Presentation type:
BG – Biogeosciences

EGU23-8898 | Orals | MAL32 | Vladimir Ivanovich Vernadsky Medal Lecture

River ecosystems: A tale of superlatives and hidden beauty 

Tom J. Battin

River ecosystems are superlatives in many respects. Their networks represent the largest biogeochemical nexus between the continents, oceans and atmosphere. River networks span multiple catchments, even biomes, and are highly dynamic in space and time. The world’s rivers contribute relatively little by areal extent, but their CO2 emissions are of the same magnitude as the CO2 sequestration flux by the world’s oceans. Rivers figure among the most heterotrophic ecosystems on Earth, metabolizing terrestrial organic carbon. Owing to their dendritic structure, the biodiversity that river networks host is exceptionally high. Finally, needless to emphasize how critical the ecosystem services are that rivers provide. Central to many of these river superlatives are microbial biofilms that abundantly coat the sedimentary surfaces of the river beds. A microbiome, encompassing all three domains of life, shapes, in conjunction with the turbulent nature of water flow, intriguing biofilm architectures. Biofilms, a hidden beauty emanating from the interactions between biology, physics and chemistry, regulate ecosystem energetics and are therefore an important linchpin between river biodiversity and biogeochemistry.

In my lecture, I will attempt to provide the state-of-the-art of global river carbon biogeochemistry and biofilm ecology. An emphasis will be given on the rivers that literally drain the roof of our planet, now at risk because of climate change. It is my hope, that soon we will appreciate the world’s river networks as we do appreciate the oceans and various terrestrial ecosystems.

How to cite: Battin, T. J.: River ecosystems: A tale of superlatives and hidden beauty, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8898, https://doi.org/10.5194/egusphere-egu23-8898, 2023.

EGU23-9859 | ECS | Orals | MAL32 | BG Division Outstanding Early Career Scientist Award Lecture

Causes and consequences of environmental perturbations through the Phanerozoic 

Hana Jurikova

Study of past carbon cycle perturbation events is fundamental for assessing Earth’s climatic and ecological sensitivities, and our planet’s overall biogeochemical functioning and responses. Major hindrance to our understanding is the lack of reliable CO2 estimates from Earth’s ‘deeper’ geologic past. I will summarize my work on CO2 reconstruction from the rock record and make the case that boron isotope values of brachiopod shells serve as a robust CO2 proxy. I will first present evidence from culturing experiments and natural marine settings demonstrating that the boron isotope composition of recent brachiopod shells responds predictably to the coupled ocean pH and CO2 system, and provide a calibration that enables its accurate quantification. Next, I will showcase ocean pH and CO2 records for some of most crucial yet enigmatic events in Earth’s evolutionary history, including the Permian-Triassic mass extinction, and discuss the causes and consequences of CO2 change and its biogeochemical impacts during extinctions and events of abrupt environmental change. Finally, I will highlight recent progress and new capabilities to lay out a roadmap towards robust record of Phanerozoic CO2.

How to cite: Jurikova, H.: Causes and consequences of environmental perturbations through the Phanerozoic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9859, https://doi.org/10.5194/egusphere-egu23-9859, 2023.

BG1 – General Biogeosciences

EGU23-412 | ECS | Orals | BG1.2

Assessing changes in post-fire vegetation resilience in Mediterranean basin over the past 22 years 

Tiago Ermitão, Célia Gouveia, Ana Bastos, and Ana Russo

Fire is an integral component of ecological dynamics, playing an important role in biome distribution and biomass variability. Nonetheless, fires can also pose a  threat to both ecosystems and humans, by imposing severe economic and social consequences, and potentially contributing to biodiversity loss, carbon loss and soil erosion, whose effects can last from months to years.

The Mediterranean basin is a fire-prone region where vegetation is in general well adapted to fire, with several species showing resistance to fire itself or being able to recover quickly following fire events. However, as a consequence of climate change, more intense and frequent summer hot and dry conditions are expected to occur, which can promote more frequent and severe wildfires, with return periods potentially outpacing recovery times. Understanding recovery dynamics is therefore crucial to assess the impact of changing fire regimes in ecological dynamics and stability of ecosystems. 

In our study, we use the “Enhanced Vegetation Index” (EVI), remotely-sensed by MODIS sensor with a temporal span of 22 years, to evaluate vegetation dynamics before, during and following large fire seasons. We use a mono-parametric recovery model to assess recovery times in different burn scars across the Mediterranean basin, covering different fire regimes and land cover types. We find a tendency for slower recovery in areas that burned more often, which may indicate a decrease in ecosystems’ resilience in the past 22 years.

This study was performed under the frameworks of the 2021 FirEUrisk project (funded by European Union’s Horizon 2020 research and innovation programme under the Grant Agreement no. 101003890) and of the PhD MIT Portugal MPP2030-FCT programme (Grant no.22405886350).

How to cite: Ermitão, T., Gouveia, C., Bastos, A., and Russo, A.: Assessing changes in post-fire vegetation resilience in Mediterranean basin over the past 22 years, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-412, https://doi.org/10.5194/egusphere-egu23-412, 2023.

EGU23-1406 | ECS | Orals | BG1.2 | Highlight

Large-scale fire events substantially impact plant-soil water relations across ecosystem types 

Martin J. Baur, Andrew D. Friend, and Adam F. A. Pellegrini

Wildfire is a global scale ecosystem phenomenon with substantial impact on the carbon cycle, climate warming, and ecosystem resilience. Fire and the hydrological cycle are strongly interlinked, with water availability determining the amount and combustibility of fuel, and fire influencing infiltration, runoff rates and evapotranspiration. Consequently, understanding soil moisture (SM) and vegetation water content (VWC) dynamics pre- and post-fire is fundamental for predicting fire occurrence, fire severity, and ecosystem recovery. Fire can modulate SM and VWC dynamics by influencing interception of rainfall, soil porosity, plant water uptake, and runoff; however, much evidence for fire effects on the hydrological cycle is obtained at the field- to watershed-scale. Therefore, we ask the following research question: What are the effects of large-scale fire events on SM and VWC dynamics across biomes globally?

Here we use over six years of global SM, VWC and vapor pressure deficit (VPD) derived from different remote sensing datasets to investigate the effects of large-scale fires on SM and VWC dynamics. We apply a dry down framework, only analyzing consecutive observations of decreasing soil moisture, to describe post-fire response rates for SM, VWC and VPD relative to a pre-fire reference state.

We find large scale evidence that the post-fire rate of change of SM over time is more negative, indicating faster water loss. Vegetation recovery, indicated by a positive change in VWC over time, exceeds the pre-fire reference state, which suggests that post-fire recovery is predominantly faster than undisturbed seasonal vegetation growth, likely due to succession of fast-growing plant species. Furthermore, fire affects ecosystem hydrology on shorter timescales as well, reducing diurnal VWC variation over a wide range of SM and VWC conditions. Our findings confirm several trends previously only observed at smaller scales and suggest global remote sensing of SM and VWC can substantially contribute to understanding the dynamics of post-fire plant and soil water status.

How to cite: Baur, M. J., Friend, A. D., and Pellegrini, A. F. A.: Large-scale fire events substantially impact plant-soil water relations across ecosystem types, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1406, https://doi.org/10.5194/egusphere-egu23-1406, 2023.

EGU23-1412 | Posters on site | BG1.2

PyroCbs from Australia Fires and its Impact Study Using Satellite Observations from CrIS and TROPOMI and Reanalysis Data 

Xiaozhen Xiong, Xu Liu, Wan Wu, Liqiao Lei, Qiguang Yang, Daniel Zhou, and Allen Laura

Australia’s unprecedented fire disasters at the end of 2019 to early 2020 emitted huge amounts of carbon monoxide (CO) and fire aerosol particles to the atmosphere, particularly during the Pyrocumulonimbus (pyroCb) outbreak that occurred in southeast Australia between 29 December 2019 and 4 January 2020. It was estimated that at least 18 pyroCbs were generated during this episode, and some of them injected ice, smoke, and biomass burning gases above the local tropopause.  An unprecedented abundance of H2O and CO in the stratosphere, and the displacement of background ozone (O3) and N2O from rapid ascent of air from the troposphere and lower stratosphere were found from satellite observations. Some other studies also found that the fire emissions and their long-range transport resulted in stratospheric aerosol, temperature, and O3 anomalies after the 2020 Australian bushfires and altered the Antarctic ozone and vortex, posing great impact to local air qality and climate change.

            This study will focus on the thermodynamic state of atmosphere associated with these pyroCbs, and its impact on the change of the cloud properties and trace gases during this unprecedented Australia fires, mainly based on a new single Field of View (SFOV) Sounder Atmospheric Products (SiFSAP) and TROPOMI. SiFSAP was developed by NASA using the Cross-track Infrared Sounder (CrIS) and Advanced Technology Microwave Sounder (ATMS) onboard SNPP and JPSS-1, and will soon be available to the public at NASA DAAC. Since this product has a spatial resolution of 15 km at nadir, which is better than most global weather and climate models and other current operational sounding products, a process-oriented analysis of the dynamic transport of CO and fire plumes during this unprecedented fire disasters will be made in this study.  Based on a Principal Component Radiative Transfer Model (PCRTM) and an optimized estimation retrieval algorithm, a simultaneously retrieval is made using the whole spectral information measured by CrIS,  and the derived SiFSAP include temperature, water vapor, trace gases (such as O3, CO2, CO, CH4 and N2O), cloud properties and surface properties. Use of ATMS together with CrIS allows SiFSAP to get accurate retrieval products under thick pyroCb conditions. An algorithm to detect pyroCb based on the hyperspectral infrared sounder spectrum from CrIS will be developed and verified. In addition to SiFSAP sounding products,  CO, O3, NO2 from TROPOMI and O3 from OMPS will be used. The wind fields from the NASA’s Modern-Era Retrospective Analysis for Research and Applications Version-2 (MERRA-2) and ERA5 will be used to characterize the transport, and the SiFSAP temperature and water vapor profiles within and around pyroCbs will be compared with MERRA-2 and ERA5 products.     

How to cite: Xiong, X., Liu, X., Wu, W., Lei, L., Yang, Q., Zhou, D., and Laura, A.: PyroCbs from Australia Fires and its Impact Study Using Satellite Observations from CrIS and TROPOMI and Reanalysis Data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1412, https://doi.org/10.5194/egusphere-egu23-1412, 2023.

EGU23-1975 | ECS | Orals | BG1.2

Drivers of spatial and temporal variability in savanna fire emission factors 

Roland Vernooij, Tom Eames, Jeremy Russel-Smith, Cameron Yates, Robin Beatty, Jay Evans, Andrew Edwards, Natasha Ribeiro, Martin wooster, Tercia Strydom, Marcos Giongo, Marco Borges, Carol Barradas, Maximo Menezes, Dave van Wees, and Guido van der Werf

Roughly half of global fire emissions originate from savannas, and emission factors (EF) are used to quantify the amount of trace gases and aerosols emitted per unit dry matter burned. It is well known that these EFs vary substantially even within a single biome but so far quantifying their dynamics has been hampered by a lack of EF measurements. Therefore, global emission inventories currently use a static averaged EF for the entire savanna biome. To increase the spatiotemporal coverage of EF measurements, we collected over 4500 EF bag measurements of CO2, CO, CH4 and N2O using an unmanned aerial system (UAS) and measured fuel parameters and fire severity proxies during 129 individual landscape fires. These measurements spanned various widespread savanna ecosystems in Africa, South America and Australia, with early and late dry season campaigns. We trained random forest (RF) regressors to estimate daily dynamic EFs for CO2, CO, CH4 and N2O at 500×500-meter resolution based on satellite and reanalysis data. The RF models reduced the difference between measured and modelled EFs by 60-85% compared to static biome averages. The introduction of EF dynamics resulted in a spatial redistribution of CO, CH4 and N2O emissions compared to the Global Fire Emissions Database version 4 (GFED4s) with higher emissions in higher rainfall savanna regions. While the impact from using dynamic EFs on the global annual emission estimates from savannas was relatively modest (+2% CO, -5% CH4 and -18% N2O), the impact on local EFs may exceed 60% under dry seasonal conditions.

How to cite: Vernooij, R., Eames, T., Russel-Smith, J., Yates, C., Beatty, R., Evans, J., Edwards, A., Ribeiro, N., wooster, M., Strydom, T., Giongo, M., Borges, M., Barradas, C., Menezes, M., van Wees, D., and van der Werf, G.: Drivers of spatial and temporal variability in savanna fire emission factors, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1975, https://doi.org/10.5194/egusphere-egu23-1975, 2023.

EGU23-2097 | Orals | BG1.2

Linked fire activity and climate whiplash in California during the early Holocene 

Jessica Oster, Julia Homann, Cameron de Wet, Sebastian Breitenbach, and Thorsten Hoffmann

Recent wildfire activity in semi-arid regions like western North America exceeds the range of historical records. High-resolution paleoclimate archives such as stalagmites could illuminate the link between hydroclimate, vegetation change, and fire activity in pre-anthropogenic climate states beyond the timescale of existing tree-ring records. Here we present an analysis of levoglucosan, a combustion-sensitive anhydrosugar, and lignin oxidation products (LOPs) in a stalagmite from White Moon Cave in the California Coast Range in order to reconstruct fire activity and vegetation composition across the 8.2 kyr event. Elevated levoglucosan concentrations suggest increased fire activity while altered LOP compositions indicate a shift toward more woody vegetation during the event, with the shift in vegetation preceding the increase in fire activity. These changes are concurrent with increased hydroclimate volatility as shown by carbon and calcium isotope proxies. Together, these records suggest that climate whiplash (oscillations between extreme wetness and aridity) and fire activity in California, both projected to increase with anthropogenic climate change, were tightly coupled during the early Holocene.

How to cite: Oster, J., Homann, J., de Wet, C., Breitenbach, S., and Hoffmann, T.: Linked fire activity and climate whiplash in California during the early Holocene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2097, https://doi.org/10.5194/egusphere-egu23-2097, 2023.

EGU23-2233 | ECS | Orals | BG1.2

Fire impacts on soil carbon in a non-fire adapted alpine forest 

Melissa Torres, Caroline Poyntner, Sampriti Chaudhuri, Marc Pignitter, Hannes Schmidt, Thilo Hofmann, and Gabriel Sigmund

An increase in fire-prone conditions in non-fire adapted regions is rooted in climatic and anthropogenic changes. Such pyrogeographical shifts are observable, for example, in alpine regions. In 2021, Austria, experienced a fire larger than 100 ha for the first time in a century in the Schneeberg-Rax mountain region. In depth understanding of post-fire effects on carbon cycling at such non-fire adapted sites is still scarce. To help close this knowledge gap, post-fire changes were investigated at the abovementioned site, including soil organic matter composition and soil chemical conditions. 

Samples were taken immediately after the fire, 3 months, 6 months and 12 months thereafter from four sampling sites. Selected sites consisted of 1. a pine forest affected by a crown fire, 2. a pine and beech mixed forest affected by a surface fire, and two non-fire affected controls with similar site conditions (vegetation, slope, altitude, and exposition). Samples were analyzed for pH, carbon content, elemental composition, leachable dissolved organic carbon and trace elements, organic matter composition, and environmentally persistent free radical concentrations. 

pH increased after the fire at both sites investigated. This increase was the strongest (up to 1.5 units) immediately after the fire but was still substantial 1 year after the fire. Carbon contents decreased approximately 2fold in the crown fire affected soil compared to the control soil, but remained similar between surface fire affected soil and the respective control. However, aromaticity of bulk carbon and the leachable fraction increased in both fire-affected soils, which can be related to the formation of pyrogenic carbon during the fire. Pyrogenic carbon is a highly aromatic and recalcitrant carbon pool produced during incomplete combustion of biomass. Pyrogenic carbon can also contain substantial amounts of environmentally persistent free radicals (EPFR), which can form reactive oxygen species, which can induce oxidative stress on microbiota. Our EPFR measurements showed an increase by at least 1.5 orders of magnitude of EPFR in fire affected soils. This study suggests that changes in soil carbon cycling can be expected following fires in non-adapted alpine forests. 

How to cite: Torres, M., Poyntner, C., Chaudhuri, S., Pignitter, M., Schmidt, H., Hofmann, T., and Sigmund, G.: Fire impacts on soil carbon in a non-fire adapted alpine forest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2233, https://doi.org/10.5194/egusphere-egu23-2233, 2023.

EGU23-2932 | Posters on site | BG1.2

Hydrological conceptual model for reconstructing fire history from cave stalagmites 

Pauline Treble, Campbell Micheline, Andy Baker, McDonough Liza, and Kosarac Nevena

Cave stalagmites (speleothems) are highly-valued archives of environmental information owing to their preservation of climate sensitive proxies and well-defined chronologies.  Yet the reconstruction of fire history from stalagmites is a relatively unexplored approach, with some advantages over traditional fire proxy archives.  For example, stalagmites may contain annual laminae (visible or chemical) which can be exploited for seasonal to annual proxy information with precise chronologies.  Thus stalagmites have the potential to yield annually-resolved records of fire and climate that could be used to (1) better understand the fire-climate relationship, (2) fire recurrence interval information, (3) understand ecosystem resilience and (4) inform land management policy.

The development of fire proxies from stalagmites is still in its infancy. Robust interpretations of any proxy information relies on an understanding of the environmental processes that lead to the preservation of proxies in the archive.  Cave stalagmites may record fire history via dripwater, or via the cave entrance as aerosols.  The focus here is on the transportable constituents in dripwater such as solutes, colloids and suspended matter.  A fire event produces ash (a source of leachates) and can alter soil properties (hydrophobicity, pH, organic matter etc) producing temporary enrichments (or depletions) in transported constituents via dripwater.  The resulting signal may be detected in stalagmites using high-resolution methods such as laser ablation mass spectrometry, fluorescence and infrared microscopy techniques.  Cave depth is an important factor in the preservation process with the detection of a fire signal more likely to be observed in dripwater from shallow caves (e.g. 5-10 m) owing to the potential for attenuation and mixing that may occur in deeper caves (Campbell et al., 2022).  However, owing to the karstification of carbonate rocks which host caves, there commonly exists different flow types: diffuse/slow flow through the matrix, preferential/fast flow through fractures and conduits.  Fracture (or conduit) influenced flowpaths have higher permeability and enhance rapid and deep percolation of water from the surface towards the cave.  Several studies have shown that stalagmites fed by dripwater with a fracture-flow component contain higher concentrations of soil-derived trace metals and organics indicating a stronger hydrological connection with the surface.  It logically follows that fracture-influenced flowpaths are more likely to transmit proxies for fire.  Furthermore, flowpaths may be a more important factor than cave depth in some settings, e.g., Campbell et al. (2022) presented a case study of a historical fire event recorded in a stalagmite that was located ~40 m below the surface.  

Understanding the hydrological setting of a cave system including rainfall recharge and flowpaths is valuable in the interpretation of speleothem records in general.  This contribution presents a conceptual model illustrating how these factors influence the preservation of fire proxies in stalagmites and makes recommendations for ideal sample selection for fire proxy records based on cave characteristics as well as stalagmite attributes such as morphology and colour.

Campbell. M. et al., Speleothems as Archives for Palaeofire Proxies. ESS Open Archive. July 24, 2022. DOI:10.1002/essoar.10511989.1

How to cite: Treble, P., Micheline, C., Baker, A., Liza, M., and Nevena, K.: Hydrological conceptual model for reconstructing fire history from cave stalagmites, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2932, https://doi.org/10.5194/egusphere-egu23-2932, 2023.

EGU23-3238 | ECS | Orals | BG1.2

Feeding the flames: how colonialism led to unprecedented wildfires across SE Australia 

Michela Mariani, Simon Connor, Michael-Shawn Fletcher, Simon Haberle, Janelle Stevenson, Peter Kershaw, Annika Herbert, Martin Theuerkauf, and David Bowman

The Black Summer bushfires (2019-2020) cost the Australian economy over 100 billion dollars and burnt a total of 18 million hectares. In just one season, around 20% of Australia's Eucalyptus forests burnt down and billions of animals perished. Recent catastrophic fires in Australia and North America have made scientists and policymakers question how the disruption of First Nations' burning practices has impacted fuel loads. For instance, we have learnt from modern Australian Indigenous communities, historical literature, and art works that Indigenous peoples have used cultural burning to rejuvenate patches of land and preserve open vegetation for hunting and cultural purposes. The advent of British invasion brought a change in the type of fire regimes and landscape management across much of the continent, which may have led to an increase in flammable fuels in forest settings. However, the actual degree of land-cover modification by early settlers has only been often debated in the academic literature and within management stakeholders.

The quantification of past land cover is needed to address such debates. Pollen is the key proxy to track past vegetation changes, but pollen spectra suffer from some important biases e.g. taphonomy, pollen productivity, dispersal capability. Estimating past vegetation cover from sedimentary pollen composition requires to correct for productivity and dispersal biases using empirical-based models of the pollen-vegetation relationship. Such models for quantitative vegetation reconstruction (e.g. REVEALS) have yet been mostly applied in the Northern Hemisphere in the last 15 years - here we present recent applications of this methodology from Australia. We show the quantification of land cover changes through pre- and post- British invasion on multiple records (n=51) across the southeastern Australian region. This represents the first regional application of REVEALS within the Australian continent.

We provide the first empirical evidence that the regional landscape before British invasion was a cultural landscape with limited tree cover as it was maintained by Indigenous Australians through cultural burning. Our findings suggest that the removal of Indigenous vegetation management has altered woodland fuel structure and that much of the region was predominantly open before colonial invasion. The post-colonial land modification has resonance in wildfire occurrence and management under the pressing challenges posed by climate change.

How to cite: Mariani, M., Connor, S., Fletcher, M.-S., Haberle, S., Stevenson, J., Kershaw, P., Herbert, A., Theuerkauf, M., and Bowman, D.: Feeding the flames: how colonialism led to unprecedented wildfires across SE Australia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3238, https://doi.org/10.5194/egusphere-egu23-3238, 2023.

EGU23-3310 | ECS | Orals | BG1.2

PEAT-FWI: Improving the Fire Weather Index for peatlands with Hydrological Modeling and L-band Microwave Observations 

Jonas Mortelmans, Anne Felsberg, Gabriëlle De Lannoy, Sander Veraverbeke, Robert Field, Niels Andela, and Michel Bechtold

The Fire Weather Index (FWI) is used worldwide to estimate the danger of wildfires. The FWI system integrates meteorological parameters and empirically combines them into several moisture codes, each representing a different fuel type. These moisture codes are then used in combination with wind speed to estimate a fire danger. Originally, the FWI system was developed for a standard jack pine forest, however, it is widely used by fire managers to assess the fire danger in different environments as well. Furthermore, it is often also used to assess the vulnerability of organic soils, such as peatlands, to ignition and depth of burn. The utility of which is often questioned.

 

This research aims at improving the original FWI for northern peatlands by replacing parts of the original, purely weather-based FWI system with satellite-informed model estimates of peat moisture and water level. These come from a data assimilation output combining the NASA catchment model, including the peat modules PEATCLSM, and Soil Moisture and Ocean Salinity (SMOS) L-band brightness temperature observations. The predictive power of the new, peat-specific FWI (PEAT-FWI) is evaluated against the original FWI against fire data of the global fire atlas from 2010 through 2018 over the major northern peatlands areas. For the evaluation, the fires are split up in early and late season fires, as it is hypothesized that late fires are more hydrological driven, and the predictive power of the PEAT-FWI will thus differ between the two types of fires. Our results indeed indicate that the PEAT-FWI improves the predictive capability of estimating fire risk over northern peatlands in particular for late fires. By using a receiver operating characteristics (ROC) curve to evaluate the predictive power of the FWI against a random estimate, the area under the curve increases by up to 10% for the PEAT-FWI compared to the original FWI. The recent version 7 release of the operational Soil Moisture Active Passive (SMAP) Level-4 Soil Moisture Data Assimilation Product now includes PEATCLSM, thus, the proposed PEAT-FWI is straightforward to include in operational FWI products.

How to cite: Mortelmans, J., Felsberg, A., De Lannoy, G., Veraverbeke, S., Field, R., Andela, N., and Bechtold, M.: PEAT-FWI: Improving the Fire Weather Index for peatlands with Hydrological Modeling and L-band Microwave Observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3310, https://doi.org/10.5194/egusphere-egu23-3310, 2023.

EGU23-3332 | ECS | Orals | BG1.2

How changes in ignition sources influence fire probability in the Amazon and Cerrado biomes: a perspective based on frontier age 

Andreia F. S. Ribeiro, Lucas Santos, Maria R. Uribe, Rafaella A. Silvestrini, Ludmila Rattis, Marcia N. Macedo, Douglas C. Morton, James T. Randerson, Sonia I. Seneviratne, Jakob Zscheischler, and Paulo M. Brando

Agricultural expansion and ongoing climate change are rapidly altering the fire regime of natural ecosystems along the Cerrado-Amazon biome boundary. While agricultural intensification has driven a decrease in fire ignitions in some regions, agricultural expansion has increased fire usage in other landscapes for deforestation and managing pasturelands. These contrasting patterns of fire activity across different land-use frontiers limits our ability to accurately predict where and when fires may occur, particularly under the context of climate change.

To predict fire activity with land-use transitions, we modelled fire probability as a function of the age of different land-use transitions across the Amazon and Cerrado. We investigated annual land-use and associated burned areas based on the MapBiomas Collection 6.0 and MapBiomas Fire Collection 1.0 data, respectively, from 1986 to 2020. This allowed us to quantify how the time-since conversion of native vegetation (forest, savanna, and grassland) to pasture and farming influence fire occurrence. Additionally, we explored the joint impact of land-use change and climate extremes in fire activity in terms of estimated vapor pressure deficit (VPD) and maximum cumulative water deficit (MCWD), two common measures of flammability and drought impact. 

Our results confirm that transition age is a strong predictor of fire probability. They also suggest that fire probability increases (decreases) at different rates before (after) clearing in Amazon and Cerrado. The role of climate extremes in modulating burning activity associated with land-use transitions varied by biome, post-fire land use, and the size of the burned area associated with the conversion. These findings provide insight into incorporating the effect of land-use transition age on ignition probability for fire modelling in combination with climate drivers. From an operational point of view, our results aim to contribute to environmental policies capable of sustaining ecosystem integrity at the ecotone between the Amazon and Cerrado biomes.

How to cite: Ribeiro, A. F. S., Santos, L., Uribe, M. R., Silvestrini, R. A., Rattis, L., Macedo, M. N., Morton, D. C., Randerson, J. T., Seneviratne, S. I., Zscheischler, J., and Brando, P. M.: How changes in ignition sources influence fire probability in the Amazon and Cerrado biomes: a perspective based on frontier age, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3332, https://doi.org/10.5194/egusphere-egu23-3332, 2023.

EGU23-3632 | ECS | Posters virtual | BG1.2

BPCA-derived PyC may reflect fire signals over regional scales from the western Amazon Basin fire record 

Jing Lyu, Andrew Zimmerman, Mark Bush, and Crystal McMichael

Fire alters the biogeochemical cycling of important elements, plays a role in climate change, and shapes the composition of global biological communities. Detection of past fires has long been used to reconstruct human settlement and climate records. Charcoal and phytolith abundance has been the most commonly used paleofire proxies but may only represent evidence of local fires. Chemical analyses of pyrogenic carbon (PyC) have been more recently used, but are also not without controversy. Thus far, very few intercomparisons of these proxies have been conducted. Here, the fire records contained in soil and lake sediments of Western Amazon (at lakes Ayauchi, Parker, Gentry, and surrounding regions) were determined by charcoal microscopy, chemical thermal oxidation (CTO), and benzene polycarboxylic acids (BPCA) molecular biomarkers. Charcoal represented a smaller portion of PyC and, with its patchy distribution, likely indicated local or larger regional fire events. With a median value of about 15% of organic carbon, PyC via CTO oxidation was of the highest concentrations, which suggests a larger PyC detection window and lower sensitivity of reflecting regional fire. With a median value of about 3% of organic carbon, the BPCA-derived PyC distributions bore the closest resemblance to both spatial and temporal regional fire variations, established via archeological, pollen and phytolith records, thus may be a more sensitive indicator of fire over larger regional scales. Molecular ratios of BPCA molecules in Lake Ayauchi soils indicated higher temperature fires (> 600°C) and suggested a history of more human occupation and human-caused fire in the Lake Ayauchi region compared with the Lake Gentry & Parker region. However, our findings suggest that the use of a combination of fire proxy methods provides a fuller picture of the fire history of a region than any single approach. Establishing a better understanding the differences in the information provided by various paleofire proxies will allow a more complete understanding of the drivers, history and ecological and biogeochemical effects of fire, both regionally and globally.

How to cite: Lyu, J., Zimmerman, A., Bush, M., and McMichael, C.: BPCA-derived PyC may reflect fire signals over regional scales from the western Amazon Basin fire record, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3632, https://doi.org/10.5194/egusphere-egu23-3632, 2023.

EGU23-3695 | ECS | Orals | BG1.2

Wildfires alter nitrifier communities and increase soil emissions of NOx but not N2O in California chaparral 

Elizah Stephens, Aral Greene, Alexander Krichels, and Peter Homyak

Background:

Fires burn roughly 3% of Earth’s land surface each year and are predicted to become more frequent and severe as human-caused climate change progresses. Fires can drive ecosystem N loss by volatilizing N bound in plant biomass to the atmosphere and by leaving behind ash rich in ammonium (NH4+) and organic N that can run off when it rains. While N volatilization and runoff account for a large fraction of N loss after fires, budget imbalances suggest soil emissions of nitric oxide (NO) and nitrous oxide (N2O) may also be significant N loss pathways after fire. Identifying sources of NO and N2O is important because NO is a precursor for tropospheric O3 which causes high rates of asthma hospitalizations,and N2O is a powerful greenhouse gas with 300× the warming potential of CO2. Soil emissions of NO and N2O are largely governed by the microbial processes of nitrification and denitrification. Under aerobic conditions typical of dry soils, nitrifying organisms such as ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) oxidize NH4+ to nitrate (NO3-) and release NO and N2O as byproducts. AOA and AOB process N with different efficiencies, suggesting shifts in AOA:AOB ratios may change N emissions. Specifically, AOB are dominant in soils with high NH4+and pH and produce higher NO and N2O emissions. Since such soil conditions are frequently observed after fires, we hypothesize NO and N2O emissions will increase as AOB communities become dominant. To test this, we collected soil cores from 5 plots in the Sequoia National Park, CA over a time series starting two weeks after a high severity chaparral fire. We selectively inhibited AOA and AOB communities to measure their contributions to NO and N2O emissions. We also measured the isotopic composition of N2O emissions from these soils using an LGR isotopic N2O analyzer to better understand the processes responsible for post-fire N2O production.

Results/Conclusions

One month after the fire, soil bulk emissions of NO over 72hrs were 1.5 times higher in the burned plots (101.4 ± 22.4 µg N-NO/g soil burned; 67.1 ± 19.3 µg N-NO/g soil unburned; ±SE). Bulk soil emissions of N2O over 72hrs were 7.5 times lower in burned plots compared to before the fire (0.0616 ± 0.04 ng N-N2O/g soil burned; 0.463 ± 0.19 ng N-N2O/g soil unburned; ±SE). Although the effects of fire on nitrifier communities were not significant at one month post-fire (Control: p=0.14, AOA: p=0.09, AOB: p=0.162), both AOA and AOB contributions to NO emissions increased in response to fire. Results for nitrifier contributions to N2O emissions were highly variable and non-significant with no clear trends as all N2O emissions were near zero. Further analysis over the time series may yield clearer results as microbial communities have more time to recover. Pairing these data with isotopic information (in progress) may yield one of the most in-depth understandings of post-fire NO and N2O emissions to date.

How to cite: Stephens, E., Greene, A., Krichels, A., and Homyak, P.: Wildfires alter nitrifier communities and increase soil emissions of NOx but not N2O in California chaparral, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3695, https://doi.org/10.5194/egusphere-egu23-3695, 2023.

EGU23-4520 | ECS | Orals | BG1.2

Examining the response of different wildfire properties to changes in climate and CO2 levels at the Last Glacial Maximum 

Olivia Haas, Iain Colin Prentice, and Sandy P. Harrison

Climate change and atmospheric CO2 levels can influence wildfire properties through separate and potentially contrasting impacts on vegetation and climate. One way to examine the sensitivity of global wildfire properties to changes in climate and CO2 levels is using an out-of-sample experiment, such as the Last Glacial Maximum (LGM; 21 ka BP). Charcoal records show reduced burning at the LGM, when CO2 levels were ~ 185 ppm and the climate was cooler and drier. In this analysis, we isolated out the potential effects of LGM CO2 levels and LGM climate on the spatial patterns of global wildfire properties.

Using three statistical models, we conducted simulations of the spatial distribution of global burnt area, fire size and fire intensity under four scenarios: modern climate/modern CO2 levels, LGM climate/LGM CO2 levels, modern climate/LGM CO2 levels and LGM/ modern CO2 levels. We used outputs from three coupled ocean–atmosphere models representative of the range of simulated LGM climates. The ecophysiological effect of CO2 levels was explicitly accounted for through vegetation inputs. Gross primary productivity (GPP) and land cover were derived for the LGM and modern climate keeping either CO2 levels at 395 ppm (modern), or setting them to 185 ppm, using the P Model, a first-principles model of GPP which allows continuous acclimation of photosynthetic parameters to environmental variations, and the BIOME4 equilibrium global vegetation model.

Our results show a reduction in burnt area under LGM CO2 levels, both with modern and LGM climate inputs. In the case of the warmest of the LGM climate scenarios, this reduction was of the same magnitude as the combined LGM climate/LGM CO2 levels scenario. However, the driest and coldest LGM climate scenario produced a reduction in burnt area even with modern CO2 levels, and the largest reduction in burnt area with LGM CO2.  The reduction was primarily driven by changes in vapour pressure deficit (VPD). Fire size increased under LGM climates, due to changes in wind and VPD. The lower CO2 values at the LGM had no impact on fire size. Fire intensity increased under LGM climates and LGM CO2 levels, with both effects of similar amplitude and changes driven primarily by VPD, GPP and diurnal temperature range. 

We compared our outputs with sedimentary charcoal records from the Reading Palaeofire Database (RPD). Overall, the burnt area LGM CO2 levels/LGM climate scenario showed the greatest agreement, though depending on how cold and dry the LGM climate was, this agreement was either equal to LGM CO2 levels or LGM climate alone. These results suggest that whilst there was reduced global burning at the LGM, there may have been larger and more intense fires. They also highlight the importance of the ecophysiological effect of CO2 levels on fuels, a major control of burnt area and fire intensity regardless of climate. They point to the importance of including this effect in process-based fire models, as well as the importance of accurately estimating the amplitude of projected change for different climate variables in order to increase the reliability of future projections.

How to cite: Haas, O., Prentice, I. C., and Harrison, S. P.: Examining the response of different wildfire properties to changes in climate and CO2 levels at the Last Glacial Maximum, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4520, https://doi.org/10.5194/egusphere-egu23-4520, 2023.

EGU23-5113 | ECS | Orals | BG1.2

Speleothem organic biomarkers trace last millennium fire history at near-annual resolution in northwestern Australia 

Elena Argiriadis, Rhawn F. Denniston, Stefania Ondei, and David Bowman

Recent developments in speleothem science are showing their potential for paleofire reconstruction through a variety of inorganic and organic proxies including trace metals (1) and the pyrogenic organic compound levoglucosan (2). Previous work by Argiriadis et al. (2019) presented a method for the analysis of trace polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in stalagmites (3). These compounds reflect biogeochemical processes occurring at the land surface, in the soil, and in the cave. PAHs are primarily related to combustion of biomass while n-alkanes, with their potential for vegetation reconstruction (4), provide information on fuel availability and composition, as well as fire activity. These organic molecules are carried downward by infiltrating water and incorporated into speleothems (5), thereby creating the potential to serve as novel paleofire archives.

Using this approach, we developed a high-resolution stalagmite record of paleofire activity from cave KNI-51 in tropical northwestern Australia. This site is well suited for high resolution paleofire reconstruction as bushfire activity in this tropical savanna is some of the highest on the continent, the cave is shallow and overlain by extremely thin soils, and the stalagmites are fast-growing (1-2 mm yr-1) and precisely dated. We analyzed three stalagmites which grew continuously in different time intervals through the last millennium - KNI-51-F (CE ~1100-1620), KNI-51-G (CE ~1320-1640), and KNI-51-11 (CE ~1750-2009). Samples were drilled continuously at 1-3 mm resolution from stalagmite slabs, processed in a stainless-steel cleanroom to prevent contamination.

Despite a difference in resolution between stalagmites KNI-51-F and -G, peaks in the target compounds show good replication in the overlapping time interval of the two stalagmites, and PAH abundances in a portion of stalagmite KNI-51-11 that grew from CE 2000-2009 are well correlated with satellite-mapped fires occurring proximally to the cave.

Our results suggest an increase in the frequency of low intensity fire in the 20th century relative to much of the previous millennium. The timing of this shift is broadly coincident with the arrival of European pastoralists in the late 19th century and the subsequent displacement of Aboriginal peoples from the land. Aboriginal peoples had previously utilized “fire stick farming”, a method of prescribed, low intensity burning, that was an important influence of ecology, biomass, and fire.  Prior to the late 1800s, the period with the most frequent low intensity fire activity was the 13th century, the wettest interval of the entire record. Peak high intensity fire activity occurred during the 12th century.

Controlled burn and irrigation experiments capable of examining the transmission of pyrogenic compounds from the land surface to cave dripwater represent the next step in this analysis. Given that karst is present in many fire-prone environments, and that stalagmites can be precisely dated and grow continuously for millennia, the potential utility of a stalagmite-based paleofire proxy is high.

 

 

(1) L.K. McDonough et al., Geochim. Cosmochim. Acta. 325, 258–277 (2022).

(2) J. Homann et al., Nat. Commun., 13:7175 (2022).

(3) E. Argiriadis et al., Anal. Chem. 91, 7007–7011 (2019).

(4) R.T. Bush, F. A. McInerney, Geochim. Cosmochim. Acta. 117, 161–179 (2013).

(5) Y. Sun et al., Chemosphere. 230, 616–627 (2019).

How to cite: Argiriadis, E., Denniston, R. F., Ondei, S., and Bowman, D.: Speleothem organic biomarkers trace last millennium fire history at near-annual resolution in northwestern Australia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5113, https://doi.org/10.5194/egusphere-egu23-5113, 2023.

EGU23-5429 | ECS | Posters on site | BG1.2

Smoke self-lofting towards the lower stratosphere: an alternative process to pyroCb-lofting 

Kevin Ohneiser, Albert Ansmann, Jonas Witthuhn, Hartwig Deneke, Alexandra Chudnovsky, Gregor Walter, and Fabian Senf

Wildfire smoke is known as a highly absorptive aerosol type in the shortwave wavelength range. The absorption of Sun light by optically thick smoke layers results in heating of the ambient air. This heating is translated into self-lofting of the smoke up to more than 1 km in altitude per day. The main goal is to demonstrate that radiative heating of intense smoke plumes is capable of lofting them from the lower and middle free troposphere (injection heights) up to the tropopause without the need of pyrocumulonimbus (pyroCb) convection. The further subsequent ascent within the lower stratosphere (caused by self-lofting) is already well documented in the literature. Simulations of heating rates which are then converted into lofting rates are conducted by using the ECRAD (European Centre for Medium-Range Weather Forecasts Radiation) scheme. As input parameters thermodynamic profiles from CAMS (Copernicus Atmosphere Monitoring Service) reanalysis data, aerosol profiles from ground-based lidar observations, radiosonde potential temperature profiles, CALIOP (Cloud Aerosol Lidar with Orthogonal Polarization) aerosol measurements, and MODIS (Moderate Resolution Imaging Spectroradiometer) aerosol optical depth retrievals were used. 


The sensitivity analysis revealed that the lofting rate strongly depends on aerosol optical thickness (AOT), layer thickness, layer height, and black carbon (BC) fraction. We also looked at the influence of different meteorological parameters such as cloudiness, relative humidity, and potential temperature gradient. Lofting processes in the stratosphere observed with CALIOP after major pyroCb events (Canadian fires, 2017, Australian fires 2019-2020) are compared with simulations to demonstrate the applicability of our self-lofting model. We analyzed long-term CALIOP observations of Siberian smoke layers and plumes evolving in the troposphere and UTLS (upper troposphere and lower stratosphere) region over Siberia and the adjacent Arctic during the summer season of 2019 and found several indications (fingerprints) that self-lofting contributed to the vertical transport of smoke. We hypothesize that the formation of a near-tropopause aerosol layer, observed with CALIOP over several months, was the result of self-lofting processes because this is in line with the self-lofting simulations. 


We will show a detailed analysis of tropospheric and stratospheric smoke lofting rates based on simulations and observations.

How to cite: Ohneiser, K., Ansmann, A., Witthuhn, J., Deneke, H., Chudnovsky, A., Walter, G., and Senf, F.: Smoke self-lofting towards the lower stratosphere: an alternative process to pyroCb-lofting, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5429, https://doi.org/10.5194/egusphere-egu23-5429, 2023.

EGU23-5803 | ECS | Orals | BG1.2 | Highlight

Which is the role of post-fire SOC erosion in the C cycle? 

Antonio Girona-García, Cristina Santín, Diana Vieira, and Stefan Doerr

Wildfires burn on average 448 million hectares globally every year, releasing around 2.2 Pg of carbon (C) into the atmosphere [1, 2]. The net effect of wildfires in the C cycle goes, however, beyond emissions and involves many other interacting processes. Among those, there is a significant knowledge gap on the role of post-fire soil organic carbon (SOC) erosion as a carbon sink mechanism.

Post-fire erosive response is greatly enhanced by the direct and indirect effects of wildfires on soil and vegetation, such as the loss of protective cover and soil structure or the development of a water-repellent layer [3]. In addition, biomass and soil organic matter undergo quantitative and qualitative changes during wildfires, such as the formation of pyrogenic carbon, highly resistant to degradation. The resulting PyC and non-PyC carbon fractions, with contrasting physical properties and chemical stability, will be differently redistributed and mineralized during the erosion process [4]. Ultimately, post-fire SOC erosion will act as a carbon sink when the post-fire burial and stabilization of eroded carbon, together with the recovery of net primary production and soil organic carbon content, exceed the SOC losses during its post-fire transport [5]. All these processes have been scarcely investigated and poorly quantified to the date. In this presentation, we will provide new insights into this potential C sink mechanism, critically reviewing the state of the art and highlighting key research gaps.

References

[1] Boschetti et al., 2021. Global Wildfire Information System (GWIS). https://gwis.jrc.ec.europa.eu/apps/country.profile/downloads

[2] Randerson et al., 2012. J Geophys Res. https://doi.org/10.1029/2012JG002128

[3] Shakesby & Doerr, 2006. Earth-Sci Revs. https://doi.org/10.1016/j.earscirev.2005.10.006

[4] Doetterl et al., 2016. Earth-Sci Revs. https://doi.org/10.1016/j.earscirev.2015.12.005

[5] Santín et al., 2015. Glob Change Biol. https://doi.org/10.1111/gcb.12800

How to cite: Girona-García, A., Santín, C., Vieira, D., and Doerr, S.: Which is the role of post-fire SOC erosion in the C cycle?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5803, https://doi.org/10.5194/egusphere-egu23-5803, 2023.

EGU23-6083 | ECS | Posters on site | BG1.2

Representing Northern High Latitude Peat Fires in the JULES-INFERNO Fire Model 

Katie Blackford, Apostolos Voulgarakis, Colin Prentice, Chantelle Burton, and Matthew Kasoar

Anthropogenic activities and climate change are increasing the vulnerability of carbon rich peatlands to wildfires. Peat fires, which are dominated by smouldering combustion, are some of the largest and most persistent wildfires on Earth. Across the northern high latitudes, peat fires have the potential to release vast amounts of long term stored carbon and other greenhouse gases and aerosols. Consequently, peat fires can have huge implications on the carbon cycle and result in a positive feedback effect on the climate system. Peat fires also impact air quality and can lead to haze events, with major impacts on human health. Despite the importance of peat fires they are currently not represented in most fire models, leading to large underestimations of burnt area and carbon emissions in the high latitudes. Here, I present a representation of peat fires in the JULES-INFERNO fire model (INFERNO-peat). INFERNO-peat improves the representation of burnt area across the high latitudes, with notable areas of improvement in Canada and Siberia. INFERNO-peat also highlights a large amount of interannual variability in carbon emissions from peat fires. The inclusion of peat fires into JULES-INFERNO demonstrates the importance of representing peat fires in models, and not doing so may heavily restrict our ability to model present and future fires and their impacts across the northern high latitudes.

How to cite: Blackford, K., Voulgarakis, A., Prentice, C., Burton, C., and Kasoar, M.: Representing Northern High Latitude Peat Fires in the JULES-INFERNO Fire Model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6083, https://doi.org/10.5194/egusphere-egu23-6083, 2023.

EGU23-6184 | ECS | Orals | BG1.2 | Highlight

A global model for estimating fuel consumption and fire carbon emissions at 500-m spatial resolution 

Dave van Wees, Guido R. van der Werf, James T. Randerson, Brendan M. Rogers, Yang Chen, Sander Veraverbeke, Louis Giglio, and Douglas C. Morton

Fires constitute a key source of emissions of greenhouse gasses and aerosols. Fire emissions can be quantified using models, and these estimates are influenced by the spatial resolution of the model and its input data. Here we present a novel global model based on the Global Fire Emissions Database (GFED) modelling framework for the estimation of fuel consumption and fire carbon emissions at a spatial resolution of 500 m. The model was primarily based on observation-derived data products from MODIS, reanalysis data for meteorology, and an updated field measurement synthesis database for constraining fuel load and fuel consumption. Compared to coarser models, typically with a resolution of 0.25°, the 500-m spatial resolution allowed for increased spatially resolved emissions and a better representation of local-scale variability in fire types. The model includes a separate module for the calculation of emissions from fire-related forest loss, using 30-m Landsat-based forest loss data. We estimated annual carbon emissions of 2.1 Pg C yr-1, of which around 24% was from fire-related forest loss. Fuel consumption was on average a factor 10 higher in case of fire-related forest loss compared to fires without forest loss. Up to now, emission estimates from our new model are based on MODIS burned area with a 500-m resolution, leading to global emissions similar to GFED4s. However, novel high-resolution burned area datasets based on the Landsat and Sentinel-2 missions reveal substantially more global burned area. Our 500-m global fire model provides a suitable framework for converting these burned area products to emissions, with the prospect of substantially higher global emissions.

How to cite: van Wees, D., van der Werf, G. R., Randerson, J. T., Rogers, B. M., Chen, Y., Veraverbeke, S., Giglio, L., and Morton, D. C.: A global model for estimating fuel consumption and fire carbon emissions at 500-m spatial resolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6184, https://doi.org/10.5194/egusphere-egu23-6184, 2023.

EGU23-6286 | ECS | Posters on site | BG1.2

Hysteresis of fire-prone weather to CO2 forcing 

Jin-Soo Kim, Hyo-Jeong Kim, and Soon-Il An

CO2 emission from biomass burning (BB) is one of the essential elements of the global carbon budget, with its annual mean of about 2.0 PgC/year equivalent to 15 % of 2020 fossil fuel emissions. However, while a global increase in fire-prone weather is projected alongside climate change, a quantitative understanding of how much carbon will further be released due to increased fires is highly limited, which could result in large uncertainty in meeting the net zero target. Thus, in this study, we evaluate future changes in fire-prone weather based on the fire weather index (FWI) and estimate the potential fire-induced emissions on a global scale that could be induced by climate change. To this end, 28 ensembles of idealized CO2 reduction simulations with the CESM climate model were analyzed. The results show that when CO2 in the atmosphere is doubled (2xCO2) from 367 ppm by 1 % per year, the additional emission due to increased fire weather could reach about 1.7 PgC/year, which corresponds to 82% of the current BB emission. Moreover, even if the atmospheric CO2 concentration further peaks and is reduced back to 2xCO2, the lagged response of the climate system can cause fire-prone weather and its resulting C emissions to remain higher than its previous state in many countries. These results highlight that more focus is required on the climate-fire-carbon feedback not only for more accurate future predictions but also for achieving net zero emissions in each country through a proper wildfire management strategy.

How to cite: Kim, J.-S., Kim, H.-J., and An, S.-I.: Hysteresis of fire-prone weather to CO2 forcing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6286, https://doi.org/10.5194/egusphere-egu23-6286, 2023.

EGU23-6777 | ECS | Posters on site | BG1.2

Characterisation of large-scale urban fire emissions by inverse modelling 

Emilie Launay, Virginie Hergault, Marc Bocquet, Joffrey Dumont Le Brazidec, and Yelva Roustan

Large-scale fires such as warehouse fires that have occurred in recent years or dramatic accidents like the Paris Notre-Dame Cathedral fire in 2019 have stressed the need to develop means of assessing the toxicity risks to the population and the environment of smoke plumes. A key challenge is to quickly provide the authorities with information on the areas impacted by the plume and the pollutant concentration levels to which the population is likely to be or to have been exposed. The Laboratoire Central de la Préfecture de Police (LCPP) aims to deploy a number of devices for measuring pollutants and tracers of smoke combustion during a fire. Subsequently, the application of an atmospheric dispersion model within the framework of a data assimilation approach should provide a source characterisation and a finer estimate of the concentration levels at points of interest.

To characterise the source, noticeably the released mass of pollutants and the emission height linked to a plume rise, an inverse problem method has been implemented. It is based on a Bayesian Markov Chain Monte Carlo (MCMC) technique meant to quantify the uncertainties associated with the emission estimation. Since the emission height strongly influences the atmospheric dispersion in the vicinity of the source, two approaches are used to estimate it. The first one consists in finding the emission time rate for each considered height and the second one consists in focussing on a single emission height and its associated emission time rate using a discrete distribution to describe the vertical profile. We use the Lagrangian Parallel Micro Swift Spray (PMSS) model developed by AriaTechnologies fed with meteorological fields provided by Météo-France to represent the atmospheric dispersion of smoke.

Our inverse method is applied to a large warehouse fire that occurred in Aubervilliers near Paris in 2021 using real observations. Abnormal concentrations of particulate matter were recorded, with a peak at 160 µg.m-3, located in the centre of Paris about 6 km from the source. They were collected by the LCPP and AirParif, the local air quality agency, and are used to retrieve the emission with a quantification of uncertainties and a sensitivity analysis of model error. The resulting emission height of the source, mainly between 200 and 300 m, coincides with the terrain observation for an emission rate of less than 1000 kg/h throughout the duration of the fire. A sensitivity analysis to the initial approximation of the source (the prior) shows its importance. It suggests to improve our method by incorporating the statistical parameters of the observation error into the MCMC method.

How to cite: Launay, E., Hergault, V., Bocquet, M., Dumont Le Brazidec, J., and Roustan, Y.: Characterisation of large-scale urban fire emissions by inverse modelling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6777, https://doi.org/10.5194/egusphere-egu23-6777, 2023.

EGU23-6797 | ECS | Posters on site | BG1.2

Variability of CO and aerosols plumes from wildfires in the Northern Hemisphere in 2008-2022 using satellite observations. 

Antoine Ehret, Solène Turquety, Maya George, and Cathy Clerbaux

Wildfires are responsible for significant emissions of greenhouse gases, pollutants and aerosols. In addition to being a large source of carbon monoxide (CO) and carbon dioxide (CO2), they alone account for more than half of black carbon emissions and the majority of primary organic aerosol emissions.

Despite proactive fire suppression policies in the Northern Hemisphere (NH), allowing a decrease in fires, especially in Europe, an increase in the number of extreme fires can be noted in recent years. In the NH, this increase is mainly in Western America and boreal regions. The pollution plumes produced during extreme fires can be transported over thousands of kilometers, impacting background pollutant levels on a hemispheric scale. Thus, variability in fire intensity may explain a large part of the spatial and temporal variability of many atmospheric pollutants. For longer lived pollutants, wildfires may significantly increase background levels.

In this study, the link between extreme fire weather (high temperature), large fires and background pollution in the Northern Hemisphere is analyzed based on satellite observations. The impact of large wildfires on background levels of CO and aerosols above Europe is studied more specifically. We present the variability of fire frequency in the NH, their intensity and the related emissions using 20 years (2003-2022) of MODIS fire observations analyzed with the APIFLAME model. The link between large events and fire weather is studied using the ERA5 reanalyses and the Canadian Fire Weather Index (FWI). The related impact on the variability of total CO and AOD in the NH is analyzed using 15 years (2008-2022) of satellite observations from IASI/Metop and MODIS/Terra and Aqua, respectively. Finally, plume retro trajectories are computed in order to assess the contribution of the different geographical areas of the NH on the CO and AOD variability.

How to cite: Ehret, A., Turquety, S., George, M., and Clerbaux, C.: Variability of CO and aerosols plumes from wildfires in the Northern Hemisphere in 2008-2022 using satellite observations., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6797, https://doi.org/10.5194/egusphere-egu23-6797, 2023.

EGU23-7379 | Orals | BG1.2 | Highlight

Changes in global fire regimes under idealized overshoot scenarios 

Lars Nieradzik, Hanna Lee, Paul Miller, Jörg Schwinger, and David Wårlind

Within the framework of the project IMPOSE (Emit now, mitigate later? IMPlications of temperature OverShoots for the Earth system) six idealized emission-overshoot simulations have been performed with the Earth System Model NorESM2-LM2 and used as forcing for the 2nd generation dynamic global vegetation model LPJ-GUESS with its fire-model SIMFIRE-BLAZE to investigate the impact of different CO2 overshoots on global wildfire regimes.

The simulations describe a set of scenarios with high, medium, and low accumulative CO2 emissions and each of which has a short (immediate) and a long (100 years) peak of accumulative CO2 emissions before declining towards a baseline simulation of 1500 PgC accumulatively emitted within the first 100 years.

The results show that the height of the overshoot has an impact on global fire regimes while its duration does not seem to play a significant role 200 years after peak CO2. Overall, we can see that changes in vegetation composition following the temperature anomaly are the main driver for changes in global wildfire frequency. While in the low overshoot scenarios burnt area has almost converged towards the baseline simulation, the extremest scenarios show the lowest burnt area at the end of the simulation period, indicating that vegetation changes, especially in low latitudes, have been most significant and/or are still ongoing.

How to cite: Nieradzik, L., Lee, H., Miller, P., Schwinger, J., and Wårlind, D.: Changes in global fire regimes under idealized overshoot scenarios, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7379, https://doi.org/10.5194/egusphere-egu23-7379, 2023.

EGU23-7449 | ECS | Orals | BG1.2

The role of vegetation in UK upland wildfires: Risk, Resilience, and Remote Sensing 

Kirsten Lees and Tim Lenton

Wildfires are becoming a growing concern in the UK, as climate change increases the occurrence and persistence of periods of hot, dry weather. Vegetation type and management play an important but contested role in UK fire risk and resilience, and questions remain over the best ways to prevent large fires developing. Remote sensing can provide vital data on fire size, severity, and recovery times, but method effectiveness is dependent on understanding specific ecosystems. This research uses ground validation of four wildfires in the UK Peak District National Park to deliver insights which improve interpretation of satellite data in wildfire monitoring. These insights are then applied to a three-year remote sensing database of large wildfires in England and Wales, to give novel results on the links between vegetation type and management, and fire size and severity. Ecosystem resilience and recovery is further explored through analysing the vegetation growth post-fire at three of the four Peak District study sites. This project therefore develops and validates remote sensing methodology in wildfire research by combining field data with satellite imagery to yield new understandings of the relationships between vegetation and fire. 

How to cite: Lees, K. and Lenton, T.: The role of vegetation in UK upland wildfires: Risk, Resilience, and Remote Sensing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7449, https://doi.org/10.5194/egusphere-egu23-7449, 2023.

EGU23-7853 | Posters on site | BG1.2

Current Operational Implementation of the Canadian Forest Fire Weather Index System in the Republic of Ireland 

Klara Finkele, Padraig Flattery, Ciaran Nugent, and Paul Downes

Since 2006 the Canadian Forest Fire Weather Index System (FWI) has been employed operationally at Met Éireann to predict the risk of forest fires in Ireland (Walsh, S, 2006). Around 11% or 770,000 ha of the total land area of Ireland is afforested, but there are also large areas of open mountain and peatlands covered in grasses, dwarf-shrub and larger woody shrub type vegetation which can provide fuel for spring wildfires under suitable conditions. Following winter, vegetation can be dead or have a very low live moisture content, and the flammability of this vegetation can be readily influenced by prevailing weather, especially following prolonged dry periods.

The Department of Agriculture, Food and Marine is the Forest Protection authority in Ireland responsible for issuing Fire Danger Notices. These notices improve preparedness for fire responses and are based on information provided by Met Éireann who calculate the FWI and FWI components using observation data at synoptic stations, and the predicted FWI for the next five days ahead based on numerical weather prediction data.

The FWI is determined based on the types of forest fuel and how quickly they dry out/get rewetted, and components of fire behaviour. The FWI represents the fire intensity as the rate of energy per unit length of fire front (kW/m). The components which provide the most accurate indication of risk under Irish conditions are the Fine Fuel Moisture Code and Initial Spread Index, based on the fuels involved and ignition patterns observed to date. Since 2022 Met Eireann provide the FWI as well as the individual components Fine Fuel Moisture Content and Initial Spread Index via the public website for synoptic stations. These indices are based on observations and a seven-day forecast into the future using ECMWF predictions. This allows all county councils responsible for wildfire preparedness to access this information swiftly and directly.

Met Éireann also use the ANYWHERE multi-hazard warning tool which allows for visualisation of multiple fire-related risk factors and warning indices to be viewed simultaneously. The ANYWHERE system, in combination with our station-based forecast and antecedent conditions, provide fire managers and response teams with excellent information with which to make decisions. 

How to cite: Finkele, K., Flattery, P., Nugent, C., and Downes, P.: Current Operational Implementation of the Canadian Forest Fire Weather Index System in the Republic of Ireland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7853, https://doi.org/10.5194/egusphere-egu23-7853, 2023.

EGU23-7913 | ECS | Posters on site | BG1.2

Fate of Fire altered Organic Carbon in the arctic river-to-ocean continuum: Resolving Mackenzie River Black Carbon in the Beaufort Sea 

Linn G. Speidel, Lisa Bröder, Julie Lattaud, Negar Haghipour, Timothy I. Eglinton, and Alysha I. Coppola

Keywords: Black carbon, Dissolved organic carbon, BPCAs, Mackenzie River, Beaufort Sea, Climate change

Climate change is amplified in the arctic and boreal regions. This causes higher average temperatures and less precipitation in the summer months and is resulting in longer wildfire seasons, severity, frequency and extent. This increases the relies of carbon into the atmosphere as greenhouse gases and aerosols, amplifying climate change even further. Black carbon (BC) is a fraction of organic carbon, resulting from the incomplete combustion of biomass and fossil fuels. BC may be inaccessible for biodegradation, because of its highly condensed aromatic molecular structure and therefore stores carbon on long timescales on land and in the ocean. BC is produced on land, but is transported as dissolved BC (DBC) by the rivers to the oceans, where it cycles on millennial timescales, sequestering BC. Thus, it is important to understand the significance of BC in the context of increased fires in this vulnerable region in the face of climate change.

The Mackenzie River is a major source of terrestrial dissolved organic carbon (DOC) and the largest source of sediments to the Arctic Ocean. Here, we resolve the cycling of riverine DBC from the Mackenzie River to its fate in the Beaufort Sea, and the influence of mixing with Pacific water masses entering from the Chukchi Sea. We present DBC concentration data in ocean water, which was collected on two cruises in the Beaufort Sea in 2021 and 2022 covering the outflow of the Mackenzie River.

For DBC concentrations, we digested solid phase extracts of DOC with nitric acid to oxidize BC molecules into benzenepolycarboxylic acids (BPCAs), which were then quantified on High Performance Liquid Chromatography (HPLC). We compare the concentrations of the DBC and DOC to trace the mixing of DBC river outflow with the ocean water. Since DBC originates on land and is relatively stable to biodegradation we can resolve the pathways of DBC from the Mackenzie River to the Arctic Ocean.

 

 

How to cite: Speidel, L. G., Bröder, L., Lattaud, J., Haghipour, N., Eglinton, T. I., and Coppola, A. I.: Fate of Fire altered Organic Carbon in the arctic river-to-ocean continuum: Resolving Mackenzie River Black Carbon in the Beaufort Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7913, https://doi.org/10.5194/egusphere-egu23-7913, 2023.

EGU23-7937 | ECS | Orals | BG1.2

A New Method for Nowcasting Wildfire Risk 

Theodore Keeping, Sandy Harrison, and Iain Prentice

Wildfire risk prediction relies on the often-heuristic assessment of diverse fire potential indices, fuel maps, fire weather indices and prior fire activity data. Here we present a model nowcasting daily wildfire genesis probability and expected wildfire sizes in the contiguous US.

Predictors were selected and developed to account for climate, vegetation, topographic and human effects on wildfire genesis. Climate factors are represented by multiple fuel wetting and drying processes at daily to seasonal-scale antecedences, snowpack, and wind. We use GPP to predict fuel mass and recent growth, and dominant vegetation type. Human factors include population, landscape accessibility and ignition sources such as powerlines.

The first stage of the model predicts wildfire genesis probability as a zero-inflated process with an explicit probability of fire preclusion, whilst the second stage models fire sizes according to a generalised extreme value distribution. Nonlinear effects are accounted for via global optimisation for the domain for which each variable drives changes in fire genesis behaviour and the appropriate variable transform.

The model has good predictive and explanatory power, as shown by various performance metrics and the meaningful nonlinear relationships identified in the optimisation process. We show that this method can resolve seasonal wildfire risk dynamics well over smaller ecoregions than the observational record permits, allowing us to quantify the extent to which fire risk is determined by seasonal-scale versus daily-scale effects.

How to cite: Keeping, T., Harrison, S., and Prentice, I.: A New Method for Nowcasting Wildfire Risk, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7937, https://doi.org/10.5194/egusphere-egu23-7937, 2023.

EGU23-8075 | Posters on site | BG1.2

Impact of socio-economic factors in burnt area for future climate scenarios 

João Teixeira, Chantelle Burton, Douglas I. Kelley, Gerd Folberth, Fiona M. O'Connor, Richard Betts, and Apostolos Voulgarakis

Fire processes are a complex component of the Earth System processes and their full representation has proven to be difficult to represent Earth System Models (ESM). Because of this, these processes are often simplified in fire enabled ESMs, for instance ignitions are usually modelled to increase at low population densities up to a threshold, and reduce thereafter, as suppression effects become dominant with the increase of population density. However, socio-economic, and cultural factors can play a significant role in shaping the behaviour of fire ignitions. This study aims to address this by implementing a socio-economic factor in the fire ignition and suppression parametrisation in the INteractive Fire and Emission algoRithm for Natural envirOnments (INFERNO) based on the Human Development Index (HDI). The inclusion of this factor reduced a large long-standing positive bias found in regions of Temperate North America, Central America, Europe, and Southern Hemisphere South America. This change also leads to improvements in the model representation of fire weather and anthropogenic drivers in tropical regions, by reducing the influence of population density changes. Therefore, this framework can be used to improve understanding of the anthropogenic impacts of fire in future scenarios based on different Shared Socioeconomic Pathways.

How to cite: Teixeira, J., Burton, C., Kelley, D. I., Folberth, G., O'Connor, F. M., Betts, R., and Voulgarakis, A.: Impact of socio-economic factors in burnt area for future climate scenarios, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8075, https://doi.org/10.5194/egusphere-egu23-8075, 2023.

EGU23-9361 | ECS | Posters on site | BG1.2

Investigating Emergency Room Visits for Cardiorespiratory Diseases in Alberta and Ontario, Canada in Relation to Wildfires 

Victoria Flood, Kimberly Strong, Rebecca Buchholz, Sheryl Magzamen, and Grace Kuiper

Carbon monoxide (CO) is released during biomass burning events, resulting in decreased air quality and leading to the formation of climate forcing pollutants. An increase in wildfires has resulted in a change to the CO seasonal cycle of the North American Pacific Northwest, when comparing 2012-2018 to 2002-2011. This trend was reported using data from the Measurements of Pollution in the Troposphere (MOPITT) instrument on NASA’s Terra satellite. Similarly, an increase in summertime CO values was identified with the Fourier Transform Infrared (FTIR) spectrometer at the University of Toronto Atmospheric Observatory (TAO), over the same time period. Studies have shown correlations between wildfire smoke exposure and healthcare utilization for cardiovascular and respiratory conditions. Monthly counts of Emergency Department admissions for cardiovascular and respiratory diseases for Alberta and Ontario are investigated in relation to wildfire events in Canada and the USA. MOPITT and TAO FTIR CO columns, the Moderate Resolution Imaging Spectroradiometer (MODIS) burned area product, and provincial burned areas from Natural Resources Canada are assessed to estimate wildfire smoke exposure in the study region. This work aims to evaluate if CO can be used as a complementary tracer for health impacts from wildfire smoke exposure. 

 

How to cite: Flood, V., Strong, K., Buchholz, R., Magzamen, S., and Kuiper, G.: Investigating Emergency Room Visits for Cardiorespiratory Diseases in Alberta and Ontario, Canada in Relation to Wildfires, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9361, https://doi.org/10.5194/egusphere-egu23-9361, 2023.

EGU23-9575 | Orals | BG1.2

FRYv2.0 : a global fire patch morphology database from FireCCI51 and MCD64A1 

Florent Mouillot, Wentao Chen, Manuel Campagnolo, and Philippe Ciais

The assessment of global burned area from remote sensing is an essential climate variable driving land surface GHG emissions and energy/water budget. Gridded 0.25° or 0.5° monthly burned area have been largely used for biosphere/atmosphere interactions modelling, while recent fire/weather analysis or model developments increasingly request fire events, defined as a fire patch with intrinsic fire spread properties. Pixel level information, the finest resolution from global burned area, defined by their burn date, can be aggregated within a spatio-temporal threshold and delineate these fire events. Uncertainties in burn date, the coarse resolution of pixel resolution, multiple ignition points, or the specified values in spatio-temporal thresholds can however lead to various final fire event delineation. Currently, three major global fire event database exist (FRY, Fire Atlas, GlobFire), mostly derived from MCD64A1 pixel level 500m-resolution burned area. We propose here a new version of FRY, based on MCD64A1 and FireCCI51 at 250m, with an updated pixel aggregation method allowing for single ignition fire patches. Fire patch morphology indicators as elongation, direction, complexity have been conserved from v1.0, with additional information as ignition points from minimum burn date from burned area and more timely-accurate hotspots (VIIRS and MCD14ML), rate of spread, fire Radiative power and burn severity, as well as fraction of land cover affected, based on user requirements. The dataset is delivered as a yearly shapefile, with an attribute table referencing all information on ignition, spread and final shape. Global comparison of major information from FRYv2.0 (fire size distribution, fire number, ROS) will illustrate the effects of increasing spatial resolution and better timing from hotspots provided in this new version, freely available for the scientific community for the period 2001-2020.

How to cite: Mouillot, F., Chen, W., Campagnolo, M., and Ciais, P.: FRYv2.0 : a global fire patch morphology database from FireCCI51 and MCD64A1, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9575, https://doi.org/10.5194/egusphere-egu23-9575, 2023.

EGU23-9791 | Orals | BG1.2 | Highlight

Lightning in a changing climate and its impacts on fire area burned 

Cynthia Whaley, Courtney Schumacher, Montana Etten-Bohm, Vivek Arora, David Plummer, Jason Cole, Michael Lazare, and Ayodeji Akingunola

Lightning is an important atmospheric process for igniting forest fires – often in remote locations where they are not easily suppressed – which results in potentially large emissions of many pollutants and short-lived climate forcers. Lightning also generates reactive nitrogen, resulting in the production of tropospheric ozone, the third most important greenhouse gas. Furthermore, the changing climate is expected to change the frequency and location of lightning. As such, lightning is an important component of climate models. The Canadian Atmospheric Model, CanAM, is one such climate model that did not contain an 'online' lightning parameterization. Fire ignition in CanAM was done via an unchanging climatological lightning input. In this study, we have added a new logistical regression lightning model (Etten-Bohm et al, 2021) into CanAM, creating the capacity for future lightning predictions with CanAM under different climate scenarios. The modelled lightning and fire area burned were evaluated against measurements in a historical period with good results. Then we simulate lightning and fire area burned in a future climate scenario in order to provide an estimate on how lightning and its impacts will change in the future. This study also presents the first time that CanAM’s land fire model was used online with its atmosphere to fully simulate fires in the global earth system.

Reference:

Etten-Bohm, M., J. Yang, C. Schumacher, and M. Jun : Evaluating the relationship between lightning and the large-scale environment and its use for lightning prediction in global climate models, JGR-atmospheres, 126, e2020JD033990, 2021.

How to cite: Whaley, C., Schumacher, C., Etten-Bohm, M., Arora, V., Plummer, D., Cole, J., Lazare, M., and Akingunola, A.: Lightning in a changing climate and its impacts on fire area burned, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9791, https://doi.org/10.5194/egusphere-egu23-9791, 2023.

EGU23-10336 | Posters on site | BG1.2

A hybrid deep learning framework for predicting point-level Alaskan fires 

Hocheol Seo and Yeonjoo Kim

Fires in high latitudes are becoming more critical in terrestrial ecosystem modeling. With climate warming and dry weather condition, the fires have spread more, and widespread burning has severely damaged the ecosystem. As the fire dynamics cannot be described with the mass or energy balance equations, the fire models have been developed with different input variables, linked with different vegetation models, and widely coupled with the earth system models (ESMs) or land surface models (LSMs) with different complexities of parameterization. Here, we designed a new approach using hybrid deep learning [Long Short-Term Memory (LSTM) - Artificial Neural Network (ANN)] for predicting Alaskan natural fires and aimed to understand the impacts of fires with from the NCAR community land model 5 – biogeochemistry (CLM5-BGC). This study was conducted based on fire information provided by Alaska Interagency Coordination Center (AICC), which provides the data for each fire point, start date, end date, and total burned area from 2016-2020. As the fire duration was identified as the most important in predicting the burned area, we first trained the LSTM for predicting fire duration (i.e., fire ignition and fire persistence period) with ERA5 atmospheric forcings. Also, we trained ANN to predict the burned area with both ERA5 atmospheric forcings and fire duration. Then, we combined two models (LSTM and ANN) to simultaneously predict the fire days and burned area with climate and vegetation datasets. This hybrid model has the strength to capture large fires (>10000ha), comparing the burned area from CLM5-BGC (Correlation: 0.79). When this hybrid model is coupled with CLM5-BGC, we found that the carbon fluxes changed over Alaska. In particular, total net ecosystem exchange (NEE) increased by more than two times that of only CLM5-BGC, which could primarily affect terrestrial carbon exchanges.

Acknowledgement

This work was supported by the Korea Polar Research Institute (KOPRI, PE22900) funded by the Ministry of Oceans and Fisheries and the Basic Science Research Program through the National Research Foundation of Korea, which was funded by the Ministry of Science, ICT & Future Planning (grant no. 2020R1A2C2007670) and by the Ministry of Education (2022R1A6A3A13073233).

How to cite: Seo, H. and Kim, Y.: A hybrid deep learning framework for predicting point-level Alaskan fires, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10336, https://doi.org/10.5194/egusphere-egu23-10336, 2023.

EGU23-10389 | Orals | BG1.2

Towards mechanistic representation of wildfire effects on soil – downscaling to quantify subsurface heat fluxes 

Dani Or, Hamid Vahdat-Aboueshagh, Eden Furtak-Cole, and Sean A. McKenna

Advances in wildfire modeling have focused on refining atmospheric interactions for obvious links between local airflows, combustion dynamics, fire line advance and smoke plume transport. Yet, lasting impacts of wildfires on landscapes are linked primarily with changes in soil characteristics and alteration of ecological and hydrologic processes. Quantitative assessment of wildfire impacts requires metrics for fire-surface thermal interactions beyond qualitative surrogates such as burn severity used for ecological assessment. The highly transient and localized nature of wildfire intensity and its coarse spatial and temporal representation hinder quantitative translation of wildfire dynamics to soil heat fluxes even with the most advanced wildfire models (e.g., QuicFire, WRF-Fire, WFDS). Inspired by the pioneering works of Byram, Rothermel and Albini, we seek to derive high resolution information on fire line intensities from highly resolved fuel maps informed by fire line dynamics derived from numerical wildfire model representation. This hybrid downscaling approach (limited by the quality and resolution of fuel maps) offers a means for constraining soil surface heat fluxes at resolutions relevant to quantifying critical temperatures and duration at depth to estimate pyrolysis of soil organic carbon and the degree of soil structure alteration. Examples will be presented and discussed. 

How to cite: Or, D., Vahdat-Aboueshagh, H., Furtak-Cole, E., and A. McKenna, S.: Towards mechanistic representation of wildfire effects on soil – downscaling to quantify subsurface heat fluxes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10389, https://doi.org/10.5194/egusphere-egu23-10389, 2023.

EGU23-10651 | ECS | Posters on site | BG1.2

An annually resolved stalagmite record of fire frequency for the last 250 years in south west Australia 

Liza McDonough, Pauline Treble, Andy Baker, Andrea Borsato, Silvia Frisia, Micheline Campbell, Gurinder Nagra, Katie Coleborn, Michael Gagan, Jian-xin Zhao, and David Paterson

Stalagmites provide records of past changes in climate, vegetation, and surface events, which can be identified through variability in their chemical composition over time. This variability is the result of changes in surface environmental properties, which are reflected in the physical and chemical properties of the water that percolates into the cave, ultimately affecting the composition of the speleothem calcite. Wildfires have the potential to alter soil properties and soluble element concentrations. Consequently, stalagmite compositions have been shown to respond to increases in soil nutrients, trace metal concentrations, and changes in soil/karst bedrock hydraulic conductivity. It is, therefore, likely that stalagmites, and particularly those grown in shallow caves for which transmission of the surface signal is rapid, capture the environmental effects of wildfires in their chemical and physical properties.

We analysed a stalagmite from a shallow cave in a region known to be affected by wildfires in south-west Western Australia. Fire proxies were assessed using a multi-proxy approach. This includes water isotopes via stable-isotope ratio mass spectrometry and trace element analyses via synchrotron X-ray fluorescence microscopy and laser ablation inductively coupled plasma mass spectrometry. This approach shows that the timing of known fire events coincided with a multi-proxy response in stalagmite chemistry, including increased concentrations of phosphorus, copper, aluminium, lead, and zinc, which are interpreted to be derived from leaching of ash from burned vegetation above the cave. We also identified lower and less variable peaks in phosphorus concentrations during the pre-colonisation period, suggesting that Indigenous land management resulted in more frequent but low intensity burning. This contrasted with less frequent but more intense fires associated with post-colonisation land-management. A particularly large paleo-fire identified in 1897 appears to coincide with a peak in 𝛿18O, interpreted to have resulted from evaporation of sub-surface water during the heat of the fire. This large fire was preceded by a multi-decadal dry period identified by trace element proxies. The intensity of the 1897 fire was then exacerbated by the combination of a multi-decadal drought and a transition away from cultural burning practices by Indigenous Australians, which resulted in build-up of vegetation and dry combustible material on the forest floor.

This research is a world-first demonstration of fire events recorded in stalagmites and shows their potential to provide accurate records of both fire frequency intervals and changes in climate. Further records of past fire events from stalagmites will help to understand how past fire regimes have varied with climate, land-use change and colonisation, and will help to better guide land management practices in the future.

How to cite: McDonough, L., Treble, P., Baker, A., Borsato, A., Frisia, S., Campbell, M., Nagra, G., Coleborn, K., Gagan, M., Zhao, J., and Paterson, D.: An annually resolved stalagmite record of fire frequency for the last 250 years in south west Australia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10651, https://doi.org/10.5194/egusphere-egu23-10651, 2023.

EGU23-11016 | ECS | Posters on site | BG1.2

Speleothems as archives for palaeofire proxies 

Micheline Campbell, Liza McDonough, Pauline Treble, Andy Baker, Nevena Kosarac, Katie Coleborn, Peter Wynn, and Axel Schmitt

Environmental proxy archives such as tree rings, sediment cores, and ice cores are commonly used to investigate past fire regimes. Speleothems, naturally forming cave decorations mainly comprising of stalagmites, stalactites, and flowstones, have been extensively used as palaeoenvironmental archives as their physical attributes and chemical composition change with changed environment. Research has shown that cave drip water chemistry responds to fire events, and more recently, that speleothems can record past fire events due to physical and chemical processes which alter speleothem composition. These processes include changes to water stores due to evaporation, fracturing of the host rock, changed soil hydrophobicity, production of highly soluble lime, changes in soil CO2 production, destruction of vegetation and deposition of ash above the cave. These changes can result in shifts in δ18O and δ13C, altered concentrations of vegetation, soil and bedrock-derived elements, and incorporation of soluble ash derived elements (including phosphorus, aluminium, copper, zinc, and lead) in speleothems (McDonough et al., 2022; Campbell et al., 2022).

Changes in speleothem chemistry are typically determined using micro-analytical techniques (such as Synchrotron X-ray Fluorescence Microscopy and laser ablation inductively coupled plasma mass spectrometry) and isotope ratio mass spectrometry. These changes can be precisely and absolutely dated via uranium-series and carbon dating, and can often be resolved at high resolution via manual counting of seasonal fluctuations in organic matter and trace element concentration. This makes speleothems, particularly those grown in shallow caves in highly seasonal climates, ideal for identifying both short-lived events such as wildfires, and longer-term changes such as shifts in climate. This novel application of speleothems as archives for coupled climate and palaeofire proxies is still in its infancy but holds great potential.

Here, we present a review of this new sub-discipline. We cover its origins in cave dripwater monitoring, discuss site and sample selection, and describe the current analytical and statistical approaches used to extract fire information from speleothems. Such records will enable land managers to develop improved methods for managing fire regimes.

McDonough, L.K., Treble, P.C., Baker, A., Borsato, A., Frisia, S., Nagra, G., Coleborn, K., Gagan, M.K., Zhao, J., Paterson, D., 2022. Past fires and post-fire impacts reconstructed from a southwest Australian stalagmite. Geochimica et Cosmochimica Acta. https://doi.org/10.1016/j.gca.2022.03.020
 
Campbell, M., McDonough, L., Treble, P., Baker, A., Kosarac, N., Coleborn, K., Wynn, P.M., Schmitt, A., 2022. Speleothems as Archives for Palaeofire Proxies [preprint], https://www.authorea.com/doi/full/10.1002/essoar.10511989.1
 

How to cite: Campbell, M., McDonough, L., Treble, P., Baker, A., Kosarac, N., Coleborn, K., Wynn, P., and Schmitt, A.: Speleothems as archives for palaeofire proxies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11016, https://doi.org/10.5194/egusphere-egu23-11016, 2023.

EGU23-11297 | Orals | BG1.2

Effects of land use, fuel loads and fuel moisture on fire intensity and fire emissions in South America derived by reconciling bottom-up and top-down satellite observations 

Matthias Forkel, Niels Andela, Vincent Huijnen, Christine Wessollek, Alfred Awotwi, Daniel Kinalczyk, Christopher Marrs, and Jos de Laat

Emissions from vegetation fires in tropical forests have the potential to turn the global land carbon sink into a source, affect atmospheric chemistry, and hence air quality. While natural forest fires are a rare phenomenon in tropical forests of South America and are usually of rather low intensity, deforestation fires and small land clearings in systems with high fuel loads can cause intense fires and high emissions. However, the high moisture content in tropical forests causes incomplete combustion and higher emissions of carbon monoxide (CO) than of carbon dioxide. The interacting effects of land use change, fuel load and moisture on fire intensity and emissions is, however, difficult to quantify at large scales because not all of those components are readily available from Earth observations in a consistent way. 

Here, we make use of several satellite products on vegetation, fire activity and atmospheric composition to quantify the effects of land use, fuel loads, fuel moisture on fuel consumption, emission factors and hence on emissions and atmospheric trace gas concentration. First, we use observations of active fires and fire radiative power from the VIIRS and Sentinel-3 SLSTR sensors to map different fire types (forest fires, deforestation fires, small land clearing and agricultural fires, savannah fires). Second, we integrate satellite products of canopy height, above-ground biomass, leaf area index, land cover and soil moisture in a novel data-model fusion framework to estimate fuel loads and moisture in vegetation, surface litter and woody debris. We then combine in a bottom-up approach the fire types with fuel loads and moisture to estimate fuel consumption and fire emissions using default emission factors. Third, we use observations from Sentinel-5p TROPOMI and the Integrated Forecast Systems (IFS) of the Copernicus Atmosphere Monitoring Service to compare the bottom-up estimates with distributions of CO and NOx in the atmosphere, which allows optimising emissions and associated emission factors.

Our reconciled estimates of fire emissions outperform previous CO estimates e.g. from the Global Fire Assimilation System, which demonstrates an improved estimation of fire carbon emissions. The results show that the high fire intensity and emissions in tropical deforestation fires originate from the burning of high loads of woody biomass and coarse woody debris. The high fuel moisture content causes higher emission factors of CO in tropical forests than in savannah fires and hence higher absolute emissions of CO. Our new model approaches and satellite products allow to provide an integrated assessments on the effects of fuel and fire behaviour on fire emissions.

How to cite: Forkel, M., Andela, N., Huijnen, V., Wessollek, C., Awotwi, A., Kinalczyk, D., Marrs, C., and de Laat, J.: Effects of land use, fuel loads and fuel moisture on fire intensity and fire emissions in South America derived by reconciling bottom-up and top-down satellite observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11297, https://doi.org/10.5194/egusphere-egu23-11297, 2023.

EGU23-11559 | ECS | Orals | BG1.2

Identifying the limits to fire growth in Eastern Siberia 

Thomas Janssen and Sander Veraverbeke

Boreal forests store about one third of the world’s forest carbon and may store even more carbon in the future because of the positive effects of rising atmospheric CO2 concentrations on photosynthesis and plant growth. However, fire frequency and severity have also been increasing in boreal forests in the last decades, which might offset their carbon sink potential. In Eastern Siberia, the dry and hot summers of 2020 and 2021 showed exceptionally high fire activity. However, even large fires that can spread for several months, eventually come to an end. This can be because of a change in the weather or because fires run out of fuels. Here, we aim to quantify the controls of fire growth in Eastern Siberia using high resolution landscape variables and hourly ERA-5 meteorological variables. We harmonized the burned area product from the Fire Climate Change Initiative and active fire product from the Visible Infrared Imaging Radiometer Suite, and derived fire perimeters from them for the period between 2012 and 2021. Along these fire perimeters, we then identified spatial changes in landscape variables (i.e. a decline in tree cover or increase in surface water) and temporal changes in hourly vapor pressure deficit and wind. By doing so, we could attribute causes of why fires stopped spreading.

How to cite: Janssen, T. and Veraverbeke, S.: Identifying the limits to fire growth in Eastern Siberia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11559, https://doi.org/10.5194/egusphere-egu23-11559, 2023.

EGU23-11992 | Orals | BG1.2

Assessing the feasibility of prescribed burning as a fire risk reduction tool for The Netherlands 

Niels van Manen, Albert Buxó, Linde Egberts, Laura Houwaard, Lennard Jacobsen, Jip Keesom, Martijn Reijners, David van Slooten, Anneloes Teunisse, and Anoek van Tilburg

Climate change is expected to cause prolonged and more severe droughts in Europe, increasing landscape fire occurrence. Since The Netherlands has a high population density in areas typified as ‘Wildland-Urban Interface’, a genuine risk for Dutch society arises. Landscape management, such as prescribed burning, can reduce fire risk. Prescribed burning is executed by intentionally burning the low and understory vegetation, limiting fuel for a landscape fire, under controlled conditions. In this interdisciplinary research, conducted by a team of (early career) researchers from climate science, cultural studies, hydrology, mathematics and spatial economics, we aim to assess whether prescribed burning can be used in The Netherlands as a fire risk reduction tool in natural areas with a high fire risk.

 

The Netherlands has a well-developed flood management system. However, it lacks such holistic approaches to landscape fire management. Landscape managers and researchers can learn from Dutch flood management by applying the secondary objective, improvement of spatial quality, to prescribed burning. In this research we assess the potential for improving spatial quality through prescribed burning, by adapting the spatial quality framework of the Dutch Room for the River project. Our framework looks at the three pillars burning effectiveness, ecological robustness, and cultural meaning at the potential prescribed burning sites. Burning effectiveness is highest in natural areas (Natura 2000 sites), with high fire risk and the presence of low vegetation. Ecological robustness measures the disturbance prescribed burning could cause in a landscape. Disturbance depends on the burning frequency and intensity, as well as on the type of vegetation that is burned and the usage of the area. In groundwater protection areas, seepage of harmful elements could cause more disturbance. These areas are therefore excluded from the analysis. From the perspective of cultural meaning, social perceptions influence the measure’s performance. Cultural significance and landscape identification provide various perspectives on fires and prescribed burning. Categorizing the different levels of engagement, based on an engagement pyramid, can deliver a basis for implementing prescribed burning.

 

Preliminary analyses result in a selection of 15 Natura 2000 sites in The Netherlands where prescribed burning could be feasible, varying from the Voornes Duin (14 km2) to the Veluwe (885 km2). These areas are mostly vegetated with coniferous and mixed forests. Prescribed burning potentially causes more disturbance in grasslands. However, since none of the 15 areas contain more than 24% grassland, prescribed burning could still be feasible at all locations. In the area of the Veluwe, qualitative interviews with the local population indicate support for fire management, such as prescribed burning, as they are aware of the risks imposed by landscape fires.

 

The final research results can contribute to the improvement of fire management in both The Netherlands and other North-Western European countries with similar vegetation and climate change effects.

How to cite: van Manen, N., Buxó, A., Egberts, L., Houwaard, L., Jacobsen, L., Keesom, J., Reijners, M., van Slooten, D., Teunisse, A., and van Tilburg, A.: Assessing the feasibility of prescribed burning as a fire risk reduction tool for The Netherlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11992, https://doi.org/10.5194/egusphere-egu23-11992, 2023.

EGU23-12559 | ECS | Posters on site | BG1.2

High-latitude wildfires, atmospheric composition, and climate 

Eirini Boleti, Katie Blackford, Stelios Myriokefalitakis, and Apostolos Voulgarakis

In high-latitude regions, larger and more frequent fires have been occurring over recent years, a tendency that is expected to continue in the coming decades due to warmer temperatures and regionally decreased precipitation imposed by climate change (IPCC,2019). Boreal wildfires in general are a significant source of CO2 emissions, as well as other greenhouse gases and aerosols (Akagi et al. 2011; Van Der Werf et al. 2010), e.g. emissions from boreal forests between 1997 and 2016 accounted for 7.4% of the global emissions (van der Werf et al. 2017). The effects of boreal fires on future climate have not been investigated and are potentially of great importance since climate change is occurring more rapidly in those high-latitude areas. More flammable forests in addition to the large carbon-rich peatlands, will potentially lead to devastating consequences.

The overall goal of our project is to quantify the effects of high-latitude wildfire emissions on atmospheric composition as well as climate. For this purpose, simulations with the EC Earth Earth System Model (ESM) are being employed to characterize the past, present and future variability and changes of wildfires especially in high latitudes. In the results presented here, we demonstrate how the EC Earth model performs when forced with prescribed fire emissions (GFED4) and with a more detailed peat fire module developed by our team. The mean state, seasonality, and interannual variability of fire emissions and key atmospheric constituent abundances (black carbon, organic carbon, NOx, CO, ozone, amongst others) are validated in the model, using a range of observational datasets. This validation exercise is a key step before employing the EC-Earth model for quantifying future impacts of high-latitude fires on atmospheric composition and climate.

 

IPCC,2019: Jia, G., E. Shevliakova, P. Artaxo, N. De Noblet-Ducoudré, R. Houghton, J. House, K. Kitajima, C. Lennard, A. Popp, A. Sirin, R. Sukumar, L. Verchot, 2019: Land–climate interactions. In: Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems [P.R. Shukla, J. Skea, E. Calvo Buendia, V. Masson-Delmotte, H.-O. Pörtner, D.C. Roberts, P. Zhai, R. Slade, S. Connors, R. van Diemen, M. Ferrat, E. Haughey, S. Luz, S. Neogi, M. Pathak, J. Petzold, J. Portugal Pereira, P. Vyas, E. Huntley, K. Kissick, M, Belkacemi, J. Malley, (eds.)]. In press.

Akagi, S.K. et al., 2011: Emission factors for open and domestic biomass burning for use in atmospheric models. Atmos. Chem. Phys., 11, 4039–4072, doi:10.5194/acp-11-4039-2011.

Van Der Werf, G.R. et al., 2010: Global fire emissions and the contribution of deforestation, savanna, forest, agricultural, and peat fires (1997–2009). Atmos. Chem. Phys., 10, 11707–11735, doi:10.5194/acp-10-11707-2010.

Van Der Werf, G.R. et al., 2010: Global fire emissions and the contribution of deforestation, savanna, forest, agricultural, and peat fires (1997–2009). Atmos. Chem. Phys., 10, 11707–11735, doi:10.5194/acp-10-11707-2010.

How to cite: Boleti, E., Blackford, K., Myriokefalitakis, S., and Voulgarakis, A.: High-latitude wildfires, atmospheric composition, and climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12559, https://doi.org/10.5194/egusphere-egu23-12559, 2023.

EGU23-12604 | Orals | BG1.2

Causes of uncertainty in simulated burnt area by fire-enabled DGVMs 

Matthew Forrest, Chantelle Burton, Markus Drüke, Stijn Hantson, Fang Li, Joe Melton, Lars Nieradzik, Sam Rabin, Stephen Sitch, Chao Yue, and Thomas Hickler

Fire-enabled dynamic global vegetation models (DGVMs) can be used to study how fire activity responds to its main drivers, including climate/weather, vegetation and human activities, at coarse spatial scales. Such models can also be used to examine the effects of fire on vegetation, and, when embedded in Earth system models, investigate the feedback of fire on the climate system. Thus they are valuable tools for studying wildfires. Accordingly, the Fire Model Intercomparison Project (FireMIP) was established to evaluate and utilise these models using consistent protocols.

Here we present the second round of FireMIP simulations to focus historic wildfire drivers (1901 to present). A six-member ensemble of simulations from fire-enabled DGVMs was compared to remotely-sensed burnt area observations and to the previous round of historical FireMIP simulations. We found that the model skill when simulating spatial patterns of burnt area shows modest improvements compared to the previous FireMIP round, and that the simulations mostly reproduce the decreasing trend in global burnt area found over the last two decades. However, whilst the broad global patterns are reasonable, there are considerable discrepancies with regards to regional agreement and timing of burnt area. Furthermore, the models show diverging trends in the pre-satellite era.

To investigate further and inform future model development, we explored the residuals between simulated burnt area from the FireMIP models and remotely-sensed burnt area as a function of climate, vegetation, anthropogenic and topographic variables using generalised additive models (GAMs). We found some common responses across the models, with many over-predicting fire activity in arid/low productivity areas and all models under-predicting at low road density. However, with respect to other variables, such as wind speed and cropland fraction, the models residuals showed divergent responses. It is anticipated that these results should aid further development of global fire models in terms of driving variables, process representations and model structure.

How to cite: Forrest, M., Burton, C., Drüke, M., Hantson, S., Li, F., Melton, J., Nieradzik, L., Rabin, S., Sitch, S., Yue, C., and Hickler, T.: Causes of uncertainty in simulated burnt area by fire-enabled DGVMs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12604, https://doi.org/10.5194/egusphere-egu23-12604, 2023.

EGU23-12731 | ECS | Posters on site | BG1.2

Quantifying the direct influence of climate change on the rate of spread of wildfires in the Iberian Peninsula 

Martín Senande-Rivera, Damián Insua-Costa, and Gonzalo Míguez-Macho

Due to its strong connection with meteorological conditions and vegetation structure, fire activity is affected by anthropogenic climate change. As a direct effect, climate regulates fuel moisture, so warmer and drier conditions are linked to higher fuel flammability, increasing fire risk. We use data from ERA5 and different CMIP6 models to build a database of fuel moisture (for both live and dead fuels) under real conditions (factual) and modified conditions without the influence of global warming (counterfactual). We then calculate the rate of spread of some observed wildfires in the Iberian Peninsula from 2001 to 2021, from both factual and counterfactual data. We find that climate change influence is already noticeable and significant. We also identify the areas most vulnerable to the impacts of climate change and the time of the year when these impacts are strongest. 

How to cite: Senande-Rivera, M., Insua-Costa, D., and Míguez-Macho, G.: Quantifying the direct influence of climate change on the rate of spread of wildfires in the Iberian Peninsula, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12731, https://doi.org/10.5194/egusphere-egu23-12731, 2023.

Tropospheric ozone (O3) is a key greenhouse gas and pollutant that is receiving increasing attention globally.  While there are many sources of tropospheric O3, precursors from human activity (Anthro) and open biomass burning (BB) are the only ones that can be controlled. As such, it is crucial for policymakers to understand the relative contributions of the two. However, determining the contribution of O3 can be challenging as it cannot be directly observed. It must be calculated by chemical transportation model (CTM) simulation which could be biased for unreal emission inventory, or estimated by real observations that assumes too simple chemical and transportation processes.

In this paper, we propose a solution by developing a deep learning (DL) model that combines both CTM simulations and observations. The DL model is able to learn a generalized relationship between unobservable O3 contribution from Anthro or BB sectors and observable mixing ratio of tracers simulated by CTM with full chemistry and transportation processes. The DL model then, when applied to observed tracers, could avoid the bias from model to provide an accurate estimation of the contributions in reality.

Our results indicate the contribution from BB to tropospheric remote ozone mixing ratio is no larger than that from Anthro emission from a global perspective, even when uncertainties are deliberately tuned to bias BB. Therefore, the reduction of anthropogenic emissions should be the top priority for controlling global background O3 levels, at least for the time period of 2016-2018 studied.

How to cite: Ma, C., Cheng, Y., and Su, H.: Biomass Burning Contributes Less to Remote Tropospheric Ozone than Human Activity, Indicated by a Deep Learning Approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13307, https://doi.org/10.5194/egusphere-egu23-13307, 2023.

EGU23-13544 | ECS | Posters on site | BG1.2

Seasonal skew of tropical savanna fires 

Tom Eames, Jeremy Russell-smith, Cameron Yates, Roland Vernooij, and Guido van der Werf

Tropical savannas and grasslands are the most frequently burned biome in the world, and fire constitutes an important part of the ecosystem. In this ecosystem it can have both rejuvenating and destructive effects, depending on several factors including fuel conditions, weather conditions, and time of year. For centuries humanity has used fire in these landscapes for hunting, land clearance, agriculture, and most recently carbon offsetting. Land managers in locations with a monsoonal climate and frequent fire regimes such as tropical savannas use prescribed burning as a management tool in the ‘early dry season’ (EDS) shortly after the last rains of the year. Fires at this time tend to be cooler, restricted to surface level and less severe, meaning they can be controlled more easily and tend to go out at night without external input. Commonly a specific, fixed date is used to indicate when this window of safe burning has expired, set based on experience of the local or regional authority. In this work, we have defined a method of determining when this window expires on the basis of active fire hotspot data from the twin MODIS instruments from 2001 through to 2021. By using the relationship between day and night-time active fire detections, we set a flexible date for the transition between the early and late dry seasons in fire-prone savannas globally in the five major tropical savanna regions - Northern & Southern hemisphere South America (NHSA & SHSA), Northern & Southern hemisphere Africa (NHAF & SHAF), and Australia (AUST). The variability across each region was high (lowest mean standard deviation annually was 24 days in NHAF and highest was 56 in AUST). The fraction of area burned in the late dry season ranged from 15% (SHSA) to as high as 85% (AUST) on average, with many parts of Africa and Australia especially showing a significant skew towards the late dry season. This suggests potential for implementation of prescribed burning programmes to increase the amount of desirable fire in the global savanna ecosystems.

How to cite: Eames, T., Russell-smith, J., Yates, C., Vernooij, R., and van der Werf, G.: Seasonal skew of tropical savanna fires, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13544, https://doi.org/10.5194/egusphere-egu23-13544, 2023.

EGU23-13603 | ECS | Orals | BG1.2

Simulating wildfire impacts on boreal forest structure over the past 20,000 years since the Last Glacial Maximum in Central Yakutia, Siberia 

Ramesh Glückler, Josias Gloy, Elisabeth Dietze, Ulrike Herzschuh, and Stefan Kruse

Even though wildfires are an important ecological component of larch-dominated boreal forests in eastern Siberia, intensifying fire regimes may induce large-scale shifts in forest structure and composition. Recent paleoecological research suggests that such a state change, apart from threatening human livelihoods, may result in a positive feedback on intensifying wildfires and increased permafrost degradation [1]. Common fire-vegetation models mostly do not explicitly include detailed individual-based tree population dynamics. However, setting a focus on patterns of forest structure emerging from interactions among individual trees in the unique forest system of eastern Siberia may provide beneficial perspectives on the impacts of changing fire regimes. LAVESI (Larix Vegetation Simulator) has been previously introduced as an individual-based, spatially explicit vegetation model for simulating fine-scale tree population dynamics [2]. It has since been expanded with wind-driven pollen dispersal, landscape topography, and the inclusion of multiple tree species. However, until now, it could not be used to simulate effects of changing fire regimes on those detailed tree population dynamics.

We present simulations of annually computed tree populations during the past c. 20,000 years in LAVESI, while applying a newly implemented fire module. Wildfire ignitions can stochastically occur depending on the monthly fire weather. Within the affected area, fire intensity is mediated by surface moisture. Fire severity depends on the intensity, with scaled impacts on trees, seeds and the litter layer. Each tree has a chance to survive wildfires based on a resistivity estimated from its height and species-specific traits of bark thickness, crown height, and their ability to resprout. The modelled annual fire probability compares well with a local reconstruction of charcoal influx in lake sediments. Simulation results at a study site in Central Yakutia, Siberia, indicate that the inclusion of wildfires leads to a higher number of tree individuals and increased population size variability compared to simulations without fires. In the Late Pleistocene forests establish earlier when wildfires can occur. The new fire component enables LAVESI to serve as a tool to analyze effects of varying fire return intervals and fire intensities on long-term tree population dynamics, improving our understanding of potential state transitions in the Siberian boreal forest.

References:

[1] Glückler R. et al.: Holocene wildfire and vegetation dynamics in Central Yakutia, Siberia, reconstructed from lake-sediment proxies, Frontiers in Ecology and Evolution 10, 2022.

[2] Kruse S. et al.: Treeline dynamics in Siberia under changing climates as inferred from an individual-based model for Larix, Ecological Modelling 338, 101–121, 2016.

How to cite: Glückler, R., Gloy, J., Dietze, E., Herzschuh, U., and Kruse, S.: Simulating wildfire impacts on boreal forest structure over the past 20,000 years since the Last Glacial Maximum in Central Yakutia, Siberia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13603, https://doi.org/10.5194/egusphere-egu23-13603, 2023.

EGU23-13941 | Orals | BG1.2 | Highlight

Wildfires, chromium and freshwater quality at tropical ultramafic catchments : A prospective study on laboratory-heated soils from New Caledonia 

Farid Juillot, Gael Thery, Cecile Quantin, Quentin Bollaert, Michael Meyer, Thomas Quiniou, Philippe Jourand, Marc Ducousso, Emmanuel Fritsch, and Guillaume Morin

During the last decade, the world faced record-breaking giant fires as observed in Australia and California, a trend that is expected to increase in the forthcoming years due to climate change (Palinkas, 2020; Sharples et al., 2016; van Oldenborgh et al., 2021). In addition to their large ecological impacts, wildfires are more and more regarded for their potential threat to human health through air pollution (Xu et al., 2020). However, water pollution resulting from wildfires represents an underestimated pathway for wildfires-induced health risk (Abraham et al., 2017). This latter impact is related to the heat generated by wildfires that can propagate towards several centimeters in the soil and transform/destroy soil components. In addition to weakening soil physical stability, such transformation/destruction can change the speciation of potentially toxic elements (PTEs) that are associated with these soil components, leading to enhanced mobility towards waterways (Abraham et al., 2017; Terzano et al., 2021). One notable PTE is chromium, which is naturally present in soils mostly as trivalent Cr(III), but can represent an environmental and health issue when occurring as hexavalent Cr(VI). Recent studies reported Cr(III) oxidation to Cr(VI) upon laboratory-heating of Cr(III)-doped Fe-oxyhydroxides (Burton et al., 2019a; 2019b). Besides, Cr(III) oxidation to Cr(VI) upon controlled heating was also demonstrated for different types of soils (Burton et al., 2019b; Rascio et al., 2022; Thery et al., 2023). All these considerations suggest a significant effect of wildfires on Cr(III) oxidation to Cr(VI) in soils, with a possible influence on Cr mobility that could further impact freshwater quality. This risk of freshwater Cr(VI) pollution is expected to particularly concern ultramafic catchments because of the related occurrence of Cr-rich soils.

We have tried to address this question by performing laboratory-heating of several soils types (Ferralsols, Cambisols and Vertisols) developed on various geological settings (ultramafic, mafic and volcano-sedimentary) in New Caledonia, a French overseas territory which is a good representative of wildfires-threatened tropical ultramafic catchments (Toussaint, 2020). The results obtained revealed a significant influence of soil heating on Cr(III) oxidation to Cr(VI), followed by an enhanced Cr(VI) mobility, in all soil types. However, the magnitude of Cr(III) to Cr(VI) oxidation and Cr mobility depended on the actual nature of the soil, Ferralsols showing the highest Cr(VI) release compared to Cambisols and Vertisols. These differences were further interpreted on the basis of the changes in Cr speciation (including redox) induced by laboratory-heating of the investigated soils, as revealed by synchrotron-based X-ray absorption spectroscopy analyses. Finally, a simple risk assessment relying on the hypothesized concentration of suspended particulate matter (SPM) issued from burned soils in the related waterways allowed to emphasize a risk of wildfires-induced freshwater Cr(VI) pollution for ultramafic catchments composed of Ferralsols (Thery et al., 2023). Beyond the single case of New Caledonia, the results of this study point to the need to foster collaborative studies in order to further evaluate this risk of wildfires-induced freshwater Cr(VI) pollution at tropical ultramafic catchments on a global scale.

How to cite: Juillot, F., Thery, G., Quantin, C., Bollaert, Q., Meyer, M., Quiniou, T., Jourand, P., Ducousso, M., Fritsch, E., and Morin, G.: Wildfires, chromium and freshwater quality at tropical ultramafic catchments : A prospective study on laboratory-heated soils from New Caledonia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13941, https://doi.org/10.5194/egusphere-egu23-13941, 2023.

EGU23-14211 | ECS | Posters on site | BG1.2

Impact of biomass burning on the chemical composition of Arctic aerosols using mass spectrometry 

Yvette Gramlich, Karolina Siegel, Sophie L. Haslett, Radovan Krejci, Paul Zieger, and Claudia Mohr

Biomass burning releases numerous aerosol particles into the air, influencing the radiative budget by scattering or absorbing solar radiation and by influencing cloud properties through acting as cloud condensation nuclei. These aerosol particles contain black and organic carbon and can be transported over large distances, reaching also pristine environments such as the Arctic. Due to the rising global temperature the fire activity has increased, and record-breaking black carbon concentrations have been observed in the Arctic (Stohl et al., 2007). Biomass burning events reaching the Arctic have been observed to increase the aerosol number concentration by about one to two orders of magnitude (Lathem et al., 2013). Although a lot of attention has been drawn to the physical characteristics of fire plumes, changes in chemical composition, specifically in the Arctic, are studied to a lesser extent. In this study we report molecular-level information on the chemical characteristics of biomass burning aerosol particles measured during different plumes reaching the island of Svalbard during 2020. These measurements were part of the year-long NASCENT (Ny-Ålesund aerosol cloud experiment; Pasquier et al., 2022) campaign, and were conducted using a filter inlet for gases and aerosols coupled to a high-resolution time-of-flight mass spectrometer (FIGAERO-CIMS) using iodide as reagent ion. We use the particle-phase levoglucosan, a well-known tracer for biomass burning released from cellulose combustion, obtained from the FIGAERO-CIMS to identify biomass burning events, and will discuss the chemical characteristics of the properties of the events compared to non-events and implications for aerosol radiative and hygroscopic properties. In addition to a better understanding of the chemical composition of aged fire plumes reaching the Arctic, our study will also give insights on the time scales on which the background Arctic air can be disturbed by fire activity. 

References:
Stohl et al., Atmospheric Chem. Phys., 7, 511–534, 2007
Lathem et al., Atmospheric Chem. Phys., 13, 2735–2756, 2013
Pasquier et al., Bull. Am. Meteorol. Soc., 103, E2533–E2558, 2022

How to cite: Gramlich, Y., Siegel, K., Haslett, S. L., Krejci, R., Zieger, P., and Mohr, C.: Impact of biomass burning on the chemical composition of Arctic aerosols using mass spectrometry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14211, https://doi.org/10.5194/egusphere-egu23-14211, 2023.

EGU23-15549 | ECS | Posters on site | BG1.2

Regional precipitation variability modulates Holocene fire history of Iceland 

Nicolò Ardenghi, Gifford H Miller, Áslaug Geirsdóttir, David J Harning, Jonathan H Raberg, Thor Thordarson, and Julio Sepúlveda

We present the first continuous Holocene fire record of Iceland from a lacustrine archive in the northeast region. We use pyrogenic PAHs (polycyclic aromatic hydrocarbons) to trace shifts in fire regimes, paired to a continuous record of n-alkanes, faecal sterols, perylene, biogenic silica, and 13C, as proxies for soil erosion, lake productivity, and human presence.

Paleoclimate research across Iceland provides a template for changes in climate across the northern North Atlantic. The role of orbitally driven cooling, volcanism, and human impact as triggers of local environmental changes, such as fire and soil erosion, is debated. While there are indications that human impact could have reduced environmental resilience in a context of deteriorating climatic conditions, it is still difficult to resolve to what extent human and natural factors affected Iceland landscape instability, due also to a lack of data on natural fire regime prior and during human colonisation.

Pyrogenic PAHs can be formed during the incomplete combustion of biomass initiated by humans or natural wildfires. Factors such as fire temperature, biomass typology, and source distance can strongly affect pyrogenic PAH molecular weight and spatial distribution.
Faecal sterols/stanols and their ratios have been used in archaeological and paleoclimate studies to detect human and/or livestock/herbivore waste. The absence of large herbivorous mammals and humans in Iceland prior to settlement means that increases in the occurrence of faecal sterols and bile acids over natural background values should mark the arrival of humans and associated livestock in the catchment, which could be traced regionally.

Our results indicate that the Icelandic fire regime during the Holocene followed four main phases. Among these, a very long period centred around the Holocene climatic optimum (ca 9.5 – 4.5 ka BP) was characterised by a generally low frequency fire regime, both in the lake catchment as in the whole north-eastern Iceland. This same period was also marked by relatively low background levels of faecal sterols/stanols. At 4.5 ka BP a new phase started, with a general increase of all PAHs values. According to both our PAH and sterol data, there is no apparent human signal around the 9th century C.E., where an increase in man-made fires would likely be expected in connection to the historical data of Viking colonisation of Iceland (870s C.E.), suggesting that fire regimes have primarily been controlled by natural factors.
In addition, the pyrogenic PAHs record also differs from the trend of a general stepwise climatic “deterioration” previously highlighted by other lake proxies throughout Iceland, linked to decreasing summer insolation and related cooling, as highlighted also by our other proxies.

A comparison to recent palynological data from a nearby site and to δD data from the NW region suggest shifts in NAO regimes as the main forcing behind shifting fire regimes in Iceland. Changes in precipitation regimes would have determined shifts in the composition of the regional vegetational community, increasing fuel availability and flammability with decreasing precipitation, leading to widespread low temperature fires, easily trigged by frequent volcanic episodes.

How to cite: Ardenghi, N., Miller, G. H., Geirsdóttir, Á., Harning, D. J., Raberg, J. H., Thordarson, T., and Sepúlveda, J.: Regional precipitation variability modulates Holocene fire history of Iceland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15549, https://doi.org/10.5194/egusphere-egu23-15549, 2023.

EGU23-15670 | ECS | Orals | BG1.2 | Highlight

Identifying tipping points and threshold values for ecosystem functioning in northern peatlands during the climate crisis (PEATFLAMES) 

Luke Andrews, Michał Słowiński, Harry Roberts, Katarzyna Marcisz, Piotr Kołaczek, Agnieszka Halaś, Dominika Łuców, and Mariusz Lamentowicz

Peatlands are globally important carbon sinks and stores. Climate change threatens to alter carbon cycling in some regions of the Northern Hemisphere, causing them to become net sources of atmospheric carbon, exerting a positive feedback upon global climate. Furthermore, enhanced drying, increased human activity and vegetation succession in response to a warming climate have increased the frequency of wildfires in some peat-bearing regions, including areas underlain by permafrost. Such events can cause thousands of years’ worth of formerly stable carbon to be rapidly released into the atmosphere, imparting further climate warming.

 

The future response of peatlands to climate warming and wildfire remains uncertain, and as a result peatlands are rarely included in Earth System Models, despite their importance in the global carbon system. Understanding how changes in climate and anthropogenic activity in the past affected peatland ecosystem functioning will improve our understanding of how these sensitive ecosystems may respond to future projected changes and thus reduce this uncertainty.

 

Our project aims to assess how warming, drought and wildfire have impacted the resilience of peatlands and permafrost in the Northern Hemisphere over the past c. 2000 years. Several peat cores spanning a latitudinal gradient covering several regions including Russia, Poland, the Baltic states and Scandinavia will be analysed using multiple palaeoecological proxies at high resolution to reconstruct past changes in wildfire frequency, hydrology and vegetation. This will allow us to define baselines and threshold values for ecosystem shifts relevant to future projected changes in climate.

 

How to cite: Andrews, L., Słowiński, M., Roberts, H., Marcisz, K., Kołaczek, P., Halaś, A., Łuców, D., and Lamentowicz, M.: Identifying tipping points and threshold values for ecosystem functioning in northern peatlands during the climate crisis (PEATFLAMES), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15670, https://doi.org/10.5194/egusphere-egu23-15670, 2023.

EGU23-16152 | Posters on site | BG1.2

Temporal analysis of wildfire emissions in the Northwest of Spain using ESA CCI data 

Patricia Oliva and César Quishpe

The Northwest of the Iberian Peninsula is one of the European regions with the highest frequency of forest fires. However, in the last decade fires in this region have burned larger areas and later in the fire season. Assessing the damage caused by fire and the pollutants released in the burning process is important to understand the effects on ecosystems and the carbon cycle, the recurrence of fires, and the effect on human health. In this work, we performed the estimation of emissions released in Galicia (Northwest Spain) in the last six years combining existing ESA CCI products. To quantify the area burned, we used the products from the Burned Area Algorithm developed within the Fire Climate Change Initiative (FireCCI) project. Then, the characterization and quantification of the total biomass were obtained from the Biomass CCI project at 100 m resolution by extracting the mean biomass by vegetation type from CORINE Land cover 2018. The burning efficiency factor was fitted using burn severity estimates from the dNBR calculation on the Sentinel-2 data. The emissions factors were selected from the literature. Our results show that during the last few years, there is a positive trend of annual emissions in Galicia. The sporadic maximums were registered in the years 2017 and 2022 when the climatic conditions aggravated the fire behaviour. In addition, Galicia is the region of Spain that registers the highest average estimates of emissions from fires since a high percentage of the affected area is occupied by pine and eucalyptus forests. These emissions contribute to a drastic decrease in air quality influencing the climate and affecting public health. Finally, we verified that adapting the burning efficiency factors to the specific conditions of the affected ecosystem generates more precise emission estimates.

How to cite: Oliva, P. and Quishpe, C.: Temporal analysis of wildfire emissions in the Northwest of Spain using ESA CCI data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16152, https://doi.org/10.5194/egusphere-egu23-16152, 2023.

EGU23-16241 | ECS | Posters virtual | BG1.2

Characterizing the fire regime evolution and land-use change in the Dry and Wet Chaco between 2001 and 2019 

Rodrigo San Martin, Catherine Ottle, and Anna Sörensson

Wildfires play an essential role in the biogeophysical cycles of different world ecosystems, from dry savannas to humid wetlands. During the last decades, fire regimes of several global regions began to present significant alterations due to climate change and human land-use pressure. The South American Gran Chaco ecoregion contains one of the most important reservoirs of native forests and biodiversity in the world, including the largest continuous dry tropical forest and some of the most extensive wetlands. The area presents a marked precipitation gradient from the East (wet) to the West (dry), which is manifested in vegetation (from wetlands to dry forests and shrublands). In this work, we mapped natural vegetation with the European Space Agency (ESA) Climate Change Initiative (CCI) medium-resolution land cover maps (MRLC v2.0.7; annual - 300m) and fires with the ESA CCI Fire product (FireCCI51; monthly - 250m) in the Gran Chaco between 2001 and 2019 to establish the past and current effects and dynamics of fires in the area (which are primarily human ignited). To assess the region’s climatology, we used the ERA5 bias-corrected reanalysis dataset (WFDE5; daily - 0.5º). Our results highlight the distinct dynamics of fires in the wet and dry areas of the Gran Chaco, showing two fire seasons - summer and winter - in the wet areas (where grasses predominate) and one fire season - winter - in the dry areas (where shrubs and trees are more abundant). Examining the correlations between annual rain anomalies and burnt area, we find that precipitation anomalies have different effects in dry and wet areas throughout the region’s precipitation gradient. Correlations change from positive in the drier areas to negative in the wetter areas. These results may reflect that summer and winter fires do not have the same drivers and the key role of the available biomass limiting the fire expansion. Since biomass is more dependent on precipitation in dry areas compared to wetter ones, the correlation of winter fires with precipitation is positive in the drier regions. The negative correlations obtained in the summer season could be explained by the fact that summer fires essentially occurred in the wetter part of the Chaco and are intended (through human ignition) to increase the grasslands’ productivity; this practice could be more frequent during negative precipitation anomalies compared to positive ones. Further analysis will try to confirm these findings with biomass satellite data.   

How to cite: San Martin, R., Ottle, C., and Sörensson, A.: Characterizing the fire regime evolution and land-use change in the Dry and Wet Chaco between 2001 and 2019, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16241, https://doi.org/10.5194/egusphere-egu23-16241, 2023.

EGU23-16504 | Posters on site | BG1.2

History of fire regime shifts during the last 1000 years in Northeastern Mongolia 

Michał Słowiński, Milena Obremska, Dashtseren Avirmed, Michał Woszczyk, Saruulzaya Adiya, Dominika Łuców, Agnieszka Mroczkowska, Agnieszka Halaś, Witold Szczuciński, Andrzej Kruk, Mariusz Lamentowicz, Joanna Stańczak, and Natalia Rudaya

Recent years have seen rapid climatic changes in Central Asia, particularly Mongolia. An increase in the thickness of the active layer above permafrost and considerable changes to the vegetation structure are likely outcomes of the long-term temperature rise and precipitation changes. The management of future habitats or the biodiversity of northern Mongolia faces significant difficulties from rising temperatures, prolonged and frequent droughts, and gradual permafrost degradation. Our knowledge of the historical processes involved in permafrost degradation and the ensuing ecological effects is still mostly incomplete. These connections may be used to explain changes in the fire regime, permafrost melting, and plant distribution in the Khentii mountains region. Therefore, based on a multiproxy study of peat archive data, we provide the first high-resolution fire history from northeastern Mongolia over the last 1000 years (micro- and macroscopic charcoals, charcoal size classes and morphotypes, peat geochemistry). We examined microscopic and macroscopic charcoal particles as a proxy for fire activity. We also tracked changes in regional and local plant composition using pollen data. To investigate how changes in fire regimes and the climate affect the functioning of the peatland ecosystem, we also conducted a geochemical analysis.

Additionally, to better comprehend the changes in earlier fire regimes and fire-vegetation connections, we employed the morphotypes of macrocharcoal to pinpoint vegetation burning. This study's primary objective is to evaluate the impact of human behavior, vegetation, and prolonged droughts on the incidence of fire regime transitions during the past 1000 years in Central Asia permafrost marginal zone (Mongolia). The findings showed that most of the fires in the area were probably started by natural causes, presumably connected to heatwaves that resulted in prolonged droughts. We have established a connection between increased fires and the local weather phenomena known as "dzud", a catastrophic confluence of winter snowfall and droughts that impacts fire intensity.

The study is the result of research project No. 2017/01/X/ST10/01216 and 2018/31/B/ST10/02498 funded by the Polish National Science Centre.

How to cite: Słowiński, M., Obremska, M., Avirmed, D., Woszczyk, M., Adiya, S., Łuców, D., Mroczkowska, A., Halaś, A., Szczuciński, W., Kruk, A., Lamentowicz, M., Stańczak, J., and Rudaya, N.: History of fire regime shifts during the last 1000 years in Northeastern Mongolia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16504, https://doi.org/10.5194/egusphere-egu23-16504, 2023.

EGU23-16912 | ECS | Posters on site | BG1.2

Fire, Work with Me: A PAH record from a Southwestern US speleothem 

Jonathan Smolen, Isabel Montañez, and Michael Hren

Polycyclic aromatic hydrocarbons (PAHs) are molecules produced during incomplete combustion of organic matter and have been increasingly utilized as paleo-proxies for wildfires. More recently, their incorporation from drip water into speleothems has been utilized in conjunction with the stable isotopic and trace elemental measurements of host carbonate and fluid inclusions in order to assess a coupled record of fire and hydroclimate. Numerous studies have focused on cave systems in the Southwestern U.S., which has experienced highly variable hydroclimate and massive wildfires with past climate changes. Here, we present a PAH record covering ~19-11.5 ka obtained from a precisely dated and well-studied ML-1 stalagmite obtained from McLean’s Cave in the central Sierran foothills, CA. Total concentrations of four-ring PAHs reach maximum values from ~16.8-15 ka, associated with the first stage (1a) of Heinrich Stadial 1 (HS1) interval – this is interpreted as increased levels of soil PAHs produced from regional wildfires. Covariance of isomeric diagnostic ratios with total concentration indicates a shift in the nature of the associated fires, separating effects of PAH mobility in altered soils as well as shifts in soil water transport, stalagmite growth rates, and precipitation amounts. Paired climate signals from independent regional proxies are discussed, as well as factors affecting the interpretation of PAH signals in speleothems. Considerations and methods using small (~1g) speleothem samples are presented, with a focus on simultaneous extraction of useful paleoenvironmental information from other molecular biomarkers entombed within speleothems.

How to cite: Smolen, J., Montañez, I., and Hren, M.: Fire, Work with Me: A PAH record from a Southwestern US speleothem, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16912, https://doi.org/10.5194/egusphere-egu23-16912, 2023.

EGU23-17450 | ECS | Orals | BG1.2 | Highlight

First results of a field campaign focused on overwintering zombie fires 

Thomas D. Hessilt, Sander Veraverbeke, Emily Ogden, Jason Paul, Merritt Turetsky, Max van Gerrevink, Raquel Alfaro-Sanchez, Oleg Melnik, Rebecca C. Scholten, and Jennifer Baltzer

Fire is a major disturbance in the boreal forests of the high northern latitude. Fire extent and severity have been increasing in recent decades, and the occurrence of overwintering ‘zombie’ fires has been linked to recent fire extremes. Overwintering fires are fires which were seemingly extinguished at the end of the boreal fire season yet smolder during winter to re-emerge as a flaming fire in the subsequent spring. So far, overwintering fires have only been investigated using satellite imagery. Here, for the first time, we show preliminary results from a field campaign that measured in situ impacts of fires that overwintered from 2014 to 2015 in the Canadian Northwest Territories. We measured among other the burn depth in organic soils, and characterized micro-topography. We also qualitatively assessed how fires may have overwintered. We compared nine overwintering fire sites, which burned during both 2014 and 2015, with six sites that only burned in 2014 and five nearby unburned sites. The average burn depth (±SD) of the overwintering fires was 6.8 ± 1.6 cm and significantly deeper compared to 6.1 ± 1.2 cm in the single fire sites (P < 0.01). Somewhat surprisingly, the majority of overwintering fires occurred in mesic sites with large productive trees. Only two overwintering sites were sampled in mesic-subhygric to subhygric sites dominated by black spruce (Picea mariana). The unburned control sites often featured a micro-topography of hummocks and hollows. This micro-topography was leveled in overwintering fires sites because of severe burning in organic soils. In overwintering sites, most of the organic layer was consumed. This may have led to prolonged smoldering in the root systems of trees. Our results are the first to quantify the burn depth of overwintering fires, and also show that overwintering does not only happen through deep smoldering in organic soils, yet can also occur from smoldering in tree boles and root systems of burned and fallen trees.

How to cite: Hessilt, T. D., Veraverbeke, S., Ogden, E., Paul, J., Turetsky, M., van Gerrevink, M., Alfaro-Sanchez, R., Melnik, O., Scholten, R. C., and Baltzer, J.: First results of a field campaign focused on overwintering zombie fires, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17450, https://doi.org/10.5194/egusphere-egu23-17450, 2023.

EGU23-703 | ECS | Posters on site | BG1.3

How will Solar Radiation Modification affect Cropland Suitability in West Africa? 

Temitope Samuel Egbebiyi, Christopher Lennard, Izidine Pinto, Romaric Odoulami, Piotr Wiolski, Simone Tilmes, and TEMITOPE SAMUEL EGBEBIYI

Cropland suitability, a process of evaluating the capability of a piece of land in relation to the growing conditions of a given crop, is highly essential for agricultural planning. Projected changes in the future climate are expected to significantly affect the agricultural sector, notably agricultural production which include cropland suitability. Although, previous studies have shown Solar Radiation Modification (SRM), which involves the injection of sulfur into the stratosphere to reduce insolation of the sun and cool the planet, could mitigate the impact of climate change (hereafter GHG) on agricultural production, however there is still a lack of understanding on how Stratospheric Aerosol Injection (SAI) intervention (an SRM technique) will affect cropland suitability in West Africa. The present study examines the impact of GHG and SAI on Legumes (Cowpea, Soyabean and Groundnut) and Root and Tuber (Cassava, Potato and Yam) suitability and planting season over West Africa. The Stratospheric Aerosol Geoengineering Large Ensembles (GLENS) simulation for the historical, GHG and SAI experiments for the period 1980-2009 and 2060-2089. Ecocrop, a crop suitability model was used to investigate the impact of GHG and SAI on the over West Africa owing to their economic importance to the region. Our findings shows while SAI offset the impact of GHG on temperature it leads to a reduction in rainfall over West Africa. Crop suitability decreases northwards over the region. SAI intervention will lead to an increase (over 12%) in highly suitable area for Cassava and Potato compared to GHG but leads to 3% decrease compared to historical period. In contrast, SAI results in decrease (6%) in suitable area for Legumes when compared to GHG impact over West Africa. In addition, SAI intervention will lead to a 1-2month early planting season for all legumes crops and Yam over West Africa but delay of about 2months for Cassava and Potato. The study will assist to improve our understanding on SAI intervention at mitigating GHG impact on Legumes and Root & Tuber crop production over West Africa. It will also help inform policy maker in their decision making of adaptation strategies to ensure food security and zero hunger and healthy nutrition in West Africa.

How to cite: Egbebiyi, T. S., Lennard, C., Pinto, I., Odoulami, R., Wiolski, P., Tilmes, S., and EGBEBIYI, T. S.: How will Solar Radiation Modification affect Cropland Suitability in West Africa?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-703, https://doi.org/10.5194/egusphere-egu23-703, 2023.

EGU23-3775 | ECS | Orals | BG1.3 | Highlight

Aerosol-induced radiation effect and the potential influence of stringent emission control on terrestrial carbon uptake in China 

Lingfeng Li, Bo Qiu, Xin Huang, Weidong Guo, Xin Miao, Jiuyi Chen, Yueyang Ni, and Xiaohui Tian

Atmospheric aerosols can scatter and absorb the incident solar radiation, and thus impact the land carbon cycle by perturbating the radiation required for photosynthesis. Atmospheric aerosols inhibit the carbon uptake by terrestrial ecosystems through reducing the total amount of incident radiation, while the increased proportion of diffuse irradiance is known to promote photosynthesis. In the past few decades, with the rapid industrialization and urbanization, China has suffered from frequent haze pollution episodes, which have brought up severe environmental problems and ecological impacts. Here, we use a regional climate model, WRF-Chem, along with the offline driven Simplified Simple Biosphere Model (SSiB4) to investigate the impact of aerosol radiation effects on land biosphere carbon uptake capacity. The results show that the current aerosol loading has led to significant decrease in the incident solar radiation in China, which severely suppresses the gross primary production (GPP) and net primary production (NPP). Then, we assessed the influences of stringent emission and pollution control policies on terrestrial ecosystem carbon fluxes. By comparing the simulation results based on China’s ambitious carbon neutrality policies with the reference scenario with negligible emission control, we found that the carbon neutrality scenario with rigorous pollution control increases the incident solar radiation and thereby enhancing the carbon uptake of land biosphere. Under the current state of aerosol loading, the decrease of total amount of incident radiation dominates the suppression of terrestrial carbon uptake, while aerosol diffuse fertilization effect can only partly offset the inhibition of decreased solar radiation on plant photosynthesis. Our findings improve the understanding of the interactions between aerosol pollution and the land carbon cycle, and suggest an appreciable ecological benefit and a potential terrestrial carbon sink enhancement of stringent emission and pollution control actions.

How to cite: Li, L., Qiu, B., Huang, X., Guo, W., Miao, X., Chen, J., Ni, Y., and Tian, X.: Aerosol-induced radiation effect and the potential influence of stringent emission control on terrestrial carbon uptake in China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3775, https://doi.org/10.5194/egusphere-egu23-3775, 2023.

EGU23-3823 | ECS | Orals | BG1.3

Trait-based ozone plant sensitivity to assess global vegetation damage risks 

Yimian Ma, Xu Yue, Stephen Sitch, Nadine Unger, Johan Uddling, Lina Mercado, Cheng Gong, and Zhaozhong Feng

A major limitation in modeling global O3 vegetation damage has long been the reliance on empirical O3 sensitivity parameters derived from a limited number of species and applied at the level of plant functional types (PFTs), which ignore the large interspecific variations within the same PFT. Here, we present a major advance in large-scale assessments of O3 plant injury by linking the trait leaf mass per area (LMA) and plant O3 sensitivity in a broad and global perspective. Application of the new approach and a global LMA map in a dynamic global vegetation model reasonably represents the observed interspecific responses to O3 with a unified sensitivity parameter for all plant species. Simulations suggest a contemporary global mean reduction of 4.8% in gross primary productivity by O3, with a range of 1.1%-12.6% for varied PFTs. Hotspots with damages > 10% are found in agricultural areas in the eastern U.S., western Europe, eastern China, and India, accompanied by moderate to high levels of surface O3. Furthermore, we reveal an inherent plant sensitivity spectrum for O3 which is highly linked with plant leaf trait trade-off strategy, revealing high risks for fast-growing species with low LMA, such as crops, grasses and deciduous trees.

How to cite: Ma, Y., Yue, X., Sitch, S., Unger, N., Uddling, J., Mercado, L., Gong, C., and Feng, Z.: Trait-based ozone plant sensitivity to assess global vegetation damage risks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3823, https://doi.org/10.5194/egusphere-egu23-3823, 2023.

EGU23-5157 | Posters on site | BG1.3

Ozone damage in plants: 7 years of study in a free-air experimental facility (FO3X) 

Barbara Baesso Moura, Jacopo Manzini, Yasutomo Hoshika, and Elena Paoletti

Ozone (O3) is a toxic oxidative air pollutant with significant detrimental effects on natural vegetation and crop species. Free-air controlled exposure (FACE) facilities provide an ideal tool for O3 effect studies, producing realistic results. The O3 Free-Air Controlled Exposure (FO3X - FACE) facility, located in Sesto Fiorentino, Italy, and established in 2015, is an AnaEE (Analysis and Experimentation on Ecosystems) European research platform. The facility permits the exposure of plants to three levels of O3 concentrations (1.0, 1.5, and 2.0 times the ambient concentration, denoted as AA, x1.5AA, x2.0AA, respectively), with main environmental variables continuously monitored. Over the years, the accumulated exposure over 40 ppb hourly concentrations (AOT40) was calculated and used as an exposure-based O3 index. The stomatal conductance (gsto) model, based on the multiplicative algorithm, was used to parameterize the gsto of 12 species (7 deciduous: Oxford poplar, Quercus robur, Quercus pubescens, Sorbus aucuparia, Alnus glutinosa, Vaccinium myrtillus, I-214 poplar, and 5 evergreens: Quercus ilex, Phillyrea angustifolia, Arbutus unedo, Pinus halepensis, Pinus pinea), in order to calculate the hourly stomatal O3 flux (Fst), and thus the phytotoxic O3 dose above an hourly threshold y of uptake (y = 1, POD1) used as a flux-based O3 index. Our studies have evaluated the effect of O3 in gas exchange parameters as light-saturated photosynthesis (Asat / R2 POD1 = 0.46 vs. AOT40 = 0.20) and stomatal conductance (gsto /R2 POD1 = 0.18 vs. AOT40 = 0.18), as well as for the induction of specific visible foliar injury (VFI / R2 POD1 =0.40 vs. AOT40 = 0.32) and biomass loss (Bloss / R2 POD1 = 0.50 vs. AOT40 = 0.22). We demonstrate that species-specific flux-based O3 index POD1 is more relevant compared to the exposure-based O3 index AOT40, showing the importance of comprehending the mechanism of O3 damage to plants after the uptake through stomata. Our research has also been improving the derivation of experimentally based critical levels (CLs) for the protection of forests and crops vegetation from O3 damage.

How to cite: Baesso Moura, B., Manzini, J., Hoshika, Y., and Paoletti, E.: Ozone damage in plants: 7 years of study in a free-air experimental facility (FO3X), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5157, https://doi.org/10.5194/egusphere-egu23-5157, 2023.

EGU23-5313 | Posters on site | BG1.3

Water-food-energy nexus: Progress, challenges and prospect 

Zhihui Lin
The water- food- energy nexus (WFE) plays a key role in achieving sustainable development. In this study, we systematically analyzed the concept of the WFE nexus and review its recent progress. We found that the academic communities have not reached a unanimous understanding of the concept of the WFE nexus and research framework. The evaluation methodology of the WFE nexus presents a transition from the traditional sectoral research paradigm to the human-environment system paradigm that considers the intersection of natural science and social science. These methods can also be grouped into three categories:an evaluation based on a critical process, an evaluation based on the whole system, and a comprehensive evaluation that involves coupling the internal and external elements of the WFE nexus. A bibliometric analysis shows that the number of research papers concerning the WFE nexus increased exponentially during 2000 to 2019, and the increase was particularly significant after 2015. Environmental science, food science, and nutrition science are the three main disciplines in WFE nexus research. More important, we need to strengthen the application of geography thinking, that is, comprehensive and systematic thinking, to study the WFE nexus in the future. Based on the literature review, we found that existing research lacked a quantitative understanding of the mutual feedback among the WFE nexus and its evolution.Therefore, we suggest the following five priority areas for future research: establishing a multi-source database of the WFE nexus, revealing the mutual feedback mechanism of the WFE nexus, developing a coupling model of the WFE nexus, establishing a decision- making platform for the WFE nexus, and promoting the collaboration of multiple sectors related to the WFE nexus. This will help to achieve a synergetic sustainable development of the WFE nexus through system governance and scientific management.

How to cite: Lin, Z.: Water-food-energy nexus: Progress, challenges and prospect, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5313, https://doi.org/10.5194/egusphere-egu23-5313, 2023.

EGU23-6562 | ECS | Orals | BG1.3 | Highlight

Near Real-Time Distribution of Ozone in China from 2013 to 2020 and Agricultural Impacts 

Liangke Liu, Guannan Geng, Junting Zhong, Yuxi Liu, Qingyang Xiao, Xiaoye Zhang, and Qiang Zhang

Air pollution is one of the most important environmental problems in China. As a major air pollutant, ozone (O3) will endanger human health and terrestrial ecosystems. It is of great practical significance to obtain a continuous full-coverage dataset of ozone with high spatio-temporal resolution to conduct mechanism research from its causes, development, diffusion, impact and other aspects. In this study, a 3-stage machine learning model was developed through multiple data fusion, and the LightGBM method is used to obtain the hourly spatio-temporal distribution dataset of the O3 concentration in China from 2013 to 2020, with a resolution of 0.25 °× 0.25°. We first revise the meteorological reanalysis data using ground observation and propose a data fusion algorithm to achieve the ground level distribution of ozone, which combines ground observation of pollutants, population data, revised reanalysis meteorological conditions, reanalysis of radiation, land and vegetation data, emission inventory and results of chemical transport model simulation.  In addition, due to the common phenomenon that the previous prediction models underestimate the extreme value of the pollution periods,therefore, we redefined the heavy pollution event and assimilated it into the 0.25 grid by using the synthetic minimum oversampling technique (SMOTE) method to improve the model performance during the extreme pollution periods.

Our model, with the 10-fold CV result of R2 = 71% and RMSE= 25.1μg·m-3, and our hourly O3 concentration results are spatially and spatially continuous with a similar distribution compare to the observation, which proves the reliability of our model. With higher time resolution, various exposure response indicators can be obtained. AOT40 calculated by high-resolution hourly ozone concentration further, which is far more accurate than it when directly predicted by daily indexs modeling.

In addition, based on the distribution of AOT40, we assessed the agricultural damage and ecological damage caused by the change of surface ozone pollution during 2013-2020. Our estimation considered the planting area and phenological period of crops that the overestimation of crop RYL in the region can be avoided. The annual avrage production loss of wheat, rice and maize in China from 2013 to 2020 is 55.0, 57.4 and 23.6 Mt, respectively. Besides, The loss of gross primary productivity was also estimated. During 2013-2020, the ozone pollution in China caused an annual average loss of 2.1%, and the loss in the south was much higher than that in the north.

How to cite: Liu, L., Geng, G., Zhong, J., Liu, Y., Xiao, Q., Zhang, X., and Zhang, Q.: Near Real-Time Distribution of Ozone in China from 2013 to 2020 and Agricultural Impacts, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6562, https://doi.org/10.5194/egusphere-egu23-6562, 2023.

EGU23-7323 | ECS | Posters on site | BG1.3

A new modeling method to quantify aerosol-induced vegetation-climate biophysical feedbacks 

Yuan Zhang, Philippe Ciais, Laurent Li, and Olivier Boucher

Atmospheric aerosols can strongly affect vegetation through their cooling effect and changing diffuse radiation. The changes of vegetation further alter the climate through biophysical and biochemical feedbacks. Previous studies either investigate aerosol impacts in offline simulations to understand the vegetation response, or in fully coupled simulations to quantify the full impacts on the climate, including through atmospheric physics. So far there has been no experiment designed to separate the aerosol-induced vegetation-climate feedback from the aerosol impact itself. Existing studies on vegetation-climate feedbacks (not necessarily due to aerosol) often prescribe vegetation properties, so that the climate altered by vegetation can no longer affect the vegetation, leading to an incomplete feedback estimation. To quantify the full vegetation-climate feedback due to aerosols, we propose a new modeling framework in coupled Earth system models (ESM). In this new framework, the atmosphere module simulates the climate under both preindustrial and historical aerosol scenarios at each time step. The climates simulated under the two scenarios are both passed to the land surface module. All processes in the land surface module are separated into an organic (vegetation, part of soil) and an inorganic (energy budget, hydrology) part. The organic part is driven by the preindustrial aerosol climate, while the inorganic part is driven by the historical aerosol climate and affected by the organic part. The land surface processes provide the feedback variables for atmosphere to simulate the next time step. The feedback can be evaluated by comparing this experiment to fully coupled simulations under preindustrial and historical aerosol scenarios. Here we first introduce this framework and apply it to IPSL-CM6A-LR ESM. This new framework can have more general usages and provide opportunities to understand the land surface feedbacks in the Earth system.

How to cite: Zhang, Y., Ciais, P., Li, L., and Boucher, O.: A new modeling method to quantify aerosol-induced vegetation-climate biophysical feedbacks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7323, https://doi.org/10.5194/egusphere-egu23-7323, 2023.

EGU23-9331 | ECS | Posters on site | BG1.3

Multi-site analysis of the impact of surface ozone on European forests 

Inês Vieira, Félicien Meunier, Stephen Sitch, Flossie Brown, Giacomo Gerosa, Ivan Janssens, Pascal Boeckx, Marijn Bauters, and Hans Verbeeck

Tropospheric Ozone (O3) is a secondary pollutant with a positive radiative forcing and many negative effects on air quality, human health and ecosystems at different scales. In fact, O3 acts as a strong oxidant in plants, negatively impacting many cellular and molecular processes, such as modifying rubisco activity, reducing stomatal conductance and inducing early leaf senescence. Furthermore, when the O3 levels at the surface are high (typically above 40 ppb), these combined effects may decrease the photosynthetic carbon gains, mainly detectable at the leaf level but also important at the tree and stand scales. In this study, we intend to evaluate the effects of O3 on Gross Primary Production (GPP) at four European forest sites (Belgium, France and Italy) using local measurements, both for O3, eddy-covariance (GPP) and meteorological variables (including air temperature (TA), relative humidity (RH), vapour pressure deficit (VPD), short-wave radiation (SW), wind and precipitation). We first applied a series of statistical analyses to identify the impact of O3 and meteorological variables on GPP for each site. In a second step, we used a process-based model that simulates GPP using the Farquhar equations parameterised for each site to quantify O3-induced GPP reductions. Our results showed that the dominant meteo factor is site dependent. The SW appears to be the most important variable for predicting GPP at all sites, contrary to TA and VPD. The Belgium and Italian sites show a correlation of 0.51(0.55) for TA and 0.38(0.48) for VPD, respectively. Whereas in the French site, the TA correlation of 0.55 exceeds the VPD correlation of 0.38. Consequently, the GPP reduction varies along the different sites. This study shows the necessity of long-term monitoring datasets to understand better the O3 impacts at several ecosystems combined with process-based models.

 

How to cite: Vieira, I., Meunier, F., Sitch, S., Brown, F., Gerosa, G., Janssens, I., Boeckx, P., Bauters, M., and Verbeeck, H.: Multi-site analysis of the impact of surface ozone on European forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9331, https://doi.org/10.5194/egusphere-egu23-9331, 2023.

EGU23-10119 | ECS | Orals | BG1.3

The development and application of a mechanistic photosynthetic-stomatal conductance canopy model (DO3SE-crop) 

Pritha Pande, Sam Bland, Nathan Booth, Jo Cook, and Lisa Emberson

The impact of elevated ozone concentration on crop yield, like wheat, plays a significant role yet is poorly studied in Asian countries like China and India. We have developed, calibrated, and tested a mechanistic photosynthetic-stomatal conductance canopy model (DO3SE-crop) with an integrated ozone module (Anet-gsto+O3) for the region of Xiaoji, China. The key component of the model development involves phenology, leaf scale processes, leaf-to-canopy upscaling, and carbon allocation. The calibrated model for Xiaoji simulated the difference in yield losses for ambient and elevated ozone treatments for the years 2008 for four cultivars (Y2, Y15, Y16, Y19), ranging from 21-24%, compared with the observed dataset, giving R2 of 0.74 and RMSE of 0.003. The model was tested for 2009 and gave yield losses of 24-27%, with R2 of 0.60 and RMSE of 0.12, against the observed dataset. Further, our findings suggest that the difference in yield loss is due to the early decline in carbon assimilation in elevated treatment.This happens because of the early senescence in elevated treatment, which brings leaf senescence forward by 9-11 days.

How to cite: Pande, P., Bland, S., Booth, N., Cook, J., and Emberson, L.: The development and application of a mechanistic photosynthetic-stomatal conductance canopy model (DO3SE-crop), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10119, https://doi.org/10.5194/egusphere-egu23-10119, 2023.

EGU23-12046 | ECS | Orals | BG1.3

Can the atmospheric aerosol impact on the functioning of a peatland? 

Kamila Harenda, Krzysztof Markowicz, Patryk Poczta, Iwona Stachlewska, Jędrzej Bojanowski, Bartosz Czernecki, Alasdair Mac Arthur, Dirk Schüttemeyer, and Bogdan Chojnicki

The productivity of terrestrial ecosystems is determined, among other things, by solar radiation and its degree of scattering can increase or reduce it. The intensity of scattering is determined by the optical properties of the atmosphere due to the presence of particles suspended in the atmosphere, i.e. clouds and aerosols. Additionally, the amount of these substances and also the physical properties affect the radiation transfer and thus the plants ability of CO2 absorption. In the presented research, an attempt to quantify the impact of the different types of aerosols presence in the atmosphere on the amount of gross ecosystem production (GEP) in a transitional peatland in northwestern Poland was made. Three classes of cloudiness were assumed in the simulations: cloudless, medium and full cloud conditions, and an atmosphere-ecosystem model was used to assess the peatland productivity under these conditions. It was found that changes in the physical parameters of aerosols in the atmosphere can both increase and decrease the amount of CO2 uptake by peatlands by up to 8.2% and 6%, respectively. Thus, the research is extremely relevant to the global carbon balance, as peatlands are one of the largest reservoirs of organic carbon in the biosphere.

How to cite: Harenda, K., Markowicz, K., Poczta, P., Stachlewska, I., Bojanowski, J., Czernecki, B., Mac Arthur, A., Schüttemeyer, D., and Chojnicki, B.: Can the atmospheric aerosol impact on the functioning of a peatland?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12046, https://doi.org/10.5194/egusphere-egu23-12046, 2023.

EGU23-12811 | Orals | BG1.3

Towards a better understanding of the physical risks and tradeoffs of solar geoengineering. 

Matthew Henry, Jim Haywood, and Andy Jones

Solar climate intervention using Stratospheric Aerosol Injection (SAI) is a proposed method of reducing global-mean temperatures to temporarily offset some of the effects of global warming while we cut greenhouse gas emissions and remove CO2 from the atmosphere. While the scientific, moral, and ethical questions surrounding solar geoengineering are undoubtedly complex, rigorous and unbiased information on its advantages and pitfalls will help us make better decisions in the future. Recent research has shown that some of the negative physical side-effects of SAI can be moderated by designing a better intervention strategy. I will present a comparison between a previously published ensemble of climate model simulations using the Community Earth System Model 2 (CESM2) and a new ensemble using the United Kingdom Earth System Model 1 (UKESM1). This set of simulations is based on a moderate greenhouse gas emission scenario and start injection of stratospheric aerosols in year 2035 to keep the global-mean surface temperature at 1.5 degrees above preindustrial. The injection occurs at four different latitudes and a controller algorithm is used to maintain the latitudinal gradient and inter-hemispheric difference in surface temperature, thus moderating the side effects of previous injection methods. We compare the behavior of the algorithm between the two models, as well as the climate response, with a particular focus on tropical precipitation.

How to cite: Henry, M., Haywood, J., and Jones, A.: Towards a better understanding of the physical risks and tradeoffs of solar geoengineering., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12811, https://doi.org/10.5194/egusphere-egu23-12811, 2023.

EGU23-14543 | Posters on site | BG1.3

Characterizing the O3 yield gap in the sugarcane production of SE Brazil 

Alexander Cheesman, Flossie Brown, Rafael Ribero, Gerd Folberth, Felicity Hayes, Barbara Moura, Elena Paoletti, Yasutomo Hoshika, Lucas Cernusak, Colin Osborne, and Stephen Sitch

Sugarcane a vitally important crop across many tropical and subtropical regions. São Paulo (SP) state, Brazil the largest single regional producer of both raw sugar and the production of bioethanol has experienced large-scale conversion of pasture to sugarcane production in recent decades. This predominantly rain-fed agricultural area is exposed to seasonal drought and periodic high tropospheric ozone (O3) pollution at levels known elsewhere to be detrimental to plant productivity. Given the large current extent, and planned expansion of sugarcane production to meet global demand for ‘green’ biofuels there is a pressing need to characterize the risk of current tropospheric O3 to the sugarcane industry. This is a key step towards limiting the O3 yield gap under future climate and land use change scenarios. In this study, we therefore sought to a) derive realistic sugarcane O3 dose response functions across a full range of O3 exposure and b) model the implications of this observed O3 response across the globally important production area of SE Brazil.

We found a significant and substantial impact of O3 on a range of sugarcane cultivars, including a number of commercially relevant varieties. When combined with biologically relevant predictions of O3 exposure across Brazil this allows us to predict the current regional impact of O3 on sugarcane production. We find that up to 25 million tonnes of total crop productivity a year may be lost across São Paulo alone due to the direct impacts of O3 exposure – but that substantial differences in O3 sensitivity of different cultivars highlights the need for future work to elucidate the true impacts of O3 in this important tropical cropping system.

How to cite: Cheesman, A., Brown, F., Ribero, R., Folberth, G., Hayes, F., Moura, B., Paoletti, E., Hoshika, Y., Cernusak, L., Osborne, C., and Sitch, S.: Characterizing the O3 yield gap in the sugarcane production of SE Brazil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14543, https://doi.org/10.5194/egusphere-egu23-14543, 2023.

EGU23-15314 | ECS | Posters on site | BG1.3

Interannual variability in ozone damage to tropical forests 

Flossie Brown, Stephen Sitch, Gerd Folberth, and Alexander W. Cheesman

Fire emissions include the ozone precursor NOx, which is often the limiting precursor in remote locations such as the tropical forests. In fact, interannual variability in tropical fire activity, which depends on meteorology and human activity, is highly correlated with variability in surface ozone concentration over the tropics. Additionally, drought years in Asia and South America show consistently higher fire activity and surface ozone concentrations compared to years without droughts. Since surface ozone is known to decrease plant productivity, higher ozone concentrations during drought events may reduce strength of the land carbon sink. On the other hand, drought events may protect plants from ozone damage by causing a decrease in stomatal conductance. Thus, the net impact will be the balance of these opposing effects, and will likely vary by region. As climate change may increase the frequency of drought events in the tropics, an understanding of present-day relationships between drought events, fire activity and surface ozone concentrations will help inform of current and future risks of plant-ozone damage in the tropics.

Using climate model predictions of surface ozone concentration from 1996 – 2015, we show that annual mean ozone concentrations over the Amazon are up to 10 ppb higher during drought years compared to years without drought due to variability in fire activity. We then use a land surface model to show that net primary productivity loss due to plant-ozone damage in the Amazon is largest during drought years at the basin scale. The majority of the productivity loss occurs around the arc of deforestation in the Southern Hemisphere, whereas a reduction in stomatal conductance protects the Northern Hemisphere Amazon from ozone damage during drought years. Given that the interannual variability in carbon lost from plant-ozone damage is predicted to be of similar magnitude to that from direct fire emission (~ 200 Tg C), we highlight a need to consider plant sensitivity to ozone, especially for agriculture and secondary forests in the arc of deforestation. 

How to cite: Brown, F., Sitch, S., Folberth, G., and Cheesman, A. W.: Interannual variability in ozone damage to tropical forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15314, https://doi.org/10.5194/egusphere-egu23-15314, 2023.

EGU23-15707 | Orals | BG1.3 | Highlight

Ozone impacts on tropical forest productivity 

Stephen Sitch, Alexander W Cheesman, Flossie Brown, Paulo Artaxo, Lucas A Cernusak, Gerd Folberth, Felicity Hayes, Tim Hill, Lina Mercado, and Johan Uddling

Tropospheric ozone (O3) reduces plant productivity by entering leaves, generating reactive oxygen species and causing oxidative stress which in turn increases respiration, decreases photosynthesis, plant growth, biomass accumulation, and consequently reduces the land carbon sink. Tropical forests are potentially most vulnerable to future O3 scenarios given their high productivity, generally high stomatal conductance and environmental conditions conducive to O3 uptake (eg precursor emissions during biomass burning).

Here we present the first comprehensive set of measurements of O3 effects on plant physiology and biomass accumulation in tropical forests. We exposed twelve tropical tree species to elevated O3 concentrations in Open Top Chambers (OTCs) based at the James Cook University O3 experimental facility in Cairns, Australia, from which we generate O3 dose-response functions for each species. We test the importance of Leaf Mass per unit Area (LMA) as an indicator of O3 sensitivity.

We use these relationships to parameterize the global land-surface model JULES, and apply the model over the pan-tropical region using contemporary near-surface O3 concentration fields. For the first time we quantify the impact of O3 on contemporary tropical productivity.

How to cite: Sitch, S., Cheesman, A. W., Brown, F., Artaxo, P., Cernusak, L. A., Folberth, G., Hayes, F., Hill, T., Mercado, L., and Uddling, J.: Ozone impacts on tropical forest productivity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15707, https://doi.org/10.5194/egusphere-egu23-15707, 2023.

EGU23-17057 | ECS | Orals | BG1.3 | Highlight

Marine cloud brightening, could it mitigate coral bleaching on the Great Barrier Reef? 

Daniel Harrison

For over 30 years scientists and engineers have theoretically pondered whether it was possible to mitigate global warming by atomising seawater over the ocean in a bid to favourably manipulate aerosol-cloud-radiation processes. Given the current plight of the coral ecosystem of the Great Barrier Reef, marine cloud brightening is under considereation as a regional strategy to reduce environmental stress on coral reefs during marine heatwaves. Atmospheric, biogeochemical and ecological modelling suggest that the potential exists to reduce light and thermal stress during marine heatwaves causing coral bleaching. Results from recent field campaigns, the first to empirically test the concept of marine cloud brightening, support the foundational assumptions. From its inception the research program has involved consultation and participation of indigenous traditional custodians of the reef and has proceeded within the regulatory oversight of one of the world’s most actively managed marine estates. This talk will give an overview of the Australian research program including the scientific basis which underpins it and a summary of the most recent results and future directions.

How to cite: Harrison, D.: Marine cloud brightening, could it mitigate coral bleaching on the Great Barrier Reef?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17057, https://doi.org/10.5194/egusphere-egu23-17057, 2023.

Both the quantity and quality of radiation could be altered by aerosols and cloud, and thus changing ecosystem carbon and water fluxes, as well as their coupling relationship. Although the importance of radiation quantity to ecosystems has been well studied, how radiation quality (characterized by diffuse radiation fraction, the proportion of diffuse to total radiation, Kd) affects ecosystem carbon and water cycles remains unclear due to the lack of diffuse radiation observations. In this work, taking advantage of a newly derived Kd dataset, we comprehensively explored the impact of Kd on ecosystem carbon uptake (net ecosystem exchange, NEE), carbon flux (gross primary production, GPP), water flux (evapotranspiration, ET), and water-use efficiency (GPP/ET, WUE) based on measurements at 201 global FLUXNET sites. We found that diffuse radiation is more efficient to improve NEE, GPP and ET than direct radiation at the same radiation level for all vegetation types, leading to increased ecosystem carbon uptake and water loss with Kd at the low and middle Kd levels. Furthermore, the enhancement of GPP is stronger than ET, leading to improved ecosystem WUE by diffuse radiation. By separating radiation into diffuse and direct components, we found that diffuse radiation is the most important factor for GPP, while ET is more dominated by direct radiation, indicating the complex process underlying the response of WUE to changes in Kd. This research helps improve our understandings of the responses of ecosystem carbon and water cycle to aerosol/cloud changes.

How to cite: Wang, B. and Yue, X.: Relationships between radiation quality and ecosystem carbon and water fluxes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17190, https://doi.org/10.5194/egusphere-egu23-17190, 2023.

EGU23-17374 | Orals | BG1.3

Understanding the combined effects of ozone pollution and climate change on crop yield and nutritional quality 

Lisa Emberson, Sam Bland, Pritha Pande, Jo Cook, Nathan Booth, and Divya Pandey

Ozone pollution and climate change are extremely likely to threaten future crop production in important agricultural regions around the World with the Mediterranean, South and East Asia and mid-West US being particularly at risk with implications for food security. Modelling methods used to assess risk of ozone pollution have developed in recent years away from empirical approaches based on dose-response relationships towards more process-based models. The DO3SE-Crop model has developed from an ozone deposition and effects model (having used flux-response relationships to assess damage) to a crop model capable of assessing the effect of ozone on photosynthesis and carbon allocation. Working within the AgMIP-ozone activity, DO3SE-Crop has been calibrated and evaluated against experimental ozone fumigation datasets for wheat cultivars from Spain (Mediterranean Europe), China and India and is able to assess the influence of climate variables on crop growth and yield as well as the effect of ozone on instantaneous photosynthesis and senescence. We find that the ozone effect on senescence is the primary determinant for yield loss in wheat. We are further developing the model to assess ozone effects on nutritional quality since we know that ozone is an important limiter of translocation of nitrogen to the grains. The establishment of DO3SE-Crop will allow assessments of the future impacts resulting form the combined effects of ozone and climate change on supply and nutritional aspects of food security. Importantly, this can include an assessment of the yield improvements between current and near- to mid-term future conditions for a range of adaptation options proposed for wheat in response to climate change including management of irrigation, growing season and development of new varieties from crop breeding with targeted physiological traits such as enhanced gas exchange and improved water use efficiency.

How to cite: Emberson, L., Bland, S., Pande, P., Cook, J., Booth, N., and Pandey, D.: Understanding the combined effects of ozone pollution and climate change on crop yield and nutritional quality, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17374, https://doi.org/10.5194/egusphere-egu23-17374, 2023.

Moisture is a key factor governing soil nitrogen (N) biogeochemistry; it controls microbial activity and, therefore, the cycling of N. Ongoing climate change is altering precipitation regimes, increasing the frequency and intensity of droughts with implications for ecosystem N retention and loss. In particular, wetting dry soils can produce large emission pulses of nitrous oxide (N2O), a potent greenhouse gas, but the mechanisms governing the N losses remain elusive. Especially because denitrification, arguably the most important process producing N2O, is thermodynamically unfavorable in dry soils. Disentangling how drought can alter the balance between ecosystem N retention and loss is further challenged by the multiple biotic and abiotic processes that interact to control N availability and emissions, requiring multiple analytical approaches.

 

To advance understanding of N cycling in dry soils, we studied drylands in southern California that can experience >6 months without rain and whose contrasting soils developing under shrub canopies (soils known as “islands of fertility”), or in the bare interspaces between shrubs, allow us to interrogate biotic–abiotic interactions. Using isotopologues of N2O coupled with chloroform fumigations to slow microbial activity, we found that N retention and loss trade off as dry conditions intensify. In particular, N2O emissions were undetectable from soils in the interspaces between plants, but exceeded 1000 ng N-N2O m-1 s-1 in islands of fertility, rivaling emissions observed in global hotspots like tropical forests and temperate agroecosystems. Despite the hot and dry conditions, isotope tracers and natural abundance isotopologues of N2O indicated NO3- was reduced to N2O within 15 minutes of wetting dry desert soils, and that both denitrification and N2O reduction to N2 contributed to the observed patterns, with δ15NSP-N2O values averaging 12.8 ± 3.9 ‰. Consistent with isotope values, fumigating soils in the lab with chloroform decreased NO3--derived N2O emissions by 59%, suggesting denitrifiers were able to reduce NO3- immediately after wetting these summer-dry desert soils. In contrast to NO3-, the 15N-NH4+ tracer was not found in N2O, suggesting nitrification is not an important pathway governing N2O emissions in these systems. Despite the hot and dry conditions known to make denitrification thermodynamically unfavorable in many drylands, denitrifiers can endure through hot and dry summers and are key to producing the surprisingly large N2O emissions when dry desert soils wet up.

How to cite: Homyak, P.: Denitrification in dry soils: Unexpected N emissions under environmental extremes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2124, https://doi.org/10.5194/egusphere-egu23-2124, 2023.

EGU23-2623 | Posters on site | BG1.4

Which N2O production processes are relevant when converting from grassland to cropland? 

Caroline Buchen-Tschiskale, Dominika Lewicka-Szczebak, Greta Nicolay, Mirjam Helfrich, Heinz Flessa, and Reinhard Well

During the last decades, large areas of grassland were converted to cropland across Europe, mainly due to the increasing demand of cropland following the expansion of biogas plant production (e.g. maize). However, the conversion to cropland bears a risk of nitrous oxide (N2O) emission due to enhanced nitrogen (N) mineralization. Until now, knowledge about N2O production pathways due to grassland conversion and in particular N2O reduction to N2 is very limited (Buchen et al., 2018), even though understanding of N2O processes and identification of sources are needed in order to devise mitigation options.

N2O samples were collected periodically from manual chambers following chemical and mechanical conversion from permanent grassland to cropland (maize) at two sites with different texture (clayey loam and sandy loam) and fertilization regime (with and without mineral N-fertilization) in north-western Germany (Helfrich et al., 2020). Samples were analysed for natural abundance stable isotope signatures of soil-emitted N2O (δ15NbulkN2O, δ18ON2O and δ15NSPN2O = intramolecular distribution of 15N in the N2O molecule) by isotope ratio mass spectrometry (IRMS) and dual-isotope of N2O isotopic signatures (plotting δ15NSPN2O vs. δ18ON2O) were used for data evaluation (Lewicka-Szczebak et al., 2017). Although, isotopic signatures were very variable throughout the year at both sites, the clayey loam site exhibited a close correlation between δ15NspN2O and δ18ON2O suggesting that values were mainly controlled by N2O reduction to N2. At the sandy loam site this pattern was less pronounced, possibly because processes other than bacterial denitrification (e.g. fungal denitrification and nitrification) also significantly influence isotopocule values. Altogether, bacterial denitrification was found to be the most important process following grassland conversion to maize cropping.

References:

Buchen, C., Lewicka‐Szczebak, D., Flessa, H., Well, R., 2018. Estimating N2O processes during grassland renewal and grassland conversion to maize cropping using N2O isotopocules. Rapid Communications in Mass Spectrometry 32, 1053-1067.

Helfrich, M., Nicolay, G., Well, R., Buchen-Tschiskale, C., Dechow, R., Fuß, R., Gensior, A., Paulsen, H., Berendonk, C., Flessa, H., 2020. Effect of chemical and mechanical grassland conversion to cropland on soil mineral N dynamics and N2O emission. Agriculture, Ecosystems & Environment 298, 106975.

Lewicka-Szczebak, D., Augustin, J., Giesemann, A., Well, R., 2017. Quantifying N2O reduction to N2 based on N2O isotopocules – validation with independent methods (helium incubation and 15N gas flux method). Biogeosciences 14, 711-732.

How to cite: Buchen-Tschiskale, C., Lewicka-Szczebak, D., Nicolay, G., Helfrich, M., Flessa, H., and Well, R.: Which N2O production processes are relevant when converting from grassland to cropland?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2623, https://doi.org/10.5194/egusphere-egu23-2623, 2023.

EGU23-3413 | Posters on site | BG1.4 | Highlight

Hot-spots of denitrification in soil depending on crop residue and liquid manure incorporation – models and experiments 

Reinhard Well, Rene Dechow, and Balazs Grosz

Soil denitrification is known to be affected by incorporation of crop residues due to supply of reductants and oxygen (O2) consumption by decomposition. The formation of anoxic microsites where denitrification can occur thus depends on quality, particle size and spatial distribution of incorporated residues in interaction with physical and chemical soil properties. Current biogeochemical models typically assume homogeneity of soil layers and thus don’t consider the size and distribution of crop residue particles. Until now, dinitrogen (N2) and nitrous oxide (N2O) fluxes related to residue incorporation patterns have been rarely studied and are poorly represented by current models. Here we present synergetic concepts and results of two projects addressing the spatial modelling of anoxic hot-spots („Modeling the impact of liquid organic fertilization and associated application techniques on N2O and N2 emissions from agricultural soils”, MOFANE) and measures to mitigate denitrification in soil („Measures to reduce direct and indirect climate-impacting emissions caused by denitrification in agriculturally used soils”, MinDen).

To test the incorporation of harvest residues and catch crops on denitrification, a full-factorial laboratory incubation will be carried out in MinDen, assessing incorporation methods and pre-crushing of catch crops, and how these interact with soil type and water content.

 

Based on a static model to take into account spatial hot-spots induced by liquid manure (Baral et al., 2016)  a dynamic model was developed in MOFANE and tested using lab experiments (Grosz et al., 2022). This model can also be applied to evaluate the aforementioned crop residue effects.

We present a conceptual model of denitrification in dependence of size and distribution of crop residues, soil type, soil moisture and soil structure. It predicts that pre-shredding and homogenous incorporation favours denitrification at low gas diffusivity given by high moisture and/or high clay content or bulk density, since small organic hot-spots suffice to create anoxia. For high gas diffusivity (e.g. due to sandy texture and/or dry conditions) it predicts that denitrification is favoured if incorporated crop residues are large, since anoxic microsites can only develop if the size of organic hot-spots is large enough so that the O2 sink strength exceeds O2 diffusion from the atmosphere.

Scenarios of the conceptual model will be tested using the dynamic hot-spot model and results will be presented.

 

Baral, K.R., Arthur, E., Olesen, J.E., Petersen, S.O., 2016. Predicting nitrous oxide emissions from manure properties and soil moisture: An incubation experiment. Soil Biology & Biochemistry 97, 112-120.

Grosz, B., Kemmann, B., Burkart, S., Petersen, S.O., Well, R., 2022. Understanding the Impact of Liquid Organic Fertilisation and Associated Application Techniques on N2, N2O and CO2 Fluxes from Agricultural Soils. Agriculture 12, 692.

How to cite: Well, R., Dechow, R., and Grosz, B.: Hot-spots of denitrification in soil depending on crop residue and liquid manure incorporation – models and experiments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3413, https://doi.org/10.5194/egusphere-egu23-3413, 2023.

EGU General Assembly 2023

23-28 April 2023

 

THE EFFECT OF FERTILISATION AND CROPS ON NITROGEN SEQUESTRATION BASED ON MICROBIAL ANALYSIS AND N2O EMISSIONS

Laura Kuusemets1, Ülo Mander1, Jordi Escuer Gatius2, Alar Astover 2, Mikk Espenberg1

1 University of Tartu, Institute of Ecology and Earth Sciences, Vanemuise 46, 51014 Tartu, Estonia

2 Estonian University of Life Sciences, Institute of Agricultural and Environmental Sciences, Kreutzwaldi 5, 51014 Tartu, Estonia

Contact: laura.kuusemets@ut.ee

 

Nitrogen (N) is an essential nutrient in crop production as N is used to make amino acids (make the proteins that construct cells), is one of the building blocks for DNA, and is a significant component of chlorophyll (photosynthesis). The input of N in the form of fertilisers increases crop yield. On the other hand, agricultural nitrogen inputs can cause N leaching and the loss of biologically active N to the atmosphere, contributing to global warming. Thus, excessive and inefficient use of N fertiliser results in enhanced crop production costs and pollution of water bodies and the atmosphere. Agricultural landscapes are an important source of nitrous oxide (N2O), a highly active greenhouse gas and stratospheric ozone depleter. The main objectives of the study were to evaluate whether and how different crop species and fertilisation norms affect nitrous oxide (N2O) emissions and soil microbiome using the closed chamber method and quantitative polymerase chain reaction (qPCR) analysis.

The study was done in the IOSDV (International Organic Nitrogen Long-term Fertilisation Experiment) experimental field located in the southern part of Estonia. The crop species studied were barley (cultivar “Elmeri”), sorgo (cultivar “Susu”), and wheat (cultivar “Mistral”). The fertiliser treatment is constituted of mineral nitrogen fertilisation and fertilisation with farmyard manure. Three nitrogen fertiliser treatment rates were used: 0, 80 and 160 kg ha−1. Samples were collected over seven months, from April 2022 to October 2022. qPCR was used to quantify the abundance of bacteria- and archaea-specific 16S rRNA, nitrification (bacterial, archaeal and comammox (complete ammonia oxidation) amoA) denitrification (nirK, nirS, nosZI and nosZII) and dissimilatory nitrate reduction to ammonium (DNRA; nrfA gene) marker genes from the soil samples.

The results of this study indicate that different fertilisation influence N2O emissions and the highest N2O emissions are emitted from the highest N fertilizer treatment (160 kg ha−1). On average, sorgo fields fertilised with farmyard manure had slightly higher N2O emissions compared to fertilisation with mineral fertiliser. In addition, on average, the highest and smallest N2O emissions occurred with wheat and barley, respectively. The N2O emissions among all crop species decreased during drought in the summer. The preliminary microbial analysis shows that nitrification was the primary process resulting in N2O emissions, but the different groups of nitrifiers showed different trends under different fertilisation and crops.

 

How to cite: Kuusemets, L.: The effect of fertilisation and crops on nitrogen sequestration based on microbial analysis and N2O emissions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4359, https://doi.org/10.5194/egusphere-egu23-4359, 2023.

Ammonia oxidation contributes to global N2O emissions both by direct production and by fueling denitrification (provision of nitrite or nitrate to denitrifiers). Urea or ammonia-based fertilizers account for approximately 70% of annual nitrogen fertilizer inputs globally. This means that the subsequent coupling processes driven by ammonia oxidation are of great significance to N2O emissions. However, for this important source of N2O production, direct evidence at the process- and microorganism- level is highly lacking, leading to that the systematic mechanism of the coupling processes and microbial activities in response to environmental changes (especially O2 changes) remains unknown. Here, we investigated ammonia oxidation, other soil N transformation processes, N2O emissions and related environmental changes (e.g., O2 consumption) and microbial activities in a calcareous upland soil in Northern China, which has a strong ammonia oxidizing rate and is a global N2O hotspot, by combining field observations, microcosm, molecular and isotope techniques. The results showed that the soil has a far (5-30 times) higher nitrification potential and gross nitrification rate than other cropland soils in the world. The strong ammonia oxidation led to rapid O2 consumption and NO2- accumulation in soil matrix, causing strong emission peaks of N2O, which was in line with the N2O yield from denitrifiers. The N2O 15N site preference and 15N labeling data further revealed a major role of nitrification-induced denitrification in high N2O emissions. A higher AOB/AOA gene abundance ratio correlated the higher nitrification potential, higher NO2- transition and higher N2O emissions. A coupling expression of nitrifying and denitrifying genes (amoA, narG, nirS, nirK, nosZ) and a significant structural alteration of the soil microbiota along with the O2 consumption driven by ammonia oxidation linked to higher N2O emissions. All the evidence points to ammonia oxidation-linked denitrification being the major process generating N2O. In consequence, reducing N surplus, slowing down nitrification rate using nitrification inhibitors, and avoiding high ammonium microzones using slow-release or organic fertilizers are main measures to reduce N2O emissions per unit of urea or NH4+-based N input in intensively managed alkaline soils globally.

How to cite: Ju, X. and Song, X.: Ammonia oxidation as the engine to induce denitrification to produce N2O in alkaline agricultural soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4780, https://doi.org/10.5194/egusphere-egu23-4780, 2023.

EGU23-4849 | ECS | Orals | BG1.4 | Highlight

Importance of in-situ measurements of both N2O and N2 emissions to calibration of biogeochemical models to simulate N budgets 

Naoya Takeda, Johannes Friedl, David Rowlings, Clemens Scheer, Edwin Haas, David Kraus, and Peter Grace

Denitrification is a key process in the global nitrogen (N) cycle, causing nitrous oxide (N2O) and dinitrogen (N2) emissions. Even though denitrification is assumed to be a major N loss pathway from agroecosystems, field-scale estimates of both N2O and N2 are scarce, reflecting methodological difficulties in measuring and upscaling N2 emissions. Mechanistic biogeochemical models allow estimates of seasonal denitrification losses at the field scale, extrapolating important yet often limited experimental results. However, such predictions rely mostly on N2O data, meaning that the lack of N2 data hinders the validation of overall denitrification rates, which remain a major uncertainty for N budgets.

This study investigated denitrification losses and N budgets in two subtropical sugarcane systems using Agricultural Production Systems sIMulator (APSIM) with unique datasets of both N2O and N2 emissions measured in the field with the 15N gas flux method and upscaled over the growing season. Five key soil N parameters in APSIM were identified as influential on N2O and N2 emissions via global sensitivity analysis, followed by generalised likelihood uncertainty estimation to determine their posterior distributions using (i) both N2O and N2 data and (ii) N2O data only.

For both approaches, the calibration of APSIM led to larger denitrification (N2O+N2) losses and a shift towards N2 compared to the use of default parameters. Simulated N2O emissions did not differ between the different calibration approaches. However, simulated N2 emissions were larger and agreed better with the observed values when calibrated with both N2O and N2 consistently across sites. This approach also improved the simulation of fertiliser N losses via denitrification, leaching and runoff, compared to the observed fertiliser 15N loss at harvest.

These findings indicate that biogeochemical models commonly used with default soil N parameters or calibration limited to N2O data are likely to underestimate denitrification losses, producing a bias in simulations of N budgets. Our findings also highlight the importance to integrate in-situ measurements of N2O and N2 in simulation exercises, and demonstrate how innovative isotope methods can be used to inform biogeochemical models, ensuring more accurate N budget estimates across scales.

How to cite: Takeda, N., Friedl, J., Rowlings, D., Scheer, C., Haas, E., Kraus, D., and Grace, P.: Importance of in-situ measurements of both N2O and N2 emissions to calibration of biogeochemical models to simulate N budgets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4849, https://doi.org/10.5194/egusphere-egu23-4849, 2023.

EGU23-5282 | Posters on site | BG1.4

Shifting China’s rice fields from nitrogen source to sink by innovative agricultural management 

Weichen Huang, Wenjun Jiang, and Feng Zhou

Rice field has been traditionally considered as a nonpoint source of reactive nitrogen (N) for the environment, while it, with surrounding ditches and ponds, also contributes to receiving N inputs from atmosphere and waterbodies and intercepting N outputs from rice field. However, due to the paucity of multi-site, long-term observation and control experiment data, as well as robust process-based model for nitrogen budget, a comprehensive assessment of the N source (i.e., outputs > inputs) or sink (i.e., inputs > outputs) of rice field for the environment, from site to regional scale, is lacking. Here, a 2-year systematic observation and process-based simulations of N budget across China, covering typical annual rice cropping systems including single rice, double rice and rotation, were conducted to identify the roles of rice field in nitrogen cycling in China. The cost-benefit analysis for shifting China’s rice fields from nitrogen source to sink in different climatic scenarios (wet, normal and dry year) by innovative agricultural management, without compromising crop yield or soil fertility, were further evaluated. Rice fields, with surrounding ditches and ponds, perform as a nitrogen sink for atmosphere but a source for waterbody, which was confirmed by both the observational data and regional assessment by process-based model, regardless of rice types or climatic scenarios. With the adoption of sustainable N and water regulation measures, single rice field across China could be shifted to N sink (12.9-29.9 kg N ha-1) while the N source of double rice would be reduced by 51%-66%. For middle rice field (rotation with other crops), N sink would be achieved in dry year, while 31%-55% would shift to sink in wet and normal year. However, with such great benefits, the costs only accounted for 41%-49% of the expenditure for waste water treatment. Furthermore, through sorting all the measures and adopting economic ones (lower cost with higher benefit) in priority, we found that rice fields across China have great space for source-to-sink regulation with zero cost, which means the benefits would exceed the regulation costs, and even achieve overall N sink in dry year. Together these findings help us to update scientific knowledge to the role of rice fields in ecosystems, as well as highlight the significance and possibility for achieving environmental-friendly rice field, by improving agricultural management technologies.

How to cite: Huang, W., Jiang, W., and Zhou, F.: Shifting China’s rice fields from nitrogen source to sink by innovative agricultural management, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5282, https://doi.org/10.5194/egusphere-egu23-5282, 2023.

EGU23-5324 | ECS | Posters on site | BG1.4

Low-cost in-field determination of soil ion concentration using a portable 3D printed device based on ion-selective electrodes and textile threads 

Ernesto Saiz, Yafei Guo, Sami Ullah, Sameer Sonkusale, and Aleksandar Radu

Population keeps growing so as the need for food production. The increase in energy prices is putting a lot of pressure in energy intensive industrial processes such as the production of fertilizers. Farmers need to fine-tune the amount of fertilizer needed by the soil, so that they do not add in excess, elevating costs and polluting the environment, or do not fall short, suffering sub-optimal crop yields.

This work reports the fabrication and characterization of a low-cost device for the continuous monitoring of the concentration of plant nutrients based on ion-selective electrodes and textile threads that work in direct contact with soils. Here, as proof of concept, we developed a thread-based, microfluidic sensor platform. We utilized traditional polymer membrane-based ion-selective electrodes (ISEs) for potassium, nitrate, ammonium and pH were drop-casted directly on top of a miniaturized, 3D-printed holder. Electrical contact is established via graphite-based contacts link to the electrochemical signal reader via electrical wires. The sensor platform was enhanced by the addition of five 30 cm long textile threads connected to an absorption pad on the opposite side. This is the key innovation as these threads mimic the roots and via capillary action wick the moisture from the soil to the sensing area. The entire sensor platform contained 4 ISEs for each chemical species and one reference electrode and was encased into a 3D printed housing. The device is placed next to the soil that is going to be analysed inserting the threads in the soil sampling area.

Preliminary results show that thread-based sensor system is reproducible and consistently provides a near-Nernstian sensitivity of 55±5 and 50±3 for potassium, -58±1 and -63±2 for nitrate, and 60±1 and 60±12 (mV/decade) for ammonium between 2.8x10-6 and 1.3x10-2 M without (directly in solution) and with textile threads respectively. Analysis of soil samples with different soil moisture content (100%, 75%, 50% and 40%) using our low cost device gave a correlation coefficient of R2 = 0.91 for potassium and R2 = 0.92 for ammonium when compared to the values measured using traditional methods such as inductively coupled plasma optical emission spectroscopy (ICP-OES) and flow injection analysis (FIA), respectively. The promising performance of this low-cost device is encouraging towards its use as an extended network to measure soil ion concentration at high temporal and spatial resolution.

How to cite: Saiz, E., Guo, Y., Ullah, S., Sonkusale, S., and Radu, A.: Low-cost in-field determination of soil ion concentration using a portable 3D printed device based on ion-selective electrodes and textile threads, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5324, https://doi.org/10.5194/egusphere-egu23-5324, 2023.

EGU23-5440 | ECS | Posters on site | BG1.4

Microbial and environmental factors affecting nitrate removal in bio-electrochemical systems (BES) 

Sharvari Sunil Gadegaonkar, Ülo Mander, and Mikk Espenberg

Excess nitrogen has caused environmental issues by polluting the air and water. Many different processes help remove nitrogen compounds from contaminated soils and waters, and the presence of oxygen is one of the most decisive factors. Denitrification in anaerobic conditions is considered the main removal processes of excessive nitrogen, although lately discovered anaerobic ammonium oxidation (ANAMMOX) and dissimilatory nitrate reduction to ammonium (DNRA) may also have an important role in nitrogen elimination of different systems. To a lesser extent, also nitrification can contribute to nitrogen elimination in watery systems. All previously pointed out removal mechanisms occur in the constructed wetlands and could even be enhanced with the bio-electrochemical systems (BES). BES exploit the ability of the electroactive microorganisms to reduce the oxides of nitrogen.

We analyzed various articles treating nitrate (NO3) polluted water in BES and normalized their NO3 removal efficiencies to a common unit (mg liter−1 day−1). We analyzed the effect of various factors such as electrode materials, working mode, type of inoculum, number of chambers, systems’ capacity and the microbial community structure on the NO3 removal efficiencies. The highest removal efficiencies were displayed by granular carbon and carbon cloth used as cathode and anode material, respectively. The electrode materials and operational parameters, such as working mode and number of chambers, were deemed important by the random forest classification algorithm. Continuous mode of operation, denitrifying microbes as inoculum type, and two chamber systems have displayed optimum NO3 removal efficiencies. Feature selection using random forest classification showed the type of inoculum and capacity of the BES were unimportant factors. Proteobacteria and Firmicute were the prominent phyla observed in BES treating NO3 polluted water. Besides the denitrification (abundance of narG, nirS, nirK, nosZI, and nosZII genes) process in BES, there is evidence of electrochemical support for anaerobic ammonium oxidation (ANAMMOX) (abundance of hzsB or ANAMMOX specific 16S rRNA gene) and dissimilatory NO3 reduction to ammonium (DNRA) (abundance of nrfA gene) processes. The results of this work aid in understanding the prevalent processes in the BES and help to build efficient BES for optimum NO3 removal.

How to cite: Gadegaonkar, S. S., Mander, Ü., and Espenberg, M.: Microbial and environmental factors affecting nitrate removal in bio-electrochemical systems (BES), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5440, https://doi.org/10.5194/egusphere-egu23-5440, 2023.

EGU23-5615 | Posters on site | BG1.4 | Highlight

Crop plant effects on denitrification – what have we learned in six years DASIM project? 

Pauline Sophie Rummel, Reinhard Well, Johanna Pausch, Paulina Englert, Amanda Matson, Lukas Beule, Sebastian Floßmann, Jonas Eckei, Birgit Pfeiffer, and Klaus Dittert

Denitrification in agricultural crop production is one of the main sources of gaseous N2O and N2 losses to the environment. To successfully develop mitigation strategies, it is crucial to understand N2O production pathways, but also to quantify all other gaseous N losses, especially N2 emissions. Therefore, this project aimed (1) to identify the main drivers of denitrification during plant growth and in the post-harvest period, (2) to quantify denitrification derived N2O and N2 losses during the cropping season, and (3) to assess the interactions between plant litter quality, initial litter degradation, and formation of hotspots of N2O and N2 production. We conducted experiments on the laboratory, greenhouse, and field plot scale using the 15N gas flux method and HeO2 atmosphere to directly measure N2O and N2 losses and to determine the fraction of denitrification derived N losses. We worked with soils, crops, temperature and moisture conditions that are typical for our central German humid-temperate climate.

Plant growth affected all controlling factors of denitrification, especially soil moisture, NO3 and Corg availability. Crop species differed in their growing patterns and N uptake throughout the growing season controlling both N and C availability in soil. Accordingly, N2O and N2 emission patterns differed between crop species. Overall, emissions were highest when plant N uptake was low, i.e., during early growth stages and ripening, and after harvest. On the field scale, soil moisture and temperature were major controls of N2O+N2 losses.

In a climate chamber study under controlled temperature conditions, N2O and N2 fluxes mainly derived from denitrification of labeled 15NO3 in anoxic microsites, while nitrification simultaneously occurred in more oxic parts of the soil, potentially contributing to formation of unlabeled N2O. Increasing soil moisture with irrigation increased denitrification rates in anoxic hotspots, which corresponded with increasing N2O and especially N2 fluxes. At the same time, it restricted nitrification and thus decreased the share of nitrification-dependent processes contributing to N2O formation.

Incorporation of plant litter increased CO2, N2O, and N2 losses irrespective of litter quality, soil moisture or soil type/SOM content. We found that under O2 limiting conditions (70 % WFPS), the fraction of easily degradable C controlled the magnitude of N2O and N2 losses after litter incorporation. Under moderate soil moisture (50-60 % WFPS), interactions between litter degradation and SOM turnover affected the time course and processes contributing to N2O formation. Overall, our high-resolution gas flux measurements showed that N2O+N2 emissions from harvest residues can contribute significantly to the total N loss. 

How to cite: Rummel, P. S., Well, R., Pausch, J., Englert, P., Matson, A., Beule, L., Floßmann, S., Eckei, J., Pfeiffer, B., and Dittert, K.: Crop plant effects on denitrification – what have we learned in six years DASIM project?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5615, https://doi.org/10.5194/egusphere-egu23-5615, 2023.

EGU23-5834 | ECS | Posters on site | BG1.4

Prolonged Flooding followed by drying increase greenhouse gas emissions differently from soils under grassland and arable land uses 

Yafei Guo, Ernesto Saiz, Aleksandar Radu, and Sami Ullah

Abstract

    Under the predicted climate change scenarios, heavy precipitation could result in prolonged flooding (PF) and flooding-drying (FD) of soils in agriculture. The influence of PF and FD on soil greenhouse gas fluxes and nitrogen (N) dynamics of arable and grassland soils, which are the dominant land use types in UK soil, is still unclear. Two months of soil incubation experiments were conducted to find out the impact of PF and FD on soil nitrogen dynamics and greenhouse gas fluxes from arable and grassland soil. The result showed the developed ion selective electrodes (ISE) sensor was working to measure NH4+ in the first 5 days of real-life application under both grassland and arable soil. There were less N2O-N emissions in grassland and arable soil when soil moisture was higher than 100% water-holding capacity (WHC). Arable soil had more N2O-N emissions when soil moisture was higher than 100% WHC compared to grassland soil due to a low pH. Grassland soil had more N2O-N emissions when soil moisture was lower than 100% WHC compare to arable soil due to a high carbon and nitrogen source. When soil moisture was greater than 100% WHC, the available NO3--N in the soil controlled N2O-N emissions of grassland more effectively. The N2O-N emissions of grassland soil were more controlled by soil stable NH4+-N and NO3--N when soil moisture was lower than 100% WHC. The emissions of N2O-N and CO2-C were increased with the time of FD. FD significantly increased N2O-N, CO2-C, and CH4-C emissions in grassland soil compared to arable soil by 0.93, 2.15, and 37.29 times, respectively. Converting arable land use to grassland could increase the greenhouse gas (GHG) emissions under climate change (heavy rain). Further research needs to be done to find out how to reduce the GHG emissions under climate change after transfer arable to grassland.

How to cite: Guo, Y., Saiz, E., Radu, A., and Ullah, S.: Prolonged Flooding followed by drying increase greenhouse gas emissions differently from soils under grassland and arable land uses, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5834, https://doi.org/10.5194/egusphere-egu23-5834, 2023.

EGU23-6382 | ECS | Orals | BG1.4

Modeling coupled nitrification-denitrification in manure-amended soil 

Jie Zhang, Elisabeth Larsen Kolstad, Wenxin Zhang, Per-Erik Jansson, Iris Vogeler Cronin, and Søren O. Petersen

The flux of nitrous oxide (N2O) from the soil to the atmosphere is an important contributor to the global greenhouse effect. Spatial variation in the distribution of factors that drive N2O producing processes often creates hotspots within soil that are difficult to quantify and model, and this is particularly the case after manure amendment. In the stagnant soil matrix, solute diffusion is crucial in supplying the nitrate (NO3-)to nearby zones, i.e., hotspots, to maintain a locally high NO3- reduction. To provide detailed insight into the spatiotemporal variability of nitrogen (N) transformations around N2O hotspots, we propose a multi-species, reactive transport model containing kinetic reactions of soil respiration, nitrification, nitrifier denitrification, and denitrification, built on a system of partial differential equations. The model was used to simulate the amount of N2O, dinitrogen (N2) and carbon dioxide (CO2) emitted from a 10 cm soil profile with time, and concentration profiles of crucial intermediates. The measured N2O and N2 fluxes correlate well with the model simulations, with a simulated stratification of growing nitrifying and denitrify activities in and around the manure hotspot which is consistent with previous incubation experiments. N2O evolution was sensitive to the initial setup of oxygen (O2) availability, and anaerobic condition was maintained in the saturated manure zone throughout the simulation period, demonstrating the necessity of simulating the heterogeneity within soil in N2O models. Simulation experiments will be conducted to assess the effects of solute diffusion on N transformations. We anticipate that diffusive NO3- transport to be crucial to facilitate the coupled nitrification-denitrification around the manure zone. Neglecting such a process in process models may make it difficult to reflect the rapid turnover of nitrogen pool around organic hotspots and underestimate N2O emissions. The model and its parameters allows for new detailed insight into N2O formation processes in heterogeneous environments.

How to cite: Zhang, J., Kolstad, E. L., Zhang, W., Jansson, P.-E., Cronin, I. V., and Petersen, S. O.: Modeling coupled nitrification-denitrification in manure-amended soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6382, https://doi.org/10.5194/egusphere-egu23-6382, 2023.

EGU23-6652 | ECS | Orals | BG1.4

The production of N2O from sheep urine patches is influenced by soil properties. 

Danielle Hunt, Laura Cardenas, Davey Jones, and David Chadwick

The urine patch from livestock creates an active hotspot of soil nitrogen (N) cycling due to the intrinsically high N and carbon (C) loading rates. These N hotspots frequently result in N losses to the atmosphere or leaching from soil. N losses vary due to climate conditions, soil conditions, and management practices. However, we do not fully understand how these factors influence N cycling and nitrous oxide (N2O) emissions from urine patches. Intensive lowland grazing systems on mineral soils have been relatively well studied in this context, however, other grazing systems such as extensive upland systems on organic soils have been much less studied.

To investigate the effect of soil type on N cycling and N2O emissions in the urine patch, soil was collected from pastures in an altitudinal gradient, from an improved lowland mineral soil with coastal influence to unimproved organic soil under acid grassland.  Depending on the position along the gradient, the soils change in properties such as pH, bulk density, organic matter content, cation exchange capacity and nutrient availability. Soil was collected for a laboratory incubation study from four sites including two lowland sites (Cambisol and Cambisol with coastal influence) and two upland sites (Podzol and Histosol). Soils were sieved and divided into four replicates of each treatment. Sheep urine from Welsh Mountain ewes was applied at an equivalent loading rate of 150 kg N ha-1 to half of the soil and the remaining half received the equivalent volume of water as a control. All the treatments were held at 70% water-filled pore space to optimise both moisture conditions for nitrification and denitrification to occur. Over 100 days, greenhouse gas emissions were monitored along with soil pore water nitrate and ammonium concentrations.

Soil type had an overall significant effect on N2O emissions with the highest cumulative emissions during this period being from the Podzol and the lowest cumulative emissions being from the Histosol. The two lowland sites showed no significant differences. There was a delay in nitrification in the Podzol, with the majority of the N2O being emitted a month after urine application. The Histosol showed no evidence of nitrification as there was no build-up of nitrate concentrations over the experiment. This was probably due to differences in soil pH in the soils. There were no differences in carbon dioxide or methane emissions from the four soils, but there was a spike in methane flux on the Podzol which corresponded with increases in N2O fluxes from this soil type.

This experiment has shown that certain upland soils have the potential to produce N2O emissions and cycle N under optimal conditions, although this is at a much slower rate than the lowland sites. Results from this incubation study helps improve our understanding of how soil properties in organic soils affect N cycling and contribute to knowledge gaps on the sustainability of upland grazing systems.

How to cite: Hunt, D., Cardenas, L., Jones, D., and Chadwick, D.: The production of N2O from sheep urine patches is influenced by soil properties., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6652, https://doi.org/10.5194/egusphere-egu23-6652, 2023.

Soil microbial processes in drylands are limited by multiple abiotic factors, the most important being water and macronutrients (nitrogen (N) and phosphorus (P)). Understanding of relative importance of different abiotic factors for soil microbial processes is important because drylands are important regulators of global carbon (C) cycle and there is close connection between water, N, and C cycles. To assess how soil activity is affected by removing multiple nutrient limitations and manipulating water availability we conducted a short-term, multifactorial field experiment. We manipulated water, N, and P availability by application of the nutrients and water in the field. We evaluated how soil respiration, nitrous oxide, and nitric oxide emissions responded to increasing water, N and P availability individually and interactively in the Negev Desert. We hypothesized that neither water nor nutrient addition alone will enhance the activity of desert soils. On the other hand, removing multiple limitations will accelerate soil nutrient cycling. Further we hypothesized that acceleration of soil nutrient cycling will be reflected in high soil emissions of N2O, NO, and CO2 as proxies for the N cycle and respiration, respectively. We found that increasing water availability in desert soils significantly accelerated soil respiration rates but not the N cycle. Nitrogen availability affected soil NO production but not soil respiration. Soil emissions of N2O were unaffected by neither water nor nutrients additions. Phosphorus additions had no effect on soil microbial activity either alone or synergistically together with N and water.

How to cite: Gelfand, I. and Osei-Yeboah, M.: Contrasting effects of increase in water and nutrients availability on soil respiration and soil nitric and nitrous oxide emissions in desert., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7971, https://doi.org/10.5194/egusphere-egu23-7971, 2023.

EGU23-8168 | ECS | Orals | BG1.4

Cross-Comparisons of Sediment Incubation Methods to Bound Stochastic Influences on Denitrification of Natural Waters from Mississippi River Floodplain Wetlands 

Stony S. Samberg, Marjorie L. Brooks, Scott D. Hamilton-Brehm, Joseph M. Krienert, and Jonathan W.F. Remo

Flood regimes in large river systems such, as the Mississippi River, are inherently stochastic meaning that floodplain wetlands experience varying hydrostatic pressures of groundwater upwelling (exfiltration) and infiltration from overland flooding. Distinctions in water delivery can drastically alter the oxygen levels and groundwater delivery into wetland sediments where anaerobic microbes remove nitrates through denitrification. Our findings bound conditions for modeling denitrification rates across oxic flood waters versus exfiltration by anoxic groundwaters. Four-by-four factorial laboratory incubation treatments included oxic versus anoxic waters (degassed with helium) introduced by exfiltration or infiltration (Figs. 1A, 1B).

Sediments collected in triplicate from four floodplain wetlands located along Dogtooth Bend segment of the Mississippi River near the Ohio River confluence were incubated with river water. Sediments were incubated at 29 oC for 96 h. Nitrogen gas production was measured by membrane inlet mass spectrometry (MIMS). Inflow and outflow waters were analyzed for nitrate, ammonia, phosphate, and dissolved organic carbon while sediments were characterized for their physical traits. In contrast to most studies, that estimate denitrification relative to surface area in incubations only (i.e. address conditions of surface flooding), we also present our findings relative to sediment volumes (i.e. evaluate denitrification rates from exfiltration of groundwater). Regression analyses compared denitrification from surface area versus volume calculations (R2 values > 0.89); consequently providing an excellent tool for converting estimates from surface area alone to varying sediment saturation for more rigorous assessments of subsurface interactions.

Average denitrification rates relative to sediment volume were significantly higher in anoxic-deep-injection cores (“AD cores”; 23.83 + 1.94 N mg/m3/d) compared to anoxic-surface-delivery cores (“AS cores”; 19.98 + 1 N mg/m3/d), that also exceeded oxic-deep-injection cores (“OD cores"; 14.96 + 1.78 N mg/m3/d) and oxic-surface-delivery cores (“OS cores”; 10.23 + 1.04 N mg/m3/d). Thus, average denitrification followed an anoxic-injection hierarchy of AD > AS > OD > OS (p-values < 0.003), which was maintained for denitrification relative to surface area. Regarding site-specific distinctions, for sandy sites this hierarchy persisted, and each treatment differed significantly. Sites with clayey sediments had very-low permeability regardless of injection type; thus only oxic versus anoxic treatments differed significantly irrespective of water delivery. By contrast sites with loamy sediments, injection type significantly influenced denitrification rates while neither oxic nor anoxic water treatments differed. An AICc model showed that phosphate, ammonia, temperature variation, dissolved oxygen, and sand content explained 33% (p-value < 0.05) of the variation in denitrification rates across all cores and treatments.

Our findings highlight the greater insights provided from cross-comparison incubation designs to better inform landscape-scale models of denitrification rates across floodplain wetlands depending on the magnitude and duration of flooding.

How to cite: Samberg, S. S., Brooks, M. L., Hamilton-Brehm, S. D., Krienert, J. M., and Remo, J. W. F.: Cross-Comparisons of Sediment Incubation Methods to Bound Stochastic Influences on Denitrification of Natural Waters from Mississippi River Floodplain Wetlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8168, https://doi.org/10.5194/egusphere-egu23-8168, 2023.

EGU23-8878 | ECS | Posters on site | BG1.4

Low vs. upland - copper addition regulates denitrification in cropland soils from N2O emissions hotspots in Denmark 

Yujia Liu, Daniel Mika-Nsimbi Poultney, Florian Wichern, Per Ambus, and Carsten W. Müller

Agricultural land-use makes up around 38% of the total global land surface. Farming activities are a major source of greenhouse gas emissions (carbon dioxide, methane and nitrous oxide) worldwide. Nitrous oxide (N2O) emissions from agricultural land are an important contributor to the overall greenhouse gas budget. The high spatial and temporal variation of N2O emissions in agricultural lands makes it more challenging and important to quantify the actual emissions. Denmark’s glacial landscape is characterized by a high abundance of topographic depressions. These are typically flooded for 1-3 months per year, mainly during late winter and spring season. As these depressions are frequent in agricultural areas, their soils are exposed to an increased nitrate availability due to regular fertilization. The combination of high-water saturation and high nitrate availability results in distinct landscape denitrification and thus N2O emission “hotspots”.

The reduction of N2O to N2 by N2O reductase can be an important mechanism to mitigate N2O emissions. The N2O reductase is both Cu and pH sensitive. Studies have showed Cu-modified organic fertilizer have the potential to enhance the reduction from N2O to N2, and therefore decrease N2O emissions from fields.

In this study, we aimed to elucidate if Cu addition alters the emission of N2O from upland and depression soils in a different way. Therefore, we conducted an incubation experiment with both upland and depression soils, testing how different levels of Cu addition and two different water levels affect the emission of N2O. In order to differentiate the N2O production pathways (nitrification or denitrification), we applied 15N tracer in the form of 15NH415NO3 or 14NH415NO3. We also added 13C labelled maize residues to be able to trace the consumption of fresh substrate in the course of denitrification as affected by different Cu and water levels.

Interestingly, although the soils were homogenized and incubated at the same water availability, we demonstrated a clearly higher N2O emission from the depression soils compared to the upland soils. In general, we were able to demonstrate that Cu addition clearly reduces the level of N2O emissions from upland soils, which is clearly more pronounced at higher soil water levels.

How to cite: Liu, Y., Poultney, D. M.-N., Wichern, F., Ambus, P., and Müller, C. W.: Low vs. upland - copper addition regulates denitrification in cropland soils from N2O emissions hotspots in Denmark, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8878, https://doi.org/10.5194/egusphere-egu23-8878, 2023.

The COVID-19 global pandemic has significantly affected air quality due to changes in human behavior. Gaseous nitrous acid (HONO) is a significant precursor of the hydroxyl radicals (OH), powerfully influencing atmospheric oxidization capacity and air quality. However, the impacts on the sources and sinks of HONO during COVID-19 are not well understood. Here, we observed the concentrations of HONO, nitric oxide (NO), and nitrogen dioxide (NO2) in the suburb of Shanghai during May 2020 (P1), August 2020 (P2), and April 2021 (P3) to analyze seasonal variations of HONO chemistry and also clarify how different pandemic phases influence HONO sources and sinks. The average concentration of HONO during P1, P2 and P3 showed an increasing trend (0.292 ± 0.0078、0.358 ± 0.0115, and 0.415 ± 0.0115 ppb, respectively), with direct emission from vehicles was the most essential source of the nocturnal HONO concentration (38.14%, 47.52%, and 50.95%, respectively), followed by heterogeneous conversion of NO2. The daytime HONO sources presented noticeable discrepancy among three study periods. In spring, homogeneous reaction was the primary HONO source with a mean production rate of 0.2 ppb h−1, while there was almost no unknown source (Punknown). In summer, however, the average production rate of homogeneous reaction decreased to 0.15 ppb h−1, while Punknown was up to 58% of the whole HONO production, demonstrating some strongly enhanced source(s) in the summer season. By comparing HONO budgets between different pandemic phases, the contributions of vertical and horizontal transport doubled from P1 to P3, with the average production rates increasing from 0.03 to 0.06 ppb h−1. Our results also showed that the strict lockdown measures reduced the unknown sources of HONO (P1), and correspondingly, as Shanghai implemented regular epidemic prevention and control measures, the relatively high rate of Punknown was observed during P3, making up 35% of the whole HONO production. What is more, through the strong correlation with J(HNO3) (r = 0.9) and J(NO2) (r = 0.89), it can be argued that the photolysis of nitric acid and photo-enhanced heterogeneous conversion may be a vital production pathway. The HONO photolysis was the major loss pathway, occupying approximately 85% of HONO loss during all campaigns. During noontime, the average photolysis loss rate was 1.07、2.40 and 1.86 ppb h−1, accounting for up to 96% of the HONO sinks. Dry deposition was the second important loss pathway, especially in the morning and before sunset. This study indicates remarkable seasonal variations of HONO and the effects of COVID-19, and has significant implications on controlling measures of air pollutants in megacity.

How to cite: Wang, Y. and Wu, D.: Sources and sinks of atmospheric nitrous acid (HONO) in the megacity of Shanghai during COVID-19, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11088, https://doi.org/10.5194/egusphere-egu23-11088, 2023.

Reactive nitrogen from anthropogenic inputs such as fertilizers and its changes in the transport and fate in the environment as a consequence of changes in land management may alter the nitrogen balance of a catchment and thus its concentrations in water bodies. This can be enhanced by increased wet and dry deposition of nitrogen from anthropogenic activities. In the Mau Forest Complex in Kenya, the annual export of nitrogen from a catchment dominated by smallholder agriculture was reported to be almost double those from the native forest. Fertilization and livestock management are assumed to have contributed to this shift, but no empirical evidence is available to support this. Furthermore, the contribution of the nitrogen wet deposition through rainfall and throughfall to the nitrogen balance has not been quantified yet. This study aims at determining the contribution of nitrogen wet deposition and anthropogenic inputs to the nitrogen balance of a 27 km² headwater catchment characterized by smallholder farming in the Mau Forest Complex. Rainfall and throughfall samples were collected from precipitation collectors in 10 different locations within 24 hours after 11 rainfall events in the span of 9 weeks. Anthropogenic inputs were estimated from a household survey (n=185). 

Median and Interquartile range (IQR) concentrations of total dissolved nitrogen (TDN) were slightly higher in rainfall i.e. 0.7 (0.4–0.9) mg N L−1 than in throughfall i.e. 0.6 (0.4–0.8) mg N L−1, resulting in median wet deposition of 0.04 (0.02–0.06) kg N ha−1 from rainfall and 0.03 (0.01–0.06) kg N ha−1 from throughfall per sampled rainfall event (4.7 mm; 2.5–8.1 mm). Extrapolated to the full year, this leads to an estimated nitrogen input from wet deposition of 11.7 (9.5-12.5) kg N ha−1 yr−1 from rainfall and 6.4 (5.7-9.6) kg N ha−1 yr−1 from throughfall, although this estimate does not consider seasonal changes in TDN concentrations in rain- and throughfall. Median inputs of nitrogen from inorganic fertilizer was 25 (15.2–40.2) kg N ha−1 yr−1, whereas annual inputs from livestock were 76 (49-125) kg N ha-1 yr−1.

Reactive nitrogen inputs from farming and livestock are higher than the estimated wet deposition and could therefore significantly impact the catchment nitrogen balance. It follows therefore that a continual and increase use of nitrogen inputs from manures and fertilization with inorganic fertilizers, as well as further forest cover loss for agricultural expansion may lead to future elevated levels of nitrogen in the environment, leading to risks of progressive enrichment of water bodies and further nitrogen imbalances. To keep these in check, appropriate manure management strategies, fertilizer application and control of forest conversion cannot be overemphasized.

How to cite: Kasebele, M., Jacobs, S., and Breuer, L.: Inputs of reactive nitrogen from wet deposition and fertilization in a tropical montane catchment characterised by smallholder farming., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11325, https://doi.org/10.5194/egusphere-egu23-11325, 2023.

EGU23-12416 | ECS | Orals | BG1.4

Nitrogen losses from food production in the North China Plain compared to environmental targets 

Fanlei Meng, Mengru Wang, Reinder Ronda, Maryna Strokal, Carolien Kroeze, Lin Ma, Wen Xu, and Fusuo Zhang

North China Plain (NCP) is a region in China, with highly intensive food production and a hotspot of nitrogen (N) losses to the environment. Region-specific N management is, therefore, required to effectively reduce agricultural N losses. For this it is important to identify the N flows and environmental targets in the food chain (including crop production, animal production, food processing, and human consumption) at the county scale. We developed an integrated assessment N framework. It combines a food chain approach with an air quality model and groundwater model. We apply this method to quantify the relative contributions from parts of the food chain to N losses. We identify environmental targets to air and water in Quzhou, a typical agricultural county in the NCP. We found that N losses to the environment from the food chain were ~11 kt  in Quzhou in 2017. Approximately 80% of this amount is from crop and animal production, which is primarily caused by the low N use efficiency in crop production (28%) and animal production (18%). Ammonia (NH3) emissions to air (4.1 kt N) and N leaching (2.1 kt N), and direct discharges of manure to water (1.9 kt N) are the main contributors to the N losses in Quzhou. To meet the environmental targets for air quality (PM2.5) and groundwater quality, the NH3 emissions and N leaching need to be reduced by 55%, and 21-50%, respectively. Our findings indicate that better nutrient management is urgently needed to reduce agricultural N losses and to support Agriculture Green Development in NCP.

How to cite: Meng, F., Wang, M., Ronda, R., Strokal, M., Kroeze, C., Ma, L., Xu, W., and Zhang, F.: Nitrogen losses from food production in the North China Plain compared to environmental targets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12416, https://doi.org/10.5194/egusphere-egu23-12416, 2023.

EGU23-13010 | Posters on site | BG1.4

Advancing the realistic simulations of N2O emissions in cold climate watersheds using Soil and Water Assessment Tool 

Prasad Daggupati, Uttam Ghimere, and Asim Biswas

Nitrous Oxide (N2O) emissions in Soil and Water Assessment Tool (SWAT) is heavily dependent on soil temperature and moisture. However, SWAT has been known to highly under-estimate soil temperature which limits movement of water and nutrients throughout the soil profile and does not replicate freeze-thaw cycles which is of paramount importance in the N2O emissions. Thus, we integrated modules developed by individual researchers pertaining to energy balanced snow melt, rain-on-snow, energy balanced soil temperature and N2O emission into a single SWAT model and termed in SWAT Cold Climate N2O (SWAT-CCN2O). SWAT-CCN2O was then tested for flows, sediments, soil temperature and N2O emission simulation in a representative watershed in Ontario, Canada, the Speed River basin. Compared with the unaltered SWAT model, SWAT-CCN2O was able to significantly capture the pre-spring snowmelt induced flows. A more realistic simulation of soil temperature (soil temperatures did not go below -4oC) and a satisfactory simulation of sediments and N2O emissions were observed in the basin, which highlights the potential to use SWAT-CCN2O for streamflow and N2O simulation in cold climatic catchments. This version of SWAT is made publicly available for further improvements and applications in similar watersheds.

 

 

How to cite: Daggupati, P., Ghimere, U., and Biswas, A.: Advancing the realistic simulations of N2O emissions in cold climate watersheds using Soil and Water Assessment Tool, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13010, https://doi.org/10.5194/egusphere-egu23-13010, 2023.

EGU23-13162 | Posters on site | BG1.4

Modeling hot-spot of N2 and N2O production in agricultural soils as introduced by liquid organic fertilization 

Balázs Grosz, Rene Dechow, and Reinhard Well

Prediction of liquid organic fertilizer effects by biogeochemical models on denitrification and associated N2O and N2 fluxes in soils is inappropriate, because previous studies mostly excluded N2, and the calibration of the models without N2 data is inaccurate. Besides, the models mostly homogenize the substrate content of the applied manure with the corresponding substrate pools of the soil, without the consideration of the effects of the liquid manure induced hot-spots in the soil. Therefore, the main goal of the MOFANE Project was to develop a new approach dealing with hot spot effects in manure amended soils. A simple and static model approach (Sommer et al., 2004) was improved and developed for a dynamic model to consider the effect of the manure induced hot-spots in the soils. It contemplates the effect of the application technique of the liquid manure (surface or injected), the ammonium and labile organic carbon content of the manure, the water content and the structure of the soil to calculate the NH3 loss, the N mineralization and O2 consumption of the degradable organic content, the nitrification and the denitrification in the manure-soil hot-spot region. The substrate exchange and flow are calculated based on the water potential difference between the liquid manure and soil. A laboratory experiment was conducted to provide proper input and output data for the model testing.  A sandy (Grosz et al., 2022) and a loamy arable soil were investigated in 10 days laboratory incubations. The temperature was constant 15oC and the water-filled pore space (WFPS) were constant 40% and 60%. The soils were amended with and without artificial slurry in three manure treatments (control, surface-applied, injected). N2O and CO2 fluxes were quantified by gas chromatography. N2 and source-specific N2O flux was quantified by isotope-ratio mass spectrometry. The results of laboratory experiments will be used for testing the model accuracy. 

Grosz, B., Kemmann, B., Burkart, S., Petersen, S. O., and Well, R.: Understanding the Impact of Liquid Organic Fertilisation and Associated Application Techniques on N2, N2O and CO2 Fluxes from Agricultural Soils, Agriculture, 12, 692, https://doi.org/10.3390/agriculture12050692, 2022.

Sommer, S. G., Petersen, S. O., and Møller, H. B.: Algorithms for calculating methane and nitrous oxide emissions from manure management, Nutrient Cycling in Agroecosystems, 69, 143–154, https://doi.org/10.1023/B:FRES.0000029678.25083.fa, 2004.

 

How to cite: Grosz, B., Dechow, R., and Well, R.: Modeling hot-spot of N2 and N2O production in agricultural soils as introduced by liquid organic fertilization, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13162, https://doi.org/10.5194/egusphere-egu23-13162, 2023.

EGU23-13402 | ECS | Orals | BG1.4 | Highlight

In situ measurement of denitrification (N2 and N2O) and greenhouse gas emissions (CO2, N2O, CH4) in conservation agriculture 

Gianni Micucci, Fotis Sgouridis, Stefan Krause, Iseult Lynch, Niall P. McNamara, Gloria Dos Santos Pereira, Felicity Roos, and Sami Ullah

Over the last 80 years, intensive agriculture has had numerous consequences globally. In particular, it has led to a loss of soil organic carbon (SOC) and a decline in soil fertility, resulting in higher nitrogen (N) fertilizer application. Excess of fertilizer has driven the emissions of N2O, a greenhouse gas (GHG) 298 times more potent in inducing global warming than CO2. Under the UK target of net zero emissions by 2050 and considering the recent increase in fertilizer price, conservation agriculture appears a viable solution to sustain food production whilst reducing global warming. Along with species diversification and reduction (or absence) of tillage, a permanent soil organic cover is the third pillar of conservation agriculture. In particular, “leys” consist in temporary pastures planted in between crops or to restore exhausted soils. These leys are planted with a mix of N fixing plants, which have a unique symbiotic relationship with soil bacteria collectively called “Rhizobia” that transform atmospheric N2 into organic nitrogen. The mineralization of this organic nitrogen is expected to reduce dependence on N fertilizer. In contrast with the traditional grass/clover mix, herbal leys have recently gained popularity amongst UK farmers. They consist in a more complex mixture of grasses, legumes and herbs, bringing a range of benefits to forage, livestock health and soil fertility.

Here we report a year’s worth of measurement of soil mineral N and SOC contents, N mineralization potential, in situ measurement of denitrification (which transforms N fertilizer into N2O and N2) and total GHG emissions (CO2, N2O, CH4) from a 4-year-old herbal ley in comparison with an arable field. We measured denitrification with our newly developed method (see Micucci et al., 2022) and GHG with conventional GHG chambers. First results show that during the early growing season (April to June), total N2O emissions measured from GHG chambers were 10 to 60 times higher in the arable field than in the herbal ley, due to N fertilizer application. Similarly, a high loss of this N fertilizer was observed during April in the form of denitrified N2.

Micucci, G., Sgouridis, F., Krause, S., Lynch, I., McNamara, N. P., Dos Santos Pereira, G., Roos, F., and Ullah, S. (2022). Towards enhanced sensitivity of the 15N Gas Flux method for quantifying denitrification in soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-585, https://doi.org/10.5194/egusphere-egu22-585

 

 

 

How to cite: Micucci, G., Sgouridis, F., Krause, S., Lynch, I., McNamara, N. P., Dos Santos Pereira, G., Roos, F., and Ullah, S.: In situ measurement of denitrification (N2 and N2O) and greenhouse gas emissions (CO2, N2O, CH4) in conservation agriculture, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13402, https://doi.org/10.5194/egusphere-egu23-13402, 2023.

EGU23-14663 | ECS | Posters on site | BG1.4

Effect of various fertilizer doses on soil N2O and CO2 emissions in cropland soils in Hungary 

Ádám Mészáros, Boglárka Magyar, Nicholas Omoding, János Balogh, Szilvia Fóti, Krisztina Pintér, Attila Percze, Giulia De Luca, and Zoltán Nagy

Quantifying greenhouse gas emissions has been a priority for climate scientists for decades. As a result, the spatial and temporal dynamics of emissions have been widely studied, but to date, we still do not fully understand the main drivers of the variation in patterns. The aim of our research is to quantify the spatio-temporal variability of these greenhouse gases under various nutrient supply conditions and different tillage practices (plow or cultivator) on sandy-clay and loam soils.

Our measurements took place near Kartal on loam soil and near Gödöllő on sandy-clay soil, in Central Hungary, in 2022 on winter wheat. CO2 and N2O fluxes are analyzed with Li-cor gas analyzers (LI-870 CO2/H2O Analyzer and LI-7820 N2O/H2O Trace Gas Analyzer) connected to the 8200-01S Smart Chamber. We can track both modest changes brought on by natural factors (precipitation, temperature variations) and the impact of more significant artificial factors (fertilization, type of tillage) on the N2O and CO2 flux using these rather sensitive devices. In Kartal, 24, and in Gödöllő 40 KG-PVC rings with a diameter of 20 cm were placed in the study areas and measured on a weekly basis. In Kartal half of the collars received fertilizer, and the other half was covered during the application. In Gödöllő, 8 different treatments can be distinguished, resulting from a combination of 3 different fertilizer doses (0kg/ha, 75kg/ha, and 150kg/ha), 2 tillage methods (plow and cultivator), and soil conditioners. The collars protrude 4 cm from the soil and the inner soil surface has been cleared of vegetation. The gas exchange between soil and air is measured for 3 minutes on each collar, while simultaneously measuring soil moisture, temperature, and vegetation cover (LAI) near the collars. Soil samples were taken monthly to a depth of 15 cm, and 50 cm from the collars.

Based on our observation, in the case of N2O emission, there are significant differences between the two study areas. On average N2O emissions in Gödöllő were higher than in Kartal. Cumulative N2O emissions were significantly higher in areas receiving higher doses of fertilizer. For 150kg/ha, the highest value was 42 g N m2, while for 0kg/ha and 75kg/ha, lower values of around 16-20 g N m2 were observed. With average emissions of 420–500 g C m2, there are no discernible variations in cumulative CO2 emission across treatments. However, the temporal variation of both GHG emissions shows differences due to the persistent drought in summer. During the rainy season, spring and autumn, a more intense N2O and CO2 flux were observed due to soil respiration.

How to cite: Mészáros, Á., Magyar, B., Omoding, N., Balogh, J., Fóti, S., Pintér, K., Percze, A., De Luca, G., and Nagy, Z.: Effect of various fertilizer doses on soil N2O and CO2 emissions in cropland soils in Hungary, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14663, https://doi.org/10.5194/egusphere-egu23-14663, 2023.

EGU23-14831 | ECS | Posters on site | BG1.4

Microscale oxygen distribution to predict denitrification in structured soil 

Maik Lucas, Lena Rohe, Hans-Jörg Vogel, Reinhard Well, and Steffen Schlüter

Different microbial species are capable of producing N2O through multiple pathways, and these can coexist within short distances due to different microenvironmental conditions in the heterogeneous soil structure. Denitrification in soil occurs predominantly in microbial hotspots where denitrifiers use nitrate as an alternative electron acceptor. Soil water content has a profound influence on denitrification because it determines the diffusion lengths of oxygen through air- and water-filled pores, as well as the diffusion of denitrification products from the source in the soil to the atmosphere. Predicting N2O emissions resulting from denitrification, however, is notoriously difficult without quantifying microscale hotspots.

In this experiment we evaluated results from an incubation experiment with undisturbed cores from two different soils having contrasting structures (cropland vs. meadow) at three different water contents. In addition to high-resolution gas chromatography, 15N-labeled nitrate solution allowed information on denitrification and its product ratios to be gained through IRMS measurements at selected time points. On the other hand, 7 needle-type optodes per core in combination with image analysis of images derived by X-ray tomography are used to quantify small scale diffusion distances and hotspots around POM. Last, a previous experiment, with the same but sieved soil and without particulate organic matter (POM), is used as a comparison to further investigate the influence local structure heterogeneity and POM on denitrification.

First results indicate that the reduction of diffusion pathways during sieving in the arable soil resulted in significantly lower emissions after sieving compared to the structured soil, while N2O+N2 emissions in the meadow soil were only slightly affected by sieving. For the first time, we were able to generate 3D images of O2 saturation by combining image-derived diffusion length information with the measured O2 concentrations. These allowed to explain high variabilities of N2O+N2 emissions from the field structured cores.

How to cite: Lucas, M., Rohe, L., Vogel, H.-J., Well, R., and Schlüter, S.: Microscale oxygen distribution to predict denitrification in structured soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14831, https://doi.org/10.5194/egusphere-egu23-14831, 2023.

EGU23-15598 | Orals | BG1.4 | Highlight

Effect of residue management and nitrification inhibitor on N2O and N2 emissions from an intensive sugarcane cropping system in sub-tropical Australia 

Clemens Scheer, Johannes Friedl, Daniel Warner, David Rowlings, Weijin Wang, and Peter Grace

Sugarcane is typically produced under conditions that are known to stimulate soil denitrification, i.e. high fertiliser inputs in combination with high levels of crop residue (trash) retention and a warm and humid climate, and high levels of fertiliser N losses from intensive sugarcane systems have been reported. However, there is still insufficient reliable data on N2 losses from sugarcane soils based on field measurements since it is inherently challenging to measure N2 emissions against the high atmospheric N2 background. This study investigated the effect of cane trash removal and the use of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N2 and N2O emissions on a commercial sugarcane farm in sub-tropical Australia using the 15N gas flux method. Substantial gaseous N losses were observed under current management practice where cane trash retention and N fertiliser application (145 kg N ha-1 as urea) resulted in elevated losses of N2O and N2 from a subsurface N fertiliser band, with more than 50% of these gaseous N losses emitted as N2O. Cane trash retention increased the magnitude of N2O and N2 emissions reflecting overlapping effects of increased soil water content and labile C supply from residues, but had no effect on the N2O/(N2+N2O) ratio. The NI DMPP was extremely effective in reducing overall N2O and N2 losses and also promoted complete denitrification of N2O to environmentally benign N2, with only 4% of total N2O and N2 losses emitted as N2O. This shows that DMPP might be especially effective in reducing N2O emissions from banded fertiliser were localized zones of high NO3- concentration around the fertiliser band are created that are particularly vulnerable to denitrification. Consequently, the use of DMPP in sugarcane systems with banded fertiliser does not only offer environmental benefits by reducing N2O emissions but also substantially reduces overall denitrification losses, providing an effective strategy to improve NUE and reduce N2O emissions for the Australian sugarcane industry.

How to cite: Scheer, C., Friedl, J., Warner, D., Rowlings, D., Wang, W., and Grace, P.: Effect of residue management and nitrification inhibitor on N2O and N2 emissions from an intensive sugarcane cropping system in sub-tropical Australia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15598, https://doi.org/10.5194/egusphere-egu23-15598, 2023.

Specific nitrification inhibitors (NIs) have been widely used to disentangle the contribution of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB) as well as nitrite oxidizers to the nitrification process in specific environments. However, if these previously reported NIs can also be used to evaluate the activity of the newly discovered complete ammonia oxidizers (comammox) Nitrospira, remains understudied. Here we evaluated various NIs for their impact and specificity regarding inhibition of comammox Nitrospira in batch cultures of pure and mixed strains of AOA, AOB and comammox. Using these batch cultures, we observed that chlorate could specifically inhibit the ammonia oxidation and nitrite oxidation activity of comammox Nitrospira, while it had no effect on the tested AOA and AOB strains. This inhibitory effect of chlorate on comammox Nitrospira was subsequently confirmed based on 13CO2-DNA-stable isotope probing (13C-DNA-SIP) analysis. Furthermore, by applying a set of specific NIs, the nitrification and nitrous oxide (N2O) production rates of comammox Nitrospira in coastal wetlands were estimated as 17.45 ng N g-1 h-1(26.9 % of the total rate) and 0.0083 µmol-1 L h-1 (28.5%). Altogether, we identified and applied an effective and specific inhibitor of comammox Nitrospira, which allowed quantifying comammox activity in wetlands of the Yangtze Estuary, shedding new light on the ecological roles of comammox bacteria in coastal wetland environments.

How to cite: Han, P. and Sun, D.: Comammox Nitrospira contributed nitrification and N2O production activity in coastal wetland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17035, https://doi.org/10.5194/egusphere-egu23-17035, 2023.

Tropical forests in southern China have been suffering high level of acid rain in recent decades, which may alter soil phosphorus (P) supply capacity and thus affect ecosystem productivity. We conducted a 10-yr field experiment of simulated acid rain (SAR) to examine how acidification impacts seasonal changes of soil P fractions in a tropical forest with highly-acidic soils in south China. The results showed that SAR significantly reduced soil P bioavailability, with increased occluded P pool but reduced the other more labile P pools in the dry season. The decreased soil P bioavailability was primarily related to the repressed P desorption capacity and enhanced P sorption during soil acidification, which regulated by acid-activated soil iron/aluminum minerals and soil organic matter. However, in the wet season, SAR did not change microbial P, soluble P and labile organic P pools. Different from the decline of microbial abundance in the dry season, SAR increased ectomycorrhizal fungi and its ratio to arbuscular mycorrhiza fungi in the wet season, which significantly stimulated phosphomonoesterase activities and likely promoted the dissolution of occluded P. Our results suggest that, even in already highly-acidic soils, the acidification-induced P limitation could be alleviated by stimulating ectomycorrhizal fungi and phosphomonoesterase activities. The differential responses and microbial controls of seasonal soil P transformation revealed here should be implemented into ecosystem biogeochemical model for predicting plant productivity under future acid deposition scenarios.

How to cite: Hu, Y., Chen, J., and Deng, Q.: Mycorrhizal fungi alleviate acidification-induced phosphorus limitation: Evidence from a decade-long field experiment of simulated acid deposition in a tropical forest in south China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2919, https://doi.org/10.5194/egusphere-egu23-2919, 2023.

EGU23-3112 | ECS | Orals | BG1.5

Can we account for the “missing” phosphorus in simulated low phosphorus agricultural systems? 

Jennifer Davies, Victoria Janes-Bassett, Martin Blackwell, Andrew Burgess, Jessica Davies, and Philip Haygarth

Long term total phosphorus (P) concentration, inorganic P and / or organic P concentration in agricultural soils is not commonly measured. As a consequence, computer-based models, that have been developed to predict P responses to changing management practices, are typically tested against soil “agronomically available” P data (as measured by tests such as; Olsen-P, Morgan’s-P, Mehlich-3, etc.) and those that do test against total P are limited to a few agricultural experimental sites across the world. While there is some correlation with total soil P, the term “available P” is arguably a functional concept, influenced by a large number of biotic and abiotic factors, rather than a direct soil measurement. This highlights a developmental gap in P modelling which could help to further unlock our understanding of P biogeochemical cycling when used in conjunction with contemporary empirical P research. 

Investigating P cycling in agricultural systems using the computer-based model N14CP has demonstrated that the model can predict carbon and nitrogen cycling and crop yields well for systems receiving abundant fertiliser. However, in systems where there is no P applied, predicted yield responses are greatly underestimated, with “missing” P input concentrations equivalent to annual fertiliser application rates. To date, the testing of N14CP has not included the P pools due to a lack of soil total P and/or soil organic P data from long-term field trials. Using recent total, organic and inorganic phosphate concentrations in the topsoil and yield data from two contrasting long-term field trial sites in the UK and the USA, this research will test P outputs and modelled yields from N14CP. It is hypothesised that the model will underestimate soil P concentrations, and crop yield, in the absence of P fertiliser inputs. This study will then apply changes to the mode model inputs, outputs and control processes to investigate whether these are sufficient to supply the crops and soil with the “missing” P. 

Understanding this source of “missing” P in N14CP will not only be useful for developing our understanding of P processes in computer-based models but could also further understanding of P processes linked to P draw-down in agricultural systems that have a history of high legacy P concentrations. 

How to cite: Davies, J., Janes-Bassett, V., Blackwell, M., Burgess, A., Davies, J., and Haygarth, P.: Can we account for the “missing” phosphorus in simulated low phosphorus agricultural systems?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3112, https://doi.org/10.5194/egusphere-egu23-3112, 2023.

EGU23-7187 | Posters on site | BG1.5

Phosphorus Bioavailability and Speciation dynamics within fluvial suspended sediments 

David O'Connell, Qingzin Zhang, Diogo Ferreira, Sara Sandstrom, Robbie Goodhue, Laurence Gill, and Yongfeng Hu

Eutrophication of agricultural catchment streams remains a global problem despite increasingly stringent regulations. Long term, sustained release of bioavailable phosphorus (P) from legacy P stored in fluvial sediments may impact downstream water quality, hence greater understanding is required regarding P speciation dynamics and potential release mechanisms from fluvial sediments to the water column.

This study examined the dynamic P fractions, speciation and bioavailability of suspended fluvial sediments from two geologically contrasting agricultural catchment streams (Ballyboughal (BB) and Tintern Abbey (TTA)) using a combination of complimentary techniques including sequential chemical  fractionations (SCF), Dual Culture Diffusion Apparatus mesocosm experiments (DCDA), X-ray fluorescence spectroscopy (XRF) and X-ray Absorption Near-edge Structure (XANES) spectroscopy. Results from the SCF of fluvial suspended sediments pre- and post DCDA microcosm experiment’s revealed that loosely bound P (PH2O), exchangeable P against OHions (PNaOH), and organic P (POrg) are the major P fraction contributors to the bioavailable P fraction which would promote algal growth. Other P fractions including acid-soluble P principally associated with calcium phosphate compounds (PHCl) and ferric bound P (PCBD) showed relatively lower mineralisation to bioavailable P. Significantly, P K-edge XANES spectra enabled identification of seasonal and spatial P speciation dynamics and the existence of major P fractions including Fe-P and Ca-P associated mineral phases along with organic P compounds. Additionally, SCF, XRF and Ca K-edge XANES show contrasting Ca associated phases between both catchments, with calcite dominant in the BB sediments and Ca humic-complexes predominant in the TTA sediments. Contrasting Ca-P fraction transformation mechanisms of the two catchments are indicated by P redistributions in SCF and the reduction of elemental Ca amounts from XRF analysis. Calcium (Ca) K-edge XANES shows the BB catchment has a large amount of calcite while TTA was shown to contain organic Ca compounds, likely in the form of Ca-humic-complexes. This study provides a conjunctive method for future studies and validation of P speciation and bioavailability assessment associated with fluvial suspended sediments from agricultural catchments streams. The results contribute to future catchment scale sedimentary fluvial P modelling and enhanced catchment management strategies to improved water quality.

 

How to cite: O'Connell, D., Zhang, Q., Ferreira, D., Sandstrom, S., Goodhue, R., Gill, L., and Hu, Y.: Phosphorus Bioavailability and Speciation dynamics within fluvial suspended sediments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7187, https://doi.org/10.5194/egusphere-egu23-7187, 2023.

EGU23-7734 | Orals | BG1.5 | Highlight

Land plant evolution and volcanism led to the Late Devonian mass extinction 

Gabriel Filippelli, Matthew Smart, William Gilhooly, Kazumu Ozaki, Christopher Reinhard, Jessica Whiteside, and John Marshall

The evolution of land plants in terrestrial environments brought about one of the most dramatic shifts in the history of the Earth system — the birth of modern soils — and likely stimulated massive changes in marine biogeochemistry and climate. In particular, multiple marine mass extinctions characterized by widespread anoxia, including the Late Devonian mass extinction around 375 million years ago (Ma), may have been linked to terrestrial nutrient release driven by newly-rooted landscapes. Here, we use recently generated constraints from Earth’s lacustrine rock record as variable inputs in an Earth system model of the coupled C-N-P-O2-S biogeochemical cycles in order to evaluate whether recorded changes to phosphorus fluxes would be adequate to sustain Devonian marine biogeochemical perturbations and extinction dynamics. Results show that globally scaled riverine phosphorus export during the Late Devonian mass extinction generates widespread marine anoxia and produces carbon isotope, temperature, oxygen, and carbon dioxide perturbations generally consistent with the geologic record. Similar results for a competing extinction mechanism, large scale volcanism, suggest the Late Devonian mass extinction was likely multifaceted with both land plants and volcanism as contributing factors.

How to cite: Filippelli, G., Smart, M., Gilhooly, W., Ozaki, K., Reinhard, C., Whiteside, J., and Marshall, J.: Land plant evolution and volcanism led to the Late Devonian mass extinction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7734, https://doi.org/10.5194/egusphere-egu23-7734, 2023.

EGU23-12271 | ECS | Posters on site | BG1.5

The impact of changing freeze-thaw dynamics under recent climatic changes on nutrient leaching in a Swedish agricultural field 

Anna Lackner, Tobias Klöffel, and Jennie Barron

Agriculture can be a significant contributor of nutrients, such as phosphorus (P) and nitrogen (N) to surface water, increasing the risk of eutrophication. Soil frost and freeze-thaw (FT) cycles impact both the transport of nutrients through changes in the hydrologic regime of the field and the mobility/availability of nutrients through changes in the biogeochemistry of the field.  With a changing climate, changes in the frequency and duration of FT cycles are expected in regions of higher latitudes and altitudes. However, there is a knowledge gap related to the response of nutrient leaching with changing FT patterns in a changing climate.

The aim of this study was to investigate the impact of soil freezing and thawing on nutrient leaching (N, P) from an agricultural field in northern Sweden for the period 1989-2021. The FT dynamics were modelled in terms of a soil temperature profile using an explicit soil moisture and energy-based process model – the COUP, at an hourly time step. Long term environmental monitoring data of surface and drainage runoff, combined with soil temperature and soil moisture data were used for model calibration and validation. Finally, the modelled FT dynamics and measured nutrient concentrations and runoff were statistically related to each other.

Our preliminary findings confirm the importance of soil frost occurrence for the separation of surface runoff and drainage. However, no clear relationship between soil FT dynamics and nutrient loads (or concentrations) in surface or drainage water could be observed. This suggests that changes in the hydrological regime through freezing and thawing are most important for the amount and export pathways of nitrogen and phosphorous as compared to alternative mechanisms of nutrient mobilisation.

How to cite: Lackner, A., Klöffel, T., and Barron, J.: The impact of changing freeze-thaw dynamics under recent climatic changes on nutrient leaching in a Swedish agricultural field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12271, https://doi.org/10.5194/egusphere-egu23-12271, 2023.

EGU23-12467 | ECS | Orals | BG1.5

Human-caused increases in phosphorus burials in global lake sediments during the Holocene 

Luyao Tu, Madeleine Moyle, John Boyle, Paul Zander, Tao Huang, Lize Meng, Changchun Huang, Martin Grosjean, and Xin Zhou

Human activities have contributed to significant disruptions of the phosphorus (P) cycle on Earth’s surface.  Yet, there is little information about when and how humans started to influence the global P cycle in the past. In this study, we reconstruct lake-wide P burial rates during the Holocene based on sediment-P data of 108 lakes across the globe. The results indicate the first distinct increases in lake P burial rates after the mid-late Holocene (at around 4000 years before present BP) at global scales and in Europe. Yet, different land-use histories have caused different timings of the first increases in lake P records in other regions, with ~2000 BP in China and ~550 BP in North America. We further show that global lake P-sequestration rate from ~4000 BP to 1850 Common Era (CE) has doubled compared with that in the period before 4000 BP. Since 1850 CE, the value increased ~six-fold compared with the period before 4000 BP. These findings indicate that anthropogenic activities have been affecting the global P cycle over a pre-industrial background for millennia.

How to cite: Tu, L., Moyle, M., Boyle, J., Zander, P., Huang, T., Meng, L., Huang, C., Grosjean, M., and Zhou, X.: Human-caused increases in phosphorus burials in global lake sediments during the Holocene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12467, https://doi.org/10.5194/egusphere-egu23-12467, 2023.

EGU23-13516 | Posters on site | BG1.5

P-TRAP – Reducing diffuse phosphorus input to surface waters 

Thilo Behrends and Sylvia Walter

In 2019 the EU Marie Sklodowska-Curie Training Network P-TRAP has been launched and is now approaching its end. The project has been targeting the diffuse flux of phosphate (P) into surface waters, i.e. the problems of understanding and controlling environmental P fluxes. P-TRAP has been aiming to develop new methods and approaches to trap P in drained agricultural areas and in the sediments of eutrophic lakes. The P-TRAP technologies have in common that they rely on the naturally strong connection between the biogeochemical cycling of P and iron (Fe). Trapping of P involved the application of Fe-containing by-products from drinking water treatment. P-TRAP aspired the ideas of a circular economy and aimed at recovering the retained P in agricultural systems and to convert it into valuable products for agricultural applications. In order to direct and support the development of the technologies, process-orientated investigations on the behaviour of P during the transformation of Fe minerals have been conducted. The poster will highlight some results from the project and will present conclusions, which can be drawn based on the current achievements.

How to cite: Behrends, T. and Walter, S.: P-TRAP – Reducing diffuse phosphorus input to surface waters, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13516, https://doi.org/10.5194/egusphere-egu23-13516, 2023.

EGU23-13631 | Posters on site | BG1.5

Fe solid phase chemistry and its effect on P retention in the sediment of a eutrophic peat lake 10 years after Fe amendment 

Melanie Münch, Rianne van Kaam, Karel As, Stefan Peiffer, Gerard ter Heerdt, and Andreas Voegelin

Globally, surface water quality and ecosystem functioning are challenged by anthropogenic P inputs. While sterner legislation has led to lower external P loading, internal loading fed by legacy P accumulated in the sediment has become the controlling factor of surface water P concentrations in many European freshwater systems. Fe amendment is a treatment method to control internal P loading, but is not always successful on the long term. In Lake Terra Nova, a polymictic shallow peat lake in the Netherlands, treatment with FeCl3 only led to a temporary decrease in sedimentary P release. Two years after treatment seasonal peaks in surface water P concentrations started to appear and have been increasing in intensity for the past 8 years. Depth-resolved solid phase analysis by sequential Fe and P extractions was combined with bulk X-ray absorption spectroscopy (XAS) at the Fe K-edge and high-resolution micro-X-ray fluorescence spectrometry (µ-XRF) and µ-XAS. At spots with distinctively high Fe contents, pyrite and silicate-bound Fe are identified by microscopic and spectroscopic analyses. The spectroscopic data, however, also point to a finely dispersed Fe species in the sediment matrix which most likely corresponds to Fe complexed by OM in the surface sediment. The correlation of the distribution of P and Fe suggests that P is bound to these Fe-OM complexes. This interpretation is supported by the sequential extraction results which showed that the Fe treatment induced a shift in the dominant P pool from Ca-bound P to Fe- and OM-bound P. Overall, the results indicate that FeCl3 application caused a change in sediment P dynamics towards a highly redox sensitive system in which P bound to Fe-OM is released to the surface water during seasonally low bottom water oxygen concentrations. The results of this study therefore indicate that FeCl3 may not be the ideal additive for the remediation of internal P loading in peaty water bodies due to the high affinity of Fe to OM.

How to cite: Münch, M., van Kaam, R., As, K., Peiffer, S., ter Heerdt, G., and Voegelin, A.: Fe solid phase chemistry and its effect on P retention in the sediment of a eutrophic peat lake 10 years after Fe amendment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13631, https://doi.org/10.5194/egusphere-egu23-13631, 2023.

EGU23-16011 | Orals | BG1.5

Speciation of soil organic phosphorus: Steps from NMR spectra to bioavailability 

Jürgen Schleucher, Lenny Haddad, Marina Paneque, David Wardle, Andrea Vincent, and Reiner Giesler

Phosphorus (P) is an essential element for all life on Earth. Understanding P cycling is in the context of global change crucial both for modelling of global biogeochemical cycles and for agricultural productivity. Recently, concerns about the future of P fertilizer supply have prompted much research on soil P and method development. 31P Nuclear Magnetic Resonance (NMR) Spectroscopy has been used to analyse speciation of inorganic and of organic P species (Po), using in alkaline soil extracts1. The region containing signals from phosphomonoesters is particularly important because these compounds are considered biologically active, but there are still significant problems to be resolved particularly for this region of P NMR spectra, including: 1. Poor signal resolution often makes quantification of Po species in this region very challenging. 2. It is unclear if observed signals are due to free P species, or originate from P compounds bound to high-molecular weight soil matter. 3. The question needs to be addressed how signals observed in alkaline extracts relate to P species that were originally present in the soil. Here we present two approaches to address these problems:

In a study of a 5000-year soil chronosequence in Northern Sweden2, we found that humus P composition barely changed, although time since fire varied up to 5000 years. We will present a new method to back-calculate original Po speciation from the observed composition. Results of this method indicate absence of “recalcitrant” Po species, and instead indicate that most Po was originally present as biologically active P metabolites, probably present in live soil organisms. We will discuss implication of these findings for P biogeochemistry.

Second, we studied a diverse group of soils to address how the poorly resolved phosphomonoester region should best be analysed. Deconvolution techniques are required to handle the overlap, but a better understanding of the nature of the signals is required for reliable quantification. Based on combined analysis of 1D 31P NMR, 2D 1H-31P NMR and 31P linewidth measurements, we present a strategy for quantification of phosphomonoester species, as next step in linking observed Po speciation to P bioavailability.

 

(1) Cade-Menun BJ, Preston CM (1996) A comparison of soil extraction procedures for 31P NMR spectroscopy. Soil Sci 161:770–785

(2) Andrea G. Vincent, Jürgen Schleucher, Reiner Giesler, David A. Wardle (2022) Soil phosphorus forms show only minor changes across a 5000‑year‑old boreal wildfire chronosequence. Biogeochemistry (2022) 159:15–32  https://doi.org/10.1007/s10533-022-00910-2

(3) Vestergren J, Vincent AG, Jansson M et al (2012) High-resolution characterization of organic phosphorus in soil extracts using 2D 1H–31P NMR correlation spectroscopy. Environ Sci Technol 46:3950–3956. https:// doi. org/ 10. 1021/ es204016h

How to cite: Schleucher, J., Haddad, L., Paneque, M., Wardle, D., Vincent, A., and Giesler, R.: Speciation of soil organic phosphorus: Steps from NMR spectra to bioavailability, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16011, https://doi.org/10.5194/egusphere-egu23-16011, 2023.

EGU23-16254 | ECS | Posters on site | BG1.5

Phosphate pools and oxygen signature in the hyper-arid Atacama Desert 

Xiaolei Sun, Wulf Amelung, Federica Tamburini, Erwin Klumpp, Ramona Morchen, and Roland Bol

The Atacama Desert is a temperate desert restricted by the Pacific Ocean and the Andeans, which is an ideal place to study the biogeochemical phosphate-water dynamics in the conditions with extreme limited water and biomass. We hypothesized that phosphate pools and oxygen signature change along with the increasing distance to the coast and thus aridity. The surface soils (0-10 cm) were sampled along the transect with distance to coast in Paposo region (~25°S) which is located in the Coastal Cordillera nearby the Pacific Ocean from 2.3 to 22.9 km, including 9 altitude sites (600 m, 900 m, 880 m, 920 m, 1000 m, 1200 m, 1450 m, 1700 m, 2110 m). Each site involved 3 samples surrounding the plant with a distance of 0-10 cm and other 3 samples far from the plant with 1 m. The Ca-bound P (HCl-extracted P followed the Hedley sequential P fractionation) accumulated along the increasing distance to coast within 37.9 km and could be described by a mono-exponential regression mode. However, an initial declining trend was detected for phosphate 18O of HCl-Pi and it reached a steady-state condition beyond 10 km from the coastline, which was the maximum distance that advective fog could penetrate inland. Only the nearest site at 2.3 km (600 m.a.s.l) to coast showed an isotope value within the range of full isotopic equilibrium with biologically cycled phosphate. Furthermore, the effects of the present plant distribution on surface soil Hedley P stocks and phosphate 18O signatures were very limited. We concluded that both P stocks and phosphate 18O signatures followed primarily the aridity gradient but phosphate 18O signatures could work as a tracer for long-term climate conditions.

How to cite: Sun, X., Amelung, W., Tamburini, F., Klumpp, E., Morchen, R., and Bol, R.: Phosphate pools and oxygen signature in the hyper-arid Atacama Desert, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16254, https://doi.org/10.5194/egusphere-egu23-16254, 2023.

EGU23-17064 | ECS | Orals | BG1.5

Formation and aging of Fe(III) and Ca precipitates in exfiltrating anoxic groundwater and effects on phosphate retention 

Ville Nenonen, Ralf Kaegi, Stephan J. Hug, Stefan Mangold, Jörg Göttlicher, Lenny H.E. Winkel, and Andreas Voegelin

The oxidation of dissolved Fe(II) upon exfiltration of anoxic groundwaters into oxic surface waters leads to precipitation of poorly crystalline Fe(III)-solids that strongly bind phosphate (PO4) and thereby can attenuate eutrophication. Fresh Fe(III)-precipitates may transform into more crystalline phases over time, which may lead to the release of initially co-precipitated PO4. The formation and transformation of Fe(III)-precipitates in natural waters is strongly affected by other solutes (Ca, Mg, PO4, silicic acid (SiO4)) that interfere with Fe(III) precipitation and transformation, and thereby also affect PO4 binding. Furthermore, in Ca-containing waters, the repartitioning of PO4 released from Fe(III)-precipitates into Ca-carbonates or –phosphates, could limit PO4 release.

For better understanding the fate of PO4 in aquatic environments, there is a need for a mechanistic understanding of coupled Fe(III)- and Ca-precipitate formation and transformation processes induced by groundwater exfiltration, and their effects on PO4 sequestration. In this laboratory study, we examined the effects of Ca, Mg, and SiO4 on the formation and transformation of Fe(III)- and Ca-precipitates in bicarbonate-buffered aqueous solutions upon Fe(III)-precipitate formation by Fe (II) oxidation in the presence of PO4, over aging periods up to 100 d. Changes in precipitate structures were probed with spectroscopic and microscopic techniques and linked to changes in the retention or release of PO4 over time.

The results show that especially Ca and SiO4 contribute to effective PO4 retention via multiple interdependent processes, and thereby strongly attenuate PO4 release over extended periods of time.

 

REFERENCES

Senn, A.-C.; Kaegi, R.; Hug, S. J.; Hering, J. G.; Mangold, S.; Voegelin, A., Composition and structure of Fe(III)-precipitates formed by Fe(II) oxidation in near-neutral water: Interdependent effects of phosphate, silicate and Ca. Geochim. Cosmochim. Acta 2015, 162, 220–246.

Senn, A.-C.; Kaegi, R.; Hug, S. J.; Hering, J. G.; Mangold, S.; Voegelin, A., Effect of aging on the structure and phosphate retention of Fe(III)-precipitates formed by Fe(II) oxidation in water. Geochim. Cosmochim. Acta 2017, 202, 341–360.

 

How to cite: Nenonen, V., Kaegi, R., Hug, S. J., Mangold, S., Göttlicher, J., Winkel, L. H. E., and Voegelin, A.: Formation and aging of Fe(III) and Ca precipitates in exfiltrating anoxic groundwater and effects on phosphate retention, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17064, https://doi.org/10.5194/egusphere-egu23-17064, 2023.

EGU23-17071 | ECS | Posters on site | BG1.5

Impact of agricultural land use and management on available soil phosphorus content in agricultural catchments of Ireland 

Ognjen Zurovec, Daniel Hawtree, Simon Leach, and Bridget Lynch

The build-up of soil phosphorus (P) in agricultural soils exceeding crop requirements can lead to diffuse P losses that could impair surface water quality. Therefore, adequate spatial information is required to develop viable tools and recommendations for sustainable P management at the local scale. Here, we present a database of nearly 8.000 samples, collected over a 12-year period in four meso-scale (~10 km2) agricultural catchments in Ireland. The agricultural area of each catchment is divided into sampling units (up to 2 ha) and soil samples are repeatedly taken from each sampling unit every 4 years. Four soil sampling campaigns were carried out to date. The results were analysed in the context of soil test P values (Morgan’s P) and classified according to the P index system as defined in the Ireland’s Nitrates Action Programme.

Overall, levels of soil test P did not show substantial changes, with the exception of the most recent sampling campaign. However, when the collected data are considered in a spatial context and accompanied with soil data and land use information, they reveal a more complex story. Notable differences in soil P trends are observed at the individual catchments scale and impacted by land use, agricultural management intensity and some soil properties across and within the catchments. Similarly to the overall soil test P trends, the total area under P index 4 soils (above optimal) decreased in the period preceding the most recent sampling campaign. The most notable decreases in P index 4 soils are found in tillage and drystock fields, but also in the catchment dominated by highly stocked dairy farms availing of a nitrate derogation.

Recent increases in soil test P and consequently areas under P index 4 may not be linked to increased organic or mineral P inputs, but rather come as a result of an overall increase in soil pH from increased lime application observed over the most recent period, which had an impact on the extractable Morgan’s P content. On-farm redistribution of fertilizer P inputs to soils with lower P index status has the potential to increase P use efficiency and decrease P loss risk to surface water.

How to cite: Zurovec, O., Hawtree, D., Leach, S., and Lynch, B.: Impact of agricultural land use and management on available soil phosphorus content in agricultural catchments of Ireland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17071, https://doi.org/10.5194/egusphere-egu23-17071, 2023.

EGU23-17121 | ECS | Posters virtual | BG1.5

Strategies for optimizing the scalable microbial synthesis of vivianite 

Lordina Eshun, Victoria Coker, Sam Shaw, and Jonathan Lloyd

Vivianite (Fe3(PO4)2·8H2O) has been reported to form as a secondary mineralization product during the microbial reduction of phosphate-containing Fe(III) minerals [1 – 3]. The phosphate-rich nature of vivianite makes it a suitable sink for phosphorus, which is a scarce and irreplaceable resource, and a major contributor to eutrophication in surface water bodies. There is, therefore, interest in synthesizing vivianite by Fe(III) reducing bacteria such as Geobacter sulfurreducens and Shewanella putrefaciens, to treat phosphate-rich waters, recovering the phosphate for re-use in agriculture. In this study, factors including the presence and absence of phosphate and electron shuttle, the buffer system, pH, microbial load, and the type of Fe(III)-reducing bacteria that influence the formation of vivianite under laboratory batch systems have been investigated. The rate of Fe(II) production, and its interaction with the residual Fe(III) and other oxyanions (e.g., PO43-, CO32-) was found to be the main driving factor for secondary mineral formation. Magnetite was formed in treatments with zero phosphates whereas vivianite and green rust were formed in treatments containing phosphate. The rate and extent of Fe(III) bioreduction were higher in Shewanella putrefaciens than in Geobacter sulfurreducens. Vivianite and green rust were both identified as the dominant endpoints in treatments with Geobacter sulfurreducens and Shewanella putrefaciens.

 

[1] Fredrickson, Zachara, Kennedy, Dong, Onstott, Hinman, & Li (1998). Geochimica et Cosmochimica Acta 62, 3239-3257.

[2] O’Loughlin, Boyanov, Gorski, Scherer, & Kemner (2021). Minerals 11, 149

[3] Zachara, Kukkadapu, Fredrickson, Gorby, & Smith (2002). Geomicrobiology Journal 19, 179–207. 

How to cite: Eshun, L., Coker, V., Shaw, S., and Lloyd, J.: Strategies for optimizing the scalable microbial synthesis of vivianite, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17121, https://doi.org/10.5194/egusphere-egu23-17121, 2023.

Internal phosphorus (P) loading from sediments is an important component of total P supply to the water column of many eutrophic lakes.  A long-standing paradigm states that the magnitude of internal loading through diffusion of P is limited in the presence of iron (Fe) oxides at the sediment-water-interface, due to efficient sorption and co-precipitation of P with oxide minerals. Iron-rich sediments underlying oxic water columns in shallow lake areas are thus expected to retain, rather than release P. However, recent statistical investigations have suggested that oxic epilimnetic areas of stratifying lakes may be responsible for a significant fraction of the internal P loading in these systems [1], implying a "leaky" seal of Fe oxides even under oxic conditions. Here we study the mechanisms of internal P loading in two Fe-rich eutrophic lakes in southern Finland through geochemical analysis of porewaters, over one annual cycle at five study sites per lake. Diffusive flux calculations using Fick's Law, and upscaling to whole-lake areal estimates, confirm that shallow (approx. <10 m) areas dominate internal P loading even during stratified conditions in summer. Furthermore, the highest instantaneous fluxes of the study were observed in shallow sites in late summer. The results suggest in shallow eutrophic settings with a high organic matter flux to sediments and elevated summer temperatures, remineralization reactions at the sediment-water interface regenerate P efficiently enough to escape capture by Fe oxides, even under sediment molar Fe/P ratios >20.     

 

[1] Tammeorg, O., Möls, T., Niemistö, J., Holmroos, H., & Horppila, J. (2017). The actual role of oxygen deficit in the linkage of the water quality and benthic phosphorus release: potential implications for lake restoration. Science of the Total Environment, 599, 732-738.

How to cite: Jilbert, T., Zhao, S., and Hermans, M.: The paradox of internal phosphorus loading from oxic areas of iron-rich eutrophic boreal lakes: insights from porewater geochemistry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17179, https://doi.org/10.5194/egusphere-egu23-17179, 2023.

EGU23-17209 | Posters on site | BG1.5

Effect of increased sulfate reduction on the stability of authigenic vivianite in lake sediment 

Harm van Kuppevelt and Michael Hupfer

The presence of high levels of phosphorus (P) in surface waters can negatively impact the functioning of ecosystems and water quality. Despite efforts to decrease P concentrations, the accumulation of P reservoirs in sediment from past high external inputs still poses a problem. This legacy P can contribute to internal P loading, which has been shown to extent eutrophication in many freshwater systems. To effectively restore these systems, it is important to understand the geochemical processes that control the fixation and release of P in the sediment. While it is known that under anoxic conditions, P can be stored in the form of the mineral vivianite, it is not well understood if the vivianite reservoir can also act as a source of P. In a field study, mixed sediment from Lake Arendsee, Germany that naturally contained vivianite was placed in the sediment floor of the same lake, in both sulfate reduction depths and below (0-45cm). After three months, the sediment was retrieved and analyzed to investigate the effect of sulfide production on the vivianite pool. Sequential extraction and XRD analysis of the sediment solid phase showed that at shallower depths where sulfide concentrations were higher, there was a significant reduction of the vivianite reservoir and a decrease of P bound to Fe relative to S bound Fe forms. This suggests that P bound in vivianite can act as a P source in sulfidic sediment. Further research is needed to determine the extent of this phenomenon in lakes with increased sulfide production.

How to cite: van Kuppevelt, H. and Hupfer, M.: Effect of increased sulfate reduction on the stability of authigenic vivianite in lake sediment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17209, https://doi.org/10.5194/egusphere-egu23-17209, 2023.

EGU23-95 | ECS | Orals | BG1.6 | Highlight

Global warming beyond 1.5–2⁰C multiplies the rainforests' tipping risk 

Chandrakant Singh, Ruud van der Ent, Ingo Fetzer, and Lan Wang-Erlandsson

Tropical rainforests invest in their root systems to store soil moisture from water-rich periods for use in water-scarce periods. An inadequate root-zone soil moisture storage predisposes or forces these forest ecosystems to transition to a savanna-like state, devoid of their native structure and functions. Yet changes in soil moisture storage and its influence on the rainforest ecosystems under future climate change remain uncertain. Using a mass-balance-based (empirical) understanding of root zone storage capacity, we assess the future state of the rainforests and the forest-savanna transition risk in South America and Africa. For this, we analyse the hydroclimatic estimates of 33 Earth System Models under four different shared socioeconomic pathway scenarios (i.e., SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5). We find that by the end of the 21st century, nearly one-third of the total forest area will be influenced by climate change. Furthermore, beyond 1.5-2⁰C warming, ecosystem recovery reduces gradually, whereas the forest-savanna transition risk increases several folds. For Amazon, this risk can grow by about 1.5-6 times compared to its immediate lower warming scenario, whereas for Congo, this risk growth is not substantial (0.7-1.65 times). The insight from this study underscores the urgent need to limit global surface temperatures below the Paris agreement.

How to cite: Singh, C., van der Ent, R., Fetzer, I., and Wang-Erlandsson, L.: Global warming beyond 1.5–2⁰C multiplies the rainforests' tipping risk, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-95, https://doi.org/10.5194/egusphere-egu23-95, 2023.

EGU23-357 | ECS | Posters on site | BG1.6

Is priming influenced more by in situ or incubation temperatures? Evidence from a 1500 m elevation gradient in the Amazon 

Angela Katherine Martin Vivanco, Outi-Maaria Sietiö, Aino Seppänen, Bruno Glaser, Oona Uhlgren, Kevin Mganga, Subin Kalu, Andrew Nottingham, and Kristiina Karhu

Abstract

Growing attention has been paid to the significance of microbial metabolism for soil carbon (C) and nutrient cycle as well as their feedback effects on global warming. The estimated annual release of carbon dioxide from soil microbial respiration is 60 petagrams, and because aged native soil organic matter (SOM) has higher temperature sensitivity, the anticipated warming is expected to speed up its C release. Warming might increase litter and root exudate C inputs to hasten the decomposition of older SOM through priming effects. Microorganisms, however, have a rapid rate of growth and turnover and the new SOC formation from labile C inputs may be able to partly counteract the C losses through primed SOM decomposition. We are examining how temperature and the availability of C and nutrients affect the size and direction of priming effects. We conducted an incubation experiment on intact soil cores collected from altitudes ranging from 1500 to 3050 m a.s.l, and that were part of the Kosñipata gradient in the Peruvian Amazon. We incubated the soils for seven months, at two different temperatures to evaluate the impact of temperature, on the magnitude of priming effect caused by added 13C-labeled glucose, which was used as a model compound for labile root derived C inputs. At the end of the incubation, we determined the amount of 13C integrated into the microbial biomass and amino sugars, as well as the 13C remaining in bulk SOM.

Keywords 

Soil organic carbon, Priming effect, Soil respiration, Microbial residues, Elevational (altitudinal) gradient, Amazon

How to cite: Martin Vivanco, A. K., Sietiö, O.-M., Seppänen, A., Glaser, B., Uhlgren, O., Mganga, K., Kalu, S., Nottingham, A., and Karhu, K.: Is priming influenced more by in situ or incubation temperatures? Evidence from a 1500 m elevation gradient in the Amazon, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-357, https://doi.org/10.5194/egusphere-egu23-357, 2023.

EGU23-1307 | Orals | BG1.6

CloudRoots-Amazonia22: Integrating clouds with photosynthesis by crossing scales 

Jordi Vila-Guerau de Arellano and Oscar Hartogensis and the CloudRoots and collaborators from Brasil and Germany

How are carbon dioxide assimilation by photosynthesis and (shallow) cumulus clouds connected? What is the local interaction between rainforest evapotranspiration and cloud formation modulated by incoming regional air masses? These interrelated questions were the main drivers of the experimental campaign CloudRoots-Amazonia22 that took place at the ATTO/Campina supersites in the pristine Amazon rainforest during August 2022 (dry season). CloudRoots-Amazonia22 collected observational data to derive relationships between leaf level processes to canopy scales and connected them to the diurnal evolution of the clear to cloudy atmospheric boundary layer. At leaf level, first results indicate a diurnal asymmetry of the leaf conductance with maximum openings before midday. These observations are related to radiative energy fluxes to study the partitioning into sensible and latent heating and of plant-soil carbon dioxide exchnages. By coupling measurements of carbon and water stable isotopologues by fast laser instruments to turbulence measurements we aim to quantify flux variations related to the radiation fluctuations driven by clouds. These observations are integrated with 75 soundings of state variables and greenhouse gas profiles taken by flights below, through and above the cloud layers. We investigate what controls the transition from shallow to deep convection and the causality between the surface-cloud shear and the moisture transport at the interface between the different atmospheric layers. The observational analysis is completed with conceptual modelling and systematic large-eddy simulation experiments, which include dynamic vegetation models to advance our understanding of the diurnal energy, water and carbon cycles over the Amazon rainforest.

How to cite: Vila-Guerau de Arellano, J. and Hartogensis, O. and the CloudRoots and collaborators from Brasil and Germany: CloudRoots-Amazonia22: Integrating clouds with photosynthesis by crossing scales, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1307, https://doi.org/10.5194/egusphere-egu23-1307, 2023.

EGU23-4410 | Posters on site | BG1.6

Intra- and inter-annual changes in isoprene emission from central Amazonia 

Eliane Gomes Alves, Raoni Aquino Santana, Cléo Quaresma Dias-Junior, Santiago Botía, Tyeen Taylor, Ana Maria Yáñez-Serrano, Jürgen Kesselmeier, Pedro Ivo Lembo Silveira de Assis, Giordane Martins, Rodrigo de Souza, Sergio Duvoisin Junior, Alex Guenther, Dasa Gu, Anywhere Tsokankunku, Matthias Sörgel, Bruce Nelson, Davieliton Pinto, Shujiro Komiya, Bettina Weber, and Diogo Martins Rosa and the Cybelli Barbosa

Isoprene emissions are a key component in biosphere-atmosphere interactions, and the most significant global source is the Amazon rainforest. However, intra- and inter-annual variations in biological and environmental factors that regulate isoprene emission from Amazonia are not well understood and, thereby, poorly represented in models. Here, with datasets covering several years of measurements at the Amazon Tall Tower Observatory (ATTO) in central Amazonia, Brazil, we (1) quantified canopy profiles of isoprene mixing ratios across seasons of normal and anomalous years and related them to the main drivers of isoprene emission – solar radiation, temperature, and leaf phenology; (2) evaluated the effect of leaf age on the magnitude of the isoprene emission factor (Es) from different tree species and scaled up to canopy with intra- and inter-annual leaf age distribution derived by a phenocam; and (3) adapted the leaf age algorithm from MEGAN with observed changes in Es across leaf ages. Our results showed that the variability in isoprene mixing ratios was higher between seasons (max. during the dry-to-wet transition seasons) than between years, with values from the extreme 2015 El-niño year not significantly higher than in normal years. In addition, model runs considering in-situ observations of canopy Es and the modification on the leaf age algorithm with leaf-level observations of Es presented considerable improvements in the simulated isoprene flux. This shows that MEGAN estimates of isoprene emission can be improved when biological processes are mechanistically incorporated into the model.  

How to cite: Gomes Alves, E., Aquino Santana, R., Quaresma Dias-Junior, C., Botía, S., Taylor, T., Yáñez-Serrano, A. M., Kesselmeier, J., Lembo Silveira de Assis, P. I., Martins, G., de Souza, R., Duvoisin Junior, S., Guenther, A., Gu, D., Tsokankunku, A., Sörgel, M., Nelson, B., Pinto, D., Komiya, S., Weber, B., and Martins Rosa, D. and the Cybelli Barbosa: Intra- and inter-annual changes in isoprene emission from central Amazonia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4410, https://doi.org/10.5194/egusphere-egu23-4410, 2023.

EGU23-4499 | ECS | Posters on site | BG1.6

Top-down constraint of net carbon exchange in tropical South America 

Santiago Botía, Saqr Munassar, Thomas Koch, Amir Hossein Abdi, Luana S. Basso, Shujiro Komiya, Jost Lavric, David Walter, Luciana V. Gatti, Emanuel Gloor, John Miller, Wouter Peters, Christian Rödenbeck, and Christoph Gerbig

The contribution of vegetation to the South American carbon balance is critical for understanding the regional dynamics in net carbon exchange. Of particular interest is the role of the Amazon region as a sink or source of carbon to the atmosphere. Recent evidence indicate a weakening of the Amazon carbon sink, and when taking fires into account, the region represents a source of carbon to the atmosphere. In this study we use a regional atmospheric inversion system together with data from the Amazon Tall Tower Observatory (ATTO) and airborne profiles of CO2, to constrain the Net Biome Exchange (NBE) in tropical South America. At the domain-wide scale we find that the atmospheric observations can constrain 64% of the land mass, with uncertainty reductions in most of the Amazon region, and the adjacent Cerrado and Caatinga biomes. Furthermore, we provide a sub-regional-specific analysis showing the effect of assimilating the Amazon Tall Tower Observatory CO2 time series on the mean seasonal cycle of NBE for four areas within the Amazon, the Cerrado and the Caatinga. An emerging sink-source gradient between the Amazon region (sink) and the integrated effect of the Cerrado and Caatinga (source) is found, but the source is located in the boundaries and outside the eastern border of the legal Amazon. Optimized NBE estimates at regional and subregional scales are shown and the importance of the continuous measurements at ATTO is highlighted. Finally, we indicate the areas with a limited data constraint in our system and conclude that the observational network has to be further expanded for reducing the remaining uncertainty in top-down inverse approaches for this region.

How to cite: Botía, S., Munassar, S., Koch, T., Abdi, A. H., Basso, L. S., Komiya, S., Lavric, J., Walter, D., Gatti, L. V., Gloor, E., Miller, J., Peters, W., Rödenbeck, C., and Gerbig, C.: Top-down constraint of net carbon exchange in tropical South America, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4499, https://doi.org/10.5194/egusphere-egu23-4499, 2023.

Tropical rainforests in the Amazon play a vital role in absorbing atmospheric CO2, yet there remains a significant degree of uncertainty surrounding the process, magnitude, and potential future changes. In this study, we used outputs of Earth System Models (ESMs) to explore the impacts of dry-season precipitation changes on the terrestrial carbon cycle, with a specific focus on Gross Primary Production (GPP), which has yet to be thoroughly examined. The seasonal amplitude of GPP over the Amazon rainforests from the CMIP6 ensemble displayed significant variations among models resulting from dry-season decline, and these are much higher amplitude compared to reference data from 1981-2000. The regions with less precipitation are particularly vulnerable in the models, and this dry-season decline is anticipated to significantly intensify by the end of the 21st century due to the drying associated with global warming.

How to cite: Taguchi, T. and Ichii, K.: Analyzing the sensitivity of gross primary production to the water stress in the Amazon rainforest using CMIP6 models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6496, https://doi.org/10.5194/egusphere-egu23-6496, 2023.

EGU23-9165 | ECS | Posters on site | BG1.6

Soil fertility and drought stress episodes explain the variations in diameter growth of the hyperdominant Amazon tree species Eschweilera coriaceae 

Flavia Durgante, Niro Higuchi, Shinta Ohashi, John Ethan Householder, Florian Wittmann, and Susan Trumbore and the collaborators

Amazonian forest productivity is related to gradients in climate and soil fertility, and impacted by extreme climate events such as drought. However, interactions between soil fertility and drought in influencing regional and interannual variations in tree diameter growth are still poorly explored. To fill this gap, we used radiocarbon measurements to evaluate the variation in tree growth rates over the past decades for 30 individual trees from an important hyperdominant species, Eschweilera coriacea (Lecythidaceae). Trees were sampled from six sites in the state of Amazonas, Brazil, spanning a range of soil properties and climate. Using a linear mixed model, we show that temporal variations in mean annual diameter increment for a specific time period reflects interactions between soil fertility and SPEI drought index (Standardized Precipitation and Evapotranspiration Index). Overall differences between sites in mean tree growth, wood density and biomass production primarily reflected soil fertility, while temporal variations in growth response to drought also strongly dependence on soil fertility. Whereas drought strongly limited tree growth in fertile environments, its impact on tree growth was attenuated in poorer soils. Our results suggest that the growth response of trees to drought is strongly dependent on soil conditions, a facet of Amazon forest productivity that is still underexplored. As the Eschweilera coriacea is a hyperdominant species in the Amazon and is ranked second for highest biomass production in the basin, the pattern of tree growth in response to soil-climate interactions influences the carbon balance of the entire Amazon basin. This result has a large potential to improve predictions of how tropical tree growth affect the global carbon cycle in the face of climate change.

How to cite: Durgante, F., Higuchi, N., Ohashi, S., Householder, J. E., Wittmann, F., and Trumbore, S. and the collaborators: Soil fertility and drought stress episodes explain the variations in diameter growth of the hyperdominant Amazon tree species Eschweilera coriaceae, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9165, https://doi.org/10.5194/egusphere-egu23-9165, 2023.

EGU23-10412 | Orals | BG1.6

Turbulent Fluxes Within and Above the Amazon Roughness Sublayer 

Cléo Quaresma Dias-Junior, Nelson Dias, Otávio Acevedo, Luca Mortarini, Daiane Brondani, Pablo Oliveira, Alessandro Araújo, Leonardo Oliveira, Rosaria Ferreira, Ricardo Acosta, Bruno Takeshi, and Carlos Alberto Quesada

For tropical forests, such as the Amazon Forest, the turbulence intensity at the forest-atmosphere interface is high since in this region there is strong convective activity during the day and the aerodynamic roughness of the forest canopy is high. Heat and other scalar properties are exchanged between the flow and the canopy. Understanding these exchange mechanisms is essential for a variety of applications in various fields of science. Furthermore, it is known that the Amazon region has a strong influence on the transport of heat and water vapor to regions located at higher latitudes and plays an important role in the carbon cycle. Measurements carried out in micrometeorological towers are crucial for the correct quantifications of the turbulent fluxes. However, the use of micrometeorological towers in the Amazon is recent. High frequency measurements (eg Eddy covariance systems) in the Amazon rainforest were usually performed at a single point, often above the forest canopy. The first analyses from the fast response data clearly showed the existence of what is now known as the roughness sublayer (RSL). In these works, it was speculated that the surface boundary layer, was higher up. Within Amazonian RSL, important discoveries have already been made, for example: (i) the Monin-Obuhkov similarity functions are not the most appropriate for estimating turbulent fluxes in the region immediately above the forest canopy. (ii) The Amazonian nocturnal boundary layer is often populated by submeso phenomena, which create episodes of intermittent turbulence and increase the complexity of exchange processes between the forest and the atmosphere during the night. (iii) Above the Amazonian RSL, it was possible to verify that there is no evidence of a classic inertial layer. Since July 2021, the ATTO (Amazon Tall Tower Observatory) tower has been performing continuous measurements, carried out by nineteen 3D-sonic installed from 5 m (inside the forest canopy) to 316 m (above the RSL). Therefore, in this work we will show the profiles of different turbulent fluxes measured since mid-2021 under different stability conditions and at different periods of the year (dry and rainy season). These new measurement profiles, with high vertical resolution, are unique and they will allow us to understand the turbulent exchange processes in regions of the Amazon planetary boundary layer that have not been previously explored.

 

 

 

 

How to cite: Dias-Junior, C. Q., Dias, N., Acevedo, O., Mortarini, L., Brondani, D., Oliveira, P., Araújo, A., Oliveira, L., Ferreira, R., Acosta, R., Takeshi, B., and Quesada, C. A.: Turbulent Fluxes Within and Above the Amazon Roughness Sublayer, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10412, https://doi.org/10.5194/egusphere-egu23-10412, 2023.

EGU23-10522 | Posters on site | BG1.6

Unique Tall Tower Greenhouse Gas Measurements in the Amazon Rainforest: observed patterns and daily cycles 

Hella van Asperen, Shujiro Komiya, Sam Jones, Santiago Botia, Jost Lavric, Thorsten Warneke, David Griffith, and Susan Trumbore

The ATTO (Amazon Tall Tower Observatory) tower is a 325m tall tower located in the middle of the pristine Amazon rainforest. Since 2022, continuous greenhouse gas concentrations at different heights (4m, 42m, 81m, 150m, 273m, 321m) are monitored by use of a Spectronus FTIR-spectrometer, measuring CO2, CH4, CO, N2O and del13CO2 hourly, compliant to WMO/GAW standards. This unique measurement system is the first set up which measures greenhouse gases continuously until 325m above a tropical rainforest, which fill an important gap in the global continous observation network. The measurements can be used for regional and global modelling, and can be used for biosphere-atmosphere exchange flux estimates. In this presentation, we will show the main observations of the first year of data collection, and will present the typical daily cycles observed for the different gases at different heights.

How to cite: van Asperen, H., Komiya, S., Jones, S., Botia, S., Lavric, J., Warneke, T., Griffith, D., and Trumbore, S.: Unique Tall Tower Greenhouse Gas Measurements in the Amazon Rainforest: observed patterns and daily cycles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10522, https://doi.org/10.5194/egusphere-egu23-10522, 2023.

EGU23-10954 | Posters on site | BG1.6

Continuous water vapor isotope measurements at the Amazon Tall Tower Observatory site during a dry season: Insights into diel atmospheric moisture sources 

Shujiro Komiya, Sam Jones, Hella van Asperen, Jost Lavric, Getachew Adnew, Robbert Moonen, Santiago Botia, Cléo Quaresma Dias-Júnior, Ricardo Acosta Gotuzzo, Rosaria Rodrigues Ferreira, Fumiyoshi Kondo, and Susan Trumbore

The recent development and improvement of commercially available laser-based spectrometers have expanded onsite continuous water vapor (H2O) stable isotope composition (e.g. δ18O, δ17O and δ2H) measurements in a variety of sites across the world in the last decade. However, we still lack continuous observations in the Amazon basin region, a region that significantly influences atmospheric and hydrological cycles on local to global scales.

The Amazon Tall Tower Observatory (ATTO) site is located in well-preserved central Amazon upland rainforest. In August 2022, a commercial cavity-ring down (CRDS) analyzer (L2140-i model, Picarro, Inc., USA) was installed to continuously measure water vapor isotope compositions at four levels (79, 38, 24, and 4 m above ground) of the 80 m walk-up tower. Also, deuterium excess (hereinafter called d-excess; d-excess = δ2H–8δ18O) was assessed to trace processes that contribute to diel variation in atmospheric moisture inside and above canopy.

During the dry season, d-excess generally decreased during the nighttime, reaching minimum values at 6 am to 8 am local time (LT), followed by an increase to maximum values at 12 pm to 4 pm. The diel d-excess variation indicates that atmospheric entrainment occurred in the early morning and evapotranspiration was a dominant moisture source in the afternoon. Further results will be analyzed and discussed in the presentation.  

How to cite: Komiya, S., Jones, S., van Asperen, H., Lavric, J., Adnew, G., Moonen, R., Botia, S., Quaresma Dias-Júnior, C., Acosta Gotuzzo, R., Rodrigues Ferreira, R., Kondo, F., and Trumbore, S.: Continuous water vapor isotope measurements at the Amazon Tall Tower Observatory site during a dry season: Insights into diel atmospheric moisture sources, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10954, https://doi.org/10.5194/egusphere-egu23-10954, 2023.

EGU23-11005 | ECS | Orals | BG1.6 | Highlight

Regional ecotypes structure biogeography of Amazon forest drought resilience and vulnerability 

Shuli Chen, Scott Stark, Antonio Nobre, Luz Cuartas, Diogo Amore, Natalia Restrepo-Coupe, Marielle Smith, Rutuja Chitra-Tarak, Hongseok Ko, Bruce Nelson, and Scott Saleska

Amazonia contains the most extensive tropical forests on Earth, but the role of the region as a carbon appears to be declining. Increasing deforestation, fire and climate change-associated increases in drought, threaten to push forests past a tipping point. However, forests are complex, exhibiting drought responses indicative of both resilience (photosynthetic “greening”) and vulnerability (browning and tree mortality) that are difficult to explain by climate variation alone. Still needed is a framework for understanding and predicting how different regions will respond to different kinds of future drought. Here, we combine remotely-sensed photosynthetic vegetation indices (enhanced vegetation index, EVI, corrected for sun-sensor geometry; and solar-induced chlorophyll fluorescence, SIF) with ground-based tree demography to test recent ecological hypotheses about forest drought resilience and vulnerability for different forest ecotypes across the basin, defined by their water-table depth, soil fertility and vegetation characteristics. In high-fertility southern Amazonia, drought response was importantly structured by water-table depth, with resilient greening in shallow-water-table-forests (where greater water availability heightened responsiveness to excess sunlight) contrasting with vulnerability (“browning” and excess tree mortality) over deeper water tables. Notably, shallow-water-table-forest resilience weakened as droughts lengthened. By contrast, low-fertility northern Amazonia, with slower-growing but drought-hardy trees (or tall trees, with deep-rooted water access), supported more drought-resilient forests independent of water-table depth. This work reveals a new biogeography of forest drought response that provides a framework for conservation decisions and improved prediction of heterogeneous forest responses to future climate changes, but warns that longer/more frequent droughts undermine these multiple ecohydrological strategies of Amazon forest resilience.

How to cite: Chen, S., Stark, S., Nobre, A., Cuartas, L., Amore, D., Restrepo-Coupe, N., Smith, M., Chitra-Tarak, R., Ko, H., Nelson, B., and Saleska, S.: Regional ecotypes structure biogeography of Amazon forest drought resilience and vulnerability, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11005, https://doi.org/10.5194/egusphere-egu23-11005, 2023.

EGU23-11140 | Posters on site | BG1.6

Modelling soil phosphorus cycle feedbacks in old-growth and regrowing tropical forests in Amazonia 

Katrin Fleischer, Lin Yu, Lucia Fuchslueger, Carlos A. Quesada, and Sönke Zaehle

Soil nutrient availability is a key constraint on tropical forest growth. On highly weathered soils, intact forests' carbon-nutrient cycles have developed over pedogenic time scales, leading to tight nutrient cycling of some depleted elements, such as phosphorus. Ecosystem nutrient recycling and plant nutrient limitation are predominant in lowland Amazonia, controlling the forests' response to disturbance and climate change. Deforestation, biomass removal, and fire lead to the loss of carbon and nutrients previously stored in vegetation, potentially enforcing nutrient limitation and reducing carbon storage in regrowing forests.   

Here, we employ the process-based terrestrial biosphere model QUINCY (Thum et al., 2019), coupled with the microbial-explicit soil model JSM (Yu et al., 2020) to simulate carbon and nutrient cycling rates at intact Amazonian forest sites, which span a natural gradient of 30 to 727 mg phosphorus g dry soil-1, and from 2 to 81% clay. The model QUINCY-JSM accounts for dynamic plant carbon investment in growth and nutrient acquisition, and microbial-explicit growth, turnover, and nutrient cycling. We confront the ecosystems with historical changes in atmospheric CO2 and climate, and simulate an experimental harvest of the entire forest stand to assess the consequences of that nutrient loss on the regrowing forest stand. Simulations of the Amazon forest sites are in good agreement with forest census data on vegetation carbon dynamics. Biologically-driven nutrient mineralization represents the main source of nutrients for plants, with negligible contribution of inorganic nutrient cycling in highly weathered sites. After experimental deforestation, we find that the inorganic nutrient supply is insufficient and restricts forest growth, leading to lower vegetation biomass equilibrium after deforestation. Our simulations suggest that forest degradation may occur through biomass removal in tropical forests.

Thum, T., Caldararu, S., Engel, J., Kern, M., Pallandt, M., Schnur, R., et al. (2019). A new model of the coupled carbon, nitrogen, and phosphorus cycles in the terrestrial biosphere (QUINCY v1.0; revision 1996). Geoscientific Model Development, 12(11), 4781–4802. https://doi.org/10.5194/gmd-12-4781-2019

Yu, L., Ahrens, B., Wutzler, T., Schrumpf, M., & Zaehle, S. (2020). Jena Soil Model (JSM v1.0; Revision 1934): A microbial soil organic carbon model integrated with nitrogen and phosphorus processes. Geoscientific Model Development, 13(2), 783–803. https://doi.org/10.5194/gmd-13-783-2020

How to cite: Fleischer, K., Yu, L., Fuchslueger, L., Quesada, C. A., and Zaehle, S.: Modelling soil phosphorus cycle feedbacks in old-growth and regrowing tropical forests in Amazonia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11140, https://doi.org/10.5194/egusphere-egu23-11140, 2023.

EGU23-11315 | ECS | Orals | BG1.6

Creating virtual forests to understand fragmentation in tropical ecosystems 

Eleanor Downie, Rico Fischer, Nikolai Knapp, Erone Ghizoni Santos, Fabian Fassnacht, José Luis Camargo, Ana Andrade, and Eduardo Maeda

The study of forest fragmentation, the break-up of forests into smaller patches, has become increasingly important due to increases in human-induced forest clearance, with 12 million hectares of forest being lost per year and 32% of this loss being tropical. There is substantial evidence showing that edge effects can alter the ecology structure and vertical profile of remaining forests, even hundreds of meters from the forest edge.  However, implementing empirical experiments (for example in the framework of the Biological Dynamics of Forest Fragments Project (BDFFP)) to understand the effects of fragmentation on forest structural traits can be logistically and scientifically challenging and limited to smaller areas.  The use of forest models may help overcome these limitations, as they are able to quickly reproduce long-term data, as well as simulate a broad range of geographical conditions. This study aimed to reproduce the vertical distribution of plants in Amazonian forests affected by fragmentation using the forest model FORMIND. To achieve this, we optimized parameters driving plant demography and mortality, as well as their response to edge effects. FORMIND is an individual and process-based gap model suited for species rich vegetation communities, with the option of a fragmentation module. We modified processes and parameters in FORMIND to mimic the dynamics observed in the BDFFP experiment. Forest structural traits extracted from the FORMIND model output were compared with those obtained from terrestrial laser scans of the BDFFP fragments. The resulting simulations demonstrated that, after 40 years of edge effects, the optimized model was able to reproduce similar results to those observed using the terrestrial LiDAR system. Total plant area index (PAI), and PAI at varying height intervals (PAI 0-10m, PAI 10-20m, PAI 20-30m), showed consistent responses from edge effects, thus resulting in an adequate vertical plant distribution. Results demonstrate that, forest models such as FORMIND have strong potential to study the mechanisms and the impact of environmental changes on forests. Models can also expand the possibilities of in-situ studies, which are limited in time and space, when calibrated carefully with suitable in-situ data, here delivered by terrestrial LiDAR.

How to cite: Downie, E., Fischer, R., Knapp, N., Ghizoni Santos, E., Fassnacht, F., Camargo, J. L., Andrade, A., and Maeda, E.: Creating virtual forests to understand fragmentation in tropical ecosystems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11315, https://doi.org/10.5194/egusphere-egu23-11315, 2023.

EGU23-11338 | Orals | BG1.6 | Highlight

AmazonFACE: A Free Air CO2 Enrichment Experiment in the Amazon rainforest is ready to launch 

Rammig Anja and Lapola David and the AmazonFACE Team

Atmospheric CO2 concentrations are still rising due to land-use change and fossil fuel burning, and have unambiguously influenced Earth’s climate system and terrestrial ecosystems. Plant responses to rising atmospheric CO2 concentrations may have induced an increase in biomass and thus, increased the carbon sink in forests worldwide. Rising CO2 directly stimulates photosynthesis (the so-called CO2-fertilization effect) and tends to reduce stomatal conductance, leading to enhanced water-use efficiency, which may provide an important buffering effect for plants during adverse climate conditions. For these reasons, current global climate simulations consistently predict that tropical forests will continue to sequester more carbon in aboveground biomass. However, several lines of evidence point towards a decreasing carbon sink strength of the Amazon rainforest in the coming decades, potentially driven by nutrient limitation, droughts or other factors. Mechanistically modelling the effects of rising CO2 in the Amazon rainforest are hindered by a lack of direct observations from ecosystem scale CO2 experiments. To address these critical issues, we are currently building a free-air CO2 enrichment (FACE) experiment in an old-growth, highly diverse, tropical forest in the Brazilian Amazon and we here present our main hypotheses that underpin the AmazonFACE experiment.  We focus on possible effects of rising CO2 on carbon uptake and allocation, phosphorus cycling, water-use and plant-herbivore interactions, and discuss relevant ecophysiological processes, which need to be implemented in dynamic vegetation models to estimate future changes of the Amazon carbon sink. We also report on baseline measurements at the AmazonFACE site and show the progress on model development with regard to phosphorus uptake strategies.

How to cite: Anja, R. and David, L. and the AmazonFACE Team: AmazonFACE: A Free Air CO2 Enrichment Experiment in the Amazon rainforest is ready to launch, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11338, https://doi.org/10.5194/egusphere-egu23-11338, 2023.

EGU23-14926 | Orals | BG1.6

Topography influence on turbulent profiles over the ATTO site 

Raissa de Oliveira, Daiane Brondani, Luca Mortarini, Umberto Giostra, Eliane Alves, Carlos Alberto Quesada, and Cléo Quaresma Dias-Junior

The spatial representativeness of anemometric tower measurements and the underlying hypothesis of horizontal homogeneity of the atmospheric flows have long being questioned in the literature. Further, forest are rarely situated on uniform and flat terrain in which the horizontally homogeneity of turbulence holds. The orography around the Amazon Tall Tower Observatory (ATTO) site makes no exception. The measurement site is located on a narrow plateau SW-NE oriented, surrounded by lower hills. It is then natural to investigate the spatial variability of the turbulent field around the ATTO and the INSTANT towers to understand the role played by gentle topography. The Parallelized Large-Eddy Simulation Model (PALM) is used to simulate the atmospheric flow over the Amazon Forest and to investigate the effect of topography on the Atmospheric flow within and above the roughness sublayer. The real topography of the ATTO site is considered, while a horizontally homogeneous leaf area density (LAD) profile is assumed for the canopy over the whole area. Hence, the flow variability can be totally ascribed to spatial orography gradients. The influence of orography is assessed comparing the profiles of the turbulent kinetic energy components and fluxes evaluate over flat terrain and over the real topography at different position on the horizontal plane. The dependence of the orography influence on the wind direction is investigated considering two different wind directions.

 

How to cite: de Oliveira, R., Brondani, D., Mortarini, L., Giostra, U., Alves, E., Quesada, C. A., and Dias-Junior, C. Q.: Topography influence on turbulent profiles over the ATTO site, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14926, https://doi.org/10.5194/egusphere-egu23-14926, 2023.

EGU23-16898 | Posters on site | BG1.6

Rainfall-Particle Feedback in the Amazon Forest 

Luiz Augusto Toledo Machado and the Gabriela R. Unfer, Christopher Pohlker , Jonathan Williams, Harder Hartwig, Meinrat O. Andreae, Paulo Artaxo, Yafang Cheng, Joachim Curtius, Marco A. Franco, Micael A. Cecchini, Achim Edtbauer, Bruna Holanda, Leslie A. Kremper, Bruno B. Meller, Eva Pfanne

 Atmospheric aerosol particles are essential for the formation of clouds and precipitation, thereby impacting
the global energy budget and the water cycle. However, particle production in pristine environments like the
Amazon rainforests are not yet well understood. New particle formation can occur in the outflow of high
convective clouds and be transported downward (top-down) or they may form and grow from oxidized
biogenic volatile organic compounds at low altitudes before entering the largescale vertical circulation
(bottom-up). In this study, we examine a comprehensive measurement dataset of aerosols, trace gases,
and meteorological parameters to examine new particle formation and growth in the Amazon rainforest.
The results reveal that rain events are important not only for the downdraft of particles from aloft but
also for the injection of ozone into the forest canopy. While near-ground particle enhancements by
downdrafts were modest, .another less frequent but more efficient process acted to increase sub-40 nm
particle concentrations nearly one hour after the maximum precipitation. This phenomenon occurs due to
downdrafts of ozone-rich air entering the canopy containing reactive organic species and initiating particle
production. Particularly on days when the previous night has a high ozone concentration, these particles
grow in the early morning to form cloud condensation nuclei in the early afternoon
 

How to cite: Toledo Machado, L. A. and the Gabriela R. Unfer, Christopher Pohlker , Jonathan Williams, Harder Hartwig, Meinrat O. Andreae, Paulo Artaxo, Yafang Cheng, Joachim Curtius, Marco A. Franco, Micael A. Cecchini, Achim Edtbauer, Bruna Holanda, Leslie A. Kremper, Bruno B. Meller, Eva Pfanne: Rainfall-Particle Feedback in the Amazon Forest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16898, https://doi.org/10.5194/egusphere-egu23-16898, 2023.

EGU23-16945 | ECS | Posters on site | BG1.6

Wet deposition of sub-micron aerosol particles in an urban area of the Amazon central 

Glauber Cirino, Márcio Matheus, Henrique Barbosa, Courtney Schumacher, Aaron Funk, Joel Brito, Luciana Rizzo, Rafael Palácios, Simone Silva, Breno Imbiriba, Jost Lavric, Scot Martin, and Paulo Artaxo

Aerosol particles impact health, ecosystems, and climate, especially when in high concentrations in urban environments. Wet deposition is one of the most critical limiting mechanisms of particulate matter in the atmosphere.  This mechanism captures particles inside clouds (rain-out) or below the cloud due to precipitation (washout). In the Amazon basin, the physical mechanisms and scavenging rates remain unknown in many regions. Several studies over the last decades have empirically ascertained the impact of wet deposition to develop local atmospheric models or to estimate the contribution of its effects. Here, we analyzed some of the physical and chemical properties of aerosols: nucleation mode (NU, 10-30 nm), Aitken (30-100 nm), accumulation mode (AC, 100-430 nm), total particle number (10-430 nm), Black Carbon equivalent (BCe), and chemical properties, such as organic aerosols (OA), sulfate (SO42−) and nitrate (NO3). We obtained the data set from the Intensive Observation Periods (IOPs) of the GoAmazon2014 experiment, Iranduba-AM (T2 sampling site), ~ 9 km NE of Manaus city. We conducted three analyzes from these data: (I) daily cycles on dry and rainy days; (II) scavenging rates (TS), i.e., the difference in the concentration of aerosol one hour before and the first hour of rainfall events, generally, during local thunderstorms or Mesoscale Convective Systems - MCS; and (III) scavenging coefficients (λ). We verified significant statistics decreases at both NU and AIT modes, as well SO42− and NO3. In TS analysis, we observed a similar decline (NU: -21%, AIT: -17%, AC: -22%), contributing to an overall removal of up to -13% (on average). The soluble fractions were removed easily (OA: -21%, SO42−: -16%, and NO3: -16%) compared to insoluble fractions (BCe: -11%). In λ analysis, a substantial decrease in all size classes (NU: 2.0 × 10−4 s−1, AIT: 7.8 × 10−4 s−1, AC: 1.3 × 10−4 s−1, CN: 5.4 × 10−4 s−1) was also observed, with unexpected prominence to the AIT. We've attributed this result to introducing aerosol particles of 10-50 nm by deep convection, which may counteract the washout. Measurements of cloud properties might help confirm this hypothesis. Our preliminary findings are helpful for the local modeling of pollutant dynamics and provide evidence that wet deposition substantially removes sub-micron particles in the Amazon region. The wet deposition rates for other storms and clouds in the atmosphere, however, remain unknown.

How to cite: Cirino, G., Matheus, M., Barbosa, H., Schumacher, C., Funk, A., Brito, J., Rizzo, L., Palácios, R., Silva, S., Imbiriba, B., Lavric, J., Martin, S., and Artaxo, P.: Wet deposition of sub-micron aerosol particles in an urban area of the Amazon central, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16945, https://doi.org/10.5194/egusphere-egu23-16945, 2023.

EGU23-17108 | Orals | BG1.6

Forest conversion cuts off biogeochemical connections of the subsoil to the top 

Simone Kilian Salas, Alberto Andrino, Elisa Díaz García, Diana Boy, Marcus A. Horn, Jens Boy, Georg Guggenberger, and Hermann F. Jungkunst

Losses in above- and belowground biodiversity are linked to changes in land use practices and immediately affect processes in the upper soil horizons. Theoretically, these superficial changes are reversible unless a tipping point on an ecosystem level was crossed. This safety net of functional redundancy facilitates the return of vital soil functions and processes to the initial state. Little is known about how deep these changes have reached into the subsoil over time, because early warning indicators of a tipping point being about to be crossed are still sparse. This is especially important for the tropics, as soils are typically intensively weathered and nutrient depleted, therefore, plants relying largely on nutrients from below. Net nitrous oxide (N2O) emission rates from the soil surface have proved to be valid proxies for detecting the crossing of tipping points in soil biogeochemistry. Here, we advanced this approach by looking deeply into the soil and reveal that potential greenhouse gas (GHG) production and consumption are useful proxies to estimate how deep the loss of aboveground biodiversity has already impacted soil microbial processes. We performed incubation experiments on forest and pasture soils stemming from shallow as well as 1 m deep profiles from the Peruvian Amazon Basin to determine the production and consumption potential of the GHGs at different water holding capacities. We expected pasture soils to have lost direct carbon(C)-related connections to deeper soil horizons. In forests, roots with different and greater depths also connect deeper soil layers. Therefore, in greater depth, carbon dioxide (CO2) production declined faster under pastures than under forests because C limitations are reached sooner. In the surface, grasses are well known for their input of C and increased CO2 production. Since old pastures are limited in nitrogen (N), almost no N2O should be produced, possibly increasing the potential to take up N2O. However, denitrification is a heterotrophic process also dependent on available C, therefore, the potentials of N2O production and consumption in deeper forest soils were larger with increasing water holding capacity. These findings could indicate that losses in aboveground biodiversity due to forest conversion can have profound impacts on soil microbial processes, extending also to deeper soil layers while altering the connection of the subsoil to the top.

How to cite: Kilian Salas, S., Andrino, A., Díaz García, E., Boy, D., Horn, M. A., Boy, J., Guggenberger, G., and Jungkunst, H. F.: Forest conversion cuts off biogeochemical connections of the subsoil to the top, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17108, https://doi.org/10.5194/egusphere-egu23-17108, 2023.

EGU23-17534 | ECS | Posters on site | BG1.6

Effects of deforestation events on atmospheric dynamics using Lagrangian reanalysis data 

Lucie Bakels, Silvia Bucci, and Andreas Stohl

Deforestation in the Amazon basin has the potential to affect regional atmospheric circulations, possibly causing changes in the moisture transport by altering the regional Hadley and Walker cells (Zhang et al.1996). Previous studies that modelled the atmosphere under different extreme deforestation scenarios have shown that deforestation in the Amazon basin could increase the length and frequency of dry seasons in the Southern Amazon, while an increase of rain is expected in the Northern Amazon (e.g. Espinoza et al., 2019; Ruiz-Vasquez et al., 2020). Beyond climate models, it is also possible to trace the effect of past deforestation on the atmosphere using a Lagrangian transport model applied on atmospheric reanalysis data. Using the FLEXPART global simulations on the ERA-5 ECMWF reanalysis dataset (1959-2022), we are able to track air parcels through time and space, making it possible to locate the origin of moisture and latent heat, and quantify how global atmospheric circulation is affected by air transport from deforested areas.

How to cite: Bakels, L., Bucci, S., and Stohl, A.: Effects of deforestation events on atmospheric dynamics using Lagrangian reanalysis data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17534, https://doi.org/10.5194/egusphere-egu23-17534, 2023.

EGU23-606 | Orals | BG1.7

The African greenhouse gases budget: flux trends and uncertainties for the 2009-2019 period 

Yolandi Ernst and Sally Archibald and the RECCAP2 Africa team

Africa contributes significantly to the global greenhouse gases (GHG) budget through extensive land use change that is driven by rapid population growth and low human development status. As part of the REgional Carbon Cycle Assessment and Processes Phase 2 (RECCAP2) project, we developed a comprehensive GHG budget for the period 2009-2019 for Africa. We considered bottom-up process-based models, data-driven remotely sensed products, and national greenhouse gas inventories in comparison with top-down atmospheric inversions, accounting also for lateral fluxes. We incorporated emission estimates derived from novel methodologies for termites, herbivores, and fire, which are of particular importance in Africa. We further constrained global biomass change products with high-quality local observation data. During the RECCAP2 period, Africa remains a net sink for carbon. Emissions from land cover change represents the largest contribution to the African budget. However, land cover change emissions in the drier savanna regions were largely offset by increased vegetation growth in the wet tropics. Additionally, fire emissions decreased as suggested by strong reductions in burned area. Burning of fuelwood has however increased. As expected, an upward trend in anthropogenic fossil fuel emissions was evident, ascribed to an increasing demand for energy by a growing and developing population. For all the component fluxes, uncertainty and interannual variability is large, which highlights the need for increased efforts to address Africa-specific data gaps. However, for RECCAP2, we have improved our overall understanding of many of the important components of the African GHG budget that will help to inform climate policy and action.

How to cite: Ernst, Y. and Archibald, S. and the RECCAP2 Africa team: The African greenhouse gases budget: flux trends and uncertainties for the 2009-2019 period, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-606, https://doi.org/10.5194/egusphere-egu23-606, 2023.

EGU23-1333 | Orals | BG1.7

Synthesis, homogenisation and regionalisation of inland water greenhouse gas budget estimates for the RECCAP2 initiative 

Ronny Lauerwald, George H. Allen, Bridget R. Deemer, Shaoda Liu, Taylor Maavara, Pete Raymond, Lewis Alcott, David Bastviken, Adam Hastie, Meredith A. Holgerson, Matthew S. Johnson, Bernhard Lehner, Peirong Lin, Alessandra Marzadri, Lishan Ran, Hanqin Tian, Xiao Yang, Yuanzhi Yao, and Pierre Regnier

Inland waters are important sources of the greenhouse gasses (GHGs) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) to the atmosphere. While a growing number of global estimates of inland water GHG emissions exists, the integration of inland waters into regional GHG budgets is often hampered by the lack of adequate geo-spatial datasets. Moreover, existing estimates diverge substantially, in part due to persisting uncertainties related to the size and distribution of effective inland water surface areas.  In the framework of the 2nd phase of the REgional Carbon Cycle Assessment and Processes (RECCAP-2) initiative, we synthesize existing estimates of GHG emissions from streams, rivers, lakes and reservoirs, and homogenize them with regard to underlying global maps of inland water surface areas and the effects of seasonal ice cover. We then produce estimates of inland water GHG emissions for 10 extensive land regions that are used for the regional land budgets of RECCAP2. According to our synthesis, global inland waters emit 5.6 (3.5-9.1) Pg CO2 yr-1, 101 (83-135) Tg CH4 yr-1 and 326 (254-592) Gg N2O yr-1. South American rivers contribute about one third of global inland water CO2 emissions. North-American and Russian lakes contribute together one third of global inland water CH4 emissions. Finally, North America alone contributes one fourth of global inland water N2O emissions.

The global inland water emissions sum up to a global warming potential (GWP) of an equivalent emission of 13.6 (10.0-20.3) and 8.3 (5.8-12.7) Pg CO2 yr-1 at a 20- and 100-year horizon, respectively. At 100-year horizon, the contribution of CO2 dominates the GWP of global inland water GHG emissions, with rivers being the largest emitters. At the 20-year horizon, on the contrary, lakes and rivers are equally important emitters, and the contributions of CH4 to the GWP of inland water GHG emissions even exceed those of CO2. Contributions of N2O to the GWP appear to be less significant at both time horizons. Normalized to the area of the RECCAP-2 land regions, South America and South East Asia show the highest inland water emission rates in terms of GWP, dominated by riverine CO2 emissions.

How to cite: Lauerwald, R., Allen, G. H., Deemer, B. R., Liu, S., Maavara, T., Raymond, P., Alcott, L., Bastviken, D., Hastie, A., Holgerson, M. A., Johnson, M. S., Lehner, B., Lin, P., Marzadri, A., Ran, L., Tian, H., Yang, X., Yao, Y., and Regnier, P.: Synthesis, homogenisation and regionalisation of inland water greenhouse gas budget estimates for the RECCAP2 initiative, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1333, https://doi.org/10.5194/egusphere-egu23-1333, 2023.

EGU23-1609 | Posters on site | BG1.7

The Qinghai-Tibet Plateau may have already shifted to carbon source: Evidence from OCO-2 satellite XCO2 observations 

Wei He, Fei Jiang, Weimin Ju, Hengmao Wang, Ngoc Tu Nguyen, and Jing M. Chen

As one of the most sensitive regions to climate change on the Earth's surface, the Qinghai-Tibet Plateau is experiencing lasting warming, which has been evidenced to enhance surface carbon uptake but also could lead to carbon emission due to accelerated permafrost degradation and ecosystem respiration. Due to the difficulties of limited observations and imperfect modeling techniques, whether the Qinghai-Tibet Plateau is a carbon sink or source has been an ongoing debate. The recent satellite XCO2 Observations could provide some useful constraints on the carbon budget in this region.  Here, based on the recent OCO-2 XCO2 observations and the inversion results from the OCO-2 v10 MIP, we estimated the net biome carbon fluxes for the Qinghai-Tibet Plateau. Our results suggest that this region has become a carbon source (around -0.10 PgC/year) already, which is supported by an upscaling estimate with intensified eddy covariance flux measurements over China. Meanwhile, we found this carbon source signal is not detected by either in-situ CO2 inversions or terrestrial biosphere model simulations. Currently, although some studies based on flux measurements report this region is a carbon sink and even keeps increasing recently, many others hold opposite viewpoints about it. Our result provides an important piece of evidence supporting that the Qinghai-Tibet Plateau becomes a carbon source, albeit additional evidence is needed, especially from in-situ CO2 observations and aerial CO2 observations (e.g., by aircraft, unmanned aerial vehicle, and AirCore). In principle, atmospheric CO2 measurements could provide a more complete picture of the carbon budget in this region compared to discrete and limited eddy flux measurements. In the future, enhanced in-situ and aerial CO2 observations are expected to disentangle the puzzle of this carbon budget issue in this region.

How to cite: He, W., Jiang, F., Ju, W., Wang, H., Nguyen, N. T., and Chen, J. M.: The Qinghai-Tibet Plateau may have already shifted to carbon source: Evidence from OCO-2 satellite XCO2 observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1609, https://doi.org/10.5194/egusphere-egu23-1609, 2023.

EGU23-2813 | ECS | Orals | BG1.7

Is destabilisation risk increasing in land carbon sinks? 

Marcos Fernández-Martínez, Josep Peñuelas, Frederic Chevallier, Philippe Ciais, Michael Obersteiner, Christian Rödenbeck, Jordi Sardans, Sara Vicca, Hui Yang, Stephen Sitch, Pierre Friedlingstein, Vivek K. Arora, Daniel Goll, Atul K. Jain, Danica L. Lombardozzi, and Patrick C. McGuire

Global net biome production (NBP), or net land carbon uptake, has been repeatedly shown to increase during recent decades. However, whether the temporal variability and autocorrelation of NBP has changed during this period remains elusive. Answering this question is particularly relevant given that an increase in both could indicate destabilising C sinks and potentially lead to abrupt changes. We investigated the trends and controls of net land C uptake and its temporal variability and autocorrelation, from 1981 to 2018, using two atmospheric inversion models, the amplitude of the seasonal cycle of atmospheric CO2 derived from nine monitoring stations distributed across the Pacific Ocean, and 12 dynamic global vegetation models. Spatially, we found that plant biodiversity presented a convex parabolic relationship with NBP and its temporal variability at the global scale while nitrogen deposition generally increased annual NBP. We also found that annual NBP and its interdecadal temporal variability globally increased, but temporal autocorrelation decreased. Regions characterized by increasingly variable NBP were usually with warmer and with increasingly variable temperatures, and lower and weaker trends in NBP compared to those where NBP variability did not increase, where NBP became stronger. Annual temperature increase and its increasing temporal variability were the most important drivers of declining NBP and increasingly its variability. Our results show that increasing regional NBP variability can be mostly attributed to climate change.

How to cite: Fernández-Martínez, M., Peñuelas, J., Chevallier, F., Ciais, P., Obersteiner, M., Rödenbeck, C., Sardans, J., Vicca, S., Yang, H., Sitch, S., Friedlingstein, P., Arora, V. K., Goll, D., Jain, A. K., Lombardozzi, D. L., and McGuire, P. C.: Is destabilisation risk increasing in land carbon sinks?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2813, https://doi.org/10.5194/egusphere-egu23-2813, 2023.

EGU23-3228 | ECS | Orals | BG1.7 | Highlight

The contemporary Amazon Forest carbon budget 

Thais M. Rosan, Stephen Sitch, Michael O’Sullivan, Christopher Wilson, Luana S. Basso, Dominic Fawcett, Viola A. Heinrich, Jefferson G. Souza, Celso von Randow, Lina M. Mercado, Emanuel Gloor, Luciana Gatti, Pierre Friedlingstein, Andy Wiltshire, Julia Pongratz, Clemens Schwingshackl, and Luiz E.O.C. Aragão and the TRENDY-v11 Team

The Amazon is the largest continuous tropical forest in the world and plays a key role in the global carbon cycle. Human-induced disturbances (e.g., deforestation and wildfires) in combination with climate change have impacted its carbon cycling. However, uncertainties remain on the magnitude of carbon fluxes associated with human-induced disturbances and the old-growth forest sink, and thus the net land carbon balance of the Amazon. Here we synthesize state-of-the-art estimates of the land carbon flux components in the Amazon. To quantify the human-disturbance fluxes from deforestation, land use and land cover changes and degradation, we use a set of bookkeeping models. The annual intact sink was quantified using a set of 16 Dynamic Global Vegetation Models (DGVMs). We then combine the carbon flux estimates from disturbances with the intact sink estimates to provide a bottom-up estimate of the net land carbon flux and compare them alongside top-down estimates from atmospheric model inversions. Between 2010 and 2018, the net land carbon flux in the Brazilian Amazon estimated with the bottom-up approach was -59 (±160) Tg C yr-1 and +36 (±125) Tg C yr-1 with the top-down approach. Despite disagreeing on the sign of the flux, this analysis suggests that the Brazilian Amazon was on average near carbon neutral over the 2010-2018 period, given the large uncertainties underlying both methods. The net land carbon fluxes for the years 2019 and 2020 based on the bottom-up approach were larger than for 2010-2018. This is likely primarily due to direct emissions related to an increase in deforestation although it may possibly be partly caused by a weakening of the forest carbon sink, both in response to deforestation and a warming climate. Spatially, both methodologies agree that the south-eastern Amazon was a net carbon source over the whole study period. These results have important implications for the mitigation potential of Brazilian ecosystems within the goals of the Paris Agreement. 

 

How to cite: Rosan, T. M., Sitch, S., O’Sullivan, M., Wilson, C., Basso, L. S., Fawcett, D., Heinrich, V. A., Souza, J. G., von Randow, C., Mercado, L. M., Gloor, E., Gatti, L., Friedlingstein, P., Wiltshire, A., Pongratz, J., Schwingshackl, C., and Aragão, L. E. O. C. and the TRENDY-v11 Team: The contemporary Amazon Forest carbon budget, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3228, https://doi.org/10.5194/egusphere-egu23-3228, 2023.

EGU23-3303 | ECS | Orals | BG1.7

Near-real-time global gridded daily CO2 emissions 

Xinyu Dou, Zhu Liu, Philippe Ciais, Jinpyo Hong, Frédéric Chevallier, Yilong Wang, Feifan Yan, Steven J. Davis, Monica Crippa, Greet Janssens-Maenhout, Diego Guizzardi, Efisio Solazzo, Xuanren Song, Da Huo, Piyu Ke, Hengqi Wang, and Zhu Deng

Timely, fine-grained gridded carbon emission datasets are particularly important for global climate change research. Often, fine-grained datasets are challenging to visualize over the globe, and clear visualization tools are also needed. Therefore, we present a near-real-time global gridded daily CO2 emissions dataset (GRACED). GRACED provides gridded CO2 emissions at a 0.1° × 0.1° spatial resolution and 1-day temporal resolution from cement production and fossil fuel combustion over seven sectors, including power, industry, residential consumption, ground transportation, domestic aviation, international aviation, and international shipping. GRACED is prepared from the near-real-time daily national CO2 emissions estimates (Carbon Monitor), multi-source spatial activity data and satellite NO2 data for time variations of those spatial activity data. Here, we examined the spatial patterns of sectoral CO2 emission changes from January 1, 2019, to December 31, 2021. In 2021, most regions showed rapid rebounds in carbon emissions compared with 2020, reflecting the continuing challenges to accelerate climate mitigation in the post-COVID era. GRACED provides the most timely and more refined overview than any other previously published datasets, which enables more accurate and timely identification of when and where fossil CO2 emissions have rebounded and decreased as the world recovers from COVID-19 and witnesses contrasted efforts to decarbonize energy systems. Uncertainty analysis of GRACED gives a grid-level two-sigma uncertainty of value of ±19.9%, indicating the reliability of GRACED was not sacrificed for the sake of higher spatiotemporal resolution that GRACED provides. In addition, we also examined the distribution of emission in a grid-wise perspective for major emission datasets, and compared it with GRACED. The similarity in emission distribution was observed in GRACED and other datasets. One of the advantages of our dataset is that it provides worldwide near-real-time monitoring of CO2 emissions with different fine spatial scales at the sub-national level, such as cities, thus enhancing our comprehension of spatial and temporal changes in CO2 emissions and anthropogenic activities. With the continued extension of GRACED time series, we present crucial daily-level input to analyze CO2 emission changes in the post-COVID era, which will ultimately facilitate and aid in designing more localized and adaptive management policies for the purpose of climate change mitigation in the post-COVID era.

How to cite: Dou, X., Liu, Z., Ciais, P., Hong, J., Chevallier, F., Wang, Y., Yan, F., Davis, S. J., Crippa, M., Janssens-Maenhout, G., Guizzardi, D., Solazzo, E., Song, X., Huo, D., Ke, P., Wang, H., and Deng, Z.: Near-real-time global gridded daily CO2 emissions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3303, https://doi.org/10.5194/egusphere-egu23-3303, 2023.

Determining the temperature dependence of wetland CH4 and CO2 emissions is critical for predicting the impacts of climate change on greenhouse gas (GHGs) emissions in wetland ecosystems. However, the spatial variation for temperature dependence of wetland CH4 and CO2 emissions is poorly understood, especially at the global scale. Here, we investigate the temperature dependencies of wetland CH4 and CO2 emissions across large-scale climatic gradients using 56,271 daily paired observations of ecosystem-level CH4 and CO2 emissions in 45 widely distributed wetlands from the FLUXNET-CH4 database. The temperature dependencies of CH4 and CO2 emissions show contrasting spatial patterns across globally geographic climate gradients. Specifically, the temperature dependence of CH4 emissions  increased with increasing mean annual temperature (MAT), but the opposite was true for that of CO2 emissions. The ratio of CH4 to CO2 emissions was positively dependent on temperature when only MAT and mean annual precipitation were greater than 4.7 °C and 483 mm, respectively. Our results imply that the relative contribution of CH4 to total GHG emissions increases with ambient temperature increases in a warmer and wetter climate region and could act as a positive feedback mechanism in the future. 

How to cite: Chen, H. and Zhou, X.: Contrasting patterns in the temperature dependence of wetland CH4 and CO2 emissions across globally geographic climate gradients, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4684, https://doi.org/10.5194/egusphere-egu23-4684, 2023.

India is primarily concerned with comprehending regional carbon source-sink response in tandem with changes in atmospheric carbon dioxide (CO2) concentrations or human-caused anthropogenic emissions. Atmosphere CO2 is the most significant greenhouse gas contributing to climate change and global warming. To develop a countrywide mitigation policy, it is therefore critical to identify underlying source-sink locations and their mechanisms at various temporal scales and regional levels. To better understand the variability of CO2 and its relationship with the climate variables requires long-term observations. Recent advancements in high-resolution satellite measurements provide a viable opportunity to examine CO2 variability at a regional level. In this work, we presented the long-term variations and growth rates of the Greenhouse Gas Observing Satellite (GOSAT) and Orbiting Carbon Observatory-2 (OCO-2) satellite retrieved column-averaged dry-air mole fraction of CO2 (XCO2 ) and the relationship of XCO2 growth rate with ENSO and climate parameters (temperature, precipitation, soil moisture, and NDVI) over India for the period 2010 to 2021. Results revealed an increase of 2.54 (2.43) ppm/yr of XCO2 in GOSAT (OCO-2) retrievals during overlapping measurement period (2015-2021). In addition, a wavelet analysis shows an increase in XCO2 every year for GOSAT; however, OCO-2 decreases and increases in XCO2 every 5-6 months. This is attributable to high resolutions measurements of OCO-2 favouring better capture of source (high XCO2)-sink (low XCO2) signal than GOSAT. The Principal Component Analysis (PCA) analysis on XCO2 anomalies showed EOF-1 contributed mainly by the south and southeast of India. Further analysis demonstrated that the trend and seasonal cycle of XCO2 regulates the variability. The XCO2 growth rates strongly correlate with ENSO and NDVI (clear during major ENSO events), whereas precipitation and temperature show a weak correlation. Further, lag correlation analysis reveals that ENSO and climate parameters precede the GOSAT XCO2 growth rates, with soil moisture, NDVI, and ENSO having a good correlation with 8,4 and 3 months of leads, respectively.

How to cite: Das, C. and Kunchala, R. K.: Understanding long-term carbon dioxide (CO2) variability and its link with ENSO and climate parameters over India using satellite retrievals, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4738, https://doi.org/10.5194/egusphere-egu23-4738, 2023.

EGU23-5420 | ECS | Posters on site | BG1.7

A global tracer release experiment to help estimate OH tropospheric concentrations and benchmark chemistry-transport models 

Joel Thanwerdas, Dominik Brunner, and Stephan Henne

Despite the urgent need for reduction of greenhouse gas concentrations, their emissions remain at high levels worldwide. Atmospheric inverse modelling allows to quantify these emissions by leveraging observations of greenhouse gas mole fractions and chemistry-transport models. However, this technique largely relies on models with an imperfect representation of transport and chemical processes and the resulting errors propagate to emission estimates. Atmospheric scientists can improve their models by comparing simulated processes against available observational data.

One efficient, although challenging, way of acquiring such validation data is to perform a tracer release experiment. It consists of releasing one or multiple decaying tracers into the atmosphere at one or multiple locations in the world, and then observe their time-evolving mixing ratios to understand transport pathways, mixing and decay rates. To the best of our knowledge, tracer release experiments have only been performed at local or regional scales to study transport processes, but never at the global scale. A global tracer release experiment could generate invaluable data against which to compare model outputs. However, modelers must be able to disentangle transport and chemical processes from the data, which requires that the experiment be carefully designed. Subject to this requirement being met, it could help to better quantify and even reduce 1) transport errors by investigating inter- and intra-hemispheric transport and 2) chemistry errors by constraining OH tropospheric concentrations. These data could also help to create a benchmarking methodology to highlight the strengths and weaknesses of the regional and global models that are currently used to quantify greenhouse gas emissions.

Here, we present design considerations for such a global tracer release experiment based on simulations with the 3-D chemistry-transport model ICON-ART. Our first results indicate that releasing several hundred tons of two tracers with different lifetimes as pulses could be sufficient to obtain a good estimate of OH concentrations along the parcel trajectories. This method could be applied at different locations in order to sample a large part of the world and at different times, e.g., to account for seasonal variations in OH concentrations. However, we also show that many parameters influence the results and therefore we enumerate the benefits but also the limits of such an experiment.

How to cite: Thanwerdas, J., Brunner, D., and Henne, S.: A global tracer release experiment to help estimate OH tropospheric concentrations and benchmark chemistry-transport models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5420, https://doi.org/10.5194/egusphere-egu23-5420, 2023.

EGU23-6152 | ECS | Posters on site | BG1.7

The seasonal cycle of atmospheric CO2 in South America over the last ten years seen by GOSAT 

Lukas Artelt, Eva-Marie Metz, Sanam Vardag, Sourish Basu, and André Butz

The number of in-situ CO2 measurements in the Southern Hemisphere is very limited. This leads to large 
uncertainties in estimates of regional carbon fluxes by in-situ based inverse models. Satellite-based CO2 
measurements, on the other hand, are available in the Southern Hemisphere with a dense spatial 
coverage. By evaluating these, the regional carbon cycle can be studied in more detail and the results of 
carbon cycle models can be validated against the satellite data.

Here, we present a comparison of atmospheric CO2 data provided by the Greenhouse gases Observing 
SATellite (GOSAT) and in-situ based inverse models for South America from 2009 to 2019. The seasonal 
cycle of atmospheric CO2 concentrations measured by the GOSAT satellite shows differences in both,
amplitude and timing, compared to in-situ based atmospheric inversions. To determine the reason for
these discrepancies, we use the TM5-4DVar atmospheric inversion model assimilating GOSAT satellite 
data to obtain GOSAT based land-surface fluxes. This allows us to identify sub-regions responsible for the 
differences. In order to gain a deeper understanding of the underlying processes, we also analyse various 
climate parameters, fire emission data, and vegetation proxies (for example Solar Induced Fluorescence, 
SIF). By doing so, we aim at improving our understanding of the mechanisms that influence the seasonal 
carbon cycle in South America.

How to cite: Artelt, L., Metz, E.-M., Vardag, S., Basu, S., and Butz, A.: The seasonal cycle of atmospheric CO2 in South America over the last ten years seen by GOSAT, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6152, https://doi.org/10.5194/egusphere-egu23-6152, 2023.

EGU23-6173 | ECS | Orals | BG1.7

Carbon fluxes from different fire types in the Amazon and Cerrado biomes quantified using Earth-observation based modelling 

Dominic Fawcett, Leo Ng, Amos Tai, Xiaoyu Yan, Thais Rosan, Celso Silva Junior, Ana Bastos, Philippe Ciais, Clément Albergel, Luiz Aragão, and Stephen Sitch

Fires in the tropics are linked to both climate and land-use change. While in the Amazon, deforestation-related fires decreased following a substantial reduction in deforestation activities until 2012, there have been recent upturns in deforestation and forest fires. Furthermore, earth system models predict a further increase in the intensity of dry seasons in this region in the 21st century. Therefore, carbon emissions from drought-induced forest fires can counteract further pledged deforestation reductions in the following decades, yet they are only partially accounted for in national carbon emission estimates. Improved assessments of fire impacts, including the carbon fluxes arising from post-fire mortality and regrowth, are therefore highly important. 
Combining a range of available satellite products enables spatially specific fire emissions estimations. We developed a remote sensing based approach where biomass maps, observed forest loss, burned area and active fire data are combined to generate updated fuel load and emission estimates. In addition, space-for-time methods are employed to derive estimates of post-fire mortality as a function of pre-fire biomass. This high-resolution model guarantees an improved separation of fire types, and we can report emissions associated with deforestation, forest degradation and savanna fires for the entire Amazon basin and the Brazilian Cerrado at monthly intervals. 
Results show that over 2015-2020 fires cause annual gross emissions of ~300 Tg C over the Amazon and Cerrado. While instantaneous emissions from forest fires are small, the fire-induced mortality and subsequent decomposition cause legacy fluxes which are closer to deforestation fire emissions in magnitude, highlighting their importance. Recent upturns in deforestation fire emissions were observed, including in conservation areas established before 2004. There is overall good agreement with previous instantaneous fire emission estimates from other approaches (GFED4s, GFED 500 m) while remaining disagreements highlight areas of uncertainties, such as combustion completeness values, which could benefit from additional field measurements and spatial modelling supported by EO products.
Outputs from this work can further be used to improve regional greenhouse gas budgets and inform emission reduction and mitigation efforts.

How to cite: Fawcett, D., Ng, L., Tai, A., Yan, X., Rosan, T., Silva Junior, C., Bastos, A., Ciais, P., Albergel, C., Aragão, L., and Sitch, S.: Carbon fluxes from different fire types in the Amazon and Cerrado biomes quantified using Earth-observation based modelling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6173, https://doi.org/10.5194/egusphere-egu23-6173, 2023.

Increasing extreme events and drastic shifts in the variability, intensity and frequency of droughts, heavy precipitation and frost are predicted to accompany further climate change. It is most likely that an increasing occurrence of such events will be accompanied by soil feedback of GHG emissions, particularly of nitrous oxide (N2O) known to be an extremely sensitive GHG. The increase in extreme events can lead to an increased occurrence of short-term emission pulses, referred to as ‘hot moments’, which can contribute significantly to the total annual N2O emission balance.
To account for this potential feedback to the climate system, biogeochemical models driven by climate projections of multi-model ensembles (CPM) can be used to generate scenarios observing future trends in N2O emission behavior.
Most commonly, the CPM average is used as climate input in biogeochemical models. While averaging CPM’s may provide the best overall comparison with real mean climate change, it poses the risk of ‘averaging out’ expected extreme events, thereby biasing soil-atmosphere feedbacks and future N2O emission trends! 

We follow the hypothesis, that for nitrogen-saturated soils as common in industrialized countries, the annual N2O emissions simulated by the averaged CPM differ from the average annual N2O emissions simulated by the individual CPM’s, as hot moment inducing extreme climate events are averaged as well.

For our biogeochemical model simulations, we used weather data from ten selected individual climate-projections based on the multi-model ensemble of the EURO-CORDEX initiative. To focus on the effects of climate and to exclude possible biases, remaining input parameters were unified, i.e., homogeneous soil horizons and a single crop rotation were assumed. In addition, each simulation period was initialised with the same parameters to exclude possible changes in fluxes resulting from soil carbon and nitrogen cycling.

First results with CANDY and LDNDC seem to support our hypothesis, showing that annual N2O emissions simulated with the averaged CPM differ clearly from those resulting from the output mean of the individual CPM’s.

This emphasises to consider using the averaged output based on individual CPM’s rather than relying solely on averaged CPM’s for predicting future N2O emission trends.

How to cite: Hey, L., F. Jungkunst, H., and H. E. Meurer, K.: A potential bias using averaged climate projection multi model ensembles when forecasting nitrous oxide emissions from soils under climate change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8208, https://doi.org/10.5194/egusphere-egu23-8208, 2023.

EGU23-8372 | Orals | BG1.7

Why atmospheric methane surged in 2020? 

Shushi Peng, Xin Lin, Rona Thompson, Yi Xi, Gang Liu, Xin Lan, Didier Hauglustaine, Benjamin Poulter, Michel Ramonet, Marielle Saumois, Yi Yin, Zhen Zhang, Bo Zheng, and Philippe Ciais

Methane (CH4) levels in the atmosphere increased by 15.1 ± 0.4 ppb in 2020, the highest annual increase from 1984 to 2020, despite a likely decrease in anthropogenic CH4 emissions during COVID-19 confinements. Here, we used bottom-up and top-down methods to quantify the changes in different sources of CH4, and in its atmospheric sink due to the hydroxyl radical (OH) in 2020 compared to 2019. Bottom-up methods showed that, globally, total anthropogenic emissions slightly decreased by ~1.2 Tg CH4 yr-1, fire emissions were lower than in 2019 by ~6.5 Tg CH4 yr-1, and wetland emissions increased by 6.0 ± 2.3 Tg CH4 yr-1. In addition to higher wetland emissions in 2020 than 2019 from bottom-up, we found a decrease of 1.6–1.8% in tropospheric OH concentration relative to 2019, mainly due to lower anthropogenic NOx emissions and associated lower free tropospheric ozone during the confinements. Based on atmospheric CH4 observations from the surface network, and considering the decrease in OH, using top-down inversions, we infer that global net emissions increased by 6.9 ± 2.1 Tg CH4 yr-1 in 2020 relative to 2019, while the global CH4 removal from reaction with OH in the atmosphere decreased in 2020 by 7.5 ± 0.8 Tg CH4 yr-1. Therefore, we attribute the positive growth rate anomaly of atmospheric CH4 in 2020 relative to 2019 to lower OH sink (53 ± 10%) and higher natural emissions (47 ± 16%), mostly from wetlands. Warmer and wetter climate conditions in the Northern Hemisphere promoted wetland emissions, but fires decreased in the Southern Hemisphere, compared to the previous year. Our study highlights that northern microbial emissions of CH4 are highly sensitive to a warmer and wetter climate and could act as a positive feedback in the future. Our study also hints that the global CH4 pledge must be implemented by taking into account NOx emissions trend, whose reduction lengthens the lifetime of atmospheric CH4.

How to cite: Peng, S., Lin, X., Thompson, R., Xi, Y., Liu, G., Lan, X., Hauglustaine, D., Poulter, B., Ramonet, M., Saumois, M., Yin, Y., Zhang, Z., Zheng, B., and Ciais, P.: Why atmospheric methane surged in 2020?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8372, https://doi.org/10.5194/egusphere-egu23-8372, 2023.

EGU23-9695 | ECS | Orals | BG1.7

Biomass recovery after fires dominates the carbon sink of boreal forests over the last three decades 

Yidi Xu, Philippe Ciais, Wei Li, Sassan Saatchi, Maurizio Santoro, Alessandro Cescatti, Dmitry Shchepashchenko, Guojin He, Ceccherini Guido, Jiaying He, Lei Fan, Martin Brandt, Rasmus Fensholt, Jean-Pierre Wigneron, Heather Kay, Stephen Sitch, Ana Bastos, Simon Bowing, François Ritter, and Ibrahim Fayad

Wildfires are an integral part of boreal forest dynamics. Understanding the carbon loss/recovery associated with fires is crucial to assess the stability of these slow-growing forests.  Yet, the carbon balance from fires and post-fire forest recovery remain uncertain at the biome scale due to the lack of spatial details about rates of forest regrowth. Here, we quantify carbon losses from fire emissions and gains from post-fire regrowth using high spatial-resolution satellite data and a bookkeeping model. We combined a 35-year long record of burned area from the Landsat satellites since 1985 with local biomass-age regrowth curves derived from high-resolution satellite-based above ground biomass (AGB) datasets. We found that forests in Eurasia tend to recover faster and reach higher biomass levels than those in North America. Young forests recovering from post-1985 wildfires produced a carbon sink of 652±200 TgC during the period 1985 to 2020. The additional recovery of older secondary forests that burned before 1985 further adds a cumulative sink of 1659±346 TgC. Comparatively, old-growth forests that did not burn accumulated 930±233 TgC during the period 1985-2020. This result shows 71% of the contemporary carbon sink in AGB is contributed by recovery from fires. After accounting for fire emissions each year and for the slow decay of coarse woody debris after burning, the net AGB carbon sink in boreal forests is 2108±234 TgC during 1985-2020. This study provides the first spatially explicit aboveground observation-based carbon budget of boreal forests and provides insights on the key factors that will control its future evolution.

How to cite: Xu, Y., Ciais, P., Li, W., Saatchi, S., Santoro, M., Cescatti, A., Shchepashchenko, D., He, G., Guido, C., He, J., Fan, L., Brandt, M., Fensholt, R., Wigneron, J.-P., Kay, H., Sitch, S., Bastos, A., Bowing, S., Ritter, F., and Fayad, I.: Biomass recovery after fires dominates the carbon sink of boreal forests over the last three decades, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9695, https://doi.org/10.5194/egusphere-egu23-9695, 2023.

EGU23-10462 | Posters virtual | BG1.7

An assessment of sea-air CO2 flux in the Arctic Ocean from 1985 to 2018 

Sayaka Yasunaka, Manfredi Manizza, Jens Terhaar, Are Olsen, Ryohei Yamaguchi, Peter Landschützer, Eiji Watanabe, Dustin Carroll, Hanani Adiwira, Jens Müller, and Judith Hauck

As a contribution to the Regional Carbon Cycle Assessment and Processes phase 2 (RECCAP2) project, we present synthesized estimates of the Arctic Ocean CO2 uptake and their uncertainties from state-of-the-art surface ocean pCO2-observation products, global and regional ocean biogeochemical models and atmospheric inversions. For the period of 1985−2018, the Arctic Ocean represents a net sink of CO2 of 103 ± 19 TgC yr−1 in the pCO2 products and 92 ± 30 TgC yr−1 in the ocean biogeochemical models. While the long-term mean CO2 uptake in the Arctic Ocean is primarily caused by steady-state fluxes of natural carbon, it is enhanced 28% by the atmospheric CO2 increase and 15% by climate change. Moreover, the climate effect in the Arctic Ocean has become more important in recent years. The CO2 uptake peaks in late summer and early autumn, and is low in winter because the sea ice cover inhibits sea-air fluxes. The annual mean of CO2 uptake increased due to the decreasing sea ice concentration both in the pCO2 products and the ocean biogeochemical models. Both, the mean CO2 uptake and the trend, is substantially weaker in the atmospheric inversions. Uncertainty across all estimates is large especially in the estimated surface ocean pCO2 values in the East Siberian Sea and the Laptev Sea, due to scarcity of observations and missing processes in models, such as land-sea fluxes and sediment dynamics.

How to cite: Yasunaka, S., Manizza, M., Terhaar, J., Olsen, A., Yamaguchi, R., Landschützer, P., Watanabe, E., Carroll, D., Adiwira, H., Müller, J., and Hauck, J.: An assessment of sea-air CO2 flux in the Arctic Ocean from 1985 to 2018, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10462, https://doi.org/10.5194/egusphere-egu23-10462, 2023.

An increasing trend is observed in the frequency of climate extremes. Drought is a widely observed extreme event that has a significant influence on the terrestrial ecosystem functioning and carbon balance. Interannual variability in the Indian summer monsoon (ISM) rainfall, an important meteorological phenomenon providing 90 percent of the country’s annual precipitation, also significantly influences the vegetation carbon processes and carbon balance. Identifying the changes in vegetation greenness and terrestrial carbon fluxes to droughts and variability in ISM is essential for planning mitigation strategies and policy making. The main objective of this study is to identify the impact of drought and ISM variability in terrestrial biosphere carbon processes and their impact on the national carbon budget. Here we attempt a comprehensive study using different meteorological datasets available and CO​2 flux data prescribed from inversion, process-based, and LUE-based models to quantify the impact of extreme events and monsoonal variability on the ecosystem behavior and, thereby, on the atmosphere-biosphere  CO​2 exchange fluxes over the Indian region while considering prominent vegetation classes. We also use the inference from the satellite-derived  Solar Induced Fluorescence (SIF) and eddy covariance flux observations over the region. Preliminary results will be presented and discussed. 

How to cite: Ravi P, A. and K Pillai, D.: Assessing the impact of climate extremes and Indian summer monsoon variability on terrestrial biosphere carbon fluxes over Indian region using satellite observations and modeling., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10881, https://doi.org/10.5194/egusphere-egu23-10881, 2023.

EGU23-10894 | Orals | BG1.7

Seasonal variabiltiy of the surface ocean carbon cycle: a global synthesis 

Keith Rodgers and the RECCAP2 coauthors: seasonal variabiltiy in surface ocean carbon cycle

Here we present a synthesis of surface ocean pCO2 and air-sea CO2 flux seasonality for a modern climatology and      their decadal trends between the 1980s and 2010s, as part of the REgional Carbon Cycle Assessment and Processes Phase 2 (RECCAP2) project. Working with both surface ocean pCO2-observation products (pCO2 products) and global ocean biogeochemistry models (GOBMs), our main findings are: (i) Over biome scales, both pCO2 products and GOBMs confirm increases in the seasonal amplitude of pCO2 and integrated CO2 fluxes between 1985-1989 and 2014-2018. (ii) For the 2014-2018 climatology, GOBMs exhibit a systematic bias with too-weak biologically-driven seasonal variability in surface dissolved inorganic carbon (DIC), such that the pCO2 seasonal cycle in subtropical biomes is spuriously large and both the amplitude and phase of seasonal pCO2 variations diverge from those in the pCO2 products in subpolar and circumpolar biomes. (iii) Decadal increases in pCO2 seasonal cycle amplitude in subtropical biomes are attributed to being largely driven by reducing CO2 buffering capacity and increasing sensitivity to temperature due to increasing anthropogenic carbon (Cant) content insurface waters for both the pCO2 products and GOBMs. In subpolar and circumpolar biomes, the seasonality change for GOBMs is dominated by Cant invasion, whereas for pCO2 products modulations of the climate state are equally important. (iv) Considered together, the subtropical biomes exhibit decadal increases in CO2 flux seasonality that are larger during winter than summer, consistent with the mechanism described by Fassbender et al. (2022) and potentially promoting a negative feedback in the climate system by increasing the CO2 uptake in winter, by virtue of surface winds being stronger in winter than summer. (v) Large ensemble simulations with ESMs were applied to confirm the validity of biomes as aggregation domains for identifying forced signals. Despite compromises to DIC seasonality impacting pCO2 seasonality, the chosen biome-scale is appropriate for representing the decadal rate of increase of pCO2 seasonality for both GOBMs  and pCO2 products.

How to cite: Rodgers, K. and the RECCAP2 coauthors: seasonal variabiltiy in surface ocean carbon cycle: Seasonal variabiltiy of the surface ocean carbon cycle: a global synthesis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10894, https://doi.org/10.5194/egusphere-egu23-10894, 2023.

EGU23-11163 | ECS | Posters on site | BG1.7

A new gap-filling method to avoid systematic bias in carbon balance estimates in northern ecosystems 

Henriikka Vekuri, Juha-Pekka Tuovinen, Liisa Kulmala, Dario Papale, Pasi Kolari, Mika Aurela, Jari Liski, Tuomas Laurila, and Annalea Lohila

Climate change mitigation requires – besides greenhouse gas emission reductions – actions to increase carbon sinks and storages in terrestrial ecosystems. However, quantification of sources and sinks of carbon depends on reliable estimates of the net ecosystem exchange of carbon dioxide (CO2). This also involves the eddy covariance technique (EC), a key method to directly measure the CO2 fluxes between ecosystems and the atmosphere. Various methods have been used to impute, or gap-fill, missing EC data and previous comparisons have shown that the accuracy of the best-performing methods, e.g. the widely-used marginal distribution sampling (MDS), is reaching the noise limit of measurements. However, knowledge on the performance of gap-filling methods is lacking from northern ecosystems.

By analyzing an extensive global data set, we show that MDS causes significant carbon balance errors for northern ecosystems. MDS systematically overestimates the carbon dioxide (CO2) emissions of carbon sources and underestimates the CO2 sequestration of carbon sinks. We discuss reasons for the errors and show how a machine learning method called extreme gradient boosting or a modified version of MDS can be used to minimize the northern site bias.

How to cite: Vekuri, H., Tuovinen, J.-P., Kulmala, L., Papale, D., Kolari, P., Aurela, M., Liski, J., Laurila, T., and Lohila, A.: A new gap-filling method to avoid systematic bias in carbon balance estimates in northern ecosystems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11163, https://doi.org/10.5194/egusphere-egu23-11163, 2023.

EGU23-11303 | ECS | Posters on site | BG1.7

Recent methane trends derived from S5P/TROPOMI data 

Jonas Hachmeister, Oliver Schneising, Michael Buchwitz, John P. Burrows, Justus Notholt, and Matthias Buschmann

Methane (CH4) has a relatively long tropospheric lifetime and is consequently a well-mixed greenhouse gas. CH4, released by several
types of human activity and natural processes, is one important driver of climate change. The global mean concentration of CH4 has
increased by 156% between the beginning of the industrial revolution around 1750 and 2019, reaching roughly 1866 ppb in 2019 (IPCC).
The time dependence of this increase is not well understood. For example, it is not entirely clear why CH4 growth rates reached record 
high values in 2020 and 2021. Furthermore, the number of published growth rates (annual methane increases) is limited and includes data
from NOAA and the Copernicus Climate Change Service. Hence the rate of increase of CH4 calculated from independent data sources are
valuable for cross-verification and in furthering our understanding of the methane cycle.
The TROPOMI instrument onboard the Sentinel-5P satellite provides daily CH4 data with a spatial resolution of roughly 7x7 km²
and global coverage. We analyze the TROPOMI CH4 data with the goal of determining robust values of the annual methane increases (AMI)
for both global and zonally resolved data. For this we utilize a dynamic linear model approach to separate the underlying methane level,
the seasonal and short-term variations. The AMIs are defined as the difference in the underlying (i.e. fitted) methane level between
the first and last day of a year. In this contribution, we present first results for global and zonal TROPOMI AMIs for the years 2019-2022.
We compare the resulting global TROPOMI AMIs with data from NOAA and Copernicus and discuss the distribution of zonal AMIs for the given years.

How to cite: Hachmeister, J., Schneising, O., Buchwitz, M., Burrows, J. P., Notholt, J., and Buschmann, M.: Recent methane trends derived from S5P/TROPOMI data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11303, https://doi.org/10.5194/egusphere-egu23-11303, 2023.

EGU23-12203 | ECS | Posters on site | BG1.7

Fire emission estimates for Australian extreme fire season 2019/2020 using FLEXPART  

Ines Dillerup, Christopher Lüken-Winkels, Eva-Marie Metz, Sanam Vardag, Nicholas Deutscher, David Griffith, and André Butz

In Australia, increasing temperatures and prolonged drought periods lead to an intensification of wildfires. In particular, severe fires are expected to occur more frequently in Southeast Australia’s eucalyptus forests leading to strongly enhanced CO2 emissions and preventing the renewed uptake of the released CO2 by vegetation. However, current fire emission estimates presented by conventional fire emission databases show significant discrepancies in their emission estimates of extreme fire events like the Australian fire season 2019/2020.

Here, we investigate the fire emissions released during the Australian summer 2019/2020 based on total column measurements of CO2 and CO using the Lagrangian Particle Dispersion Model FLEXPART. We calculate footprints and backward trajectories of trace gases to inversely retrieve carbon emission estimates. In a first case study we focus on TCCON total column measurements of CO and CO2 taken in Wollongong located close to the hot-spot of eucalyptus fires. As the measurements show a significant enhancement of all mentioned tracers during the fire event, FLEXPART is used to calculate emission estimates for southeast Australia. Furthermore, we retrieve emission factors between the trace gases. Our results are compared to the conventional databases like GFED, GFAS and FINN and emission estimates published by other studies.

How to cite: Dillerup, I., Lüken-Winkels, C., Metz, E.-M., Vardag, S., Deutscher, N., Griffith, D., and Butz, A.: Fire emission estimates for Australian extreme fire season 2019/2020 using FLEXPART , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12203, https://doi.org/10.5194/egusphere-egu23-12203, 2023.

EGU23-12424 | ECS | Posters on site | BG1.7

Constraining land surface CO2 fluxes by ecosystem and atmospheric observations using atmospheric transport 

Samuel Upton, Wouter Peters, Markus Reichstein, Santiago Botia, Fabian Gans, Basil Kraft, and Ana Bastos

The growth rate of atmospheric CO2 mole fractions can be measured with high accuracy, but there are still large uncertainties in our ability to separate anthropogenic and natural sources and sinks. One major source of uncertainty is the net flux of carbon from the biosphere to the atmosphere, or Net Ecosystem Exchange (NEE). There are two major approaches to quantifying NEE; top-down approaches that typically use atmospheric inversions, and bottom-up estimates using process-based or data-driven terrestrial biosphere models, upscaled to the regional or global scale. Both approaches have known limitations. A system that harmonizes these approaches, providing a high-quality estimate of the spatial distribution of NEE, and an accurate integral of NEE at regional and global scales, would improve our ability to model the full carbon budget. With other component fluxes, a harmonized product could help improve our monitoring of regional and national greenhouse gas budgets, and thus verify the trajectory towards CO2 emission goals.

This study builds upon our previous work that connected the bottom-up eddy-covariance model to top-down estimates of regional NEE from atmospheric inversions using fixed regional linear oper-ators. That work demonstrated that top-down estimates of atmospheric CO2 provide an important additional constraint to a data-driven bottom up model. The use of top-down constraints improved the regional and global upscaling of NEE, leveraging the strengths of the two different approaches. However, the previous work had a simplified computational link between the top-down and bottom-up fluxes of NEE, and did not access the very large volume of atmospheric observations of atmospheric CO2. Here, we replace the regional atmospheric inversion estimates of NEE with direct observations of the atmospheric mole fractions of CO2. The fixed regional linear operators are replaced by estimating the near-field sources of an observation using an atmospheric transport model. For training, the bottom-up model is run for the source locations. We apply this technique to observations from to tropical, extra-tropical and boreal tall-tower sites over different meteorological conditions where we infer NEE from the observed atmospheric mole fraction, corrected for CO2 background and non-biogenic CO2 fluxes. This inference is combined in the objective function with tower-level inferences, and directly used to update the bottom-up model. The model can ‘see’ more varied inputs in the dynamic footprints, and the size of our pool of training data is increased. The new process improves our ability to accurately infer the regional and global distribution of NEE by directly learning across spatial scales, using diverse observations of CO2.

How to cite: Upton, S., Peters, W., Reichstein, M., Botia, S., Gans, F., Kraft, B., and Bastos, A.: Constraining land surface CO2 fluxes by ecosystem and atmospheric observations using atmospheric transport, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12424, https://doi.org/10.5194/egusphere-egu23-12424, 2023.

EGU23-12786 | Orals | BG1.7

Constraining regional and global ocean carbon fluxes in RECCAP2 

Judith Hauck, Nicolas Gruber, Masao Ishii, and Jens Daniel Müller and the RECCAP2 ocean chapter leads

Keeping global warming in line with the Paris Agreement requires rapid reductions in CO2 emissions. Tracking these reductions demands a thorough bookkeeping of natural and anthropogenic carbon fluxes. The second REgional Carbon Cycle Assessment and Processes (RECCAP2) activity of the Global Carbon Project aims to accurately assess land and ocean CO2 sources and sinks through the efforts of hundreds of scientists around the globe. 

For the ocean component, regional budgets are developed for the global ocean and five large regions for the period 1980-2018. In addition, four ‘special focus’ themes, namely the biological carbon pump, the seasonal cycle, the coastal ocean and model evaluation are addressed. We use state-of-the-art ocean models and observation-based datasets to provide robust estimates of regional CO2 budgets and constrain their uncertainties. Here, we will provide an overview of RECCAP2 activities, and showcase key results focusing on mean ocean carbon fluxes, and their trends and variability.

How to cite: Hauck, J., Gruber, N., Ishii, M., and Müller, J. D. and the RECCAP2 ocean chapter leads: Constraining regional and global ocean carbon fluxes in RECCAP2, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12786, https://doi.org/10.5194/egusphere-egu23-12786, 2023.

EGU23-12963 | ECS | Posters on site | BG1.7

High-resolution quantification of aboveground carbon change over the tropics 

Yu Feng, Philippe Ciais, Yidi Xu, Jean-Pierre Wigneron, Xiaojun Li, and Lei Fan

Tropical ecosystems play an important role in regulating the global carbon balance. Existing studies have extensively analyzed the carbon dynamics of tropical forests, the largest terrestrial component of the global carbon budget, showing a likely neutral contribution of tropical forests to the global carbon cycle. However, high-resolution dynamics of aboveground carbon (AGC) change of the whole tropical terrestrial ecosystem and its processes remain rarely investigated. In this study, we first used low-frequency L-band passive microwave observations to derive wall-to-wall maps of annual AGC stocks over the tropics at 25-km spatial resolution. Using high-resolution satellite observations of land-cover change and biomass maps and random forest models, we separated the AGC stock into various ecosystems, including forest, shrub, and short-vegetation (grass and crop), and attributed the change to different degradation processes such as fires and deforestation at 100-m resolution. Our preliminary results show that total AGC stocks in tropical ecosystems increased by  +2.25 [+1.19,+3.29] PgC (the range represents the minimum and maximums of the multiple estimates) from 2010 to 2020. The coast of Brazilian Mata Atlantica, Central African Republic, and east Tanzania are the hotspots of net increase, while the Arc of Deforestation in the Amazon basin and the Congo Basin show substantial net losses. Gross losses from non-fire deforestation and fire totaled -1.62 [-1.38,-1.86] PgC yr-1. We also observed strong recovery in African burned regions, possibly due to post-fire regrowth and additional recovery resulting from declining fires in the region. Our results highlight the importance of explicit temporal and spatial mapping of tropical carbon dynamics at high resolution, which can help us better understand the role of tropical terrestrial ecosystems in the global carbon cycle.

How to cite: Feng, Y., Ciais, P., Xu, Y., Wigneron, J.-P., Li, X., and Fan, L.: High-resolution quantification of aboveground carbon change over the tropics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12963, https://doi.org/10.5194/egusphere-egu23-12963, 2023.

EGU23-13759 | Orals | BG1.7

An assessment of CO2 storage and sea-air fluxes for the Atlantic Ocean and Mediterranean Sea between 1985 and 2018  

Fiz F. Perez, Marion Gehlen, Jerry Tjiputra, Are Olsen, Meike Becker, Marta Lopez-Mozos, Jens D. Müller, Nadine Goris, and Judith Hauck

The dynamic and thermohaline characteristics of the Atlantic Ocean linked to the Atlantic Meridional Overturning Circulation (AMOC) give it a specific role in the accumulation of heat and CO2, either of natural or anthropogenic origin (Cant), from the surface layer to the deep waters, significantly mitigating the impacts of anthropogenic climate change. Here, we evaluate the annual mean, long-term trends, seasonal cycle and interannual variability of net sea-air CO2 fluxes (FCO2) between 1985 and 2018 based on observation products (pCO2-products) and global ocean biogeochemical models (GOBMs) for the Atlantic from 30ºS to the Nordic Seas (~79ºN) and the Mediterranean. The mean contemporary FCO(sum of anthropogenic and natural components) is estimated to be 0.362 ± 0.067 and 0.47 ± 0.15 Pg C yr-1 using pCO2-products and GOBMs, respectively. The GOBMs show consistent growth trends in CO2 uptake with rates similar to the atmospheric CO2 growth, however trends obtained from CO2-products show a sharp increase from the pre-2000 period to the post-2000 period. There is overall agreement between pCO2-products and GOBMs results for mean values, seasonal cycle and interannual variability in all biomes, except for the North Atlantic subpolar biome, where pCO2-products show lower mean values, larger trends, and a different seasonal cycle than GOBMs. The GOBMs and pCO2-products show very concordant values in equatorial and subtropical regions, where CO2 variability is strongly determined by temperature. For the period 1994-2007, GOBMs show concordant values in annual Cant storage rate with carbonate marine system observations (Gruber et al., 2019) with values of 0.506 ± 0.106 Pg C yr-1 vs 0.673 ± 0.066 Pg C yr-1, respectively. The Cant storage rate agreement between GOBMs and observations are also registered in the different biomes, although in both permanently stratified subtropical in North and South Atlantic biomes, the storage rates in GOBMs show a larger spread with their mean values 30 and 40% lower than those estimated from observations. In general, the Atlantic accumulates more Cant than that inferred from the cumulative FCO2 changes, partly due to a significant lateral Cant transport from the Southern Ocean (about 30%).

How to cite: Perez, F. F., Gehlen, M., Tjiputra, J., Olsen, A., Becker, M., Lopez-Mozos, M., Müller, J. D., Goris, N., and Hauck, J.: An assessment of CO2 storage and sea-air fluxes for the Atlantic Ocean and Mediterranean Sea between 1985 and 2018 , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13759, https://doi.org/10.5194/egusphere-egu23-13759, 2023.

EGU23-13792 | Orals | BG1.7

Impacts of land use and environmental change on the Eastern European land carbon sink 

Karina Winkler, Hui Yang, Raphael Ganzenmüller, Richard Fuchs, Guido Ceccherini, Grégory Duveiller, Giacomo Grassi, Julia Pongratz, Ana Bastos, Anatoly Shvidenko, Arnan Araza, Martin Herold, and Philippe Ciais

Land-based mitigation is essential in reducing carbon emissions. Yet, the attribution of land carbon fluxes to their sinks and sources remains highly uncertain, in particular for the forest-rich but data-poor region of Eastern Europe. Here we integrate various data sources (from top-down and bottom-up modelling, earth observation, inventories) to show that Eastern Europe accounted for an annual aboveground biomass (AGB) carbon sink of ~0.49 GtC in 2010‑2019, or about 75% of the entire European carbon uptake. However, we find that the land-based carbon sink is declining. This declining trend is mainly driven by changes in land use and land management, but also by increasing natural disturbances due to ongoing climate change. Despite the high overall importance of environmental factors such as soil moisture, nitrogen and CO2 for enhancing the land-based carbon sink, we find indicators of a saturation effect of the regrowth in abandoned former agricultural areas, combined with an increase in wood harvest, particularly in European Russia. Our results contribute to a better understanding of the regional carbon budget of Eastern Europe and its trend. This study sheds light on land use and management as drivers of the land-based carbon sink and their role for climate mitigation.

How to cite: Winkler, K., Yang, H., Ganzenmüller, R., Fuchs, R., Ceccherini, G., Duveiller, G., Grassi, G., Pongratz, J., Bastos, A., Shvidenko, A., Araza, A., Herold, M., and Ciais, P.: Impacts of land use and environmental change on the Eastern European land carbon sink, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13792, https://doi.org/10.5194/egusphere-egu23-13792, 2023.

EGU23-14171 | ECS | Posters on site | BG1.7

Numerical simulation of the atmospheric CH4 increase and the corresponding decrease of δ13C(CH4) after 2007 

Anna-Leah Nickl, Franziska Winterstein, and Patrick Jöckel

The global atmospheric CH4 growth rate stagnated between 2000 and 2007, and has continued to grow since 2007. This renewed CH4 rise has been analysed with respect to a 2007 onward decline in  δ13C(CH4), indicating changes in the relative contribution of CH4 sources. However, this is still subject to debate and a variety of hypotheses have been put forward. In our work, we present numerical sensitivity simulations that investigate the impact of different inventories of methane emission fluxes on the globally averaged δ13C(CH4) signature. We apply the state-of-the-art global chemistry-climate model EMAC and use a simplified approach to simulate methane loss. We include methane isotopologues and take the kinetic isotope effects in physical and chemical processes into account. We further consider regional differences in the isotopic signatures of individual emission source categories, such as, for example, the differences between signatures of tropical and boreal wetlands emissions. Based on recent emission inventories and isotopic source signatures from the literature, our chemistry climate model reproduces the actual atmospheric methane and δ13C(CH4) distribution adequately. We show that our setup is suitable to constrain the individual influence of different CH4 sources on the global average δ13C(CH4). We further present an approach to optimize the global methane level with respect to station measurements probing for a strategy to include the isotopic information into such an optimization process.

How to cite: Nickl, A.-L., Winterstein, F., and Jöckel, P.: Numerical simulation of the atmospheric CH4 increase and the corresponding decrease of δ13C(CH4) after 2007, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14171, https://doi.org/10.5194/egusphere-egu23-14171, 2023.

EGU23-15006 | ECS | Orals | BG1.7

A comprehensive synthesis of anthropogenic and natural sources and sinks of Australasia carbon budget (2010-2019) 

Yohanna Villalobos, Pep Canadell, Peter Briggs, Ian Harman, Elizabeth D. Keller, Beata Bukosa, Sara E. Mikaloff-Fletcher, Ben Smith, Miko UF. Kirschbaum, Donna Giltrap, Liyin Liang, Ronny Lauerwald, Judith Rosentreter, Taylor Maavara, Laure Resplandy, Peter J. Rayner, Eva Schöemann, and Sourish Basu

Accurate national carbon budget assessments allow nations to evaluate their progress in cutting carbon emissions and therefore be aligned with the Paris Climate Agreement goals. To support the initiative of The REgional Carbon Cycle Assessment and Processes (RECCAP-2), we built a synthesis of the Australasia (Australia and New Zealand) terrestrial carbon budget for 2010-2019 based on top-down and bottom-up approaches. Major carbon flux components in the bottom-up budget (e.g., net primary productivity and heterotrophic respiration) were simulated by CABLE model, Biome-BGC model and Cewn simulations. In addition, this budget include carbon flux components from the land-ocean aquatic continuum, such as inland waters, estuaries, blue carbon ecosystems, and continental shelves and carbon fluxes embodied in trade (export and import) of crops, woods, livestock and fossil fuel. We reconciled Australia and New Zealand bottom-up budgets separately with fluxes derived from regional and global OCO-2, GOSAT flux inversions, as well as fluxes obtained from in-situ measurement only (CarbonWatchNZ). We found that annual mean budgets for Australia agree relatively well (within the uncertainty range) with regional and global top-down GOSAT and OCO-2 flux estimates. New Zealand's annual bottom-up carbon budget also agrees relatively well with fluxes derived from CarbonWatchNZ inversion and GOSAT but disagrees with global flux estimates from OCO-2.

How to cite: Villalobos, Y., Canadell, P., Briggs, P., Harman, I., Keller, E. D., Bukosa, B., Mikaloff-Fletcher, S. E., Smith, B., Kirschbaum, M. UF., Giltrap, D., Liang, L., Lauerwald, R., Rosentreter, J., Maavara, T., Resplandy, L., Rayner, P. J., Schöemann, E., and Basu, S.: A comprehensive synthesis of anthropogenic and natural sources and sinks of Australasia carbon budget (2010-2019), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15006, https://doi.org/10.5194/egusphere-egu23-15006, 2023.

EGU23-15146 | ECS | Orals | BG1.7

A new approach for estimating anthropogenic carbon relying on an observational back-calculation method 

Marta López-Mozos, Fiz F. Pérez, Lidia I. Carracedo, Geoffrey Gebbie, and Antón Velo

Around 31% of carbon dioxide derived from human activities (Canth) has been absorbed by the ocean (DeVries, 2014; Gruber et al., 2019; Sabine et al., 2004). This accumulation helps to mitigate atmospheric carbon dioxide (CO2), but in turn leads to severe consequences on marine systems (IGBP, IOC, SCOR, 2013). Both components of CO2, i.e. anthropogenic and natural, present high variability and uncertainties difficult to observe and quantify. In particular, the Canth signal represents a small fraction of the total dissolved inorganic carbon pool (CT) and it is not directly distinguishable from the natural component, resulting in the emergence of back-calculation techniques (Brewer 1978; Chen and Millero, 1979) to derive it indirectly. Over the years, back-calculation techniques have undergone remarkable improvements (Gruber et al., 1996; Sabine et al., 2004; Touratier et al., 2004, 2007; Vázquez-Rodríguez et al., 2009a, 2009b, 2012), resulting in different methods for estimating Canth that, despite providing helpful and advanced results, show various biases and limitations. Here, we present a new approach for estimating Canth that relies on a back-calculation methodology, purely based on carbon data, and provides results that show good agreement with previous global Canth climatologies. Our approach mainly differs from previous methodologies by pioneering using the transport matrix output from a data‐assimilating ocean circulation inverse model (TMI: Total Matrix Intercomparison; Gebbie and Huybers, 2010) to obtain preformed properties, instead of the historical use of Optimum Multiparameter analysis (OMP). This improvement prevents from the need to use (sub)surface-property linear regressions to estimate preformed alkalinity or air-sea CO2 disequilibrium, and allows introducing different corrections for denitrification and, as a novelty, oxygen disequilibrium.

How to cite: López-Mozos, M., Pérez, F. F., Carracedo, L. I., Gebbie, G., and Velo, A.: A new approach for estimating anthropogenic carbon relying on an observational back-calculation method, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15146, https://doi.org/10.5194/egusphere-egu23-15146, 2023.

EGU23-15166 | ECS | Posters virtual | BG1.7

Significance of biological forcing on the spatio-temporal variability of carbon dioxide fluxes over the Northern Indian Ocean 

Lekshmi Krishna, Rishikesh Bharti, and Chandan Mahanta

The oceanic uptake and release of carbon dioxide (CO2) play a critical role in global carbon cycle since oceans can act both as sink and source of CO2 which vary spatially and temporally. The ocean primary productivity has significant effects on the CO2 flux, as it consumes the dissolved CO2 at the sea surface for the photosynthetic carbon production, reducing the surface carbon content, while higher production rates at surface layers cause higher respiration rates in the subsurface layers, thereby increasing the sea water CO2 partial pressures (pCO2) in these layers. Northern Indian Ocean is found to be a perennial source of CO2 and also one of the most productive regions of Indian Ocean, however, while the western sub basin acts as an annual source, the eastern counterpart is a seasonal sink, especially during the monsoon and winter seasons. The major factors contributing to its high productivity is the summer and winter blooms caused by the wind-driven upwelling and winter cooling as well as convective mixing. The present study attempts to understand the relation between the CO2 fluxes and primary productivity in the western and eastern sub basins of the northern Indian Ocean. The study divides the Sea in to North, West, East and Central parts based on the productivity and analyses the spatial and temporal variation of the CO2 exchange between the sea and atmosphere in connection with the primary production. Satellite as well as climatological data were used to derive the monthly CO2 fluxes and ocean primary productivity. Both sub basins exhibited high rates of productivity during the monsoon and winter seasons; high monsoon and winter CO2 outfluxes were observed over the western sub basin in the northern waters towards the coast, while the eastern basin was found to have strong influxes in both the seasons over the northern waters. Towards the open ocean part, both fluxes and productivity showed decreasing trends in the western basin, whereas, the eastern sub basin showed an increasing trend of CO2 outflux over the open ocean waters in the south. Surface stratification and limited nutrient availability have resulted in the low productivity rates during the pre- and post-monsoon seasons in both basins, while the absence of the surface mixing resulting from the stratification along with photosynthetic consumption lowered the fluxes. The primary production was observed to have a significant influence over the western basin fluxes while the fluxes over the eastern basin were primarily affected by the physical forcing i.e., the thermohaline stratification.

How to cite: Krishna, L., Bharti, R., and Mahanta, C.: Significance of biological forcing on the spatio-temporal variability of carbon dioxide fluxes over the Northern Indian Ocean, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15166, https://doi.org/10.5194/egusphere-egu23-15166, 2023.

EGU23-16001 | Orals | BG1.7

The land-to-ocean loops of the global carbon cycle: How much do we know about long-term trends and drivers of changes in CO2 fluxes ? 

Pierre Regnier, Laure Resplandy, Judith Rosentreter, Raymond Najjar, and Philippe Ciais

This contribution presents a new view of the global carbon cycle which accounts for the land-to-ocean transport of carbon through inland waters, estuaries, tidal wetlands and continental shelf waters—the ‘land-to-ocean aquatic continuum’ (LOAC). We highlight how biogeochemical and ecological processes from land-to-ocean have been perturbed by human interventions, including atmospheric composition change, climate change and land-use change. The extend to which these anthropogenic perturbations have altered regional and global CO2 budgets and trends along the LOAC are also presented and the knowledge gaps that are key to reduce uncertainties in future assessments of LOAC fluxes are identified. Finally, broader implications regarding the quantification of the terrestrial and open ocean sinks of anthropogenic carbon are briefly discussed 

How to cite: Regnier, P., Resplandy, L., Rosentreter, J., Najjar, R., and Ciais, P.: The land-to-ocean loops of the global carbon cycle: How much do we know about long-term trends and drivers of changes in CO2 fluxes ?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16001, https://doi.org/10.5194/egusphere-egu23-16001, 2023.

EGU23-16482 | Posters on site | BG1.7

Measurement of the isotopic signature of boreal wetland methane emissions 

Rebecca Fisher, Ceres Woolley Maisch, David Lowry, James France, Thomas Rockmann, Carina van der Veen, C. Mary R. Fowler, and Euan G. Nisbet

The use of δ2H as well as δ13C methane isotope measurements will help improve regional and global source apportionment and understanding of reasons for methane’s continued and accelerating growth. However more data on regional variability in isotopic signatures of the main sources is required as well as regular measurements of both isotopes in methane in background air.

Field campaigns across Canada in June 2022 and to northern Finland and Norway in August 2022 were carried out to collect air samples for methane δ13C and δ2H isotopic characterisation from boreal wetlands.

In Finland and Norway a road campaign with continuous measurements of methane mole fraction was carried out from Södankyla, Finland to Aidejavri, Norway, with a generally decreasing gradient in methane from south to north and this has been compared with land cover maps. Air samples for isotopic analysis were collected at Södankyla, Kaamanen and Lompolojänkkä fens in Finland and Aidejavri and Suossjavri degrading palsa mires in Norway. In Canada δ2H and δ13C isotopic signatures were determined in methane emitted by wetlands in northern Ontario including at Fraserdale, and northern Saskatchewan (East Trout Lake).

Overall the mean signatures of emissions from the boreal samples collected were -67‰ for δ13C and -320‰ for δ2H, but there was significant local variability when sampling air close to ground level. Aircraft campaigns would be a better way of identifying the integrated isotopic signature of regional wetland emissions (as demonstrated previously for δ13C signatures across northern European wetlands). Weekly sampling for methane δ13C and δ2H was started at Pallas Sammaltunturi in northern Finland in August 2022. These data will be used to identify the regional source signature of emissions.

How to cite: Fisher, R., Woolley Maisch, C., Lowry, D., France, J., Rockmann, T., van der Veen, C., Fowler, C. M. R., and Nisbet, E. G.: Measurement of the isotopic signature of boreal wetland methane emissions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16482, https://doi.org/10.5194/egusphere-egu23-16482, 2023.

EGU23-16842 | Orals | BG1.7

Magnitude, trends, and variability of the global ocean carbon sink from 1985-2018 

Timothy DeVries, Kana Yamamoto, and Rik Wanninkhof and the RECCAP2 Global Ocean Team

The RECCAP2 global ocean project provides an assessment of the mean, trends, and variability of the global ocean carbon sink for the period 1985-2018. The analysis is based on a comprehensive assessment of models and observation-based products, including global ocean biogeochemical models (GOBMs), pCO2 observation-based air-sea CO2 flux products, ocean data assimilation models, and DIC-observation based products. We find that the mean ocean CO2 sink from 1985-2018 is -1.7±0.3 PgC yr-1 as diagnosed by pCO2-observation based air-sea CO2 flux products. The dominant component of the global air-sea CO2 flux is the oceanic uptake of anthropogenic CO2, which is estimated at between -2.0 to -2.6 PgC yr-1 using a range of GOBMs, assimilation models and DIC-based products. The second largest component of the global air-sea CO2 flux is the outgassing of terrestrially-derived CO2, which is estimated at 0.65±0.3 PgC yr-1 but is not yet fully resolved by RECCAP2 models. The trend in the global air-sea CO2 flux from 1985-2018 ranges from -0.26 PgC yr-1 decade-1 in the GOBMs to -0.39 PgC yr-1 decade-1 in the pCO2 products. Over the 2001-2018 period, when the pCO2-based estimates benefit from improved data coverage, they predict a strengthening trend in the ocean carbon sink of -0.63 PgC yr-1 decade-1. This is driven primarily by the trend in anthropogenic carbon uptake of -0.41 PgC yr-1 decade-1, and secondarily by a climate-forced trend of -0.28 PgC yr-1 decade-1. This climate-forced strengthening of the ocean carbon sink since 2001 is not diagnosed in the GOBMs, and the reasons for this trend remain unclear. We find that the interannual to decadal variability of the global carbon sink is mainly driven by climate variability, with the climate-driven variability exceeding the CO2-forced variability by 2-3 times. GOBMs suggest that the climate-driven variability is about 4-8% of the global mean carbon sink, while the climate-driven variability is about 9-14% of the global mean flux in the observation-based pCO2 products. In all, the RECCAP2 analysis provides a state-of-the-art summary of our current knowledge of the ocean carbon sink, and the mechanisms driving its magnitude, trends, and variability over time.

How to cite: DeVries, T., Yamamoto, K., and Wanninkhof, R. and the RECCAP2 Global Ocean Team: Magnitude, trends, and variability of the global ocean carbon sink from 1985-2018, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16842, https://doi.org/10.5194/egusphere-egu23-16842, 2023.

EGU23-16920 | Orals | BG1.7

Greenhouse gas budget for South Asia region 

Atul Jain, Jatin Anand, Naveen Chandra, and Prabir Patra

Understanding climate change and possible solutions to recent increases in concentrations of major GHG concentrations dependent upon quantifying the emission inventory of these gases. The objective of this study, which is part of the Regional Carbon Cycle Assessment and Processes-2 (RECCAP2) project, is to estimate the country-specific GHGs budget (sources and sinks) for the South Asia (SA) region for the 2010s. The region comprises seven countries: Afghanistan, Bangladesh, Bhutan, India, Nepal, Pakistan, and Sri Lanka. Each country in the region is experiencing rapid changes due to the continuous development of agriculture, deforestation, reforestation, afforestation, and the increased demand for land for people to live in. In this study, we synthesize top-down (TD) and bottom-up (BU) model results and ground-based and other data sets to estimate the GHG emissions for carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) due to anthropogenic and natural biospheric activities. Major contributing factors include net biome productivity, fossil fuel emissions, inland waters, and wetland and wet/dry soils. Our study shows that the SA region was the net source of atmospheric CO2 for the 2010s. BU estimates for CO2, CH4, and N2O emissions were 1974, 1047, and 715 Tg CO2eq, and TD estimates were 2010, 1247, and 799 Tg CO2 eq. The total GHG emission for the region based on BP and TD were 3736 and 4056 Tg CO2 eq. Among SA countries, India was the most significant contributor to the total GHG emission.

How to cite: Jain, A., Anand, J., Chandra, N., and Patra, P.: Greenhouse gas budget for South Asia region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16920, https://doi.org/10.5194/egusphere-egu23-16920, 2023.

EGU23-17328 | Orals | BG1.7

RECCAP2 – Southern Ocean carbon fluxes and storage 

Lavinia Patara, Judith Hauck, and Luke Gregor and the RECCAP2 Southern Ocean team

Cool temperatures, vigorous overturning circulation, and high biological productivity make the Southern Ocean a key region for the air-sea CO2 exchanges. It is also the main gateway for anthropogenic CO2 into the ocean owing to the upwelling of old water masses with low anthropogenic CO2 concentration, and the transport of the newly equilibrated surface waters into the ocean interior. Here we present results from the Southern Ocean chapter of RECCAP2, which is the Global Carbon Project’s second systematic study on Regional Carbon Cycle Assessment and Processes. We analyse Southern Ocean contemporary carbon fluxes and anthropogenic carbon accumulation in 1985-2018 from a wide range of global ocean biogeochemical models (GOBMs), surface ocean pCO2-based data products (pCO2-products), and data-assimilated models, with the aim of identifying patterns of regional and temporal variability, model limitations and future challenges. Our results highlight agreement of GOBMs and pCO2-products on the mean Southern Ocean contemporary CO2 uptake (0.75 ± 0.28 PgC yr-1 and 0.74 ± 0.07 PgC yr-1 respectively). Compared with RECCAP1 (where the database of model- and observation-based estimates was significantly smaller), the new estimates suggest a weaker sink, possibly due to better representation of winter outgassing. Strong discrepancies exist between GOBMs and pCO2-products in seasonality and trend estimates between 1985-2018. The pCO2-products show the presence of a stagnation in uptake through the 1990’s followed by a rapid increase in uptake, while GOBMs show consistent uptake throughout the 1985-2018 period. On a regional level, the subtropical seasonally stratified (STSS) biome has the largest air-sea CO2 flux with uptake of CO2 peaking in winter, whereas the ice (ICE) biome is characterised by a generally small magnitude of fluxes into and out of the ocean and a pronounced seasonal cycle with the largest ocean uptake of CO2 in summer. Connecting these two, the subpolar seasonally stratified (SPSS) biome has intermediate flux magnitude, with GOBMs showing spread in the strength of winter outgassing and difficulties in simulating the strongest CO2 uptake in summer. The biases in GOBMs originate mainly from the non-thermal component of air-sea CO2 flux, and in particular from the difficulty in simulating the competing effects of circulation and biology on carbon draw-down in summer. Our analysis reveals a distinct zonal asymmetry (secondary to the latitudinal gradient) between the Atlantic, Pacific and Indian sectors. The zonal asymmetry is observed in the mean uptake and amplitude of the seasonal cycle rather than the phasing of the seasonal cycle. GOBMs show a 20% spread and an overall underestimate of their simulated anthropogenic carbon accumulation, pointing to insufficient water mass formation and interior ventilation. These first results confirm the global relevance of the Southern Ocean carbon sink and highlight the strong regional and interannual variability of the Southern Ocean carbon uptake in connection to physical and biogeochemical processes. 

How to cite: Patara, L., Hauck, J., and Gregor, L. and the RECCAP2 Southern Ocean team: RECCAP2 – Southern Ocean carbon fluxes and storage, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17328, https://doi.org/10.5194/egusphere-egu23-17328, 2023.

EGU23-391 | ECS | Posters on site | BG1.8

Temporal factors in the high latitude eddy covariance network design 

Martijn Pallandt, Martin Jung, and Mathias Goeckede

High latitude regions are increasingly affected by climate change, where large stocks of carbon sequestered in permafrost are at risk of being released. Monitoring this change is therefore vital for our understanding of  the Arctic and global climate, but adverse conditions and the heterogeneity of Arctic landscapes make it exceptionally challenging to gain a comprehensive observational view of the carbon cycle. In this work we explore the growth of the high latitude eddy covariance (EC) network, and evaluate ways to improve its design both from a spatial and temporal aspect to better monitor this vital region. We utilise the relative extrapolation index (EI) metric, a method to assess upscaling errors as a factor of a location's distance in predictor variable space to the EC network. Our EC site survey, last updated in 2022, identified 213 site locations in the Arctic, of which 124 are currently active. Of these active sites, 79% intend to remain active for 5 years or longer, although on average these sites only have 3.1 years of funding. We investigated the effect of limited site activity periods on the network, and found that if sites only stayed active for a maximum of 36 month (3 full years) or 18 month (3 full summers), the network’s mean EI would increase by 27.3 and 24.5 percentage points, respectively. This deterioration in network data coverage is similar to setting the network back to 2012 and 2008, i.e. a time when fewer sites by far were active. In addition, we investigated the effect of long time series of data, and the optimal configuration of the network in depth versus breadth. For the former, our results show that even for time series that are already long, adding more data years still contributes to increasing network performance overall. For the latter, we find that with total site-months remaining constant, many sites with fewer site-months results in a lower EI than a few sites with many site-months. Summarising, our findings demonstrate that a top-down network management should ideally combine long-term monitoring sites with observations that are rotated between multiple observation sites, to capture both long-term trends and spatial heterogeneity in exchange flux rates. 

How to cite: Pallandt, M., Jung, M., and Goeckede, M.: Temporal factors in the high latitude eddy covariance network design, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-391, https://doi.org/10.5194/egusphere-egu23-391, 2023.

Groundwater is one of the largest continental carbon reservoirs and tightly linked to globally significant carbon fluxes such as uptake on land, evasion from inland waters and delivery to oceans. Despite emerging evidence that these fluxes are sensitive to environmental changes, long-term trends in groundwater carbon dynamics remain widely unknown. Here I show that dissolved inorganic carbon and carbon dioxide concentrations in groundwater have increased on average by 29% and 48%, respectively, across Sweden (55−68°N) during 1980−2020. I attribute these changes mainly to a partial recovery from historic atmospheric sulfate deposition and associated shifts in weathering pathways in acid-sensitive bedrock, but also to enhanced soil respiration as a likely consequence of climate and land use changes. The results highlight previously neglected significant long-term and large-scale dynamics in groundwater carbon cycling and have implications for the pathways and time scales through which carbon is cycled through the land - inland water - ocean continuum. The observed dynamics should be included in carbon cycle models for accurate evaluations and predictions of the effects of environmental changes on regional and global carbon fluxes.

How to cite: Klaus, M.: Rising carbon dioxide concentrations in Swedish groundwater during 1980−2020, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1265, https://doi.org/10.5194/egusphere-egu23-1265, 2023.

EGU23-1744 | Posters on site | BG1.8

Carbon dioxide and methane fluxes measurement for tundra ecosystem with ponds in High Arctic 

Namyi Chae, Hyewon Hwang, Taejin Choi, and Bang Yong Lee

In this study, CO2 and CH4 fluxes were measured in the tundra ecosystem in order to evaluate the potential future sensitivity of the carbon cycle to climate change using chamber systems and eddy covariance methods during summer in 2019 and 2022 in Canada. The study site is located on dry tundra with ponds in high-arctic near Cambridge Bay, Nunavut, Canada (69°7'47.7"N, 105°3'35.3"W). The vegetation cover around the site is mainly covered with dwarf-shrubs, graminoids, and lichens. CO2 and CH4 fluxes were examined to understand the mechanism of the carbon cycle over the tundra ecosystems with the pond. From chamber methods, the variability of net CO2 exchange was more sensitive to grass of wet condition than vegetation of dry condition and the variability and magnitude of CH4 emission near the pond was larger than that of dry condition. The emission CO2 and CH4 fluxes were examined positive relationship at almost bare soil of wet condition and negative relationship at various vegetation at dry condition. Net ecosystem exchange, ecosystem respiration, and gross primary production were measured or calculated using the both methods to investigate the influence of the ecosystem with ponds in the tundra carbon cycle. This study was supported by a National Research Foundation of Korea grant from the Korean government (MSIP) (NRF-2021M1A5A1065679 and NRF-2021R1I1A1A01053870).  

How to cite: Chae, N., Hwang, H., Choi, T., and Lee, B. Y.: Carbon dioxide and methane fluxes measurement for tundra ecosystem with ponds in High Arctic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1744, https://doi.org/10.5194/egusphere-egu23-1744, 2023.

Wetlands play an important role in the carbon balance of the Arctic. All wetland types are characterized by an individual combination of hydrological conditions, soils, vegetation cover, etc. These characteristics influence their feedback with current and future climate conditions, and therefore also their greenhouse gas exchange processes. While most climate models distinguish only one or two types of wetlands, biogeographical approaches define at least ten types of wetlands in the Arctic.

Improving the representation of wetland ecology in carbon upscaling studies in the Arctic requires finding the balance between the diversity of wetlands, including their variability in responses to climate forcing, and the information that is commonly available to represent them in modelling frameworks. On the one hand, a larger number of classes allows a more precise description of the conditions and characteristics of the fluxes within each class. On the other hand, more classes also mean less information per class, and thus more gaps that need to be interpolated.

To support the development of a refined classification scheme, we first built a database on Arctic wetland characteristics, including measured carbon pools and fluxes, based on the available information from published studies. Our database covers the period 1988 – 2019, with observations for all seasons available. Most data was taken from flux chamber studies, since this technique allows to resolve the highly heterogeneous mosaic of landcover, environmental conditions, vegetation and consequently GHG fluxes that characterize large fractions of the Arctic. For all plots, general (coordinates, time of measurements, etc.), physical (pH, vegetation composition, water table, etc.) site characteristics and CH4 and CO2 fluxes were collected. However, for some of these parameters, data coverage turned out to be too sparse to complete analyses. For example, permafrost depth, pH, and water table level cover only 45, 15 and 34% of all available plots. To improve this situation, remotely-sensed data was included, allowing to equally cover all measurement points, albeit often with less accuracy.

Based on statistical processing using agglomerative hierarchical cluster analysis, we divided all observations into wetland categories based on their CO2 and CH4 flux signatures and the response to dominant environmental factors. We present the most successful classifications for different total numbers of classes, allowing to base the choice of scheme on the information that is available for a specific modelling study.

How to cite: Ivanova, K. and Goeckede, M.: Optimization of a classification scheme for Arctic wetlands to support carbon and energy flux upscaling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1905, https://doi.org/10.5194/egusphere-egu23-1905, 2023.

Wildfire is the most important disturbance agent in boreal forests. These disturbances play a major role in the boreal forest carbon cycle. They lead to direct CO2 and CH4 emissions during the active fire phase and to long-lasting post-fire impacts on net CO2 and CH4 fluxes through changes in forest structure and in microclimatic conditions. For example, a forest’s ability to minimise differences between land surface and air temperature can preserve permafrost and can lower soil temperatures and thus soil respiration. Fire and post-fire succession are linked to diverse changes in ecosystem function and structure shaping land-atmosphere interactions and, thus, forest microclimate for decades after the disturbance event. However, the mechanisms behind changes in boreal forest microclimate remain uncertain hampering our understanding of carbon cycle impacts of wildfires. Here, we analyse surface energy balance observations from 17 eddy covariance flux tower sites across fire disturbance chronosequences in the North American boreal biome to identify the main drivers of post-fire changes in land surface-air temperature gradients. We use 102 years of observations to quantify winter and summer changes in important ecosystem properties such as evaporative fraction, aerodynamic conductance, and albedo following stand-replacing fire disturbances. Then, we link changes in ecosystem properties to decadal changes in surface-air temperature gradients.

We find that the summer daytime surface-air temperature gradient increases after the fire disturbance indicating reduced ability to cool the land surface during the warm summer months. However, in the winter, the daytime temperature gradient becomes smaller. Decreased aerodynamic conductance contributes mainly to the post-fire surface heating in the summer while increasing albedo mainly explains winter cooling. Evaporative fraction increases initially in the first few decades after the post-fire disturbance. However, during drought years, the evaporative fraction declines rapidly. Our results provide important insights into fire impacts on microclimatic conditions and ground thermal regimes in boreal forests and highlight the reduced capacity of post-fire forests to reduce land surface temperatures during heatwave events. The findings have the potential to contribute to a better mechanistic understanding of post-fire permafrost thaw and soil respiration changes.

How to cite: Helbig, M. and Daw, L.: Boreal forests on fire - Decadal wildfire impacts on boreal forest microclimate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3533, https://doi.org/10.5194/egusphere-egu23-3533, 2023.

EGU23-4338 | ECS | Orals | BG1.8

Greenhouse gas dynamics across a latitudinal gradient of thermokarst lakes 

Nicolas Valiente, Oriol Grau, Victoria Martin, Ivan Janssens, Inge Van de Putte, Peter Dörsch, Hannes Schmidt, and Andreas Richter

The Arctic is warming at a faster rate than the rest of the planet due to climate change. The warmer temperatures are causing, among other effects, the permafrost to thaw. When ice-rich permafrost thaws, thermokarst features form due to subsidence of the ground surface and the creation of dynamic depressions, basins, and lakes. As a result, the hydrological cycle in these latitudes is intensifying, causing an increase of nutrients and organic carbon in surface waters. Such impacts on freshwaters affect microbial community composition, and thus, these systems are good sentinels to study processes in primary ecological succession related to ecosystem processes such as productivity and greenhouse gas (GHG) emissions. This study aims to improve the current understanding of microbial processes leading to release of GHG in thermokarst lakes. To that end, we sampled a total of 12 thermokarst basins in August 2022 along a latitudinal gradient (67ºN - 69ºN) in the Northwestern Territories (Canada). The basins were selected so that half were in the taiga biome and half in the tundra biome. In addition, based on satellite images and in-field observations, half of the lakes sampled were in expansion and the other half were undergoing drainage. Water samples were collected for the analysis of GHGs (CH4, CO2, N2O), major ions, dissolved nutrients (organic C, δ13C-DOC, organic and inorganic -N) and microbial community composition (16S rRNA gene metabarcoding). We used Ar-corrected gas saturation of each GHG as a proxy of net metabolic changes. Our first results show that both expanding and shrinking lakes were strongly oversaturated in CH4 andCO2, slightly saturated in N2O, and slightly undersaturated in O2, pointing out higher respiration activity than primary production. Microbial mineralization of organic matter was used as a proxy for GHG production. We found higher concentrations of dissolved organic C in shrinking lakes compared to expanding ones. Following the latitudinal gradient (i.e. biomes), higher temperatures were found in lakes sampled in the taiga compared to those located in tundra, together with deeper permafrost table depths. In surface waters, pH values and dissolved O2 concentrations were significantly higher in tundra lakes compared to taiga lakes, probably as a result of lateral DOM fluxes in more productive ecosystems (i.e. boreal forests). Differences between microbial communities in both biomes are therefore expected, which we will verify once the ongoing sequencing analyses are available. Our study advances the current knowledge of GHG dynamics in thermokarst lakes and helps to predict future effects of climate change impacts in northern latitudes.

How to cite: Valiente, N., Grau, O., Martin, V., Janssens, I., Van de Putte, I., Dörsch, P., Schmidt, H., and Richter, A.: Greenhouse gas dynamics across a latitudinal gradient of thermokarst lakes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4338, https://doi.org/10.5194/egusphere-egu23-4338, 2023.

EGU23-5011 | ECS | Orals | BG1.8

Impact of the Long-Term Drainage on the Eddy-Covariance Fluxes in Northern High Latitude Permafrost Regions 

Abdullah Bolek, Mark Schlutow, Tarek El-Madany, Olaf Kolle, Martin Heimann, and Mathias Goeckede

In the context of global climate change, permafrost thaw in northern high-latitude territories is becoming a major concern due to the vast amount of organic carbon that is stored within this region. To accurately predict the feedback between Arctic permafrost carbon pools and future climate change, detailed insight into current carbon cycle processes and their environmental controls is imperative. A highly valuable data source for this purpose are continuous observations of turbulent exchange fluxes of carbon (e.g. CO2 and CH4 fluxes) and energy (e.g. fluxes of sensible and latent heat) with the eddy-covariance technique, in combination with the monitoring of environmental parameters such as e.g. air or soil temperature and moisture, radiation,  atmospheric turbulence, water table levels, precipitation, and snow depth.

In this study, we evaluate the effect of drainage on vertical carbon fluxes and environmental parameters within a Northeast Siberian wet tundra permafrost ecosystem. Our experiment includes two co-located eddy-covariance sites, one reflecting disturbed conditions affected by a drainage system which was built in 2004, and the other as an undisturbed control site. Both towers were identically outfitted with eddy covariance instruments mounted on 5 m tall towers on the floodplain of the Kolyma River near Chersky (68.75 º N, 161.33º E) in Northeast Siberia, Russia. The dataset analyzed here covers the period from July 2013 to December 2021, including continuous coverage throughout the winter seasons. We present a statistical analysis of the long-term trends in the environmental parameters and surface-atmosphere exchange fluxes at both sites. In addition, we relate the carbon and heat fluxes at both sites in the spectral and temporal domain to the inter-annual variability in climate conditions, which include extremes in both summer (temperature, precipitation) and winter (snow cover) conditions. Finally, we show the annual carbon budget of both sites, with a specific focus on the long-term impact of the drainage on carbon cycle process.

How to cite: Bolek, A., Schlutow, M., El-Madany, T., Kolle, O., Heimann, M., and Goeckede, M.: Impact of the Long-Term Drainage on the Eddy-Covariance Fluxes in Northern High Latitude Permafrost Regions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5011, https://doi.org/10.5194/egusphere-egu23-5011, 2023.

Gas hydrates are known to be an enormous potential energy resource that are accumulated worldwide, especially in the polar regions, and yet the estimates for this resource remain uncertain. In the Arctic region, methane emissions into the atmosphere are a substantial factor in global warming that poses a great danger to the environment. Previously, several studies have been conducted to estimate the gas hydrates in the Arctic to ease such problems despite the need for more data compared to conventional reserves. In the western continental margin of the Chukchi Plateau, the sea mound morphologies were first discovered, and gas hydrate samples were obtained via gravity coring during the first expedition in 2016. In the following expedition in 2018, an intensive gas hydrate exploration including the single-channel seismic survey was conducted in the area of mound morphologies and identified the local bottom simulating reflectors. Consequently, an extensive multichannel seismic survey was conducted in 2019 to investigate the geophysical characteristics of widely distributed gas hydrates in the western continental margin of the Chukchi Plateau. The objective of this study is to estimate the potential volume of gas hydrate resources in the Chukchi Plateau based on the geophysical data. From this study, the distribution of bottom-simulating reflectors and local gas hydrate saturations were derived from the geophysical data. The gas hydrate saturation model in this study area was constructed using the kriging method with few geological assumptions. Then, the total volume of gas hydrates in the western continental margin of the Chukchi Plateau was proposed. The results of this study will provide basic information on the estimates of gas hydrates in the western continental margin of the Chukchi Plateau and contribute to assessing the size of the associated volume of methane emissions due to global warming.

How to cite: Choi, Y., Kang, S.-G., Choi, Y., and Hong, J. K.: Estimation of potential gas hydrate resources based on the geophysical data in the western continental margin of the Chukchi Plateau, the Arctic Ocean, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5019, https://doi.org/10.5194/egusphere-egu23-5019, 2023.

EGU23-6128 | Orals | BG1.8

Rhizosphere priming in a warming Arctic: Are peatlands insusceptible? 

Birgit Wild, Sylvain Monteux, Bernd Wendler, Gustaf Hugelius, and Frida Keuper

Rapid warming is currently accelerating Arctic carbon cycling, including increased permafrost thaw and CO2 production from soil organic matter decomposition, but also CO2 uptake by plants. Plants can additionally stimulate soil organic matter decomposition near their roots, via the rhizosphere priming effect. In a recent modeling study, we showed that priming can accelerate Arctic soil carbon loss at a globally relevant rate, and spatial analysis pointed to large potential contributions from carbon-rich permafrost peatlands. At the same time, the high carbon content of peatlands might render them insusceptible to input of easily available organic compounds by plant roots, which is considered a key component of priming. We here investigated the susceptibility of permafrost peat soils to priming by plant compounds under aerobic conditions that resemble the dominant rooting zone. To that end, we combined a 30-week laboratory incubation of peat soils from five circum-Arctic locations, with a literature meta-analysis of priming studies of Arctic peat and mineral soils. The combined experimental and literature data showed substantially and significantly weaker priming susceptibility of peat than mineral soils. Organic carbon addition increased CO2 production from soil organic matter in mineral, but not in peat soils. Organic nitrogen addition had a significant effect on both sample types, but that of peat was much weaker. These observations point at fundamental, mechanistic differences in the response of peat and mineral soil organic matter decomposition to changing carbon and nitrogen availability. In a new model sensitivity analysis, we show that insusceptibility of peatlands to priming would substantially reduce estimates of priming-induced carbon loss from the circum-Arctic. While our study suggests a limited effect of plant-released organic compounds on peat decomposition, it does not preclude a vegetation effect on decomposition under natural conditions. The large carbon stocks of circum-Arctic peatlands and expected changes in vegetation and drainage, call for increased efforts to quantify the combined effect of living plants on soil processes beyond carbon input.

How to cite: Wild, B., Monteux, S., Wendler, B., Hugelius, G., and Keuper, F.: Rhizosphere priming in a warming Arctic: Are peatlands insusceptible?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6128, https://doi.org/10.5194/egusphere-egu23-6128, 2023.

EGU23-6610 | ECS | Posters on site | BG1.8

ARCLIM: bioclimatic atlas of the terrestrial Arctic 

Mika Rantanen, Matti Kämäräinen, Pekka Niittynen, Gareth K Phoenix, Jonathan Lenoir, Ilya Maclean, Miska Luoto, and Juha Aalto

The warming of the Arctic and its consequences for the global climate system have become one of the strongest manifestations of human-induced climate change. Over the four decades, the Arctic has warmed three to four times faster than globally. In addition to the long-term trend in average temperatures, extreme weather events are becoming increasingly frequent causing disturbances to the Arctic terrestrial ecosystems. 

Many existing datasets primarily concentrate on seasonal precipitation and temperature at coarse spatial (10-100 km) and temporal (30-year average climatologies) resolutions forming the basis of current understanding of how Arctic ecosystems will respond to climate change. For this reason, the conventional datasets likely leave out many ecologically significant aspects of the Arctic climate relevant for biological or biogeochemical processes. For instance, snow cover duration, rain-on-snow events, or extreme wind events are known to be important variables for Arctic ecology that may not be adequately represented by the more widely used climate statistics.

Here, we introduce a new dataset of bioclimatic indices relevant for investigating the changes of Arctic terrestrial ecosystems. The dataset, called ARCLIM, consists of several climate and event-type indices for the northern high-latitude land areas. The indices are calculated from the hourly ERA5-Land reanalysis data for 1950-2021 in a spatial grid of 0.1 degree (~9 km) resolution. We provide the indices in three subsets: (1) the annual values during 1950-2021; (2) the average conditions for the 1991-2020 climatology; and (3) temporal trends over 1951-2021. 

The 72-year time series of various climate and event-type indices draws a comprehensive picture of the Arctic bioclimate variability. We hope that the ARCLIM dataset opens new research opportunities aiming to better understand the impacts of climate change in Arctic terrestrial ecosystems.

How to cite: Rantanen, M., Kämäräinen, M., Niittynen, P., Phoenix, G. K., Lenoir, J., Maclean, I., Luoto, M., and Aalto, J.: ARCLIM: bioclimatic atlas of the terrestrial Arctic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6610, https://doi.org/10.5194/egusphere-egu23-6610, 2023.

EGU23-7504 | ECS | Orals | BG1.8 | Highlight

Increasing methane emissions from the North Slope of Alaska since 2000 and late Autumn-Winter emissions from multiple Arctic regions 

Rebecca H. Ward, Anita L. Ganesan, Colm Sweeney, John Miller, Mathias Goeckede, Tuomas Laurila, Juha Hatakka, Viktor Ivakhov, and Alexander Makshtas

Large stores of carbon frozen in the Arctic as permafrost are under threat of thawing as temperatures in the Arctic increase at a rate four times that of the global mean. This study uses recent atmospheric data from the North Slope of Alaska and Northeast Siberia to provide the most up-to-date assessment of emissions and trends from these two major high-latitude regions.

We use two methods to quantify emissions and assess trends across different seasons: 1) Using 35 years of data from Barrow, Alaska, a wind sector method that quantifies trends in emissions by calculating concentration enhancements over background using wind direction to identify the land sector (first used in Sweeney et al., 2016), and 2) using Barrow data and recent data from three Siberian stations, an inversion method with the high-resolution atmospheric transport model NAME that quantifies both emissions and trends from these regions. We use results from these two approaches to quantify the temperature sensitivity (Q10) of soils based on correlations between surface air and ground temperatures with methane emissions.

With the inclusion of atmospheric concentration data after 2015, we now show that land emissions from the North Slope of Alaska have been increasing since 2000, reflecting a change from previous analyses, which showed no significant increase in summertime methane emissions between 1986-2014 (Sweeney et al., 2016). We find significant emissions from the late shoulder season (Autumn-Winter), which has historically been undermeasured and underrepresented in models and emissions inventories, in this region of Alaska as well as two North-eastern Siberian locations, the Taymyr Peninsula and the East Siberian Lowlands. We show that emissions during this late-season have been growing over the past two decades at a rate similar to summer-time emissions.

Our results based on long-term atmospheric data can be used to show that important change is happening in the Arctic, with an increasing emissions trend and the presence of late shoulder season emissions.

How to cite: Ward, R. H., Ganesan, A. L., Sweeney, C., Miller, J., Goeckede, M., Laurila, T., Hatakka, J., Ivakhov, V., and Makshtas, A.: Increasing methane emissions from the North Slope of Alaska since 2000 and late Autumn-Winter emissions from multiple Arctic regions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7504, https://doi.org/10.5194/egusphere-egu23-7504, 2023.

EGU23-8337 | Posters on site | BG1.8

Remineralization of soil-derived dissolved organic carbon in the high Arctic fjord (Kongsfjorden) 

Katarzyna Koziorowska-Makuch, Laura Bromboszcz, Przemysław Makuch, Izabela Pałka, Aleksandra Winogradow, and Karol Kuliński

Ongoing climate change has a significant impact on marine and terrestrial polar ecosystems. The increased melting, and retreat of glaciers, as well as the permafrost thawing, intensify the transport of dissolved organic matter from land to Arctic fjords. It has been estimated that the permafrost surface layer contains as much as 1035 ± 150 Pg of organic carbon (Hugelius et al., 2014), so even a small release can significantly change the carbon loads reaching the fjords. Although there are quantitative estimations of the dissolved organic carbon (DOC) delivered from land, the fate of the soil-derived DOC in fjords remains highly unknown. It is still unclear to what extent this DOC pool is bioavailable and how fast can it be remineralized. Therefore, the following research objectives have been formulated: (1) to quantify the shares of labile, semi-labile, and refractory fractions in the soil-derived DOC, and (2) to estimate remineralization rate constants and half-life times for different bioavailable fractions of DOC. This has been done through the 180-days-lasting incubation experiments of the DOC released from soils (soil leachates) mixed with the seawater from adjacent fjord. At the beginning and after 1, 2, 3, 5, 9, 19, 29, 65, 90, and 180 days of incubation, the individual samples were collected to measure DOC concentrations. For the study site, the catchments of two rivers in Kongsfjorden (West Spitsbergen, Svalbard) - Bayelva River and Londonelva River were selected. Bayelva River is 4 km long, with a glacierised catchment area of 32 km2, which is almost entirely underlain by permafrost with a seasonal active layer (Killingtveit, 2004). Londonelva River is located on Blomstradøya (small island in Kongsfjorden) and is characterized by a small (0.7 km2) de-glacierised catchment area. The results indicate that the soil leachates contain a lot of DOC (420 μmol L-1 in the Bayelva catchment and 2730 μmol L-1 in the Londonelva catchment), which is highly bioavailable - 61% and 66% of DOC was remineralized during the incubation experiment, respectively. This high bioavailability of terrestrial DOC indicates that its supply has the potential to play an essential role in sustaining the bacterial loop in the fjord and, through the CO2 release, to amplify ocean acidification in the coastal zone. The obtained results contribute to a better understanding of the processes shaping the carbon cycling in the Arctic fjords (and likely in other polar regions).

How to cite: Koziorowska-Makuch, K., Bromboszcz, L., Makuch, P., Pałka, I., Winogradow, A., and Kuliński, K.: Remineralization of soil-derived dissolved organic carbon in the high Arctic fjord (Kongsfjorden), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8337, https://doi.org/10.5194/egusphere-egu23-8337, 2023.

EGU23-10051 | ECS | Posters on site | BG1.8

The impacts of regional Arctic lake change on remotely sensed methane emission hotspots in Alaska, USA 

Clayton D. Elder, David R. Thompson, Latha Baskaran, Ingmar Nitze, Guido Grosse, Nicholas Hasson, Katey M. Walter Anthony, and Charles E. Miller

Arctic and boreal wetlands and lakes are experiencing complex ecological changes as a result of warming. The potential for rapidly thawing permafrost to promote large increases in methane (CH4) emissions via ground subsidence and ponding (thermokarst), and permafrost carbon mineralization is of particular concern for accelerating the permafrost carbon feedback (PCF) [Turetsky et al. 2020]. However, complex hydrological dynamics produce large uncertainties regarding the sign and magnitude of carbon loss in modeling and forecasting efforts. Determining CH4’s current and future contributions to the PCF is challenging due to sparse observations, high spatiotemporal variability, and heterogeneous Arctic landscapes. As a result, top-down (observation-based) and bottom-up (model/inventory-based) evaluations of annual Arctic and boreal CH4 emissions disagree by 50-200% [McGuire et al. 2012; Peltola et al. 2019]. Constraining the current budget and forecast uncertainty in future Arctic emissions will require scale-bridging approaches that reconcile fine spatiotemporal variability and regional to continental scale coverage. To this end, we compiled multiple large remote sensing datasets to study relationships between Arctic lake and thermokarst landscape morphology trends with remotely-sensed (AVIRIS-NG) CH­4 emission hotspot detections. Preliminary analyses from a lake-and-wetland-rich 1,750 km2 study area of the Yukon Kuskokwim Delta, AK, USA reveal discrete correlations between recently wetted areas and CH4 hotspot detections. However, in an analysis of over 1,200 lakes > 1 ha, hotspots were detected in greater abundance surrounding lakes that have shrunk in area since 1999 (p < 0.05) (Fig. 2). Our preliminary results imply a complex response of CH4 emissions surrounding dynamic permafrost environments. Ongoing analyses seek to further elucidate patterns related to waterbody size, permafrost ice and carbon contents, and relationships between terrestrial and limnetic hotspot detections. 

How to cite: Elder, C. D., Thompson, D. R., Baskaran, L., Nitze, I., Grosse, G., Hasson, N., Walter Anthony, K. M., and Miller, C. E.: The impacts of regional Arctic lake change on remotely sensed methane emission hotspots in Alaska, USA, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10051, https://doi.org/10.5194/egusphere-egu23-10051, 2023.

EGU23-10145 | Posters on site | BG1.8 | Highlight

Seasonal increase of methane emissions linked to warming in Siberian tundra 

Torsten Sachs, Norman Rößger, Christian Wille, Julia Boike, and Lars Kutzbach

Methane (CH4) is a strong greenhouse gas that accelerates climate change, yet its emissions from wetlands in general and Arctic permafrost-affected wetlands in particular remain very uncertain in the global CH4 budget. Arctic CH4 sources and the expected effect of permafrost thaw on these sources have gained much attention by the public, media, policy makers, and researchers during the past decade, but neither inversion nor process-based models provide clear trends in emissions and there has not been any observational evidence for increasing CH4 emissions from Arctic permafrost ecosystems.

Here, we provide this observational evidence. 

Based on the longest record of direct Arctic CH4 flux observations acquired since 2002 at a Siberian tundra site using the eddy covariance method, we found an increase in the early summer (June and July) CH4 emissions by 1.9 ± 0.7 % yr-1 since 2004 along with a strong increase in June air temperatures of 0.3 ± 0.1 °C yr-1. Although the tundra’s maximum source strength in August has not yet changed and the overall mean annual emissions of 171.5 ± 12.3 mmol m−2 yr−1 remain in the lower half of the published range, the increase in early summer methane emissions shows that atmospheric warming has begun to affect the methane flux dynamics of permafrost-affected ecosystems in the Arctic. This is especially noteworthy, given the very thick and cold continuous permafrost in the study area compared to most other observational sites.
While the observed changes clearly happen in the early warm season, we also estimate 39 % of the annual emission to originate from the re-freezing and frozen period, highlighting the importance of the cold season for annual permafrost CH4 emission estimates and the substantial challenges in achieving continuous data coverage in the Arctic winter.

How to cite: Sachs, T., Rößger, N., Wille, C., Boike, J., and Kutzbach, L.: Seasonal increase of methane emissions linked to warming in Siberian tundra, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10145, https://doi.org/10.5194/egusphere-egu23-10145, 2023.

EGU23-10192 | ECS | Orals | BG1.8

Sea animals promote carbonyl sulfide (OCS) emissions from Antarctic tundra 

Wanying Zhang, Renbin Zhu, Yi Jiao, Robert C. Rhew, Bowen Sun, Riikka Rinnan, and Zeming Zhou

Carbonyl sulfide (OCS), the most abundant atmospheric sulfur-carrying gas, can contribute to regulating Earth’s radiative balance through forming sulfate aerosols. The bryophyte-dominated tundra lying over the ice-free Antarctica is an important terrestrial carbon sink and provides colonies for sea animals, such as penguins and seals, which remains hitherto unexplored concerning OCS biogeochemistry. Here, we measured OCS fluxes from the Antarctic tundra and coupled their fluxes to soil biogeochemical properties to explore OCS production and degradation processes. The bryophyte-dominated normal upland tundra was an OCS sink at -0.97 ± 0.57 pmol m-2 s-1, resulting from both bryophytes and OCS-metabolizing enzymes (e.g., carbon anhydrase, nitrogenase) secreted by soil microbes, such as Acidobacteria, Verrucomicrobia, Chloroflexi, and Mortierellomycota. In comparison, tundra within sea animal colonies was an OCS source up to 1.35 ± 0.38 pmol m-2 s-1, due to the input of organosulfur from sea animals and the animal-induced anaerobic soil environment, which promoted simultaneous abiotic OCS production in soil, and outweighed the biogenic OCS uptake by bryophytes and soil microbes. Furthermore, sea animal colonization shaped the soil microenvironment, affecting nutrient levels, pH and moisture, which may have reduced the abundances of OCS-metabolizing microbes and thereby OCS degradation and further unveiled concurrent OCS production. Basic calculation suggested that sea animals contribute about 107 metric tons yr-1 of OCS-S to the atmosphere. The strength of this OCS source is expected to increase in response to Antarctic warming. Overall, tundra ecosystems are important interfaces for OCS exchange and sea animals exert an impact on the sulfur cycle in coastal Antarctica.

How to cite: Zhang, W., Zhu, R., Jiao, Y., Rhew, R. C., Sun, B., Rinnan, R., and Zhou, Z.: Sea animals promote carbonyl sulfide (OCS) emissions from Antarctic tundra, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10192, https://doi.org/10.5194/egusphere-egu23-10192, 2023.

EGU23-10643 | ECS | Orals | BG1.8

Strategic expansion of the Arctic-Boreal carbon flux network 

Kyle Arndt and Susan Natali and the Permafrost Pathways Flux Steering Committee

Permafrost soils store vast amounts of carbon, twice as much as the atmosphere. With climate warming occurring at a rate three to four times the global average in Arctic-boreal ecosystems this carbon is at risk of being released to the atmosphere in the form of carbon dioxide or methane (hereby, carbon fluxes) exacerbating global climate warming. However, gaps in carbon flux data in high latitude ecosystems limit our ability to understand, upscale, model, and project carbon fluxes, which in turn limit our ability to set accurate emissions reduction targets to stay within globally agreed upon temperature thresholds such as 1.5 or 2°C. To address this, we are strategically expanding the informal Arctic-boreal carbon flux network through the installation of ~10 new eddy covariance sites and supporting expanded measurements (during winter and for CH4) at existing sites. To guide site selection decision making, we are using a representativeness analysis of the current eddy covariance network, determining the Euclidean distance in environmental data space using key carbon flux drivers at a 1 km2 resolution across the Arctic-boreal region (Pallandt et al., 2022). Analyses show a lack of representation in the high Arctic, Siberia, and Eastern Canada, and representation is substantially lower when considering only sites with year-round measurement or that measure methane, limiting our ability to estimate the full impact of carbon fluxes from the Arctic-boreal region. Additional consideration is given to logistical constraints, partnerships, and modeling gaps. Work has begun including a re-installation in Churchill, MB, and upgrades for year-round and additional instrumentation for 4 towers in Alberta and the Northwest Territories and a site in Iqaluit, NU. We will further synthesize existing network data to inform the Dynamic Vegetation [Model] Dynamic Organic Soil Terrestrial Ecosystem Model (DVM-DOS-TEM) model and use machine learning approaches to upscale Arctic-boreal carbon fluxes.

How to cite: Arndt, K. and Natali, S. and the Permafrost Pathways Flux Steering Committee: Strategic expansion of the Arctic-Boreal carbon flux network, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10643, https://doi.org/10.5194/egusphere-egu23-10643, 2023.

EGU23-10711 | ECS | Orals | BG1.8

Characterization of atmospheric methane release at hotspots in the outer Mackenzie River Delta 

Daniel Wesley, Scott Dallimore, Roger MacLeod, Torsten Sachs, and Dave Risk

Spatio-temporal patterns of methane (CH4) and carbon dioxide (CO2) release from natural sources needs to be better understood across the Arctic region. Climate change in the Arctic is occurring at a pace that may be 2 to 4 times the global average, and existing measurements derive from a limited number of field sites, and most originate during the growing season although important studies show that release continues during winter. The Mackenzie River Delta in the western Canadian Arctic holds thin and destabilizing permafrost, high organic content soils, a high proportion of wetlands, and vast natural gas occurrences at depth, all of which create high methane potential. In the present study, we conducted atmospheric CH4 and CO2 measurements using a mobile laboratory equipped with a greenhouse gas analyzer during the summer and winter. We also visited known aquatic and terrestrial CH4 flux hotspots, including pingos, lakes, river channels and wetlands, where we measured concentration transects and stable carbon isotope (13C-CH4) values to characterize CH4source and spatial pattern. Source stable carbon isotope (δ13C-CH4) signatures at hotspots ranged from -42 to -88 ‰ δ13C-CH4. Active surface microbial production was responsible for at least 4 of the 8 hotspots investigated, indicating that microbial production may be responsible for a greater number of CH4 hotspots than is indicated by previous studies in the region. Mobile surveys showed that shrubland, grassland and deep water were the most important ecosystems for CH4 and CO2 production during the wintertime and that low lying areas of the Delta had the highest atmospheric mixing ratios of CH4.

How to cite: Wesley, D., Dallimore, S., MacLeod, R., Sachs, T., and Risk, D.: Characterization of atmospheric methane release at hotspots in the outer Mackenzie River Delta, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10711, https://doi.org/10.5194/egusphere-egu23-10711, 2023.

EGU23-11027 | Orals | BG1.8

From Archaea to the atmosphere: linking above and belowground communities to scale methane and isotopic emissions across the Arctic 

Ruth Varner, Patrick Crill, McKenzie Kuhn, Dylan Cronin, Michael Palace, Carmody McCalley, Sophia Burke, Jia Deng, Scott Saleska, and Virginia Rich and the A2A and EMERGE project teams

High latitude peatlands are a significant source of atmospheric methane. Production, consumption and emission rates are spatially and temporally heterogeneous, resulting in a wide range of global estimates for the atmospheric budget of methane. Increasing temperatures in Arctic regions cause degradation of underlying permafrost, changing hydrology, vegetation and microbial communities, but the consequences of this for methane cycling, including stable methane isotopes, are poorly understood. We provide evidence of direct linkages between below ground methanogen communities and above ground plant communities that can be remotely sensed and used in model simulations to effectively predict methane and isotopic fluxes across the landscape. Combining remote sensing with biogeochemical modeling can be used to predict methane dynamics, including the fraction derived from hydrogenotrophic versus acetoclastic microbial methanogenesis. Applying this approach across heterogeneous discontinuous permafrost peatlands enables us to accurately predict isotopic emissions, which will help constrain the global role of Arctic methane emissions.

How to cite: Varner, R., Crill, P., Kuhn, M., Cronin, D., Palace, M., McCalley, C., Burke, S., Deng, J., Saleska, S., and Rich, V. and the A2A and EMERGE project teams: From Archaea to the atmosphere: linking above and belowground communities to scale methane and isotopic emissions across the Arctic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11027, https://doi.org/10.5194/egusphere-egu23-11027, 2023.

EGU23-11216 | Posters on site | BG1.8

Process-based simulation of nutrient (N, P, Si, Ca) effects on permafrost carbon cycling under present and future climate conditions 

Mathias Göckede, Fabrice Lacroix, Jörg Schaller, Peter Stimmler, and Sönke Zaehle

Many aspects regarding biogeochemical cycles in carbon-rich permafrost ecosystems remain poorly constrained to date, resulting in a major source of uncertainty for prognostic simulations of the global greenhouse gas budget, and the associated design of effective future climate policies. Only very few studies have investigated the role of nutrients on carbon cycle processes in Northern ecosystems, and existing data is particular limited for elements beyond nitrogen (N) and phosphorus (P). Consideration of their impacts may be particularly relevant for simulating a warmer future Arctic with substantially increased thaw depths, and associated input of nutrients from currently deep-frozen permafrost pools.

For the presented study, we enhanced a high-latitude version of the terrestrial ecosystem model QUINCY, which fully couples carbon (C), nitrogen (N) and phosphorus (P) cycles in vegetation and soil, with an additional first-order factor derived from soil incubation experiments that accounts for stabilization and mobilization of soil organic matter through Calcium (Ca) and Silicon (Si). In a preparation step, based on thaw depths of CMIP6 models we first computed the pan-Arctic scale magnitude of Si and Ca susceptible to release to the active layer under different climate warming scenarios. Subsequently, considering changes in the active layer depth computed by QUINCY, we calculated historical and future changes in active layer Ca and Si contents at selected sites. Element availability and associated effects on carbon cycle processes were simulated for three Siberian permafrost observatories, Chersky, Spasskaya Pad and Chokurdakh.

For a historical time period, testing the Ca/Si relationship at the Chersky site for the carbon cycle resulted in a slightly improved agreement between model results and eddy covariance flux data, mainly linked to an increase in organic matter stabilization induced by higher Ca content in the soil. To illustrate the potential future implications of Ca and Si on the permafrost carbon cycle, we then compared a historical (2000 – 2020) against a future (2060 – 2080) period, with the simulations for the latter based on RCP 4.5 emissions. The substantial increase in active layer depth (0.5 – 0.8m) between these periods led to various changes in Ca/Si availability across our three study sites, including neutral to positive trends for Si and both increases and decreases for Ca. Since Ca dominated the net effect on carbon cycling, accordingly we observed both increases and decreases in GPP and ecosystem respiration linked to the consideration of Ca/Si effects, with mean changes in component fluxes reaching up to ±24 g m-2 yr-1. This implies that considering stabilization factors induced by Ca/Si, and potentially other soil minerals, could be important for a process-based reproduction of present-day permafrost carbon cycles, and projections of future scenarios.

How to cite: Göckede, M., Lacroix, F., Schaller, J., Stimmler, P., and Zaehle, S.: Process-based simulation of nutrient (N, P, Si, Ca) effects on permafrost carbon cycling under present and future climate conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11216, https://doi.org/10.5194/egusphere-egu23-11216, 2023.

EGU23-11626 | ECS | Orals | BG1.8

Mapping Drained Lake Basins on a circumpolar scale 

Helena Bergstedt, Benjamin Jones, Annett Bartsch, Louise Farquharson, Juliane Wolter, Amy Breen, Mikhail Kanevsiy, Guido Grosse, Pascale Roy-Léveillée, and Clemens von Baeckmann

Lakes and drained lake basins (DLB) are ubiquitous landforms in permafrost lowland regions, covering 50% to 75% of permafrost lowlands in parts of Alaska, Siberia, and Canada. Depending on the time passed since the drainage event, surface characteristics within the DLB such as surface roughness, vegetation, moisture and abundance of ponds may vary. The mosaic of vegetative and geomorphic succession within DLBs and the distinct differences between DLBs and surrounding areas can be discriminated with remote sensing and used to derive a landscape-scale classification. Previously published local and regional studies have demonstrated the importance of DLBs regarding carbon storage, greenhouse gas and nutrient fluxes, hydrology, geomorphology, and habitat availability. To help quantify these processes on a circumpolar scale and improve the representation of Arctic landscapes in large scale models, a circumpolar data set of DLBs distribution and DLB properties is needed.  Due to the inherent temporal characteristics of DLBs, such a data set also has the potential for space-for-time applications regarding landscape models. A pan-Arctic scale effort to map and further the understanding of DLBs in permafrost-regions is the outcome of work conducted within the International Permafrost Association (IPA) Action Group on DLBs, a bottom-up effort led by the scientific community that includes developing a first pan-Arctic drained lake basin data product based on multispectral remote sensing data (Landsat-8). Comprehensive mapping of DLBs areas across the circumpolar permafrost landscape and including field data into this approach will allow for future utilization of these data in pan-Arctic models, aid upscaling efforts and greatly enhance our understanding of DLBs in the context of permafrost landscapes. This will improve quantitative studies on landscape diversity, wildlife habitat, permafrost, hydrology, geotechnical conditions, high-latitude carbon cycling, and landscape vulnerability to climate change.

How to cite: Bergstedt, H., Jones, B., Bartsch, A., Farquharson, L., Wolter, J., Breen, A., Kanevsiy, M., Grosse, G., Roy-Léveillée, P., and von Baeckmann, C.: Mapping Drained Lake Basins on a circumpolar scale, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11626, https://doi.org/10.5194/egusphere-egu23-11626, 2023.

EGU23-12327 | ECS | Orals | BG1.8

First measurement of methane emissions from Canadian glaciers in the Yukon 

Sarah Elise Sapper, Christian Juncher Jørgensen, Moritz Schroll, Frank Keppler, and Jesper Riis Christiansen

Land-terminating glaciers in Greenland and Iceland are sources of methane (CH4) to the atmosphere1,2,3. CH4 is produced through microbial methanogenesis underneath the ice, transported dissolved in subglacial meltwater to the margin where the gas is emitted to the atmosphere via degassing4. However, sparse empirical data exist about the spatial distribution of subglacial CH4 production and emission in other glaciated regions of the world, limiting our understanding of its regional and global importance in atmospheric carbon budgets and its possible role in the climate system.

In August 2022, we conducted fieldwork at three outlet glaciers - Dusty, Kluane and Donjek glaciers - of the St. Elias Icefields in Yukon, Canada, to investigate if these alpine glaciers are also sources of CH4 emissions to the atmosphere. The glaciers were chosen due to the absence of proglacial lakes and the presence of meltwater upwellings at the glacier termini, which were accessed via helicopter.

In-situ extracted dissolved CH4 and CO2 concentrations were measured in the field with a portable greenhouse gas analyzer. Additionally, extracted gas was collected in exetainers for concentration measurements via gas chromatography and in Tedlar gas bags for stable carbon and hydrogen isotope analyses of CH4 to decipher its origin. Further, water samples were collected for geochemical analyses. At Dusty glacier, we performed a high-intensity sampling campaign over 10 hours and continuous measurements of dissolved CH4 concentrations with a custom-made low-cost and low-power dissolved CH4 sensor5 to study changes in dissolved gas concentrations, stable isotopic signatures and water chemistry during the rising limb of the diurnal discharge curve.

In-situ measured CH4 and CO2 concentrations yielded significantly elevated CH4 and depleted CO2 levels in the meltwater of all three glaciers. Discrete gas samples confirmed dissolved CH4 concentrations 45x, 135x and 250x above the atmospheric equilibrium concentration (3.6 nmol L-1) in the meltwater of Dusty, Kluane and Donjek glaciers, respectively. First measurements of stable carbon and hydrogen isotope values of CH4 showed enrichment in 13C, while 2H was depleted compared to atmospheric CH4, at all sites, likely originating from a thermogenic source or caused by bacterial CH4 oxidation. Water analyses showed an alkaline environment enriched in carbonates and DOC, in contrast to more acidic waters from glaciers in Greenland and Iceland.

These first measurements demonstrate that the subglacial meltwaters from glaciers in the St. Elias Icefields are net sources of CH4 and net sinks of CO2 to the atmosphere. Our findings indicate that CH4 emissions from subglacial environments under alpine glaciers may be a more common phenomenon than previously thought, and a potential cause for remotely sensed CH4 concentrations anomalies over glaciated regions. However, more alpine glaciers and outlets from the Greenland Ice Sheet need to be studied to evaluate this link and provide the needed ground truthing for satellite sensors in high latitudes.

 

1. Christiansen & Jørgensen (2018) DOI 10.1038/s41598-018-35054-7

2. Lamarche-Gagnon et al. (2019) DOI 10.1038/s41586-018-0800-0

3. Burns et al. (2018) DOI 10.1038/s41598-018-35253-2

4. Christiansen et al. (2021) DOI 10.1029/2021JG006308

5. Sapper et al. (2022) DOI:10.5194/egusphere-egu22-9972

How to cite: Sapper, S. E., Juncher Jørgensen, C., Schroll, M., Keppler, F., and Riis Christiansen, J.: First measurement of methane emissions from Canadian glaciers in the Yukon, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12327, https://doi.org/10.5194/egusphere-egu23-12327, 2023.

EGU23-13301 | Orals | BG1.8 | Highlight

CoMet 2.0 Arctic: Carbon Dioxide and Methane Mission for HALO 

Andreas Fix, Heinrich Bovensmann, Christoph Gerbig, Sven Krautwurst, Michal Gałkowski, Quatrevalet Mathieu, Christian Fruck, Sebastian Wolff, Friedemann Reum, Paul Waldmann, Florian Ewald, Bernhard Mayer, Patrick Jöckel, Christoph Kiemle, Charles E. Miller, and and the CoMet 2.0 Arctic team

In order to reliably predict the climate of our planet, and to help inform political conventions on greenhouse gas emissions such as the Paris Agreement of 2015, adequate knowledge of both natural and anthropogenic sources of the greenhouse gases Carbon dioxide (CO2) and methane (CH4) and their feedbacks is needed. Despite the recognized importance of this issue, our current understanding about sources and sinks of CO2 and CH4 is still inadequate. This is particularly true for the Arctic, where large wetlands and permafrost areas constitute the most relevant but least quantified ecosystems for the global carbon budget.

The CoMet 2.0 Arctic mission wants to help remedy this deficiency with a multi-disciplinary approach providing relevant measurements from Arctic regions using a suite of sophisticated scientific instrumentation onboard the German research aircraft HALO (High Altitude and LOng Range Research Aircraft, https://halo-research.de) to support state-of-the-art Earth System Models. At the same time, CoMet intends to support and improve current and future satellite missions, which still struggle to make high-quality measurements given the low sun elevation, low albedo, and adverse cloud conditions in the Arctic.

CoMet 2.0 Arctic (https://comet2arctic.de/) has successfully been conducted within a six-week intensive operation period from August 10th to September 16th, 2022 targeting greenhouse gas emissions from boreal wetlands and permafrost areas in the Canadian Arctic, from wildfires, and from anthropogenic emission sources such oil, gas, and coal extraction sites and landfills.

For that mission, HALO was equipped with a suite of remote sensing and in-situ instruments for the measurement of greenhouse gases and meteorological parameters. The remote sensing package comprised the CH4 and CO2 lidar CHARM-F (operated by DLR), the imaging spectrometer MAMAP2D-Light (operated by University of Bremen) and the hyperspectral imager specMACS (operated by LMU Munich). The remote sensors were supported by several in-situ instruments (operated by MPI Jena and DLR) to measure the main greenhouse gases and related trace species as well as an air sampler that collects air samples at flight level for later analysis (e.g. w.r.t. isotopes) in the laboratory. Furthermore, instruments to provide detailed information about the standard meteorological parameters (pressure, wind, humidity) were operated and several small meteorological sondes were launched in order to link those in-flight data to profiles.

A total of 135 flight hours including a test flight to landfills in Spain and transfer flights from Europe have been performed. 16 scientific flights took place out of Edmonton, Alberta, to various regions all over Canada.

CoMet 2.0 Arctic has partly been coordinated with the Arctic-Boreal Vulnerability Experiment field program by NASA (ABoVE, https://above.nasa.gov/). Both missions, ABoVE and CoMet 2.0 Arctic, are linked through the transatlantic initiative AMPAC (Arctic Methane and Permafrost Challenge, https://www.ampac-net.info/) that has recently been inaugurated by the US and European Space Agencies, NASA and ESA.

Thus, a valuable data set was acquired to help better understand the methane and carbon dioxide cycles in the Arctic and emissions from natural and anthropogenic sources.

How to cite: Fix, A., Bovensmann, H., Gerbig, C., Krautwurst, S., Gałkowski, M., Mathieu, Q., Fruck, C., Wolff, S., Reum, F., Waldmann, P., Ewald, F., Mayer, B., Jöckel, P., Kiemle, C., Miller, C. E., and the CoMet 2.0 Arctic team, A.: CoMet 2.0 Arctic: Carbon Dioxide and Methane Mission for HALO, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13301, https://doi.org/10.5194/egusphere-egu23-13301, 2023.

Future warming of the Arctic not only threatens to destabilize the enormous pool of organic carbon accumulated in permafrost soils, but may also mobilize elements such as calcium (Ca) or silicon (Si). Little is known about the effects of Si and Ca on carbon cycle processes in soils from Siberia, the Canadian Shield or Alaska. We incubated five different soils for six months with different Ca and amorphous Si (ASi) concentrations. Our results show a strong decrease in soil CO2 production for all soils with increasing Ca concentrations. The ASi effect was not clear across the different soils used, with soil CO2 production increasing, decreasing or not being significantly affected depending on the soil type and if the soils were initially drained or waterlogged. Including Ca as a controlling factor for Arctic soil CO2 production rates may therefore reduce uncertainties in modelling future scenarios on how Arctic regions may respond to climate change. To project how biogeochemical cycling in Arctic ecosystems will be affected by climate change, there is a need for data on element availability. For this we analysed ASi, Si, Ca, iron (Fe), phosphorus (P), and aluminium (Al) availability from 574 soil samples from the circumpolar Arctic region. We show large differences in element availability among different lithologies and Arctic regions. We summarized these data in pan-Arctic element maps focussing on the top 100 cm of Arctic soil. Furthermore, we provide values for element availability for the organic and the mineral layer of the seasonally thawing active layer as well as for the uppermost permafrost layer. Our spatially explicit data on differences in the availability of elements between the different lithological classes and regions now and in the future will improve Arctic Earth system models for estimating current and future carbon and nutrient feedbacks under climate change.

How to cite: Stimmler, P. and Schaller, J.: Calcium and amorphous silica in Arctic soils: Estimating Pan-Arctic availabilities and importance for CO2 production, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13563, https://doi.org/10.5194/egusphere-egu23-13563, 2023.

EGU23-13894 | ECS | Orals | BG1.8

Natural methane emissions at high latitudes: A study through the MAGIC2021 measurements campaign 

Félix Langot, Cyril Crevoisier, Thomas Lauvaux, Axel Guedj, Jérôme Pernin, Antoine Berchet, Isabelle Pison, and Sophie Wittig

Methane is a potent greenhouse gas that plays a significant role in the global climate system. High latitude methane is a particularly sensitive subject due to the uncertainty in future gas release due to multiple factors such as the thawing of permafrost and the evolution of wetland cover. Thus, these regions have the potential to significantly contribute to global warming. In this study, we present the results of the MAGIC2021 campaign, which was conducted in Lapland around Kiruna, Sweden in August 2021. The campaign included measurements with atmospheric air sampler AirCores on board weather balloons, three research aircraft equipped with in-situ sensors, and ground-based measurements of gas total columns using EM27/SUNs. We focus here on the combined measurements of 0-30 km profiles by AirCore and by ATR42 research aircraft to investigate sources of methane in the region. To this end, we employed back-trajectory Lagrangian models and conducted an in-depth comparison between model (ERA5, CAMS) and campaign data in a multi-species approach combining CH4, CO2 and CO. Our findings provide insight into the sources and transport of methane at high latitudes. They show that in order to properly study local sources of methane, it is mandatory to account for transported methane originating from regions as far as Northern Canada. Our work also highlights the importance of conducting in situ measurement campaigns like MAGIC2021, which provide valuable data for improving our understanding of atmospheric processes at high latitudes and informing the development of more accurate models and validate satellite retrievals. Plans for next campaigns will also be detailed.

How to cite: Langot, F., Crevoisier, C., Lauvaux, T., Guedj, A., Pernin, J., Berchet, A., Pison, I., and Wittig, S.: Natural methane emissions at high latitudes: A study through the MAGIC2021 measurements campaign, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13894, https://doi.org/10.5194/egusphere-egu23-13894, 2023.

EGU23-14008 | Posters on site | BG1.8

Modeling influence of CH4 ebullition on carbonate system in the East Siberian Arctic Shelf 

Evgeniy Yakushev, Anfisa Berezina, Matvey Novikov, Richard. Bellerby, and Igor Semiletov

Progressive permafrost thawing leads to excessive transport of organic matter (OM) from the land and massive bubbling methane (CH4) release from degrading subsea permafrost in the Arctic shelf. The “extreme” aragonite under-saturation in the vast East Siberian Arctic Shelf (ESAS) reflects seawater acidity levels much higher than those projected in this region for the end of this century, as these are currently based only on atmospheric CO2.(Semiletov et al., 2016). The changes in the carbonate system can be explained by an excessive production of carbon dioxide connected due to mineralization of land origin OM or /and oxidation of methane in the areas of intensive seeping.

Here, we analyze consequences of CH4 oxidation on the carbonate system state in the methane seepage areas. We used biogeochemical model BROM coupled with a vertical 2 Dimensional Benthic-Pelagic Model 2DBP and bubble fate model (Yakushev et al., 2021). BROM is a detailed biogeochemical model for the water column, benthic boundary layer (BBL), and sediments. BROM considers interconnected transformations of species (N, P, Si, C, O, S, Mn, Fe) and resolves OM in nitrogen currency. BROM includes a module describing the carbonate equilibrium; this allows BROM to be used to calculate pH and carbonates saturation states, as well as processes of formation and dissolution of carbonates. The model's alkalinity variations take into account changes connected with redox reaction consuming or releasing proton. Methanogenesis and aerobic and anaerobic methane oxidation are also parameterized. The gas bubble fate module parameterizes bubbles rising and dissolution.  An application of the model allowed to estimate connection between an intensity of CH4 release in the area (Shakhova et al., 2015) and changes in the carbonate system and to evaluate a volume of water affected. This research was funded by the Research Council of Norway: 315317 BEST-Siberian.

References:

Semiletov et al. (2016) Acidification of East Siberian Arctic Shelf waters through addition of freshwater and terrestrial carbon. Nat. Geosci., 9 (2016), pp. 361-365, 10.1038/NEGO2695

Shakhova N et al . ( 2015) The East Siberian Arctic Shelf: towards further assessment of permafrost-related methane fluxes and role of sea ice. Phil. Trans. R. Soc. A373: 20140451.http://dx.doi.org/10.1098/rsta.2014.0451

Yakushev E., Blomberg A.E.A., Eek E., Protsenko E., Totland C., Staalstrøm A., Waaru I.-K. Modeling of biogeochemical consequences of a CO2 leak in the water column with bottom anoxia. International Journal of Greenhouse Gas Control. 2021. 111: 103464.

How to cite: Yakushev, E., Berezina, A., Novikov, M., Bellerby, R., and Semiletov, I.: Modeling influence of CH4 ebullition on carbonate system in the East Siberian Arctic Shelf, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14008, https://doi.org/10.5194/egusphere-egu23-14008, 2023.

EGU23-14205 | Posters on site | BG1.8 | Highlight

In situ measurements of greenhouse gas mole fractions over North American high-latitude regions during CoMet 2.0 Arctic mission 

Michal Galkowski, Christoph Gerbig, Uwe Schultz, and Andreas Fix

As a second most abundant anthropogenic greenhouse gas, methane has been an object of intense study over the past years. Despite a good overall knowledge of the sources contributing to the increase of its atmospheric abundance, the precise constrain of the global methane budget remains elusive, with large uncertainties still characterizing both anthropogenic and natural emissions, especially in the regions poorly constrained by observations, such as tropical wetlands or northern high-latitude regions.

CoMet 2.0 Arctic mission, executed in August and September 2022 aimed at characterizing the distribution of CH4 and CO2 over significant regional sources with the use of a German Research Aircraft HALO (High Altitude Long-range Observatory), as well as to validate remote sensing measurements from state-of-the-art instrumentation installed on-board against a set of independent in-situ observations. These sources included both anthropogenic (oil, gas and coal industries) as well as natural sources that represent large-scale methane-emission regions (including wetlands and major deltas in the region).

We will present results of in-situ observations performed across 15 research flights performed over a variety of environments. High-precision mole fractions of CO2, CH4 and CO were measured with the the JIG (Jena In-Situ Greenhouse gas sensor, based on Picarro 2401-m) instruments, while JAS (Jena Air Sampler) allowed collection of 155 spot samples to additionally characterize N2O, H2, SF6, O2/N2, Ar/N2 and stable isotopes (not presented).

Flight strategies were adopted in order to balance the needs of different types of instrumentation aboard HALO aircraft, while simultaneously sample the atmospheric constituents in the optimal manner. These strategies included a) high- to mid-altitude horizontal legs during transfers from Base of Operations (Edmonton, Alberta) towards the specific target areas, b) local vertical profiles, c) low-altitude sections with detailed scanning of the mole fractions of atmospheric constituents across the PBL and residual layers. With the appropriate selection of strategies for targeting particular emission sources, we were able to gather a rich observation suite that demonstrates importance of interplay between regional fluxes and atmospheric dynamics on spatio-temporal ranges larger than usually considered.

How to cite: Galkowski, M., Gerbig, C., Schultz, U., and Fix, A.: In situ measurements of greenhouse gas mole fractions over North American high-latitude regions during CoMet 2.0 Arctic mission, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14205, https://doi.org/10.5194/egusphere-egu23-14205, 2023.

EGU23-15346 | Orals | BG1.8

Airborne in-situ observations of natural methane emissions in Scandinavia during MAGIC 2021 

Klaus-Dirk Gottschaldt, Cyril Crevoisier, Alina Fiehn, Andreas Fix, Kerstin Hartung, Heidi Huntrieser, Patrick Jöckel, Bastian Kern, Julian Kostinek, Tiina Markkanen, Mariano Mertens, Callum Middleton, Magdalena Pühl, Mathieu Quatrevalet, Martin Wooster, and Anke Roiger

Wetlands in the high northern latitudes are a major, yet poorly known contributor to the global methane (CH4) budget. In wetlands, peat bogs and lakes, CH4 is produced by organic degradation processes. These natural emissions are affected by climate change though, e.g. by changing temperatures and permafrost thaw. A better understanding is essential also for discussing the human role in the budget of this important greenhouse gas and mitigation options.

However, the data coverage in the region is still thin: accessibility is limited, satellite sensors struggle with the high solar zenith angle, difficult surface and thermodynamic conditions, or clouds. Corresponding emission inventories and models differ significantly, in the distribution as well as in the amount of emissions. Based in Kiruna/Sweden, the French MAGIC initiative addressed these knowledge gaps by bringing together a multitude of instruments on three research aircraft (Safire ATR-42, BAS Twin Otter, DLR Cessna) and various other platforms for measurements in northern Scandinavia in August 2021.

Here we focus on airborne in-situ measurements with the DLR Cessna. The suite of instruments aboard the aircraft included a meteorological sensor package, a Picarro, and an Aerodyne QCLS, providing CH4,CO2, C2H6, 13C(CH4), temperature, H2O, 3d-wind, all along the flight track.

The Cessna conducted 12 scientific flights in the region, which mostly targeted and scouted hotspots of CH4 emissions indicated by wetland emission inventories. The flights were coordinated as often as possible with other airborne, ground-based and satellite platforms to allow for intercomparisons and for providing ground truth for remote sensing instruments. Estimating CH4 emission fluxes is another major objective, which is challenging because of spatial and temporal heterogeneity of these area sources. To this end we tried a combination of different methods and flight patterns. We provide an overview of the measurements, discuss the different flight strategies and show first results of the analyses that are ongoing in the frame of the ESA MAGIC4AMPAC project.

How to cite: Gottschaldt, K.-D., Crevoisier, C., Fiehn, A., Fix, A., Hartung, K., Huntrieser, H., Jöckel, P., Kern, B., Kostinek, J., Markkanen, T., Mertens, M., Middleton, C., Pühl, M., Quatrevalet, M., Wooster, M., and Roiger, A.: Airborne in-situ observations of natural methane emissions in Scandinavia during MAGIC 2021, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15346, https://doi.org/10.5194/egusphere-egu23-15346, 2023.

EGU23-17361 | Orals | BG1.8

MethaneCAMP project – first results 

Johanna Tamminen and the MethaneCAMP project team

The ESA funded two-year MethaneCAMP project addresses specifically satellite observations of methane (CH4) in the Arctic in support of the collaborative ESA-NASA Arctic Methane and Permafrost Challenge (AMPAC) initiative.  Up to now, satellite retrievals of methane have not been optimised for the high latitude conditions. Known challenges are caused by high solar zenith angles, low reflectivity over snow and ice, frequent cloudiness, varying polar vortex conditions and limited number of validation data sets. The goal of MethaneCAMP is to improve the observation capacity over polar regions by assessing and optimising methane retrievals at high northern latitudes. Furthermore, MethaneCAMP aims to demonstrate the potential of using satellite observations of methane together with modelling and surface observations in analysing spatial and temporal changes of the Arctic methane. Specifically, we will focus on Sentinel 5P/TROPMI, GOSAT, GOSAT-2 and IASI XCH4 observations and on few case studies of high spatial resolution instruments. In this presentation we review the preliminary results of MethaneCAMP project which are achieved in the first year and discuss how the outcomes can be utilised in the AMPAC working group activities.

How to cite: Tamminen, J. and the MethaneCAMP project team: MethaneCAMP project – first results, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17361, https://doi.org/10.5194/egusphere-egu23-17361, 2023.

In criminal cases of clandestine homicide graves, the criminal behavior and mental map of an offender may be influenced by several geographical, botanical, and geological features. Among these factors, diggability assumes for a concealer a predominating role in the concealment act because an easy and efficient digging of a hole requires that the ground is diggable. The diggability (the ease and efficiency with which soils and sediments may be dug and reinstated in a grave) may vary from very easy to difficult, and forensic geologists may qualitatively and relatively evaluate it by using a T-metal bar for offensive and defensive search purposes. Results of a diggability survey were processed in the GIS platform, reconstructing contour maps, Inverse Distance Weighting, Kriging, and Thin Plate Spline with Tension maps of a crime scene. The interpolation of the data by Thin Plate Spline with Tension rendered the best results. The diggability survey demonstrated that the pit fell in a suitable area for concealment, being one of the easiest diggable and thick sectors of the search area.

How to cite: Somma, R.: Diggability field survey for the assessment of the most suitable site for a clandestine homicide grave, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-20, https://doi.org/10.5194/egusphere-egu23-20, 2023.

EGU23-70 | Posters virtual | ITS4.2/BG1.12

Procedures for the documentation and collection of physical evidence from human and animal envenomization cases. 

Jason Byrd, Daniela Sapienza, Michael Schaer, Adam Stern, Roberta Somma, Lerah Sutton, and Domenico Trombetta

Legal cases involving human and animal envenomizations may be encountered by the medicolegal investigator.  Such cases are often difficult due to lack of physical evidence and analytical difficulty.  The development and use of an interdisciplinary approach and standardized protocol involving experts in environmental and life sciences (toxicology, legal medicine, entomology, veterinary forensic science, biology, geography, geology, and meteorology) may improve the documentation, collection, and presentation of physical evidence in court.  This information can be utilized to develop and optimize new protocols for toxicological screenings for application in human and animal cases.  In such cases, the scientific background of coroners and police experts may not be sufficient to correctively delineate the environmental features of the territory that may be typical of certain species of venomous fauna present in the scene of the events. Therefore, protocols providing complete information concerning the environment of the scene and detail of the events together with exam protocols, sample collection, tissue preservation, and testing/analysis are needed. This holistic approach could enhance the ability to detect toxins involved in envenomizations to better manage forensic science and legal cases. 

 

How to cite: Byrd, J., Sapienza, D., Schaer, M., Stern, A., Somma, R., Sutton, L., and Trombetta, D.: Procedures for the documentation and collection of physical evidence from human and animal envenomization cases., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-70, https://doi.org/10.5194/egusphere-egu23-70, 2023.

EGU23-145 | ECS | Posters virtual | ITS4.2/BG1.12

The unique contextual situation of the Ca’ Granda burial ground: from taphonomic observations towards a new type of anthropogenic soil 

Giulia Tagliabue, Anna Masseroli, Mirko Mattia, Carlotta Sala, Elena Belgiovine, Daniele Capuzzo, Gaia Giordano, Paolo Maria Galimberti, Fabrizio Slavazzi, Cristina Cattaneo, and Luca Trombino

Soil is a dynamic matrix that can rapidly respond to disturbance events, such as the death and the subsequent deposition of an organism. Concurrently, it can be considered an archive of evidence due to its ability to record the signals of disturbance events. Such a condition turns the biogeochemical analysis of geopedological samples into a valuable tool for the study of decomposition processes, especially when they are flanked with the examination of the remains. The aim of the present research is to present the unique contextual situation of the Sepolcreto (i.e., burial ground) under the crypt of the ancient Ospedale Maggiore of Milan Ca’ Granda (Italy). The sepulchre hosted an estimated amount of 150000 buried individuals, 10000 of which are still buried in one of the underground chambers, named “chamber O”, and whose remains underwent various type of post-mortem transformative processes, both disruptive and preservative. In this study microscopic and ultramicroscopic analysis have been carried out in order to detect any evidence of material exchange between the bone tissue, from three skeletal remains collected from the “chamber O” of the Sepolcreto, and the surrounding pedosedimentary matrix. The specimens were analysed by the mean of a polarizing microscope and a SEM-EDS, which pointed out the presence of a mutual exchange of material between the two substrates, underlying the intensity of the interaction between organisms (even after their death) and the environment. Finally, this burial context permitted to observe an inedited type of soil, mainly composed of organic matter transformed by thanatological processes, bone tissue fragments and some other evidence of anthropic origin and/or activity. Therefore, it has been considered a new type of anthropogenic soil named “Thanatogenic soil”.

How to cite: Tagliabue, G., Masseroli, A., Mattia, M., Sala, C., Belgiovine, E., Capuzzo, D., Giordano, G., Galimberti, P. M., Slavazzi, F., Cattaneo, C., and Trombino, L.: The unique contextual situation of the Ca’ Granda burial ground: from taphonomic observations towards a new type of anthropogenic soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-145, https://doi.org/10.5194/egusphere-egu23-145, 2023.

Contrarily to land plants, which display complex anatomical features useful in diagnostics, algae are problematic to identify at the species level. Taxonomic identifications classically are focused on morphological observations at the light microscopy, but current research showed extensive phenotypic plasticity and cryptic diversity resulting in different phylogenetic assemblages. Modern taxonomic approaches also include ultrastructural (SEM and/or TEM), phylogenetic and phylogenomics information, all methodologies that may be expensive and need the involvement of skilled experts. In criminal investigations, such methodologies may not be always applicable by the judicial system because of the costs, and morphological identification of algae at the light microscope is usually the standard method. Consequently, scientific data coming from algae are often neglected in forensic investigations, with the notable exceptions of the diatoms in drowning victims.

This research deals with a traditional morphological investigation on the detection and identification of soil microalgae in a case of disappearance. The method was useful in forensic investigations to associate control samples from the scene of the events to detected traces of unknown origin found on the victims.

Morphological characteristics (shape, size, color, taking into consideration the different state of conservation of the algae) and cellular characteristics (wall, unicellular, colonial, multicellular organization) were observed at the light microscopy.  Where species identification was not achievable with certainty, the smallest identifiable taxonomic level was recorded. A comparison of identified morphotypes as well as of the peculiar associations of taxonomic entities was made between sample of unknown origin to those of known origin and was used to evaluate similarity degree.

Observations of microalgae, in association with other geological (shape, size, color, composition of mineral grains) and botanical (shape, size, color of leaves and seeds) analyses, allowed investigators to: i) associate the walking of a person under investigation in specific sites of the scene of the events; ii) exclude that the bodies of two victims were submerged under water; iii) exclude the contact of any surface of the persons’ belongings, other than the soles of their shoes, with water basins of any kind.

The present investigation proved how a traditional light microscopic approach could be decisive to associate field samples to detected traces, basing on the identification of associations of morpho-types of microalgae.

How to cite: Morabito, M. and Somma, R.: May light microscopy observations of algae play a significative role in forensic investigations of soils?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1336, https://doi.org/10.5194/egusphere-egu23-1336, 2023.

EGU23-2692 | Orals | ITS4.2/BG1.12 | Highlight

Pesticide use under the influence of socio-economic and climate change: Pest-Agri-SSPs 

Stefan Dekker, Poornima Nagesh, Oreane Edelenbosch, Hugo de Boer, Hermine Mitter, and Detlef P. van Vuuren

Pesticide use is a crucial human-driven change in the Anthropocene that negatively impacts the environment and ecosystems. While pesticides are essential to agriculture to sustain crop production and ensure global food security, they also lead to significant environmental impacts. The export of pesticides after application from the agricultural fields threatens the soil, groundwater and surface water quality in many world regions. Pesticide use is constantly increasing globally, driven mainly by agricultural intensification, despite stricter regulations and higher pesticide effectiveness. To enhance the understanding of future pesticide use and emissions and make informed farm-to-policy decisions, we developed Pesticide Agricultural Shared Socio-Economic Pathways (Pest-Agri-SSPs) in six steps. The Pest-Agri-SSPs are based on an extensive literature review and expert knowledge, considering significant climate and socio-economic drivers from farm to continental scale in combination with multiple actors impacting them. In the literature, pesticide use is associated with farmer behaviour and agricultural practices, pest damage, technique and efficiency of pesticide application, agricultural policy and demand for agricultural products. Here, we developed Pest-Agri-SSPs upon this understanding of pesticide use drivers and relating them to plausible sectoral developments, as described by the Shared Socio-economic Pathways for European agriculture and food systems (Eur-Agri-SSPs).

The Pest-Agri-SSPs present European pesticide use in five scenarios with low to high challenges to climate change adaptation and mitigation up to 2050. The most sustainable scenario (Pest-Agri-SSP1) shows a decrease in pesticide use owing to sustainable agricultural practices, technological advances and a pro-environmental orientation of agricultural policies. On the contrary, the Pest-Agri-SSP3 and Pest-Agri-SSP4 show an increase in pesticide use resulting from high challenges from pest pressure, resource depletion and relaxed agricultural policies. Pest-Agri-SSP2 presents a stabilised pesticide use resulting from strict policies and slow transitions by farmers to sustainable agricultural practices. Pest-Agri-SSP5 shows a decrease in pesticide use for most drivers, influenced mainly by rapid technological development and the application of sustainable agricultural practices. However, Pest-Agri-SSP5 also shows a relatively low rise in pesticide use driven by agricultural demand, production, and climate change. Our results highlight the need for a holistic approach to tackle pesticide use and emissions, considering the identified drivers and future developments. The storylines and qualitative assessment provide a platform to make quantitative assumptions for numerical modelling and evaluating policy targets.

Keywords: Farm characteristics, pest damage, technology, policy, socioeconomic, agriculture and food systems

Adapted version of this work has been submitted to Journal of Environmental Management: Nagesh P, Edelenbosch OY , Dekker SC, de Boer HJ, Mitter H, van Vuuren DP. Pesticide use under the influence of socio-economic and climate change: Pest-Agri-SSPs

 

 

How to cite: Dekker, S., Nagesh, P., Edelenbosch, O., de Boer, H., Mitter, H., and van Vuuren, D. P.: Pesticide use under the influence of socio-economic and climate change: Pest-Agri-SSPs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2692, https://doi.org/10.5194/egusphere-egu23-2692, 2023.

EGU23-3869 | Posters virtual | ITS4.2/BG1.12

Overview in forensic purpose and application of plant DNA 

Daniela Sapienza, Gennaro Baldino, Irene Lo Piccolo, Roberta Somma, Elvira Ventura Spagnolo, Cristina Mondello, Patrizia Gualniera, and Alessio Asmundo

The multidisciplinary approach in forensic science led to the development of geology and botany as predictive forensic applications (forensic geology – forensic botany) aimed at analyzing and studying the crime scene for the "solving" of the criminal hypothesis. Over the past fifteen years, the study of plant DNA has been used in forensics science to discriminate the place of origin of plant material found at a crime scene, to identify poisonous vegetable species, as a forensic marker in all cases where determining geographic origin is essential to investigative leads, missing person cases, and intelligence application (Bell et al., 2015), in the identification of Cannabis as support of law authorities in fighting drug abuse and global trafficking. These specific topics to date made it possible to: distinguish a primary crime scene from a secondary one, link a suspect to the crime scene, and determine the date of death. Findings of plant material can be examined through chemical analysis, morphological analysis, DNA analysis, PCR and electrophoresis. Comparative studies may be carried out among the plant remains collected from the victim and suspect and plant sampled on the event scene in order to trace the place where the plant transfer occurred. The analysis of the international literature presented through this review shows the importance of further developments in plant DNA analysis, growing and expanding a global database containing the plant DNA barcode, and implementing specific guidelines for the collection and sampling procedures of forensic samples.

How to cite: Sapienza, D., Baldino, G., Lo Piccolo, I., Somma, R., Ventura Spagnolo, E., Mondello, C., Gualniera, P., and Asmundo, A.: Overview in forensic purpose and application of plant DNA, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3869, https://doi.org/10.5194/egusphere-egu23-3869, 2023.

One pillar of the protection of groundwater established by the EU legislation is the “polluter pays principle”. Following this principle, the costs for the remediation of contaminated sites must be in charge of the responsible of the environmental crime. Compound Specific Isotope Analysis (CSIA), also known as “isotopic fingerprinting”, is a robust tool to apportion the source of groundwater contamination and eventually the polluter. The isotopic composition of the contaminant molecule may reflect the production process of a compound or the origin of the raw materials used in the production. Here we present the effective and decisive application of isotopic fingerprinting of carbon stable isotopes in the molecule of chlorinated hydrocarbons (chlorinated ethenes PCE-Perchloroethylene and TCE-Trichloroethylene) for the source apportionment in two contaminated sites in Italy, namely Ferrara (Emilia-Romagna region, Northern Italy) and Bussi sul Tirino (Abruzzo region, Central Italy). In both cases, industrial wastes from a production of chloromethanes, using methane and chlorine, were disposed illegally in unlined dumps resulting in a severe contamination of groundwater. The companies responsible for the contamination are different in the two sites but the production process is the same, resulting in a similar isotopic signature of the wastes. In both cases, the isotopic fingerprinting was critical to identify the chlorometane production as the source of contamination among other possible sources, despite two different hydrogeological settings (a large alluvial plain in the Ferrara site and a narrow valley with macroclastic alluvial deposits and travertines in the Bussi site). In both cases, PCE and TCE showed strongly depleted values of δ13C (isotopic ratio of the fraction of 13C respect to 12C isotopes of carbon) ranging between  -87 and -65‰ for PCE and between -79 and -64‰ for TCE. The very depleted isotopic values are related to the use of methane in the production process instead of coal, this last one being commonly adopted in the synthesis of PCE and TCE for commercial use (e.g. for laundry of textiles or metal degreasing). The groundwater contamination in the two sites had serious implications in terms of sanitary risk due to vapour intrusion into residential buildings (Ferrara site) or water ingestion by local citizens (Bussi site) from a public water supply well field site serving about 300.000 inhabitants and affected for more than 20 years by the contamination (from the opening in 1984 to the decomissioning in 2007). In both cases, complex legal issues arose either below penal or civil jurisdiction and the isotopic fingerprinting was used as the most relevant proof in order to identify the polluters.

How to cite: Gargini, A. and Filippini, M.: Isotopic fingerprinting as an effective tool for polluter apportionment in environmental crimes involving groundwater, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4120, https://doi.org/10.5194/egusphere-egu23-4120, 2023.

EGU23-4457 | ECS | Posters virtual | ITS4.2/BG1.12

No chance for doubts: a multidisciplinary approach for solving a criminal case. 

Gennaro Baldino, Elvira Ventura Spagnolo, Stefano Vanin, Roberta Somma, Filippo Cucinotta, Cristina Mondello, Patrizia Gualniera, Michele Gaeta, Alessio Asmundo, and Daniela Sapienza

In a forensic context, the criminal case evaluation is often challenging, and the only autopsy may not be exhaustive to determine the cause and the time of death, mainly when the corpse is dismembered, charred, or putrefied. Moreover, the conditions of an altered corpse and the recovered places of the cadaver (countryside, forests, rivers, beaches, etc.), outdoors, or in burnt buildings and ruins, can raise challenges not only in terms of victim identification but also in terms of acquisition of additional information aimed at elucidating the dynamics of death, like the detection of the corpse transfer after the death, especially in cases of suspected homicides. In such complex cases, it is, therefore, of paramount importance to provide a multidisciplinary approach involving the collaboration of ultra-specialized forensic experts. In this context, experts in criminalistic disciplines, such as forensic geology, botany, and entomology, may provide their contribution, as well as the engineers applying to medicine new technologies for the 2D and 3D reconstructions of crime scenes and evidence. We consider helpful to report a court case that came to our attention, involving forensic pathology experts together with forensic biologists, geologists, botanists, naturalists, entomologists, veterinarians, physicists, computer scientists, and engineers whose collaboration based on a multidisciplinary approach contributed to the management and the solving of a suspect crime.

How to cite: Baldino, G., Ventura Spagnolo, E., Vanin, S., Somma, R., Cucinotta, F., Mondello, C., Gualniera, P., Gaeta, M., Asmundo, A., and Sapienza, D.: No chance for doubts: a multidisciplinary approach for solving a criminal case., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4457, https://doi.org/10.5194/egusphere-egu23-4457, 2023.

EGU23-5269 | ECS | Orals | ITS4.2/BG1.12 | Highlight

Environmental issues of self-heating coal waste dumps in Poland 

Ádám Nádudvari, Mariola Jabłońska, and Monika Fabiańska

During coal mining, an enormous amount of economically not used humic or sapropelic coals, coal shales are deposited as wastes nearby the coal mines in urbanised areas, e.g. Upper Silesia, Katowice – Rybnik Industrial Region, in Upper Silesian Coal Basin, Poland. These wastes start to oxidise or lose out weathering immediately; in the worst cases, they will undergo self-heating. During exothermic reactions, the heavy metals contained in these rocks, especially sulfur compounds of  Pb, Cd, Cr, Cu, Zn, Ni, Hg, As are mobilised to the environment due to their high volatility at elevated temperatures and due to low pH levels (2 – 4) occurring on the dumps (Nádudvari et al., 2021, 2022). Amongst them, the Hg mobilisation and enrichment make such coal waste dumps more dangerous. Nádudvari et al. (2021, 2022) reported >1000 mg/kg enrichment of Hg in crusts of expelled bitumen and in gases from thermally affected wastes Hg concentration reached ~100 times higher than in polluted urban air from Upper Silesia. Additionally, the MeHg formation - Methylmercury (10 – 30 μg/kg) was also significant and probably formed via chemical reactions. Furthermore, other toxic gases emitted from the vents like benzene, formaldehyde, NH3, HCl, H2S, CO, Cl2, NH3, SO2, and NO were detected, and many of their average annual concentrations exceeded numerous times the permissible Polish norms limits (Nádudvari et al., 2022). The formation of PAHs – Polycyclic Aromatic Hydrocarbons is also very common due to the burning processes, therefore, the lifetime cancer risks due to PAHs and heavy metals accumulations in the dumps are significant. Thus access to these dumps should be prohibited (Nádudvari et al., 2021). Abundant phenols are typical products of self-heating dumps, and their occurrence shows the coking conditions inside the dumps (Nádudvari et al., 2020). The potential ecological and human health risks of these dumps are moderate to very high due to the significant influence of the high Hg concentrations (Nádudvari et al., 2022).

How to cite: Nádudvari, Á., Jabłońska, M., and Fabiańska, M.: Environmental issues of self-heating coal waste dumps in Poland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5269, https://doi.org/10.5194/egusphere-egu23-5269, 2023.

Land reclamation is a significant environmental and economic issue. Nowadays, there is a need to restore industrial areas to a state as close to nature as possible. Therefore, it is essential to monitor the condition of soils in a quick and non-invasive way. In southern Poland, the mining industry led to the creation of diverse waste dumps like post-mining waste, tailings from flotation, or Zn-Pb wash waste dumps. The research area covers the industrial waste dumps in Olkusz, Bytom and Piekary Śląskie. For the study, soil samples were taken from 1 m soil pits to determine the migration of pollutants into the soil profile. Additionally, waste dumps contacting the soils were sampled (from 0.5 m deep pits). The total organic carbon and sulphur were determined using Eltra Elemental Analyser CS530, while the composition of the total extracts was analyzed using Agilent gas chromatograph 7890A, with a DB-5 column coupled with a mass spectrometer 5975 C XL MDS. The total concentration of trace elements was determined using atomic absorption spectrometry in an acetylene-air flame (Analyst 400, Perkin Elmer). The ERT measurements were performed using LUND electrical imaging system with SAS 4000 Terrameter produced by ABEM Malå (Guideline Geo).

The samples contain av. 3.7 wt. % TOC and 0.4 wt. % TS. In GC-MS chromatograms, the Bytom and Piekary Śląskie samples show a higher PAHs abundance than the Olkusz samples. In soil profiles near waste dumps, a higher abundance of PAHs was found not only in the surface layer but also in samples to 0.75 m depth. In soil profiles away from the landfill, a higher abundance of PAHs was found only to 0.5 m depth. The PAHs abundance was decreased below 0.5 m depth, and even some of the PAHs weren't found. The high PAHs abundance even at a depth of up to 1m was observed in soil profiles under a waste layer. In samples, the concentrations of trace elements are higher than the limit values (Cd 1.1 to 135.7, Pb 17 to 12407 and Zn 19 to 28903 mg/kg). Soil contamination and its spatial diversity with trace elements in the mining area can be successfully located and studied using ERT measurements. The impact of soil pollution was observed on the geoelectric cross-sections in the form of reduced electrical resistivity associated with an elevated trace element content compared to the unpolluted area. The differentiation of the electrical resistivity was related in particular to the sites of surface runoff from the waste dump. The sediment washed out from the waste dump changed the physical characteristics of the soil and lowered the electrical resistivity of the native geology. The results suggest that the trace elements and toxic organic compounds in wastes are mobilised by surface runoff and the infiltration of rainwater into the ground.

Acknowledgements

The financial support of the National Science Centre, grant No 2017/27/B/ST10/00680 is gratefully acknowledged.

Presentation preference: poster on-site in Vienna

 

 

How to cite: Szram, E., Kondracka, M., Fabiańska, M., and Marynowski, L.: Soil degradation caused by post-mining and post-metallurgical waste - detection using gas chromatography–mass spectrometry (GC-MS) and electrical resistivity tomography (ERT), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5477, https://doi.org/10.5194/egusphere-egu23-5477, 2023.

EGU23-5500 | Posters virtual | ITS4.2/BG1.12

Find the culprit 

Francesco Crea, Chiara Alessandrello, Francesco Parello, Roberta Somma, and Sebastiano Ettore Spoto

In Forensic Geology, Environmental Forensics is devoted to ascertaining contaminants in the soil/subsoil, surface waters, and groundwaters. In such cases, forensic geologists usually accomplish activities concerning geological, hydrogeological, geochemical, and geophysical research to individuate the source of the contaminant substance and discover if this latter depends on anthropogenic or natural origins.

Preliminary chemical data on groundwaters from some areas of the Peloritani Mountains showed anomalous high contents of fluoride F-, a halogen element in the atmosphere, sea, fresh waters, and minerals. Natural sources of fluoride in the groundwaters are volcanic gas, the sea, and minerals. Fluoride is an essential component in around 300 minerals, among which the most diffused are fluorite and fluorapatite. A significant chemical feature of the ions of fluoride is that they have the same charge as the hydroxyl group OH- and present an ionic radius very similar to OH-. These chemical characteristics make it possible that F- may readily substitute the hydroxyl group in minerals such as micas, X2Y4-6Z8O20(OH,F)4.

Most of the collected groundwaters in the present research were hosted in aquifers formed by Variscan high-grade metamorphic rocks provided with fracture permeability and in aquifers made up of Tertiary to Quaternary siliciclastic deposits with porosity permeability. These aquifers have a silicate composition and are rich in biotite. Among micas, biotite is the most diffused mafic mineral in the high-medium grade metamorphic rocks (augen gneiss, gneiss, mica schists) of the Peloritani Mountains. This mineral is also widespread in weathered monomineralic lithoclasts of siliciclastic deposits (Miocene, middle to upper Pleistocene, Holocene to Actual clastic deposits) deriving from dismantling the chain's metamorphic rocks.

Previous studies on biotite from acid plutonic rocks of India demonstrated that fluoride contents might reach a concentration up to 7 wt%. Biotite mica may be likely responsible for the natural fluoride contamination of some of the studied groundwaters, in some cases also commercially exploited in the past.

WHO suggests that the F- concentration in the drinking waters must range between 700 and 1500 µg/l depending on the different climatic zones. Concentrations over 1500 µg/l in Italian drinking waters are prohibited and dangerous for public health.

The present research carried out in the Peloritani Mountains is devoted to: i) defining the actual geographical extent of the identified F- anomaly; ii) studying the water/rock interactions to ascertain if the leaching of F- from biotite mica, present in the high-grade metamorphic rocks and siliciclastic deposits, may be the natural phenomenon responsible for the ascertained fluoride contamination; iii) search for possible other causes of F- contamination as the salt wedge intrusion in the groundwaters of the coastal areas.

How to cite: Crea, F., Alessandrello, C., Parello, F., Somma, R., and Spoto, S. E.: Find the culprit, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5500, https://doi.org/10.5194/egusphere-egu23-5500, 2023.

EGU23-5737 | Orals | ITS4.2/BG1.12

Self-heating-generated compounds release to water phase simulated by hydrous pyrolysis 

Monika Fabiańska, Ewa Szram, Dariusz Więcław, Magdalena Misz-Kennan, and Justyna Ciesielczuk

            Spontaneous heating of coal waste rocks stored within the dumps is the worldwide phenomenon. It occurs in oxygen-deficient conditions that can be well simulated by hydrous pyrolysis. The process leads to production of new, relatively well water soluble compounds. They should be considered a hazard to the aquatic systems, both to the surface and groundwater since many older coal waste dumps are not isolated from below. However, the amounts of water soluble compounds produced and their fingerprint are not well recognized. In this project we aimed to identify types of compounds produced using hydrous pyrolysis as laboratory simulation of self-heating carried out in controlled conditions. This will allow for identification of distribution patterns of self-heating-produced compounds also in natural waters.

            Four mudstones from two coal mines, the Janina (subbituminous) and Marcel (bituminous) (Upper Silesia Coal Basin, Poland) were selected for hydrous pyrolysis. The experiments were conducted in 1-liter reactors (Parr Co.) in temperatures 250, 360, and 400oC during 72 h. the procedure details are presented by Lewan et al. (2008). Amount of water added ranged from 200-380 mL. Dissolved organic compounds were isolated using solid phase extraction on C18 PolarPlus columns (BAKERBOND, 3g). Compounds were eluted with dichloromethane (HPLC grade). The compositions of SPE extracts was investigated with an Agilent 6890 gas chromatograph coupled with an Agilent Technology 5973 mass spectrometer.

            Hydrous pyrolysis released compounds such as phenols, carboxylic acids, aldehydes, and ketones, including numerous aromatic ketones and quinones, and S-heterocyclic compounds such as dibenzothiophenes. Phenolic derivatives, dominating in pyrolytic water phase (up to 60% of the total extract composition), comprised compounds from phenol (C0) to C4 phenols. The minimal temperature of phenol release, caused by the macromolecule cracking, was 360oC. Water phase from 250oC pyrolysis contained phenols in minor amounts only, and vitrinite, the main source of them, was not changed. The general composition of organic phase at this temperature corresponds to water leachates of Upper Silesia coal.

            Thus the major hazard to the aquatic environment is sites in coal waste dumps with self-heating temperature exceeding 250oC and compounds indicating this pollution origin are phenols with cresols and xylenols domination in the distribution.

 

Acknowledgements

The financial support of the National Science Centre, grant No 2017/27/B/ST10/00680 is gratefully acknowledged.

Lewan, M.D., Kotarba, M.J., Więcław, D., Piestrzyński, A., 2008. Evaluating transition-metal catalysis in gas generation from the Permian Kupferschiefer by hydrous pyrolysis. Geochim. Cosmochim. Acta 72, 4069-4093.

How to cite: Fabiańska, M., Szram, E., Więcław, D., Misz-Kennan, M., and Ciesielczuk, J.: Self-heating-generated compounds release to water phase simulated by hydrous pyrolysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5737, https://doi.org/10.5194/egusphere-egu23-5737, 2023.

In the 1978, Gianni Lombardi and Valerio Giacomini, two Italian experts in forensic geology and botany, respectively, were involved by the judicial authority for analysing the sands and plant remains found in the clothing and moccasins of the honorable Aldo Moro, kidnapped and killed by terrorists. Experts had to determine the site where this material transfer occurred.

As demonstrated by the analyses carried out by these experts, plant taxonomists can give useful information in forensic analyses especially for events occurring outdoor. Small plant traces spread in quantity, like pollens, spores, thorns, seeds and small fruits, may easily transfer to the clothing and footwear of people or to the same human body, moving outdoor in the countryside.

In 2020, 42 years later, the authors of this research were involved by the judicial systems to reconstruct the events related to the disappearance of two persons, in the Sicilian countryside, found cadavers a few days after in a site near the last sighting of them.

The research focused on the morphological description of thorns, other pointed structures, and seeds produced by plants thriving in the scene of events. For simplicity, it was chosen to use the generic term "thorns" to indicate pointed plant structures, although aware that the term "prickle" should have been used for epidermal structures, “thorns” strictly for stem-derived structures, and "spines" for other structures derived from leaves, petioles or stipules.

A photographic atlas of thorns and seeds was produced with the species found in the scene of the events. A comprehensive description of plants as they appeared in situ as well as of their thorny appendices was made, and explanatory pictures were captured, both in situ and under the stereoscopic microscope in the laboratory. The extensive biometric analysis made on thorns and seeds of all collected species in the scene of events was recorded.

Soil traces and microtraces of forensic samples of unknown origin (from the victims’ bodies and their belongings) were investigated for the presence of thorns or thorn fragments and seeds, which were then compared with those recorded in the atlas.

The organic component (vegetal elements) of the forensic geological traces from victims and their belongings was predominant in quantity over the inorganic one.

Comparative observations allowed to identify hundreds of thorns and thorn fragments and several hundreds of seeds found on the clothes and footwear of both victims, as plants thriving in the area under investigations. Basing on the punctual distribution of individual plants, the analysis of thorn traces and seeds was useful, together with geological analyses on sands and clay minerals, in reconstructing the path of the victims in the hours immediately preceding their death and, therefore, provided valuable information to the investigating authorities.

How to cite: Mondello, F., Morabito, M., and Somma, R.: Holistic approach in the forensic analysis of geological trace evidence: as Forensic Botanists and Geologists may help judicial investigations , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6304, https://doi.org/10.5194/egusphere-egu23-6304, 2023.

EGU23-6763 | Orals | ITS4.2/BG1.12

Contaminants in continental shelf sediments, a way to reconstruct a source to sink pathway (Naples Bay, Italy) 

francesco paolo buonocunto, alfonsa milia, matilda mali, santina giandomenico, antonella di leo, lucia spada, luciana ferraro, and laura giordano

In areas characterized by geologic variability and high demographic pressure, seafloor sediment characteristics and the study of contaminants are important to reconstruct the origin and pathway of both contaminants and the sediments from source to sink.

The area off-shore the alluvial Sarno plain (Naples Bay, Eastern Tyrrhenian Sea) is bounded by the Vesuvius volcano in the northern part and by the carbonates relief of the Sorrento Peninsula in the southern part, and it is affected by metals contamination due the outflow of industrial vast.

A Geochemical and physical parameters of the sediments were analysed along a transect moving from the coast until the 100 m of water depth with the aim to explore how the onshore documented contamination affect the offshore counterpart. Surface sediment samples collected from the offshore Sarno plain, were analysed for grain size, nutrients (TOC, TN, TP) and heavy metals (Hg, Cd, As, Cr, Ni, Cu, Zn, and Pb) to evaluate the contamination status, and processed using multivariate statistical analysis. A sediment survey along the transect has been used to evaluate: 1) the relative influences of parent lithology and anthropogenic effects offshore the Sarno river; and 2) the extension of the influence of the river in the submarine area.

Four clusters are identified through PCA analysis: 1) the first resulted associated to the presence of As and Fe, low TOC content and prevalence of sandy fraction reflecting a geogenic contribution from Vesuvius Plan; 2) the second mainly include Cr, Cu, Zn, Pb and partially Cd and Hg, high TOC content and finest granulometry, reflecting the influence of the Sarno River discharges in the marine area; 3) the third include a variability in the Mn, Fe and TOC content. This area might reflect the Sorrento-Peninsula influence; 4) the forth include samples of the distal area in which a low contamination rate is displayed and irregular Hg and Cd pattern are verified, probably due to diffuse contamination origin and other coupling factors

Results indicate that 1) the area offshore Vesuvius displays physical and geochemical association mainly related to the natural origin of volcanoclastic sediments; 2) in the central area, the association of contaminants suggests their anthropogenic origin from the Sarno Plain, whereas the distal area, characterized by low rate of contamination, are mainly influenced by sediment from Sorrento Peninsula. Finally based on the contaminant and nutrient distribution it is possible to individuate the distribution of terrigenous sediments and organic matter of the Sarno delta deposits. The results show that the river should account as one of the main contribution sources of anthropogenic contaminants.  Some metals contamination anthropogenic in origin and TOC in general decreased gradually with distance from the coast and in particular is limited to the area of deposition of the river discharge.

Individuation of several marine sector with different geochemical associations permitted the reconstruction of source to sink contaminants pathway on the continental shelf.

How to cite: buonocunto, F. P., milia, A., mali, M., giandomenico, S., di leo, A., spada, L., ferraro, L., and giordano, L.: Contaminants in continental shelf sediments, a way to reconstruct a source to sink pathway (Naples Bay, Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6763, https://doi.org/10.5194/egusphere-egu23-6763, 2023.

EGU23-8174 | ECS | Orals | ITS4.2/BG1.12 | Highlight

Searching for the bomb spike in Danube river sediments: Extracting the anthropogenic impact of Vienna 

Diana Hatzenbühler, Michael Weißl, Christian Baumgartner, and Michael Wagreich

The Anthropocene, the strongly debated potential new unit of the Geological Time Scale, describes the intensified anthropogenic influence on the environment and geological processes, and its traces in geological archives. Regional studies characterizing the growth of human impact, the Anthropocene transformation, are scarce, especially for urban or per-urban environments.

In this project, we investigate the anthropogenic impact of the metropolis Vienna on its peri-urban environment and the proposed beginning of the Anthropocene epoch in the 1950s CE by applying sedimentological and geochemical methods. In previous studies (Wagreich et al. 2022), the authors were able to successfully detect the human influence in urban sedimentary archives of Vienna (anthropogenic coarse sediments) using artificial isotopes and anthropogenic trace metals. For our project, we extend the study area from Vienna to the city of Hainburg to investigate Vienna’s anthropogenic impact in both anthropogenic and natural sediments downstream the Danube river. In this area, direct human intervention in the environment, such as ground excavations, backfill and damming, is highly variable, from locally strong (e.g., hydro-power dams, airport constructions), to not existing (National Park Donau-Auen), thus offering a suitable location to trace and quantify the extent of anthropogenic impact.

Within petrographic facies, sedimentological and geochemical markers are applied to characterize the anthropogenic strata in this area: The archive of fine-grained natural Danube deposits, i.e. erosional profiles and sediment cores, is analysed for trace metals, artificial radiogenic isotopes, and microplastics with the aim (i) to disentangle the anthropogenic fingerprint of Vienna from the sediment, (ii) to identify and evaluate the proposed Anthropocene geological boundary around 1950 CE, and (iii) to evaluate a potential correlative stratigraphic reference section section/ point for the Anthropocene downstream of Vienna. Finally, the Carnuntum-Vienna Anthropocene field lab offers the opportunity to integrate environmental systems modelling with an Anthropocene equation approach for the temporal and spatial growth of the anthropogenic layers (iv).           

How to cite: Hatzenbühler, D., Weißl, M., Baumgartner, C., and Wagreich, M.: Searching for the bomb spike in Danube river sediments: Extracting the anthropogenic impact of Vienna, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8174, https://doi.org/10.5194/egusphere-egu23-8174, 2023.

EGU23-8685 | ECS | Posters virtual | ITS4.2/BG1.12

The application of soil analysis in forensic taphonomy: using pigs as analogues for human corpses 

Giulia Tagliabue, Cristina Cattaneo, and Luca Trombino

Many studies have shown how Environmental Sciences can contribute to the forensic and medico-legal investigations on murder and body concealment dynamics. Nonetheless, most of the research is generally limited to botanical, entomological and anthropological fields leaving out the observation of the active interaction between a decomposing body and the surrounding environment, such as soil. Indeed, a clandestine grave can destroy the valuable forensic evidence as well as prevent the identification of the offender or the victim itself and even the determination of the post-mortem interval (PMI), post-burial interval (PBI) and, overall, the dynamics of the crime act. Therefore, the present experiment, built on the basis of a previous pioneer project carried out in the same area between 2009 and 2011, will be based on the re-enactment of real cases of body disposal, consisting in a combination of multiple methods of concealment, all of them including the inhumation of the remains in a woodland setting. It will consist of the excavation of 32 burials, all dug on the same day, at a depth between 40 and 60 cm involving just as many piglet cadavers (Sus scrofa) weighing between 3 and 5 kg. They will be divided into four different groups, each of which will undergo peculiar treatments: eight will be buried naked; eight clothed; eight will be buried in quicklime and the last eight will be previously hurt. The experiment will be conducted for a total of 730 days and the exhumations of the specimens will be performed in eight increasing time intervals, to achieve different PBIs for each group of subjects (15, 30, 60, 120, 240, 365, 545 and 730 days). At the time of each exhumation biological material, commodities and soil will be sampled and investigated from a geochemical, microscopic (polarizing microscope) and ultramicroscopic (SEM-EDS) point of view, aiming to underline any evidence of mutual exchange of material between the different substrates, as well as any symptom of disturbance, both biochemical and mechanical. As focusing on a multidisciplinary approach, not only this study will allow to reach a standardization for the right reading of trace evidence in real cases of clandestine burials inquiry, but it also will contribute to draw up some guidelines for the exploitation of the parameters registered by the geopedological analytical techniques, which have been neglected for years in the forensic and medico-legal context.

How to cite: Tagliabue, G., Cattaneo, C., and Trombino, L.: The application of soil analysis in forensic taphonomy: using pigs as analogues for human corpses, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8685, https://doi.org/10.5194/egusphere-egu23-8685, 2023.

EGU23-8782 | Posters on site | ITS4.2/BG1.12

Forensic geosciences investigations on experimental fields 

Sebastiano D’Amico, Jason H Byrd, Emanuele Colica, Saviour Formosa, Roberta Somma, Giulia Tagliabue, and Luca Trombino

The search for homicide graves is a very strenuous activity that may lead to the identification of the burial site if it is planned based on articulated scientific approaches considering several aspects of forensic sciences. Moreover, another difficult task in such criminal cases may be the estimation of the Post-Mortem Interval (PMI) of the victim. Discrepancies between PMI estimation through entomological studies and other evaluations may be. This inconsistency is at the base of the necessity to examine and well understand the human decay process of human beings and the decay consequences in the surrounding environmental context. It is noteworthy that several processes may occur on the surrounding site the burial. Phenomena as a depression, a different growth of plants, or the occurrence of peculiar insect associations may be observed on the grave, due to the body’s decay, and the body fluids release in the underground. These aspects may be analysed in experimental fields where pig carcasses, usually used as analogues for the human cadavers, are inhumated in holes dug by means of hand instruments (pick and shovel) or mechanical excavators. These sites may be monitored by applying geological, geophysical, geochemical, and geomatic methods, as well as entomological and botanical characterization of the insects and flora, respectively. The present research is devoted to plan, analyse and monitoring of a simulated experimental field in Malta, where a simulated grave containing a pig carcass will be prepared. The research project is dedicated to geophysical and geomatic surveys to be realized before the excavations and during the project for monitoring the depression development and the shape and dimensions of the leachate plume. Geophysical methods consist of ERT tomographies, seismic and georadar profiles, parallel and orthogonal to the graves. Geological investigations are focused on characterizing the pedogenic profile and the composition, texture, and structure of the soil/sediment. Entomological research is devoted to identifying insect species typically related to body decay. Ideally and in addition to the above, botanical surveys are aimed at defining the main species and differences in the plant growth. The reconstructed evolution of the burial environment may be investigated to better assist criminal investigations into the definition of the PMI in recognition of a burial site and other significative criminological and criminalistic data.

How to cite: D’Amico, S., Byrd, J. H., Colica, E., Formosa, S., Somma, R., Tagliabue, G., and Trombino, L.: Forensic geosciences investigations on experimental fields, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8782, https://doi.org/10.5194/egusphere-egu23-8782, 2023.

EGU23-13026 | ECS | Posters on site | ITS4.2/BG1.12 | Highlight

Old and modern challenges of Forensic Gemmology 

Sebastiano Ettore Spoto

Forensic Gemmology is a branch of Forensic Science where the analysis of gemstones has legal implications, which cannot be set aside, improvised, or, even worse, done with approximation. Local and world markets and archaeological sites can currently encounter a wide range of gemmological objects that are incorrectly declared, treated, or classified. Materials in question are made by also using the latest technologies. Occasionally, cases are brought to court regarding the value of a precious gem in addition to its "authenticity," which often, to be resolved, require complex preparation. Therefore, keeping in mind the significance of gemstone identification, here are specific methodologies discussed to test the authenticity of the gemstones and to find out whether the gemstones are authentic or not. Modern challenges also concern determining whether gemstones were extracted under ethical conditions and determining whether gemstones are of synthetic or natural origins. Thus, forensic examination of gemstones becomes very difficult if proper procedures are not outlaid. The problems that need to be addressed at the international level remain relevant, for instance, creating a standard scheme for determining the ethical origin of colored gemstones, similar to the one existing in the diamond market.

How to cite: Spoto, S. E.: Old and modern challenges of Forensic Gemmology, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13026, https://doi.org/10.5194/egusphere-egu23-13026, 2023.

BG2 – Methods in Biogeosciences

EGU23-1093 | Orals | BG2.1

Lithium isotopes potential in (paleo)ecology 

Fanny Thibon, Jean Goedert, Nicolas Séon, Lucas Weppe, Jeremy E. Martin, Romain Amiot, Sylvain Adnet, Olivier Lambert, Paco Bustamante, Philippe Telouk, Christophe Lécuyer, and Nathalie Vigier

Life evolution has been shaped by marine and continental environmental dichotomy. Particularly, the ecological history of vertebrates is divided into several aquatic and terrestrial phases. Even today, some species spend time in both marine and continental environments during their lifetime. Nevertheless, the timing and location of past ecological transitions, as well as the monitoring of current migration, are still challenging to trace.

To reconstruct the aquatic environments of vertebrates (i.e. seawater vs freshwater), stable (δ13C, δ18O, δ34S) and radiogenic (87Sr/86Sr) isotope systems applied to mineralized tissues have been commonly used in the past decades1–6. Nevertheless, these methods hold some limitations as they cannot be applied universally.

Here, we measured the lithium stable isotope composition of mineralized tissues (δ7Li) from extant vertebrates living in various aquatic environments (seawater, freshwater/terrestrial, and "transitional environments”). We highlight the potential of δ7Li to decipher vertebrates that live in these different environments, in contrast to δ34S and δ18O that cannot distinguish – in some cases – species living in intermediate waters from those living in seawater. Furthermore, we measured the δ7Li values of fossil apatites from extinct vertebrates and obtained values that fall within the range of aquatic environment of their extant relatives7. This new proxy may therefore profit studies in ecology, archaeology and palaeontology.

 

1 M. T. Clementz, A. Goswami, P. D. Gingerich and P. L. Koch, Journal of Vertebrate Paleontology, 2006, 26, 355–370.

2  J. Fischer, S. Voigt, M. Franz, J. W. Schneider, M. M. Joachimski, M. Tichomirowa, J. Götze and H. Furrer, Palaeogeography, Palaeoclimatology, Palaeoecology, 2012, 353–355, 60–72.

3 J. Goedert, C. Lécuyer, R. Amiot, F. Arnaud-Godet, X. Wang, L. Cui, G. Cuny, G. Douay, F. Fourel, G. Panczer, L. Simon, J.-S. Steyer and M. Zhu, Nature, 2018, 558, 68–72.

4 J. Goedert, R. Amiot, D. Berthet, F. Fourel, L. Simon and C. Lécuyer, Sci Nat, 2020, 107, 10.

5 L. Kocsis, A. Ősi, T. Vennemann, C. N. Trueman and M. R. Palmer, Palaeogeography, Palaeoclimatology, Palaeoecology, 2009, 280, 532–542.

6 B. Schmitz, S. L. Ingram, D. T. Dockery and G. Åberg, Chemical Geology, 1997, 140, 275–287.

7 F. Thibon, J. Goedert, N. Séon, L. Weppe, J. E. Martin, R. Amiot, S. Adnet, O. Lambert, P. Bustamante, C. Lécuyer and N. Vigier, Earth and Planetary Science Letters, 2022, 599, 117840.

How to cite: Thibon, F., Goedert, J., Séon, N., Weppe, L., Martin, J. E., Amiot, R., Adnet, S., Lambert, O., Bustamante, P., Telouk, P., Lécuyer, C., and Vigier, N.: Lithium isotopes potential in (paleo)ecology, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1093, https://doi.org/10.5194/egusphere-egu23-1093, 2023.

EGU23-2055 | Posters on site | BG2.1

Silver stable isotopic ratios determined in contaminated soils 

Ales Vaněk, Maria Vaňková, Martin Mihaljevič, and Vojtěch Ettler

Silver isotopic fractionation(s) during metallurgical processes (or other high-T processes) and its fate in mining- and smelter-affected environments, Ag-contaminated soils/sediments remain entirely unknown. Regarding the Ag-ore processing (roasting/smelting technologies), it can be assumed that, similarly to other isotopic systems (e.g., Tl and Cu), the isotopically lighter Ag (enriched in 107Ag) enters the smelter emissions (fly ash), and isotopically heavier Ag (enriched in 109Ag) remains in the residual metal phase. Our preliminary data from the Ag-contaminated soils around a former primary Ag-smelter at Příbram (Czech Rep.) indicate an apparent variability of ε109Ag within soil profiles. The identified ε109Ag values presented for the forest soil profile (Fig. 1) recorded ~0 in the organic horizon (O), ~0-+1 in the organo-mineral horizons (A1 and A2), and up to +7 in the mineral horizon (B). This finding suggests both the isotopically-lighter Ag fraction present in the topsoil (Fig. 1), as well as enhanced 107Ag release during high-T smelting operations, i.e., relative to geogenic Ag (local ore). However, the question that clearly remains to date is to which degree the alteration/chemical processes in soil could have produced the Ag isotopic fractionation and which type of mechanisms (e.g. Ag(I)→Ag0) could represent the key geochemical controls.

Fig. 1 An example of vertical evolution of Ag isotopic signatures (ε109Ag, relative to the NIST SRM 978a Ag standard) and Ag concentrations in a forest soil profile, ~1 km away from a former primary Ag-smelter (Příbram, Czech Rep.). The Ag isotopic data are assigned an estimated error of ±0.7 ε109Ag (2sigma), which is based on our long-term reproducibility of multiple separate analyses (n = 6) of NIST SRM 2782 (Industrial Sludge) (Vaněk et al., unpublished data).

How to cite: Vaněk, A., Vaňková, M., Mihaljevič, M., and Ettler, V.: Silver stable isotopic ratios determined in contaminated soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2055, https://doi.org/10.5194/egusphere-egu23-2055, 2023.

EGU23-4677 | ECS | Orals | BG2.1

Equilibrium and kinetic controls contribute to nitrogen and oxygen isotope effects during anammox in a wastewater treatment system 

Paul Magyar, Damian Hausherr, Robert Niederdorfer, Kun Huang, Joachim Mohn, Helmut Bürgmann, Adriano Joss, and Moritz Lehmann

Anammox plays a pivotal role in both natural and engineered systems as a process that simultaneously converts fixed nitrogen to N2 and regenerates NO3. In aquatic and terrestrial ecosystems, isotopic measurements, especially of the NO3pool, provide an essential constraint on the processes that regulate the supply and elimination of fixed nitrogen, but the isotope effects of anammox remain poorly constrained.

We present measurements of the δ15N and δ18O of NO3, NO2, and NH4+ as processed by anammox in a mixed microbial community enriched for N removal from wastewater. We find that oxygen isotope effects expressed in NO2include a substantial contribution from equilibration reactions with water superimposed on kinetic isotope effects. Equilibrium between water and NO2during processing by anammoxis greatly accelerated above rates observed under abiotic conditions even during growth phases when NO2 is rapidly being consumed. In turn, δ18O of NO3 nearly completely reflects the incorporation of O atoms derived from water with little additional isotopic fractionation. The δ15N values of NO3 and NO2 also show evidence for an equilibrium isotope exchange reaction between these molecules, which raises the possibility that nitrite oxidation is partially reversible, while introducing a high degree of variability into the δ15N of NO3 generated by anammox. Finally, variation observed in the δ15N of NH4+ consumed by anammox can be connected to physiological limitations within the anammox cell.

Despite this complexity, we were able to use NO2 and NO3isotope measurements to diagnose changes in the activity of anammox and related processes within the wastewater treatment system during a low-temperature perturbation experiment. These results provide new constraints for interpreting the variability in δ15N and δ18O of NO3in natural systems, with implications for estimating relative rates of fixed N turnover processes.

How to cite: Magyar, P., Hausherr, D., Niederdorfer, R., Huang, K., Mohn, J., Bürgmann, H., Joss, A., and Lehmann, M.: Equilibrium and kinetic controls contribute to nitrogen and oxygen isotope effects during anammox in a wastewater treatment system, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4677, https://doi.org/10.5194/egusphere-egu23-4677, 2023.

EGU23-5210 | ECS | Posters on site | BG2.1

Fractionation of nitrogen and oxygen isotopic composition in N2O produced by bacterial denitrification 

Noémy Chénier, Paul M. Magyar, Lukas Emmenegger, Moritz F. Lehmann, and Joachim Mohn

The isotopic composition of nitrous oxide (N2O) reveals valuable information on the biological production sources that contribute to N2O accumulation in the atmosphere, i.e. denitrification, nitrifier-denitrification and nitrification1. Isotopic fingerprints for each of these microbial pathways have been identified in past work, however, overlapping signatures of co-occurring N2O production processes2, and limitations in the robustness of associated fractionation factors under varying growth/environmental conditions3 still pose significant challenges.

We will present data from the initial phase of our project, where we study N2O production and associated N and O isotopic fractionation by the denitrifier Pseudomonas aureofaciens, grown in the laboratory under different growth conditions and thus different reaction kinetics. N2O production was quantified on-line by Fourier-Transformation IR-spectroscopy (FTIR), and the isotopic composition of produced N2O was determined by quantum cascade-laser-absorption spectroscopy (QCLAS). The combination of N2O production and isotope data (continuously measured) allowed us to elucidate changes in N and O isotope fractionation in response to changing reaction kinetics.

In a later phase of the project, we will expand our isotope-analytical capability by including also the doubly-substituted molecules of N2O, 15N15N16O (556), 14N15N18O (458) and 15N14N18O (548). More specifically, we will interrogate the symmetry of N – N bond formation, verify combinatorial effects during N2O production, and we will test whether Δ556, Δ458, and Δ548 (and the preference for 15N substitution in the central/terminal N-position) can be applied as proxies for reaction kinetics4, 5.  

1 Yu, L., Harris, E., Lewicka Szczebak, D., Barthel, M., Blomberg, M.R., Harris, S.J., Johnson, M.S., Lehmann, M.F., Liisberg, J., Müller, C. and Ostrom, N.E., 2020. What can we learn from N2O isotope data?–Analytics, processes and modelling. Rapid Communications in Mass Spectrometry, 34(20), p.e8858.

2 Kantnerová, K., Tuzson, B., Emmenegger, L., Bernasconi, S.M. and Mohn, J., 2019. Quantifying isotopic signatures of N2O using quantum cascade laser absorption spectroscopy. Chimia, 73(4), pp.232-232.

3 Haslun, J.A., Ostrom, N.E., Hegg, E.L. and Ostrom, P.H., 2018. Estimation of isotope variation of N2O during denitrification by Pseudomonas aureofaciens and Pseudomonas chlororaphis: implications for N2O source apportionment. Biogeosciences, 15(12), pp.3873-3882.

4 Yeung, L.Y., 2016. Combinatorial effects on clumped isotopes and their significance in biogeochemistry. Geochimica et Cosmochimica Acta, 172, pp.22-38.

5 Kantnerová, K., Hattori, S., Toyoda, S., Yoshida, N., Emmenegger, L., Bernasconi, S.M. and Mohn, J., 2022. Clumped isotope signatures of nitrous oxide formed by bacterial denitrification. Geochimica et Cosmochimica Acta, 328, pp.120-129.

How to cite: Chénier, N., Magyar, P. M., Emmenegger, L., Lehmann, M. F., and Mohn, J.: Fractionation of nitrogen and oxygen isotopic composition in N2O produced by bacterial denitrification, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5210, https://doi.org/10.5194/egusphere-egu23-5210, 2023.

EGU23-6603 | ECS | Orals | BG2.1

Uniquely low stable iron isotopic signatures in deep marine sediments caused by Rayleigh distillation 

Male Köster, Michael Staubwasser, Anette Meixner, Simone A. Kasemann, Hayley R. Manners, Yuki Morono, Fumio Inagaki, Verena B. Heuer, Sabine Kasten, and Susann Henkel

Microbially mediated iron (Fe) reduction is suggested to be one of the earliest metabolic pathways on Earth and Fe(III)-reducing microorganisms might be key inhabitants of the deep and hot biosphere [1, 2]. Since microbial Fe cycling is typically accompanied by Fe isotope fractionation, stable Fe isotopes (δ56Fe) are used as tracer for microbial processes in modern and ancient marine sediments [3, 4]. Here we present Fe isotope data for dissolved and sequentially extracted sedimentary Fe pools from subseafloor sediments that were recovered during International Ocean Discovery Program Expedition 370 from a 1,180 m deep hole drilled in the Nankai Trough off Japan where temperatures of up to 120°C are reached at the sediment-basement interface. The expedition aimed at exploring the temperature limit of microbial life and identifying geochemical and microbial signatures that differentiate the biotic and abiotic realms [5, 6]. Dissolved Fe (Fe(II)aq) is isotopically light throughout the ferruginous sediment interval but some samples have exceptionally light δ56Fe values. Such light δ56Fe values have never been reported in natural marine environments and cannot be solely attributed to microbially mediated Fe(III) reduction. We show that the light δ56Fe values are best explained by a Rayleigh distillation model where Fe(II)aq is continuously removed from the pore water by diffusion and adsorption onto Fe (oxyhydr)oxide surfaces. While the microbially mediated Fe(II)aq release has ceased due to an increase in temperature beyond the threshold of mesophilic microorganisms, the abiotic diffusional and adsorptive Fe(II)aq removal continued, leading to uniquely light δ56Fe values. These findings have important implications for the interpretation of Fe isotope records especially in deep subseafloor sediments.

 

References:

[1] Vargas, M. et al., 1998. Nature 395: 65-67.

[2] Kashefi, K. and Lovley, D.R., 2003. Science 301: 934-934.

[3] Beard, B.L. et al., 1999. Science 285: 1889-1892.

[4] Anbar, A.D. and Rouxel, O., 2007. Annu. Rev. Earth Planet. Sci. 35: 717-746.

[5] Heuer, V.B. et al., 2017. In Proc. IODP Volume 370.

[6] Heuer, V.B. et al., 2020. Science 370: 1230-1234.

How to cite: Köster, M., Staubwasser, M., Meixner, A., Kasemann, S. A., Manners, H. R., Morono, Y., Inagaki, F., Heuer, V. B., Kasten, S., and Henkel, S.: Uniquely low stable iron isotopic signatures in deep marine sediments caused by Rayleigh distillation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6603, https://doi.org/10.5194/egusphere-egu23-6603, 2023.

EGU23-7883 | ECS | Posters on site | BG2.1

Effects of different slurry application techniques on Nitrogen Use Efficiency (NUE) in an extensive grassland 

Sebastian Floßmann, Kaiyu Lei, Sigrid van Grinsven, Jörg Völkel, Ingrid Kögel-Knabner, and Michael Dannenmann

Optimized slurry management targeted to increase nitrogen use efficiency (NUE) can be fundamental for limiting fertilizer N losses from agricultural grasslands causing eutrophication of ground- and surface water as well as air pollution. However, a holistic assessment of both agronomic and environmental impacts including key soil functions is still missing. This study aims to provide such information by assessing the impacts of traditional vs. modern slurry application techniques on NUE, hydrological and gaseous N losses, productivity and fodder quality, soil organic nitrogen formation and total N balances.  In a plot-scale grassland experiment 15N enriched slurry was applied after the first cut in early summer. The application treatments included: (1) traditional slurry broadcast spreading under dry weather; (2) application like (1) followed by a heavy rainfall event to increase slurry infiltration into soil; (3) broadcast spreading of slurry diluted with water; (4) injection of slurry into soil via shallow slits; and (5) injection of slurry into soil via deep slits. Variant (4) and (5) represent modern trailing shoe injections requiring extensive machinery. Fates of fertilizer N such as plant uptake, immobilization in soil and microbial biomass as well as NO3 leaching were investigated by 15N tracing approaches in order to create full N balances. For this, biomass harvest and soil sampling were conducted after a growth period of 2 months. Here, we will present first results of our work that are expected to provide highly relevant decision support for grassland management. 

How to cite: Floßmann, S., Lei, K., van Grinsven, S., Völkel, J., Kögel-Knabner, I., and Dannenmann, M.: Effects of different slurry application techniques on Nitrogen Use Efficiency (NUE) in an extensive grassland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7883, https://doi.org/10.5194/egusphere-egu23-7883, 2023.

EGU23-8103 | ECS | Orals | BG2.1

Lysimeter-based full N balance as a tool to test field N2 flux measurements 

Irina Yankelzon, Lexie Schilling, Nicole Wrage-Moennig, Arne Tenspolde, Ulrike Ostler, Klaus Butterbach-Bahl, Lorenz Hartl, Rainer Gasche, Amanada Matson, Reinhard Well, Clemens Scheer, and Michael Dannenmann

Measuring soil dinitrogen (N2) emissions is notoriously challenging under field conditions. Hence, N2 emissions represent a significant uncertainty in the nitrogen mass balance of terrestrial ecosystems. The 15N gas flux (15NGF) method is the only method currently available for directly quantifying N2 emissions in situ. However, this method has rarely undergone independent validation under field conditions. In this study, our objectives were to: (1) Quantify N2 emissions and their role in the fertilizer N mass balance of a wheat rotation using the 15NGF method (2) Verify the obtained quantities of N2 emissions using a mass balance approach and (3) Verify the temporal N2 emission dynamics at the soil-atmosphere interface using vertical soil profiles of 15N2 enrichment.

To achieve these objectives, we grew winter wheat in lysimeters and applied 15N enriched mineral fertilizers via fertigation in three doses (sum 170 kg N ha-1). We then analyzed gaseous (NH3, N2O, N2) and hydrological N losses, as well as fertilizer N fates in plant and soil, and 15N2 enrichment in soil air.

Our results showed that N2 emissions directly measured using the 15NGF method amounted to 30 ± 4 kg N ha-1, which was equivalent to 18 ± 3 % of the applied fertilizer N. These measurements agreed with unrecovered fertilizer N obtained from the 15N fertilizer mass balance, although the latter had large inherent uncertainty (21 ± 21 kg N ha-1). N2O emissions, however, were negligible (0.14 ± 0.02 kg N ha-1). The temporal variability of measured N2 emissions after fertilizer additions was generally well explained by 15N2 enrichment in soil gas.

Overall, we provide independent validation of the 15NGF method in measuring N2 emissions in the field and highlight the significant role of these emissions in the nitrogen balance of crop systems. Our data also suggest that soil gas measurements in combination with diffusion modeling could serve as an alternative method for quantifying N2 emissions. These results should encourage a wider application of the 15NGF method in order to improve our understanding of N2 emissions and reduce the current uncertainties in estimates of these emissions.

How to cite: Yankelzon, I., Schilling, L., Wrage-Moennig, N., Tenspolde, A., Ostler, U., Butterbach-Bahl, K., Hartl, L., Gasche, R., Matson, A., Well, R., Scheer, C., and Dannenmann, M.: Lysimeter-based full N balance as a tool to test field N2 flux measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8103, https://doi.org/10.5194/egusphere-egu23-8103, 2023.

Identifying and quantifying sources and cycling of nitrogen is important for understanding not only aquatic ecosystems but also planning water resource management, mitigating urban and agricultural pollution, and optimizing government policy. Stable isotopes of dissolved nitrate and nitrite (δ15N, δ18O and δ17O) have been useful in distinguishing between the diverse nitrogen sources and sinks and help understand large scale global ocean processes as well as revealing major changes in agricultural land use and urbanization. 

Despite the strength of dissolved nitrate and nitrite stable isotope analysis, the strong barrier for uptake using the favored contemporary methods (bacterial denitrifier and Cd-azide reaction) due to the laborious multi-step methods, maintenance of anerobic bacterial cultures and use of highly toxic chemicals has limited the analysis to highly specialized laboratories. We evaluate the performance of the Elementar EnvirovisION using the new Titanium (III) reduction method (Altabet et al., 2019) for one step conversion of nitrate into N2O for IRMS analysis.   

The EnvirovisION has been developed for high performance analysis of CO2, N2O and CH4 and dissolved nitrate. The system has the capacity to be rapidly customized for specific needs with options for dual GC columns supporting the Weigand ‘heart-cut’ N2O method (Weigand et al., 2016) and sequential N2 and N2O analysis from a single atmospheric sample. 

How to cite: Barker, S., Preece, C., Berstan, R., and Seed, M.: Analysis of dissolved nitrate stable isotopes using the one-step Ti (III) reduction method and Elementar EnvirovisION System  , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8338, https://doi.org/10.5194/egusphere-egu23-8338, 2023.

EGU23-9366 | Posters on site | BG2.1

Temporal and spatial variations in the isotope hydrobiogeochemistry (H, C, O, S, Ra) of a managed river draining a lowland towards the Baltic Sea 

Michael E. Böttcher, Cátia M. Ehlert von Ahn, Christoph Malik, Julia Westphal, Benjamin Rach, Carla Nantke, Anna-Kathrina Jenner, Rhodelyn Saban, Vera Winde, and Iris Schmiedinger

The flow path of a river draining a lowland in the southern Baltic Sea, the Warnow River, was investigated to evaluate its freshwater composition as a source of dissolved substances to regional coastal waters. A spatial study was carried out once to follow the variations from the source to the estuary. A temporal study in the composition as a function of the season, during 6 years (2017-2022), was carried out at a site just before the river reaches the estuary. Surface water was sampled to analyze major and tracer elements, stable (H, C, O, S), and unstable (Ra) isotopes. The results show that the composition of the Warnow River along the flow path is controlled by a complex interplay between in-situ processes, exchange with the atmosphere, diffuse groundwater, and surface water inlets. On a temporal scale, pH, nutrient, and redox sensitive trace element concentrations are strongly impacted by pelagic primary production in spring. During summer and autumn, influences occurred by benthic microbial activity, associated diffusive release from soils/sediments, and surface water inlets. Throughout the investigation period, the Warnow River was a source of isotopically light CO2 to the atmosphere and DIC to the estuarine waters. The delivered DIC concentrations seem to vary with the season due to changes in biological pelagic and benthic activity. DOC was derived from a mixture of C3 organic sources and fertilizers. From concentration-discharge relationships, examples of dilution, mobilization, and chemostasis trends were found. Discharge-controlled seasonal trends are superimposed by system-internal processes and the hydrological consequences of river and drainage management. Our analysis thus provides new insights into the controls on the variations of water and solutes in a managed river at the land-sea interface as part of the regional hydrological cycle of a lowland catchment coastal water system.

 

The study was supported by the DFG research training group BALTIC TRANSCOAST, DAAD ,  and the BMBF project CARBOSTORE/COOLSTYLE

How to cite: Böttcher, M. E., Ehlert von Ahn, C. M., Malik, C., Westphal, J., Rach, B., Nantke, C., Jenner, A.-K., Saban, R., Winde, V., and Schmiedinger, I.: Temporal and spatial variations in the isotope hydrobiogeochemistry (H, C, O, S, Ra) of a managed river draining a lowland towards the Baltic Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9366, https://doi.org/10.5194/egusphere-egu23-9366, 2023.

EGU23-10139 | ECS | Posters on site | BG2.1 | Highlight

The influence of high evaporative conditions on peat-forming mosses in the Antarctic Peninsula 

Danielle Jones, Dulcinea Groff, and David Beilman

Low-elevation coastal ecosystems of the northern Antarctic Peninsula are responding to rapid climate change by expansion of ice-free areas and increased vegetation cover. The record-setting air temperatures during the austral summer of 2020 provided an opportunity to evaluate the sensitivity of peat-forming and carbon accumulating mosses to conditions with high evaporative demand, a departure from the typical wet, cold, and windy conditions of the northern Antarctic Peninsula. Mosses are sensitive to environmental change and have been used as archives of paleoclimate information where few terrestrial records exist. However, it is still unclear how much of an influence increased evaporative demand, source water variation, or microclimate can have on moss leaf cellulose. We collected environmental waters and moss surface samples to explore the influence of microclimate, persistent snowmelt, and evaporation on moss tissue waters and cellulose for two moss species, Chorisodontium aciphyllum and Polytrichum strictum. Using the δ18O isotope values of moss tissue waters and leaf alpha-cellulose from surface samples, we compared the enrichment found in mosses to the enrichment in local water sources.  

δ2H and δ18O isotopes of moss tissue waters ranged from -87 to -23 and -10.6 to 0.6, respectively, indicating significant enrichment relative to our environmental water samples (δ2H values of -98.3 to -48.7 and δ18O values of -12.1 to -5.21) and long-term summer precipitation (February, δ2H values of -66.9 ± 15.9‰ and δ18O values of -8.11 ± 2.20‰, Vernadsky Station). Negative correlations between δ18O of moss water and the daily average and maximum relative humidity (on the day of collection) (r = -0.44; p < 0.001 and r = -0.62; p < 0.001, respectively) suggest that conditions resulting in high evaporative demand may have a dominant effect and imprint on the δ18O of moss cellulose. We found no relationship between δ13C values of alpha-cellulose, which reflect changes in CO2 diffusivity with moisture conditions, and microclimate variables or average temperature and relative humidity on the day of sample collection. This is possibly the result of discrepancies between peak growth and seasonal peaks in cumulative evaporation leading the tissues to incorporate multiple seasons. The isotope values of moss waters likely reflect the anomalously warm summer on the Antarctic Peninsula, as indicated by the divergence from moss water lines published in non-record-setting summers. Although the δ18O values of moss tissue waters are a proxy for the composition of δ18O values of summer precipitation, it is critical to consider the imprint of high evaporative conditions, in addition to summer precipitation composition, when reconstructing past environmental conditions using cellulose from peat archives. 

How to cite: Jones, D., Groff, D., and Beilman, D.: The influence of high evaporative conditions on peat-forming mosses in the Antarctic Peninsula, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10139, https://doi.org/10.5194/egusphere-egu23-10139, 2023.

EGU23-11001 | ECS | Orals | BG2.1

Development of new proxies for sulfurization and paleo-environmental conditions using a Rock-Eval coupled to MC-ICPMS 

Hadar Cohen-Sadon, Yoav Oved Rosenberg, Shimon Feinstein, and Alon Amrani

The sulfur (S) cycle is directly linked to the global carbon and iron cycles. Sulfur plays an important role in the preservation of organic matter (OM) over geological time scales. Assimilatory and dissimilatory sulfate reductions (ASR and DSR, respectively) are the main processes shaping the sulfur cycle and carry different sulfur isotopic fractionation (-1 to -3 ‰, and -20 to -75 ‰, respectively). The reduced S species produced by DSR react during early diagenesis with OM (sulfurization) to form organic-S, and/or with iron (Fe) to form pyrite. Although in most cases organic- and pyritic-S have a common origin (i.e., DSR), organic-S in marine sediments is typically 34S enriched relative to its co-existing pyrite by up to 40 ‰ (global average is ~10‰). This isotopic difference is assumed to depend on specific paleo-environmental conditions and different sulfurization pathways (open-closed system for sulfate, Fe availability, redox state, OM type, etc.). Different sulfurization pathways may affect the type and distribution of S-bonds in sedimentary OM and thus can strongly affect the structure and character of sedimentary OM.

Recently, new instrumentations and methods were developed for the rapid determination of organic- and pyritic-S concentrations and δ34S values using a Rock-Eval analyzer (RE) coupled to a MC-ICPMS. A new parameter, Tmax-S (the temperature at maximum peak of organic-S generation), was suggested to represent the organic-S thermal stability in pyrolysis conditions. Applying this parameter to thirteen organically rich and thermally immature samples of various geological settings and paleo-environmental origins revealed several interesting empirical correlations. The Tmax-S value was found to differ among the rocks and to linearly correlate (R2=0.98) with the percentage of pyrolyzed organic-S out of the total organic-S in the rock. Moreover, Tmax-S was strongly correlated with the distribution of sulfidic and thiophene compounds in the rock (R2=0.87). This suggests that Tmax-S may be used as a tool to evaluate the distribution of different S-bonds in the organic molecule, and, as a proxy, their sulfurization and paleoenvironmental conditions.

The rock samples' Tmax-S values also correlate with their isotopic difference between organic- and pyritic-S (Δ34Sorganic-pyrite; R2=0.76). The Δ34Sorganic-pyrite values of the rocks extended between 1 to 40‰ where marine samples characterized by low Tmax-S values (~400-450 °C) and large Δ34Sorganic-pyrite values (~20-40‰) and lacustrine samples by high Tmax-S values (~450-480 °C) and small Δ34Sorganic-pyrite values (~1-5‰). This correlation further supports the link between paleo-environmental conditions, specific sulfurization pathways, and the organic-S structures (represented by Tmax-S). It may shed light on some fundamental questions regarding the role of S isotopic distribution between pyrite and OM during deposition and diagenesis.

How to cite: Cohen-Sadon, H., Rosenberg, Y. O., Feinstein, S., and Amrani, A.: Development of new proxies for sulfurization and paleo-environmental conditions using a Rock-Eval coupled to MC-ICPMS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11001, https://doi.org/10.5194/egusphere-egu23-11001, 2023.

EGU23-12808 | Orals | BG2.1

Exploring new protocols for bulk off-line fluid inclusion extraction for the analysis of δ13C-CH4 using a Cavity Ring-Down Spectroscopy (CRDS) analyzer. 

Orlando Sébastien Olivieri, Alberto Vitale Brovarone, Jens Fiebig, Francesco Ressico, Valentina Marassi, Sonia Casolari, and Olivier Sissmann

For decades, the search for terrestrial abiotic CH4 has been a central quest in geology and astrobiology. Most of this research has focused on crustal fluid samples collected at surface seeps, hydrothermal vents, and wells. Nonetheless, in such open systems processes like mixing with shallow biotic CH4, oxidation, and diffusion can lead to large uncertainties in the initial composition of deeply originated CH41. Extracting natural CH4 from fluid inclusions entrapped in minerals could overcome the effects of shallow contamination occurring in natural open systems and shed light on the origin of deep CH4 in a wide variety of geodynamic settings2,3.  

In this abstract, we present a novel approach for bulk off-line fluid inclusion extraction for the analysis of δ13C-CH4 using a Cavity Ring-Down Spectroscopy (CRDS) analyzer (Picarro G2201-i). Two fluid extraction techniques were compared: ball milling in ZrO2 jars and sample crushing in a stainless-steel sealed tube under a piston. The accuracy and precision of the different protocols was evaluated with blanks, CH4 isotopic labelling and interlaboratory comparisons.   

Blanks and isotopically labelled tests with the ball milling technique suggested that milling speed, and duration, and sample mass and type may strongly affect the CH4 concentrations and isotopic compositions measured by the CRDS analyser. These effects are mainly ruled by the blank production of CH4 –demonstrated by gas chromatography analyses– and potentially other molecules induced by frictional heating. The blank gases may cause interference effects on the absorption bands detected by the CRDS analyser. This effect was marked by a large offset in the δ13C-CH4 measured in the high-range analytical modes of the Picarro G2201-i. The magnitude of the interference was inversely correlated to the CH4 concentration.Other processes such as CH4 diffusion and adsorption may play a role in the observed changes in CH4 concentrations and isotopic compositions. Experimental conditions involving high CH4 concentrations and sample mass could well reproduce CH4 isotopic composition. 

Crushing in a sealed stainless-steel tube produces lower blank levels compared to ball milling, nevertheless the crushing efficiency and CH4 release is lower due to smaller rock sample size.   

The presented ball milling protocol provides a simple and fast way to extract and accurately analyse CH4 hosted in fluid inclusions even if great care should be considered for samples with low CH4 concentrations where contamination and interferences can potentially alter the CH4 isotopic signature of natural samples.   

 

References 

  • 1 - Young et al. (2017). 10.1016/j.gca.2016.12.041 
  • 2 - Klein et al. (2019). 10.1073/pnas.1907871116 
  • 3 - Grozeva et al. (2020). 10.1098/rsta.2018.0431 

 

This work is part of project that has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 864045).    

How to cite: Olivieri, O. S., Brovarone, A. V., Fiebig, J., Ressico, F., Marassi, V., Casolari, S., and Sissmann, O.: Exploring new protocols for bulk off-line fluid inclusion extraction for the analysis of δ13C-CH4 using a Cavity Ring-Down Spectroscopy (CRDS) analyzer., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12808, https://doi.org/10.5194/egusphere-egu23-12808, 2023.

EGU23-13490 | ECS | Posters on site | BG2.1

New insights into benthic nitrogen cycling using natural-abundance stable isotopes measurements 

Alessandra Mazzoli, Cameron M. Callbeck, Tim J. Paulus, Claudia Frey, Jakob Zopfi, Sergei Katsev, Donald E. Canfield, and Moritz F. Lehmann

Marine and lacustrine benthic habitats represent hotspots of nitrogen (N) turnover, with many N transformation processes occurring simultaneously, and at high rates. More specifically, sedimentary microbial reduction of nitrate to dinitrogen (N2), and other modes of N2 production (e.g., anammox), are the most important sinks of fixed N in aquatic environments. Natural abundance stable isotope ratio measurements can be employed to help disentangling N-loss mechanisms, given that the isotope effects (e) associated with each process are well studied.

In our study, we surveyed an array of lacustrine and marine benthic environments and assessed the isotopic composition (d15N and d18O) of porewater ammonium (NH4+) and nitrate (NO3-) – the key substrates driving the various N transformation pathways, such as denitrification, anammox, nitrification and dissimilatory nitrate reduction to ammonium (DNRA). We further examined how benthic N isotope dynamics vary in different sedimentary regimes, with distinct organic matter (OM) mineralization rates. We expect the relative importance of the various N pathways to affect the NH4+ and/or NO3- isotope pools differentially.

Our preliminary porewater d15N-NH4+ results suggest a diverse pattern with regard to the isotope enrichments between oligotrophic lakes, characterized by relatively strong depth gradients, and eutrophic lakes, where no significant depth gradient was observed. We hypothesize that this distinction could be attributed to different organic N availability and/or anammox contributions in the surveyed environments. Furthermore, we compared rate measurements (based on 15N addition experiments) to the N and O nitrate isotopic signatures to quantify processes, such as denitrification and DNRA. To investigate N isotope fractionation within the narrow nitracline, we employed the whole-core squeeze method, which provided a high-resolution porewater NO3-profile. Using this method, we found that the calculated community nitrate consumption e values at the nitracline (eelim_porewater) showed strong variability among the surveyed settings. We attribute such variation to shifts in the relative importance of denitrification versus DNRA and anammox between lakes of different trophic states. Overall, eelim_porewater wasconsiderably below 25‰ – the value generally reported for the biological isotope effect of denitrification (edenit).

How to cite: Mazzoli, A., Callbeck, C. M., Paulus, T. J., Frey, C., Zopfi, J., Katsev, S., Canfield, D. E., and Lehmann, M. F.: New insights into benthic nitrogen cycling using natural-abundance stable isotopes measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13490, https://doi.org/10.5194/egusphere-egu23-13490, 2023.

EGU23-13891 | ECS | Orals | BG2.1

There and back again: Combining hydrogen and strontium isotopes refines the trans-Saharan migratory patterns of the butterfly Vanessa cardui 

Megan Reich, Sana Ghouri, Samantha Zabudsky, Gerard Talavera, and Clement Bataille

Migratory insects serve an important role to ecosystems and economies as they participate in the long-distance transfer of nutrients, pollen, and biomass. However, migratory insects are understudied, especially compared to birds and mammals, partially because traditional tracking techniques (e.g. mark-recapture, biologgers) are often ineffective for insects because insects are small, short-lived, and numerous. Thus, isotope geolocation has become an effective tool for studying dispersing insects. The painted lady butterfly (Vanessa cardui (L.)) is a virtually cosmopolitan species that was recently found to make regular, annual multi-generational migrations across the Sahara Desert. Previous work geolocating painted ladies with hydrogen isotopes has shown early spring migratory movements of painted ladies from sub-Saharan Africa to Mediterranean Europe and autumn movements to the sub-Sahara from Europe. However, these previous works using hydrogen isotopes were unable to offer refined estimates of natal origin due to the inherent limitations of the technique. Here, we update previous hydrogen isotope-based geographic assignment by (1) using an updated model of hydrogen isotope variations across the landscape (i.e., isoscape), (2) combining with strontium isotope-based geographic assignment, and (3) expanding the number of geolocated butterflies to include capture locations on both sides of the Sahara Desert across different years. Using this method, we spatially refine previous estimates of the natal origins of successful trans-Saharan migrants and estimate the distances that successful migrants travelled. Overall, this study demonstrates the advantages of combining hydrogen and strontium isotopes for the geographic assignment of migratory butterflies and further advances our understanding of long-distance insect migration.

How to cite: Reich, M., Ghouri, S., Zabudsky, S., Talavera, G., and Bataille, C.: There and back again: Combining hydrogen and strontium isotopes refines the trans-Saharan migratory patterns of the butterfly Vanessa cardui, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13891, https://doi.org/10.5194/egusphere-egu23-13891, 2023.

EGU23-14655 | ECS | Posters on site | BG2.1

Unravelling the formation paths of amorphous hydroxyaluminosilicates and hydrous ferric silicates: Evidence from silicon isotopes 

Franziska M. Stamm, Andre Baldermann, Daniel A. Frick, Dorothee Hippler, and Martin Dietzel

Silicate mineral weathering and the resulting formation of clay minerals are key processes at the Earth’s surface. Reverse weathering reactions regulate the evolution of ocean pH and chemistry, atmospheric carbon dioxide budget, soil formation and associated nutrient and element transfer within local and global biogeochemical cycles. A key element released during weathering processes is silicon (Si), that enters the biogeochemical cycle as dissolved silicic acid (Si(OH)4 or DSi). During the transport of DSi through the hydro-, bio-, pedo- and lithosphere towards the ocean, DSi is involved in the formation of new silicate minerals (i.e., clay minerals) in particular in the critical zone (CZ). Here, DSi is frequently precipitating as gel-like, amorphous phases such as short range ordered hydroxyaluminosilicate phases (HAS: e.g., allophane) or as hydrous ferric silicates (HFS: e.g., hisingerite). These highly reactive minerals are known precursors to the formation of important soil clay minerals e.g., within the smectite group.

The individual reaction pathways and the environmental controls underlying HAS and HFS formation within the CZ are not yet well constrained. Si isotope fractionation throughout HAS and HFS formation is a key tool to decode and assess such enigmatic reaction mechanisms. Therefore, a series of allophane-hisingerite precipitation experiments has been performed to investigate Si isotope fractionation to potentially resolve mechanisms and conditions underlying the formation of HAS and HFS phases. Kinetic and equilibrium Si isotope fractionation between reactive fluid and solid phases are studied at high temporal resolution. Isotope exchange mechanisms are investigated using the three-isotope method, which is a novel proxy to trace the direction and the progress of low-temperature water-mineral/rock interactions.

How to cite: Stamm, F. M., Baldermann, A., Frick, D. A., Hippler, D., and Dietzel, M.: Unravelling the formation paths of amorphous hydroxyaluminosilicates and hydrous ferric silicates: Evidence from silicon isotopes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14655, https://doi.org/10.5194/egusphere-egu23-14655, 2023.

EGU23-15191 | Orals | BG2.1

Determining the relevance of common mycelial networks in the nitrogen nutrition of plants adapted to semi-arid ecosystems 

Alberto Andrino, Asunción Morte, Francisco Arenas, Aline Figueiredo, Leopold Sauheitl, Alfonso Navarro, Ángel L. Guarnizo, Georg Guggenberger, and Jens Boy

Plants in semi-arid environments have adapted to scarce nitrogen (N) resources by becoming more efficient at using and taking it up, or by relying on symbiotic organisms. Common mycelial/mycorrhizal networks (CMNs) may help plants access and assist to a spatio-temporal redistribution of resources in soil. While CMNs have been extensively investigated in temperate forests and grasslands, their importance in semi-arid environments is still uncertain. This study evaluates the existence and importance of CMNs in N translocation in semiarid environments, using Helianthemmum almeriense as the host plant mycorrhized with Terfezia claveryi. We hypothesize that the presence of CMNs is a response mechanism to N scarcity due to soil heterogeneity. Through this mechanism, host plants and mycorrhizal fungi provide redistribution of N, playing a determinant role at all spatial scales, from the facilitation of seedling establishment to the persistence and coexistence of different plant communities. To test our hypothesis, we designed a mesocosm that allowed only hyphae to cross into an adjacent compartment. Three different tests were used to assess the existence and directionality of CMN. In the first test (T1), an adult plant was labeled with 15N and on the other side, only unlabeled soil was present. In this way, we could check if the mycorrhizal fungus tends to homogenously distribute the 15N to places where there is no other plant. In the second test (T2) we had an adult plant and in the adjacent compartment, four-week-old seedlings that were already mycorrhized with mycelium coming from the compartment with the adult plant. In this case, the 15N marker was applied where the adult plant was located, and we checked whether there was a transfer of 15N to the seedlings. In T3, we used a set of mesocosms equal to T2, but this time 15N was applied on the side where the seedlings were located. The idea was to determine whether the distribution of the 15N was proportional to the size of the plant that could receive it. The three types of mesocosms were sampled before labeling (day 0), 7 and 14 days after labeling. Our results reveal that 15N translocation to adjacent compartments occurred in all three tests, but in significantly different amounts. The translocation of 15N was significantly higher in those tests where there was a plant in the adjacent compartment (Tests 2 and 3) compared to T1. We also found that the contribution (%) of 15N to the total plant N pool was significantly higher for one-month-old seedlings in both T2 and T3, compared to adult plants. Under controlled greenhouse conditions, we have shown that the mycelium seems to act as an effective hub for N translocation, but we have not found the amounts transferred under our experimental conditions to be nutritionally remarkable. Our results should be further evaluated under natural conditions, to verify whether this N transfer has a greater nutritional significance than that found under controlled conditions, and also whether this CMN may play a more important role in signaling between plants adapted to semi-arid regions.

How to cite: Andrino, A., Morte, A., Arenas, F., Figueiredo, A., Sauheitl, L., Navarro, A., Guarnizo, Á. L., Guggenberger, G., and Boy, J.: Determining the relevance of common mycelial networks in the nitrogen nutrition of plants adapted to semi-arid ecosystems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15191, https://doi.org/10.5194/egusphere-egu23-15191, 2023.

EGU23-16065 | Posters on site | BG2.1

Isotopic tracking of condensation, infiltration and interstitial water to detect microbial activity in caves 

Angel Fernandez-Cortes, Tamara Martin-Pozas, Soledad Cuezva, Fernando Gazquez, David Benavente, Juan Carlos Cañaveras, Cesareo Saiz-Jimenez, and Sergio Sanchez-Moral

Water plays a key role in the colonization and ecology of microorganisms in natural subterranean environments since it controls their metabolic activity and the microbe-mineral interactions. In turn, microbial activity leaves its signature in groundwater. For instance, the aerial hyphae of Actinobacteria colonizing cave-rock surfaces and sediments act as vapour condensation nuclei and facilitate the retention of interstitial water in the porous system of rocks, sediments and speleothems.

Here, we present the results of exhaustive monitoring of cave waters from Pindal Cave (northern Spain), a shallow and well-ventilated cave on the coastline, with extensive microbial colonization on the sediments and walls surfaces. This study sheds light on the detection of biosignatures based on stables isotopes of cave waters and controlled by underground-dwelling microorganisms. The isotopic composition (d18O and dD) of seepage waters (fast drips, soda straws and gours) and condensation droplets were determined by cavity ring-down spectroscopy (CRDS). An analytical set-up based on a CRDS analyser coupled to an Induction Module enabled the step-heating of moonmilk deposits and other substrates with distinct degrees of microbial colonization, and the selective release of their interstitial water for isotope analyses.

The δ18O and δD values of the in-cave waters correlate linearly (δD=7.71·δ18O+12.28; R2=0.97), like the Local Meteoric Water Line (δD=7.00·δ18O+6.77; R2=0.92, based on the of isotopes composition of regional rain). The offset of d-excess between the cave waters and the LMWL would indicate a significant recharge by occult precipitation linked to local coastal fogs. The isotopic composition of dripping water,  -5.7‰ [-6.7 to -4.8 ‰] for  d18O and -31.3‰ [-39.0 to -22.7 ‰] for dD, agree with the water samples from the gours located far from the cave entrance, with some slight deviations indicating evaporation processes or sudden contributions of meteoric water due to flash-flood events.

The δ18O and δD values of condensation water collected from non-colonized surfaces are -5.4‰ [-5.9 to -4.5 ‰] and –28.4‰ [-32.9 to -21.3 ‰], respectively. This isotope composition is similar to the contemporary infiltration water, which suggests that condensation mostly comes from autochthonous vapour generated from in-cave waters. The Actinobacteria mats quickly absorb the condensation water and it is then retained during long periods on the rock surface. Thus, in the case of microbial induced deposits like moonmilk, condensate water becomes a reservoir of interstitial water exposed to isotopes fractionation linked to the microbial metabolism processes. Indeed, the δ18O and δD values of this interstitial water correlate linearly with the rest of the in-cave waters but show a distinctive composition with higher δ18O and δD values compared to the infiltration water and condensation droplets; -3.6‰ [-4.4 to -2.0 ‰] and –18.9‰ [-27.2 to -10.8 ‰], respectively. These findings lead to exploring the potential use of water isotopes as a tool for indirectly assessing microbial activity and its role in the water balances in underground ecosystems.

Research funded by PID2019-110603RB-I00 – SUBSYST and PID2020-114978GB-I00 projects

How to cite: Fernandez-Cortes, A., Martin-Pozas, T., Cuezva, S., Gazquez, F., Benavente, D., Cañaveras, J. C., Saiz-Jimenez, C., and Sanchez-Moral, S.: Isotopic tracking of condensation, infiltration and interstitial water to detect microbial activity in caves, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16065, https://doi.org/10.5194/egusphere-egu23-16065, 2023.

EGU23-16235 | ECS | Orals | BG2.1 | Highlight

Isotope biogeochemistry of the carbon-iron-sulfur cycle in a temperate coastal peatland after flooding by brackish seawater 

Rhodelyn Saban, Michael Ernest Boettcher, Anna Kathrina Jenner, Sara Elizabeth Anthony, Gerald Juransinski, Catia Ehlert von Ahn, Patricia Roeser, and Iris Schmiedinger

Soils from a coastal peatland (Drammendorf,  southern Baltic Sea) were investigated for the biogeochemical impact of flooding with brackish seawater. The peatland was rewetted in late 2019 through the partial removal of a dyke and brackish water with high sulfate concentration from a lagoon (Kubitzer Bodden) allowed to intrude into the peatland. Soil cores were retrieved about 2 and 3 years after the initial rewetting event. Pore waters were extracted from soil cores using rhizons and samples were analyzed besides physical parameters for major ions, nutrients, water stable isotopes, dissolved inorganic carbon (DIC) concentrations, and stable isotopes in C and S species. Solid phase samples were analyzed for contents of CNS and acid-extractable metal and nutrient species, and the stable isotope composition of acid-volatile sulfide (AVS), chromium-reducible sulfide (CRS, pyrite).Results from the post-event campaigns are compared with pre-flooding conditions. Poree water generally showed a trend towards freshening with depth as remains from the pre-flooding conditions. . Different sites are furthermore characterized by different amounts of diagenetically released dissolved inorganic carbon (DIC). A mixing evaluation of ẟ13C-DIC signatures together with major ion concentrations reveals potential DIC sources, like organic matter/methane oxidation, carbonate dissolution and mixing with seawater-derived DIC. DIC from the dissolution of minor soil carbonates may lead to a relative enrichment of 13C in DIC. Brackish water intrusion and cation exchange are reflected by the downward gradients in pore water compositions, with Na and Mg decreasing and Ca increasing with depth. Soil organic carbon is dominating with inorganic carbon being a minor fraction in most parts. Dissolved pore water sulfate and high total sulfur in the top soils with decrease downward trends further reflect the importance of post-event enhanced sulfur cycling leading to characteristic sulfur isotope signatures. AVS is depleted in the top soils with highest contents at about 5 cmbsf. Pyrite sulfur dominates and show different enrichment zones with the sediment columns. Contents in CRS contents covary with TOC, indicating that the benthic diagenetic system is controlled by organic matter availability, as in normal marine sediments.  The study demonstrates the role of electron acceptor availability for benthic carbon cycling, and the kinetics of biogeochemical interactions upon oxidation of reduced carbon, mineral authigenesis/dissolution, and ion exchange processes. The results of implications for coastal processes in the humid climate zone during times of increasing seawater level rise.

 

 

How to cite: Saban, R., Boettcher, M. E., Jenner, A. K., Anthony, S. E., Juransinski, G., Ehlert von Ahn, C., Roeser, P., and Schmiedinger, I.: Isotope biogeochemistry of the carbon-iron-sulfur cycle in a temperate coastal peatland after flooding by brackish seawater, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16235, https://doi.org/10.5194/egusphere-egu23-16235, 2023.

EGU23-16361 | ECS | Posters on site | BG2.1

Comparison of two isotope-based methods to quantify nitrification rates in estuaries 

Vanessa Russnak, Sophie Kache, Maren Voss, and Kirstin Dähnke

Estuaries are important biogeochemical reactors that can remove dissolved inorganic nitrogen (DIN, mostly nitrate) from the water column, but can also generate nitrate via remineralization and subsequent nitrification of organic matter in the water column. To assess this regeneration of nitrate, an important nutrient source for phytoplankton that contributes to eutrophication, various isotope-based laboratory methods are in use.

In this study, we compare two commonly used stable-isotope-based techniques to measure nitrification in estuarine water, the isotope dilution method and the addition of 15N-ammonium. Both measure the isotope enrichment in nitrate but have drastically different incubation times. We apply both methods in the estuary of the Elbe River and evaluate the drawbacks and advantages of each method to develop application recommendations.

Our results indicate that nitrification measurements using isotope dilution are less variable between stations, but suggest that rates are overestimated at high phytoplankton activity. On the counter side, the addition of 15N-ammonium as a tracer apparently overestimates nitrification in heterotrophic settings, probably because substrate addition stimulates nitrification. The adequate measurement technique must this be carefully chosen depending on the selected study site.

Funding information  - This study has been carried out and was financially supported by the BMBF “Blue-Estuaries” project (grant no. 03F0864C)

How to cite: Russnak, V., Kache, S., Voss, M., and Dähnke, K.: Comparison of two isotope-based methods to quantify nitrification rates in estuaries, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16361, https://doi.org/10.5194/egusphere-egu23-16361, 2023.

EGU23-16727 | ECS | Posters on site | BG2.1

The isotope effect of benthic N removal in two Swiss lakes 

Tim J. Paulus, Alessandra Mazzoli, Claudia Frey, Jakob Zopfi, Cameron Callbeck, and Moritz F. Lehmann

Aquatic sediments play a critical role in moderating the availability of fixed nitrogen (N) in the biosphere. Microbial N cycling processes, such as denitrification and anammox, contribute to fixed‑N removal as N2 gas from lakes and the ocean. N‑isotopic measurements of dissolved inorganic N (e.g., nitrate (NO3-)) can provide insights into the different sources, sinks, and pathways of N, if the associated N isotope signatures/effects are constrained. While substantial work has been done to resolve N‑loss using microbial metagenomic‑based approaches and rate measurements, how nitrogen‑loss processes imprint natural‑abundance isotopes of 15N and 18O of NO3- remains largely understudied in freshwater lake sediments. Current marine evidence suggests that water column denitrification involves high NO3- isotope effects (>20‰). In contrast, the marine NO3- isotope effect of sedimentary denitrification is suppressed at the level of the sediment‑water interface (apparent N/O isotope effect, εapp <5‰). How anammox affects εapp in either marine or freshwater systems, is completely unknown. This study aims to achieve a deeper understanding of NO3- N and O isotope fractionation during benthic N transformation and sedimentary N‑loss (including anammox), and its ultimate expression in the water column of freshwater lakes. We also investigate how εapp values may vary with environmental conditions (e.g., trophic state) that affect the reactivity and amount of organic matter in the sediments, as well as the balance between benthic N‑cycle reactions.

The two study sites Lake Baldegg (eutrophic) and Sarnen (oligotrophic), were chosen because of their contrasting trophic states. We conducted a suite of experiments with sediment cores collected at different times of the year to assess the sedimentary εapp in these two lakes. More specifically, we carried out whole‑core incubations under oxic/anoxic conditions and examined the change 15N/14N and 18O/16O of NO3- with net NO3- depletion in the overlying water. We integrated natural‑abundance N and O isotope measurements with 15N‑label based N transformation‑rate measurements, to understand how the phenology and differential combination of the different N transformation pathways may modulate εapp. We demonstrate that nitrification, DNRA, denitrification, anammox and organic matter remineralization overlap spatially in the sediments of Lake Sarnen. In contrast, these processes are, in parts, spatially decoupled in Lake Baldegg. Moreover, the relative importance of anammox versus denitrification is significantly greater in Lake Baldegg. In both lakes the net N isotope effect of sedimentary NO3- consumption is strongly underexpressed at the ecosystem level, with NO3-‑N εapp values systematically below 4‰. In Lake Sarnen the NO3- N‑vs.‑O isotope signature followed a 1:1 trend, whereas in Lake Baldegg a systematically higher ratio was observed. This suggests that, while in Lake Sarnen, the NO3- N and O isotope signatures are dominated by NO3- reduction, NO3- regeneration (e.g., by nitrification or anammox) overprints the NO3- isotopic signature of net denitrification under the more eutrophic conditions in Lake Baldegg.

How to cite: Paulus, T. J., Mazzoli, A., Frey, C., Zopfi, J., Callbeck, C., and Lehmann, M. F.: The isotope effect of benthic N removal in two Swiss lakes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16727, https://doi.org/10.5194/egusphere-egu23-16727, 2023.

EGU23-144 | ECS | Posters on site | BG2.2

Calibration of an optical methane clumped isotope thermometer 

Ivan Prokhorov, Béla Tuzson, Nico Kueter, Malavika Sivan, Maria Elena Popa, Thomas Röckmann, Lukas Emmenegger, Stefano M. Bernasconi, and Joachim Mohn

Methane clumped isotope thermometry relies on accurate measurements of relative abundances of the doubly-substituted isotopologues 12CH2D2 and 13CH3D. Calibration of the thermometer requires, regardless of the applied technique, i.e., laser absorption spectroscopy or high-resolution mass spectrometry, routine preparation of thermally re-equilibrated samples spanning the temperature and bulk isotopic composition (δ13C-, δD-CH4) range of the target applications.

Here we present a practical method for methane isotopologue re-equilibration over activated γ-Al2O3. We demonstrate complete and reproducible re-equilibration of clumped isotope signatures with minimal alteration of the bulk isotope composition, almost complete sample recovery, and no detectable formation of decomposition products. Samples spanning a range in δD-CH4 of 100 ‰ were equilibrated between 100 °C and 500 °C and used to calibrate a high-resolution quantum cascade laser absorption spectrometer. In addition, we report on a comparison between the spectroscopic measurements carried out at Empa and an independently calibrated high-resolution mass spectrometric technique using a Thermo MAT253 Ultra at IMAU, Utrecht University.

This study is supported by the European Commission under the Horizon 2020 – Research and Innovation Framework Programme, H2020-INFRAIA-2020-1 (grant no. 101008004) and the Swiss National Science Foundation project no. 200021_200977.

How to cite: Prokhorov, I., Tuzson, B., Kueter, N., Sivan, M., Popa, M. E., Röckmann, T., Emmenegger, L., Bernasconi, S. M., and Mohn, J.: Calibration of an optical methane clumped isotope thermometer, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-144, https://doi.org/10.5194/egusphere-egu23-144, 2023.

EGU23-1424 | Posters on site | BG2.2

Satellite-based dry-wet seasonal changes of OCS surface budgets over the Amazon rainforests 

Lin Tan, King-Fai Li, Xun Jiang, Le Kuai, and Danie Liang

Carbonyl sulfide (OCS) is the most dominant sulfur-containing species in the atmosphere and is an important tracer of the terrestrial gross primary productivity as it is involved only in photosynthesis. Biomass burning and terrestrial uptakes by plants and soil is the primary terrestrial source and sink of OCS, respectively.  The Amazon basin alone accounts for 10% of the global biomass burning emission and 33% of the global plant/soil uptake. However, both terms are sensitive to water stress, heat stress, and the associated wildfires in the dry seasons. Here, we estimate the dry-wet seasonal difference of the terrestrial OCS budget over the Amazon region by constraining the NCAR MOZART4 chemistry-transport model with the mid-tropospheric OCS abundances retrieved from NASA’s Thermal Emission Spectrometer (TES) measurements during 2004 and 2012.  Our perturbative calculations show that biomass-burning emissions that are predominant in the south rim of the Amazon have more influence on the mid-tropospheric OCS over the southeast subtropical Amazon. In comparison, the plant/soil uptakes that are predominant in the tropical Amazon have more influence over the northwest tropical Amazon.  This dipole spatial pattern helps distinguish the mid-tropospheric OCS seasonal variability due to biomass-burning emissions and plant/soil uptakes.

How to cite: Tan, L., Li, K.-F., Jiang, X., Kuai, L., and Liang, D.: Satellite-based dry-wet seasonal changes of OCS surface budgets over the Amazon rainforests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1424, https://doi.org/10.5194/egusphere-egu23-1424, 2023.

Combining measurements, modeling and machine learning to improve N2O accounting for sustainable agricultural development in sub-Saharan Africa

 

  • Ouma1,2, E. Harris1, M. Barthel2, J. Six2, A. Otinga3, R. Njoroge3, F. Perez-Cruz1, S. Leitner4

 

1 Swiss Data Science Centre, ETH Zurich, 8092 Zurich, Switzerland

2 Department of Environmental Systems Science, ETH Zurich, Switzerland

3 Department of Soil Science, University of Eldoret, Eldoret, Kenya

4 International Institute of Livestock Research (ILRI), Nairobi, Kenya

 

Sub-Saharan Africa continues to grapple with food insecurity due to low crop yields. While an increase in synthetic fertilisers could potentially increase agricultural productivity in the region, it would lead to an increase in emissions of nitrous oxide (N2O). Moreover, in this region, the lack of quantification of parameters and documentation of the processes relevant to N2O emissions have hampered the adoption of climate-smart agricultural practices and advancement of N2O inventories. This study aims to conduct the first online measurements of N2O fluxes and isotopic composition from agricultural soils in Uasin Gishu County, Kenya, using the TREX-QCLAS system: quantum cascade laser absorption spectrometer (QCLAS) coupled to a preconcentration unit-TRace gas EXtractor (TREX). The isotopic measurements obtained will be useful in the inference of N2O production and consumption rates for different pathways and will improve understanding of the key drivers of variability in tropical cropland N2O fluxes. Further, a collation and analysis of available N2O flux and isotope data along with campaign measurements and data science approaches will enhance the potential to predict future emissions and promote the development of targeted mitigation strategies.

 

A pilot phase of initial flux measurements set at the plant research station in Eschikon, Switzerland in early 2023 using the TREX-QCLAS system coupled with automated dynamic chambers optimised for continuous unattended N2O flux measurements will be conducted before deployment in Kenya. Using clover and grass plots, we aim to understand N2O fluxes and drivers in a simple system. N2O measurements will be based on a three-stage calibration protocol (preconcentrated ambient air, preconcentrated compressed air, and calibration of the instrumental concentration dependence using progressive dilution of the anchor standard) followed by measurement of chamber air. Preliminary results of automated quality control and data analysis procedures will be key to ensure success of the instrumental deployment in Kenya in late 2023.

 

References:

  • Harris, E., Diaz-Pines, E., Stoll, E., Schloter, M., Schulz, S., Duffner, C., Li, K., Moore, K. L., Ingrisch, J., Reinthaler, D., Zechmeister-Boltenstern, S., Glatzel, S., Brüggemann, N., & Bahn, M. (2021). Denitrifying pathways dominate nitrous oxide emissions from managed grassland during drought and rewetting. Science advances, 7(6), eabb7118. https://doi.org/10.1126/sciadv.abb7118

 

  • Ibraim, E., Denk, T., Wolf, B., Barthel, M., Gasche, R., Wanek, W., … Mohn, J. (2020). Denitrification is the main nitrous oxide source process in grassland soils according to quasi‐continuous isotopocule analysis and biogeochemical modeling. Global Biogeochemical Cycles, 34(6), e2019GB006505 (19 pp.). https://doi.org/10.1029/2019GB006505

 

How to cite: Ouma, T.: Combining measurements, modeling and machine learning to improve N2O accounting for sustainable agricultural development in sub-Saharan Africa, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1731, https://doi.org/10.5194/egusphere-egu23-1731, 2023.

EGU23-1754 | ECS | Orals | BG2.2

Stratospheric observations of carbonyl sulfide using AirCore and LISA 

Alessandro Zanchetta, Steven van Heuven, Michel Ramonet, Thomas Laemmel, Jin Ma, Maarten Krol, and Huilin Chen

Carbonyl sulfide (COS) is a long-lived sulfur compound present in the atmosphere with an average mole fraction of around 450-500 ppt, and has been suggested as a potential tracer to partition gross primary production (GPP) and net ecosystem exchange (NEE) in plants’ photosynthesis, possibly by satellite observations. However, its sources and sinks have not been fully understood, and remote sensing observations of COS still require validation and to be linked with a reference measurement scale, e.g., NOAA’s. In this work, we have made vertical profiles of COS mole fractions using AirCore at Trainou, France (47°58' N, 2°6' E), in June 2019, and at Kiruna, Sweden (67°53' N, 21°04' E) in August 2021, using both AirCore and a new version of lightweight stratospheric air (LISA) sampler. Besides COS, simultaneous measurements of CO2, CO, CH4 and N2O have also been made. These results will be compared with COS simulations from the TM5-4DVAR modeling system to get a better understanding of the behavior of this species in the stratosphere, i.e., the sources and the sinks COS, as well as vertical structures due to atmospheric transport. These will be helpful to improve our understanding of the budget and the variabilities of COS in the stratosphere, and advance the use of remote sensing observations of COS from satellite and ground-based spectrometers to study the carbon cycle.  

How to cite: Zanchetta, A., van Heuven, S., Ramonet, M., Laemmel, T., Ma, J., Krol, M., and Chen, H.: Stratospheric observations of carbonyl sulfide using AirCore and LISA, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1754, https://doi.org/10.5194/egusphere-egu23-1754, 2023.

Isotopocules of the greenhouse gas nitrous oxide (N2O), i.e. δ18O, average δ15N (δ15Nbulk), and 15N site preference (SP) values were used to distinguish between N2O production pathways in soil. However, as many N2O production pathways coexist and N2O can be reduced to N2, it is not possible to distinguish pathways based only on the natural abundance of N2O. This applies especially to nitrification and fungal denitrification, where the specific high SP values overlap. Combining 15N tracer approaches and natural abundance approaches (especially using SP values) could serve to disentangle such pathways, but with the disadvantage that both approaches have to be carried out as parallel experiments.

With this contribution, we present an experimental concept based on the theory, that low level labelling with 15N of N2O precursors may allow both, a clear distinction of nitrate or ammonium (NO3- or NH4+, respectively) derived N2O fluxes by 15N tracing, and the use of SP values of N2O as additional constraint. This could potentially expand possibilities to evaluate and validate current natural abundance isotopocule mapping approaches.

We will present first results of three experiments to investigate the impact of low labelled precursors on SP values of N2O produced. Each experiment included treatments with unlabeled and low labelled 15N precursors to test if low labelling with 15N affects N2O isotopocules. In one incubation experiment (i) various levels of 15N labelling of NO3- (between 0.6 and 5 at% 15N) were used for incubations with Pseudomonas aureofaciens. In another experiment (ii) two pure bacterial (P. aureofaciens and Paracoccus denitrificans) and one pure fungal culture (Fusarium oxysporum) known to be capable of reducing NO3- or NO2-, respectively, were used. In all experiments, isotopocules of N2O were unaffected by N2O reduction as this reduction step could be excluded with selected species. To further investigate isotopocules of N2O affected by co-occuring processes as well as N2O reduction a third incubation experiment with two repacked soils was conducted. For this approach, nitrification and/or denitrification was induced by applying NH4SO4 and KNO3 as N2O precursors, either unlabeled in one treatment or with 15N labelled KNO3 (max. 1.1 at% 15N) in another treatment, both under dry (40% water filled pore space (WFPS)) or wet (80% WFPS) soil conditions.

Based on the results presented, we will be able to give an outlook whether this method can be used to distinguish between nitrification and fungal denitrification.

How to cite: Rohe, L. and Well, R.: Combining low level labelling with 15N and 15N site preference to distinguish N2O production by nitrification and fungal denitrification, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4990, https://doi.org/10.5194/egusphere-egu23-4990, 2023.

EGU23-5286 | ECS | Orals | BG2.2

Carbon and water fluxes of the boreal evergreen needleleaf forest biome constrained by assimilating ecosystem carbonyl sulfide flux observations 

Camille Abadie, Fabienne Maignan, Marine Remaud, Kukka-Maaria Kohonen, Wu Sun, Linda Kooijmans, Timo Vesala, Ulli Seibt, Nina Raoult, Vladislav Bastrikov, Sauveur Belviso, and Philippe Peylin

Boreal forests absorb a significant amount of atmospheric CO2 through gross primary production (GPP), representing about 20% of the global GPP. However, direct observations of GPP over the whole boreal region are not available as plant photosynthetic rate cannot be measured at scales larger than the leaf scale. At large scales, Land Surface Models (LSMs) can simulate GPP but the lack of direct GPP measurements makes it challenging to evaluate and improve the GPP representation in LSMs. In addition, boreal forests are highly sensitive to environmental changes, impacting gas exchanges and leading to high uncertainties in GPP estimates simulated by LSMs or obtained from data driven methods. Carbonyl sulfide (COS) has emerged as a promising proxy to infer GPP estimates or to better constrain GPP representation in LSMs. Because COS is absorbed by vegetation following the same diffusion pathway as CO2 during photosynthesis and not emitted back to the atmosphere, implementing a mechanistic representation of vegetation COS uptake in LSMs allows using COS data to constrain GPP representation. In this study, we performed ecosystem COS flux and GPP assimilations to constrain the COS and GPP related parameters in the ORCHIDEE LSM. We focused on Hyytiälä forest, where the longest time-series of ecosystem COS flux measurements was reported. We found that assimilating ecosystem COS fluxes increases the estimated net ecosystem COS uptake by 14%. However, a persistent underestimation of the ecosystem COS flux seasonal amplitude after data assimilation points towards structural errors in the COS model, possibly related to COS internal conductance representation. In comparison with an assimilation of GPP only, adding ecosystem COS flux assimilation leads to a stronger reduction in the stomatal conductance, highlighting the potential of COS to inform stomatal diffusion. Consequently, including COS data in the assimilations also impacts the resulting latent heat flux and water use efficiency. Finally, we scaled up this assimilation framework to the boreal region and found that the joint assimilation of COS and GPP fluxes increased the modeled vegetation COS uptake up to 18%, but not the GPP budget. This contrasts with previous inversion studies that simultaneously increase vegetation COS uptake and GPP budgets based on a linear relationship relating the two. 

How to cite: Abadie, C., Maignan, F., Remaud, M., Kohonen, K.-M., Sun, W., Kooijmans, L., Vesala, T., Seibt, U., Raoult, N., Bastrikov, V., Belviso, S., and Peylin, P.: Carbon and water fluxes of the boreal evergreen needleleaf forest biome constrained by assimilating ecosystem carbonyl sulfide flux observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5286, https://doi.org/10.5194/egusphere-egu23-5286, 2023.

EGU23-5713 | ECS | Orals | BG2.2

Sources of oceanic carbonyl sulfide revealed by sulfur isotopes measurements 

Chen Davidson, Yasmin Avidani, Alon Angert, Sinikka Lennartz, and Alon Amrani

Carbonyl sulfide (COS) is the major long-lived sulfur gas in the troposphere, and an important precursor for stratospheric sulfate aerosols, which increases earth’s albedo. The main sink of COS is the uptake by terrestrial plants, in a similar pathway to CO2. Therefore, COS is used as a promising proxy for CO2 removal by terrestrial plants (gross primary production, GPP), which regulates the earth’s climate. Currently, COS budget estimates have large uncertainties associated with the magnitude of COS sources and sinks. The COS ocean-atmosphere flux is the largest natural source of tropospheric COS, however, its magnitude is at the heart of a scientific debate with estimates ranging between  200 to 800 Ggr S Yr-1 [1-2].

Sulfur isotopes measurements (34S/32S; δ34S) are recently used in an isotopic mass-balance to constrain the COS budget, assuming each end-member has a unique isotopic signature [3]. However, in our previous work [3], we estimated the isotopic signature of the ocean-atmosphere COS flux, based on limited samples from the Mediterranean and Red Seas, which may not be representative of the oceans. In the current work, we present measurements of photochemistry experiments and natural samples from the Atlantic Ocean, sampled during dawn, afternoon, and sunset. Atlantic Ocean samples that were taken during dawn (min COS concentrations) show δ34S value of 14±2‰ (n=8, one outlier with δ34S value of 19.2‰ was excluded). However, samples taken during the afternoon (max concentration) show heavier δ34S values of 18±1‰ (n=6).  This significant difference in δ34S values between dawn and afternoon (P-value 0.0003) indicates that COS “dark production” is associated with an isotopic fractionation that produces isotopically lighter COS, supporting the hypothesis that COS “dark production” is related to biotic processes. While COS photoproduction is associated with heavier isotopic values, which we assume are closer to the δ34S value of its biogenic source. This assumption is also supported by our photochemistry experiments, which indicate a small isotopic fractionation of COS photoproduction from cysteine (≤1‰). The isotopic signatures we present here will be used to better understand the main processes controlling oceanic COS production, and better constrain the ocean-atmosphere COS flux.   

 

[1] Lennartz, Sinikka T., et al. "Marine carbonyl sulfide (OCS) and carbon disulfide (CS2): a compilation of measurements in seawater and the marine boundary layer." Earth system science data 12.1 (2020): 591-609.

[2] Berry, Joe, et al. "A coupled model of the global cycles of carbonyl sulfide and CO2: A possible new window on the carbon cycle." Journal of Geophysical Research: Biogeosciences 118.2 (2013): 842-852.

[3] Davidson, Chen, Alon Amrani, and Alon Angert. "Tropospheric carbonyl sulfide mass balance based on direct measurements of sulfur isotopes." Proceedings of the National Academy of Sciences 118.6 (2021): e2020060118.

How to cite: Davidson, C., Avidani, Y., Angert, A., Lennartz, S., and Amrani, A.: Sources of oceanic carbonyl sulfide revealed by sulfur isotopes measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5713, https://doi.org/10.5194/egusphere-egu23-5713, 2023.

EGU23-6222 | ECS | Posters on site | BG2.2

The formation and transport of nitrogen-containing species in aerosols over central mountain area of Taiwan using isotope analysis 

Ming-Hao Huang, Ting-Yu Chen, Haojia Ren, and Hui-Ming Hung

Particulate matter (PM) is one major air pollutant that affects human health and the radiation balance of the earth. Thus, it is essential to identify the sources of air pollutants to provide feasible control strategies. In this study, we investigated the size-dependent 15N and 18O isotope ratio of N-containing species in aerosols to specify their sources, transport, and formation processes. Aerosol samples of different size ranges were collected using a micro-orifice uniform deposit impactor (MOUDI) on a half-day basis over Xitou Experimental Forest of National Taiwan University (23.40°N, 120.47°E, 1178 m a.s.l.) site at the valley southwest to the central Metropolitan of Taiwan in April 2021. Due to its location and topography, Xitou is downstream of the local circulation, which is dominated by the land-sea breeze and mountain-valley wind and brings the pollutants from the coastal industrial and agricultural activities to the forest during the daytime. Therefore, the samples collected at Xitou are a mixture of complex information. Chemical functional groups measurement was performed using Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR) technique beforehand to provide a grasp of the concentration-size distribution for both nitrate and ammonium as a reference to ensure sufficient nitrogen requirement for further isotope analysis at gas chromatography–isotope ratio mass spectrometer (GC-IRMS). The daily average concentration is 3.78±1.82 and 2.47±2.47 ug/m3 for ammonium (NH4+) and nitrate (NO3), respectively. The concentration during daytime is higher than at nighttime by a factor of 1.3-1.8. The result suggests that pollutants brought by the sea breeze windward contribute to nitrogen-containing aerosols. During a persistent 24-hour weak wind fog event, a significant concentration decreases for both substances (NH4+: 5.34 to 2.12 ug/m3 and NO3: 4.62 to 0.56 ug/m3) in PM10, likely due to sedimentation. The observed δ15N in NO3 increasing with diameter suggests NO3 at larger particles formed at the upper stream and NO3 at finer particles formed locally. On the other hand, δ18O in nitrate shows a similar trend which might be the contribution of RO2 as the oxidant locally. As NH4+ in aerosols is contributed by ammonia partitioning, δ15N-NH4+ only reflects the fractionation process during phase change and initial emission. The size-dependent trend of δ15N-NH4+ shows similar behavior to our previous study in December 2018 and reflects the time points of partitioning. Furthermore, the quantitative analysis of the transport and formation processes based on the size-dependent isotope will be deconvoluted to understand the partitioning of N-containing species in aerosols, which would be necessary for the pollution control strategy and their impact evaluation.

How to cite: Huang, M.-H., Chen, T.-Y., Ren, H., and Hung, H.-M.: The formation and transport of nitrogen-containing species in aerosols over central mountain area of Taiwan using isotope analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6222, https://doi.org/10.5194/egusphere-egu23-6222, 2023.

EGU23-6260 | Posters on site | BG2.2

Tracking Biogenic Carbon in Liquid Fuel Blends using Conventional Mass Spectrometry and Infrared Spectroscopy 

Scott Herndon, David Nelson, Sophie Lehmann, Alejandro Heredia-Langner, James Moran, and J. Timothy Bays

This work demonstrates the analytical basis for an IR (isotope ratio) laser measurement system with the potential to perform routine quantification of biogenic carbon content in liquid fuel products at working refineries. We will present the performance potential for routine quantification for mixtures of C3 and C4 biogenic carbon sources mixed with fossil feedstock.  We will show the progress toward an operational on-line portable monitor. Initial work employed a predilution stage that required challenging transfer techniques to suppress fractionation.  More recent work has explored the potential for the IR based apparatus to directly quantify stable isotopologues that are isobaric in IRMS (isotope ratio mass spectrometry) instruments. The IR system results for 13CO2/12CO2 compare favorably with gold-standard IRMS. 

How to cite: Herndon, S., Nelson, D., Lehmann, S., Heredia-Langner, A., Moran, J., and Bays, J. T.: Tracking Biogenic Carbon in Liquid Fuel Blends using Conventional Mass Spectrometry and Infrared Spectroscopy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6260, https://doi.org/10.5194/egusphere-egu23-6260, 2023.

EGU23-6847 | ECS | Posters on site | BG2.2

Isotopic fractionation of sulfur during COS hydrolysis 

Yasmin Avidani, Chen Davidson, Alon Angert, and Alon Amrani

Carbonyl Sulfide (COS) is the most abundant sulfur-containing gas in the atmosphere, and it is used as a proxy for terrestrial gross primary productivity (GPP). There are uncertainties in the COS fluxes estimations that limit this approach. Oceans are the major source of COS to the atmosphere. In the oceans, the COS is produced by photochemical reactions and "dark production", whose mechanism is not well understood. Hydrolysis is the major process that removes COS from the ocean's surface. Identifying the sulfur isotope values (δ34S) and the isotopic fractionation (e) associated with these major sources and sinks could decrease the uncertainties in the fluxes, based on an improved COS global model with an isotopic mass balance [1]. In the current study, we aim to determine the e  during the hydrolysis process of COS (eh).  We use a purge and trap system coupled to a GC/MC-ICPMS to measure δ34S values during hydrolysis under different pH, salinity (S), and temperature, representing various oceanic conditions. We calculate from our δ34S and COS concentration measurements a eh of −2.6 ± 0.3‰ in natural seawater from the Gulf of Aqaba (pH 8.2, 22 , S=41‰). Using an artificial solution at similar pH and temperature conditions (pH 8.0, 22 , S=0.2‰) we found eh of −2.3 ± 0.2‰, hence, salinity has no significant effect on the fractionation. Using the same artificial solution at 4   we found eh  of −3.9 ± 0.2‰, thus fractionation increases with decreasing temperatures, as can be expected from theory. We will also report the effect of acidity on eh from experiments in pH of 4 and 9 (at 22 ). This information on the eh will help us to understand the contribution of COS hydrolysis to the oceanic source and in the future to establish an isotope mass balance model to decrease the uncertainty of this major source.

[1] Davidson, Chen, Alon Amrani, and Alon Angert. "Tropospheric carbonyl sulfide mass balance based on direct measurements of sulfur isotopes." Proceedings of the National Academy of Sciences 118.6 (2021): e2020060118. 

How to cite: Avidani, Y., Davidson, C., Angert, A., and Amrani, A.: Isotopic fractionation of sulfur during COS hydrolysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6847, https://doi.org/10.5194/egusphere-egu23-6847, 2023.

EGU23-6955 | ECS | Posters on site | BG2.2

Quantifying the COS fluxes from plane, willow, beach and oak litter 

Florian Kitz, Herbert Wachter, and Georg Wohlfahrt

Flux partitioning, the quantification of photosynthesis and respiration, is a major uncertainty in modelling the carbon cycle and in times when robust models are needed to assess future global changes a persistent problem. A promising new approach is to derive gross primary production (GPP) from measurements of the carbonyl sulfide (COS) flux, the most abundant sulfur-containing trace gas in the atmosphere, with a mean concentration of about 500 pptv in the troposphere. The method is based on the observation that COS and CO2 enter the leaf via a similar pathway and are processed by the same enzyme (carbonic anhydrase), in case of COS a unidirectional process, allowing researchers to use COS uptake as a proxy for the gross CO2 uptake by plants. A prerequisite for using COS as a proxy for photosynthesis is a robust estimation of all non-living-leaf sources and sinks in an ecosystem. One major uncertainty in this regard is the contribution of soils and their respective litter layers to the overall ecosystem COS flux.

COS and CO2 fluxes from litter were measured in real-time using a quantum cascade laser (QCL). The plant litter from four different broadleaf tree species (plane, willow, beech and oak), collected a maximum of one hour before measurements started in the lab (to retain in situ moisture and the microbial biome), was measured under alternating dark and light (UV-A) conditions.

COS litter fluxes varied between the tree species, with plane primarily emitting COS, beech consuming COS and oak and willow being on average neutral (willow with a huge variance). COS litter fluxes within a species seem to correlate with litter moisture. The COS flux was ranging between -4 and 4 pmol kg DW-1 s-1, which is relevant in magnitude compared to the overall ecosystem COS flux and shouldn’t be neglected in future assessments of the global COS budget. 

How to cite: Kitz, F., Wachter, H., and Wohlfahrt, G.: Quantifying the COS fluxes from plane, willow, beach and oak litter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6955, https://doi.org/10.5194/egusphere-egu23-6955, 2023.

EGU23-7308 | ECS | Posters on site | BG2.2

First principles model of isotopic fractionation in formaldehyde photolysis: wavelength and pressure dependence 

Luisa Pennacchio, Andreas E. Hillers-Bendtsen, Kurt V. Mikkelsen, and Matthew S. Johnson

Experimental studies show large isotope-dependent effects in the photolysis rates of formaldehyde isotopologues, that are both wavelength and pressure dependent. These effects are on the order of 10-20% for 13C and 18O (L. Feilberg et. al, J. Phys. Chem. A, 109, 8314-8319, 2004), and 60% for CHDO (E. J. K Nilsson et. al, ACP, 14, 551–558, 2014). We have made a model of the elementary processes involved in the photodissociation including unimolecular dissociation, collisional quenching and crossing between excited state surfaces. Computational chemistry is used to characterize some of these processes. The model is validated by comparison to all existing experimental data and is then used to make predictions about the isotopic fractionation in additional isotopicules (and for conditions not yet addressed by experiment) including fractionation in clumped molecules. The following isotopologues of formaldehyde have been investigated; HCHO, DCHO, DCDO, D13CHO, H13CHO, HCH17O, HCH18O, H13CH17O and H13CH18O. Rice–Ramsperger–Kassel–Marcus (RRKM) theory was used to calculate the rates for decomposition of the S0, S1 and T1 states with CCSD(T)/aug-cc-pVTZ, ωB97X-D/aug-cc-pVTZ and CASPT2/aug-cc-pVTZ levels of theory. Furthermore, the rates and likelihood of intersystem crossing were investigated by including the spin-orbit coupling between the excited states. The model was able to replicate the experimental pressure trends accurately, however, the kinetic isotope effect was one order of magnitude too small for the non-deuterated isotopologues. We predict a large clumped isotope anomaly in 13C18O produced by formaldehyde photolysis.

How to cite: Pennacchio, L., E. Hillers-Bendtsen, A., V. Mikkelsen, K., and S. Johnson, M.: First principles model of isotopic fractionation in formaldehyde photolysis: wavelength and pressure dependence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7308, https://doi.org/10.5194/egusphere-egu23-7308, 2023.

EGU23-9030 | Orals | BG2.2 | Highlight

ISAMO (Iron Salt Atmospheric Methane Oxidation) 

Matthew S. Johnson, Maarten M. J. W. van Herpen, Berend v/d Kraats, Qinyi Li, Alfonso Saiz-Lopez, Jesper B. Liisberg, Luisa Pennacchio, and Thomas Röckmann

Methane is a well-mixed greenhouse gas responsible for >1/3 of global warming since pre-industrial times whose atmospheric burden continues to increase with a new record set in 2022. Active chlorine in the atmosphere is poorly constrained and so is its role in the oxidation of methane. This uncertainty propagates into methane source budgets through isotope-constrained top-down models, in which the observed abundance of 13C in tropospheric methane (commonly expressed as δ13C-CH4) is used to constrain the sources of methane using their characteristic δ13C-CH4 values. These models need to account for the change in the observed δ13C-CH4 by the Cl and OH sinks, which shift the observed isotope towards higher δ13C-CH4 values of fossil fuel sources, and away from 13C depleted biological sources. The ISAMO project focuses on the hypothesis that Cl atoms are produced naturally by the action of sunlight on particles containing iron and chloride and these chlorine atoms oxidize atmospheric methane. To study this, we use the sensitive and selective indirect quantification of the concentration of atomic Cl through the strong carbon kinetic isotope effect (KIE) in the CH4 + Cl reaction, which leaves the remaining CH4 enriched in 13C, and producing extremely 13C-depleted CO. We will present field and laboratory observations and global modelling, including CO isotope measurement from flasks samples across the North Atlantic. We show how this mechanism affects 13C depletion in atmospheric CO and how the corresponding 13C enrichment in CH4 affects global methane emission estimates.

How to cite: Johnson, M. S., van Herpen, M. M. J. W., v/d Kraats, B., Li, Q., Saiz-Lopez, A., Liisberg, J. B., Pennacchio, L., and Röckmann, T.: ISAMO (Iron Salt Atmospheric Methane Oxidation), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9030, https://doi.org/10.5194/egusphere-egu23-9030, 2023.

EGU23-10234 | ECS | Posters on site | BG2.2

Interannual variability and seasonality of carbonyl sulfide fluxes of an Austrian Scots pine forest 

Felix M. Spielmann, Albin Hammerle, Katharina Scholz, and Georg Wohlfahrt

The gross primary productivity (GPP), that is the gross uptake of carbon dioxide (CO2) by plants, cannot be measured on ecosystem level but must be inferred by either applying models or measuring proxies. One of those proxies is the trace gas carbonyl sulfide (COS), which is of particular interest, because it shares a very similar pathway into plant leaves as CO2 and is, contrary to the latter, generally not re-emitted.

Due to the need of expensive and sensitive instrumentation, e.g., quantum cascade lasers, only a limited amount of ecosystem measurements and even fewer long-term studies at this scale have been conducted. Consequently, more data focusing on the seasonality and the interannual variability of COS ecosystem fluxes are needed to understand the relationship of the COS to CO2 uptake, i.e., the leaf relative uptake (LRU), for reliable GPP calculations.

To investigate the impact of environmental changes on the LRU we conducted COS, CO2 and H2O eddy covariance flux (EC) measurements at our newly established forest field site in Mieming (Austria) for the last two years. The field site's dominating tree species is Scots pine (Pinus sylvestris) with Juniper trees (Juniper communis) in the understory.
In addition to the EC measurements, we conducted branch chamber measurements within the crown of the Scots pine, two at the treetop and one within the canopy.

Our EC measurements indicate a strong interannual variability of the COS fluxes. While we observed the highest COS uptake in 2021 during May, the COS uptake in 2022 was higher in the period from June to August. We also observed this pattern for the net CO2 fluxes. The fluxes of COS and CO2 concurrently decreased during the winter month and the forest turned into a net source for CO2, while COS was taken up continuously.

The mean LRU across all branch chamber measurements was 1.67 (-) with the chambers within the canopy generally having lower LRUs (1.39 (-)).

How to cite: Spielmann, F. M., Hammerle, A., Scholz, K., and Wohlfahrt, G.: Interannual variability and seasonality of carbonyl sulfide fluxes of an Austrian Scots pine forest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10234, https://doi.org/10.5194/egusphere-egu23-10234, 2023.

EGU23-10454 | ECS | Posters virtual | BG2.2

Sulfate aerosol formation mechanisms constrained by oxygen and sulfur isotopes at coastal Hong Kong 

Qianjie Chen, Allison Moon, Andrew Schauer, Tao Wang, and Becky Alexander

Sulfate plays a key role in the formation and growth of aerosol particles and cloud droplets in the troposphere and is thus important for air quality and climate. The formation mechanisms of sulfate vary with oxidant levels and environmental conditions and can be partially revealed by its isotopic signatures. Here we measure oxygen (16O, 17O, 18O) and sulfur isotopes (32S, 34S) of the sulfate aerosol samples collected at coastal Hong Kong, downwind of the highly urbanized Pearl River Delta region. Based on ion measurements, most (95%) of the sulfate collected is non-sea-salt sulfate. The δ34S of sulfate is on average 4.0±2.0 ‰ (range 0.7 – 8.0 ‰), at an average sulfur oxidation ratio of 79±9%. The average oxygen-17 excess (Δ17O) is -0.1±0.3 ‰, suggesting an important role of OH / transition metals / reactive halogens. The δ18O of sulfate is on average 4.9±2.1 ‰. The Markov-Chain Monte Carlo model will be used to further constrain sulfate formation mechanisms.

How to cite: Chen, Q., Moon, A., Schauer, A., Wang, T., and Alexander, B.: Sulfate aerosol formation mechanisms constrained by oxygen and sulfur isotopes at coastal Hong Kong, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10454, https://doi.org/10.5194/egusphere-egu23-10454, 2023.

EGU23-11890 | Posters on site | BG2.2

Tracing N2O production pathways in aqueous ecosystems by quasi-simultaneous online analysis of 15N in reactive nitrogen species and gaseous emissions 

Joachim Mohn, Kun Huang, Wolfram Eschenbach, Jing Wei, Damian Hausherr, Claudia Frey, André Kupferschmid, Jens Dyckmans, Adriano Joss, and Moritz F. Lehmann

Natural and engineered nitrogen (N) removal processes in aqueous systems represent important sources of nitrogenous gas emissions, including the potent greenhouse gas nitrous dioxide (N2O). The relevance of microbial and abiotic formation pathways can be assessed using 15N tracing techniques. While 15N-N2O analysis using optical analyzers is straightforward, quantification of 15N fractions in inorganic N compounds, ammonium (NH4+), nitrite (NO2-), and nitrate (NO3-), is typically time-consuming and labor-intensive.

In this study, we developed an automated sample-preparation unit coupled to a membrane-inlet quadrupole mass spectrometer (3n-ASSP-MIMS) for the online quasi-simultaneous analysis of 15N fractions in NH4+, NO2-, and NO3-. The technique was designed and validated for applications at moderate (100 - 200 μmol L-1) to high (2 – 3 mmol L-1) N, as found in sewer systems, wastewater in treatment plants, or eutrophic surface waters, and 15N spiking (f15) between 1 and 33%.

The potential of 3n-ASSP-MIMS was demonstrated in a feasibility study, where the technique, in conjunction with 15N-N2O analyses by FTIR spectroscopy, was applied to pinpoint nitrifier denitrification as the primary N2O formation pathway during partial NH4+ oxidation to NO2- in a lab-scale sequencing batch reactor.

How to cite: Mohn, J., Huang, K., Eschenbach, W., Wei, J., Hausherr, D., Frey, C., Kupferschmid, A., Dyckmans, J., Joss, A., and Lehmann, M. F.: Tracing N2O production pathways in aqueous ecosystems by quasi-simultaneous online analysis of 15N in reactive nitrogen species and gaseous emissions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11890, https://doi.org/10.5194/egusphere-egu23-11890, 2023.

N2O isotopic composition, i.e., δ15N-N2O, δ18O-N2O and especially site preference (SP; difference of substitution frequencies at terminal or central position in N-N-O molecule) has been shown to provide information on N2O source processes, and allows for source partitioning of N2O emissions to nitrification and denitrification. The advent of laser spectrometers more than a decade ago has spawned first datasets of N2O isotopic composition in daily resolution, but they have remained scarce. This is because until recently, the precision of commercially available spectrometers did not allow direct determination of N2O isotopic composition without technically challenging liquid nitrogen free cryogenic preconcentration of N2O. The specifications of the latest commercially available spectrometers promised preconcentration free in-situ determination of N2O isotopic composition, but a recent instrument intercomparison showed that for most of the analyzers, specific correction functions are still necessary. While some available instruments were thoroughly characterized with regard to short term precision, repeatability, drift, amount effects, matrix effects and spectral interferences, instrument performance during field deployment and on the time scale of long measurement campaigns has not been analysed so far.

Here we present a setup and results of an automated chamber system in conjunction with a laser spectrometer that was installed in the field and in use for a period of approx. two years. Initially, amount dependence was in the range of 4 to 2 ‰ ppm N2O-1 for the various isotopic species, but instrument optimizations reduced this dependence to less than 1 ‰ ppm N2O-1. CH4 dependence was constant through the whole period and in the range of 1 to 2 ‰ ppm CH4-1, with affecting only δ15Nα and δ18O. In contrast, CO2 dependence was variable and in the same range as N2O amount dependence. The uncertainty budget was dominated by instrument noise, calibration and N2O amount dependence, indicating that improvements of instrument precision and availability of more suitable reference materials have a high potential to further decrease uncertainty of measurements. Analysis of the effect of uncertainty on the error of determined soil air N2O isotopic composition based on Keeling plots resulted in an error of 2 ‰ and 1 ‰ at N2O concentration increases of 70 and 140 ppb, respectively. Consequently, source partitioning based on SP will be associated with an error of 17 and less than 12% at the moment. Compared to growing-season emissions, SP and δ18O-N2O during freeze-thaw cycles were distinctly different. SP was ~0, indicating that N2O reduction to N2 was negligible during freeze-thaw events.

How to cite: Wolf, B., Xia, L., Smerald, A., Mohn, J., and Kiese, R.: Intramolecular N2O isotopic composition using laser spectrometers: Correction functions, uncertainty budget, freeze-thaw events and source process identification, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12962, https://doi.org/10.5194/egusphere-egu23-12962, 2023.

EGU23-13488 | ECS | Orals | BG2.2

What drives the variability in isotopic fractionation of O2 during enzymatic reactions? 

Carolina F. M. de Carvalho, Moritz F. Lehmann, and Sarah G. Pati

Molecular oxygen (O2) is one of the most important electron acceptors for a large variety of biotic and abiotic processes in the environment. A wide range of oxygen isotopic fractionation associated with biological O2 consumption (e.g., respiration) has been reported in field and laboratory studies (18ɛO2 from -29 to -1 ‰). The observed variability in 18ɛO2 values has mainly been attributed to the different types of respiring organisms. But, to better understand what ultimately causes the variation in isotopic fractionation of O2, it is necessary to start investigating at the lowest level of biological complexity. All biological O2 consumption, including respiration, detoxification, and biosynthesis, occurs at the enzyme-level. A few 18ɛO2 values have been reported for isolated enzymatic O2 reduction reactions. However, these laboratory-scale studies also displayed a wide range of O-isotope effects (18ɛO2 from -33 to -10 ‰), without any systematic correlation between 18ɛO2 values and the type of enzyme, substrate, or O2-reduction mechanism. In this study, we aimed at applying O2 stable isotope analysis to a systematic selection of O2 consuming enzymes, to improve our molecular understanding of isotopic fractionation of O2 at the enzyme-level. In a first series of experiments, we have determined kinetic parameters, as well as 18ɛO2 (and 17ɛO2) values of O2 reduction for a series of copper- and flavin-dependent oxidase enzymes. O2 reduction by these oxidase enzymes occurs separately from substrate oxidation, i.e., O2 is reduced to water (four-electron reduction) or to hydrogen peroxide (two-electron reduction), independently from the type of substrate. Thus, the variability in observed O isotopic fractionation should only depend on the active-site structure and/or the O2 reduction mechanism. Our experimental 18ɛO2 values covered the same range as those previously reported for laboratory-scale studies with other enzymes. Most of the studied flavin- and copper-dependent oxidases displayed no deviation from mass-dependent fractionation (17ɛO2/18ɛO2 ≈ 0.52). We demonstrate that 18ɛO2 values systematically correlate with a given enzyme’s affinity for O2 in flavin-dependent oxidases. Furthermore, our data suggest that the range of 18ɛO2 and 17ɛO2 values differs significantly between flavin- and metal-dependent O2 consuming enzymes. These results represent an important first step towards an improved understanding and generalization of the isotopic fractionation of O2 at the enzyme- and, ultimately, at the organism-level.

How to cite: F. M. de Carvalho, C., Lehmann, M. F., and Pati, S. G.: What drives the variability in isotopic fractionation of O2 during enzymatic reactions?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13488, https://doi.org/10.5194/egusphere-egu23-13488, 2023.

EGU23-14266 | ECS | Orals | BG2.2

Sulfur and carbon isotope measurements of carbonyl sulfide (COS) from small air samples; an overview and recent findings 

Sophie Baartman, Maarten Krol, Thomas Röckmann, and Maria Elena Popa

Carbonyl sulfide (COS) is the most abundant sulfur-containing trace gas in the atmosphere, with an average mixing ratio of 500 parts per trillion (ppt). It has a relatively long lifetime of about 2 years, which permits it to travel into the stratosphere. There, it likely plays an important role in the formation of stratospheric sulfur aerosols (SSA), which have a cooling effect on the Earth’s climate. Furthermore, during photosynthetic uptake by plants, COS follows essentially the same pathway as CO2, and therefore COS could be used to estimate gross primary production (GPP). Unfortunately, significant uncertainties still exist in the sources, sinks and global cycling of COS, which need to be overcome. Isotopic measurements of COS could be a promising tool for constraining the COS budget, as well as for investigating its role in the formation of stratospheric sulfur aerosols.

Within the framework of the COS-OCS project, we developed a GC-IRMS based measurement system at Utrecht University that can measure δ33S, δ34S and δ13C from S+ and CO+ fragment ions of COS from small air samples of 2 to 5 L. With this system, we have measured various types of air samples, including outside air, firn air from Greenland, and air from the upper troposphere – lower stratosphere region. We conducted photosynthesis experiments using a plant gas exchange chamber and we are also planning to measure firn air from Antarctica. Here, we will present an overview of the COS isotope measurements conducted within the COS-OCS project, and we will highlight the most interesting findings.

How to cite: Baartman, S., Krol, M., Röckmann, T., and Popa, M. E.: Sulfur and carbon isotope measurements of carbonyl sulfide (COS) from small air samples; an overview and recent findings, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14266, https://doi.org/10.5194/egusphere-egu23-14266, 2023.

EGU23-14497 | ECS | Posters virtual | BG2.2

Isotopic and chemical characterization of saline lake and playa salts: Implication for climate on Earth and Mars 

Yuxin Hao, Yuhe Qiu, Lanxiadi Chen, Jun Li, Wanyu Liu, Mingjin Tang, Xiying Zhang, Zhenchuan Niu, Jan Pettersson, Sen Wang, and Xiangrui Kong

Evaporite salts from saline lakes and playas play active roles in the atmospheric cycles and the climate system, especially in the context of changing climate. Similar processes also occurred on Mars, where large water bodies dried up and formed saline lakes and then salt evaporites and deposits. In this study, various salt samples (brines, lakebed salts, crust salts, playa surface salts, and a series of salts collected at different depths) were collected from two Martian analogue sites (Mang’ai and Dalangtan, MA and DLT) in Qaidam Basin. The salt samples were measured for their ionic compositions and pH as the fundamental characterization, and the effects of sample types and sampling sites are discussed. The hygroscopic properties of solid salts, including crystalized brines, were experimentally determined. The results show strong connections between the ionic composition and hygroscopic properties though discrepancy exists, indicating that the hygroscopicity is sensitive to the molecular forms and the hydrate degrees of salts. Sulfur and chlorine isotopes were measured, and the results are presented as δ34S and δ37Cl. The δ34S values of samples from MA and DLT show great difference. The δ34S values of MA samples are comparable to previously reported fresh water, brines and local precipitation, indicating that the MA samples are strongly influenced by materials exchanged from local environments. The DLT samples have higher δ34S values, which suggest that the material exchanges with surrounding environments are limited. The δ37Cl values are confined within a relatively narrow window compared to literature values. A trend is that the δ37Cl values vary with sample types, i.e., crust > lakebed > brine. This is likely caused by the isotopic fractionation during evaporite precipitation, where the heavier 37Cl isotope is preferably precipitated. The study of salt samples from MA and DLT areas improves the understanding of the active role of evaporite salts in the material cycle and climate system of both Earth and Mars.

Keywords: δ34S, δ37Cl, hygroscopicity, climate, Mars, Qaidam Basin

How to cite: Hao, Y., Qiu, Y., Chen, L., Li, J., Liu, W., Tang, M., Zhang, X., Niu, Z., Pettersson, J., Wang, S., and Kong, X.: Isotopic and chemical characterization of saline lake and playa salts: Implication for climate on Earth and Mars, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14497, https://doi.org/10.5194/egusphere-egu23-14497, 2023.

EGU23-14514 | ECS | Orals | BG2.2

Measurements of the clumped isotopic composition of atmospheric methane 

Malavika Sivan, Thomas Röckmann, Carina van der Veen, Caroline P. Slomp, and Maria Elena Popa

Atmospheric methane (CH4) is the second most important anthropogenic greenhouse gas after CO­2. Global scale measurements of CH4 mole fraction show an increasing trend since pre-industrial times. Various studies have attempted to attribute the temporal change to variations in the balance between different CH4 sources and atmospheric sink reactions. Measurements of bulk isotopic composition (δ13C and δD) are used for this purpose, but due to the overlap of source signatures, it is difficult to distinguish between biogenic, thermogenic, and pyrogenic CH4. With the advancement of high-resolution mass spectrometry, it is now possible to measure the two most abundant clumped isotopologues of CH4: 13CDH3 and CD2H2. The clumping anomalies denoted as Δ13CD and ΔDD can be used as an additional tool to constrain CH4 sources.

Most of the clumped isotope studies so far, have focused on high-concentration samples, which can easily deliver the large quantity of pure CH4 (several mL) needed to measure the clumped isotopologues. But these measurements could be particularly interesting for atmospheric CH4, for which the explanations of the recent variations are still under debate. As shown by a recent modeling study (1), clumping anomalies, especially ΔDD, have the potential to help distinguish between the main drivers of change in the atmospheric CH4 burden.

In our laboratory, we use the 253-Ultra mass spectrometer to measure the clumped isotopologues of CH4. These measurements require 4-5 mL of pure CH4 to achieve a precision of 0.3 ± 0.1 ‰ for Δ13CD and 2.4 ± 0.8 ‰ for ΔDD. For atmospheric air at 2 ppm, this translates to extracting CH4 from at least 2000 L of air.

We have recently developed a method for extracting and purifying CH4 from this large quantity of air, without modifying its isotopic composition. We will present the current capabilities of this extraction system, and the first results of the clumped isotopic composition of the ambient air.

Reference:

1. Chung, E & Arnold, T 2021, 'Potential of Clumped Isotopes in Constraining the Global Atmospheric Methane Budget', Global Biogeochemical Cycles, vol. 35, no. 10, https://doi.org/10.1029/2020GB006883

How to cite: Sivan, M., Röckmann, T., van der Veen, C., Slomp, C. P., and Popa, M. E.: Measurements of the clumped isotopic composition of atmospheric methane, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14514, https://doi.org/10.5194/egusphere-egu23-14514, 2023.

I will present a newly developed method for analyzing major air components and their isotopic composition, using the high resolution Thermo Ultra mass spectrometer. The main characteristics of this instrument that are interesting in this context are the high resolution, stability and sensitivity.  The high resolution results in fewer isobaric interferences; low abundance compounds (e.g. multiply substituted molecules) can be observed due to the high resolution and high sensitivity; and the instrument stability allows long measurements, as needed for obtaining high precision for the low abundance compounds.

The species that can be analyzed so far with useful precision are:

- O2/N2 and Ar/N2 (precision in permeg range)

- O2 isotopologues, including clumped: 16O2, 16O17O, 16O18O, 17O18O, 18O2

- N2 isotopologues, including clumped: 14N2, 14N15N, 15N2

- Ar isotopes: 36Ar, 38Ar, 40Ar

The whole suite of measurements uses about 10 ml of dry air, and takes up to two days for one sample.

The first application of this method is planned for stratospheric and icecore samples.

How to cite: Popa, M. E.: Direct air measurements using the high resolution Thermo Ultra mass spectrometer: O2/N2 and Ar/N2 ratios, and O2, N2 and Ar isotopic composition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15560, https://doi.org/10.5194/egusphere-egu23-15560, 2023.

EGU23-15737 | ECS | Posters on site | BG2.2

Evaluation of nine years of continuous δ13CO2 measurements in Heidelberg, Germany 

William Cranton, Henrik Eckhardt, Antje Hoheisel, and Martina Schmidt

Measurements of atmospheric CO2 mole fraction in combination with δ13CO2 contain additional information on the CO2 source mixture at a measurement station. Instrumental developments, such as cavity ring-down spectroscopy (CRDS), have facilitated the conduction of continuous in-situ measurements of CO2 mole fraction and δ13CO2 with a high temporal resolution. This has enabled a robust and detailed local time series to be established at an urban station in Heidelberg in south-western Germany, where a CRDS G2201-i analyser has been used to measure the CO2 mole fraction and 13C/12C ratio from 2014 to 2023. This nine year time series is analysed for seasonal variations and trends in regional and local CO2 sources. We applied different approaches based on the Keeling/Miller-Tans method to identify δ13CO2 source signatures within the Heidelberg catchment area. Doing this gave δ13CO2 source values that were less depleted in the summer and more depleted in the winter, indicating a stronger biogenic effect in summer and stronger fossil fuel contributions in winter.

How to cite: Cranton, W., Eckhardt, H., Hoheisel, A., and Schmidt, M.: Evaluation of nine years of continuous δ13CO2 measurements in Heidelberg, Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15737, https://doi.org/10.5194/egusphere-egu23-15737, 2023.

EGU23-16104 | Orals | BG2.2

Sedimentary and dark production sources of COS and CS2 identified by their sulfur isotopic values 

Alon Amrani, Chen Davidson, Sinikka T. Lennartz, and Alon Angert

Carbonyl sulfide (COS) is a long-lived trace gas, and an important precursor for stratospheric sulfate aerosols, which reduce solar radiation reaching earth surface and may regulates earth's climate. The main sink of COS is the uptake by terrestrial plants similar to CO2. Thus, COS is used as a proxy for CO2 removal by terrestrial plants (gross primary production, GPP). Oceans are the major source of COS to the atmosphere , either directly or indirectly by emitting other volatile sulfur compounds such as CS2 and DMS that partially oxidize to COS in the atmosphere.  In the surface ocean, COS is produced by photochemical reactions and by "dark production" deeper in the water column and from sediments. In the present study we aim to determine and quantifying the COS and CS2 “dark production” by using sulfur isotopes measurements (34S/32S; δ34S) of surface, deep water and sediment samples. In addition, laboratory experiments were conducted to follow the productions of COS and CS2 by direct reactions with CO and HS-/SX2- and by incubations experiments of seawater. Our preliminary results from the Atlantic Ocean, the Mediterranean, North, Wadden, and Red Seas show surface δ34S values in the range of -4 to 20‰ for COS, and -10 to 22‰ for CS2 while DMS was 18-21‰. The δ34S values of DMS are in line with previous measurements of the surface ocean and reflect its biological source with small isotopic fractionation relative to marine sulfate (21‰). This was also expected for COS and CS2 that also produced from biological sources. However, their δ34S values extended over large ranges up to 30‰, while their heaviest δ34S value are closed to DMS. There are clear mixing lines for COS and CS2 between the surface ocean sources (heavy) and the sedimentary sources (light) in shallow water. The isotopic values of sedimentary-production are calculated as -4‰ for COS and -10‰ for CS2, based on the samples from the sediment rich waters of the Wadden Sea. These values suggest abiotic sulfurization of light organic compounds by 34S depleted HS-/SX2- from the microbial sulfate reduction (MSR) in the sediment. Indeed, the intertidal sands of the Wadden Sea are known to host intense MSR activity and produce large amounts of H2S and polysulfides. The specific organic precursors are still unknown and will be the subject of our upcoming experiments. Also, the “dark production” isotopic signals of the surface water is not yet well resolved, but seems also to be isotopically lighter then DMS and marine sulfate. These new findings show that the COS/CS2 sources in the ocean are complex combining contributions from several biotic and abiotic processes which seem to have unique isotopic signatures.   

How to cite: Amrani, A., Davidson, C., T. Lennartz, S., and Angert, A.: Sedimentary and dark production sources of COS and CS2 identified by their sulfur isotopic values, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16104, https://doi.org/10.5194/egusphere-egu23-16104, 2023.

EGU23-16611 | Orals | BG2.2

Seasonal and spatial variation in 13C signature of emitted methane and pore water methane in northern mires 

Janne Rinne, Xuefei Li, Patryk Łakomiec, Patrik Vestin, Per Weslien, Julia Kelly, Lukas Kohl, Lena Ström, Timo Vesala, and Leif Klemedtsson

Methane emission from northern mires shows typically strong spatial and seasonal variations. These variations have been assigned to e.g. differences in methane production due to variation in substrate input, transport pathways, methane oxidation in aerobic peat layers, and temperature variations. Stable isotope signatures of the emitted methane and methane in pore water can help us to constrain our hypotheses of these variations.

We have measured δ13C of methane emission in Mycklemossen mire in Sweden by automated chamber system for two years. We also have measured δ13C of methane in pore water in three depths in Siikaneva mire in Finland by an automated diffusion tube system for one seasonal cycle. At both sites ecosystem scale δ13C of emitted methane was measured using nocturnal boundary layer accumulation (NBLA) approach.

We observed systematic spatial variation in δ13C of emitted methane at Mycklemossen site, which mostly indicated the importance of substrate availability in explaining the spatial variability. At Siikaneva we observe systematic differences in the depth distribution of δ13C of pore water methane. Interestingly, this distribution is different in summer and winter.  The ecosystem scale δ13C of emitted methane derived by chambers and NBLA approach very close to each other. We will discuss the observations, their implications, and future integration of the data and new measurement.

 

How to cite: Rinne, J., Li, X., Łakomiec, P., Vestin, P., Weslien, P., Kelly, J., Kohl, L., Ström, L., Vesala, T., and Klemedtsson, L.: Seasonal and spatial variation in 13C signature of emitted methane and pore water methane in northern mires, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16611, https://doi.org/10.5194/egusphere-egu23-16611, 2023.

Where do oxygen and hydrogen atoms of organic matter from terrestrial plant, such as O and H in cellulose, come from? We already know that O in cellulose originates from water within plants, instead of CO2 taken in via leaf stomata, and stable isotope tracers gave an answer to this question (Deniro & Epstein 1979, Science).

 We know that all vascular plants acquire water from the soil via their roots. However, in recent years, we have learned that plants can also acquire significant amount of water directly through their leaves (Burgess and Dawson 2004, Plant, Cell & Environment; and others) and foliar-absorbed water can be a source of oxygen atoms of sugars in leaves (Lehmann et al. 2018, New Phytologist). Then, an interesting question comes up to our mind: where does the water that eventually become O and H in cellulose come from? Until recently, these water sources were thought to only be taken up by roots, as we have learned from our introductory biology textbook (Dawson 2022, Tree Physiology). However, validity of this common perception has recently been questioned, when, using hydrogen and oxygen isotope tracer in vapour or mist form, two researchers have demonstrated that foliar-absorbed water can be assimilated into organic matter (Studer et al. 2015, Biogeosciences; Lehmann et al. 2018). However, relative contributions of foliar-absorbed water and root-absorbed water assimilation into O and H in cellulose have remained an open question.

I therefore devised a labelling method that utilizes two different water sources, one enriched in deuterium and one enriched in oxygen-18, to simultaneously label both foliar-absorbed and root-absorbed water and quantify their relative contributions to plant organic matter (Kagawa 2022, Tree Physiology, https://doi.org/10.1093/treephys/tpac055). Using this new method, I will present evidence that, in the case of well-watered Cryptomeria japonica, hydrogen and oxygen incorporated into new leaf cellulose in the rainy season derives mostly from foliar-absorbed water (69% from foliar-absorbed water and 31% from root-absorbed water), while that of new root cellulose derives mostly from root-absorbed water (20% from foliar-absorbed water and 80% from root-absorbed water), and new branch xylem is somewhere in between (55% from foliar-absorbed water and 45% from root-absorbed water, see figure below). The novel dual labelling method first implemented in this study enables separate and simultaneous labelling of foliar-absorbed and root-absorbed water, and offers a new tool to study the uptake, transport, and assimilation processes of these waters in terrestrial plants. Thanks to our recent methodological breakthroughs, this new tool will soon be publicly available, as it has become easy to enclose wet tissue samples from labelled trees into smooth wall tin capsules without significant leaks, and our laboratory can now routinely analyze H and O isotope ratios of 200 samples that are labelled with heavy water per week.

 

How to cite: Kagawa, A.: Foliar water uptake as a source of hydrogen and oxygen in cellulose of vascular plants, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1769, https://doi.org/10.5194/egusphere-egu23-1769, 2023.

EGU23-2218 | Posters on site | BG2.3

Does metabolic water control the isotopic composition of water in microbial cells? 

Alon Angert, Tal Weiner, Federica Tamburini, Hagit Zer, and Nir Keren

Metabolic water, the water that is produced from O2 during respiration, carries an isotopic signature that can be different from that of the water the cell is growing in. It has been well known that for large land organisms, like birds and mammals, metabolic water contributes significantly to the water balance and has an important control on the signature of the oxygen-stable-isotopes of the water inside the organism. This isotopic signature is then carried over through isotopic equilibrium to other oxygen-bearing species like phosphate. However, for small organisms like bacteria, it has been widely assumed for decades, that the large surface area to volume ratio enables a fast exchange of the cell water with the ambient water. As a result, the isotopic signature of the metabolic water will be heavily diluted and erased. In contrast, a recent work reported indirect evidence of significant control of metabolic water on the oxygen isotopes inside microbial cells. This indirect evidence is based on deviations of oxygen isotopes in phosphate from the expected equilibrium with the ambient water. Here we report the results of experiments that directly tested the possible contribution of metabolic water to phosphate oxygen isotopes in bacteria. We found that ambient water did control the oxygen isotopes in the phosphate. However, there were large deviations from the expected equilibrium. Nevertheless, we found that these deviations were not correlated with the isotopic composition of metabolic water. Hence, other mechanisms, which will be discussed, are responsible for these deviations.

How to cite: Angert, A., Weiner, T., Tamburini, F., Zer, H., and Keren, N.: Does metabolic water control the isotopic composition of water in microbial cells?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2218, https://doi.org/10.5194/egusphere-egu23-2218, 2023.

EGU23-2967 | ECS | Posters on site | BG2.3

Novel insights into the biochemical drivers shaping hydrogen isotope values of sugar and cellulose within a plants’ leaf 

Philipp Schuler, Oliver Rehmann, Valentina Vitali, Matthias Saurer, Nina Buchmann, Arthur Gessler, and Marco Lehmann

Recent methodological achievements in determining the non-exchangeable hydrogen isotopic composition (δ2Hne) of non-structural carbohydrates such as sugars allow to disentangle of so far hidden hydrogen isotope (2H) fractionation processes influencing δ2Hne of plant carbohydrates. We conducted two climate chamber experiments to have a closer look at the basic biochemical drivers of the photosynthetic 2H fractionation between water and sugar and the post-photosynthetic 2H fractionation between sugars and cellulose in leaves: First, we studied the impact of the different biochemical reactions in 10 species with C3, 7 species with C4, and 8 species with CAM carbon fixation pathways, and their response to changes in temperature and vapor pressure deficit (VPD). Second, we investigated the impact of a temperature increase from 10 to 40°C in 5°C steps under a constant VPD on leaf level photosynthesis and metabolic functioning of 7 plant species. The first experiment revealed distinct differences in the photosynthetic 2H fractionation between C3, C4, and CAM plants. In addition, the observed intensity and direction of the shifts in δ2Hne in response to changes in temperature and VPD in C3 plants was species specific, absent in C4 plants, and again species-specific in CAM plants. However, post-photosynthetic 2H fractionation was very similar among the three types of carbon fixation. We demonstrate that, in contrary to widespread believes, the 2H enrichment during post-photosynthetic 2H fractionation is driven by the carbohydrate metabolism, and not by an isotopic exchange with surrounding water. The results of the second experiment identified a plants’ metabolic activity, and its response to changes in temperature, as a major driver of the post-photosynthetic 2H fractionation of leaf sugars in C3 species. Our results clearly demonstrate that δ2Hne of plant carbohydrates are driven by plants metabolism and its response to the environment, which are species-specific. This will help to improve our current ability to interpret δ2Hne chronologies in tree rings and other plant archives, and to use 2H fractionation in carbohydrates as a novel proxy to study a plants’ metabolic properties.

How to cite: Schuler, P., Rehmann, O., Vitali, V., Saurer, M., Buchmann, N., Gessler, A., and Lehmann, M.: Novel insights into the biochemical drivers shaping hydrogen isotope values of sugar and cellulose within a plants’ leaf, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2967, https://doi.org/10.5194/egusphere-egu23-2967, 2023.

The 18O/16O ratio of a-cellulose in land plants has proved of interest for climate, environmental, physiological and metabolic studies. Reliable application of such ratio may be compromised by the presence of hemicellulose impurities in the a-cellulose product obtainable with current extraction methods, as the impurities are known to be isotopically different from that of the a-cellulose. We firstly compared the quality of hydrolysates of “a-cellulose products” obtained with four repre-sentative extraction methods (JAYME and WISE; BRENDEL; ZHOU; LOADER) and quantified the hemicellulose-derived non-glucose sugars in the “a-cellulose products” from 40 land grass species using GC/MS. Secondly, we performed com-pound-specific oxygen isotope analysis for the hydrolysates using GC/Pyrolysis/IRMS. These results were then compared with the bulk isotope analysis using EA/Pyrolysis/IRMS of the “a-cellulose products”. We found that the ZHOU method afforded overall the highest purity a-cellulose as judged by the minimal presence of lignin, and the second lowest presence of non-glucose sugars in the investigated grass species. Isotopic analysis then showed that the O-2~O-6 of the a-cellulose glucosyl units were all depleted in 18O by 0.0-4.3 mUr (with an average of 1.9 mUr) in a species-dependent manner relative to the a-cellulose products. The positive isotopic bias of using a-cellulose product instead of the glucosyl units stems mainly from the fact that the pentoses that dominate hemicellulose contamination in the a-cellulose product are relatively enriched in 18O (compared to hexoses) as they inherit only the relatively 18O-enriched O-2~O-5 moiety of sucrose, the common bio-chemical precursor of pentoses and hexoses in cellulose, and are further enriched in 18O by the (incomplete) hydrolysis. Failure to prepare a-cellulose with the highest possible purity, free from lignin and hemicellulose contamination, can bias predictions based on mechanistic models linking a-cellulose oxygen isotope composition to plant growth conditions.

How to cite: Zhou, Y.: On the chemical purity and oxygen isotopic composition of a-cellulose extractable from higher plants and the implications for climate, metabolic and physiological studies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3902, https://doi.org/10.5194/egusphere-egu23-3902, 2023.

Stable oxygen isotope composition of tree ring cellulose (d18Ocell) has been increasingly used as a tool for reconstruction of environmental conditions (e.g. air temperature, precipitation, relative humidity) and ecophysiological variables (e.g. leaf temperature, stomatal conductance) that prevail during the period of tree growth. The current tree-ring d18Ocell mechanistic model assumes no oxygen exchange/biochemical fractionation effect during sucrose loading from the source leaf to the phloem, but is has been debated as to whether or not such an assumption is valid. Here, we performed an experimental study to quantify the possible extent of carbonyl-water exchange of oxygen during phloem loading. Towards this goal, we used a custom-made multiple-channel water vapor isotope signal labeling system to expose experimental plants to a range of water vapor d18O compositions under physiologically stable conditions; this in turn allowed the creation of a large gradient in d18O of leaf water, leaf sucrose, and phloem sucrose without disrupting plant physiology. We will present data collected from this experiment to examine the d18O relationships among the various water and sucrose pools, which may provide some insights into the possible isotope effects associated with sucrose translocation from leaf to the phloem. 

How to cite: Song, X.: Does carbonly-water exchange of oxygen occur during phloem loading of sucrose? An exploratory study involving vapor 18O labelling techniques.    , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4036, https://doi.org/10.5194/egusphere-egu23-4036, 2023.

EGU23-5629 | ECS | Posters on site | BG2.3

Hydrogen isotopes in leaf and tree-ring organic matter as potential indicators of drought-induced tree mortality 

Haoyu Diao, Marco M. Lehmann, Shengnan Ouyang, and Arthur Gessler

Drought-induced tree mortality is occurring more frequently in the world, with both the direct impact of drought (i.e., heat and drought events) and the mortality predisposition (e.g., tree nutrition status) influencing death or survival of trees. The oxygen and hydrogen isotopic compositions (δ18O and δ2H) of plant water are widely used as hydrological indicators. Both elements in water are tightly correlated and are the key source for the isotopic composition of plant organic matter. Yet, recent studies show that the relationship between δ18O and δ2H values in organic matter is weaker and more divergent. This is probably caused by physiological and metabolic processes (i.e., assimilation, assimilate allocation, use of reserves) that are integrated into δ2H but not into δ18O. This let us hypothesize that δ2H can function as a useful tool in tree mortality research to study assimilate and storage related reason (i.e., carbon starvation) of tree death, but more knowledge is urgently needed.

To test our hypothesis, we studied the pre-disposal fertilization and drought effects on δ18O and δ2H values in plant water and organic matter in a greenhouse experiment. We planted three years old saplings of Abies alba, Acer pseudoplatanus, Picea abies, Pinus sylvestris and Quercus petraea, half of which were treated with a slow-release formula fertilizer (control (F0) and fertilization (F+)); one year later, half of the F0 and half of the F+ plants were selected for a lethal drought treatment (control (D0) and drought (D+)), i.e., D0 plants were watered to field capacity, while D+ plants received no more water until they died. After 6 weeks of drought, leaf and twig samples were collected for δ18O and δ2H analyses of plant water. After the D+ plants died (i.e., 9-15 weeks after start of drought), additional leaf and stem material were collected from a same number of D0 and D+ plants. Organic matter of leaf and tree-ring of the recent year were prepared for δ18O and δ2H analyses. Additional physiological and metabolic factors were measured to examine the treatment effects.

Across all species, we found that the pre-disposal fertilization had no significant effect on δ18O and δ2H values of plant water and organic matter. On the other hand, the drought treatment significantly increased both δ18O and δ2H values of leaf and twig water, while it only significantly increased δ2H values of leaf and tree-ring organic matter. These results indicate that δ2H in leaf and tree-ring organic matter in dying trees can capture drought-induced tree mortality signals. We propose that the 2H-enrichment in the drought-exposed trees might be related to (i) the imprint of 2H-enriched signal of plant water; (ii) drought-induced changes in the metabolic processes of sugar biosynthesis; (iii) drought-induced changes in the use of carbon reserves. In summary, our study supports the idea that hydrogen isotopes can function as a potential diagnostic tool in tree mortality studies.

How to cite: Diao, H., Lehmann, M. M., Ouyang, S., and Gessler, A.: Hydrogen isotopes in leaf and tree-ring organic matter as potential indicators of drought-induced tree mortality, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5629, https://doi.org/10.5194/egusphere-egu23-5629, 2023.

EGU23-6301 | ECS | Orals | BG2.3

Recent progress in the application of hydrogen isotopes from tree-ring lignin methoxy groups as a climate proxy 

Anna Wieland, Markus Greule, Philipp Roemer, Jan Esper, Nemiah Ladd, Marco Lehmann, Philipp Schuler, and Frank Keppler

Stable hydrogen isotope values of tree-lignin methoxy groups (δ2HLM) are increasingly applied to reconstruct the stable hydrogen isotope composition of precipitation (δ2Hprecip) and mean annual temperatures in mid-latitude regions. The climate reconstructions are typically derived considering an isotope fractionation from -200 mUr to -216 mUr between lignin methoxy groups and tree source water (Keppler et al. 2007, Anhäuser et al. 2017, Greule et al., 2021, Porter et al. 2022, Wieland et al. 2022). This empirical relationship was derived from different tree species collected along a European north-south transect at elevations below 1000 m above sea level. However, it is so far unknown how environmental and physiological factors such as tree age, tree species, salinity, elevation, or precipitation amount influence the biochemical hydrogen isotope fractionation between lignin methoxy groups and precipitation.

We here present several recent investigations that show how environmental and tree physiological factors might influence δ2HLM values. For example, potential amount effects of precipitation are analysed using tree cores from the Carpathians, where the mountain barrier led to large precipitation events at the Luv site. In addition, potential age trends are studied using trees from Greece that are over 500 years old, and the phylogenetical range of δ2HLM values is assessed by comparing 70 different tree species grown under uniform climatic conditions. Finally, the influence of salinity is evaluated by analysing different mangrove tree species from Australia.

The improvements and limitations of δ2HLM values as a climate proxy at different spatial and temporal scales will be discussed. In order to better reconstruct long-term climate variations, additional gain is expected from the cross-comparison of multiple isotope proxies, including stable carbon isotope values of cellulose and lignin methoxy groups, as well as stable oxygen isotopes of cellulose.

References:

Anhäuser, T., Greule, M., Polag, D., Bowen, G. J., and Keppler, F.: Mean annual temperatures of mid-latitude regions derived from δ2H values of wood lignin methoxyl groups and its implications for paleoclimate studies, Sci. Total Environ., 574, 1276–1282, https://doi.org/10.1016/j.scitotenv.2016.07.189, 2017.

Greule, M., Wieland, A., and Keppler, F.: Measurements and applications of δ2H values of wood lignin methoxy groups for paleoclimatic studies, Quaternary Sci. Rev., 268, 107107, https://doi.org/10.1016/j.quascirev.2021.107107, 2021.

Keppler, F., Harper, D. B., Kalin, R. M., Meier-Augenstein, W., Farmer, N., Davis, S., Schmidt, H. L., Brown, D. M., and Hamilton, J. T. G.: Stable hydrogen isotope ratios of lignin methoxyl groups as a paleoclimate proxy and constraint of the geographical origin of wood, New Phytol., 176, 600–609, https://doi.org/10.1111/j.1469-8137.2007.02213.x, 2007.

Porter, T. J., Anhäuser, T., Halfar, J., Keppler, F., Csank, A. Z., and Williams, C. J.: Canadian Arctic Neogene temperatures reconstructed from hydrogen isotopes of lignin‐methoxy groups from sub‐fossil wood, Paleoceanogr. Paleoclimatology, 37, https://doi.org/10.1029/2021pa004345, 2022.

Wieland, A., Greule, M., Roemer, P., Esper, J., and Keppler, F.: Climate signals in stable carbon and hydrogen isotopes of lignin methoxy groups from southern German beech trees, Clim. Past, 18, 1849–1866, https://doi.org/https://doi.org/10.5194/cp-18-1849-2022, 2022.

How to cite: Wieland, A., Greule, M., Roemer, P., Esper, J., Ladd, N., Lehmann, M., Schuler, P., and Keppler, F.: Recent progress in the application of hydrogen isotopes from tree-ring lignin methoxy groups as a climate proxy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6301, https://doi.org/10.5194/egusphere-egu23-6301, 2023.

EGU23-6353 | Posters on site | BG2.3

Effects of vapour pressure deficit, temperature and soil drought on triple isotope patterns of assimilates and tree-ring cellulose 

Marco M. Lehmann, Philipp Schuler, Leonie Schönbeck, Oliver Rehmann, Haoyu Diao, Valentina Vitali, and Charlotte Grossiord

Stable isotope compositions of carbon (δ13C) and oxygen (δ18O) in plant carbohydrates such as photosynthetic assimilates or cellulose are widely applied tools to reconstruct climate and plant physiological responses. In contrast, applications of hydrogen isotope composition (δ2H) in plant carbohydrates are limited because of previous methodological constrains and limited knowledge on processes causing hydrogen isotope fractionations. To better understand the individual climatic drivers of isotopic variations in tree rings, particularly for δ2H, we performed a controlled experiment over one growing season in climate chambers with saplings of broadleaf and conifer tree species. The growing conditions resembled conditions that can be typically found in the field: vapor pressure deficit (VPD; 1.0, 1.6, and 2.2 kPa), air temperature (T; 25 and 30 °C), and soil drought (D, well-watered and extreme dry).  After 5 months of treatment, δ13C, δ18O, and δ2H of water, sugars and starch in stems and leaves, as well as in cellulose of the recent year tree rings were measured. For δ2H analyses of plant carbohydrates, we applied a newly developed hot water vapour equilibration method (Schuler et al., 2022, doi.org/10.1111/pce.14193). Across all species, first results show that the three elements in tree-ring cellulose respond differently to the climatic drivers: both δ2H and δ13C values increased with increases in D and VPD, but the VPD responses were more pronounced under high than under low T conditions. In contrast, δ18O values were affected by T and VPD, while the VPD response was more pronounced under wet than under dry soil D conditions. Thus, the combination of δ2H and δ13C values could be used to identify D occurrences independent of VPD conditions, while δ18O value is a better indicator for T and VPD responses. In the following steps, the isotopic variations in tree-ring cellulose will be linked to those in water, sugars, and starch and their concentrations in leaf and stem material, as well as to various other structural and functional traits which have been measured throughout the experiment (Schönbeck et al., 2022, doi.org/10.1111/pce.14425). With this unique experimental design, we aim to provide new knowledge facilitating the interpretation of stable isotope patterns in tree rings under field conditions.

How to cite: Lehmann, M. M., Schuler, P., Schönbeck, L., Rehmann, O., Diao, H., Vitali, V., and Grossiord, C.: Effects of vapour pressure deficit, temperature and soil drought on triple isotope patterns of assimilates and tree-ring cellulose, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6353, https://doi.org/10.5194/egusphere-egu23-6353, 2023.

EGU23-7297 | Orals | BG2.3

Hydrogen isotope offsets between palmitic acid and phytol increase during cyanobacterial blooms 

Nemiah Ladd, Antonia Klatt, Cindy de Jonge, Marta Reyes, Carsten Schubert, and Daniel Nelson

Hydrogen isotope fractionation between source water and lipids is highly variable among different taxonomic groups, and also among different compound classes within individual organisms. This variability results in lipid δ2H values that often span as much as two orders of magnitude more variability than that of environmental waters within typical ecosystems, indicating that lipid δ2H values may provide valuable biochemical and ecological information. These applications of lipid δ2H values remain underexplored.

Recent results from algal batch cultures indicate that hydrogen isotope fractionation by cyanobacteria differs significantly compared to eukaryotic algae. In particular, in single species cultures with constant water δ2H values, cyanobacteria tend to produce fatty acids that are slightly 2H-enriched compared to those from most eukaryotic algae, while phytol from cyanobacteria is very 2H-depleted compared to phytol from eukaryotes. This results in larger offsets between the δ2H values of phytol and fatty acids for cyanobacteria than those observed in eukaryotic algae. In order to determine if δ2H offsets between fatty acids and phytol change in freshwater lakes with variable abundance of cyanobacteria, we collected algal biomass from two depths in the water column of Rotsee, a small lake in central Switzerland, every second week from January 2019 to February 2020. During this time the percentage of algal biovolume from cyanobacteria ranged from 0 to 82 %, with two distinct cyanobacterial blooms occurring in July and October.

Water isotopes in the lake were relatively stable throughout the year, with water δ2H values varying by < 10 ‰. Lipid δ2H values, on the other hand, displayed extreme variability throughout the year. Palmitic acid (C 16:0) δ2H values varied by nearly 100 ‰ (–282 to –192 ‰), while those of phytol varied by more than 200 ‰ (–417 to –168 ‰). Consistent with expectations based on the results of cultures of single algal species, cyanobacterial blooms were characterized by larger offsets between the δ2H values of palmitic acid and phytol, and these offsets were positively correlated with the percentage of total algal biovolume attributable to cyanobacteria (R2 = 0.29; p < 0.01). These results suggest that hydrogen isotope offsets between palmitic acid and phytol in sediments have the potential to be developed as proxies for past cyanobacterial blooms, and demonstrate that hydrogen isotopes of lipids in the geologic record that are produced by many different types of aquatic organisms are more likely to be driven by ecological changes rather than changes in water isotopes.

How to cite: Ladd, N., Klatt, A., de Jonge, C., Reyes, M., Schubert, C., and Nelson, D.: Hydrogen isotope offsets between palmitic acid and phytol increase during cyanobacterial blooms, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7297, https://doi.org/10.5194/egusphere-egu23-7297, 2023.

EGU23-9401 | Posters on site | BG2.3

Identifying sources of hydrogen isotope fractionation in plant carbohydrates and lipids under low carbohydrate supply 

Meisha Holloway-Phillips, Anina Wacker, Günter Hoch, Daniel B. Nelson, Marco Lehmann, and Ansgar Kahmen

Appreciation for the influence of plant metabolism on the hydrogen isotope composition (δ2H) of plant compounds has increased in recent years, adding new opportunities to understand how plants respond to environmental change. In general, where carbon supply is limited (e.g. at the beginning of the growth season, in darkness, under low CO2), the resulting δ2H of newly produced plant compounds tends to be 2H-enriched. The source of the 2H-enrichment has yet to be identified but hypotheses include: 1) a direct effect of reduced photosynthesis; 2) change in the partitioning of photoassimilates to sucrose/transitory starch; 3) use of longer-term starch reserves; and/or, 4) increased isotopic exchange with water suggesting increased metabolite cycling. To test these ideas, we utilised samples collected from a study which grew tree saplings under 100% and 6% of ambient sunlight in the field (Weber et al. 2018, New Phytologist, 222: 171-182).  In general, relative growth rate was attenuated by a species-specific amount that ensured homeostasis of non-structural carbohydrate (NSC) concentrations; however, not before an initial two-fold reduction in NSC levels – the time period the current study focussed on. Cellulose was purified and n-alkanes extracted from leaves of six deciduous species (Betula pendula, Carpinus betulus, Fagus sylvatica, Prunus avium, Quercus petraea and Tilia platyphyllos) in July 2016, around one year after the shade treatment began. The isotopic difference of cellulose between shaded and full sunlit grown leaves (εshade-sun) was significantly different from zero, with species-specific offsets ranging between 20 to 70‰. In comparison, the treatment effect was minimal for the C-chain length concentration weighted δ2H values of n-alkanes, ranging between -7 to +10‰. To narrow down the source of 2H-enrichment in leaf cellulose, the δ2H of sucrose and starch are currently being analysed in samples collected from stem wood (without bark) before bud-break in March 2016, and in leaf and stem material sampled after leaf-out in July 2016. An increase in sucrose δ2H values from shade leaves relative to controls would support Hypothesis 1 and 2; 2H-enriched storage starch relative to leaf sucrose would support Hypothesis 3; and an increase in the δ2H of sucrose in stem wood relative to storage starch (before bud-break), would support Hypothesis 4. Our study has important implications for interpreting 2H-enrichment of plant compounds with respect to reduced C supply.

How to cite: Holloway-Phillips, M., Wacker, A., Hoch, G., Nelson, D. B., Lehmann, M., and Kahmen, A.: Identifying sources of hydrogen isotope fractionation in plant carbohydrates and lipids under low carbohydrate supply, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9401, https://doi.org/10.5194/egusphere-egu23-9401, 2023.

In contrast to tree-ring width, oxygen isotope ratio (δ18O) of tree-ring cellulose does not usually show clear age trend, indicating that it can be utilized to reconstruct past climate variation not only for the high frequency domain but also for the low frequency domain. However, in some conifer trees growing in dense forests, there are predominant trends in the tree-ring cellulose δ18O decreasing with age as well as the tree-ring width, making the long-term climate reconstruction difficult. In such trees, hydrogen isotope ratios (δ2H) of tree-ring cellulose usually show the opposite trend to that of δ18O, suggesting that the age trend in tree-ring δ18O and δ2H are owing to age-related changes in the rate of post-photosynthetic isotope exchanges between carbohydrate and xylem water before the cellulose synthesis.

Based on an assumption that tree-ring cellulose δ18O and δ2H vary in positive and negative relationships due to climatological and physiological factors respectively, Nakatsuka et al (2020) proposed a simple method to separate climatological and physiological components in original tree-ring cellulose δ18O time-series by integrating the δ18O and δ2H data in order to reconstruct past climate variation for all frequency domains seamlessly. In this method, it is very important to fix the quantitative relationship between the long-term age-related changes in δ18O and δ2H due to the post-photosynthetic process. However, it is quite difficult to elucidate the physiological relationship between δ18O and δ2H quantitatively by investigating the tree-ring δ18O and δ2H time-series solely because they are influenced not only by the physiological mechanism but also by climate variations.

Here, we propose a new strategy to study physiological controls on the tree-ring cellulose δ18O and δ2H quantitatively. It is based on vertical changes in tree-ring isotope ratios along trunks, those have been seldom investigated in previous dendrochronological studies. We measured inter-annual variations in tree-ring cellulose δ18O and δ2H at different heights in individual trunks of cypress (Chamaecyparis obtusa) and cedar (Cryptomeria japonica) in central Japan and found that the cellulose isotope ratios showed clear vertical trends together with the ring width. From top to bottom along the trunk, the δ18O decreased and the δ2H increased, suggesting that we can monitor the age trend in tree rings not only in the horizontal direction but also in the vertical direction, such that “the top is youngest and the bottom is oldest”, without being influenced by the climate variation. Based on the fact that leaves are located only at the top of trunk in the dense conifer forest, we will discuss the effects of post-photosynthetic isotopic exchanges quantitatively and elucidate the mechanism underlying the apparent age trends in the tree-ring cellulose δ18O and δ2H.

How to cite: Nakatsuka, T., Kato, M., Kato, Y., and Li, Z.: Vertical changes in cellulose oxygen and hydrogen isotope ratios along conifer trunks: Implications for physiological controls on tree-ring isotopes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10378, https://doi.org/10.5194/egusphere-egu23-10378, 2023.

EGU23-11722 | Posters virtual | BG2.3

Beyond traditional summer air temperature signals in subarctic tree rings using hydrogen and oxygen isotopes 

Marina Fonti, Matthias Saurer, Trevor Porter, Mikhail Zharkov, Valentin Barinov, Anna Taynik, Alexander Kirdyanov, Anastasya Knorre, Martin Wegmann, Tatyana Trushkina, Nataly Koshurnikova, Eugene Vaganov, Vladimir Myglan, Rolf Siegwolf, and Olga Churakova (Sidorova)

Classical tree-ring parameters like tree-ring width, maximum latewood density and cell wall thickness record summer air temperature at high latitudes well and allow for the reconstruction of summer temperature over centuries and millennia. However, information about other climatic factors (e.g. moisture and sunshine duration) is limited in these proxies, especially for temperature-limited environments in subarctic forests growing on permafrost soils. The application of stable hydrogen and oxygen isotopes can provide complementary information about moisture changes and solar irradiation.

Solar irradiation and its seasonal distribution play an important role for trees in terms of photosynthesis and carbohydrate production, which can influence deuterium variations in organic matter in addition to hydrological processes. We found that hydrogen and oxygen isotopes in larch tree-ring cellulose from Siberia show a strong link with summer sunshine duration during the growth season. Negative correlations with sunshine duration during autumn of the previous year and winter of the current year can be related to the lack of light during polar nights at subarctic sites (> 60º N) and lack of needles in larch trees to produce photosynthates in a cold environment. Indirect effects might also arise as a high amount of winter sunshine means persistent high-pressure systems with low precipitation, therefore negatively affecting snow accumulation, which is an important water source after snow melt.

Uptake of winter precipitation is possible in the warming spring and summer months after snowmelt and thawing of the active soil layer, resulting in significant correlations between tree-ring oxygen values and winter-spring air temperatures. Oxygen isotopes in organic matter are influenced by variations in the isotopic composition of source water, which is closely related to that of precipitation and soil water (though modified by evaporation at the soil surface).

Furthermore, we observed that summer vapor pressure deficit is positively and significantly recorded in stable oxygen isotopes from northeastern Siberia, while continuously represented through spring-summer months in western Canada. Hydrogen tree-ring isotopes from the Canadian subarctic recorded a negative significant correlation with summer relative humidity, opposite to northeastern Siberia.

The application of dual hydrogen and oxygen stable isotopes in tree rings can expand our knowledge beyond traditional summer air temperature reconstructions and will help to improve climate reconstructions over the past millennia.

Acknowledgements: This work was supported by the project RSF 21-17-00006.

How to cite: Fonti, M., Saurer, M., Porter, T., Zharkov, M., Barinov, V., Taynik, A., Kirdyanov, A., Knorre, A., Wegmann, M., Trushkina, T., Koshurnikova, N., Vaganov, E., Myglan, V., Siegwolf, R., and Churakova (Sidorova), O.: Beyond traditional summer air temperature signals in subarctic tree rings using hydrogen and oxygen isotopes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11722, https://doi.org/10.5194/egusphere-egu23-11722, 2023.

EGU23-12998 | Posters on site | BG2.3

Long-term physiological responses of herbaceous plants to global change from carbon and oxygen isotopes in herbarium specimen 

David Basler, Daniel B. Nelson, Jurriaan de Vos, Cristina Moreno-Gutiérrez, and Ansgar Kahmen

The analysis of the isotopic composition in herbarium specimens gives insight into the physiological responses of plants to environmental change. Specifically, the carbon isotope composition of plants is linked to the time-integrated, leaf-level intrinsic water use efficiency (i.e., the ratio of net photosynthesis over stomatal conductance), while the oxygen isotope composition is linked to leaf stomatal conductance. Thus, by combining stable isotope analyses of carbon and oxygen, trends in integrated values for net photosynthesis and stomatal conductance can be determined. Here, we present results from analyses of carbon and oxygen isotope values from over 3000 sampled herbarium specimens, that have been collected across Switzerland over the past century covering more than 80 herbaceous plant species and a wide range of habitats. While plants across most taxa and habitats have increased their intrinsic water use efficiency over the last decades, the contribution of net photosynthesis or stomatal conductance to changes in intrinsic water use efficiency differs among different plant functional groups (herbs, legumes, grasses, and sedges). Applying a multi-model approach, our study demonstrates that the carbon and water relations of plants respond to long-term changes in the environment but that the physiological nature of these responses differs among plant functional groups and the plant’s ecological niche.

How to cite: Basler, D., Nelson, D. B., de Vos, J., Moreno-Gutiérrez, C., and Kahmen, A.: Long-term physiological responses of herbaceous plants to global change from carbon and oxygen isotopes in herbarium specimen, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12998, https://doi.org/10.5194/egusphere-egu23-12998, 2023.

EGU23-14059 | Posters on site | BG2.3

Unlocking the physiological and climatic hydrogen isotope signal in tree rings and leaf n-alkanes in a boreal forest 

Charlotte Angove, Marco Lehmann, Matthias Saurer, Guido Wiesenberg, Giles Young, and Katja Rinne-Garmston

It is essential to comprehensively understand past climate and tree response to climate change because trees are directly exposed to rapid, intensifying, and widespread climate change. Both tree rings and leaf n-alkanes are long-term biomarkers which can help to better understand past climate and/or tree response to climate change. For example, interpreting carbon and oxygen stable isotopes in tree rings contribute to understanding past climate and tree response to climate change. However, greater insight could be achieved if hydrogen stable isotopes can also be clearly interpreted. To clearly interpret hydrogen isotopes in tree rings it is necessary to discover which aspects of climatic variability and tree physiology are most clearly expressed by hydrogen isotopes in tree rings. Additionally, the climatic signal of hydrogen stable isotopes in leaf n-alkanes can be deposited to soil and sediments from plants, and their climatic soil record can date back to thousands to millions of years ago. However, there are still aspects of plant physiology that have not been accounted for in leaf n-alkane hydrogen isotope interpretation, which limits the reliability of their interpretation. While data from tree rings and leaf n-alkanes are rarely combined, both tree rings and leaf n-alkanes contain a hydrogen isotope signal that originates from a hydrogen isotope signal in source water that is changed by physiological processes and interacting climatic factors during their biosynthesis. This project aims to improve our understanding of the physiological and climatic signals contained in the hydrogen isotope signal in both tree rings and leaf n-alkanes. It helps increase the useability of the hydrogen isotope signal in tree rings and helps improve the reliability of interpreting climatic signals from leaf n-alkanes. It uses a unique dataset from a field survey with samples collected multiple times during a growing season, with high temporal resolution, at one to two boreal forests in southern Finland (e.g., Leppä et al. 2022; Tang et al., 2022). This dataset is rich with information from multiple sources, such as multiple element isotope concentrations in various plant tissues and water isotope pools, as well as leaf gas exchange data, meteorological data, and eddy covariance data. The hydrogen isotope signal is traced from the climatic signal in source water, to the physiological and climatic signal in leaf water, sugars and starches and leaf n-alkanes, then from the same leaf water, sugars, and starches to bark and stem phloem sugars and starches, to high-resolution intra-annual tree ring α-cellulose. This presentation gives the project outline and some main findings.

Leppä et al. (2022) doi:10.1111/nph.18227

Tang et al. (2022) doi: 10.1093/treephys/tpac079

How to cite: Angove, C., Lehmann, M., Saurer, M., Wiesenberg, G., Young, G., and Rinne-Garmston, K.: Unlocking the physiological and climatic hydrogen isotope signal in tree rings and leaf n-alkanes in a boreal forest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14059, https://doi.org/10.5194/egusphere-egu23-14059, 2023.

EGU23-14146 | ECS | Posters on site | BG2.3

A new solid phase extraction method for purifying plant sugars for compound-specific hydrogen isotope analysis 

Selina Hugger, Meisha Holloway-Phillips, Ansgar Kahmen, and Daniel B. Nelson

As plant organic compounds are formed, their hydrogen isotopic composition (δ2H) is influenced by the hydrology of the environment as well as by the plant metabolism, and hence contains information about both. Until recently, cellulose has been the only plant carbohydrate routinely measured, because it persists in tissues over long time scales and can therefore be used to understand time-integrated signals preserved in tissues like tree rings. However, knowledge gaps about how environmental and metabolic signals are imprinted in the cellulose δ2H value currently limit the interpretation of cellulose δ2H variation with respect to plant metabolism. Measuring δ2H values of biosynthetic intermediates like sugar molecules from fresh tissue offers a possibility of filling some of these knowledge gaps to better understand the cellulose δ2H signal.

Measuring δ2H values in carbohydrates is complicated by the presence of hydroxyl hydrogen. This is because this hydrogen pool can isotopically exchange with surrounding liquid water or water vapor (e.g., during sample processing and analysis), obscuring the primary plant hydrological and metabolic information contained in the isotopic values of carbon-bound hydrogen. The contribution of exchangeable hydrogen can be accounted for using dual equilibration techniques, but in most cases, these permit only analyses of bulk leaf extracted sugars. Thus, another difficulty lies in obtaining individual sugar compounds from plants. An alternative to dual equilibration is therefore to derivatize the plant sugars prior to analysis with hydrogen of known isotopic composition to form new compounds that no longer contain exchangeable hydrogen, e.g., by acetylation. Acetylation makes sugar compounds amenable to gas chromatography (GC), so this technique also allows for compound-specific analyses of multiple compounds in the same sample, such as different sugar types. GC analysis also has the advantages of requiring smaller sample amounts and providing better assurances of sample purity than are possible for bulk sample measurement approaches.

Here, we present results on streamlining our acetylation approach to facilitate rapid and cost-effective purification from sample matrices of water-soluble plant carbohydrate extracts. We acetylate whole carbohydrate extracts, and then compare recovering sugar acetates from the sample matrix by liquid-liquid separation with recovery by reverse-phase solid phase extraction (SPE) using a C18 sorbent. The liquid-liquid separation yields a higher recovery than SPE but is much more labor-intensive, whereas the SPE method can be scaled easily for higher sample throughput. Both methods proved successful for purifying water-soluble sugar samples as well as digested starch (glucose) from plant leaf, wood, and root material, yielding GC amenable sugar acetates that are soluble in acetone. Sucrose octaacetate is well resolved under normal GC measurement conditions on commonly available GC columns (e.g., DB-5), without requiring instrument modification as is the case for halogenated sample compounds.

How to cite: Hugger, S., Holloway-Phillips, M., Kahmen, A., and Nelson, D. B.: A new solid phase extraction method for purifying plant sugars for compound-specific hydrogen isotope analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14146, https://doi.org/10.5194/egusphere-egu23-14146, 2023.

EGU23-14386 | Orals | BG2.3

Terrestrial and aquatic leaf wax hydrogen isotope proxy system models: Recent advances and remaining gaps 

Elizabeth Thomas, Allison Cluett, Owen Cowling, Devon Gorbey, Kayla Hollister, Sofia Kjellman, and Kurt Lindberg

Constraining the hydrological response to past climate change can improve climate model predictions. These constraints are most useful when provided in variables that are native to climate models (e.g., precipitation or soil water isotope values during a defined season). Leaf wax hydrogen isotopes extracted from lake sediments are valuable proxies to reconstruct the hydrological cycle. In some lakes, multiple leaf wax compounds may provide information about different aspects of the climate system (e.g., precipitation isotope seasonality, growing season evaporation, etc.), increasing the amount of information we obtain from a single measurement. Yet, the pathway by which climate signals are recorded in leaf wax hydrogen isotopes can be complex, as the isotope signal is filtered through the environment (lake or soil water) and the sensor (integrating waxes from aquatic plants and from terrestrial plants throughout the lake’s catchment). This presentation will summarize our recent and ongoing research examining how climate signals are filtered through both the environment and sensor, with the goal of providing reconstructions in terms native to isotope-enabled climate models. We will highlight studies examining lake water isotope systematics and leaf wax sources to lake sediments, emphasizing aspects of these frameworks that are applicable to other stable water isotope proxies. We will also discuss outstanding questions and avenues for future research.

How to cite: Thomas, E., Cluett, A., Cowling, O., Gorbey, D., Hollister, K., Kjellman, S., and Lindberg, K.: Terrestrial and aquatic leaf wax hydrogen isotope proxy system models: Recent advances and remaining gaps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14386, https://doi.org/10.5194/egusphere-egu23-14386, 2023.

Plant organic compounds such as cellulose or n-alkanes are often utilized as recorders of oxygen (δ18O) or hydrogen (δ2H) isotopic signals to inform on past climate or environmental conditions, or on plant physiological changes. This is because these compounds can persist in the geologic record for decades to millennia or longer in select cases. Yet, large differences have often been observed among plant organic compound δ2H or δ18O values for species growing in a single location due to the balance between variable leaf water isotopic enrichment and variable biochemical isotopic effects among species. Distinguishing between these sources of variability and making use of these signals is an ongoing challenge, in part because of the limited number of studies that have explored the extent to which the different drivers influence the isotopic composition of each compound class and element within a single location.

We present a detailed assessment of isotopic variation in relevant plant water pools and cellulose δ2H and δ18O values, in combination with n-alkane δ2H values in 192 eudicot species grown in a botanical garden in a single growing season, as well as year-to-year comparisons for consecutive years (2019-2020). Our results show that variation in leaf water δ2H values were not a strong driver for the observed variation in organic compound δ2H values across eudicot species. Additionally, while correlation between δ2H and δ18O values found in plant source water and leaf water was transferred to cellulose, the explanatory power of this correlation was strongly diminished. This indicates that additional biochemical isotope fractionation caused substantial variation in organic compound δ2H and/or δ18O values across species. Moreover, variation in cellulose δ2H values were poorly correlated with δ2H values from n-alkanes, suggesting that the biochemical pathways associated with different compounds were accompanied by varying isotope effects. Lastly, cellulose δ2H and δ18O values changed more than n-alkane δ2H values from one year to the next. This implies that, cellulose δ2H and δ18O values are more sensitive to environmental differences between growing seasons compared to δ2H values from n-alkanes, and thus that the environmental forcing effects on isotope values are not equal between compounds. Overall, we found that variation in organic compound δ2H, and possibly also δ18O, values across species and between growing seasons was substantially more strongly driven by biochemical isotope fractionation than by isotope values of plant water. Therefore, to the extent that it is possible, biochemical responses to environmental changes should be considered in interpretations of organic compound δ2H and δ18O values to reconstruct the past. Furthermore, there is potential to recover plant responses to environmental changes from plant organic compound δ2H and/or δ18O values when the measurements are incorporated into multi-compound or multi-proxy paleoenvironmental and paleophysiological inquiries.

How to cite: Nelson, D. B., Baan, J., Holloway-Phillips, M., and Kahmen, A.: Biochemically driven isotope effects differ for n-alkane hydrogen and for cellulose hydrogen and oxygen among eudicot plant species and between years, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15357, https://doi.org/10.5194/egusphere-egu23-15357, 2023.

EGU23-16142 | ECS | Posters on site | BG2.3

Investigating the "mixoplankton" paradigm using hydrogen isotope ratios 

Marc-Andre Cormier, Jean-Baptiste Berard, Kevin Flynn, Gael Bougaran, and Rosalind Rickaby

Since micro-organisms were first visualised by Robert Hooke and Antoni van Leeuwenhoek, bacteria and protists were quickly categorised as either primary producers or consumers and thus forming the base of the marine food web. New conceptual understanding sees this traditional dichotomy between autotrophs and heterotrophs in the marine food web replaced by one that recognises that mixotrophy is widespread. Many "phytoplankton" eat, while 50% of "microzooplankton" perform photosynthesis. This mixotrophic behaviour affects the cycling of nutrients, enhances primary production, biomass transfer to higher trophic levels, and the marine sequestration of atmospheric CO2. Moreover, the mixotrophic behaviour of many toxic protists could also be partly responsible for their ecological success and the occurrence of Harmful Agal Blooms (HABs).

While science requires a tool to measure the contributions of phototrophy and heterotrophy in plankton to help in biogeochemical modelling, my colleagues and I have already shown that hydrogen (H) isotopic signature (i.e. d2H) of lipids is uniquely sensitive to the expression of heterotrophy relative to photosynthesis in terrestrial plants and bacteria. This presentation will discuss groundwork experiments performed with Chlorella sorokiniana, Prymnesium parvum and Emiliania huxleyi that had for objective to explore whether d2H values of diverse compounds produced by protists are similarly sensitive to their central metabolic pathway. Hydrogen isotope analyses performed on organic compounds from these experiments, using an isotope ratio mass spectrometer (IRMS) coupled to a gas chromatograph (GC), suggest that H isotopic signature of lipids is indeed sensitive to the level of heterotrophic growth in diverse protists.

If this relation can be confirmed and calibrated, compound specific hydrogen isotope analyses could provide a powerful means to study the role of mixotrophy on the global carbon cycle, the cycling of nutrients and the occurrences of HABs.

How to cite: Cormier, M.-A., Berard, J.-B., Flynn, K., Bougaran, G., and Rickaby, R.: Investigating the "mixoplankton" paradigm using hydrogen isotope ratios, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16142, https://doi.org/10.5194/egusphere-egu23-16142, 2023.

EGU23-16430 | Orals | BG2.3

Paleohygrometry and reconstruction of lake evaporation history based on compound-specific hydrogen and oxygen isotope analyses of biomarkers – principle of the coupled isotope approach, advances and limitations 

Michael Zech, Johannes Hepp, Mario Tuthorn, Bruk Lemma, Lucas Bittner, Roland Zech, Kazimierz Rozanski, and Bruno Glaser

The oxygen and hydrogen isotopic composition δ2H and δ18O of leaf and lake water reflects the isotopic composition of source water/precipitation modified by evapo(transpi)rative enrichment. This later enrichment can be illustrated and quantified using δ2H- δ18O diagrams and the deuterium-excess. The enrichment of leaf water thereby depends primarily on relative air humidity (RH) and can be investigated using biomarkers being produced in leaves. The enrichment of lake water depends on lake evaporation and can be investigated using biomarkers being produced by aquatic macrophytes or algae. Provided that unambiguous terrestrial and aquatic biomarkers can be identified in lake sediments, the coupling of δ2H and δ18O hence allows reconstructing RH (paleohygrometry approach) and lake evaporation history. In our contribution, we discuss the potential, the advances and the limitation of the coupled isotope approach based on leaf wax-derived n-alkane and hemicellulose-derived sugar biomarkers (δ2Hn-alkanes-  δ18Osugars).

 

References

Hepp, J., Mayr, C., Rozanski, K., Schäfer, I., Tuthorn, M., Glaser, B., Juchelka, D., Stichler, W., Zech, R. and Zech, M., 2021. Validation of a coupled δ2Hn-alkane18Osugar paleohygrometer approach based on a climate chamber experiment. Biogeosciences 18, 5363-5380.

Hepp, J., Wüthrich, L., Bromm, T., Bliedtner, M., Schäfer, I. K., Glaser, B., Rozanski, K., Sirocko, F., Zech, R., and Zech, M., 2019. How dry was the Younger Dryas? Evidence from a coupled δ2H-δ18O biomarker paleohygrometer applied to the Lake Gemündener Maar sediments, Western Eifel, Germany, Climate of the Past 15, 713-733.

Zech, M., Tuthorn, M., Detsch, F., Rozanski, K., Zech, R., Zöller, L., Zech, W. and Glaser, B., 2013. A 220 ka terrestrial δ18O and deuterium excess biomarker record from an eolian permafrost paleosol sequence, NE-Siberia. Chemical Geology 360-361, 220-230.

How to cite: Zech, M., Hepp, J., Tuthorn, M., Lemma, B., Bittner, L., Zech, R., Rozanski, K., and Glaser, B.: Paleohygrometry and reconstruction of lake evaporation history based on compound-specific hydrogen and oxygen isotope analyses of biomarkers – principle of the coupled isotope approach, advances and limitations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16430, https://doi.org/10.5194/egusphere-egu23-16430, 2023.

Stable hydrogen isotope may provide evidence to identify the botanical origin of exogenous sugars added to honey, due to a combination of factors such as the systematic global variation of meteorological waters and morphological differences affecting rates of evapotranspiration prior to water incorporation into plant carbohydrate prior to photosynthesis. Here we report an simplified method, which involves the preparation of hexamethylenetetramine (HMT), produced through chemical transformation of sugar molecules, to allow direct analysis of the carbon-bound non-exchangeable hydrogen (CBNE) by elemental analyser high temperature chromium reduction coupled to Isotope Ratio Mass Spectrometry (EA-Cr/HTC-IRMS). We have optimized the reaction conditions for oxidation and derivatisation in terms of reaction time and pH of solution. A two month-monitoring for of the repeatability of δ2H values of an HMT standard  has demonstrated stable and reliable results of this technique. The procedure is relatively straightforward, convenient and easy to apply compared with alternative reported CBNE analysis methods for foodstuffs, particularly those where isolating sugars is challenging and consensus over dual-water equilibration conditions are contentious.  Moreover, it has the advantage over other methods by avoiding the use of corrosive and explosive reagents such as sugar nitro-derivatives.  This study has also demonstrated the potential to identify from the presence of rice syrup, which is currently a significant challenge for the honey industry.

How to cite: Li, A., Abrahim, A., and Kelly, S.: Stable Isotope Analysis of Non-exchangeable Hydrogen in Sugars by Oxidation/Derivatisation to hexamethylenetetramine and Elemental Analyzer-Chromium/High Temperature Conversion- Isotope Ratio Mass Spectrometry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16499, https://doi.org/10.5194/egusphere-egu23-16499, 2023.

Polysaccharides, e.g. starch, are the most abundant biopolymers on earth. They are long chain monosaccharides linked by glycosidic bonds and are playing different important roles in plants such as energy storage (e.g. starch and glycogen) structure and growth (e.g. cellulose and pectin).The determination of carbon bound non-exchangeable (CBNE) hydrogen isotope ratios in polysaccharides are of great interest in a broad range of research areas, as they contain intrinsic information about the metabolic pathway and geographical origin of the plant, derived from water incorporated during photosynthesis. Measuring non-exchangeable hydrogen isotope ratios in starch is challenging using methods such as the dual water-equilibration technique, which are labour intensive and open to a certain degree of contention of over equilibration times, temperatures, proportions of exchangeable hydrogen and fractionation factors. We report on a new approach, to determine non-exchangeable hydrogen isotopes in starch, after hydrolysis of the biopolymer into monosaccharides followed by conversion into volatile trifluoroacetamide (TFA) derivatives and analysis by GC-CrAg/HTC-IRMS.

This new methodology (Figure.01) is rapid and simple compared to current available methods and should allow CBNE hydrogen isotope analysis to be more easily and widely used.

 

How to cite: Abrahim, A. and Kelly, S.: Determination of carbon bound non-exchangeable (CBNE) hydrogen isotope ratios in starch by Microwave Assisted Hydrolysis (MAH) and GC-CrAg/HTC-IRMS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16747, https://doi.org/10.5194/egusphere-egu23-16747, 2023.

EGU23-17216 | Posters on site | BG2.3

DOH! – The interface of isotope hydrology, ecology, and organic geochemistry 

Travis Blake Meador, Stanislav Jabinski, Anna Mičanová, Niclas Zehetner, Karelys Umbria-Salinas, Matthias Pilecky, and Leonard Wassenaar

Dissolved organic matter (DOM) cycling is essential to understanding energy flow in aquatic ecosystems and their role as a source or sink of CO2 in the global carbon cycle. Quantifying DOM turnover and reactivity have been confounded by the barely detectable changes in the molecular composition and 13C & 15N stable-isotope compositions. We hypothesized that significant seasonal isotopic changes in environmental waters and primary biological productivity might be reflected in the H & O stable-isotope composition of DOM, providing an alternative way to assess the accumulation, turnover, and transport of DOM in aquatic environments. H & O stable-isotope analyses of DOM from lakes showed temporal coupling of water isotopes with organic molecules that accumulate in natural aquatic environments, which varied between catchments and by molecular size components of DOM. An in-situ stable-isotope labelling (HDO) experiment revealed (microbial) turnover of DOM occurred on a weekly timescale. Further development of δ2H- and δ18O-DOM analyses may improve our understanding of the provenance and processing of DOM and help better constrain unknowns in the metabolic balance of inland waters.

How to cite: Meador, T. B., Jabinski, S., Mičanová, A., Zehetner, N., Umbria-Salinas, K., Pilecky, M., and Wassenaar, L.: DOH! – The interface of isotope hydrology, ecology, and organic geochemistry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17216, https://doi.org/10.5194/egusphere-egu23-17216, 2023.

Understanding biogeochemical processes in groundwater is paramount for safety management of our water supplies. The AquaDiva project has been investigating a groundwater probing site in central Germany to monitor hydrology, biology and dissolved organic matter (DOM) chemistry in a multiannual project (Küsel et al., 2016). As part of this, we are addressing how deep surface-derived signals can be traced on their passage through the critical zone and into the groundwater.

We acquired a multiannual DOM data set from an untargeted liquid chromatography coupled to mass spectrometry (LC-MS) monitoring and have previously shown that fingerprints from mass-signals associate with water flows (Zerfaß et al., 2022). Using tandem mass spectrometry, we have now identified DEET (N,N-diethyl-m-toluamide) and 7-ODAA (7-oxodehydroabietic acid, putative) in groundwater samples, compounds that are released to aerosols as insect repellent sprays and through conifer wood burning for heating, respectively. We show that these signals are found in groundwater throughout the year, but with elevated intensities in summer (DEET) and winter (7-ODAA), respectively, corresponding to their primary seasons of release.

This demonstrates by the counter-periodic DEET and 7-ODAA patterns how surface-derived (aerosol) organic matter signals arrive in groundwater down to 88 m of sampling depths with intra-annual dynamics.

 

References

Küsel, K., Totsche, K.U., Trumbore, S.E., Lehmann, R., Steinhäuser, C., Herrmann, M., 2016. How Deep Can Surface Signals Be Traced in the Critical Zone? Merging Biodiversity with Biogeochemistry Research in a Central German Muschelkalk Landscape. Front. Earth Sci. 4. https://doi.org/10.3389/feart.2016.00032

Zerfaß, C., Lehmann, R., Ueberschaar, N., Sanchez-Arcos, C., Totsche, K.U., Pohnert, G., 2022. Groundwater metabolome responds to recharge in fractured sedimentary strata. Water Res. 223, 118998. https://doi.org/10.1016/j.watres.2022.118998

How to cite: Zerfass, C., Ueberschaar, N., and Pohnert, G.: Aerosols to groundwater: DEET (N,N-diethyl-m-toluamide) and 7-ODAA (7-oxodehydroabietic acid) as markers for anthropogenic emissions in the Hanich CZO, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1007, https://doi.org/10.5194/egusphere-egu23-1007, 2023.

EGU23-1634 | Posters on site | BG2.4

Quinone-Mediated Electrochemical Reduction of Ferrihydrite: Effect of Sorption and Redox Potential 

Guo-Xiang Li and Stefan B. Haderlein

Natural Organic Matter (NOM) shows both oxidizing and reducing capabilities through its quinone/hydroquinone functional groups and takes part in various geochemically redox reactions. Here four natural and synthetic quinone model compounds (anthraquinone-2,6-disulfonate, AQDS; anthraquinone-2-sulfonate, AQS; 2-hydroxyl-1,4-naphthoquinone, Lawsone; and anthraquinone-2,3-dicarboxylic acid, AQDC) were used to study the effect of adsorption of redox active organic matter on mediating ferrihydrite reduction. The studied quinone compounds varied regarding reduction potential and their tendency to adsorb at ferrihydrite. An electrochemical setup rather than iron reducing bacteria was used to circumvent potential inhibitory effects of the model quinones on microbial activity. Iron speciation, dissolved and adsorbed quinone concentrations and their redox state were monitored to elucidate controlling factors in mediated ferrihydrite reduction. Results show that all model quinones present at 100 µM total concentration enhanced the initial iron reduction rate of ferrihydrite, however, to very different extents. At -0.45 V (vs. Ag/AgCl) redox potential applied, the initial reduction rates increased compared to quinone free systems by factors of 62.53, 43.11, 32.26 and 2.91 for AQDS, AQS, Lawsone and AQDC, respectively. In contrast to AQDC and Lawsone, AQDS and AQS did not show significant adsorption at ferrihydrite under the conditions of our study. Due to the high sorption, the initial dissolved AQDC concentration was only 3.60 μM. The initial dissolved concentration of Lawsone was 85.70 µM and decreased further during ferrihydrite reduction. Adsorbed Fe(II) promoted the adsorption of Lawsone on ferrihydrite thereby decreasing the rate of iron reduction. Our findings demonstrate that the rate of ferrihydrite reduction correlated with dissolved quinone concentrations. As a result, AQDS and AQS showed the highest acceleration of ferrihydrite reduction. At the redox conditions applied (-0.45 V vs. Ag/AgCl) the fraction of reduced quinone species was higher for AQDS than for AQS, consistent with the higher efficiency of AQDS in mediating ferrihydrite reduction.

The possibility of conducting experiments at defined redox potentials and precisely controllable experimental conditions reveals the perspectives of an electrochemical setup for the investigation of biogeochemical redox reactions.

How to cite: Li, G.-X. and Haderlein, S. B.: Quinone-Mediated Electrochemical Reduction of Ferrihydrite: Effect of Sorption and Redox Potential, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1634, https://doi.org/10.5194/egusphere-egu23-1634, 2023.

EGU23-1987 | Orals | BG2.4 | Highlight

Molecular characterization of coral reef exometabolites 

Andreas Haas, Craig Nelson, Milou Arts, Benjamin Mueller, Ellen Hopmans, and Linda Kelly

Marine DOM constitutes one of the most complex chemical mixtures on earth containing hundreds of thousands of different compounds. In nearshore systems like coral reefs metabolites exuded by primary producers comprise a significant fraction of this marine DOM pool. To learn more about the chemical composition we performed untargeted molecular analysis of exudates released by coral reef primary producers (corals and algae) using liquid chromatography–tandem mass spectrometry. Of 10,568 distinct ion features recovered from reef waters, 1,667 were primary producer exudates; the majority (86%) of these exudates were organism specific, reflecting a clear divide between coral and algal exometabolomes. The stoichiometric analyses of the exudates revealed a significantly reduced nominal carbon oxidation state of algal- compared to coral exometabolites, illustrating an ecological mechanism by which algal phase shifts engender fundamental changes in the biogeochemistry of reef biomes. Coral exometabolomes were enriched in diverse sources of nitrogen and phosphorus, including tyrosine derivatives, oleoyltaurines, and acyl carnitines. In contrast DOM released by algae was dominated by nonnitrogenous compounds, including diverse prenol lipids and steroids. Additional experiments indicate that exudates, specifically exudates unique to the respective treatment, were the main substrate used by heterotrophic microbes exposed to the respective exometabolome. This data provides molecular-level insights into biogeochemical cycling on coral reefs and illustrates how changing benthic cover on reefs influences reef water chemistry with implications for microbial metabolism.

How to cite: Haas, A., Nelson, C., Arts, M., Mueller, B., Hopmans, E., and Kelly, L.: Molecular characterization of coral reef exometabolites, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1987, https://doi.org/10.5194/egusphere-egu23-1987, 2023.

EGU23-2572 | ECS | Posters on site | BG2.4

Dissolved organic matter characteristics and composition of small saline lakes in the Badain Jaran Desert, China 

Qiang Zhang, Yinghui Wang, Xiaolang Zhang, Hailong Li, Jiu Jimmy Jiao, Qinglong Fu, and Junjian Wang

Elucidating the characteristics and molecular composition of dissolved organic matter (DOM) is critical to understanding carbon cycling in increasingly saline lakes in arid and hyper-arid areas; however, the ages and molecular signatures of DOM in these widely distributed saline lakes remain poorly understood. Here, variations in DOM ages and other characteristics with salinity were investigated across 10 small saline lakes within the Badain Jaran Desert based on 14C-isotopic analysis, absorption and fluorescence spectroscopy, in addition to Fourier transform ion cyclotron resonance mass spectrometry. The results showed that brine lakes had dissolved organic carbon (DOC) levels 3-fold higher than brackish lakes, and the 14C age of DOC in brine lakes was twice as old. Compared to brackish lake DOM, brine lake DOM had more significant signatures of microbial contributions, as indicated by the higher fluorescence index values and greater relative abundances of microbial humic-like fluorescent components, in addition to sulfur-containing compounds. Moreover, brine lakes showed lower relative abundances of aromatic lignin-like components, as well as higher relative abundances of lipid- and condensed-aromatics-like components. Regarding halogen-containing DOM, the brine lakes showed higher abundances of halogen-containing lignin- and lipid-like components, supporting the preferential transformation of aromatic compounds into halogenated lignin- and lipid-like components. This study demonstrates the strong impacts of salinization on DOM aging, accumulation, and halogenation in inland saline lakes and highlights the critical role of brine lakes as a persistent carbon pool.

How to cite: Zhang, Q., Wang, Y., Zhang, X., Li, H., Jiao, J. J., Fu, Q., and Wang, J.: Dissolved organic matter characteristics and composition of small saline lakes in the Badain Jaran Desert, China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2572, https://doi.org/10.5194/egusphere-egu23-2572, 2023.

EGU23-2631 | ECS | Posters on site | BG2.4 | Highlight

Erosion regime controls sediment eDNA-based community reconstruction 

Marina A. Morlock, Saúl Rodriguez-Martinez, Doreen Yu-Tuan Huang, and Jonatan Klaminder

Environmental DNA (eDNA) analysis from lake sediments shows promise to become a great paleoecological technique. Nevertheless, our knowledge regarding catchment processes that influence the eDNA signal preserved in sediments creates uncertainties when interpreting temporal changes in reconstructed biodiversity. Are changes in species composition the result of ‘real’ changes in species abundances or simply the result of altered DNA transport processes in the catchment?

In this presentation, we investigate the role of erosion for sediment eDNA-based reconstructions. We utilize sediment records from the Central Alps and compare the plant and mammal DNA pools in lake sediments of similar age but deposited under different erosion regimes: detrital event layers formed during heavy precipitation events vs. hemi-pelagic background sedimentation.

We find strong differences in the reconstructed plant and mammal communities both across space and time. Temporal changes across the Holocene were the main drivers of change for reconstructed plant communities, but sediment type -and thus erosion regime- was the second most important factor of variance. Around 30% of all plant and mammal taxa were uniquely detected in event layers. Our results highlight that the two sediment types preserved their unique assembly of plant and animal DNA, suggesting that post-depositional mobility of terrestrial DNA is insignificant on Holocene timescales. However, our results also highlight the challenge when attributing changes in erosion regimes to the appearance of new species in an eDNA-based paleo-record because increased erosion will also increase the representation of taxa already present in the lake’s catchment. In our case, this mechanism was an important factor for DNA-inferred species composition and taxonomic richness recorded in the sediments.

How to cite: Morlock, M. A., Rodriguez-Martinez, S., Huang, D. Y.-T., and Klaminder, J.: Erosion regime controls sediment eDNA-based community reconstruction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2631, https://doi.org/10.5194/egusphere-egu23-2631, 2023.

EGU23-2837 | Orals | BG2.4

A temporal graph to predict chemical transformations in complex dissolved organic matter 

Oliver Lechtenfeld, Philipp Plamper, Peter Herzsprung, and Anika Groß

Dissolved organic matter (DOM) is a complex mixture of thousands of natural molecules that undergo constant transformation in the environment, such as sunlight induced, photochemical reactions. Despite molecular level resolution obtained by ultra-high resolution mass spectrometry, the mechanistic understanding of DOM transformations is still hampered due to a multitude of simultaneous reactions. Temporal trends of mass peak intensities are currently the only way to follow photochemical induced molecular changes in DOM, but are often limited by low temporal resolution or the necessity to apply monotonic regression models. Here, we present a novel computational approach using a temporal graph (a temporal molecular network) to model the transformation of DOM molecules in a photolysis experiment by employing a predefined set of basic molecular transformation units (like oxidation, decarboxylation, etc.). The new algorithm focuses on the temporal changes of mass peak intensities of molecular formulas by simultaneously considering educt removal and product formation for molecules linked by a transformation unit (e.g. -CO2). The transformations and molecules are further weighted by the extent of intensity change and grouped by unsupervised machine learning algorithms to find clusters of similar reactivity. The temporal graph thus allows to simultaneously identify relevant molecules subject to similar reactions and to study their time course. The graph can be constructed for low and high temporal resolution data without presumptions on reaction kinetics and with different sets of transformation units according to the experimental design. Our approach overcomes previous data evaluation limitations for mechanistic studies of DOM transformation and leverages the potential of temporal graphs to study the reactivity of complex DOM by means of ultra-high resolution mass spectrometry.

How to cite: Lechtenfeld, O., Plamper, P., Herzsprung, P., and Groß, A.: A temporal graph to predict chemical transformations in complex dissolved organic matter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2837, https://doi.org/10.5194/egusphere-egu23-2837, 2023.

The organic-rich mudstones and dolostones of the Permian Fengcheng Formation (Fm.) are typically alkaline lacustrine source rocks, which are typified by impressively abundant β-carotane. Abundant β-carotane has been well acknowledged as an effective indicator of biological sources or depositional environments. However, the coupling control of biological precursors and environmental factors on the enrichment of β-carotane in the Fengcheng Fm. remains obscure. Based on a comprehensive investigation of the bulk and molecular geochemistry of sedimentary rocks and the biochemistry of phytoplankton in modern alkaline lakes, we proposed a new understanding of the biological precursors of β-carotane and elucidated the coupling control of biological precursors and environmental factors on the enrichment of β-carotane in the Fengcheng Fm. The results show that the biological precursors crucially control the enrichment of β-carotane in the Fengcheng Fm. The haloalkaliphilic cyanobacteria are the primary biological sources of β-carotane, which is suggested by a good positive correlation between 7-+8- methyl heptadecanes/Cmax and β-carotane/Cmax in sedimentry rcoks and the predominance of cyanobacteria with abundant β-carotene in modern alkaline lakes. Land plants and algae do not significantly contribute to the enrichment of β-carotane, which is indicated by negative or weak correlations between terrigenous/aquatic ratio, C19 tricyclic terpene/C23 tricyclic terpene ratio, the concentration of C27 sterane, and β-carotane/Cmax. The environmental facors such as paleoclimate, paleoredox, paleosalinity, and thermal maturity are the indirect factors that control the enrichment of β-carotane by affecting the precursor supply from cyanobacteria and the preservation conditions in the Fengcheng Fm.

How to cite: Hou, M., Zha, M., and Liu, H.: The coupling control of biological precursors and environmental factors on β-carotane enrichment in alkaline lacustrine source rocks: a case study from the Fengcheng Formation in the western Junggar Basin, NW China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4100, https://doi.org/10.5194/egusphere-egu23-4100, 2023.

EGU23-4329 | ECS | Orals | BG2.4 | Highlight

Molecular signatures of soil-derived dissolved organic matter constrained by mineral weathering 

Yinghui Wang, Peng Zhang, Chen He, Quan Shi, Randy Dahlgren, Robert Spencer, and Junjian Wang

  Dissolved organic matter (DOM) in soil consists of a diverse mixture of water-soluble soil organic matter (SOM) molecules that are highly mobile and reactive. These molecules play various roles with different capacities in biogeochemical processes. Theoretically, the persistence of DOM molecules in soils is controlled by interactions between i) DOM leaching and desorption that release DOM from plant residues and SOM and ii) sorption and decomposition that remove DOM. However, there is still no consensus on the dominant factor(s) or dimension(s) driving the yield and molecular signatures of DOM in soil environments.

  Molecular variations of soil DOM from distinct geographical regions are primarily attributed to variations in geographical climate conditions and soil clay content. Soil weathering condition is highly related to geographical climate conditions, such as temperature and precipitation, and could be a reflection of the soil mineral characteristics. However, there is a distinct paucity of information concerning how the molecular signatures of soil DOM vary with different degrees of weathering across wide geographic scales.

  Herein, we resolved the DOM molecular signatures from 22 diverse Chinese reference soils and linked them with soil organic matter and weathering-related mineralogical properties. The mixed-effects models revealed that the yields of DOM were determined by soil organic carbon content, whereas the molecular signature of DOM was primarily constrained by the weathering-related dimension. The soil weathering index showed a positive effect on the lability and a negative effect on the aromaticity of DOM. Specifically, DOM in highly weathered acidic soils featured more amino sugars, carbohydrates, and aliphatics, as well as less O-rich polyphenols and condensed aromatics, thereby conferring a higher DOM biolability and lower DOM aromaticity. This study highlights the dominance of the weathering-related dimension in constraining the molecular signatures and potential functions of DOM in soils across a wide geographic scale.

How to cite: Wang, Y., Zhang, P., He, C., Shi, Q., Dahlgren, R., Spencer, R., and Wang, J.: Molecular signatures of soil-derived dissolved organic matter constrained by mineral weathering, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4329, https://doi.org/10.5194/egusphere-egu23-4329, 2023.

The vital role played by soil microbial communities, including bacteria, fungi, and other microorganisms, in the provision of several essential terrestrial ecosystem services cannot be overstated. To gain a more comprehensive understanding of their multifaceted ecosystem services, it is essential to identify and examine the functional role of these microbial communities and of the pathways by which they facilitate soil organic matter and plant necromass decomposition and nutrient cycling. The determination of microbial community composition in soils, and extending this to the complex decomposer soil food web, has remained a significant challenge. To address this challenge, various techniques such as 16S and 18S rRNA gene sequencing and phospholipid fatty acid (PLFA)-based biomarker analysis have been applied. While PLFA analysis has been used to characterize these communities for over three decades, recent advancements in liquid chromatography (LC) and high-resolution mass spectrometry (HRMS) now enable comprehensive analysis of the soil lipidome based on intact polar lipids, providing greater though unknown opportunities to discover biomarkers of soil microbes and other food web members. In light of this, we developed an untargeted lipidomics workflow using reverse phase liquid chromatography and electrospray ionization tandem mass spectrometry (RPLC ESI MSMS) for the analysis of lipidomes in soil and pure cultures of archaeal, bacterial, and fungal organisms, to be extended to soil fauna and plants. This workflow includes techniques for the rapid and accurate identification and quantification of lipid molecules in complex samples, utilizing internal standards, quality control strategies, Orbitrap based instrument setups, and an advanced data processing pipeline. Key features of the pipeline include compound annotation for unknowns based on SMILES generation, retention time prediction, feature-based molecular networking, as well as the relative quantification of these compounds using ionization efficiency prediction models. The developed method was capable of analyzing and identifying over 2000 unique intact polar lipid molecules from more than 12 classes in a variety of samples, covering Archaea, Gram-positive and Gram-negative bacteria, fungi, arthropods, algae and higher plants. Thus, our method can provide valuable insights into the complex and diverse soil food web by accurately identifying and quantifying a wide range of intact polar lipid molecules and further can be used for biomarker analysis and isotope tracing in soil microbial communities.

How to cite: Samrat, R. and Wanek, W.: Soil Lipidomics: A LC-MS/MS based workflow with advanced data processing for biomarker discovery in soil communities, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6106, https://doi.org/10.5194/egusphere-egu23-6106, 2023.

EGU23-6233 | Posters on site | BG2.4

Thermal maturity and depositional conditions in the Orava part of Central Carpathian Palaeogene Basin 

Leszek Marynowski, Dorota Staneczek, and Dariusz Więcław

Central Carpathian Palaeogene Basin (CCPB) is a wedge-top basin that opened in the Central Western Carpathians in Lower Palaeogene. Orava sub-basin (OSB), located in N-Slovakia, comprises the NW remnants of CCPB. Based on previous studies (Środoń et al., 2006), OSB is the least mature part of CCPB. Yet, the estimated palaeotemperatures are relatively high and reach 95-100oC. Obtained results based on biomarkers study show differences in thermal maturity depending on the location of sampling sites and lithostratigraphy. Generally, maturation increases from N to S and Biely Potok (Upper Oligocene) to Huty Fm (Lower Oligocene). The occurrence of ββ-hopanes, hopenes, oleanenes, and low values of 22S/(22S+22R) homohopane ratio (~0.4), as well as 20S/(20S+20R) sterane ratio (~ 0.1 - 0.2), suggests low thermal maturity of organic matter in N and NE part of OSB. On the contrary, the S part is characterized by relatively high values of 22S/(22S+22R) ratio (>0.5), the 20S/(20S+20R) ratio (>0.4) and lack of unsaturated compounds, indicating that these units have reached the oil window stage. Rock-Eval analysis reveals the dominance of III-type kerogen in both Lower and Upper Oligocene due to terrestrial organic matter input. Biomarkers of terrestrial origin were detected in all samples including both angiosperm and gymnosperm affinity. Moreover, in less mature samples perylene is present as one of the major compound. This compound is interpreted as derived from soil and/or wood degrading fungi (Marynowski et al., 2013). In the Lower Oligocene, dysoxic to euxinic depositional environments are prevalent, which is manifested by the occurrence of isorenieratane and its derivatives, as well as small (<5µm) pyrite framboid diameters in many samples. However, a change of sedimentary conditions to oxic/dysoxic was found in Upper Oligocene samples. The results show larger framboid diameters (>5µm), a lack of isorenieratane and homohopanes with more than 33 carbon atoms in the molecule. In summary, sedimentary conditions in the Oligocene of CCPB changed from predominantly anaerobic to aerobic, with increased input of terrestrial organic matter.

 

This work was supported by the National Science Centre, Poland (grant 2018/31/B/ST10/00284 to LM).

 

Środoń, J., Kotarba, M., Biroń, A., Such, P., Clauer, N., Wojtowicz, A., 2006. Diagenetic history opf the Podhale-Orava Basin and the underlying Tatra sedimentary structural units (Western Carpathians): evidence from XRD and K-Ar of illite-smectite. Clay Miner. 41, 751–774.

Marynowski, L., Smolarek, J., Bechtel, A., Philippe, M., Kurkiewicz, S., Simoneit, B.R.T. 2013. Perylene as an indicator of conifer fossil wood degradation by wood-degrading fungi. Org. Geochem. 59, 143–151.

How to cite: Marynowski, L., Staneczek, D., and Więcław, D.: Thermal maturity and depositional conditions in the Orava part of Central Carpathian Palaeogene Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6233, https://doi.org/10.5194/egusphere-egu23-6233, 2023.

EGU23-7912 | ECS | Posters on site | BG2.4

Tag jumping may produce major distortion of paleoecological reconstructions derived using metabarcoding approaches 

Saúl Rodriguez-Martinez, Marina Morlock, Doreen Y-T. Huang, and Jonatan Klaminder

Abstract

Analysis of DNA fragments preserved in natural archives, such as lake sediments and buried soil layers, has increased our understanding of past environments and their organism communities.  High throughput sequencing of genetic material from these matrixes and the linkage of DNA barcode databases (e.g. metabarcoding) has played, and still play, an important role for palaeoecological reconstructions. Yet, scrutinization of results derived using metabarcoding approaches – methods that fairly recently have become common within environmental science – is critical. Tag jumping is a process where sample-specific labels (tags), added to DNA sequences to allow identification of individual samples in a pooled DNA library, are unintentionally changed during sampling handling (during the end repair step). If occurring, tag jumping can result in DNA sequences being associated with the wrong sample. Nevertheless, tag jumping is rarely discussed within the paleoecological community, and the importance of the process remains largely unquantified.

Using example datasets from lake sediments and soils, we assessed the impact of tag jumping on metabarcoding data and how it affects paleo-reconstructions. We find that tag jumping can lead to substantial false positive detection of taxa in sedimentary samples. That tag jumping generated a very characteristic topological sample cross-contamination pattern allowed us to estimate that up to 80% of data in some data sets was distorted by this process(Rodriguez‐Martinez et al., 2023). We further compared a set of sedimentary DNA samples processed according to commonly applied, tag-jumping sensitive protocols with the same set of samples processed following a tag jumping free protocol. Our results suggest that tag jumping can affect paleoecological interpretations by: i) masking significant environmental change at a Holocene time-scale by making samples more similar; and; ii) adding species to sediment samples where they were not originally present (false positive detections). Our data clearly shows that tag jumping can represent a major source of bias for paleoecological reconstructions based on metabarcoding techniques. Importantly, the problem is easily circumvented if the right protocols are used.

 

References

Rodriguez‐Martinez, S., Klaminder, J., Morlock, M.A., Dalén, L., Huang, D.Y., 2023. The topological nature of tag jumping in environmental DNA metabarcoding studies. Mol. Ecol. Resour. 1755–0998.13745. https://doi.org/10.1111/1755-0998.13745

How to cite: Rodriguez-Martinez, S., Morlock, M., Huang, D. Y.-T., and Klaminder, J.: Tag jumping may produce major distortion of paleoecological reconstructions derived using metabarcoding approaches, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7912, https://doi.org/10.5194/egusphere-egu23-7912, 2023.

EGU23-8125 | Posters on site | BG2.4

Insights into NOM quality changes by combination of easy designed experiments close to nature and monitoring using FT-ICR-MS 

Peter Herzsprung, Wolf von Tümpling, Norbert Kamjunke, and Oliver J. Lechtenfeld

Natural organic matter (NOM) is often still a black box considering its isomeric composition. From the analytical point of view the highest resolution of NOM can be achieved by Fourier-transform ion cyclotron resonance mass spectroscopy (FT-ICR-MS). This analytical tool generates elemental compositions of thousands of NOM components (molecular formulas, MFs) which can be extracted from aqueous samples (e.g., via solid phase extraction) and which are ionizable (e.g. via electrospray ionization). The comparison of NOM quality in waters of different ecosystems has generated useful insights about ecosystem-specific molecular differences. However, NOM is not an inert mixture of compounds and can undergo chemical changes by photochemical or microbial reactions or adsorptive fractionation. By following the relative intensity changes of single MFs during simple experiments close to nature or monitoring, elucidation of the reactivity of the underlying NOM compounds is possible.

We have combined a photochemical degradation experiment close to nature with monitoring results from two German drinking water reservoirs with the perspective to disentangle photochemical and microbial reactions in the reservoirs. Bacterial induced transformations were widely excluded in the photo degradation experiment by filtration of the sample water before irradiation. During the reservoir monitoring, both microbial and photochemical reactions can be suggested from relative intensity differences of single MFs during lake stratification (between epi- and hypolimnion). MFs show intensity changes both in the photo experiment and in the lake monitoring are regarded as photo labile or photo products. Those MFs with intensity differences only in the lake monitoring can be regarded as microbial reactive.

A great number of highly reactive MFs were found to be present in all samples of both the photo degradation experiment and the lake monitoring. MFs like C9H12O6, C10H14O6, C10H14O7, C11H16O5 were photo products, MFs like C20H16O14, C19H14O13, C18H12O12 were photo degraded. MFs like C10H10O7 and C9H10O7 could be suggested to be microbial products because they showed elevated intensity in epilimnetic waters but minor reactivity in the photo experiment.

Our studies (1, 2, 3) provide the attempt to follow NOM reactivity by visualization of single MFs relative intensities versus time and / or space.

1) Wilske, C.et al.,Water MDPI (2020) 12 (2).

2) Herzsprung P. et al., Environ. Sci. Technol. (2020), 54, 13556-13565

3) Wilske C. et al., Water MDPI (2021), 13, 1703.

How to cite: Herzsprung, P., von Tümpling, W., Kamjunke, N., and Lechtenfeld, O. J.: Insights into NOM quality changes by combination of easy designed experiments close to nature and monitoring using FT-ICR-MS, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8125, https://doi.org/10.5194/egusphere-egu23-8125, 2023.

EGU23-8474 | Posters on site | BG2.4

Sedimentary ancient DNA reveals plankton community shifts in subarctic western Bering Sea back to the Eemian interglacial 

Kathleen Stoof-Leichsenring, Stella Buchwald, Dirk Nürnberg, Lars Harms, and Ulrike Herzschuh

Understanding past ecosystems in the Arctic and subarctic oceans is important to project ecosystem development under enhanced warming. Sedimentary ancient DNA (sedaDNA) is a fantastic proxy providing information with sufficient taxonomic width and depth to comprehensively reconstruct past ecosystems. This study uses shotgun metagenomics of 42 sediment samples to decipher phyto- and zooplankton community changes over the last glacial-interglacial cycle back to the Eemian in the subarctic western Bering Sea. We aim to understand the sensitivity of plankton community composition to climate changes and its consequences on food web dynamics and carbon export. Our results indicate that micro- phytoplankton, like sea-ice associated diatoms, and cold-adapted chlorophytes, along with crustaceous zooplankton (copepods) dominated during the last glacial period. Contrarily, pico/nano-sized phytoplankton and the diatom family Chaetocerotaceae accompanied by heterotrophic protists and reduced abundance of copepods characterized the interglacial plankton communities. Further, we identified profound differences between the Holocene and Eemian. Particularly, the Holocene records a pronounced increase of pico-sized cyanobacteria, whereas in the Eemian, cold-water related taxa like Bathycoccaceae and Triparmaceae sub-dominate the community, supporting unique communities in both interglacials, challenging an analogy to future warming scenarios. In summary, our study shows evidence for a shift from micro-sized towards pico-sized phytoplankton with climate warming in the Holocene, accompanied by a more diverse zooplanktonic community dominated by bacterial grazing heterotrophic protists. Under future warming, decreased phytoplankton cell size and shifts in the grazing communities could affect food web linkages and result in reduced potential carbon sequestration and export in the subarctic Bering Sea, weakening its function as an effective carbon sink.

How to cite: Stoof-Leichsenring, K., Buchwald, S., Nürnberg, D., Harms, L., and Herzschuh, U.: Sedimentary ancient DNA reveals plankton community shifts in subarctic western Bering Sea back to the Eemian interglacial, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8474, https://doi.org/10.5194/egusphere-egu23-8474, 2023.

EGU23-8793 | ECS | Orals | BG2.4 | Highlight

Plant sedaDNA reveals grassland change on the Northeastern Tibetan Plateau during the past 17 ka 

Ying Liu, Kathleen Stoof-Leichsenring, Bernhard Diekmann, and Ulrike Herzschuh

Grasslands on the northeastern Tibetan Plateau are particularly sensitive to changes in climate and herbivory. As two main compositions, Poaceae and Cyperaceae supply forage and support herbivory survival. However, to taxonomic resolution restriction of traditional plant proxies, the plant composition and richness change of vegetation in particular of Poaceae and Cyperaceae are still largely unknown. Here, we reconstruct the vegetation using Lake Donggi Cona sediment ancient DNA metabarcoding, targeting chloroplast trnL P6 loop (g h primer). To increase Poaceae and Cyperaceae taxonomic resolution we currently also investigate ITS1 of nuclear ribosomal DNA in Poaceae and Cyperaceae. A total of 257 terrestrial higher plant taxa, 14 Pteridophyta taxa and 9 aquatic taxa were detected. Before ca. 12.6 cal ka BP, Asteraceae dominate terrestrial plant communities, which are commonly associated with cold and arid conditions during the late glacial; after 12.6 cal ka BP, Asteraceae abundance decline, Poaceae, Rosaceae, and Salicaceae abundance increase likely related to an increase in precipitation and temperature. At 6.5 cal ka BP, the Asteraceae abundance increase, Poaceae and Salicaceae abundance decrease, which is possibly related to cold and dry environments. The plant richness increase sharply since 6.5 cal ka BP and continually maintain relatively high richness values, which may be related to herbivory. Our analyses combine different plant sedaDNA markers will help to elucidate vegetation shifts in the past with deeper taxonomic resolution and provide reference on grassland protection under future climate change scenarios.

How to cite: Liu, Y., Stoof-Leichsenring, K., Diekmann, B., and Herzschuh, U.: Plant sedaDNA reveals grassland change on the Northeastern Tibetan Plateau during the past 17 ka, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8793, https://doi.org/10.5194/egusphere-egu23-8793, 2023.

EGU23-9168 | ECS | Orals | BG2.4 | Highlight

Assessing the fate of polycondensed aromatic natural organic matter (NOM) in a high-alpine aquatic system 

Philipp Maurischat, Michael Seidel, Oliver Donnerhack, and Georg Guggenberger

With the Anthropocene, thermogenic organic carbon, also known as black carbon (BC) is increasingly introduced to ecosystems worldwide. BC is formed by incomplete combustion or pyrolysis of fossil fuels, at wildfires or by the intentional burning of biomass, emitted to the atmosphere and hydrosphere or remaining in the bio-/pedosphere. With its high molecular proportion of elemental carbon, BC is regraded to be protected from fast microbial degradation by its inherent molecular properties. In aquatic systems, BC is partly sedimented or buried when reaching endorheic lakes or the ocean, where it is withdrawn from the carbon cycle. The biogeochemical implications of BC or its degradation products in aquatic systems have therefore not received much attention. Especially in sensitive oligotrophic alpine systems, such as the treeless Tibetan Nam Co catchment, part of the biggest connected alpine pasture system in the world, which is exposed to increasing anthropogenic pressure, any nutrient and carbon surplus can threaten the ecological status.

This was studied by an ultra-high resolution mass spectrometry approach that identifies several thousands of molecular formulae in dissolved organic matter (DOM). Including polycondensed aromatics (pcAro) that are considered to include thermogenic DOM.

Incubation experiments of water samples indicated that pcAro DOM was transformed by microbes to a comparable degree such as other natural organic matter (NOM) in the samples, removing pcAro DOM by defunctionalization or metabolization. In the environmental samples we found that pcAro DOM discharged to the endorheic Nam Co Lake was transformed by photodegradation along with other aromatic compounds. For DOM of streams and the lake of the high-alpine Nam Co watershed, most pcAro is likely of local origin, i.e. derived from burning of yak faeces by pastoralist households. This pcAro formed from cellulose-rich and lignin-poor Cyperaceae fodder is chemically distinct from low-land natural biomass, usually including the burning of wood.

Thus pcAro DOM appeared to be a more viable part of the carbon cycle than previously assumed. Our data support the hypothesis that the fate of polycondensed aromatic DOM depends on several environmental factors, such as catchment characteristics, water opacity, solar irradiation and actual light penetration into the water column, as well as on the carbon source, driving the molecular composition of thermogenic NOM.

 

How to cite: Maurischat, P., Seidel, M., Donnerhack, O., and Guggenberger, G.: Assessing the fate of polycondensed aromatic natural organic matter (NOM) in a high-alpine aquatic system, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9168, https://doi.org/10.5194/egusphere-egu23-9168, 2023.

EGU23-9304 | ECS | Orals | BG2.4

A procedure to characterize physical and chemical molecular properties of individual organic matter particles 

Edurne Estévez, Sophia Mützel, Rubén del Campo, Roland Stalder, and Gabriel Singer

Rivers are important contributors to the global carbon cycle as they actively transform terrestrial organic matter (OM) during transport to the oceans. The efficient OM processing results from a diverse assemblage of consumers including heterotrophic microbes (i.e., fungi, bacteria and protists) and macroinvertebrates, which interact with an equally diverse pool of OM. Ecologically, OM can be understood as forming a multidimensional resource space for consumers, whose understanding, however, requires an advanced capability to describe relevant dimensions (i.e., traits of OM) at a level that matches the resolution of consumer diversity, where significant advancement is generated by molecular biological means (i.e., DNA sequencing). This implies moving beyond proxy-based indirect descriptors (e.g., indices derived from absorbance or fluorescence spectroscopic analyses), integrative bulk property measures (e.g., C, N, P, lignin, tannins and fibre content) or bulk amounts of operational size fractions (e.g., dissolved, fine and coarse particulate OM). Recent technological advances such as size-exclusion, liquid or ion chromatography coupled to mass spectrometry have allowed to describe dissolved OM (DOM) on a molecular species level, setting a great step forward in the highly resolved description of DOM properties. However, particulate OM (POM) characterization remains behind significantly. Here, a per-particle basis description with regard to physical features and macromolecular composition is needed. We propose a procedure to asses both physical and chemical molecular properties of individual POM particles by combining (i) photometrical techniques, which are based on image processing and particle analysis (e.g., ImageJ) of pictures obtained with microscopes or cameras, and (ii) attenuated total reflectance infrared spectroscopy (ATR-FTIR) to measure particle-specific chemical composition. We apply this method to POM samples collected along large-scale environmental gradients in river networks.

How to cite: Estévez, E., Mützel, S., del Campo, R., Stalder, R., and Singer, G.: A procedure to characterize physical and chemical molecular properties of individual organic matter particles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9304, https://doi.org/10.5194/egusphere-egu23-9304, 2023.

EGU23-9999 | ECS | Orals | BG2.4

Comparative metagenomics of terrestrial organic matter degradation in the Western Arctic 

Zakhar Kazmiruk and Eric Collins

The Arctic Ocean receives more terrestrial dissolved organic matter (tDOM) on a per volume basis than any other ocean, resulting in Arctic coastal waters harboring the highest concentration of tDOM among the world’s oceans. Due to climate change induced intensification of the hydrological cycle, permafrost thaw, and coastal erosion, tDOM input into Arctic coastal waters has been steadily increasing. Nguyen et al. (2022) have speculated that the increasing presence of tDOM in the Arctic Ocean is causing a shift in the local microbiological communities. This may significantly affect CO2 fluxes and food web dynamics in the ocean. Despite recent incubation experiments reporting substantial biodegradation of tDOM in Arctic coastal waters, very few studies have attempted to examine the genetic capacity of Arctic marine microorganisms to process lignocellulose and other recalcitrant aromatic compounds of terrestrial origin. In this study, we perform comparative metagenomics in order to assess the diversity and distribution of microbial genes responsible for tDOM degradation in the Western Arctic. We searched 361 seawater metagenomes from the Bering Shelf, Bering Strait, and Chukchi Shelf for orthologs responsible for ring-opening reactions associated with degradation of tDOM (Grevesse et al., 2022). Like others, we identified Rhodobacterales as important contributors to microbial communities encoding the ring-opening reactions required for degradation of aromatic compounds such as tDOM and petroleum products, including members of the Roseobacteraceae (Sulfitobacter, Roseomonas) and Rhodobacteraceae (Planktomarina, Ascidiaceihabitans, and uncultured taxa). We found the presence of degradation genes to be widely distributed across temperature-, salinity-, depth-, and latitudinal gradients, with no clear patterns in the richness of genes. Future work will investigate the relative abundance of these functional genes among metagenome assembled genomes derived from these samples. Doing so, we hope to elucidate the environmental factors supporting the presence of tDOM degrading microorganisms. This study will contribute to the accumulating knowledge on adaptability of marine microorganisms to inputs of recalcitrant organic compounds.

How to cite: Kazmiruk, Z. and Collins, E.: Comparative metagenomics of terrestrial organic matter degradation in the Western Arctic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9999, https://doi.org/10.5194/egusphere-egu23-9999, 2023.

EGU23-10354 | Orals | BG2.4 | Highlight

Floral analysis of a ~140 yr sediment record using sedaDNA and diatoms, Summit Lake Nevada, USA 

Paula Noble, Sarah Crump, Amelia Muscott, Darren Larsen, Ana Carolina Ruiz Fernandez, Sudeep Chandra, James Simmons, Ayowole Fifo, and Adam Csank

The sediment fill at Summit Lake shows strong potential for reconstructing past changes (Holocene to present) in the paleoecology and regional paleoclimate for the subalpine region of the Black Rock Range, northwestern Nevada, USA. Summit Lake is a high desert terminal lake with a surface elevation of 1780m.a.s.l. and is a eutrophic, alkaline (~8.4), dimictic lake with a maximum depth of ~10 m and a small surface area (2.8 km2). There is abundant growth of macrophytes, including Polygonium (smartweed), Myriophyllum (milfoil), and Ceratophyllum (coon tail), and growth progresses throughout the summer months. The lake falls within the domain of the Summit Lake Paiute Tribe, who has an inextricable cultural connection to the lake via the native Lahontan cutthroat fishery. The tribe’s original name, Agai Panina Ticutta, translates as the Summit Lake Fish Eaters.

In 2021 and 2022 C.E., we collected a series of surface and long sediment cores from multiple sites in the lake. This study focuses on sediments collected from the lake’s central depocenter. Preliminary age control of Summit Lake sediments is determined by 210Pb-dating (corroborated by the stratigraphic profiles of the man-made radionuclides 137Cs, 241Am) for the upper ~40 cm, and the Mount Mazama tephra (~7.6 ka) at 410cm depth. The age model suggests high and increasing sedimentation rates between early 1900 C.E. and 2021 C.E. (from 0.05 to 1.87 cm/yr). In comparison, the mean sedimentation rate between the Mazama tephra and ~1900 C.E. is low (0.05 cm/yr). We present preliminary sedaDNA and diatom data for the last ca. 140 years. Plant sedaDNA shows good preservation, with a stable alpha diversity of ~40 ASVs. The plant record is dominated by the aquatic plants Myriophyllum and Potamogeton (pondweed) in the upper 40cm, and terrestrial plants are also represented, including sagebrush, willow, aspen, and a variety of herbaceous plants, including aster, rose, primrose, buckwheat, borage, lupin, and saxifrage. The diatom flora of the upper 40cm is dominated by the benthic epiphyte Cocconeis placentula, which is consistent with a large macrophyte community seen in the modern system and indicated by the plant sedaDNA. Modern sampling shows the epiphytic relationship between C. placentula and milfoil. Future work will include pairing and harmonizing the diatom record derived from traditional morphotaxonomy and eDNA, contextualizing the plant eDNA with the modern plant community, and refining the age model to better discern Holocene climate events that may be driving the changes in sediment flux and the floral community. These data will be extended down-core to reconstruct the past climate and lake levels, informing the Tribe’s management efforts for a resilient watershed and fishery in the future.

How to cite: Noble, P., Crump, S., Muscott, A., Larsen, D., Ruiz Fernandez, A. C., Chandra, S., Simmons, J., Fifo, A., and Csank, A.: Floral analysis of a ~140 yr sediment record using sedaDNA and diatoms, Summit Lake Nevada, USA, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10354, https://doi.org/10.5194/egusphere-egu23-10354, 2023.

EGU23-11962 | ECS | Orals | BG2.4

Molecular transformation of dissolved organic matter in soils of contrasting tropical rainforest ecosystems is similar to temperate regions suggesting common processes 

Dan Frederik Lange, Carsten Simon, Yago Rodrigues Santos, Elaine Pires, Jonismar Souza da Silva, Sávio José Filgueiras Ferreira, Carlos Alberto Quesada, Thorsten Schäfer, and Gerd Gleixner

The variability of the molecular composition of dissolved organic matter (DOM) in soils is predominantly explained by microbial mineralization and assimilation as well as interactions with mineral surfaces and soil organic matter (SOM). From a temperate site with calcareous soil it is established that the molecular composition of DOM shifts from plant-derived towards microorganism-derived signals in soil depth profiles. This variability is largely explained by microbial activity and only to a minor degree by soil-derived parameters like texture and SOM. Here we analyze the molecular composition of DOM in depth profiles of tropical rainforest soils in order to compare its variability to the temperate site as the tropical ecosystems have larger variability in soil texture and mineralogy and lower SOM content. We collected porewater in soil profiles of four ecosystems belonging to two major Amazon rainforest types, terra firme forest on clay soils and white-sand forest on sandy soils. We analyzed the molecular composition of DOM using solid-phase extraction and ultrahigh resolution mass spectrometry.

The concentration and composition of DOM differed strongly between the sandy white-sand and clayey terra firme sites. DOM concentration in white-sand soils was much higher and decreased less with depth compared to the terra firme forests. Topsoil DOM in white-sand forests was characterized by high abundance of aromatic plant-derived compounds, whereas it reflected a stronger microbial imprint in terra firme sites. The molecular composition of DOM changed significantly with depth at all sites. In both terra firme and one white-sand forest the transformation was consistent with the expected shift from plant-derived signals towards increasing microbial reworking. The Bray-Curtis dissimilarity between topsoil and greater depth was considerably higher in terra firme compared to white-sand soils with values of 0.32 +- 0.06 and 0.14 +- 0.04, respectively, suggesting much slower DOM transformation in sandy soils. The dissimilarity was correlated similarly to pH, clay content and mineralogy (Pearson R2 = 0.27, 0.21 and 0.23, respectively). The high dissimilarity in the terra firme sites that vary strongly in clay content and mineralogy was only significantly correlated to pH (R2 = 0.16). This suggests that clay content and mineralogy, likely linked to DOM adsorption, were less important for the observed depth trend, which aligns with results from the temperate site. The significant effect of soil pH on the molecular transformation is in line with the importance of microorganisms for DOM transformation as soil pH is a major control on microbial community structure. Overall, our results suggest that similar processes control DOM transformation in temperate and tropical ecosystems, which are likely linked to microbial processing and formation of DOM.

How to cite: Lange, D. F., Simon, C., Santos, Y. R., Pires, E., da Silva, J. S., Ferreira, S. J. F., Quesada, C. A., Schäfer, T., and Gleixner, G.: Molecular transformation of dissolved organic matter in soils of contrasting tropical rainforest ecosystems is similar to temperate regions suggesting common processes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11962, https://doi.org/10.5194/egusphere-egu23-11962, 2023.

EGU23-12378 | ECS | Posters on site | BG2.4

Microbial Dissolved Organic Matter utilisation at the nearsediment waters in the Baltic Sea Deeps 

Alexandra Loginova, Kinga Hoszek, and Piotr Kowalczuk

Recent studies suggested that sediment pore waters may serve as a source of bioavailable DOM to the overlying water column, which may stimulate microbial activity in the nearbottom waters. However, a combination of DOM measurements with proxies of heterotrophic activity was not a priority of those studies. In this study, we aim to assess the bioavailability of DOM, released by sediments, and whether it may stimulate an increase in heterotrophic cell number. For this, we conduct the measurements of dissolved organic carbon (DOC) and DOM optical properties, such as chromophoric (CDOM) and fluorescent (FDOM) DOM, from the sediment pore waters of the Baltic Sea Deeps and in the water column in order to evaluate the initial supply flux (return flux) to the bottom waters and provide essential insights on the starting composition of DOM. We combine those measurements with the temporal changes of DOC, CDOM and FDOM during ex-situ incubations of the sediment cores with overlying water to infer quantitative and qualitative transformations of DOM during the incubation time. We discuss those data in combination with microbial abundance, oxygen and nutrient consumption as a proxy for sediment released DOM to serve as a substrate for heterotrophic communities to grow and function.

How to cite: Loginova, A., Hoszek, K., and Kowalczuk, P.: Microbial Dissolved Organic Matter utilisation at the nearsediment waters in the Baltic Sea Deeps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12378, https://doi.org/10.5194/egusphere-egu23-12378, 2023.

EGU23-13174 | ECS | Posters on site | BG2.4

Characterization of dissolved organic matter composition along the terrestrial-aquatic continuum in the Oren Mountains, Germany 

Livia Vieira Carlini Charamba, Tobias Houska, Klaus-Holger Knorr, and Karsten Kalbitz

In forested catchments, soil organic matter leaching leads to the transport of dissolved organic matter (DOM) into deeper soil horizons and surface waters, directly affecting the composition and functions of surface water DOM undergoing microbial decomposition and photochemical reactions. The knowledge of the amounts and composition of DOM in the soil is, thus, fundamental for characterizing its role in aquatic ecosystems. Differences in DOM composition might be used to identify major DOM sources in streams, e.g. to distinguish the influence of peatland and upland mineral soils, considering that each source has its own typical DOM fingerprint. Furthermore, a deeper understanding of the complex interactions at the terrestrial-aquatic interface could shed a light on the role of DOM composition in nutrient cycling in surface water, which is so far not well described in the literature. Thus, the aim of this study is to present a preliminary analysis of DOM composition along the terrestrial-aquatic continuum as the basis for source identification in streams characterized by long-term increasing dissolved organic carbon concentrations.

Soil water samples from different depths and stream water samples were taken biweekly for roughly a year in the catchment area of the Sosa drinking water reservoir located in the Ore Mountains (Saxony, Germany). Four different sub-catchments were analyzed. Two of them consisted mainly of peatland and degraded peatland soils (P1 and P2, respectively) and the remaining two of mineral soils such as Podzols and Cambisols (M1 and M2). The aqueous samples (soil and surface water) and soil solid phase samples (forest floor and topsoil peat horizons) from the four sub-catchments were analyzed by pyrolysis gas chromatography mass spectrometry (Py-GC-MS) and the results were further processed in Rstudio to facilitate and standardize the chemical identification of the pyrolysates. A principal component analysis (PCA) was applied to the Rstudio results.

With the PCA results we can clearly differentiate soil samples from soil water and stream water samples in principal component 1, i.e. PC1 (25.6%). Even different layers within the soil can be separated, with the deepest layer being most similar to the stream water. Lignin-derived compounds were mainly responsible to distinguish the different sample types (i.e. soil, soil water and stream water), e.g. vanillin lactoside, guaiacol, creosol, apocynin, trans-m-propenylguaiacol, and 4-ethylguaiacol. From those, only guaiacol was found to be present in stream water of P1 and P2 and in soil water of P1, with decreasing concentration along the terrestrial-aquatic continuum (i.e. from soil to stream water). PC2 (7.2%) accounted for differences i) in soil type, i.e., peatland vs. mineral soil and ii) between soil and stream water, including the different sampling sites.

In conclusion, our research indicates that DOM composition clearly changes along the terrestrial-aquatic continuum. These differences can be used to separate two important potential DOM sources, i.e. DOM from peatlands and DOM from the forest floor horizon of mineral soils. Py-GC-MS coupled with a semiautomatic data processing routine and PCA is a very promising tool for identifying DOM from different sources in stream water samples.

How to cite: Vieira Carlini Charamba, L., Houska, T., Knorr, K.-H., and Kalbitz, K.: Characterization of dissolved organic matter composition along the terrestrial-aquatic continuum in the Oren Mountains, Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13174, https://doi.org/10.5194/egusphere-egu23-13174, 2023.

EGU23-13403 | ECS | Orals | BG2.4 | Highlight

Lake ecology and catchment vegetation changes reconstructed for the last 18,400 years in South-Western Yakutia, Siberia 

Izabella Baisheva, Boris K. Biskaborn, Kathleen R. Stoof-Leichsenring, Andrei A. Andreev, Stefano Meucci, Lena Ushnitskaya, Luidmila A. Pestryakova, Elisabeth Dietze, and Ulrike Herzschuh

Since many lakes in Yakutia, eastern Siberia, are of thermokarst origin, it can be challenging to reach ages of paleorecords beyond the Holocene, hence limiting the understanding of long-term key interactions between climate change, vegetation dynamics, biodiversity shifts, and lake development. However, with a new paleoenvironmental multiproxy project at an intermontane basin we aim to reconstruct lake-vegetation feedbacks since the Late Glacial Maximum (LGM). For that purpose, a 10.8 m long sediment core has been extracted from the deepest part (22.3 m) of the Lake Khamra (59.99095° N, 112.98345° E) and dated back to 18.4 cal ka BP. Lake Khamra is situated in South-Western Yakutia, the transitional zone of discontinuous to continuous permafrost, it is also in the zone of mixed evergreen-deciduous forest. We applied sedimentological and XRF-derived geochemical parameters in addition to palynological analyses of plant fossils and metabarcoding analyses of diatoms and plants sedimentary ancient DNA (sedaDNA). Our genetic analyses of diatoms revealed 45 unique sequence types. A high distribution of several small fragilarioid types indicates the initial formation of the lake, started in the LGM (15.4 cal ka BP), and high abundance of planktonic taxa since 8 cal ka BP indicates lake deepening in the Mid-Holocene. SedaDNA composition of 38 unique sequence types of aquatic and 155 unique sequence types of terrestrial plants revealed the agreement with pollen and non-pollen palynomorph derived vegetation composition. LGM vegetation was represented as wet tundra and both analyses revealed refugia of Larix. Tundra vegetation only appeared in LGM. The Holocene warming led to the forest establishment and therefore lake vegetation feedback intensification, seen from the turnover of diatoms. Diatoms assemblages of LGM which were represented by only few epiphytic taxa significantly increased the richness, as well as increasing of planktonic and benthic diatom assemblages. The lake expansion resulted in a diversification of emergent aquatic plants. And again, because the lake is not of thermokarst origin it shows more stable insight to environmental variability. This study provides a better understanding of the climate, lake system dynamics, and vegetation in Siberia, and simultaneously fills in the very scarce paleolimnological data in eastern Siberia.

How to cite: Baisheva, I., Biskaborn, B. K., Stoof-Leichsenring, K. R., Andreev, A. A., Meucci, S., Ushnitskaya, L., Pestryakova, L. A., Dietze, E., and Herzschuh, U.: Lake ecology and catchment vegetation changes reconstructed for the last 18,400 years in South-Western Yakutia, Siberia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13403, https://doi.org/10.5194/egusphere-egu23-13403, 2023.

EGU23-13604 | Posters on site | BG2.4

Improving solid-phase extraction of dissolved organic matter (DOM) 

Hannelore Waska, Jessika Füssel, Katharina Paetz, Marit Renken, and Thorsten Dittmar

In current dissolved organic matter (DOM) research, solid-phase extraction (SPE) with Bond Elut PPL resins is the gold standard for desalination and concentration. This method routinely recovers 50-65% of marine and terrestrial DOM. However, in unusual samples, for example from hydrothermal vents, early-stage microalgal cultures, the sea-surface microlayer, or sediment leachates, DOM recovery drops to 20% or less, presumably because the prevalent organic compounds are outside the polarity or molecular size window of the PPL sorbent. Here, we adjusted individual steps of the standard protocol, such as acid type, acid strength, and solvent polarity to increase DOM yields in notoriously low-recovery samples. We compared acidification of a coastal marine sample with either HNO3 or HCl at pH 1 and pH 2. From samples of the sea-surface microlayer, the underlying seawater, and macroalgal and intertidal sediment leachates, we performed two subsequent extractions at environmental pH and at pH 2. Following DOM extraction, we compared several eluents, including methanol, acidic methanol, tetrahydrofuran, and dichloromethane. We evaluated the different approaches by determining dissolved organic carbon (DOC) and dissolved black carbon (DBC) yields as well as changes in molecular DOM composition using ultra-high resolution mass spectrometry.

Lowering the pH from 2 to 1 increased the DBC yield but resulted in slightly lower DOC recoveries, indicating a shift in molecular composition of the retained compounds rather than expansion of the SPE window. HNO3 may furthermore cause nitration, nitrosation and oxidation of DOM. However, combining sequential extraction at neutral and acidic pH with a series of eluents increased DOC recoveries substantially in comparison to the standard protocol. The inter-sample differences in the molecular composition (as detected via ultrahigh-resolution mass spectrometry on a molecular formula level) of the extracted DOM exceeded those caused by variations in the protocol and followed similar trends compared to the standard procedure. The co-variance of molecular degradation indicators with PPL performance emerged as a general trend: Recoveries with the standard protocol increased with the DOM degradation state. We conclude that PPL is much more versatile than its regular use indicates and encourage exploring a larger bandwidth of experimental setups for a better representation of natural DOM from a wide variety of sources.

How to cite: Waska, H., Füssel, J., Paetz, K., Renken, M., and Dittmar, T.: Improving solid-phase extraction of dissolved organic matter (DOM), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13604, https://doi.org/10.5194/egusphere-egu23-13604, 2023.

EGU23-14571 | Orals | BG2.4

Alkenones, as tool for reconstructing surface water temperature and salinity changesduring the Miocene-Pliocene transition in the northern Mediterranean basin 

Francesco Pilade, Iuliana Vasiliev, Daniel Birgel, Marcello Natalicchio, Francesco Dela Pierre, Alan Mancini, Francesca Lozar, and Rocco Gennari

Alkenones are unsaturated long-chained ketones produced by haptophyte algae living in the photic zone of the water column. In cultures of Emiliania huxleyi, the alkenones’ degree of unsaturation between C37 alkenone isomers (UK37’) is proportional to thetemperature of the water in which this haptophyte lives. Besides the UK37’ providing a paleotemperature proxy in the marine realm, the identification of long-chain alkenones in modern lacustrine waters and sediments allowed the recognition of non-marinehaptophyte algae able to produce alkenones. At different salinities, the haptophytes produce a different measure of alkenones molecules in particular: the abundance of C37:4 against the other C37 isomers; the different C38Et/C38Me ratio, and the differentratio between ∑C37/∑C38 isomers.

One of the best laboratories to explore and extend the usage of alkenones as a tool for reconstructing changes in sea surface temperature (SST) and salinity (SSS) is the Mediterranean domain during the Miocene - Pliocene, a boundary marked by the abrupt transition from uppermost Messinian brackish and shallow waters of the Lago-Mare event (5.55-5.33 Ma) to lower Pliocene open marine (Zanclean; 5.33 Ma). Here, we will further address the challenge of using alkenones coupled with a novel combination of commonly used proxies to reconstruct the highly varying water surface condition affecting the Mediterranean Sea during the Miocene to Pliocene transition. Therefore, we studied three time-equivalent sections from the northern part of the basin.

The integration of micropaleontological data with inorganic and organic geochemical ones allowed to evaluate of the changes of the alkenones producers across the Miocene to Pliocene transition and to test the reliability of the C37/C38 ratio, the C37:4% andC38Et/C38Me ratio as paleoenvironmental proxies.

Our results indicate that alkenone-based proxies can be confidently used for tracing SSS changes at the Miocene-Pliocene transition. Their reliability is supported by comparison with the micropaleontological assemblages (body fossils). In particular, the Pliocene sediments are dominated by alkenone marine producers, which records limited SSSs variations, confirmed by the abundant anddiversified calcareous plankton assemblage. For the marine Pliocene, our calculated SSTs (average 20 °C) and SSSs (35-38 PSU) are in the range of the values for that time.

In contrast, for the Lago Mare phase, the scarcity or absence of in situ body fossils of marine calcareous plankton and the mixing of freshwater and marine alkenones producers suggest more significant salinity fluctuations, with a general increase in salinity approaching the Miocene-Pliocene boundary. For the Lago Mare event, our reconstructed SSTs are in the range of those in Pliocene, and the reconstructed salinities for the latestMiocene samples (33 to 36 PSU) are not so different from the ones in Pliocene. Although the presence of marine primary producers inthe Lago Mare sediments is not conclusive concerning establishing a marine-typical salinity environment before the Pliocene in the Mediterranean, the calculated SSSs reflect the reconstruction proposed by alkenones. The high SSSs values and the presence of marine primary producers in the latest Lago Mare may suggest sporadic influxes of oceanic waters.

How to cite: Pilade, F., Vasiliev, I., Birgel, D., Natalicchio, M., Dela Pierre, F., Mancini, A., Lozar, F., and Gennari, R.: Alkenones, as tool for reconstructing surface water temperature and salinity changesduring the Miocene-Pliocene transition in the northern Mediterranean basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14571, https://doi.org/10.5194/egusphere-egu23-14571, 2023.

EGU23-14893 | ECS | Posters on site | BG2.4 | Highlight

DOM accumulation in oligotrophic surface waters: new insights from the Mediterranean Sea 

Giancarlo Bachi, Marta Furia, Cecilia Balestra, Raffaella Casotti, Giuseppe Civitarese, Gianpiero Cossarini, Mirco Guerrazzi, Daniel Repeta, Maurizio Ribera d'Alcalà, and Chiara Santinelli

Dissolved Organic Matter (DOM), the largest pools of reduced carbon on Earth, represents the major source of energy for micro-heterotrophs, starting the microbial loop. In the open ocean, most of the autochthonous DOM is labile and is therefore respired within days, but a small fraction, called recalcitrant, persists for years to millennia. There are large oligotrophic areas in the oceans, such as the North Atlantic subtropical gyre and the Mediterranean Sea, where the decoupling between production and consumption of DOM leads to its accumulation with implications for the microbial loop.

The main goal of this study is to investigate the putative functioning of the microbial loop all across the Mediterranean Sea following the main path of the Atlantic water entering through the Gibraltar Strait. Dissolved Organic Carbon (DOC) concentration and fluorescence of chromophoric DOM were measured together with heterotrophic prokaryotes, nanoflagellates and virus abundance by flow cytometry. Samples were collected during the MSM72 oceanographic cruise carried out in March-April 2018. Results show that in the western Mediterranean Sea the heterotrophic prokaryotes are relatively abundant and DOM is efficiently removed, suggesting an active transfer of carbon to the higher trophic levels. In contrast, in the eastern Mediterranean Sea DOM accumulates, prokaryote abundance is low and low nucleic acid prokaryotes dominates, suggesting a malfunctioning of the microbial loop leading to a less efficient carbon transfer to the food web. Following the core of the Atlantic Water flowing eastward, as the nutricline deepens, an ecological succession in the phytoplankton communities (from picoeukaryotes to cyanobacteria) is observed, together with a depletion of the fluorescent components in the DOM pool, reflecting changes in the DOM quality.

Different hypotheses can be formulated to explain these observations: the microbial communities could be limited by nutrient availability, by an enhanced top-down pressure by grazers or viruses or by the quality of DOM that could be recalcitrant due to abiotic processes such as photobleaching or to the progressive use of its labile fraction by micro-heterotrophs.

With the upcoming increase in water column stratification, a change in the quality of DOM due to the combined effect of abiotic (e.g., photobleaching) and biotic (e.g., change in the phytoplankton community) is expected with consequences for the functioning of the microbial loop. The questions about the malfunctioning of the microbial loop and its implications in a global change scenario have puzzled the scientists for years and the Mediterranean Sea is a well-suited natural laboratory to answer them.

How to cite: Bachi, G., Furia, M., Balestra, C., Casotti, R., Civitarese, G., Cossarini, G., Guerrazzi, M., Repeta, D., Ribera d'Alcalà, M., and Santinelli, C.: DOM accumulation in oligotrophic surface waters: new insights from the Mediterranean Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14893, https://doi.org/10.5194/egusphere-egu23-14893, 2023.

EGU23-15566 | ECS | Posters on site | BG2.4 | Highlight

Does vertical mobility of eDNA in old soils affect the reconstruction of past environments? 

Doreen Yu-Tuan Huang, Nick Cutler, Saúl Rodriguez, Marina Morlock, and Jonatan Klaminder

Environmental DNA (eDNA) in sediments (soils, lake and marine sediments) can – in principle - be used to reconstruct past environments, provided the DNA is readily preserved and is relatively immobile within the sedimentary sequence (to allow accurate dating). Concerns over the mobility of DNA in soils have meant that these sediments have not been considered a reliable source of eDNA for palaeo-reconstruction. However, eDNA in soils could be preserved and immobilized through adsorption to secondary minerals (predominantly clays) in sediments. The potential of clay minerals to immobilize DNA is poorly understood; to address this knowledge gap, we conducted an experiment to evaluate the vertical mobility of eDNA between soil layers.

Our experiment involved the application of spiked (non-indigenous) DNA to an experimental plot in eastern Greenland over a period of two years. During this period, we took soil samples at different depths below the plot and sequenced the samples to detect the spiked DNA. In addition to our experiment, we analyzed plant DNA from sequences of paleosols at a site in west Greenland and a site in south Iceland, to attempt to reconstruct long-term changes in vegetation cover.

Our Greenland experiment indicated that faint traces of alien DNA can be transported to deep (thus old) soil horizons by percolating rainwater and can remain intact for at least two years. We suspect this occurred in Greenland because a) rainfall is high and b) the soils are skeletal and exceptionally porous. Despite this result, we observed changes in plant DNA with depth at our other two sites; these changes seemed to track century-scale environmental changes. We could not date the changes in the Greenlandic record due to the scarcity of macrofossils for radiocarbon dating. However, macroscopic tephra layers at the site in Iceland provided isochrons (time parallel marker beds) that allowed us to assign approximate dates using tephrochronology.

Our results indicate that most of the spiked eDNA was either retained at the surface or degraded in the soil profile: only very tiny quantities leached to deep soil horizons. Therefore, we propose that eDNA in paleosols, especially those on tephra beds, possesses great potential in palaeo-reconstruction, especially when other archives (fossils, lake sediments) are not available. However, we recommend that more studies are required to examine how mineralogy and soil types govern eDNA mobility and longevity in soils.

How to cite: Huang, D. Y.-T., Cutler, N., Rodriguez, S., Morlock, M., and Klaminder, J.: Does vertical mobility of eDNA in old soils affect the reconstruction of past environments?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15566, https://doi.org/10.5194/egusphere-egu23-15566, 2023.

EGU23-15884 | Posters on site | BG2.4

Spatial dynamics of marine dissolved organic matter in the Benguela upwelling system 

Gonzalo V Gomez-Saez, Ömer K Coskun, Yanik Oertel, Jutta Niggemann, Thorsten Dittmar, Timothy G Ferdelman, and William D Orsi

Marine dissolved organic matter (DOM) is one of the largest active carbon pools on Earth, storing one thousand times more carbon than all living organisms in the ocean combined, and similar amounts of carbon than all CO2 in the atmospheric reservoir. Coastal upwelling systems are extremely productive marine regions where surface waters mix with nutrient-rich waters from below, generating hotspots for carbon cycling with highly active microbial communities in the surface and low dissolved oxygen concentration in the deep waters. However, there is a lack of mechanistic understanding with respect to DOM accumulation in upwelling systems, and the sources and processing of DOM within these productive systems are an understudied topic. Here, we performed a novel spatial analysis of the DOM dynamics in the Benguela upwelling system off Namibia both regionally (from shelf to open ocean) and vertically (from surface ocean to subseafloor). To do so, we applied state-of-the-art molecular characterization of DOM using Fourier transform ion-cyclotron resonance mass spectrometry (FT-ICR-MS). By FT-ICR-MS, we identified 29,769 DOM molecular formulas from 75 water column and 8 pore water samples. Molecular DOM analyses were complemented by organic and inorganic quantitative geochemical data and microbial 16S rRNA gene-based diversity coupled with shotgun metagenomic analyses. Furthermore, we performed a set of incubation experiments onboard to test the biodegradability of DOM, with special focus on the dissolved organic sulfur compounds and potential genes involved in sulfur cycling. Preliminary results showed highest differences in the molecular analyses between the sediment pore water DOM and the water column DOM. Most of the variability in the DOM dataset could be explained by the high proportion of compounds containing heteroatoms different than oxygen in the sediments (N, S and P), while oxygen concentrations did not show a clear effect on the DOM molecular composition in the water column. In addition, metagenomic sequencing revealed that marker genes involved in sulfur oxidation and reduction such as periplasmic sulfur-oxidizing proteins (sox), dissimilatory sulfite reductase (dsr), reverse dissimilatory sulfite reductase (rDsr), and adenylyl-sulfate reductase (apr) present throughout the water column and subseafloor. Remarkably, the highest abundance of sulfur-reducing genes was observed in sulfidic sediments whereas sulfur-oxidation genes showed minimal differences in abundance along the water column profile. Further statistical analyses (in progress) will allow us to identify connections between the microbial biosphere and the chemical diversity of DOM, which will help to better understand the mechanisms of biodegradation and accumulation of DOM in coastal upwelling systems and deoxygenated regions.

How to cite: Gomez-Saez, G. V., Coskun, Ö. K., Oertel, Y., Niggemann, J., Dittmar, T., Ferdelman, T. G., and Orsi, W. D.: Spatial dynamics of marine dissolved organic matter in the Benguela upwelling system, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15884, https://doi.org/10.5194/egusphere-egu23-15884, 2023.

EGU23-16424 | ECS | Orals | BG2.4

Dissolved organic sulfur utilization by marine benthic microbial communities revealed by quantitative DNA stable isotope probing 

Ömer Kürsat Coskun, William D. Orsi, Steve D'Hondt, and Gonzalo V. Gomez-Saez

Microbial metabolisms are directly responsible for the production, degradation and recycling of dissolved organic matter (DOM) in the ocean. Many compounds within the DOM contain sulfur (dissolved organic sulfur, DOS) and in sum they represent the largest reservoir of organic sulfur in the ocean. Recent studies indicated an abundant and diverse suite of marine bacteria with the genetic capacity for DOS transformation. However, there is currently very little experimental data regarding the marine sediment microbial communities that are actively using DOS substrates as a source of carbon. Here, we use quantitative 13C DNA stable isotope probing (qSIP) to provide the first quantitative measurements of DOS (taurine and methionine) utilization by specific operational taxonomic units in seafloor sediments from continental shelf of Puerto Rico (493 meter below sea surface). Immediately after sampling, seafloor sediments were amended with 500 µg / g 13C-labeled taurine or methionine as well as natural-abundant (12C) substrates as a control and were incubated in gas-tight glass flasks with no headspace in the dark over two different timepoints (30 hours and 10 days) to unravel the active microbial communities. Our preliminary results by gas-chromatography mass spectrometry showed that there was 6 – 10% of 13CO2-remineralization compared to control samples. This indicates that taurine and methionine are important DOS substrates supporting the activity of benthic microbial populations. Notably, the rate of taurine remineralization was five-fold higher than glucose and 50-fold higher than methionine over the first 30-hours of incubation, suggesting that taurine is an underappreciated, yet important DOS substrate for microbial activity at the seafloor. Oxygen was rapidly consumed to anoxic levels over the first 12 hours in all incubations, indicating that the taurine was utilized via anaerobic microbial metabolism. This was reflected by changes in the initial microbial community that was dominated by Thaumarchaeota (29%), Gammaproteobacteria (15%) and Planctomycetes (13%), which changed to being enriched by Firmicutes (8%-43%), Deltaproteobacteria (10%-26%), and Gammaproteobacteria (10%-29%) in the presence of taurine and methionine. Further quantitative DNA isotope probing study (in progress) will reveal the specific anaerobic microbial taxa that are responsible for driving the biogeochemical cycling of these important, yet overlooked DOS substrates at the seafloor.

How to cite: Coskun, Ö. K., Orsi, W. D., D'Hondt, S., and Gomez-Saez, G. V.: Dissolved organic sulfur utilization by marine benthic microbial communities revealed by quantitative DNA stable isotope probing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16424, https://doi.org/10.5194/egusphere-egu23-16424, 2023.

EGU23-16616 | ECS | Orals | BG2.4

Towards semi-quantification of DOM: isomer separation with LC-FT-ICR-MS combined with a post-column infusion of standard. 

Rebecca Rodrigues Matos, Elaine Jennings, Boris Koch, and Oliver Lechtenfeld

Ultrahigh-resolution mass spectrometry like FT-ICR MS has greatly expanded our view of the complexity and reactivity of complex dissolved organic matter (DOM) in the environment. However, both the structural characterization and (semi)-quantification DOM are methodologically not fully resolved, despite recent advances with coupling liquid chromatography (LC) to FT-ICR-MS that allows isomeric separation. Likewise, matrix effects and the existence of multiple isomers with largely varying – but unknown – ionization efficiencies that are simultaneously ionized and detected in direct infusion (DI)-FT-ICR MS prevents (semi)-quantification of DOM compounds and has limited the comparability of samples. Finally, common normalization strategies applied for non-targeted DOM analysis with DI cannot be easily transferred to LC-type DOM data. Here we present a new method that combines a post-column infusion of internal standard (PCI-IS) with LC-FT-ICR MS in order to reduce and compensate matrix effects as well as to provide a robust and reliable way to normalize MS peak intensities and compare samples measured with LC-FT-ICR MS. To this end, DOM samples were analyzed and the peak intensity data normalized by the internal standard and other frequently used normalization methods (e.g. sum of intensity, base peak), and absolute intensity indicating that PCI-IS normalization provides superior precision and accuracy. The potential of this method to provide semi-quantitative information on polarity fractions of DOM is assessed by testing the precision, accuracy, and linearity of PCI-IS normalization of model compounds spiked into DOM samples. Our results indicate that the use of LC separation reduced matrix effects (as compared to DI) and, in combination with the internal standard, improved to potential to obtain reliable peak intensity information.

How to cite: Rodrigues Matos, R., Jennings, E., Koch, B., and Lechtenfeld, O.: Towards semi-quantification of DOM: isomer separation with LC-FT-ICR-MS combined with a post-column infusion of standard., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16616, https://doi.org/10.5194/egusphere-egu23-16616, 2023.

EGU23-16877 | Orals | BG2.4

Characterization and microbial degradation of polysaccharides in high molecular weight dissolved organic matter. 

Daniel J. Repeta, Benjamin N. Granzow, Andrew Burger, and Edward F. DeLong

A large fraction of marine primary production is directed towards the synthesis of polysaccharides, most of which are rapidly degraded by heterotrophs, including heterotrophic microbes. However, a novel class of polysaccharides characterized by high N-acetyl aminosugar and 6-deoxysugar content, escapes rapid degradation and accumulates as a constituent of marine dissolved organic matter (DOM). These polysaccharides, which comprise ~25% of total dissolved organic carbon, also represent a large reservoir of the potentially bioavailable organic N and P stored in DOM.   To better understand the accumulation and microbial degradation of DOM polysaccharides we used size-exclusion chromatography and diffusion-ordered NMR spectroscopy to examine the size-distribution and composition of DOM recovered from seawater by ultrafiltration. Our results show that DOM polysaccharides are relatively small, with a molecular weight range of 1.3–7.7 kD and an average molecular weight of ~6 kD in surface waters decreasing to ~3 kD at 900m. Acid hydrolysis of DOM polysaccharides releases a suite of characteristic neutral sugars (glucose, galactose, mannose, rhamnose, fucose and xylose), but most of the polysaccharide (80-90%) resists hydrolysis and undergoes Maillard-like reactions between amino- and reducing sugars. To circumvent this, we modified our hydrolysis conditions to promote sugar-sugar cleavage. With this approach, we were able to generate a suite of oligosaccharides with molecular weights between 0.3-1.8 kD that carry the same spectral characteristics as DOM polysaccharides. We are using transposon insertion sequencing (Tn-seq) of marine bacteria cultured on these oligosaccharides to identify genes and degradation pathways responsible for DOM polysaccharide degradation.

 

How to cite: Repeta, D. J., Granzow, B. N., Burger, A., and DeLong, E. F.: Characterization and microbial degradation of polysaccharides in high molecular weight dissolved organic matter., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16877, https://doi.org/10.5194/egusphere-egu23-16877, 2023.

EGU23-16956 | Orals | BG2.4

Characterization and potential impacts of active nitrifier host–virus interactions in soil 

Christina Hazard, Sungeun Lee, and Graeme W. Nicol

While the complexity of prokaryotic communities in soil is relatively well understood, we are currently ignorant of the role of viruses in influencing their ecology. Viruses infect every living organism and affect rates of biogeochemical processes by killing active cells via cell lysis, or augmenting function through the transfer of auxiliary metabolic genes. The microbially-mediated process of nitrification is central to nitrogen losses and emissions of the greenhouse gas nitrous oxide, contributing to global warming and stratospheric ozone depletion, and viruses may impact this central step of the global N cycle. However, challenges remain in identifying active interactions with specific host or functional groups and virus populations within structurally complex and diverse soil environments. To address this, discrete active interactions between individual hosts and viruses in soil microcosms were examined using the transfer of assimilated carbon from autotrophic prokaryotes to viruses. Microcosms were established with amendments of urea to fuel nitrification and 13C carbon dioxide, followed by DNA stable-isotope probing (SIP) combined with metagenomic analyses. Hybrid analysis of GC mol% fractionation and 13C-DNA-SIP resulted in the identification of active ammonia oxidizing archaea (AOA) hosts and viruses only. To enable characterization of viruses actively infecting all active ammonia- and nitrite oxidizing bacteria (AOB, NOB), a second approach was used where incubations were performed using filtration of virus-like particles to increase the recovery of virus metagenomes. This included differential inhibition of specific nitrifier groups to alleviate competition and potentially increase the abundance of viruses infecting non-inhibited groups. Applications of DMPP or octyne were added to preferentially inhibit AOB and encourage growth of AOA, or acetylene to inhibit all ammonia oxidizing activity as a negative control. This approach dramatically increased the recovery of high-quality virus contigs, with 225 contigs associated with those infecting AOA, AOB or NOB including 69 complete or near-complete genomes. Viruses of ammonia-oxidizers contained auxiliary metabolic genes involved in central metabolic pathways, and analysis of viral hallmark genes revealed that they were distinct from previously cultivated viruses. Results demonstrate that virus infection of nitrifiers and propagation of viruses is a dynamic process during soil nitrification, providing insights into potential impacts of viruses on a specific functional process in soil.

How to cite: Hazard, C., Lee, S., and Nicol, G. W.: Characterization and potential impacts of active nitrifier host–virus interactions in soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16956, https://doi.org/10.5194/egusphere-egu23-16956, 2023.

EGU23-17137 | ECS | Orals | BG2.4

The effect of flow velocity on eDNA and eRNA concentration 

Jelle A. Dercksen, Laura Maria Stancanelli, and Astrid Blom

Across the globe, freshwater ecosystems have experienced a decline in biodiversity resulting from increasing anthropogenic pressure. Over the past decennia the scientific community has developed new and efficient biomonitoring techniques to register these shifts in biodiversity. A promising technique is the capture and analysis of eDNA and eRNA (environmental DNA and RNA; i.e. eNA). eNA constitutes the genetic material released by a host species into the environment in different forms, such as mucous, skin tissue, scales and saliva. However, in lotic ecosystems, such as streams and rivers, detected eNA concentrations can currently not be translated into the spatial and temporal distribution of the associated species. This is due to the lack of knowledge about the processes (e.g. transport and degradation) that influence eNA presence between the moment of release by its host, and the capture of the eNA by the practitioner.

The authors have conducted a set of laboratory experiments to shed light on these processes (i.e. transport and degradation). The objective was to test the influence of flow velocity on concentrations of both eDNA and eRNA. In an annular flume (depth = 19.7 cm; Ø = 3.7 m), which features counter-rotating bottom and top components, we performed eDNA and eRNA degradation experiments under four different flow rates, each with a duration of seven days. The source of eNA originated from water previously inhabited by wildtype zebrafish (Danio rerio). The tested angular velocities of the top lid (νt top lid) are 0.00, 0.35, 1.05 and 1.80 m/s with corresponding velocities of the bottom component in a constant ratio (νt top lidt bottom) as to reduce secondary circulations in the cross section of the flume. Flow velocity measurements were taken using an acoustic Doppler velocimeter (ADV) across the depth of the flume. During the experiment, abiotic measurements (of pH, temperature and conductivity) as well as water samples were taken. eDNA and eRNA concentrations (in copy numbers per volume) were gathered from these water samples by means of ddPCR, targeting a species-specific 73 base pair fragment in the Cytochrome c Oxidase subunit 1 gene. The abiotic measurements are consistent over the duration of the experiment (average conductivity of 520.1 µS, average temperature of 20.3 °C, average pH of 8.3). Concerning the eNA results, a decrease in both eDNA and eRNA concentrations can be noted over the span of the experiment regardless of the rotation speed. Additionally, eRNA concentrations generally decreased in concentration at a higher rate than eDNA concentrations. These experiments advance the understanding of eNA degradation in lotic ecosystems, and bring forth new directions of research to improve inference in eNA-based biomonitoring.

How to cite: Dercksen, J. A., Stancanelli, L. M., and Blom, A.: The effect of flow velocity on eDNA and eRNA concentration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17137, https://doi.org/10.5194/egusphere-egu23-17137, 2023.

EGU23-17175 | Posters on site | BG2.4

Depth trends revisited: Source-induced fragmentation of soil dissolved organic matter 

Gerd Gleixner, Vanessa-Nina Roth, Markus Lange, and Carsten Simon

Although representing only a small portion of all the organic matter being present in soils, dissolved organic matter (DOM) is its most mobile and reactive fraction. Along its transport down the soil profile, DOM interacts with minerals via sorption and aggregation phenomena, and with organisms via uptake, exudation or internal recycling. During this downward passage DOM composition changes too, shifting from a dominant plant/ plant decomposition product character to a more decomposer-driven signature. Such trends have been documented well by ultrahigh resolution mass spectrometry (FT-MS) which reveals thousands of molecular compositions (formulas) in one DOM sample (Roth et al. 2019). However, complementary properties of the molecules that constitute these signatures are largely missing. To test if the downward trend in molecular composition would also affect DOM’s fragmentation sensitivity, and if these effects could obscure the final ecological interpretation, we obtained direct injection FT-MS data with and without source-induced fragmentation (SID) at 45 eV. As a test dataset, we used samples from suction plates installed in three soil profiles (at 5, 10, 20, 30 and 60 cm depth) developed on aeolian sand deposits (podzols, cambisols) in Linde, Brandenburg (Germany). These three sites vary mainly in vegetation cover (grassland, oak, pine). All sites showed a clear depth trend as reported earlier, especially without SID turned on. SID clearly decreased the ion abundance of signals in the molecular weight range 300-500 Da (center ~350), while signals in the range 150-400 Da (center ~ 225) increased; more formulas were detected with SID on. With depth, the population of molecules decreasing/ increasing changed significantly, especially between 30 and 60 cm depth, across all sites. At 60 cm depth, decreasing formulas were more aliphatic while increasing formulas were more confined to a narrow area in the center of the van Krevelen space (“island of stability”). Interestingly, the formulas decreasing significantly across all sites were largely CHO (no other heteroatoms, at all depths), S-containing (at 5, 10, 20 and 30 cm) or P-containing (30 and 60 cm), while formulas increasing were CHO (at all depths) and N-containing ones (at all depths, but mainly at 20 and 30 cm), thereby indicating depth-dependent differences and ionization of new N-containing molecules. In ordination space, sites were clearly differentiated according to SID status, depth and site (in this order), but SID did not affect the separation in terms of depth or site, i.e., the ecological interpretation of DOM fingerprints remained similar independent of the SID status. This means that trends in soil DOM studies are likely not obscured by differences in fragmentation during the electrospray ionization process.

Reference: Roth, V.-N., Lange, M., Simon, C., Hertkorn, N., Bucher, S., Goodall, T., Griffiths, R. I., Mellado-Vázquez, P. G., Mommer, L., Oram, N. J., Weigelt, A., Dittmar, T., Gleixner, G. (2019): Persistence of dissolved organic matter explained by molecular changes during its passage through soil. Nat. Geosci. 12: 755–761.

How to cite: Gleixner, G., Roth, V.-N., Lange, M., and Simon, C.: Depth trends revisited: Source-induced fragmentation of soil dissolved organic matter, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17175, https://doi.org/10.5194/egusphere-egu23-17175, 2023.

EGU23-17392 | ECS | Posters on site | BG2.4

FTICR-mass spectrometry reveals shifts in plant-microorganism interactions over time 

Akanksha Rai, Markus Lange, Oliver Lechtenfeld, and Gerd Gleixner

A plethora of experimental studies manipulating plant diversity have shown a positive effect of biodiversity on ecosystem functions (aboveground biomass, microbial biomass etc.), which strengthens over time. Tightening of the interactions between plant and soil microorganisms over time is considered to be one of the mechanisms responsible for the observed strengthening of the biodiversity-ecosystem functioning (BEF) relationship. Belowground plant-microorganism interactions occur via the exchange of molecules present in the dissolved organic matter (DOM). Hence, an untargeted ultrahigh resolution mass spectrometric analysis of DOM provides an opportunity to understand the mechanisms of interaction between plants and microorganisms in soil. To investigate if and how plants-soil interactions changed over time, we took advantage of the highly replicated DBEF experiment of the Jena Experiment (JE) (Roscher et al., 2004, Vogel et al., 2019). In this experiment, the duration of plant-soil interactions (“history”) and the respective effects of plant diversity on ecosystem functioning were manipulated. Here, we analyzed the water extractable organic matter fraction of topsoil (WEOM; analogous to DOM in this study) using online nano solid phase extraction FTICR-mass spectrometry. While the molecular composition of the WEOM was not impacted by soil history, plant diversity effect differs among the soil history treatments. Specifically, plant diversity had a significant impact on the molecular composition of WEOM in treatments with plant and soils history. In addition, the molecular composition of WEOM in this treatment held a large number of molecular formulae that significantly correlated with plant diversity. This suggests that the strengthening of the biodiversity-ecosystem functioning over time is reflected in the WEOM molecular composition. Thus, the molecular composition of WEOM potentially provides insight into the mechanism underlying the strengthening of biodiversity-ecosystem functioning.

 

 

Roscher, C., Schumacher, J., Baade, J., Wilcke, W., Gleixner, G., Weisser, W. W., ... & Schulze, E. D. (2004). The role of biodiversity for element cycling and trophic interactions: an experimental approach in a grassland community. Basic and Applied Ecology, 5(2), 107-121.

Vogel, A., Ebeling, A., Gleixner, G., Roscher, C., Scheu, S., Ciobanu, M., ... & Eisenhauer, N. (2019). A new experimental approach to test why biodiversity effects strengthen as ecosystems age. In Advances in ecological research (Vol. 61, pp. 221-264). Academic Press.

How to cite: Rai, A., Lange, M., Lechtenfeld, O., and Gleixner, G.: FTICR-mass spectrometry reveals shifts in plant-microorganism interactions over time, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17392, https://doi.org/10.5194/egusphere-egu23-17392, 2023.

EGU23-17512 | Orals | BG2.4 | Highlight

Heterocyte glycolipids: novel tools to obtain high-resolution climate and ecosystem data from lacustrine archives 

Thorsten Bauersachs, James M. Russell, and Lorenz Schwark

Lacustrine sediment sequences represent highly valuable, continuous records of continental climate and ecosystem change. As such, they provide vital information on both the timing and magnitude of long-term climate trends as well as abrupt climate change events and associated biotic responses. Assessing this information, however, is often not straight forward as many conventional lipid-based temperature proxies are affected not only by temperature but also other environmental parameters. Here, we show that the distribution of heterocyte glycolipids (HGs), which are synthesized by N2-fixing heterocytous cyanobacteria and abundantly present in modern freshwater environments, are strongly correlated to lake surface water temperatures. We used these components, in form of the novel organic temperature proxy HDI26, to reconstruct climate variations in tropical East Africa and simultaneously study the impact of climate change on the frequency and intensity of cyanobacterial blooms using a sediment record from Lake Tanganyika (Tanzania). HDI26-reconstructed surface water temperatures varied from ~22 °C to 26 °C in Lake Tanganyika over the last 40,000 years. Lowest temperatures were observed during the Last Glacial Maximum, which is followed by a 3 to 4 °C deglacial warming to yield highest temperatures in the Late Holocene. This general warming trend is interrupted by up to 1 °C cooling during abrupt climate change events (e.g. Younger Dryas). Lipid-based reconstructions of past cyanobacterial activity indicate that although continuously present in Lake Tanganyika, cyanobacteria only became bloom-forming in the late Holocene and in particular during the last 200 years. Our data thus provides new insights and quantitative estimates on Pleistocene to Holocene climate changes in tropical East Africa and associated ecological responses. Given that heterocyte glycolipids are present ubiquitously in polar to tropical lakes and that they have been identified in lacustrine sediments of Early Cenozoic age, the HDI26 and other HG-based indices provide valuable novel tools to extract the highly sensitive climate and ecosystem information that is stored in sediments of lakes worldwide.

How to cite: Bauersachs, T., Russell, J. M., and Schwark, L.: Heterocyte glycolipids: novel tools to obtain high-resolution climate and ecosystem data from lacustrine archives, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17512, https://doi.org/10.5194/egusphere-egu23-17512, 2023.

EGU23-123 * | Orals | GMPV1.3 | Highlight

Dating a world-unique Pacific ruin: Nan Madol 

Chuuan-Chou (River) Shen, Felicia Beardsley, Shou-Yeh Gong, Osamu Kataoka, Minoru Yoneda, Yusuke Yokoyama, Leilei Jiang, Albert Yu-Min Lin, James Fox, Jason Barnabas, Gus Kohler, Zoe T. Richards, and Jean-Paul A. Hobbs

Great Holocene civilizations on Pacific islands were created by Homo sapiens. However, most of the construction histories remain uncertain due to the lack of developed writing system and the limitation of dating techniques. Nan Madol (0.7 km in width and 1.5 km in length), an abandoned city called the “Venice of the Pacific” with over 100 artificial islets, is located on the southeastern coast of island Pohnpei in Micronesia. This world-unique ruin, inscribed onto UNESCO’s World Heritage List in 2016, was built with basalt megaliths and scleractinian coral cobbles. Oral histories and previous charcoal 14C ages suggested that the main construction of Nan Madol of Pohnpei could begin in the 13th or 14th century and ceased at the 16th or 17th century, associated with the rise and fall of the Saudeleur Dynasty. However, after 150 years or more of studies, the timing of construction and the dynasty, and the probable influence of environmental factors, remain unresolved. High-precision U-Th dating techniques, developed at the High-Precision Mass Spectrometry and Environment Change Laboratory (HISPEC), Department of Geosciences, National Taiwan University, were used to date the selected pristine coral infills and reveal the construction time of the two ruins. With over 150 coral ages determined, results show a peak of construction activity during the middle 11th century could be related to the rise of the Saudeleur Dynasty. In the early 15th century, construction activities ceased, associated with the dynasty’s downfall. Our study shows that Nan Madol construction and the rise and fall of the dynasty occurred 2-3 centuries earlier than previously estimated. Moreover, the entire development was dominated by El Niño-Southern Oscillation variability and tectonic-related sea level rise.

How to cite: Shen, C.-C. (., Beardsley, F., Gong, S.-Y., Kataoka, O., Yoneda, M., Yokoyama, Y., Jiang, L., Lin, A. Y.-M., Fox, J., Barnabas, J., Kohler, G., Richards, Z. T., and Hobbs, J.-P. A.: Dating a world-unique Pacific ruin: Nan Madol, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-123, https://doi.org/10.5194/egusphere-egu23-123, 2023.

EGU23-265 | Orals | GMPV1.3

Mineral/Fluid interaction as a potential bias in calcite U-Pb dating 

Riccardo Lanari, Anda Buzenchi, Alessandro Bragagni, Bruno Dhuime, Mauro Brilli, Chiara Del Ventisette, Massimo Mattei, Sandro Conticelli, and Riccardo Avanzinelli

The application of U-Pb dating method performed on calcite has exponentially increased over the last years, since constraining the age of the crystallization for such syn-kinematic minerals, would provide a specific timing of faults movement. The potential gain of this approach is evident but the robustness of the U-Pb method performed on calcites has been not yet systematically tested.  Here, we firstly demonstrated that a mineral/fluid interaction indeed affects the regression of the 238U/206Pb and 207Pb/206Pb data-points and therefore the age; and secondly, we propose an innovative application of U-Pb dating method and a new strategy to identify and reject analytically robust isochrons.

We explore 36 samples, combining U-Pb dating performed with different methods along with carbon and oxygen stable isotopes compositions measured on the same fibres of calcite. The extremely high precision 207Pb/206Pb measured by Thermal Ionisation Mass Spectrometry  revealed that every sample experienced a certain degree of fluid interaction. We find no correlation between 238U/206Pb and the spread in δ18O. The higher spread in δ18O is instead coupled with a remarkable scattered data-points that yield U-Pb ages calculated with the different methods on the same samples with a large variability. In conclusion, our study demonstrates that great care must be taken when considering radiometric ages made on calcite since LA-ICP-MS large uncertainties might obscure the isotopic reorganization.

How to cite: Lanari, R., Buzenchi, A., Bragagni, A., Dhuime, B., Brilli, M., Del Ventisette, C., Mattei, M., Conticelli, S., and Avanzinelli, R.: Mineral/Fluid interaction as a potential bias in calcite U-Pb dating, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-265, https://doi.org/10.5194/egusphere-egu23-265, 2023.

EGU23-4234 | Orals | GMPV1.3

Application of carbonate U-Pb geochronology in dating of diagenesis and hydrothermal activity 

Zhongwu Lan, Nick M W Roberts, Shitou Wu, Fangyue Wang, Hao Wang, Rong Cao, Zhensheng Li, Ying Zhou, Kaibo Shi, and Bo Liu

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb geochronology of calcite has been an emerging research direction in recent years that has been widely applied to various disciplines, such as dating of brittle deformation, biological biomineralization, oceanic crust alteration, and hydrocarbon migration. The method has the advantage of quickly locating regions of relatively high uranium content and radiogenic lead that avoids the time-consuming procedures traditionally required for isotope dilution methods. Herein, we show how this method is successfully applied to dating of diagenesis and hydrothermal activity in Precambrian-Phanerozoic sedimentary rocks, but with a note of caution that the susceptibility of the calcite U-Pb isotope system to fluid activities means interpretation of calcite U-Pb data and selection of calcite standard should be cautioned. We demonstrate the following case studies: LA-ICP-MS calcite U-Pb geochronology has aided in defining the Mesoproterozoic-Neoproterozoic boundary (ca. 1010 Ma) in North China Craton. It also constrains the timing of calcite infillings in the Ediacaran cap carbonate to be ca. 636 Ma, indicating an early diagenetic origin and thus confirming a methane seepage hypothesis. Two episodes of hydrothermal activity (ca. 290 Ma and ca. 250 Ma) have been recognized from the Cambrian carbonate in the Tarim region, which was induced by the Permian Tarim Large Igneous Province (LIP) and Indosinian orogeny, respectively.

How to cite: Lan, Z., M W Roberts, N., Wu, S., Wang, F., Wang, H., Cao, R., Li, Z., Zhou, Y., Shi, K., and Liu, B.: Application of carbonate U-Pb geochronology in dating of diagenesis and hydrothermal activity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4234, https://doi.org/10.5194/egusphere-egu23-4234, 2023.

The global-scale glacial events recorded by diamictite and cap carbonate couplets occurred in the late Neoproterozoic and has been recognized on at least 15 paleo-continents. Diamictite and cap carbonate couplets play a pivotal role in establishing regional stratigraphic correlations and understanding the extreme climatic conditions and glacial-interglacial cycles of the Neoproterozoic glaciation. Here we report newly discovered Neoproterozoic glaciogenic diamictite and cap carbonate couplet in the Longshoushan area at the southwestern margin of the Alxa Block, NW China. Based on detailed stratigraphic and sedimentologic studies, we identified massive and stratified diamictites at the bottom of the Hanmushan Group, both with poorly sorted and rounded gravels. The presence of glacial striations and ice-rafted dropstones in stratified diamictites supports a glaciogenic origin. The upward transition from massive diamictites to stratified diamictites indicates the process of glacier retreat. The occurrence of thin-bedded phyllites in the stratified diamictites suggests a short-term deglaciation during the glaciation. The 2- to 2.6-m-thick cap carbonates cover the stratified diamictites and consist of thinly laminated microcrystalline dolomites. The basal cap carbonates contain closely linked sheet cracks, cemented breccias, tepee-like structures and cavities. The cap carbonates show high-resolution 13CPDB chemostratigraphy and negative δ13C values (ca. −2.9 to −4.1‰), typical of the Marinoan cap carbonates. Regional sedimentary characteristics and the C-O isotope values suggest that the diamictites and cap carbonate couplet in the Alxa Block likely correspond to the Marinoan glaciation and subsequent deglaciation (ca. 635 Ma), not the previously assumed Ediacaran glaciation. Thus, the diamictite and cap carbonate sequence marks the Cryogenian-Ediacaran boundary in the Alxa Block and provides evidence for further stratigraphic correlation and investigation. This work was financially supported by NSFC projects (grants 42072264, 41730213, 41902229, 41972237) and Hong Kong RGC GRF (17307918).

How to cite: Shao, D., Han, Y., Li, M., Lu, L., Cao, X., and Ju, P.: Discovery of Neoproterozoic glaciogenic diamictites and cap carbonate couplet in the Alxa Block, NW China: Evidence from stratigraphic, sedimentologic and geochemical studies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4758, https://doi.org/10.5194/egusphere-egu23-4758, 2023.

There has been considerable debate as to whether the Korean peninsula has evolved as part of the Sino-Korean Craton since Neoarchean or whether it is a product of the amalgamation of several continental fragments in the early Mesozoic Era. The relationship between the Neoproterozoic Okcheon Metamorphic Belt (OMB) and the Early Paleozoic Tabaeksan Basin (TB) in the central region of the Korean Peninsula has the potential to provide an answer to this question. Various carbonate rocks appear in OMB, showing unique carbon isotope values ​​according to their geologic age.

The Hyangsanni Dolomite is distributed around the Gyemyeongsan Formation with metavolcanics of about 860 Ma. The Hyangsanni Dolomite has δ13C values between +2.9 ‰ and +6.2 ‰, markedly higher than the Cambro-Ordovician values, and are consistent with the Neoproterozoic values. Considering the low values ​​of 86Sr/87Sr, the deposition period of the Hyangsanni Dolomite is judged to be Tonian before the Sturtian Glaciation.

The Geumgang Limestone has a maximum thickness of several tens of meters adjacent to the diamictite layer proposed as a glacial deposit but shows a very extensible distribution. The δ13C values ​​of the Geumgang Limestone range from -12.25 to -7.88 ‰, suggesting that they may be cap carbonates. However, whether their deposition was related to the Sturtian Glaciation or the Marinoan Glaciation is not yet known.

Between the Cryogenian Seochangri Formation of OMB and the Cambrian Jangsan Formation of TB are carbonate rocks previously considered Ordovician. However, carbon and oxygen isotope values analyzed in this study require different interpretations. Zones with δ13C values ​​ranging from -3.4 to +1.3 ‰ agree with Ordovician seawater values. However, over a larger area, δ13C values ​​show mostly positive values ​​from +1.9 to +7.8 ‰. Also, a significant negative excursion of δ13C values ​​down to -6.9 ‰ occurs near the highest values ​​measured. These values correlate with Ediacaran or Early Cambrian carbonates better than Ordovician seawater. It is the first to discover the possible carbonate rocks of Ediacaran or Early Cambrian in South Korea, supporting that the Neoproterozoic OMB and Early Paleozoic TB have a tectonic evolutionary history of continuous deposition rather than an assembly of different continental fragments.

How to cite: Park, K.-H. and Ha, Y.: Carbon Isotopic Composition of Carbonates of the Okcheon Metamorphic Belt in South Korea from Neoproterozoic to Early Cambrian Potential: Geological and Tectonic Significance, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5196, https://doi.org/10.5194/egusphere-egu23-5196, 2023.

EGU23-5345 | ECS | Posters virtual | GMPV1.3

Calcite TLM and LSJ07: two natural reference materials for micro-beam U-Pb geochronology and C, O isotope ratio measurements 

Shitou Wu, Yueheng Yang, Rolf Romer, Nick M W Roberts, and Zhongwu Lan

U-Pb geochronology of calcite using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is an emerging method, with potential applications to a vast array of geological issues. Accurate LA-ICP-MS calcite U-Pb dating requires matrix-matched RMs for the correction of instrumental mass bias of Pb/U ratios. Several materials are currently being used as RMs, including WC-1, Duff Brown Tank, ASH-15, JT, and AHX-1A. In this study, we will give a brief introduction of LA-ICP-MS lab at IGGCAS for carbonate U-Pb dating. Meanwhile we further characterized two calcite reference materials for micro-beam U-Pb geochronology and and C, O isotope ratio measurements. LA-ICP-MS multiple spot analyses (> 400) at different regions of materials reveal that calcite TLM and LSJ07 are homogeneous for the U-Pb age with 220.72 +/-0.98 Ma and 26.54+/-0.41 Ma respectively. SIMS multiple spot analyses (> 100) reveals calcite TLM is homogeneous for the O isotope ratio at mm special resolution. MAT 253 gives a bulk result of δ18O =-14.20 ‰. LA-MC-ICP-MS multiple spot analyses (> 200) reveals calcite TLM and LSJ07 are homogeneous for the C and O isotope ratio at mm special resolution. MAT 253 gives bulk results of δ13C =-1.53 ‰ andδ13C =-0.33 ‰ for TLM and LSJ07 respectively. These two materials represent a useful addition to the currently distributed WC-1, Duff Brown Tank, ASH-15, JT, and AHX-1A for micro-analytical techniques of U-Pb geochronology and C, O isotope ratio measurements.

How to cite: Wu, S., Yang, Y., Romer, R., Roberts, N. M. W., and Lan, Z.: Calcite TLM and LSJ07: two natural reference materials for micro-beam U-Pb geochronology and C, O isotope ratio measurements, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5345, https://doi.org/10.5194/egusphere-egu23-5345, 2023.

EGU23-5865 | ECS | Posters virtual | GMPV1.3

Dating and characterizing carbonate rocks in Upper Permian reef-dolostone reservoir systems in Sichuan Basin, southwest China: implications for porosity evolution 

Binsong Zheng, Renjie Zhou, Chuanlong Mou, Jianxin Zhao, and Daryl Howard

Large gas fields are hosted in Upper Permian reef-dolostone bodies in Sichuan Basin, southwest China, among which the Puguang gasfield is the largest marine-carbonate gas system in China. The reservoir rocks are mainly composed of intensively dolomitized sponge-reefs constructed within platform margin reef facies in northern Sichuan Basin. Although major reservoir spaces consist of intercrystal pores, dissolved pores and vugs, the knowledge regarding the evolution of porosities is still limited. Using multiple methods, this study focuses on characterising different phases of carbonates (calcite and dolomite) to understand the dolomitization model and porosity evolution of the Upper Permian Panlongdong reef cropped out in northeastern Sichuan Basin. Two-dimensional high-resolution visualization of element contents in reef dolostones was provided by synchrotron-radiation Micro X-ray fluorescence elemental mapping. O and Sr isotope analysis was carried out to trace the nature of fluids during dolomitization. Laser ablation ICP-MS U-Pb dating was performed on dolomite minerals and secondary calcite cements. Our results suggest that: (1) dolomitization of the reef occurred in the early Middle Triassic (~245 Ma) due to the downward reflux of hypersaline seawater rich in Mg2+, accompanied by a significant increase in porosity because of the selective dissolution of low-Mg calcites; (2) in the Late Triassic, continental collision between South and North China plates induced uplifting and formation of a large quantity of (micro)fractures in northern South China, followed by Sr-depleted freshwater passing through the reef, leading to precipitation of secondary calcite cements (~206 Ma).

How to cite: Zheng, B., Zhou, R., Mou, C., Zhao, J., and Howard, D.: Dating and characterizing carbonate rocks in Upper Permian reef-dolostone reservoir systems in Sichuan Basin, southwest China: implications for porosity evolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5865, https://doi.org/10.5194/egusphere-egu23-5865, 2023.

EGU23-7797 | ECS | Orals | GMPV1.3

H2O-present melting curve of magnesite and trace element distribution during melting of (dry) magnesite and calcite in the upper mantle 

Melanie J. Sieber, HansJosef Reichmann, Robert Farla, Oona Appelt, Marcus Oelze, Christian Lathe, and Monika Koch-Müller

The presence of magnesite (MgCO3) in the Earth’s mantle plays a fundamental role in reducing the melting point of the mantle [1] and forming carbonate‑rich melts such as kimberlites and carbonatites [2]. The melting curve of (dry) magnesite is well constrained [3, 4], but melting of magnesite in the presence of H2O, providing the basis for more complex (natural) systems, is poorly understood from some quenched experiments [5]. Also, the distribution of trace elements such as Li, Sr, Pb, and rare earth elements during melting of magnesite is poorly considered in models that evaluate the trace element budget of carbonate‑rich melts parental to kimberlites [6].

Here we report, first, the H2O‑present melting curve of magnesite between 2 and 12 GPa. The melting curve of magnesite mixed with 16 wt% brucite was established by in ‑ situ X‑ray diffraction measurements using the large volume press at P61B at PETRA III (DESY). Second, we report trace element partitioning data for congruent melting of calcite and incongruent melting of magnesite producing carbonate melt and periclase between 6 and 9 GPa. Those results were obtained from quenched experiments using a rocking multi‑anvil press at the GFZ overcoming equilibrium and quenching problems in previous studies [7].

 

1          Dasgupta and Hirschmann, The deep carbon cycle and melting in Earth's interior. Earth and Planetary Science Letters, 2010. 298(1-2): p. 1-13.

2          Jones, Genge, and Carmody, Carbonate Melts and Carbonatites. Reviews in Mineralogy and Geochemistry, 2013. 75(1): p. 289-322.

3          Solopova, Dubrovinsky, Spivak, Litvin, and Dubrovinskaia, Melting and decomposition of MgCO3 at pressures up to 84 GPa. Physics and Chemistry of Minerals, 2014. 42(1): p. 73-81.

4          Müller, Koch-Müller, Rhede, Wilke, and Wirth, Melting relations in the system CaCO3-MgCO3 at 6 GPa. American Mineralogist, 2017. 102(12): p. 2440-2449.

5          Ellis and Wyllie, Carbonation, hydration, and melting relations in the system MgO-H2O-CO2 at pressures up to 100 kbar. American Mineralogist, 1979. 64(1-2): p. 32-40.

6          Girnis, Bulatov, Brey, Gerdes, and Höfer, Trace element partitioning between mantle minerals and silico-carbonate melts at 6–12GPa and applications to mantle metasomatism and kimberlite genesis. Lithos, 2013. 160-161: p. 183-200.

7          Buob, Experiments on CaCO3-MgCO3 solid solutions at high pressure and temperature. American Mineralogist, 2006. 91(2-3): p. 435-440.

How to cite: Sieber, M. J., Reichmann, H., Farla, R., Appelt, O., Oelze, M., Lathe, C., and Koch-Müller, M.: H2O-present melting curve of magnesite and trace element distribution during melting of (dry) magnesite and calcite in the upper mantle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7797, https://doi.org/10.5194/egusphere-egu23-7797, 2023.

EGU23-9499 | Orals | GMPV1.3

TILDAS measurement of multiple clumped isotope ratios in carbonates: progress and new horizons 

David Nelson, Scott Herndon, Zhennan Wang, Jay Quade, and David Dettman

Isotopic analysis using high resolution Isotope Ratio Laser Spectroscopy (IRLS) has been shown to be advantageous to multiple geochemical applications during the last decade.  These advances include isotopic analysis of the bulk isotopic compositions of water, carbon dioxide, methane and nitrous oxide.  More recently, laser spectroscopy has been used by several groups to examine the isotopic compositions of methane, carbon dioxide and nitrous oxide when carrying two rare isotopes (so called clumped isotopes).   Our recent work using Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS) has demonstrated highly accurate (~0.01 ‰) measurements of the clumped (16O13C18O or 638 in HITRAN isotope notation) isotopic composition of carbon dioxide derived from carbonate samples with spectroscopic measurement times of ~30 minutes using a dual laser spectrometer.  That spectrometer is optimized for the measurement of the four isotopologues required to calculate Δ638 (or Δ47).  We present here our parallel project to develop a novel dual laser isotope analyzer capable of measuring multiple carbon dioxide isotopic signatures simultaneously.   Specifically, we simultaneously measure the isotopic abundances of the three most abundant clumped isotopologues (Δ638, Δ637 and Δ828) as well as 17O oxygen excess or Δ17O.  Δ638 and Δ828 correspond to the quantities Δ47 and Δ48 when measured by isotope ratio mass spectroscopy (IRMS).   Δ17O is very difficult to measure with IRMS and Δ637 has not been previously measured with any technique to the best of our knowledge.  The new instrument utilizes carefully chosen spectral windows, operates at low sample pressure and exploits automated laser frequency hopping.  This prototype instrument simultaneously measures seven isotopologues of carbon dioxide: 626, 636, 628, 627, 638, 637 and 828.  Our preliminary results for Δ828 (or Δ48) are displayed as an Allan-Werle plot which shows that the precision in the measurement of Δ828 is ~0.09‰ for a single 3 minute sample measurement referenced to a working reference gas.  The plot shows that instrumental drift is very small over periods of several hours and that the precision can be improved to 0.03‰ by processing 10 sub-samples or to 0.01‰ by processing 100 sub-samples.  These measurements are preliminary and somewhat idealized but show promise for this new technique.

How to cite: Nelson, D., Herndon, S., Wang, Z., Quade, J., and Dettman, D.: TILDAS measurement of multiple clumped isotope ratios in carbonates: progress and new horizons, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9499, https://doi.org/10.5194/egusphere-egu23-9499, 2023.

For fundamental thermodynamic reasons, 13C-18O bonds in carbonate minerals formed under isotopic equilibrium conditions are more abundant than predicted for a random distribution of isotopes, yielding positive Δ47 clumped-isotope signatures which decrease as a function of formation temperature [1]. Although most Earth-surface carbonates are unlikely to achieve complete isotopic equilibrium, Δ47 values of many biogenic and abiotic calcites formed under very different crystallization conditions (and with irreconcilable water-calcite oxygen-18 fractionation laws) appear to follow indistinguishable temperature calibrations, as independently documented by various groups over the years [e.g., 2-4]. That is not to say that all groups agree on a single calibration linking Δ47 and temperature, and a recent comparison of 14 reprocessed calibration studies still found evidence for statistically significant inter-laboratory discrepancies [3]. Rigorous statistical tests aiming to prove or disprove consistency between Δ47 calibrations are particularly challenging because of potentially large and non-independent analytical errors associated with standardization procedures [5], and even in some cases by large correlations in the uncertainties of estimated formation temperatures, making classical least-squares regression approaches ill suited to model these calibration data sets.

Here I propose a new formulation for least-squares regression of data with an arbitrarily complex covariance structure linking all predictor and response observations, generally applicable to all sorts of geochemical data. I use this “Omnivariant Generalized Least-Squares” (OGLS) approach to compare 7 published Δ47 calibration data sets which have been (re)processed according to the newly established InterCarb Carbon Dioxide Equilibrium Scale (I-CDES), supposedly allowing robust comparisons between Δ47 measurements across laboratories [6]. None of these reprocessed calibration data sets are found to deviate significantly from a single, unified regression line, with an overall reduced chi-squared statistic (adjusted for data covariance according to OGLS) of 0.8 consistent with slightly overestimated uncertainties on temperature constraints. This finding marks another milestone in the 17-year-long progress of Δ47 thermometry, which has now solved most of the methodological challenges standing in the way of its widespread application to many scientific issues. In short: carbonate clumped-isotope thermometry is all grown up now.

[1] Schauble et al. (2006) 10.1016/j.gca.2006.02.011
[2] Kele et al. (2015) 10.1016/j.gca.2015.06.032
[3] Petersen et al. (2019) 10.1029/2018GC008127
[4] Anderson et al. (2021) 10.1029/2020GL092069
[5] Daëron (2021) 10.1029/2020GC009592
[6] Bernasconi et al. (2021) 10.1029/2020GC009588

How to cite: Daëron, M.: Making the Case for Reconciled Δ47 Calibrations Using Omnivariant Generalized Least-Squares Regression, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10066, https://doi.org/10.5194/egusphere-egu23-10066, 2023.

EGU23-10706 | ECS | Posters virtual | GMPV1.3

Geochemical and geochronologic investigations into carbonate veins from historical drill cores in undercover Mt Isa, NW Queensland 

Xingyu Chen, Renjie Zhou, David Wood, Daniel Stirling, Kamalendra Jhala, Ira Friedman, Matt Valetich, and Lizzy Philippa

This study investigates carbonate veins in five drill cores archived at Geological Survey of Queensland from NW Queensland, ~100 km south of Mt Isa, with geochemical and geochronologic approaches in order to characterise origins of fluids and their mineralisation potentials. Carbonate veins are mostly hosted in Proterozoic age (approximately 1800-1650 Ma) supra-crustal rocks, which are inferred from geophysics to be covered by 350 to 2,000 m of younger sedimentary rocks of the Eromanga and Georgina basins. Data regarding the nature of fluid activities is important for comparison between the undercover southern Mt Isa and outcropped Mt Isa mineral district, which is a world-class mineral province.

Multiple-phase carbonate veins (mostly calcite and dolomite) are identified, including late formed brittle veins, pyrite/chalcopyrite mineralisation-bearing carbonate veins, and calcite hosted in crackle breccias. Samples are prepared into one-inch polished mounts and studied with SEM-EDS, and in situ laser ablation ICP-MS for geochemical and U-Pb geochronological studies. Relatively pure calcite phases are also prepared with microdrill for stable isotope C and O analysis. Trace element datasets suggest enrichments in rare earth elements and ytterbium (REE+Y) with distinct negative Eu anomalies. Stable isotopes range ~-5 to – 15 (δ13CVPDB‰) and ~10 to 25 (δ18OVSMOW‰). Trace element data, Yb/La and Yb/Ca ratios, and stable isotope signatures imply that these carbonate veins have hydrothermal origins. 206Pb/238U geochronology data has indicated multi-phase calcite formation ranging from the late Neoproterozoic to Cretaceous. Our results provide a novel dataset to demonstrate the use of carbonate veins in revealing fluid activities in a mineral district and help the future exploration of critical mineral deposits in undercover southern Mt Isa when interpreted against regional structural data and well-documented mineralisation events in the northern Mt Isa district.

 

How to cite: Chen, X., Zhou, R., Wood, D., Stirling, D., Jhala, K., Friedman, I., Valetich, M., and Philippa, L.: Geochemical and geochronologic investigations into carbonate veins from historical drill cores in undercover Mt Isa, NW Queensland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10706, https://doi.org/10.5194/egusphere-egu23-10706, 2023.

EGU23-12216 | ECS | Orals | GMPV1.3

Triple oxygen isotope analyses of carbon dioxide, water and carbonates by VCOF-CRDS technique 

Justin Chaillot, Mathieu Daeron, Mathieu Casado, Amaelle Landais, Marie Pesnin, and Samir Kassi

Oxygen-17 excess (Δ17O) in carbonate minerals can provide valuable insights into past continental and marine environments, long-term trends in the temperature and oxygen-isotope composition of ancient oceans, isotopic disequilibrium effects in biogenic and abiotic carbonates, and cryptic diagenesis. Triple oxygen isotope analyses of carbonates and/or CO2 using isotope-ratio mass spectrometers (IRMS) remain challenging, however, because of isobaric interference between 16O13C16O and 16O12C17O. Using spectroscopic methods, the abundance of each CO2 isotopologue may be directly quantified, potentially providing simple, non-destructive measurements of δ13C, δ18O and Δ17O on small samples of CO2.

Here we report new data characterizing the application of VCOF-CRDS (V-shaped Cavity Optical Feedback - Cavity Ring Down Spectroscopy [1]) to the analysis of small samples (<40 μmol) of pure CO2, as typically produced by phosphoric acid digestion of carbonate minerals.

Instrumental drifts from various sources are observed to bias apparent isotopic abundances by a few tens of ppm, but these drifts are slow enough that they may be precisely monitored and corrected for by repeated analyses of a working gas interspersed between other analyses, requiring only ~8 mn per aliquot and 30 mn between consecutive “unkown” analyses. This approach was tested by analyzing repeated aliquots of another CO2 tank with a different isotopic composition, yielding instrumental repeatabilities of 12 ppm, 13 ppm and 7.4 ppm for δ13C, δ18O and Δ17O, respectively (95 % CL, Nf = 66).

The accuracy of our measurements was tested over a wide range of Δ17O values spanning 130 ppm, by analyzing CO2 equilibrated at 25 °C with different waters whose triple oxygen compositions were independently constrained in the SMOW-SLAP scale by IRMS measurements and by simple nonlinear mixing predictions. We find that our Δ17O measurements are well within analytical uncertainties of predicted values (RMSE = 1.2 ppm), with analytical repeatabilities (including isotopic equilibration and gas manipulation) of 8.6 ppm (95 % CL, Nf = 27).

We will also report the results of our ongoing investigation regarding the isotopic fractionation and analytical noise associated with different acid digestion protocols at different reaction temperatures, and the triple oxygen composition of various international reference materials already used for δ13C, δ18O, and clumped-isotope measurements.

Based on these results, we conclude that VCOF-CRDS offers excellent accuracy, along with state-of-the-art levels of analytical precision/linearity, for straightforward analyses of 17O excess in CO2, water, and carbonate minerals.

[1] Stoltmann et al. (2017) 10.1021/acs.analchem.7b02853

How to cite: Chaillot, J., Daeron, M., Casado, M., Landais, A., Pesnin, M., and Kassi, S.: Triple oxygen isotope analyses of carbon dioxide, water and carbonates by VCOF-CRDS technique, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12216, https://doi.org/10.5194/egusphere-egu23-12216, 2023.

EGU23-12645 | Posters on site | GMPV1.3

The onset of the Ediacaran Nama Group sedimentation in Namibia? 

Inigo Andreas Müller, Fabio Messori, Marcel Guillong, Giovan Peyrotti, Michael Schirra, Elias Samankassou, Ulf Linnemann, Mandy Hofmann, Johannes Zieger, Agathe Martignier, Anne-Sophie Bouvier, Torsten Venneman, Kalin Kouzmanov, and Maria Ovtcharova

The final stage of the Proterozoic, the Ediacaran, shields fascinating insights on the development and dispersal of complex metazoans related to dramatic compositional changes in the atmosphere and hydrosphere.  Alternating sequences of siliciclastic and carbonate rocks of the Namibian Nama basin record the final stage of the Ediacaran and contain a vast amount of soft-bodied fauna, as well as some of the first biocalcifying organisms. However, the sparsity of ash beds at the base of the Nama group, preclude accurate and precise constraints on the onset of the Ediacaran biota in Nama group and correlation with chemo stratigraphic records worldwide.  

Due to the scarcity of ash layers, we apply U-Pb dating to carbonate rocks especially from the lower stratigraphic sections of the Nama Group combining the spatial resolution of LA-ICP-MS and the high-precision ID-TIMS U-Pb dating. The combination with mineralogical and geochemical techniques (d13C, d18O, XRD, SEM, EPMA, CL imaging, LA trace element transects, Raman spectroscopy, clumped isotope thermometry, QEMSCAN, SIMS) enables us to better understand the nature of the analyzed carbonates to distinguish between more pristine and diagenetic phases.

This study elaborates on the potential and limitations of carbonate U-Pb dating for improved stratigraphic correlation on these ancient pre-Cambrian marine carbonates from the Nama Group.

How to cite: Müller, I. A., Messori, F., Guillong, M., Peyrotti, G., Schirra, M., Samankassou, E., Linnemann, U., Hofmann, M., Zieger, J., Martignier, A., Bouvier, A.-S., Venneman, T., Kouzmanov, K., and Ovtcharova, M.: The onset of the Ediacaran Nama Group sedimentation in Namibia?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12645, https://doi.org/10.5194/egusphere-egu23-12645, 2023.

Carbonate veins are ubiquitous in many ore deposits and are often interpreted as a late stage or cross cutting fluid flow events in the ore deposit history. Faults accommodate rock displacement and the resulting zones of weakness act as conduits for magma and localised magmatic-hydrothermal fluid flow, leading to the formation of ore deposits. Dating of both low temperature veins and brittle fault material has been notoriously difficult because of a lack of ‘datable’ material. Using innovative techniques, it is now possible to date carbonate with the U-Pb isotopic system.

Here we use in-situ U-Pb carbonate geochronology to date a variety of fault material and mineralised and unmineralised veins within a major fault-controlled Cu-Au-Mo porphyry system in the central Yukon, Canadian Cordillera. Over 50 samples have been dated, revealing a long history of faulting and fluid flow in the deposit spreading over 10s of millions of years between ~75 Ma and <20 Ma. We combine petrography, U-Pb carbonate geochronology, trace element geochemistry, and clumped isotope analysis to interpret the full temperature-time evolution of the fluids within the deposit. Our results show the carbonate veins crystallised during the main ore-forming event at ~75 Ma. Subsequently, there was a prolonged period of fault-controlled fluid pulsing that likely concentrated metallic minerals in the deposit. The findings show that carbonate veins are not always late features within ore deposits and are an underutilised resource for understanding the full temporal and fluid evolution of a system. Carbonate U-Pb geochronology is therefore potentially incredibly useful for telling the previously untold and long history of fluid flow in a variety of deposit types.

How to cite: Mottram, C., Kellett, D., Dennis, P., and Clog, M.: Longevity of fault-controlled fluid flow within a Cu-Au-Mo porphyry (Yukon, Canada) revealed by coupled U-Pb carbonate geochronology and clumped isotope analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13236, https://doi.org/10.5194/egusphere-egu23-13236, 2023.

EGU23-13798 | ECS | Posters virtual | GMPV1.3

Evolution of the hydrothermal fluids of the Yolindi Fe-Cu skarn deposit, Biga peninsula, NW Turkiye: Evidence from carbon-oxygen isotopic variations of calcite minerals 

Mustafa Kaya, Mustafa Kumral, Amr Abdelnasser, Cihan Yalçın, Sercan Öztürk, Hatice Nur Bayram, and Beril Tanç-Kaya

This work deals recently with the carbon (δ13C) and oxygen (δ18O) isotopic variations in the calcite associated with the hydrothermal mineralization to comprehend the nature of the ore fluid and its source and the evolution of the Yolindi Fe-Cu skarn deposit at North of Biga peninsula (NW Turkiye). The Yolindi area is made up of Torasan Formation (marble, hornfels, phyllite, and schist) which was intruded by Oligocene Hallaçlar volcanic rocks and later early Miocene Şaroluk plutonic rocks. The Yolindi Fe-Cu skarn deposit has been formed along the eastern contact of Şaroluk pluton with the Torasan Formation having widespread prograde and/or retrograde skarn, silicic, and carbonate (calcite) alteration. The prograde skarn is less observed and characterized by formation of garnet with subordinate magnetite. While, the retrograde skarn is highly extensive having epidote, actinolite, chlorite, and carbonate including pyrite, magnetite, chalcopyrite, and specular hematite with subordinate sphalerite and galena. Malachite, azurite, goethite, hemimorphite, and cerussite represent the supergene minerals which locally replaced Fe-oxide and Fe-Cu±Zn±Pb sulfide minerals. At the Yolindi Fe-Cu skarn deposit, carbon and oxygen isotope ratios of calcite minerals from the exoskarn zone are -15.5 to -2.0 ‰ relative to PDB and 0.9 to 17.9 ‰relative to V-SMOW, respectively. Furthermore, it was inferred from the calculated carbon isotopic composition of an ore-forming fluid (δ13CCO2 = -12.7 to +0.8 ‰) that the carbon in the fluid is identical to the reduced carbon in sedimentary and metamorphic rocks. However, the calculated fluid's δ18OH2O values—which vary from 0.9 to 17.2 ‰VSMOW—indicate a mixture of metamorphic and magmatic origins for the hydrothermal fluid. This fluid mixing which has high range of C-O isotopic compositions has been due to a temperature effect along with either CO2 outgassing or fluid/rock interactions. Additionally, the mineralizing fluid is most likely derived from the metamorphic dehydration of carbonate rocks in the Torrasan Formation during Yolindi skarn formation.

Keywords: carbon (δ13C) and oxygen (δ18O) isotope; Fe-Cu Yolindi skarn deposit; Biga peninsula; NW Turkiye

How to cite: Kaya, M., Kumral, M., Abdelnasser, A., Yalçın, C., Öztürk, S., Bayram, H. N., and Tanç-Kaya, B.: Evolution of the hydrothermal fluids of the Yolindi Fe-Cu skarn deposit, Biga peninsula, NW Turkiye: Evidence from carbon-oxygen isotopic variations of calcite minerals, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13798, https://doi.org/10.5194/egusphere-egu23-13798, 2023.

EGU23-15731 | ECS | Posters on site | GMPV1.3

Variability of (234U/238U) in surface water and tufa deposits: A study in the Mono Basin, California, USA 

Ke Lin, Sidney R. Hemming, Guleed Ali, In-Tian Lin, Chih-Chieh Su, Scott W. Stine, N. Gary Hemming, and Xianfeng Wang

Uranium concentrations and 234U/238U activity ratios (δ234U) of Earth’s surface waters can provide independent and complementary information on changes in weathering regime and hydroclimate. The response of δ234U variation in surface waters in US Great Basin to climate change however remains unclear, which brings ambiguities in interpreting δ234U in aquatic carbonate deposits. Here, we analysed U concentration and δ234U in a suite of surface waters (creeks, springs and lake) as well as tufa deposits from the last glacial lake highstands in the Mono Basin, California, USA to assess the modern uranium budget in the lake water and the controlling factors on its δ234U. We find that U concentrations in groundwater springs are about one order of magnitude higher than those of creek waters. Hence, even though springs only deliver about 15% of annual inflow to the lake, they contribute 70% of U in the lake water. The residence time of U in lake water is calculated to be approximately 15,000 years, on the same order as those of Li, Na, and Cl, but significantly longer than those of alkaline earth elements. The δ234U in Mono Lake water is 180‰, same as in modern-day tufa deposits. The δ234U in lake highstand tufas is ~ 220‰, suggesting much more enhanced physical weathering associated with mountain glacial activities in the basin, even though chemical weathering was also stronger due to increased precipitation. On the other hand, the higher δ234U values (~ 250‰) in modern creeks and springs is consistent with the overall dry environment and stronger physical weathering in the basin. The 40‰ decrease in δ234U of lake water however cannot be explained by radiative decay. We hypothesis that lake water was more frequently stratified in the past, during the last glacial in particular, and the resulted anoxic environment in deep lake water has probably facilitated precipitations more enriched in 234U. 

How to cite: Lin, K., Hemming, S. R., Ali, G., Lin, I.-T., Su, C.-C., Stine, S. W., Hemming, N. G., and Wang, X.: Variability of (234U/238U) in surface water and tufa deposits: A study in the Mono Basin, California, USA, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15731, https://doi.org/10.5194/egusphere-egu23-15731, 2023.

EGU23-15952 | ECS | Posters on site | GMPV1.3

Crack-seal veins: records of 600-million-year complex tectonic and fluid flow evolution in Saudi Arabia 

Adhipa Herlambang, Ardiansyah Koeshidayatullah, Chaojin Lu, Abduljamiu Amao, Abdulwahab Bello, Faisal Al-Ghamdi, Muhammad Malik, and Khalid Al-Ramadan

The Ediacaran Period (635-538 Ma) was marked by considerable tectonic activity, including the end of the Pan-African episode – a long interval of mountain building, rifting, and reorganization spanning most of the Neoproterozoic Era. In Saudi Arabia, the Ediacaran outcrops were developed and preserved in several isolated half-grabens linked to the Ediacaran to early Cambrian Najd strike-slip fault system. This fault system manifested, particularly in the study area, as intensive fractures with a distinctive crack-seal veins morphology. Understanding the mechanism and origin of such fractures could provide unique insights into the structural evolution and paleo fluid flow throughout the history of the Arabian Plate. However, no studies have focused on different structural-controlled diagenetic processes in the Neoproterozoic sequences across the Arabian Plate. Here, we examined precipitated veins along a well-exposed 300 m thick Ediacaran host rock exposure by integrating high-resolution geochemical analyses, carbonate clumped isotopes, fluid inclusions, advanced petrography analysis of Cathodoluminescence microscopy to unravel the structural diagenesis of these Ediacaran strata. The δ18O and δ13C of the carbonate host rocks vary from -11.79 to -7.83‰, and -0.58‰ to 1.1‰, respectively. The estimated paleotemperature of the host rock derived from the clumped isotope is 47-60°C. Furthermore, the current results show that the calcite veins appear in different stages, orientations, geometries, and mineralogy. The δ18O and δ13C of the crack-seal veins vary between -11.2 to -7.8 ‰ and -2.9 to 1.9‰, respectively. The estimated clumped-derived paleotemperature of this vein is 95°C, even higher up to 136°C by utilizing the fluid inclusions. On the other hand, the Mn-rich later phase veins, which cross-cut the crack-seal veins, indicate an isotopic composition of -10.9 to -10.6‰ for δ18O and -18.2 to -15‰ for δ13C, with the estimated paleotemperature of 74-84°C. Hence, we argue that the structural diagenesis history in the study area comprises several distinct tectonic events and fluid circulation members along the fractures associated with different stages of basin evolution. Our findings, for the first time, offer a new understanding of paleo fluid circulation and also highlight the multi-proxy’s potential for investigating the structural diagenesis of calcite veins in the Ediacaran host rock in Arabia.

How to cite: Herlambang, A., Koeshidayatullah, A., Lu, C., Amao, A., Bello, A., Al-Ghamdi, F., Malik, M., and Al-Ramadan, K.: Crack-seal veins: records of 600-million-year complex tectonic and fluid flow evolution in Saudi Arabia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15952, https://doi.org/10.5194/egusphere-egu23-15952, 2023.

EGU23-15974 | ECS | Orals | GMPV1.3 | Highlight

LA-ICP-MS U-Pb carbonate geochronology and its geological applications 

Shitou Wu, Nick Roberts, and Zhongwu Lan

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb geochronology for carbonate minerals, calcite in particular, is rapidly gaining popularity as an absolute dating method. In this study, we review the latest technical progress in LA-ICP-MS carbonate geochronology, including the pre-screening strategies (on-line spot selection with a threshold, image-guided approach, and image-based approach), preferred instrumentation (Q-ICP-MS, SF-ICP-MS and MC-ICP-MS), calibration methods, common Pb corrections and the development of reference materials, with the aim of further improving the precision and accuracy of this technique. We emphasized the characterization of two calcite reference materials (TLM and LSJ07) for micro-beam U-Pb geochronology and C, O isotope ratio measurements. The latest geological applications of LA-ICP-MS U-Pb carbonate geochronology in dating of diagenesis and hydrothermal activity were reviewed.

How to cite: Wu, S., Roberts, N., and Lan, Z.: LA-ICP-MS U-Pb carbonate geochronology and its geological applications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15974, https://doi.org/10.5194/egusphere-egu23-15974, 2023.

EGU23-16279 | ECS | Posters on site | GMPV1.3

Interpreting hydrothermal clumped isotope temperatures in the Irish Zn-Pb ore field 

Aileen Doran, Steven Hollis, Julian Menuge, Alina Marca, Paul Dennis, and David van Acken

With the introduction of climate action plans by many countries globally, the development of green technologies like electric vehicles and renewable infrastructure is expected to increase. These technologies are resource intensive, meaning we will require increased production of metals to meet the growing demands of society. However, discovery and exploration rates are not increasing at the same rate as demand. Improving understanding of ore system formation and evolution is a crucial step in aiding future exploration, to help supply these critical resources.

In hydrothermal systems, carbonate minerals (e.g., calcite and dolomite) are often associated with all stages of ore formation, with fluid inclusion thermometry and carbon-oxygen (C-O) isotope ratios traditionally used to study fluid temperature and composition. However, there are several challenges still remaining with these techniques, with fluid inclusions often too small, ruptured or deformed for adequate study. In carbonate minerals, the rare, heavy isotopes 13C and 18O bond or clump more frequently at lower temperatures, with the magnitude of clumping inversely temperature-dependent. Measurement of clumped C-O isotope ratios, using gas source isotope spectrometry, simultaneously yields carbonate δ13C and δ18O values and generates mineral precipitation temperatures, allowing fluid δ18O to be directly calculated. While traditionally applied to low temperate environments, recent applications have included hydrothermal ore systems to study fluid temperature and mixing. When combined with other techniques, such as strontium isotopes, new understanding of the sources, movement and compositional evolution of fluids can be deciphered.

Recent clumped C-O and strontium isotope analyses of ore-related carbonates from the Lisheen and Galmoy deposits, southern Irish Zn-Pb ore field, have facilitated the study of fluid sources, temperatures, mixing, and modification. Lisheen and Galmoy are  hosted in a belt of regionally dolomitized Lower Carboniferous (Mississippian) marine limestones, cut by a series of NE-SW-trending ramp-relay normal faults. Study of these deposits reveals that early dolomitizing and later hydrothermal fluids are part of a complex multistage continuum, with phases of fluid mixing, compositional buffering due to dissolution, and isotope resetting. Consequently, studies of carbonates in other deposits may yield new insights into ore formation, ultimately helping exploration for crucial resources.  

How to cite: Doran, A., Hollis, S., Menuge, J., Marca, A., Dennis, P., and van Acken, D.: Interpreting hydrothermal clumped isotope temperatures in the Irish Zn-Pb ore field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16279, https://doi.org/10.5194/egusphere-egu23-16279, 2023.

EGU23-1225 | Posters on site | GI5.7

Experiments of arsenic (V) adsorption on birnessite: implications on arsenic cycling 

Hao Wei Huang, Huai-Jen Yang, Li-Yun Huang, and Chia-Ju Chieh

Birnessite occurs as a major manganese oxide in sediments. It is characterized by a high adsorption capacity for trace elements, including arsenic. However, the effects of birnessite on arsenic cycling were less intensively investigated than that of goethite, a commonly recognized arsenic host. Therefore, this study utilizes arsenic-bearing solutions containing 0.1–50 ppm arsenic to synthesize birnessite and uses arsenic sequential extraction procedure (SEP) analysis to quantify its arsenic co-precipitation and adsorption capacity.
    SEPs showed that adsorbed/structural arsenic ratio grew from 0:100 to 60:40, with arsenic concentration increasing from 0.1–50 ppm, implying saturation of structural arsenic. SEPs quantify the adsorbed and structural As of birnessite being 0.831 and 1.308 mg/g, respectively. However, the low arsenic concentrations of < 1% in residual solutions indicate nonattainment of the maximum adsorption capacity. Subsequent adsorption experiments using higher initial arsenic concentrations reaching 250 ppm determined the maximum arsenic adsorption capacity to be 19.81 mg/g at pH 7, comparable to the values of 15.3–22.5 mg/g at pH 6.5 (Manning et al., 2002; Singh et al., 2010) and that of 3.79–15.73 mg/g for goethite. It then appears that birnessite adsorption/desorption is more effective than precipitation/dissolution in controlling arsenic cycling. However, the consideration based on the maximum adsorption capacity might overrate the controls of adsorption/desorption relative to precipitation/dissolution because the natural water generally contains less arsenic than that used for the adsorption experiments. Therefore, we conducted adsorption experiments with low arsenic concentrations of 0.5 ppm and a solid/liquid ratio of 0.01 to 0.001. The results showed that adsorption capacity rose abruptly to 1.416 mg/g in two weeks and then slowly increased to 1.523 mg/g after three months. This feature indicated incomplete filling of the adsorption sites on the surface of birnessite at low As concentration despite its large specific surface area. Another controlling factor was the abundance of birnessite in sediments. If 10% of MnO (0.05–0.15%) in the Chianan sediments in southern Taiwan occurred as birnessite, the adsorbed arsenic was calculated to be 0.0005–0.022 mg, corresponding to < 2 % of adsorbed arsenic in 1 g sediments, based on the SEP data of Yang et al. (2016). In the extreme case that all the Mn occurred as birnessite, birnessite could account for up to 25% of the adsorbed arsenic. Apparently, birnessite is not a major contributor to surface arsenic cycling. However, this inference must be evaluated by considering the adsorption and co-precipitation data from goethite and goethite proportions in sediments.

How to cite: Huang, H. W., Yang, H.-J., Huang, L.-Y., and Chieh, C.-J.: Experiments of arsenic (V) adsorption on birnessite: implications on arsenic cycling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1225, https://doi.org/10.5194/egusphere-egu23-1225, 2023.

EGU23-4067 | Orals | GI5.7

Application of ion-exchange resin sachets and XRF-CS in heavy metal pollution sources monitoring 

Yu-Chen Jian, Ludvig Löwemark, and Alice Chien-Yi Liao

For the past decades, scientists have endeavored to develop efficient and suitable approaches to monitor heavy-metal pollution through technological development. Conventional monitoring methods for heavy metals are still complicated, relatively expensive, and time-consuming. This research aims to develop an innovative heavy-metal monitor, the novel approach of ion-exchange resin sachets combined with X-ray fluorescence core scanner (XRF-CS), to achieve an efficient way to effectively monitor vast areas for contamination. The resin sachets, which have a large capacity to quickly take up heavy metals, were deployed in the river weekly to capture heavy metals and then analyzed using the non-destructive, fast, and cost-efficient Itrax XRF core scanner. Two four-week sampling sessions, performed during the dry and wet periods, respectively, were conducted in northeastern Taiwan, where the environment was contaminated by a copper smelter and coal mine activities in the late twentieth century. The results suggest that ion-exchange resins are useful as long-term monitors of heavy metals in a low pollution-level settings (metal concentration <1 mg/L), and that XRF core scanner data truly reflect metal pollution concentrations as measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). This approach allows us to pinpoint pollution sources along the studied river. Especially, Zn, Ni, Mn, Fe, Cu, Ca, and Sr could be detected near pollution sources, where cps values were 1.8 to 3430.6 times higher than in unpolluted areas. Zn shows the largest difference between polluted and non-polluted areas, with the cps values of the samples in polluted areas 3528 times higher than their non-polluted counterparts. Ni, Mn, Fe, Cu, Ca, and Sr’s cps values were 1.8, 29.2, 46.1, 2.4, 6.2, and 5.9 times higher, respectively, than the corresponding counts measured in non-polluted areas. In addition, our results demonstrate that the intensity of precipitation influences the amount of metal adsorption in the resins; resins showed less adsorption in the dry period, and cps values slightly dropped to 81 to 84 percent of the wet period. In summary, ion-exchange resins are a sensitive tool that can be applied in pollution monitoring at various pollution levels due to their high performance in adsorbing heavy metals. Consequently, ion-exchange resin sachets in combination with XRF core scanner analysis is a cost-effective way to monitor large areas of potentially polluted aquatic systems quickly.

How to cite: Jian, Y.-C., Löwemark, L., and Liao, A. C.-Y.: Application of ion-exchange resin sachets and XRF-CS in heavy metal pollution sources monitoring, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4067, https://doi.org/10.5194/egusphere-egu23-4067, 2023.

EGU23-6351 | ECS | Orals | GI5.7

Geochemical baseline values of chalcophile and siderophile elements in soils around the former mining area of Abbadia San Salvatore (Mt. Amiata, Southern Tuscany, Italy). 

Federica Meloni, Barbara Nisi, Caterina Gozzi, Jacopo Cabassi, Giordano Montegrossi, Valentina Rimondi, Daniele Rappuoli, and Orlando Vaselli

Determining the background values of chemical components in environmental matrices is a difficult task. This is particularly true in regions where the human impact due to industrial, mining, agricultural and urban activities coexists with a geological (geogenic) anomaly, which influences the concentration of certain elements in soils, waters and air. In these cases, the term geochemical baseline (GB) is preferable, since it considers the actual content of that element in the superficial environment at a given point in time, including both geogenic and anthropogenic contribution. In this study, a total of 102 top- and sub-soil (collected at 10-50 cm and 50-154 cm depth, respectively) samples and seven rocks, onto which the soils developed, were collected for the determination of GBs for selected chalcophile (As, Cu, Hg and Sb) and siderophile (Co, Cr, Ni, and V) elements in 25.6 km2 around the former mining area of Abbadia San Salvatore (Mt. Amiata, Southern Tuscany, Italy). For about one century, cinnabar (HgS) ore deposits have been exploited to produce liquid mercury from the Mt. Amiata volcanic system and its surroundings, which represents a world-class mercury district. The < 2 mm (as required by the national regulamentation) fraction of the samples was pulverized and analysed by ICP-MS (As, Hg and Sb) and ICP-AES (Co, Cr, Ni, and V) after aqua regia digestion. The compositional data analysis of multivariate compositional vectors, based on the log-ratio approach was used to assess the nature of the geochemical . According to our findings, the centred log-ratio (clr) opposed to that of raw/log transformation, enhances the spatial mapping. This also allowed to obtain better-separated variables in the robust Principal Component Analysis (rPCA). Log-ratio geographical maps evidenced that the underlying bedrock geology (parent lithologies), rather than anthropogenic causes, controls the distribution of the  great majority of the elements in the top- and sub-soils. The resulting clr-PCA approach, associated with the geological features, indicates that the geochemical pattern of Hg-As is to be related to the volcanic rocks and ore-deposits, although an anthropogenic influence due to the past mining activity in the topsoils cannot be ruled out. Sb, Co, Cr, Ni, and V distribution patterns are in most cases attributed to calcareous and clay lithologies. The anomalous content of Sb found within the volcanic rocks was likely due to the presence of previously undetected old mining dump. The two data populations (volcanic and calcareus-clay lithologis) were separated into two different databases and the outliers were removed when necessary. By processing the two datasets, the US-EPA’s ProUCL software was used for calculating the GBs for the selected suite of elements. The obtained values are paramount for establishing specific guidelines and quality standards in environmental legislation and policy-making to be applied by the Municipality of Abbadia San Salvatore

How to cite: Meloni, F., Nisi, B., Gozzi, C., Cabassi, J., Montegrossi, G., Rimondi, V., Rappuoli, D., and Vaselli, O.: Geochemical baseline values of chalcophile and siderophile elements in soils around the former mining area of Abbadia San Salvatore (Mt. Amiata, Southern Tuscany, Italy)., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6351, https://doi.org/10.5194/egusphere-egu23-6351, 2023.

EGU23-7980 | ECS | Posters on site | GI5.7

A transect of mercury concentrations in fish (Black bass, Micropterus salmoides) from the Valdeazogues river, Almadén Hg mining district, South Central Spain. 

José Ignacio Barquero, Pablo Higueras, Jesus J. Hidalgo, Jose M. Esbri, Saturnino Lorenzo, and Efren Garcia-Ordiales

The Almadén district has been the World’s largest producer of mercury (Hg), for more than 2000 years. The mining activity in the district ceased some 10 years ago; however, the generalized pollution of soils and stream sediments, as well as the atmospheric emissions from these and other sources, still represent possibilities to toxify the human food chain. The Valdeazogues river crosses completely the district, with some 150 km2 extension, and including a huge mine, three mines of median importance, and up to 60 points where cinnabar (HgS) has been recognized.

Largemouth bass (Micropterus salmoides) is a carnivorous freshwater gamefish, very common along the Valdeazogues river. For years it was fished to complement the diet of the local inhabitants, although nowadays is not so common to consume it. We obtained 28 specimens, with sizes between 69 and 335 mm and weight between 11 and 552 gr, in a transect from the El Entredicho open pit to downstream the district (some 36,3 km). The specimens were analyzed using atomic absorption spectrometry with Zeeman effect.

Results show important variations throughout the transect; the largest fish in terms of weight and length had the highest Hg concentration (5246 ng/g), much higher than the fish with the lowest concentration (473.2 ng/g), which was not the specimen with the lowest size. Besides, as we go downstream the Valdeazogues River, moving away from the Entredicho Mine (considered to be the main source of contamination), Hg concentrations drops considerably until stabilizing at approximately 1200 - 1500 ng/g.

How to cite: Barquero, J. I., Higueras, P., Hidalgo, J. J., Esbri, J. M., Lorenzo, S., and Garcia-Ordiales, E.: A transect of mercury concentrations in fish (Black bass, Micropterus salmoides) from the Valdeazogues river, Almadén Hg mining district, South Central Spain., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7980, https://doi.org/10.5194/egusphere-egu23-7980, 2023.

EGU23-8217 | ECS | Orals | GI5.7

Assessing the impact of both a forest and a waste fire on the soil chemistry of two areas in Campania region 

Lucia Rita Pacifico, Annalise Guarino, Antonio Pizzolante, and Stefano Albanese

In the last decades, intentional illegal burnings increased in the numbers and became a problem of a global interest. As a consequence, human beings can be exposed to potentially toxic elements (PTEs) released during the combustion, dispersed by the wind, and accumulated in the fire’s ashes (Dimitrios, 2020).

Several studies highlighted that PTEs content in the deposited ashes can modify the chemical and the physical characteristics of the soil and, therefore, it can influence the development and growth of local microorganisms and vegetation (Raison, 1979). The geochemical characteristics of ashes depend on the nature of burned material (Dermibas et al. 2003) and on many other variables such as the intensity of combustion, the composition of the underlying soil, the bedrock type, etc.

The aim of the study was to verify at two different sites the environmental impact related with the on-set of two fire events occurred in Campania region (Southern Italy) during the 2017 summer season. One of the fires involved a forest (on the slopes of Mt. Somma-Vesuvius) and one affected a waste disposal site, known as Ilside (close to the city of Caserta). The variation occurred to concentration of PTEs in topsoil was used for the purpose.

Specifically, at both locations, 30 topsoil samples were collected before and right after the fire events. In total 60 samples were collected at the surroundings of Mt. Somma-Vesuvius slopes and 60 at the surroundings of Ilside. The post-fire samples were collected in correspondence of pre-existing sampling sites along the main wind directions recorded at the time of the fires.

To explore the potential elemental contamination occurred in soils due to the fire events, the Enrichment Factor (EFs) of a selection of PTEs was determined and mapped for individual samples. A predominant enrichment of Hg was identified for both areas.

Further, a combined application of multivariate statistics and geospatial analysis was also performed on the calculated EFs.

For the Ilside site (where special waste and e-waste were involved in burning) the association of Hg, Tl, Cu and Co was identified as the main responsible of data variability; for the Vesuvian area, the association of Hg, Cu and Cr was found to be quite strong and possibly associated with forest biomass burning.

This study highlighted how different can be the chemical evidence left by fires occurring in the environment depending on the nature of the burnt materials. At same time, result showed that even the burning of biomasses proceeding from a natural area can input in the environment PTEs which can potentially generate an increase of the pre-existing degree of environmental hazard.

References

Dermibas, A., 2003. Toxic Air Emissions from Biomass Combustion, Energy Sources, 25:5, 419-427.

Dimitrios E. A., 2020. Suburban areas in flames: Dispersion of potentially toxic elements from burned vegetation and buildings. Estimation of the associated ecological and human health risk. Environmental Research, Volume 183, ISSN 0013-9351.

Raison, R.J., 1979. Modification of the soil environment by vegetation fires, with particular reference to nitrogen transformations: a review. Plant Soil 51, 73–108.

How to cite: Pacifico, L. R., Guarino, A., Pizzolante, A., and Albanese, S.: Assessing the impact of both a forest and a waste fire on the soil chemistry of two areas in Campania region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8217, https://doi.org/10.5194/egusphere-egu23-8217, 2023.

EGU23-8374 | Orals | GI5.7

Geochemical transport through the critical zone: Statistics and reconstruction 

Karl Fabian, Clemens Reimann, and Belinda Flem


Detecting and quantifying geochemical transport through the critical zone at the continental to regional scale requires reliable  statistical procedures that can be uniquely interpreted. We present methods that provide different views on the same data sets and  formulate rules for their application and interpretation. The statistical analysis of cumulative distribution functions (CDFs) uses cumulative probability (CP) plots for spatially representative multi-element and multi-media data sets, preferably containing >1000 sites.
Mathematical models demonstrate how contamination can influence elemental CDFs of different  sample media. For example large-scale diffuse soil contamination leads to a distinctive shift of the low-concentration end of the distribution of the studied element in its top-soil CP plot, whereas high local contamination influences the high-concentration end. But also bio-geochemical processes can generate recognizable changes in elemental CDFs.
A related and partly unsolved problem is the correct interpretation of compositional data in terms of their transport through  the critical zone. 

 

How to cite: Fabian, K., Reimann, C., and Flem, B.: Geochemical transport through the critical zone: Statistics and reconstruction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8374, https://doi.org/10.5194/egusphere-egu23-8374, 2023.

In 2015, an environmental monitoring plan (http://www.campaniatrasparente.it) was launched with the aim of assessing the conditions of all environmental compartments (air, water, top and bottom soils, vegetables, biological samples) of the Campania region. A total of 5,333 topsoil samples were collected and analysed to determine the concentration of 52 chemical elements by means of Aqua Regia followed by ICP-MS. The main aim of prospecting campaign was to establish the ranges of the natural geochemical background for a few potentially toxic elements (PTEs) to be used as reference to define the degree of contamination of anthropized areas.

In the study area (about 13,600 km2) four volcanic areas are present and their pyroclastic products are spread across the regional territory due to a common (Plinian) explosive behaviour.

Due to the natural enrichment in some PTEs of soil developed on pyroclastic products, to discriminate the anthropic signals from the natural ones using geochemical data it is not a simple task when dealing with Campania soils. Therefore, as a preparatory work, to precisely identify regional areas mantled by “volcanic” soils we trained five machine learning algorithms (MLAs) to recognize when soil geochemistry is linked with the presence of volcanic products. All MLAs were implemented on centered log-ratio transformed data to reduce the closure and scaling effect commonly affecting geochemical data. In total, 1277 volcanic soils (VS) and 353 non-volcanic soils (NVS), respectively, were selected for the training phase. Data related with VS were selected based on the proximity of the samples with the volcanic centres, excluding highly anthropized areas. Data related with NVS were selected by consulting available detailed geological maps of those areas located faraway from volcanic areas where pyroclastic covers are completely absent. During the training phase, a cross-validation procedure was applied for parameters optimization. In the test phase all the MLAs showed an accuracy greater than 98% and the Random Forest algorithm proved to be the most accurate for the prediction of the remaining 3903 unlabelled soils. Therefore, a total of 1739 samples were classified as NVS and 2164 as VS. A subsequent comparison of the results with the existing distribution models of volcanic products has shown that samples classified as VS mainly fall in areas characterized by a high thickness of the pyroclastic fall deposits normally related to i) eruptions occurred in the last 10 Ky; ii) Campanian Ignimbrite eruption (ca. 39 ky BP); iii) Codola eruption (ca. 25 ky BP).

The MLAs results suggested that the most important chemical variables for the specific classification purpose were Ni, Cs, Ca, Co, Rb, Sc, Mn, U, Na. It is also evident that a first classification could be made by using few of these elements, as well. Our findings could be used as a valuable tool to better discriminate soil nature and geochemical characteristic aiming at a more effective assessment of natural background ranges for those elements sourced by both natural processes and human activities.

How to cite: Ambrosino, M., Albanese, S., Lucadamo, A., and Cicchella, D.: Combining compositional data analysis and machine learning to recognize where soil geochemistry is influenced by the presence of pyroclastic covers in Campania region (Southern Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8484, https://doi.org/10.5194/egusphere-egu23-8484, 2023.

The contamination of groundwater by geogenic sources is a major problem in many nations, especially those in the developing world. Fluoride (F) is one of the most pervasive and well-documented geogenic contaminants because of the severe health risks it poses due to its toxicity. F contamination in groundwater in India has been the subject of intense research over the past many decades. In this article, we describe the underlying geochemical process liable for F contamination as well as the factors controlling its spatiotemporal distribution in the Sedimentary Alluvial Plain (SAP) of Bankura District, West Bengal, India. To achieve the desired objective, representative groundwater samples were collected from tube wells and hand pumps at different locations of the study region during pre- and post-monsoon seasons. Collected samples were subjected to F and other hydrochemical analysis following standard test methods. Analysis shows that 37% of all groundwater samples collected during the pre-monsoon period have fluoride levels over 1.5 ppm (the limit specified by the World Health Organization, Geneva, 2004); however, the contamination level dropped to 30% during the post-monsoon period. The investigation of groundwater level changes indicates that, as water levels rise during the post-monsoon, F concentrations decrease due to the dilution effect. Piper trilinear diagram suggested Na-Ca-HCO3 type of groundwater for both seasons. According to Gibbs diagrams, rock-water interactions (mineral dissolution) are responsible for major ion chemistry in groundwater samples. Factor analysis (FA) of hydrochemical parameters revealed that the occurrence of F in groundwater was due to the weathering and dissolution of fluoride-containing minerals. X-ray diffraction (XRD) analysis of SAP sediments further confirmed the presence of fluoride-bearing minerals (muscovite and fluorite) in the subsurface lithology of the region. A substantial positive loading (> 0.75) of F with pH and bicarbonate for FA demonstrates that F is being leached from the host material by an alkaline-dominated environment. To account for the spatial variability and seasonality to the spatial change of F concentration in groundwater of the SAP, geographical information systems tools and inverse distance weighting interpolation method were used. The results revealed that significant spatiotemporal variability of F contamination was mainly influenced by the recharging rainwater and the average recharge altitude of groundwater in the area under study. The contamination level is significant in the elevated region where replenishing rainwater is more likely to come into contact with fluoride-bearing minerals when it infiltrates and percolates through the vadose zone. This phenomenon increases the F leaching through chemical weathering along groundwater flow pathways. The findings of this study can serve as a scientific foundation for the efficient management of F-contaminated groundwater in the SAP.

 

How to cite: Ghosh, A., Gogoi, N., Kartha, S. A., and Mondal, S.: Geochemical Evaluation and Spatiotemporal Distribution of Fluoride in Groundwater of the Sedimentary Alluvial Plain of Bankura District, West Bengal, India, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9327, https://doi.org/10.5194/egusphere-egu23-9327, 2023.

Dichlorodiphenyltrichloroethane (DDT) and its metabolites are highly toxic and pose chronic effects to the biosphere. As a natural storage pool, forests have great potential to capture them from the atmosphere and migrate them to the forest soil, which, in turn, influences the safety of the forest ecological environment. In this study, a systematical survey of DDT and its metabolites has been carried out to measure their spatial variations in Chinese forest soils. The main objectives of this study were to (1) investigate the levels, distribution and sources of DDT and its metabolites, and further estimate their mass inventories in Chinese forest soils, (2) explore the impact of soil properties on their distribution, and (III) assess the ecological and health risks of DDT and its metabolites. The research results were as follows. The average concentration of ΣDDTs reached up to 9.75 ng/g, and p,p’-DDT is the main component. Significant difference in the concentration of ΣDDTs was observed between the southeast and northwest regions (p<0.01), which may be related to multiple factors such as pesticide use, rainfall and altitude. The forest soil quality inventory is about 0.58×103 tons, which is lighter than that of domestic farmland soil. 56.1% of soil samples were less than the low value of risk assessment (ERL). The concentration of ΣDDTs in the East and middle is higher than that in the West, and the high value is mainly distributed in the coastal areas. DDTs were mainly from the input of the mixed source composed of industrial DDT and dicofol, of which at least 97% came from industrial DDT and up to 4% from dicofol. ΣDDTs was only positively correlated with precipitation and population density (p<0.05). The degradation of DDT in soil occured from primary stage to high stage. The possible degradation pathways involved in DDTs entering forest soil were preliminarily deduced. Firstly, the surrounding pollution sources volatilize DDTs from soils to the atmosphere through secondary emission. In this process, DDT was continuously transformed into DDE through photodecomposition. The atmosphere rich in DDTs were transported to the forest area and then into the forest surface soil through atmospheric dry and wet deposition. Then, DDT transported continuously accumulated and degraded in forest soil. In the alternation of anaerobic and aerobic process, the main degradation pathways are DDT→DDD→DDMU, DDT→dicofol+DBP, DDT→DDE→DDMU, DDMU→DDNU.

How to cite: Qu, C., Wang, R., and Sun, W.: The occurrence of dichlorodiphenyltrichloroethanes (DDT) and its metabolites in Chinese forest soils: Implications for sources and environmental processes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13317, https://doi.org/10.5194/egusphere-egu23-13317, 2023.

EGU23-15671 | ECS | Posters virtual | GI5.7

Spatio-temporal variations of phosphorus (P) fractions in surface sediments of the southern Caspian Sea 

Pooria Ebrahimi, Mohammad Javad Nematollahi, Hassan Nasrollahzadeh Saravi, Rolf David Vogt, Fariba Vahedi, and Mahdie Baloei

Sediments act as a sink and a secondary source of contaminants, accounting for a central part of coastal and marine biogeochemical cycles. Phosphorus (P) is a macronutrient that governs primary productivity and phytoplankton growth, but excess P influx results in algae bloom and deteriorates aquatic ecosystems. This study assesses seasonal fluctuations, spatial distribution and fractions of P in the sediments of the southern Caspian Sea. In this study, at eight sampling points, composite samples of the surface (from 0 to 10 cm) seabed sediments were collected at 10 and 30 m water depths. The sampling campaigns were carried out in the four seasons and a total of 64 sediment samples were obtained. Total organic matter (TOM), total P (TP) concentration and particle size distribution were determined. Then, P was fractionated using a four-step sequential procedure to quantify the loosely bound P (LP), the reductant soluble P (FeP), the metallic oxide-bound P (AlP) and the calcium carbonate (CaCO3) bound P (CaP). The inorganic P (IP) pool refers to the sum of LP, FeP, AlP and CaP, while the organic P (OP) was calculated by subtracting IP from TP.

The results show that seasonal fluctuations of mean TP were statistically insignificant (p-value > 0.05). Still, the highest levels were recorded in autumn (1555 mg kg-1), followed by winter (1405 mg kg-1), spring (1378 mg kg-1) and summer (1130 mg kg-1). These minor temporal variations in P levels are associated with the seasonal differences in the amount of runoff and the intensity of rivers discharging into the Caspian Sea, and thereby their sediment load and the physicochemical characteristics. The large riverine influx resulted in TP contamination hotspots in the river deltas of Anzali wetland, Babolrood and Sefidrud (northern Iran), where high loadings of suspended particles are discharged into the sea. The spatial TP distribution is thus site-specific and uneven. The main P fraction was CaP, reflecting the phosphate (PO43-) strong affinity for, and association with, calcium-bearing minerals. Only a minor fraction of P was determined as LP. The fraction of the mud-size particles was the main explanatory factor for the spatial distribution of overall low levels of non-residual (or bioavailable) P forms (i.e., LP, FeP and AlP) during spring and summer, while the sand fraction had the greatest explanatory value for the distribution of residual (non-bioavailable) P form (CaP) during autumn and winter. This study demonstrates that P bioavailability in sediments is mostly controlled by the physicochemical characteristics of the sediment material, which again is steered by seawater chemistry. A low content of bioavailable P fractions could therefore be related to the relatively low content of fine-grained (i.e. below 63 µm) particles in sediments of the southern Caspian Sea.

How to cite: Ebrahimi, P., Nematollahi, M. J., Nasrollahzadeh Saravi, H., Vogt, R. D., Vahedi, F., and Baloei, M.: Spatio-temporal variations of phosphorus (P) fractions in surface sediments of the southern Caspian Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15671, https://doi.org/10.5194/egusphere-egu23-15671, 2023.

This study reports on the unique results of the recently concluded Sediment-quality Information, Monitoring and Assessment System to Support Transnational Cooperation for Joint Danube Basin Water Management (SIMONA) project, the largest of its kind in Europe, which was carried out in 2018-2022 as a project of the EU DTP aiming at delivering a ready-to-deploy sediment-quality monitoring system for the effective and comparable measurements and assessment of sediment quality in surface waters in the Danube River Basin in accordance with the EU Water Framework Directive (WFD). The project has developed, tested, demonstrated an innovative environmental geochemical monitoring platform of fluvial (suspended, river bottom and floodplain) sediments using state-of-the-art automated and passive sampling technology for the contamination risk assessment according to the EU WFD in the Danube Basin. Time series analysis and signal processing of one year multi-variate and multi-matrice monitoring data could be used to identify the geochemical background, temporal trends, periodicities and contamination events in the studied EU-defined Hazardous Substances. Since the applied technology, methods and data interpretation is fully consistent with EU legislation risk assessment, results may provide a ‘best solution’ for the spatial and temporal discrimination of contamination. Results of biological contamination assessment of sediments using microbial tests are also presented.

Keywords: data analysis, geochemistry, mobility, speciation, enrichment, time series analysis

How to cite: Kovács, Z., Jordán, G., Szabó, P., and Bálint, M. and the SIMONA Project Team: Development, data modelling of environmental geochemical monitoring of fluvial (suspended, river bottom, floodplain) sediments using unique automated and passive sampling for the contamination risk assessment according to the EU WFD in the Danube Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15997, https://doi.org/10.5194/egusphere-egu23-15997, 2023.

EGU23-16075 | ECS | Orals | GI5.7

Assessing the soil baseline values of a geologically complex territory: the case study of Basilicata region. 

Annalise Guarino, Lucia Rita Pacifico, Antonio Iannone, Andrea Gramazio, and Stefano Albanese

The middle and lower reaches of the Basento river and the whole basin of the Cavone river, in Basilicata region (Italy), underwent to a geochemical prospecting involving soil and stream sediments. Specifically, 190 topsoils were collected within a depth range between 10-15 cm from the ground level and 10 bottom soils were sampled within the depth range between 80-100 cm. 

Samples were analysed at the Life Analytics laboratory (Battipaglia, Italy), by ICP-MS following an aqua regia digestion, to determine the concentrations of 16 potentially toxic inorganic substances (As, Be, Cd, Co, Cr, CrIV, Cu, Hg, Ni, Pb, Sb, Se, Tl, V, Zn, SO4).  

The purpose of the study has been the definition of the upper background limits (UBLs) for the investigation area. An exploratory data analysis (EDA) was conducted on the dataset to outline the main data structural characteristics. Due to the huge number of samples below detection limits (BDL) for Cd, CrIV, Hg, Se, Tl, only As, Be, Co, Cr, Ni, Pb, Cu, V, Zn and SO4 were considered for the UBLs definition. 

The estimate of the above-mentioned values has been conducted following a series of rigorous statistical tests in line with the "Guidelines for the determination of background values for soils and groundwater" released by the Italian National System for Environmental Protection (SNPA).  

In detail, after imputing the few BDL values found in the selected variables by means of K-nearest neighbors (k-NN) algorithm, topsoil and bottom soils data were considered as a whole. Indeed, the dataset was subdivided into 7 subsets according the geopedological units identified based on the local pedological and geological features. 

The BoxCox algorithm was applied to the single subsets to normalize data distribution before any statistical treatment. Outliers were identified by mean of the Dixon’s or Rosner’s Outlier tests depending on the sample size, the observation of boxplots and Q-Q plots and the spatial location of some samples considered as hotspots.  

For each variable and for each subset, two statical indices (i.e.:  95th upper tolerance limit with 95% coverage (95UTL95) and the 95th upper prediction limit (UPL95)) were calculated. The more conservative among them was chosen as representative for the UBLs.

Results showed that the UBLs found are much lower than the guideline values set by the Italian Environmental Law (Legislative Decree 152/2006). Our findings emphasized how the use of guideline values established at a national level is often inadequate to administrate a geologically and pedologically complex territory such as Italy, favoring the chance of running into a wrong identification of local environmental hazards.  

How to cite: Guarino, A., Pacifico, L. R., Iannone, A., Gramazio, A., and Albanese, S.: Assessing the soil baseline values of a geologically complex territory: the case study of Basilicata region., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16075, https://doi.org/10.5194/egusphere-egu23-16075, 2023.

EGU23-16151 | Posters on site | GI5.7

Potentially toxic elements (PTEs) in the soils of a densely populated active volcanic area: the Campi Flegrei case study in Italy. 

Stefano Albanese, Pooria Ebrahimi, Antonio Aruta, Domenico Cicchella, Fabio Matano, Benedetto De Vivo, and Annamaria Lima

The line of research on potentially toxic elements (PTEs) is of growing interest to the scientific community for protecting society against adverse health issues. The Campi Flegrei caldera in southern Italy is an active volcanic area where above two million people live, making it an ideal study area for investigating PTEs of natural and anthropogenic origin through the latest advances in geochemical data analysis. Therefore, a total of 394 topsoil samples (0 to 15 cm) were collected for determining the “pseudo-total” concentrations of elements in the <2 mm fraction using a combination of inductively coupled plasma-atomic emission spectrometry (ICP-AES) and inductively coupled plasma-mass spectrometry (ICP-MS), following aqua regia digestion.

The median values show that concentrations of Zn, Cu, Pb, V and As are greater (>10 mg/kg) than Cr, Co, Ni, Tl, Sb, Se, Cd and Hg. The geochemical maps generated by the Empirical Bayesian Kriging interpolation technique indicate that the higher concentrations of Pb, Zn, Cd, Cr, Hg, Ni and Sb are related to the greater population density (>6500 persons per Km2) in the urban area, but the elevated levels of As, Tl, Co, Cu, Se and V are observed in the other parts. In the context of compositional data analysis, the correlation diagram and robust principal component analysis detected: (1) the Pb–Zn–Hg–Cd–Sb–Cr–Ni association that likely shows anthropogenic activities such as heavy traffic load and fossil fuel combustion in the urban area; (2) the Al–Fe–Mn–Ti–Tl–V–Co–As–U–Th association that mostly represents the contribution of pyroclastic deposits; and (3) the Na–K–B association that probably reveals the weathering degree.

To choose the PTEs with potential health risks for the local inhabitants, the PTE quantities in soil are compared with the corresponding contamination thresholds established by the Italian legislation for residential land use. The Tl, Pb and Zn contents exceed the threshold in more than 15% of the collected samples, but Tl which derives from a natural source (e.g., leucite) is culled before evaluation. Then, children (0-6 years old) are considered for health risk assessment because: (1) Pb has significant adverse health effects in children; and (2) the more frequent hand-to-mouth behavior in children under 6 years old is linked to the higher chance of exposure. The probabilistic health risk modeling for the children <6 years old highlights negligible (hazard quotient below 1) Pb and Zn non-carcinogenic risk and unexpected (cancer risk ≤1E-06) Pb carcinogenic risk for exposure through soil ingestion. However, for the inhalation pathway, the children aged <1 year old have the highest chance (90%) of acceptable (i.e. from 1E-6 to 1E-4) Pb carcinogenic health risk. This should not be overlooked because Naples is under high environmental pressure and previous studies reported increased Pb and Zn quantities in soil between 1974 and 1999. Overall, the results of geostatistical interpolation, compositional data analysis and probabilistic health risk modeling potentially uncover the link between soil geochemistry and human health in densely populated active volcanic areas.

How to cite: Albanese, S., Ebrahimi, P., Aruta, A., Cicchella, D., Matano, F., De Vivo, B., and Lima, A.: Potentially toxic elements (PTEs) in the soils of a densely populated active volcanic area: the Campi Flegrei case study in Italy., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16151, https://doi.org/10.5194/egusphere-egu23-16151, 2023.

EGU23-16341 | ECS | Orals | GI5.7

87Sr/86Sr as an efficient tool to investigate environmental processes in winemaking: a Campania (Italy) case study. 

Piergiorgio Tranfa, Mariano Mercurio, Massimo D'Antonio, Valeria Di Renzo, Carmine Guarino, Rosaria Sciarrillo, Daniela Zuzolo, Francesco Izzo, Alessio Langella, and Piergiulio Cappelletti

In the last few years Sr isotope geochemistry has contributed substantially to environmental and food traceability research. This is achievable because soils, plants and waters all have a peculiar Sr isotopic signature (87Sr/86Sr) inherited from the local geological substratum and affected by geological processes as well as the age and initial rubidium concentration of the rocks. Strontium ions released from the bedrock by weathering processes deriving by the interaction of circulating fluids with rocks, enter the environment and accumulates in water and soils. This reservoir of bioavailable Sr may represent a reliable tracer useful to determine the geographical origin of wines as it is known that strontium is taken first by plant roots, then by grapes, and lastly by wine, with no isotope fractionation when compared to the original 87Sr/86Sr ratio in the soil and rocks. As a result, the study of the Sr isotope ratio in the final product (wine) links directly to its geological origin thus representing a specific geofingerprint for any selected wine. Based on these premises this work aims at confirming the strong link between the product (wine) and its territory, with the final purpose to make it recognizable and distinguishable from similar products and protecting it from possible fraud and adulteration. In this work the 87Sr/86Sr systematics has been used to analyze a total of 39 samples (37 soil samples and 2 wine samples) from Campania (Italy). For a better understanding, both total Sr fraction and bioavailable Sr fraction were analyzed in soil samples (rhizospheric soils, bulk soils and samples collected from different horizons) in order to better investigate the environmental processes involved during the wine production cycle.

How to cite: Tranfa, P., Mercurio, M., D'Antonio, M., Di Renzo, V., Guarino, C., Sciarrillo, R., Zuzolo, D., Izzo, F., Langella, A., and Cappelletti, P.: 87Sr/86Sr as an efficient tool to investigate environmental processes in winemaking: a Campania (Italy) case study., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16341, https://doi.org/10.5194/egusphere-egu23-16341, 2023.

EGU23-515 | ECS | Posters on site | HS1.2.1

Estimating sheet flow velocities using quinine as a fluorescent tracer in low luminosity conditions: laboratory and field experiments 

Soheil Zehsaz, João L. M. P. de Lima, M. Isabel P. de Lima, Jorge M. G. P. Isidoro, and Ricardo Martins

This study presents a technique based on the use of quinine as a fluorescent tracer, to estimate sheet flow velocities over various surface coverings (e.g., bare; mulched; vegetated; paved) in low luminosity conditions (e.g., night; twilight; shielded environments). Quinine glows when exposed to UVA light and in the concentrations used is not harmful to the environment. Experimental work was conducted for studying sheet flows in the i) laboratory (using a soil flume), over bare and mulched surfaces, and ii) field, over vegetated and paved surfaces. Flow velocities were estimated based on the injection of a quinine solution into the water flow.  In these experiments, dye and thermal tracer techniques were used as a benchmark for assessing the performance of the quinine tracer. Optical and infrared cameras were used to record the movement of the tracers’ plumes in the flow. The surface velocity of the flow was estimated by tracking the tracers’ plumes leading-edge and calculating their travel distance over a certain time lapse. Overall, the visibility of the quinine tracer was better in comparison to the dye tracer. However, under some circumstances, lower than the visibility of the thermal tracer. Nonetheless, the results show that all three tracers yielded similar estimations of the flow velocities. Therefore, when exposed to UVA light the quinine tracer can be useful to estimate sheet flow velocities over a wide variety of soil and urban surfaces in low luminosity conditions. Despite some inherent limitations of this technique (e.g., invisible under bright light conditions or heavy mulched/vegetated cover; need of a UVA lamp), its main advantage is the high visibility of the quinine fluorescent tracer under UVA light for fade light conditions (e.g., night; twilight; shielded environments such as close conduits), which creates new opportunities for tracer-based surface flow velocity measurements in surface hydrology studies.

How to cite: Zehsaz, S., de Lima, J. L. M. P., de Lima, M. I. P., Isidoro, J. M. G. P., and Martins, R.: Estimating sheet flow velocities using quinine as a fluorescent tracer in low luminosity conditions: laboratory and field experiments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-515, https://doi.org/10.5194/egusphere-egu23-515, 2023.

EGU23-649 | ECS | Posters on site | HS1.2.1

Near Real-Time Depth Change Monitoring on Inland Water Bodies Using Sentinel-1 and Dynamic World Data 

Utku Berkalp Ünalan, Onur Yüzügüllü, and Ayşegül Aksoy

Monitoring the depth changes in lakes is crucial to understanding hydrological dynamics and water quality changes. In developed countries, the authorities monitor the lake depths regularly; however, it might be different in developing and underdeveloped countries. In this study, we aim to develop a near-real-time SAR-based depth change monitoring system for lakes by focusing on shoreline pixels. For this purpose, we developed a framework using the Sentinel-1 GRD and Sentinel-2 Dynamic World land cover datasets available on the Google Earth Engine. Sentinel-1 data provides us with the necessary temporal resolution for frequent monitoring. For the initial development phase, we consider five ground monitoring stations in Sweden and one in Turkey. The approach starts by detecting water bodies within a selected area of interest using Sentinel-1. Then it extracts shoreline pixels to calculate the change in the VV and VH sigma naught and VV-VH and VV+VH Pauli vectors. Extracted differences are further classified according to the temporally closest Dynamic World data to handle the temporal difference for each land cover type. Next, we eliminate outlier values based on the percentiles, and from the remaining data, we sample each landcover class for modeling. From many of the tested frameworks, we obtained an R2 of 0.79 with Gaussian Process Regression. Currently, in this framework, we observed an underestimation of higher values and an overestimation of lower values within a range of ±0.4 cm. Furthermore, considering the chosen six lakes, we observed a negative correlation between depth change and polarimetric features obtained from samples taken from land covers of grass and flooded vegetation, which is typical for natural lakes. In the second step of the development, we will increase the number of samples by including lakes from Switzerland and further develop the model.

How to cite: Ünalan, U. B., Yüzügüllü, O., and Aksoy, A.: Near Real-Time Depth Change Monitoring on Inland Water Bodies Using Sentinel-1 and Dynamic World Data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-649, https://doi.org/10.5194/egusphere-egu23-649, 2023.

Monitoring dissolved methane in aquatic ecosystems contributes significantly to advancing our understanding of the carbon cycle in these habitats and capturing their impact on methane emissions. Low-cost metal oxide semiconductors (MOS) gas sensors are becoming an increasingly attractive tool to perform such measurements, especially at the air-water interface. However, the performance of MOS sensors in aquatic environmental sciences has come under scrutiny because of their cross-sensitivity to temperature, moisture, and sulfide interference. In this study, we evaluated the performance and limitations of a MOS methane sensor when measuring dissolved methane in waters. A MOS sensor was encapsulated in a hydrophobic ePTFE membrane to impede contact with water but allow gas perfusion. Therefore, the membrane enabled us to submerge the sensor in water and overcome cross-sensitivity to humidity. A simple portable, low-energy, flow-through cell system was assembled that included an encapsulated MOS sensor and a temperature sensor. Waters (with or without methane) were injected into the flow cell at a constant rate by a peristaltic pump. The signals from the two sensors were recorded continuously with a cost-efficient Arduino UNO microcontroller.. Our experiments revealed that the lower limit of the sensor was in the range of 0.1-0.2 uM and that it provided a stable response at water temperatures in the range of 18.5-28oC. More information at Butturini, A., & Fonollosa, J. (2022). Use of metal oxide semiconductor sensors to measure methane in aquatic ecosystems in the presence of cross‐interfering compounds. Limnology and Oceanography: Methods20(11), 710-720.

How to cite: Butturini, A. and Fonollosa, J.: Metal oxide semiconductor (MOS) sensors to measure methane in aquatic ecosystems. An eficient DIY low  cost application., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1221, https://doi.org/10.5194/egusphere-egu23-1221, 2023.

EGU23-1636 | Posters virtual | HS1.2.1

Using the hydrological model for filling the missing discharge data by using multi-site calibration 

Ankit Singh, Hemant Kumar Dhaka, Pragati Prajapati, and Sanjeev Kumar Jha

The river discharge data is one of the most important pieces of information to regulate various water resources, including flood frequency analysis, drought and flood prediction, etc. The missing observer discharge data, even a short gap, influences the whole analysis and gives a totally different result. Filling data gaps in streamflow data is thus a critical step in any hydrological study. Interpolation, regression-based analysis, artificial neural networks, and modeling are all methods for generating missing data. While using the hydrological model to generate the data, we first need to calibrate the hydrological model. The single-site calibration of the hydrological model has its own limitations, due to which it does not correctly predict the streamflow at intermediate gauge locations. This is because, while calibrating the model for the final outlet, we tune the parameters that affect the results for the final outlet only and neglect the intermediate sites' output. In this study, we demonstrate the importance of multi-site calibration and use the calibrated hydrological model to generate the missing data at intermediate sites.

For this study, we selected the Godavari River basin and calibrated it at the final outlet (single-site calibration) and at 18 + 1 outlets (multi-site calibration). The whole basin is divided into 103 subbasins, and the Soil and Water Assessment Tool (SWAT) hydrological model is used for this study. After the successful multi-site calibration, we generated the missing data at 25 different gauging locations. The initial results from single-site calibration (NSE (0.57) and R2 (0.61)) show good agreement between observed and simulated discharge for the final outlet. The multi-site calibration analysis is in progress, and full results will be presented at the conference.

How to cite: Singh, A., Dhaka, H. K., Prajapati, P., and Jha, S. K.: Using the hydrological model for filling the missing discharge data by using multi-site calibration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1636, https://doi.org/10.5194/egusphere-egu23-1636, 2023.

EGU23-2681 | Posters on site | HS1.2.1

A low cost real-time kinematic dGPS system for measuring glacier movement 

Kirk Martinez, Jane Hart, Sherif Attia, Graeme Bragg, Marcus Corbin, Michael Jones, Christian Kuhlmann, Elliot Weaver, Richard Wells, Ioannis Christou, and Emily James

Glacier movement has been measured over the years using commercial units such as those from Leica. The aim is to measure point movements on the glacier surface in order to capture fine-grained data about its movement. This can also help to calibrate satellite-based approaches which have much lower resolution. Commercial dGPS recorders cost thousands of Euros so our project is creating a solution using new lower cost dGPS boards which could enable their use by more earth scientists.

The u-blox Zed-F9P based boards from Sparkfun can be used as a base station to send dGPS corrections to “rover” units on the glacier via a radio link. Each measurement is accurate to about 2cm depending on conditions. In our design the radio is used by the rovers to forward good fixes back to the base station, which then uses off-site communications to send the data home. Two types of internet link have been enabled: using a nano-satellite board (by SWARM) and a more traditional GSM mobile phone board (for locations with coverage). Both these boards are also available from Sparkfun – making most of the modules off-the-shelf. However our power supply is optimised to save power and charge the lithium ion battery from a solar panel. A real-time clock chip is used to wake up the system to take readings and transmit data, so the sleep power is only 0.03 mW enabling a year-long lifetime. The whole system is controlled by a Sparkfun Thing Plus SAMD51 which provides the required four serial connections and a circuitpython  environment. The full system will be installed in Iceland in the summer of 2023 and replace the previous prototype based on Swift Piksi Multi units which had shown the measurement principle to be sound.

How to cite: Martinez, K., Hart, J., Attia, S., Bragg, G., Corbin, M., Jones, M., Kuhlmann, C., Weaver, E., Wells, R., Christou, I., and James, E.: A low cost real-time kinematic dGPS system for measuring glacier movement, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2681, https://doi.org/10.5194/egusphere-egu23-2681, 2023.

EGU23-4844 | Posters on site | HS1.2.1

Quality control of stream water-stage using Hilbert-Huang Transform 

Yen- Chang Chen and Wu-Hsien Hsiao

Hydrological data, especially water stage and discharge, is very important for water resources planning and development, hydraulic structure design, and water resources management. Thus the hydrological data has to be observed and collected regularly and continuously. The hydrological data can be affected by many factors such as people, instruments, and climate. Therefore, the collected hydrological data still need to be subject to quality control and inspection to eliminate unreasonable data to ensure the accuracy and reliability. Traditionally, the quality control and inspection of stream water-stage is mainly manual. The verification of water stage data needs experienced hydrologists to judge the correctness of the data, and cannot be processed automatically. It is time consumed, costly, and labor intensive to process the quality control of stream water stage. Therefore, it is necessary to develop a feasible model to automatically check stream water-stage for providing reliable and accurate hydrological data.

This study applies Hilbert-Huang Transform (HHT) to process stream water-stage. The HHT is composed of Empirical Mode Decomposition (EEMD) and Hilbert transform (HT). The EEMD decomposes stream water-stage into many intrinsic mode functions (IMFs) and a residual. The first IMF component is used for Hilbert transform conversion to obtain the time amplitude energy relationship diagram. The amplitude fluctuation of the corresponding component of the stream water-stage, the amplitude value of the outliers can be revealed. When the amplitude value is larger than usual, there may be outliers, and vice versa. It depends on the threshold that is established in this study as the basis for filtering the incorrect water-stage. Therefore automatically inspecting the water-stage data can be achieved. The model for automatic inspecting procedure developed by this study will greatly reduce the manual quality control, not only shorten the checking time, save manpower, but also provide reliable and correct river water stage data.

How to cite: Chen, Y.-C. and Hsiao, W.-H.: Quality control of stream water-stage using Hilbert-Huang Transform, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4844, https://doi.org/10.5194/egusphere-egu23-4844, 2023.

EGU23-4878 | Posters on site | HS1.2.1

Trials and design iterations experienced developing a low-cost depth trawl to sample macroplastic through the water column of a tidal river. 

David Higgins, Renata Correia, Hooi Siang Kang, Lee Kee Quen, Tan Lit Ken, Andre Vollering, Stijn Pinson, Thaine H. Assumpção, and Thomas Mani

Understanding the transport behaviour of mismanaged plastic waste in riverine and estuarine environments is growing. However, many studies to date focus on the surface layer transport while a limited number look to measure the vertical distribution of plastic waste within these systems. Factors such as density, shape, the influence of wind and flow velocity can determine the vertical distribution of the plastic waste in a river, but many knowledge gaps remain. With this, and as technology developers move to create innovative river surface focused interception solutions to extract plastic waste, a greater understanding of the transport behaviour of sub-surface plastic debris is required. Here, we present a comprehensive overview of the development stages required to build and deploy a low-cost depth trawl tool designed to sample plastic waste at a depth of up to 5m in a heavily polluted river in Malaysia. Topics covered include tool design concepts, manufacturing methods, onsite testing, river deployment learnings and sampling results. Field data is compiled from over 60 sampling surveys conducted over 14 days in several locations along the Klang River, Malaysia. The depth trawl is mounted to a locally available fishing boat (sampan) and consists of two steel horizontal arms, a steel frame, two winches, cables, weights, five nets, and is operated manually with the assistance of a solar-powered motor. The dimensions of each net are 30cm (W) x 50cm (H) x 100cm (L) with a mesh size of 30mm x 30mm. To ensure that the nets remain aligned vertically during deployment, a weight of 15kg is tied to the bottom of the net system on both sides. Samples were collected every 1 metre to a depth of 5 metres. Each sampling was conducted for 15 minutes, six times per day with an interval of 1 hour between samples to allow for changes in the tide and river flow direction. An ADCP was deployed in parallel to the depth trawl to provide measurements of flow velocity variation at the river surface and with depth. In addition, this paper reviews the depth trawl system’s capabilities and recommendations for further studies and applications in the field.

How to cite: Higgins, D., Correia, R., Kang, H. S., Quen, L. K., Ken, T. L., Vollering, A., Pinson, S., H. Assumpção, T., and Mani, T.: Trials and design iterations experienced developing a low-cost depth trawl to sample macroplastic through the water column of a tidal river., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4878, https://doi.org/10.5194/egusphere-egu23-4878, 2023.

EGU23-5922 | Posters on site | HS1.2.1

Effectiveness-assessment of nature-based flood mitigation using networked, low cost DIY environmental monitoring from FreeStation 

Sophia Burke, Arnout van Soesbergen, and Mark Mulligan

FreeStations are mature low-cost, networked, DIY environmental sensors and data loggers, developed since 2014  and now deployed around the world.  Build instructions are open source at www.freestation.org and based on high availability, low cost but accurate and robust components (with builds typically 3% the parts-cost of an equivalent proprietary monitoring systems).  This allows investment in a network of environmental loggers at the cost of a single, proprietary logger.  

FreeStations have been widely deployed in the DEFRA Natural Flood Management (NFM) national trials in the UK, and analytical methods developed to examine the performance of leaky dams, retention ponds, regenerative agricultural practices and other nature based solutions in mitigating flood risk at downstream assets.

These deployments usually consist of FreeStation weather stations: recording rainfall volume, rainfall intensity, air temperature, humidity and pressure as well as solar radiation, wind speed and direction.  The rainfall volume and instantaneous intensity are the most important for NFM studies.  Alongside weather stations, FreeStation sonar-based stage sensors are used, alongside river profile scan from a FreeStation LIDAR, to monitor change in river discharge due to an NFM intervention, relative to discharge at a downstream asset at risk.  Readings are taken at 10-minute intervals over multiple years.

A series of web based methods have been built as part of the FreeStation //Smart: platform to monitor and manage data from deployments and to analyse data to better understand flood mitigation by the key types of intervention.  In testing at more than 10 sites in the UK over a period of 2-3 years per site, large volumes of data have been collected at low cost and in support of local stakeholders during the H2020NAIAD and H2020ReSET projects.  

The data indicate the importance of careful design in leaky debris dams, the limited impact of inline retention ponds and the significant capacity of low-till farming methods to mitigate downstream flooding.  The effectiveness of NFM depends upon the number and scale of interventions, the proportion of the discharge at the downstream asset at risk which they affect (i.e. the downstream proximity of the asset at risk) and the capital and maintenance costs of the interventions. 

Low-cost approaches to environmental monitoring will be critical for developing the evidence base needed to better understand what nature based solutions work, where for water.  Low cost, internet-connected devices are easy to monitor and maintain, low risk and capable of extensive deployment to address the challenge of geographical variability which means that the impacts of specific NFM interventions are highly site specific. 

How to cite: Burke, S., van Soesbergen, A., and Mulligan, M.: Effectiveness-assessment of nature-based flood mitigation using networked, low cost DIY environmental monitoring from FreeStation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5922, https://doi.org/10.5194/egusphere-egu23-5922, 2023.

EGU23-8165 | Posters on site | HS1.2.1

Developing a smart sensor network for soil moisture monitoring in forests 

Nikita Aigner, Christine Moos, and Estelle Noyer

Forests play a crucial role in regulating the water content of soils and thus influence runoff formation, but also the susceptibility to drought or forest fires. However, the extent to which forests influence soil moisture is difficult to quantify and depends on several parameters, such as precipitation intensity and duration, and terrain or soil properties. To capture the temporal and spatial variability of soil moisture in forests, large-scale and long-term measurements are necessary. Currently, such measurements are relatively expensive and complex and thus generally lacking or restricted to agricultural areas.  

Our current work focuses on the development of a low-cost soil moisture sensor that uses off the shelf parts and can be deployed at scale to provide continuous long-term measurements. To increase adoption and ensure the digital sustainability of our concept, the project will be released open source to the general public.  

The sensor design is based around an ESP32 microcontroller to manage measurements with capacitive soil moisture sensors. For communication, we leverage the LoRa protocol and use infrastructure provided by the Things Network (TTN). Herein, we present the soft- and hardware architecture of a sensor prototype and results obtained from a proof-of-concept deployment. In addition, we discuss the calibration procedure and evaluation of capacitive soil moisture sensors (in comparison to time-domain reflectometry (TDR) sensors). Finally, we provide an outlook on future developments of our measurement system. The final goal of this project is to deploy sensors in several areas of interest that will allow for gathering data for a better understanding of the interaction of forests and soil moisture content.  

How to cite: Aigner, N., Moos, C., and Noyer, E.: Developing a smart sensor network for soil moisture monitoring in forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8165, https://doi.org/10.5194/egusphere-egu23-8165, 2023.

EGU23-10497 | ECS | Posters virtual | HS1.2.1

Synchronized mapping of water quantity and quality of a reservoir through an unmanned surface vehicle: A case study of the Daljeon reservoir, South Korea 

Kwang-Hun Lee, Shahid Ali, Yena Kim, Ki-Taek Lee, Sae Yun Kwon, and Jonghun Kam

This study developed a synchronized mapping technique for water quantity and quality via an unmanned surface vehicle (USV). The USV with the acoustic doppler current profiler (ADCP) and the multiparameter sonde of water quality sensors (YSI EXO2) was used for identifying spatial and seasonal patterns of the Daljeon reservoir in South Korea. With this technique, we measured bathymetry and nitrate concentration from August 2021 through July 2022 at the high resolution spatial resolution and tested the sensitivity of estimated nitrate loads to spatial variations of input variables (water volumes and nitrate concentrations). Results showed that measured bathymetry and nitrate concentration varies over the water surface of the reservoir and time, which are associated with seasonal variations of temperature and precipitation. Despite weak spatial variations of the nitrate concentration, the water level of the reservoirs showed strong spatiotemporal variations depending on the topography of the reservoir and the  rainfall occurrence. Furthermore, we figured out using the mean for nitrate load was underestimated by -20% of the nitrate load estimates by considering spatial variation. High-resolution bathymetry measurement play a role in estimating nitrate loads with a minor impact of spatial variations of measured nitrate concentrations. We found that rainfall occurrences more likely increase estimated nitrate loads when it accounts for spatially variations of input variables, particularly water volumes. This study proved the potential utility of USV in simultaneously monitoring water quantity and quality for integrative water resource management for sustainably development of our communities.

How to cite: Lee, K.-H., Ali, S., Kim, Y., Lee, K.-T., Kwon, S. Y., and Kam, J.: Synchronized mapping of water quantity and quality of a reservoir through an unmanned surface vehicle: A case study of the Daljeon reservoir, South Korea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10497, https://doi.org/10.5194/egusphere-egu23-10497, 2023.

EGU23-11411 | Posters on site | HS1.2.1

Automated ablation stakes to constrain temperature-index melt models 

Andrew D. Wickert, Katherine R. Barnhart, William H. Armstrong, Matías Romero, Bobby Schulz, Gene-Hua Crystal Ng, Chad T. Sandell, Jeff D. La Frenierre, Shanti B. Penprase, Maximillian Van Wyk de Vries, and Kelly R. MacGregor

We developed automated ablation stakes to measure colocated in-situ changes in ice-surface elevation and climatological drivers of ablation. The designs implement open-source hardware, including the Margay data logger, which records information from a MaxBotix ultrasonic rangefinder as well as a sensor to detect atmospheric temperature and relative humidity. The stakes and sensor mounts are assembled using commonly available building materials, including electrical conduit and plastic pipe. The frequent (typically 1–15 minute) measurement intervals permit an integral approach to estimating temperature-index melt factors for ablation. Regressions of ablation vs. climatological drivers improve when relative humidity is included alongside temperature. We present all materials required to construct an automated ablation stake, alongside examples of their deployment and use in Alaska (USA), Ecuador, Patagonia (Argentina), and the Antarctic archipelago.

 

a: Alaska, 2012
b: Alaska, 2013
c: Ecuador, 2016
d: Argentina, 2020
e: Antarctica, 2021

How to cite: Wickert, A. D., Barnhart, K. R., Armstrong, W. H., Romero, M., Schulz, B., Ng, G.-H. C., Sandell, C. T., La Frenierre, J. D., Penprase, S. B., Van Wyk de Vries, M., and MacGregor, K. R.: Automated ablation stakes to constrain temperature-index melt models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11411, https://doi.org/10.5194/egusphere-egu23-11411, 2023.

EGU23-11777 | Posters on site | HS1.2.1

A low cost multi-chamber system (“Greenhouse Coffins”) to monitor CO2 and ET fluxes under semi-controlled conditions: Design and first results 

Mathias Hoffmann, Wael Al Hamwi, Matthias Lück, Marten Schmidt, and Maren Dubbert

Determining greenhouse gas (GHG) fluxes, water (ET) fluxes and their interconnectivity within the soil-plant-atmosphere-intersphere is crucial, not only when aiming to find solutions for current agricultural systems to mitigate the global climate crises but also to adapt them to related challenges ahead, such as more frequent and severe droughts. In a first attempt for a better understanding, often laboratory and/or greenhouse pot experiments are performed, during which gas exchange is predominately measured using especially manual closed chamber systems. Commercially available systems to determine gas exchange in terms of CO2 and ET are, however, costly and measurements itself labour-intensive. This limits the amounts of variables to be studied as well as possible repetitions during a study. Additionally, it resulted in the long-term focus on agroecosystems of the northern hemisphere while agroecosystems of sub-Saharan Africa as well as Southeast Asia are still being underrepresented.

We present an inexpensive (<1.000 Euro), Arduino based, multi-chamber system to semi-automatically measure 1) CO2 and 2.) ET fluxes. The systems consists of multiple, self-sufficient, closet-shaped PVC “coffins”. The “coffins” a closed by a frontal door and periodically ventilated through a sliding window. Relays connected to the microcontroller are used to steer closure/opening (linear actuator) and ventilation (axial fans). CO2 and ET fluxes are determined through the respective concentration increase during closure by a low-cost NDIR CO­2 (K30FR; 0-10,000 ppm, ± 30 ppm accuracy) and rH sensor (SHT-41). Parallel measurements of relevant environmental parameters inside and outside the “coffins” are conducted by DS18B20 (temperature) and BMP280 (air pressure) sensors. Sensor control, data visualization and storage, as well as steering closure/opening and ventilation is implemented in terms of a wifi and bluetooth enabled, socket powered (9V), compact microcontroller (D1 RS32) based logger unit. Here, we present the design, and first results of the developed, low-cost multi-chamber system. Results were validated against results of customized CO2 and ET measurement systems using regular scientific sensors (LI-COR 850) and data logger components (CR1000), connected to each “coffin” by a multiplexer.  Flow-meter were used for measurement synchronization.

How to cite: Hoffmann, M., Al Hamwi, W., Lück, M., Schmidt, M., and Dubbert, M.: A low cost multi-chamber system (“Greenhouse Coffins”) to monitor CO2 and ET fluxes under semi-controlled conditions: Design and first results, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11777, https://doi.org/10.5194/egusphere-egu23-11777, 2023.

EGU23-12622 | ECS | Posters on site | HS1.2.1

Water user Fab Labs: co-design of low-tech sensors for irrigated systems 

Paul Vandôme, Crystele Leauthaud, Simon Moinard, Insaf Mekki, Abdelaziz Zairi, and Gilles Belaud

Mediterranean agriculture is facing the challenge to produce sustainably with a water resource under pressure. As irrigated areas expand in response to increasing vulnerability to drought, it is essential to support water users towards better agricultural water management. We set up two Fab Labs on the shores of the Mediterranean (France and Tunisia) to bring together water users around a collective project: co-constructing innovations to address local water management issues. A range of low-tech, low-cost and open source IoT-based sensors emerged from this process. The technologies were tested with users during the 2022 irrigation season. The aim of this study is to provide feedback on this participatory method as a facilitator for creating and sharing innovation in rural territories and to discuss the opportunities, benefits and limitations related to the use of these new technologies. We believe that this work contributes to make the measurement of water flows - and thus their understanding and better management - more accessible to the agricultural sector.     

How to cite: Vandôme, P., Leauthaud, C., Moinard, S., Mekki, I., Zairi, A., and Belaud, G.: Water user Fab Labs: co-design of low-tech sensors for irrigated systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12622, https://doi.org/10.5194/egusphere-egu23-12622, 2023.

EGU23-13072 | ECS | Posters on site | HS1.2.1

Precipitation Measurement from Raindrops’ Sound and Touch Signals 

Seunghyun Hwang, Jinwook Lee, Jeemi Sung, Hyochan Kim, Beomseo Kim, and Changhyun Jun

This study proposes a novel method for rainfall intensity estimation from acoustic and vibration data with low-cost sensors. At first, a precipitation measurement device was developed to collect sound and touch signals from raindrops, composed of Raspberry Pi, a condenser microphone, and an accelerometer with 6 degrees of freedom. To figure out whether rainfall occurred or not, a binary classification model with the XGBoost algorithm was considered to analyze long-term time series of vibration data. Then, high-resolution acoustic data was used to investigate the main characteristics of rainfall patterns at a frequency domain for the period when it was determined that rainfall occurred. As a result of the Short Time Fourier Transform (STFT), the highest frequency, mean and standard deviation of amplitudes were selected as representative values for minute data. Finally, different types of regression models were applied to develop the method for rainfall intensity estimation from comparative analysis with other precipitation measurement devices (e.g., PARSIVEL, etc.). It should be noted that the new device with the proposed method functions reliably under extreme environmental conditions when the estimated rainfall intensity was compared with measured data from ground-based precipitation devices. It shows that low-cost sensors with sound and touch signals from raindrops can be effectively used for rainfall intensity estimation with easy installation and maintenance, indicating a strong possibility of being considered in a wide range of areas for precipitation measurement with high resolution and accuracy

Acknowledgement

This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. NRF-2022R1A4A3032838).

How to cite: Hwang, S., Lee, J., Sung, J., Kim, H., Kim, B., and Jun, C.: Precipitation Measurement from Raindrops’ Sound and Touch Signals, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13072, https://doi.org/10.5194/egusphere-egu23-13072, 2023.

EGU23-14370 | Posters on site | HS1.2.1

Monitoring an ephemeral stream with a Teensy 3.2 + audio shield to determine water level only from the noise of a stream 

Linus Fässler, Natalie Ceperley, Peter Leiser, and Bettina Schaefli

River networks in the Alps are very complex and hold many unanswered research questions. For example, various assumptions must be made to when studying tributaries and small rivers. Namely, there is not a widely accepted tool to measure streamflow in small, mountain streams that can overcome their specific challenges affordably without large installations. For example, alteration between extremely high and no discharge volume is characteristic of intermittent rivers and ephemeral streams (IRES). Conventional measuring devices all require streambed installation, which exposes them to displacement or destruction by abruptly rising water levels. One solution, thus, is to remove the sensor from the streambed and measure from a distance. We have experimented with an acoustic sound recorder mounted above the stream as an alternative tool to assess water level. We designed a low-cost audio sensor powered by a microcontroller with an audio shield specifically for recording IRES. To ensure reproducibility, we used Arduino for programming the Teensy 3.2. Images of the water level in an IRES were simultaneously captured when possible (daylight) and used for calibration. The water level visible in the images correlated well with that determined from the audio recordings from our self-developed audio sensor (R2 = 95%). Based exclusively on the audio recording of an IRES, we can obtain a time series of the water level, at least when water was present. We are currently unable to determine consistently whether water is present nor state with certainty when the streambed is dry based solely on acoustic data. Nevertheless, this new sensor allows us to measure an alpine channel network at more locations and over longer time periods than previously feasible.

How to cite: Fässler, L., Ceperley, N., Leiser, P., and Schaefli, B.: Monitoring an ephemeral stream with a Teensy 3.2 + audio shield to determine water level only from the noise of a stream, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14370, https://doi.org/10.5194/egusphere-egu23-14370, 2023.

The development of artificial reservoirs plays a considerable role in regulating the spatial and temporal distribution of irrigated rainfall and guaranteeing sustainable agricultural development. Many studies have used the area-storage relationship to obtain the storage capacity of on-farm reservoirs (OFRs), but it does not work for OFRs with persistent water surface area. In this study, we proposed an effective method to estimate the water storage of irrigated OFRs by combining multi-source remote sensing data and ground observation. We quickly derived the location of irrigated OFRs by using seasonal characteristics of irrigated OFRs and obtained high-precision water surface area using an object-oriented segmentation. We estimated water storage of irrigated OFRs by combining three different ways (i.e., Lidar-based, ground observation-based (photos), and surface area-based). The method performs well in three aspects, i.e., identifying on-farm reservoirs, extracting water surface area, and calculating water storage. The accuracy of identification reaches 94.1%, and the derived water area agrees well with the surveyed results, i.e., an overall accuracy of 97.8%, the root mean square error (RMSE) and the mean absolute errors (MAE) are 962 m2 and 766 m2, respectively. The obtained water storage is reliable using three different ways (i.e., the area-storage, Lidar-based, and photo observations-based methods), with accuracy of 98.8%, 95.2%, and 94.1%, respectively. The proposed method enables monitoring of the storage of multiple types of irrigated OFRs, particularly the photo observation-based method can deal with the storage of OFRs with persistent water areas, showing huge potential to promote irrigated water resource utilization efficiency.

How to cite: wang, Y.: Monitoring water storage of on-farm reservoirs using remote sensing and ground observation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15372, https://doi.org/10.5194/egusphere-egu23-15372, 2023.

Hydrology is still one of the most data scarce natural sciences. The large number of variables to measure, their extreme spatiotemporal gradients, and the often harsh and hostile environmental conditions all contribute to this issue. This challenge is even more pronounced in remote and extreme environments such as the tropics, and mountain regions, where the need for robust data is most acute.

Many new and emergent technologies can help with building more cost-effective, robust, and versatile hydrological monitoring systems. However, the speed at which these new technologies are being incorporated in commercially available systems is slow and dictated by commercial interests and bottlenecks.

An alternative solution is for scientists to build their own systems using off the shelf components. Open-source hardware and software, such as the Arduino and Raspberry Pi ecosystems, make this increasingly feasible. As a result, a plethora of global initiatives for open-source sensing and logging solutions have emerged.

But despite these new technologies, it remains a major challenge to build open-source solutions that equal the reliability and robustness of the high-end commercial systems that are available on the market. Sharing experiences, best practices, and evidence on the real-world performance of different designs may help with overcoming this bottleneck.

In this contribution, I summarize the experience gained from developing and operating over 300 open-source data loggers, built around the Riverlabs platform. This platform is mostly a compilation of existing open-source hardware and software components and solutions, which were refined further and tweaked for robustness and reliability in extreme environments. Our loggers have been installed in locations as diverse as Arctic Norway, the high Andes of Peru and Chile, the Nepalese and Indian Himalayas, the Somali desert, and the Malaysian rainforest, providing a wide range of real-world test-cases and performances.

How to cite: Buytaert, W.: Towards a robust, open-source logging platform for environmental monitoring in challenging environments: the Riverlabs toolbox, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15989, https://doi.org/10.5194/egusphere-egu23-15989, 2023.

EGU23-17527 | ECS | Posters on site | HS1.2.1

Design of an affordable and highly flexible IoT station for multiple gas concentration monitoring 

Francesco Renzi, Flavio Cammillozzi, Giancarlo Cecchini, Alessandro Filippi, and Riccardo Valentini

The air quality monitoring is a core topic for European environmental policies and worldwide. At the same time technologies such as electrochemical or NDIR gas sensors became affordable and easy to implement in a customized design. A highly flexible monitoring station has been designed and build in order to obtain a customizable and affordable device. It is composed of two boards, one in charge of connectivity and processing while the other allows to insert up to 11 gas sensors. Such number is achieved through the use of three multiplexers that allow to spare input pins of the processor. Moreover the flexibility at the moment is achieved using sensors with the same form factor but adapters are under development to increase the adaptability of the system, both hardware and software. An Arduino MKR zero runs the application that can be run in three different modes: single measurement, time driven or position driven. The last feature is obtained through an optional on-board U-blox GNSS module that allows to georeference the performed measurements. This mode is mainly used when the measurement cell is applied on moving object, such as drones. The system is able to send the data collected and receive commands using MQTT protocol (HiveMQ broker) through a NB-IoT connection and interact with the user from an online dashboard created using Thingsboard. The use of the MQTT protocol allows to send the data to multiple endpoints if the data should be provided also to third parties. Moreover, the data and some parameters are also saved on a sd card. All the system is built on stand alone boards to achieve easy maintaince of the system and to allow a rapid change in the used technology (a plug and play LoRaWan module is under development). Being a multi-application platform, price of the device is of course highly dependent on the chosen set of sensors thus, in the end, on the application itself (i.e. Air pollution or gas emission in barns). To sum up, the device described is a possible solution for an affordable gas concentration measurement system that can be adapted to fit a large variety of use cases combining software and hardware solutions.

How to cite: Renzi, F., Cammillozzi, F., Cecchini, G., Filippi, A., and Valentini, R.: Design of an affordable and highly flexible IoT station for multiple gas concentration monitoring, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17527, https://doi.org/10.5194/egusphere-egu23-17527, 2023.

The so-called sea spray effect is known to considerably influence the stable isotope fingerprint of coastal samples (plants, soil, bones, teeth). However, the impact of sea spray on radiocarbon analyses in environmental samples from coastal sites has not been investigated, yet. Sea spray aerosols, containing, e.g., HCO3- or CO32- of marine origin, enter the terrestrial environment, shifting stable isotope values of terrestrial samples towards a seemingly marine isotope signature. Moreover, the sea spray is always accompanied by physiological effects in the sprayed plants, e.g., due to the salinity of the incorporated water, also visible in, e.g., stable carbon isotope data. A terrestrial herbivore, never consuming any marine food, can show a marine isotope signal due to the sea spray effect. While the marine reservoir effect, resulting from the consumption of marine food sources, can be investigated by calculating isotopic mixing models based on the δ13Ccollagen and δ15Ncollagen values of archaeological animal and human bones, the sea spray effect remains undetected in the δ13Ccollagen and δ15Ncollagen values of individuals consuming terrestrial protein (i.e., plant sources) influenced by marine aerosols. Therefore, it is important to investigate the influence of the sea spray on the radiocarbon signature.

The impact of either the direct or the accompanied, indirect sea spray effect can be visualized by an artificial sea spray experiment which was performed in a greenhouse. European beach grass (Ammophila arenaria, L.) was sprayed with mineral salt solution of different ion concentration but only traces of NaCl, with salty water from the Schlei inlet, collected next to the archaeological site of Haithabu (Germany), and with seawater from the Baltic Sea, collected at the western coast of Fehmarn island (Germany), respectively. Plants of all treatment groups were irrigated with Munich tap water (mainly originating from Mangfall valley). Radiocarbon analyses (F14C), stable as well as radiogenic isotope analyses (δ13CDIC, δ13Cbulk, δ13Ccellulose, δ18Ocellulose, δ18Osulfate, δ34Ssulfate, δ34Stotal S, 87Sr/86Sr), and (trace) elemental analyses were conducted on the plant, soil, and water samples (spray water, irrigation water) using mass spectrometry (AMS, IRMS, TIMS, ICP-MS, IC).

Radiocarbon analyses of the plants showed an impact due to the artificial sea spray. The indirect sea spray effect, resulting from either salinity (NaCl) or HCO3- stress, has an impact on plants’ F14C. The study demonstrates that a substantial proportion of 14C, which is taken up by the sprayed plants, originates from either irrigation or spray water. Stomatal conductance is markedly reduced due to both salinity and bicarbonate stress. Accordingly, less atmospheric 14CO2 can enter the plants via their stomata, while H14CO3-/14CO32-/14CO2 (aq.) can still be incorporated via the roots.

A multi-dimensional approach with a combined analysis of stable (δ13C, δ18O, δ34S), radiogenic (87Sr/86Sr), and radiocarbon isotopes in environmental samples allows to depict a detailed image of biochemical and physiological processes associated with the sea spray effect and will help to reveal new insights into the sea spray impact on the isotopic fingerprint of plants, animals, and humans, including potential caveats for radiocarbon analyses in coastal regions.

How to cite: Göhring, A., Hüls, C. M., Hölzl, S., Mayr, C., and Strauss, H.: Indirect sea spray effects on radiocarbon data of coastal plants – how physiological reactions in plants can be visualized by a combined investigation of stable, radiogenic, and radiocarbon isotopes in a greenhouse experiment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-128, https://doi.org/10.5194/egusphere-egu23-128, 2023.

Last glacial loess in Poland was deposited under periglacial conditions nearby to the regional maximum advance of the Scandinavian Ice Sheet during the Weichselian glaciation. Its glacier advance and retreat stages are expected to be mirrored in Loess-Paleosol Sequences (LPS) calling for reliable and exact dating. In the Bayreuth luminescence laboratory (BT) established modern SAR protocols of optical dating (OSL, pIRSL) were applied to the 4-11µm fine grain fraction of 38 loess samples from four LPS, distributed from Silesia to the Volhynian upland. Results were compared to published results from the Gliwice luminescence laboratory. Pleasing basic agreement even for surprising results is overshadowed however by somewhat differing apparent ages complicating a sound palaeoclimatic interpretation. A comparison of OSL and pIRIR ages obtained in BT poses a similar problem. OSL ages from quartz are prone to dose-dependent age underestimates but the critical absorbed dose may be grainsize-dependent. Experiences in BT resulted in favoring the fine grains from quartz, allowing for higher credible ages. Nevertheless, our quartz ages > ca. 50 ka are possibly but not necessarily underestimated, obviously dependent on the site and the providence of the quartz grains. In contrast, pIRIR ages turn out to be prone to overestimates due to incomplete bleaching leaving an unknown residual dose at deposition, a serious problem for beds with strong periglacial reworking.

Loess stratigraphy in Poland is well-based mainly on lithostratigraphy, palaeopedology, and periglacial geomorphology. Apart from – often problematic – radiocarbon dating and contradictory previous TL and OSL ages there is a lack however of independent physical dating methods and also of tephrostratigraphic markers. But at least the age of a prominent interstadial soil (or soil complex) now labelled L1SS1 at the end of the Middle Pleniglacial can now be fixed between ca. 30 and ca. 40 ka. Interpretation of dating results from samples older than L1SS1 is challenging. The observed diverging ages (OSL, pIRIR) are critical for the accurate time bracketing of geomorphologic and pedostratigraphic features such as ice wedging, thermokarst erosion events and interstadial soil formations and for their attribution to marine isotope stages. Alternative interpretations are discussed including possible periglacial mirroring of pre-LGM regional ice advances (Ristinge and Klintholm advances) in the southwestern Baltic Sea area.

I suggest that the strange behavior of quartz ages from different grain sizes is caused by various sources (ranging from Paleozoic crystalline rocks to Quaternary glacial drift) with very different geological and thermal histories, stored due to the very high resistance of quartz against weathering. Local and remote sources contribute to individual sedimentary beds of LPSs to varying extents. Thus, fine grains and coarser grains from an individual sample may be derived from diverse sources. In spite of the addressed uncertainties, for honesty reasons it is so far recommended aiming at age bracketing as narrowly as possible, simultaneously using OSL from different quartz fractions and pIRIR from fine polymineral grains. A refinement of this approach remains challenging as far as the sole reliable dating protocol is not ensured.

How to cite: Zoeller, L.: Ambiguity of luminescence ages from periglacial loess in Poland – “As you like it” or honesty with users?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1003, https://doi.org/10.5194/egusphere-egu23-1003, 2023.

EGU23-1396 | ECS | Posters on site | CL5.2

Tephra compositional data: are we doing it right? 

Simon Larsson and Matthew Bolton

Tephrochronology is often used for dating of natural archives and for correlation between study sites. Volcanic ashes (tephra) extracted from cores used for climate reconstructions function as common time-marker horizons and become anchor points in comparisons of age models from different studies. Given these uses, tephrochronology is well placed to help overcome the chronological challenges that hinder sufficiently precise dating of palaeoclimate records.

Tephras are identified based on their geographic and stratigraphic contexts, glass shard morphology, and geochemical composition. The geochemistry is most commonly analysed by electron probe microanalyser and presented as weight percentages of oxides of the nine or ten most abundant elements, often normalised to a 100 % total for ease of comparison. A simple exploration of such results and comparison to published data of previous tephra findings is usually enough for confident identification. However, compositional data of tephra findings from new studies continuously add to the complexity of tephrochronological investigations by increasing the amount of data available for comparison, including the addition of new potential candidates for identification. The increased likelihood of multiple candidates—sometimes with overlapping geochemistries—means that statistical data analyses are increasingly necessary.

Tephrochronologists have used principal component analysis and discriminant function analysis in situations needing statistical approaches, but these methods’ validity often requires certain assumptions not to be violated. A rarely considered example of such an issue is that compositional data suffers from the constant-sum constraint and must be converted by log-ratio transformations for some statistical analyses to function properly. As there is presently no consensus on a tephra compositional data curation procedure including log-ratio transformations, we have explored several variations and compared the results to see if a formal recommendation for such a procedure is relevant for the tephra community.

How to cite: Larsson, S. and Bolton, M.: Tephra compositional data: are we doing it right?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1396, https://doi.org/10.5194/egusphere-egu23-1396, 2023.

EGU23-1481 | Orals | CL5.2

How accurate are marine Δ14CDIC modelling approaches? 

Martin Butzin, Peter Köhler, Christoph Völker, Ying Ye, and Gerrit Lohmann

It has been estimated that Δ14C values of marine dissolved inorganic radiocarbon (Δ14CDIC) are primarily governed by transport and radioactive decay. This implies that Δ14CDIC can be considered as a radioconservative tracer which can be implemented into Earth system models without a full marine carbon cycle model. Here we evaluate the accuracies of the radioconservative modelling approach and of a further modelling approach which considers a different simplified representation of the marine radiocarbon cycle, presenting simulation results obtained with the ocean general circulation model FESOM and the marine biogeochemistry model REcoM. The relative uncertainties between the two simplified and the comprehensive treatments of the marine radiocarbon cycle are less than 5%. Therefore, the simplified Δ14CDIC modelling approaches should be sufficiently accurate for many marine radiocarbon studies. 

How to cite: Butzin, M., Köhler, P., Völker, C., Ye, Y., and Lohmann, G.: How accurate are marine Δ14CDIC modelling approaches?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1481, https://doi.org/10.5194/egusphere-egu23-1481, 2023.

EGU23-1551 | ECS | Posters on site | CL5.2

Continuous Radiocarbon Records by Laser Ablation – Status Report 

Melina Wertnik, Lukas Wacker, Nicolas Brehm, and Caroline Welte

The unique laser ablation (LA) setup at ETH Zurich (Switzerland), coupled to a MICADAS accelerator mass spectrometer (AMS), enables rapid 14C analyses and has been successfully employed for a broad range of carbonate archives such as stalagmites (Welte et al., 2021), otoliths (Andrews et al., 2019), and shells of Arctica islandica. An 193 nm ArF excimer laser is used to liberate CO and CO2 from the sample surface by ablation. The gas is then flushed with helium into the gas ion source of the AMS for online measurement.

Advantages of the novel techniques are a significant reduction in labour-intensive sample preparation and the speed of measurement, which minimises the expensive beam-time of the AMS. However, as a transient signal is measured where each sampling location is only measured for a short duration, uncertainties associated with LA-AMS are significantly higher than for conventional measurement techniques. Still, it is possible to locate strong signals such as a growth stop or the bomb spike very rapidly and precisely using only two scans of the sample. Here we present the status of the setup and progress on data reduction aimed at reducing the larger uncertainties. Preliminary results from comparisons of parallel tracks on a stalagmite allow testing the data reduction strategy and will be shown.

Andrews, A. et al. (2019), Marine and Freshwater Research, https://doi.org/10.1071/mf18265

Welte, C. et al. (2021), Climate of the Past, 17(5), 2165–2177, https://doi.org/10.5194/cp-17-2165-2021

How to cite: Wertnik, M., Wacker, L., Brehm, N., and Welte, C.: Continuous Radiocarbon Records by Laser Ablation – Status Report, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1551, https://doi.org/10.5194/egusphere-egu23-1551, 2023.

EGU23-2836 | ECS | Orals | CL5.2

The Role of Aged Organic Carbon in North Atlantic Fjord Sediments 

Craig Smeaton, Negar Haghipour, William Austin, and Timothy Eglington

Fjords are recognised as important hotspots for the burial and storage of organic carbon (OC) within their sediment, which potentially provides a long-term climate regulation service. Annually, it is estimated that 18 Mt of OC is buried within fjord sediments with between 55 – 62% of the OC originating from the terrestrial environment. The transfer of OC from the terrestrial environment to the fjord sediments is likely a significant pathway for aged OC to reach the coastal ocean. By estimating the quantity and mapping the spatial distribution of aged OC within the fjord sediments, we can develop a better understanding of the processes that govern the transfer of terrestrial OC from the catchment to the sediment of fjords, further constraining their role in long-term climate regulation.

Here we bring together radiocarbon analysis with isotopic and biomarker measurements to investigate the age of the surficial sediments within 46 fjords across the North Atlantic. The fjords in this study range from Scottish systems with catchments dominant with OC rich peat to the glaciated systems of Svalbard and Greenland.  The results from this analysis highlight that a multiple natural and anthropogenic processes govern the quantity and distribution of aged OC across North Atlantic fjords ranging between glacial input of fossil OC to the erosion of aged terrestrial material facilitated by deforestation.  This study highlights the fundamental need to understand the processes that govern the transfer of OC across the land-ocean interface to allow the role these marine sedimentary systems play in long-term climate regulation to be constrained.    

How to cite: Smeaton, C., Haghipour, N., Austin, W., and Eglington, T.: The Role of Aged Organic Carbon in North Atlantic Fjord Sediments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2836, https://doi.org/10.5194/egusphere-egu23-2836, 2023.

EGU23-2934 | ECS | Posters on site | CL5.2

Novel methods for determining the 14C age of microbially assimilated soil carbon 

Kari Finstad, Erin Nuccio, Katherine Grant, Jennifer Pett-Ridge, and Karis McFarlane

Soils are a significant component of the Earth’s carbon (C) cycle, yet a mechanistic understanding of what controls the turnover of this large C pool remains elusive. Microbial respiration of organic C accounts for roughly half of the total CO2 production from soils, though limited options exist for accurately identifying the source of C assimilated by microbial communities. Currently, radiocarbon (14C) analysis of evolved CO2 from soil incubations is the most common laboratory method for this, however they can introduce artifacts due to sample disruption and processing and can take months to produce sufficient CO2 for analysis. We present novel extraction methods which allow for the direct 14C analysis of microbial biomolecules and compare the results to laboratory incubations. Preliminary results suggest that in the upper 50 cm soil depths, the Δ14C from incubations is indistinguishable from that of extracted microbial biomass. Below 50 cm, the Δ14C of the microbial biomass is more depleted than that of the incubations, either due to the stimulation of labile C decomposition in the incubations, or the inclusion of biomolecules from non-living cells in the biomass extractions. Work is ongoing to identify the source of the extracted biomass pool and additional methods for isolating specific, short-lived biomolecules such as RNA, are underway to unambiguously determine the Δ14C of organic molecules being assimilated by active microbial communities.

How to cite: Finstad, K., Nuccio, E., Grant, K., Pett-Ridge, J., and McFarlane, K.: Novel methods for determining the 14C age of microbially assimilated soil carbon, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2934, https://doi.org/10.5194/egusphere-egu23-2934, 2023.

EGU23-4545 | Orals | CL5.2

Evaluating the accuracy of the Greenland Ice-Core Chronology (GICC) 

Sune Olander Rasmussen, Giulia Sinnl, Anders Svensson, and Bo Møllesøe Vinther

The full potential of palaeoclimate data relies on reliable time scales, i.e., a relation tying the physical dimension of the palaeoclimate archive with age. For many records, including ice cores, identification and counting of annual layers is the most direct and accurate way to obtain a time scale provided that high-resolution measurements of parameters showing annual variability are available. Annual-layer counting can provide very precise estimates of event durations and rates of change, but as errors accumulate with age, the accuracy decreases with depth/time. In contrast, radiometric methods often have good accuracy, and in principle, the two approaches can be combined to form highly accurate and precise time scales provided that the archives and their time scales can be robustly aligned. This can be done based on e.g. volcanic markers, common and correlatable features in cosmogenic isotope records, or on climatic wriggle-matching when the possible leads and lags between records is considered.

The Central Greenland ice cores are drilled in the interior areas of the ice sheet where precipitation rates are appropriate for the formation and preservation of annual layers, thereby allowing annual layers to be identified in the Holocene period and well into the last glacial period. The Greenland Ice-Core Chronology (GICC) is an attempt to derive a consistent, common time scale for the Greenland ice cores by combining data from multiple cores, using for each time period all available annually resolved data and then applying the time scale to the other cores by means of matching patterns of volcanic eruptions and other reference horizons. In this way, data from all the ice cores can be interpreted together on a common time scale (i.e., with very small relative dating uncertainty), greatly reducing the risk of artificial offsets due to misinterpretation of individual records. The first version of GICC, named GICC05, was published in 2006 and 2008, where the dating covered the time period back to 60 ka b2k, at which point the layers had thinned too much to continue with continuous annual layer counting.

Since then, high-resolution data from the newer Greenland ice cores NEEM and EGRIP have appeared, and comparisons to other palaeoclimate records on radiometric time scales have shown that in some sections, GICC05 was not as accurate as initially estimated, motivating a revision on the time scale. The top 3.8 ka of the time scale was recently revised, leading to changes in age of 10-15 years for the section older than 2500 years (see presentation by Giulia Sinnl). Here, we review the older sections of GICC05 in the context of other well-dated palaeoclimate archives and cosmogenic isotope records, as well as model-based estimates of climate leads and lags relevant when aligning climate records, and outline a plan for how to continue the revision of GICC05.

How to cite: Rasmussen, S. O., Sinnl, G., Svensson, A., and Vinther, B. M.: Evaluating the accuracy of the Greenland Ice-Core Chronology (GICC), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4545, https://doi.org/10.5194/egusphere-egu23-4545, 2023.

EGU23-6028 | Posters on site | CL5.2

Radiocarbon signatures of carbon phases exported by swiss rivers in the Anthropocene 

Timo Rhyner, Lisa Bröder, Margot White, Benedict Mittelbach, Florian Storck, Lucas Passera, Negar Haghipour, and Timothy Eglinton

Lateral carbon mobilization processes are particularly prone to anthropogenic perturbations due to human intervention of the land surface as well as aquatic corridors yet remain poorly constrained despite their importance as a key component of the C-cycle. A major source of this uncertainty involves processes modulating the sources and fate of carbon along the freshwater aquatic continuum. This study examines the radiocarbon (14C) signatures of particulate and dissolved organic carbon (POC, DOC, respectively) and dissolved inorganic carbon (DIC) transported by Swiss rivers with a view to assessing controls on the origin and cycling of carbon within corresponding watersheds. Twenty-one rivers were selected that span a range of watershed properties and are monitored by the National Long-Term Surveillance of Swiss Rivers (NADUF) program, enabling radiocarbon data to be interpreted within a broader hydrological and geochemical context.  Samples were collected during high-flow conditions in summer 2021, a year of extreme rain events. Average discharge of our sample set (n=21) was 299.76 +/- 513.87 m3/s, while the annual average discharge of all stations was 184.90 ± 264.92 m3/s. The range of D14C values of POC was -158‰ to - 446‰ (n = 21), while corresponding ranges of  D14C values for DOC and DIC were - 43‰ to - 377‰ and - 40‰ to - 301‰, respectively, indicating the presence of pre-aged carbon in all three pools. Hydrological properties such as discharge, runoff and precipitation did not appear as major significant controlling factors. Except for DI14C where annual average runoff of the past decade showed a significant negative correlation. Instead, based on Multivariate Regression Analysis, “alpine” variables such as mean basin elevation, slope, and barren areas were negatively correlated with D14C values of all three D14C-phases, while rivers draining lower elevation terrain, where agricultural land-use is more extensive were associated with higher D14C values in -the organic carbon pools (POC, DOC). Repeated sampling under different hydrological conditions and associated 14C (and 13C) measurements are being used to provide additional insights into the controls on the amount and nature of carbon exported by Swiss rivers, the interconnectivity between different carbon pools within the corresponding drainage basins and ecoregions, as well as to predict long-term trends in the context of changing climate and anthropogenic forcing.

How to cite: Rhyner, T., Bröder, L., White, M., Mittelbach, B., Storck, F., Passera, L., Haghipour, N., and Eglinton, T.: Radiocarbon signatures of carbon phases exported by swiss rivers in the Anthropocene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6028, https://doi.org/10.5194/egusphere-egu23-6028, 2023.

EGU23-6579 | Posters on site | CL5.2

An empirical study on the variability of luminescence ages for coeval loess samples 

Daniela Constantin, Robert Begy, Dimitri Vandenberghe, Daniel Veres, and Alida Timar-Gabor

An increasing number of studies exploit the advantages of a single-aliquot regenerative-dose protocol (SAR) for equivalent dose determination with sampling at relatively closely-spaced vertical intervals (of the order of 10-30 cm). The resulting ages are, at least in principal, ideally suited for age-depth modelling. The modelling, however, is made difficult owing to the variety and complex combination of uncertainties associated with luminescence dating. Moreover, we previously reported on a variability in age results for coeval loess samples that is significantly larger than expected and remains to be understood.

In this study, we examine this problem explicitly by observing the degree of precision and accuracy that can be achieved by luminescence dating of multiple coeval loess samples of known age. The main goal is to improve our understanding of how luminescence ages are to be incorporated into age-depth models, thus increasing their robustness and accuracy.

Fourteen samples were taken at closely-spaced horizontal intervals from loess deposits immediately over- and underlying the Campanian Ignimbrite/Y5 tephra layer (40Ar/39Ar dated to 39.2±0.1 ka), as exposed at a section in the Lower Danube Basin in southeastern Europe. Luminescence analyses were carried out using the single-aliquot regenerative-dose (SAR) protocol and OSL signals from 63-90 µm quartz fraction. We report an average age of 46 ka for the samples collected below the tephra layer and 40 ka for the samples collected above it. The individual random and systematic uncertainties contributing to the individual ages vary from 1.9 % to 5.4 % and from 6.0 % to 6.1 %, respectively. We obtain an improved overall precision on the age of the sedimentary context by calculating the weighted average age and combining the individual random and systematic uncertainties following Aitken (1985, Appendix B). Thus we report weighted average ages of 46 ka and 40 ka for the horizontally sampled sediment layers intercalating the ash layer and associated overall random uncertainties of 1.3 % and 1.1 %. The overall systematic uncertainties are 6.1 % and 6.0 %. The insights gained from this are discussed in relation to age-modelling studies of luminescence-dated paleoclimate archives, and loess deposits in particular.

Keywords: luminescence dating; precision; random uncertainty; quartz

How to cite: Constantin, D., Begy, R., Vandenberghe, D., Veres, D., and Timar-Gabor, A.: An empirical study on the variability of luminescence ages for coeval loess samples, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6579, https://doi.org/10.5194/egusphere-egu23-6579, 2023.

EGU23-7006 | ECS | Posters on site | CL5.2

A global synthesis of speleothem radiocarbon data – is it a sensitive proxy for past ecosystem processes? 

Franziska A. Lechleitner, Christopher Day, Jens Fohlmeister, Sophie Warken, Norbert Frank, Heather Stoll, and Caroline Welte

Speleothems, secondary cave carbonate precipitates, can serve as tools to reconstruct past terrestrial ecosystem processes, particularly related to soil and vegetation. Radiocarbon, often in conjunction with other geochemical proxies, has been increasingly used for this purpose, as the speleothem reservoir effect retains useful information on local ecosystem conditions. On the other hand, speleothems are also of interest to the radiocarbon community as they can be dated very precisely with the U-Th method, which may allow the reconstruction of atmospheric radiocarbon levels in time if the reservoir effect remained constant.

Over the past decades, a growing number of speleothem radiocarbon records have been generated from vastly different climate zones and ecosystem types. While much progress has been made in the interpretation of these records, a unified and global view of the factors driving variability in speleothem radiocarbon is still lacking. We compiled a global dataset of averaged speleothem radiocarbon measurements, and provide a critical evaluation of the applicability of the radiocarbon reservoir effect as a proxy for past ecosystem conditions. We compare our dataset to geographic (latitude, elevation), climatic (temperature and precipitation), and ecosystem and geological parameters (soil and bedrock thickness, soil age, vegetation type, and land cover). Our preliminary results show that it is difficult to extract a strong globally relevant driving factor for the mean absolute value in the reservoir effect at the investigated cave sites, and highlights the importance of detailed reporting of local conditions.

To provide insight into the amplitude range of processes affecting published speleothem radiocarbon records we perform a series of numerical forward modeling experiments. We test how the effects of changing soil age, soil pCO2, carbonate dissolution regime, and pyrite oxidation affect carbon isotopes in stalagmites.

Together, the global synthesis and modeling experiments provide us with the first global overview of how cave site parameters and climate and ecosystem processes affect speleothem radiocarbon records, and allow us to assess the sensitivity of this proxy as a tool for past ecosystem conditions.

How to cite: Lechleitner, F. A., Day, C., Fohlmeister, J., Warken, S., Frank, N., Stoll, H., and Welte, C.: A global synthesis of speleothem radiocarbon data – is it a sensitive proxy for past ecosystem processes?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7006, https://doi.org/10.5194/egusphere-egu23-7006, 2023.

EGU23-7936 | ECS | Posters on site | CL5.2

Sources of cave CO2 at Milandre cave, Switzerland constrained through multipool analysis of 14C and δ13C. 

Sarah Rowan, Marc Luetscher, Sönke Szidat, Thomas Laemmel, Oliver Kost, and Franziska Lechleitner

The cycling of subsurface karst CO2 is not well constrained in terms of its source and transportation pathway. The classical model suggests that cave CO2 is produced by the respiration of soils and vegetation in the catchment. In contrast, several new studies have proposed that the dominant source of CO2 is from the respiration of older organic matter situated deeper within the karst, or from the degassing of supersaturated drip water.

We present over a year of monitoring data from Milandre cave, northern Switzerland, whereby we evaluated the 14CO2 and δ13CO2 composition of the atmosphere in the cave catchment, catchment soil gas, well gas, and cave air. Drip waters located throughout the cave also underwent various analysis. The cave 14CO2 is more depleted compared to the soil and gas samples. The Keeling plot intercept of atmospheric and cave δ13CO2 is ~-26‰, indicating a dominant contribution from biological respiration. The dissolved inorganic carbon from various cave drips have an F14C from ~ 0.84 to 0.96 and δ13C from ~ -16‰ to -11‰. F14C and δ13C are inversely correlated.  Considering both the 14C and δ 13C results, this suggests either a source of CO2 from an aged reservoir of respiring organic matter contributing to the cave gas or substantial influence from degassing of 14C fossil carbonate CO2 from drip water. These results have implications for the understanding of the subterranean carbon cycle and the interpretation of speleothem carbon isotope records for paleoclimate studies.

How to cite: Rowan, S., Luetscher, M., Szidat, S., Laemmel, T., Kost, O., and Lechleitner, F.: Sources of cave CO2 at Milandre cave, Switzerland constrained through multipool analysis of 14C and δ13C., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7936, https://doi.org/10.5194/egusphere-egu23-7936, 2023.

The surficial 10 cm of Scotland’s saltmarshes are estimated to store 1.35 ± 0.33 Mt CO2 equivalent, approximately 3.37% of Scotland’s national greenhouse gas emissions in 20201,2. This is largely achieved through effective preservation of organic matter (OM) in low oxygen, sulphidic soils1. Saltmarshes gain organic carbon (OC) through in-situ (autochthonous) production by vegetation and benthic microalgae, and the accumulation of marine and terrestrial material during tidal inundation (allochthonous)3.

A key blue carbon challenge is to empirically understand, under current and predicted warmer conditions, the sources of OC accreted into and respired from saltmarshes. This can determine the proportion of the total OC pool which is additional through in-situ sequestration or from increased preservation of allochthonous OM3. Alongside 13C and 15N isotopes, radiocarbon (14C) analysis/dating can be used to determine the sources of saltmarsh surficial soil OC4.

We hypothesise that at ambient temperatures the younger and more labile, and predominantly autochthonous OM, will be preferentially decomposed.  But at elevated temperatures the aged, and predominantly allochthonous, OM pool will increasingly contribute to the respired greenhouse gases.

To test this hypothesis, we collected soil cores and surficial sediment samples from three contrasting Scottish saltmarshes. We analysed them for 14C to gain an understanding of the age and sources of the autochthonous and allochthonous OM accumulating. We also aerobically incubated sub-samples of the soil in temperature-controlled experiments at 11.1 ± 1°C (ambient) and 20 ± 1°C (elevated). The evolved CO2 was collected on molecular sieve traps and analysed for 14C content/age.

Our results will facilitate comparison of the age of the bulk OM and the respired CO2 to the thermogravimetrically measured reactivity of the OM determined using the recently developed Carbon Reactivity Index5. We will present our findings and introduce our ongoing work on anaerobic incubations of the same soils, which includes the novel measurement of the evolved 14CH4.

Our research contributes to a growing evidence base for emissions from saltmarshes, and the sources of OC accreting in their soils, which is vital for understanding how they cycle carbon and their ability to mitigate climate change. It will contribute to the creation of saltmarsh carbon cycle models and inform work to include saltmarshes in the UK’s Nationally Determined Contributions.

References

  • Smeaton C, Burden A, Ruranska P, et al. Using citizen science to estimate surficial soil Blue Carbon stocks in Great British saltmarshes. Front Mar Sci. 2022;9. Accessed November 28, 2022. https://www.frontiersin.org/articles/10.3389/fmars.2022.959459
  • Scottish Goverment. Scottish Greenhouse Gas Statistics 2020.; 2022. https://www.gov.scot/publications/scottish-greenhouse-gas-statistics-2020/
  • McTigue ND, Walker QA, Currin CA. Refining Estimates of Greenhouse Gas Emissions From Salt Marsh “Blue Carbon” Erosion and Decomposition. Front Mar Sci. 2021;8. Accessed January 26, 2022. https://www.frontiersin.org/article/10.3389/fmars.2021.661442
  • Hajdas I, Ascough P, Garnett MH, et al. Radiocarbon dating. Nat Rev Methods Primer. 2021;1(1):1-26. doi:10.1038/s43586-021-00058-7
  • Smeaton C, Austin WEN. Quality Not Quantity: Prioritizing the Management of Sedimentary Organic Matter Across Continental Shelf Seas. Geophys Res Lett. 2022;49(5):e2021GL097481. doi:10.1029/2021GL097481

How to cite: Houston, A., Austin, W., and Garnett, M.: A Novel Method for Radiocarbon Dating Greenhouse Gas Emissions from Saltmarsh Soils to Address Key Blue Carbon Challenges, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8033, https://doi.org/10.5194/egusphere-egu23-8033, 2023.

EGU23-8148 | ECS | Posters on site | CL5.2

Using the radiocarbon bomb spike to constrain the age of soil organic carbon delivered to Lake Constance sediments. 

Benedict V.A. Mittelbach, Margot E. White, Timo Rhyner, Stephan Wartenweiler, Negar Haghipour, Martin Wessels, Thomas M. Blattmann, Nathalie Dubois, and Timothy I. Eglinton

The residence time of carbon in terrestrial ecosystems, such as soils and freshwater, sets the pace of the terrestrial carbon cycle. Understanding export pathways and turnover times of soil organic carbon (OCSoil) is crucial to assess responses to climate and land use changes. Our study aims to quantify the average turnover time of OCSoil in the catchment of perialpine Lake Constance. Lake sedimentary sequences integrate organic carbon from their catchment and aquatic primary productivity. They act as both burial sites of organic carbon (OC) and time series archives of catchment processes. Thus, they can bridge the gap between plot scale observations, e.g., on soil carbon turnover, and observations made at the outlet of major river systems.

Sedimentary organic carbon sources include aquatic primary productivity, OCSoil, and rock-derived (petrogenic) OC. Stable carbon isotopes (δ13C) can be used to identify the relative contribution of these pools. The 5700-year half-life of radiocarbon (14C) coupled with the atmospheric nuclear bomb spike in the early 1960s can be used to infer the age and turnover rate of the OC pools on millennial to annual timescales. Bulk OC isotope analysis of a varved sediment core spanning the past ca. 110 years at quasi-annual resolution was used to constrain the age of soil carbon delivered to Lake Constance. We combined the geochemical data with a Markov-Chain-Monte-Carlo-based approach to identify the most probable age structure of aquatic and soil-derived OC components and to quantify their respective contributions in addition to petrogenic OC.

Radiocarbon analysis of sedimentary bulk OC reveals a well-defined but muted bomb spike in the early 1960s. However, bulk Δ14COC values remain below 0‰, implying a predominance of aged OC. Based on the δ13C-based three-component linear mixing model, we found these values to be the result of an OC mixture containing approx. 40% pre-aged soil carbon and up to 20% fossil petrogenic carbon.  Accounting for these inputs, we estimated that soil-derived OC delivered to Lake Constance is centennial in age, implying interim storage prior or subsequent to erosion from the landscape.

How to cite: Mittelbach, B. V. A., White, M. E., Rhyner, T., Wartenweiler, S., Haghipour, N., Wessels, M., Blattmann, T. M., Dubois, N., and Eglinton, T. I.: Using the radiocarbon bomb spike to constrain the age of soil organic carbon delivered to Lake Constance sediments., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8148, https://doi.org/10.5194/egusphere-egu23-8148, 2023.

EGU23-8195 | Orals | CL5.2

Lateglacial to interglacial sediment infills in Alpine valleys: timing, sediment provenance and paleo-environmental conditions 

Pierre Valla, Yann Rolland, Romain Delunel, Julien Carcaillet, and Christian Crouzet

Glacial/interglacial transitions in mountainous areas are marked by significant glacier retreat from forelands to inner massifs, resulting in large-scale and ephemeral lake formation that are subsequently filled (or not) by sediment transfer during lateglacial to postglacial times. When valley paleo-infills are preserved, they form precious archives to investigate (1) Alpine erosion dynamics and paleo-environmental conditions during key transition periods from full glacial stages to interglacials, and (2) glacial erosion patterns during susbequent glaciation.

In this contribution, we investigate such sedimentary deposits (locally called as "banquettes") in the French western Alps, and more precisely along the Isère valley and Val du Bourget. Previous research have attributed these deposits to the Riss – Würm transition due to their position under a basal compact till and to the MIS 6/5 transition up to early MIS 4 from palynological constraints, although no absolute ages has been available so far. Based on existing mapping of their spatial distribution and stratigraphic reconstructions, we sampled coarse-sand and sandy-gravel layers within these deposits for constraining both sediment deposition time (OSL dating) and provenance (glacial/postglacial origin, using terrestrial cosmogenic nuclide TCN 10Be in quartz). In addition, their spatial distribution provides estimates of maximum glacial erosion during the last glacial cycle, which can be subsequently used as spatial constraints for ice model predictions.

Our results confirm deposition times of these sedimentary units at the MIS 6/5 transition, with dating constraints from the late MIS 6 (ca. 145 ka) to the early MIS 5 (Eemien, 115-130 ka) for sandy layers. Upper sandy-gravel layers have younger deposition ages of ca. 80 ka, illustrating sediment fluxes at the transition from late MIS 5 to early MIS 4. We compare this temporal sequence to more recent sediment infills of the Isère valley (14C and OSL dating) during the Lateglacial to Holocene (MIS 2/1) transition. TCN data from sand samples also illustrate the sharp transition from full glacial to interglacial conditions, with a significant increase in 10Be concentrations from Lateglacial to post-glacial sediments. We propose that the observed signal can reflect changes in erosion rates, but also in glacier expansion or in paleo-environmental conditions, with export of stored subglacial sediments as well as the re-establishment of sediment/soil production and transfer along the catchment routing system following glacier retreat.

How to cite: Valla, P., Rolland, Y., Delunel, R., Carcaillet, J., and Crouzet, C.: Lateglacial to interglacial sediment infills in Alpine valleys: timing, sediment provenance and paleo-environmental conditions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8195, https://doi.org/10.5194/egusphere-egu23-8195, 2023.

EGU23-8323 | ECS | Orals | CL5.2

Using radiocarbon to identify the impact of climate and mineralogy on soil organic matter turnover 

Margaux Moreno Duborgel, Luisa Isabell Minich, Negar Haghipour, Beatriz González-Domíngez, Timothy Eglinton, and Frank Hagedorn

Soils are the largest carbon (C) reservoir in terrestrial ecosystems. There are still numerous uncertainties concerning the fate of soil organic carbon and its feedback on climate change. Radiocarbon is a useful approach to better understanding the carbon cycle. The nuclear weapon testing in the 1960s induced a peak in 14C atmospheric concentration – a signal that can be used to trace the incorporation and turnover of C in soil. By separating the soil in different fractions and measuring the 14C in them, we can quantify how much C and for how long is stored in soils, and where soil organic carbon is stabilised.

Our study aimed at identifying the impact of climate and mineralogy on soil organic matter turnover on a regional scale. We analysed C pools and 14C contents in the organic layer, mineral soil (0-20cm) and its fractions from 54 sites across Switzerland. These 54 sites are systematically spread across natural climatic and geological gradients and were repeatedly sampled in the 1990s and 2014. The mineral soil was incubated for 181 days and 14C was measured in the respired CO2. The mineral soil was fractionated according to density into particulate organic matter (POM) and mineral-associated organic matter (MAOM). We then oxidised the mineral-associated organic matter with hydrogen peroxide to remove its labile fraction of carbon. Our 14C dataset was analysed together with ancillary data comprising soil properties and climatic variables from the studied sites.

Our radiocarbon dataset showed that the carbon that was respired from the mineral soil originated predominantly from particulate organic matter. The bomb spike signal was incorporated in the organic layer and in the particulate organic matter, while the mineral-associated organic matter had turnover times on centennial to millennial time scales (from 94 to 3060 years). Further chemical oxidation of MAOM using hydrogen peroxide revealed a stronger depletion in radiocarbon of the residual fraction with Δ14C values ranging between -173 ‰ and -47 ‰. This indicates that the MAOM is a mixture of 14C-enriched organic matter and very old material.

With respect to the controlling factors of soil organic matter turnover time, the radiocarbon signature of the POM is most strongly affected by climatic variables such as mean annual temperatures. In contrast to POM, the mineral-associated organic matter, comprising the greatest pool of soil organic carbon is driven by chemical soil properties. For instance, older 14C ages are found in acidic soils with low pH values ranging between 3 and 4. In these soils, Al and Fe oxides concentrations are high. We showed that the concentrations of pedogenic oxides in the soil correlate with soil organic carbon concentrations in the mineral-associated organic matter. In soils with higher pH (>7), we can also find old 14C ages. In these soils, C is stabilised by interactions with calcium ions and carbonates.

Overall, our regional scale dataset shows that the net accumulation of labile soil organic matter seems to be climate sensitive, while mineralogy and weathering contribute most significantly to the stabilisation of organic carbon in the soil.

 

 

How to cite: Moreno Duborgel, M., Minich, L. I., Haghipour, N., González-Domíngez, B., Eglinton, T., and Hagedorn, F.: Using radiocarbon to identify the impact of climate and mineralogy on soil organic matter turnover, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8323, https://doi.org/10.5194/egusphere-egu23-8323, 2023.

EGU23-8974 | Posters on site | CL5.2

New developments in techniques for the sampling and analysis of atmospheric 14CO2 and 14CH4 at ETHZ and UNIBE, Switzerland 

Soenke Szidat, Thomas Laemmel, Dylan Geissbühler, Sarah Rowan, Philip Gautschi, Franziska Lechleitner, and Lukas Wacker

Radiocarbon (14C) measurements of atmospheric greenhouse gases such as carbon dioxide (CO2) and methane (CH4) are central in our capability to identify their provenance. The 14C content of these gases provides more insight into the age of their sources and mainly allows the distinction between fossil and modern ones. 14CO2 measurements can be used to analyze the nature of anthropogenic emissions (mostly fossil), or to discern on what organic matter pool respiration is taking place in a given environment. 14CH4 can also be used to detect anthropogenic emissions (from leaks of natural gas, for example) as well as natural emissions produced by methanogenesis, for example from ruminants or in wetlands.

The 14C analysis of atmospheric gases is made challenging due to their usual low concentration. Thus making the use of appropriate sampling methods, preconcentration and extraction techniques necessary to reach a sufficient amount of carbon for Accelerator Mass Spectrometry (AMS) analysis. We propose here a general view of the techniques that were developed at the Laboratory for Ion Beam Physics (ETHZ, Zurich), and at the Laboratory for the Analysis of Radiocarbon with AMS (UNIBE, Bern) for the purpose of analyzing CO2 and CH4 in atmospheric samples. We then discuss the practicability and the potential bias introduction of each of them.

The techniques are as follows :

  • Automated Graphitization Equipment with Automated Loading Facility (AGE-ALF)
  • Automated Graphitization Equipment with Cryogenic Trap (AGE-CT)
  • Methane Preconcentration and Purification System (MPPS)

Generally, samples were collected in sampling bags, either in 5-15L capacity for CO2 or larger than 60L for CH4. Types of samples that are considered are atmospheric CO2 and CH4 samples, CO2 from soil respiration, and CO2 from cave air. The different techniques are presented, and 14C results from standard gases are compared between the extraction lines and two MICADAS AMS systems at ETHZ and UNIBE.

How to cite: Szidat, S., Laemmel, T., Geissbühler, D., Rowan, S., Gautschi, P., Lechleitner, F., and Wacker, L.: New developments in techniques for the sampling and analysis of atmospheric 14CO2 and 14CH4 at ETHZ and UNIBE, Switzerland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8974, https://doi.org/10.5194/egusphere-egu23-8974, 2023.

EGU23-9064 | ECS | Orals | CL5.2

Paleoclimate and weathering on volcanic islands: insights from well-dated paleosols spanning the last Myr in the Central Azores 

Francisco Hevia-Cruz, Anthony Hildenbrand, Nathan D. Sheldon, François Chabaux, Fernando O. Marques, Julie Carlut, and Vittorio Zanon

Paleosols (PSs) contain valuable information about the climatic conditions under which they formed and constitute an outstanding archive of past weathering processes. Nevertheless, paleosol dating over most of the Quaternary remains challenging. Volcanic environments are unique sites for such purposes, as precise radiometric age determination can be achieved on volcanic units ‘bracketing’ PSs. Here, we present a combined geochemical and geochronological study of PSs spanning the last Myr in the Central Azores archipelago (Pico, Faial and São Jorge Islands; central North Atlantic). Precise K-Ar dating of lava flows on groundmass separates (unspiked Cassignol-Gillot technique) yield ages with a typical uncertainty of a few kyr, allowing us to tightly constrain PS ages and weathering rates near key paleoclimatic transitions. PS geochemistry further allowed us to reconstruct weathering conditions and estimate Mean Annual Precipitation and Temperature (MAP & MAT) by two proxies previously validated for other volcanic terranes (CIA-K and Clayeyness).

Four periods of PSs formation are constrained at 870-845 ka, ~725 ka, 320-280 ka and 130-45 ka. Most PSs formed just after interglacial peaks, with a few exceptions. Our MAP reconstructions are variable (600-1,500 mm/yr), but generally lower than current annual precipitations (~1,000 mm/yr). MAT estimates (14-28°C) are higher than present-day annual temperatures (~17.5°C). MAP & MAT variations are in general agreement with global climatic curves; the highest values (28°C, 1,500 mm/yr) are reached at ~855 ka, coinciding with an interglacial peak. The younger PSs (130-45 ka) indicate more stable MAP & MAT in the ranges 650-1,000 mm/yr and 15-20°C, respectively and seem to show a temperature decrease after the MIS5e interglacial stage.

Most paleosols were formed in a few kyr under high MAT (>17°C) and moderate to high MAP (>700 mm/yr), supporting a major influence of temperature on weathering kinetics. Parental material texture also had an important role, as several PSs formed upon pyroclastic deposits over most of their depth, whereas those developed on lava flows were generally restricted to the highly fragmented upper brecciated parts. Minimum vertical soil formation rates are in the range of ~0.3-4.5 cm/kyr, with a mean of ~1.7 cm/kyr and an outlier around ~10 cm/kyr. Those generally high values can be explained by the highly vesicular parental material, and by an exceptionally feldspar-rich (easily weathered) parental rock for the outlier.

As current precipitation and temperatures are higher than the threshold values of ~700 mm/yr and ~17°C under which most PSs formed, enhanced soil formation is expected for the near future, especially in the context of global warming and particularly in volcanic contexts. This may have important and fast impacts on local human activities, but also regarding CO2 consumption by rock weathering and geological hazards.

How to cite: Hevia-Cruz, F., Hildenbrand, A., Sheldon, N. D., Chabaux, F., Marques, F. O., Carlut, J., and Zanon, V.: Paleoclimate and weathering on volcanic islands: insights from well-dated paleosols spanning the last Myr in the Central Azores, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9064, https://doi.org/10.5194/egusphere-egu23-9064, 2023.

EGU23-10967 | ECS | Posters on site | CL5.2

Initial radiocarbon (14C) results of compound class persistence across a climate gradient in California grassland soils 

Katherine Grant, Marisa Repasch, Kari Finstad, Taylor Broek, Jennifer Pett-Ridge, and Karis McFarlane

Soils mediate the rapid cycling of carbon through the critical zone. Soil organic carbon (SOC) is composed of a complex mixture of plant and microbial derived organic compounds with distinct cycling timescales. The residence time of individual SOC components depends on a combination of factors, including compound reactivity, mineral association, and climate conditions, making it difficult to accurately quantify. However, radiocarbon analysis of specific compound classes can disentangle the mixture of SOC ages within a single sample. We modified methods to measure the Δ14C of distinct compound classes (lipids, amino acids, and carbohydrates) from bulk and physically fractionated grassland soils. Additionally, we measured the Δ14C of the water-extractable fraction (WEOC) and the residual acid-insoluble fraction. Samples were collected from a series of grassland meadows across California ranging in climatic conditions including temperature and precipitation. Sites include grassland meadows in Angelo Coast Range Reserve, Hopland Extension Reserve and Sedgwick reserve, and which receives 2160, 940, and 380 mm yr-1 of rainfall and is dominated by Avena spp. We sampled 1m soil pits by ~10cm intervals to study changes in SOC persistence with depth. We used solid state 13C-NMR to measure the relative abundance of the target compound classes in soil. The Δ14C of bulk soil decreased from about +50‰ to about +10‰ in the O-horizons to a range of about -150‰ to about -650‰ in the deepest horizons. At the Hopland site, the clay fraction (<63μm) had higher Δ14C values than both the bulk (<2mm) and sand (<2mm to >63μm) fractions. WEOC Δ14C values ranged from modern to about -45.6‰. Δ14C values of total extracted lipids ranged from 36±4‰ at the surface to -215±3‰ at depth. Quantifying the age distribution of distinct compound classes gives a direct measurement of the persistence between these phases.

How to cite: Grant, K., Repasch, M., Finstad, K., Broek, T., Pett-Ridge, J., and McFarlane, K.: Initial radiocarbon (14C) results of compound class persistence across a climate gradient in California grassland soils, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10967, https://doi.org/10.5194/egusphere-egu23-10967, 2023.

EGU23-11287 | ECS | Orals | CL5.2

14C-based deconvolution of relationships between carbon pools in Icelandic rivers and streams 

Nora Gallarotti, Lisa Bröder, Julie Lattaud, Negar Haghipour, and Timothy Eglinton

Rivers are important agents in the lateral transfer of carbon from terrestrial to the marine realm, thus forming a key component of the global carbon cycle. Carbon sources and transformations along the land-ocean aquatic continuum are dynamic with a complex interplay between dissolved and particulate, and inorganic and organic carbon pools. Elucidating interrelationships between these pools is hindered by multiple sources and processes that influence the carbon signatures of these pools in a dissimilar fashion. Icelandic streams and rivers offer an opportunity to directly assess the fluvial carbon pool dynamics due to the virtual absence of sedimentary rocks (e.g., shales, carbonates with a radiocarbon dead signature) that otherwise “muddy the waters” with respect to apparent sources and turnover times.

In order to characterize carbon transport patterns of Icelandic rivers and streams, we collected water samples from 43 river systems with watersheds that cover a wide range of catchment properties such as size, water discharge, climate as well as landcover. Here we assess the concentrations as well as the isotopic composition (13C, 14C) of particulate and dissolved organic carbon (POC; DOC, respectively) as well as dissolved inorganic carbon (DIC) alongside stable water isotopes (δ2H, δ18O) and major ion geochemistry.
Radiocarbon content (reported as fraction modern; F14C) of POC, DOC and DIC show similar patterns: lower F14C values (i.e., highest radiocarbon ages) are mostly associated with glacial runoff while higher F14C values (younger carbon) correspond to higher soil organic carbon content within the respective catchment. This dataset is but a first glimpse at carbon transport patterns in Icelandic rivers. Biomarker concentrations and isotopic compositions such as leaf waxes (n-alkanes, n-alkanoic acids) and soil derived lipids (branched glycerol dialkyl glycerol tetraether) will be used to further investigate provenance, transport and storage mechanisms in the diverse suite of Icelandic catchments.

How to cite: Gallarotti, N., Bröder, L., Lattaud, J., Haghipour, N., and Eglinton, T.: 14C-based deconvolution of relationships between carbon pools in Icelandic rivers and streams, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11287, https://doi.org/10.5194/egusphere-egu23-11287, 2023.

EGU23-11860 | Posters on site | CL5.2

A new UV-Oxidation set up for AMS radiocarbon analysis for small dissolved organic carbon in marine and fresh water samples 

Negar Haghipour, Maarten Lupker, Lukas Wacker, Margot White, Lisa Bröder, and Timothy I. Eglinton

Radiocarbon measurements of dissolved organic carbon (DOC) can give us valuable information about origin and age of DOC, a major, yet little understood component in the global carbon cycle. One way to measure DOC in water is to remove dissolved inorganic carbon first, oxidize organic carbon with UV irradiation and ultimately analyses the formed inorganic CO2 for 14C. The main challenge of UV-Oxidation (UVox) methods is to extract the typically low concentrations of DOC with low blanks required for relatively high precision 14C measurements. A disadvantage of currently used UVox methods is that only one sample can be oxidized in a laborious process at the same time in large volume. Here we present a UV-Oxidation system where up to 12 water samples can be oxidized simultaneously in 12 separate quartz reactors arranged around a single UV lamp in a compact setup. The simple setup further uses helium instead of vacuum typically used by conventional extraction lines to speed up the extraction of the formed CO2 after oxidation. The key improvements of the new UVox setup are: 1) Reduced amount of water needed (30- 60 ml) as samples are measured for 14C with the Micadas gas ion source., 2) UV oxidation efficiency for standards is high (96%), 3) No KI trap is needed, 4) Required time for sample preparation of up to 12 samples is 4-6 h, 5) combined the CO2 from different reactors to one trap.  We obtained 2.6 ± 0.6 µgC with F14C= 0.27±0.05 for processing blank.  We will present the first measurments of DOC samples from Swiss lakes, Canadian Beaufort Sea and the reproducibility of the line.

How to cite: Haghipour, N., Lupker, M., Wacker, L., White, M., Bröder, L., and Eglinton, T. I.: A new UV-Oxidation set up for AMS radiocarbon analysis for small dissolved organic carbon in marine and fresh water samples, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11860, https://doi.org/10.5194/egusphere-egu23-11860, 2023.

EGU23-12735 | Orals | CL5.2

14C analysis of atmospheric methane: development of a portable sampling system 

Giulia Zazzeri, Lukas Wacker, Negar Haghipour, Philip Gautschi, and Heather Graven

Measurements of radiocarbon (14C) in atmospheric methane (CH4) provide a powerful tool to distinguish fossil from biogenic methane emissions, because fossil methane is completely devoid of 14C. However, these measurements are particularly challenging as CH4 is at low concentration in the atmosphere and large volumes of air must be sampled.

At the Laboratory of Ion Beam Physics (LIP), ETH, we developed a portable sampler based on the laboratory prototype in Zazzeri et al. 2021 [1]. The new system enables extraction of carbon from CH4 while sampling in the field, reducing the sample processing in the laboratory and allowing collection of a hundred liters of air onto a 0.5 g zeolite trap.

Here we present an overview of the sampling system and the technical developments that have been implemented at LIP. The relatively small size of the sampler and its interface with the gas ion source of the AMS system make 14CH4 measurements much easier to perform. Its portability will enable collection of CH4 samples in any environment, with the potential of assessing the radiocarbon signature of methane emissions that have not been yet characterized.

[1] Zazzeri, G., Xu, X., & Graven, H. (2021). Environmental Science & Technology, 55(13), 8535-8541.

How to cite: Zazzeri, G., Wacker, L., Haghipour, N., Gautschi, P., and Graven, H.: 14C analysis of atmospheric methane: development of a portable sampling system, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12735, https://doi.org/10.5194/egusphere-egu23-12735, 2023.

EGU23-14183 | ECS | Posters on site | CL5.2

Radiocarbon constraints on lateral export of soil organic carbon in rivers of Switzerland 

Alexander Brunmayr, Heather Graven, Timo Rhyner, Margaux Moreno Duborgel, and Negar Haghipour

Lateral carbon transport through inland waters plays a critical yet often overlooked role in the delicate balance of carbon exchanges controlling the net uptake and storage of anthropogenic carbon in terrestrial ecosystems. Though new terrestrial carbon cycle models are increasingly making an effort to explicitly represent these traditionally neglected lateral fluxes, the parameters governing lateral carbon transport, particularly the composition and ages of exported soil carbon, remain ill-constrained. In this study, we explore the power of combined river and soil 14C datasets as a parameter constraint when calibrating a novel carbon cycle model connecting the terrestrial and riverine systems in catchments of Switzerland. For the riverine data, we use 14C measurements of particulate organic carbon (POC), dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) for water samples collected during high-discharge events in 2021 across Switzerland. Within those river catchments, we have forest soil 14C data at various depths down to 60cm for up to three samples in time (mid 1990s, 2014, and 2022). The soil samples were split into the following representative fractions: soil dissolved organic carbon (soil-DOC), particulate organic carbon (soil-POC), and mineral-associated organic carbon (soil-MOC), which represents the older and more recalcitrant component of soil carbon. This study investigates to what extent using these fraction-specific 14C measurements together with 13C and nitrogen data for both rivers and soils allows us to not only distinguish the different sources of riverine carbon but further analyze the composition and age of the soil organic carbon ending up in Swiss rivers.

How to cite: Brunmayr, A., Graven, H., Rhyner, T., Moreno Duborgel, M., and Haghipour, N.: Radiocarbon constraints on lateral export of soil organic carbon in rivers of Switzerland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14183, https://doi.org/10.5194/egusphere-egu23-14183, 2023.

EGU23-297 | ECS | Orals | SSS9.1

Pedophysics: a python package for soil geophysics. 

Gaston Mendoza Veirana, Philippe de Smedt, Jeroen Verhegge, and Wim Cornelis

Near surface geophysical electromagnetic techniques are proven tools to support ecosystem services such as agriculture, soil remediation, nutrient management, and heritage conservation. Key influencing geophysical properties are electrical conductivity (σ, or resistivity (ρ)), dielectric permittivity (𝜀) or magnetic susceptibility (μ), that are targeted to model soil properties and state variables such as texture, bulk density, cation exchange capacity (CEC) or water content. To translate geophysical properties into quantitative information on the targeted soil properties, relationships between these have to be considered in appropriate models. These so-called pedophysical models can then be integrated into interpretation schemes (e.g., after inversion, or through incorporating this into forward modelling procedures). This modelling step, translating geophysical properties into soil properties (and vice versa), thus constitutes a key aspect of near surface exploration.

While hundreds of pedophysical models exist to perform this task, these often depend on many properties and parameters defined within a specific range e.g., electromagnetic frequency, texture, and salinity; impeding applications to cases where information about the studied soil is scarce. Therefore, selecting an appropriate pedophysical model for a given scenario is often a very complex task.

To facilitate solutions for pedophysical modelling we present pedophysics, an open source python package for soil geophysical characterization. The package implements up-to-date models from the literature and, based on the user’s needs, automatically provides an optimal solution given a set of input parameters and the targeted output.

First, a virtual soil is defined by inputting any of its available properties. This soil can be defined in discrete states to simulate the evolution of its properties over time. Secondly, a module (predict) is called to predict the target property of interest. Following this workflow, for example, a soil with a given texture and changing water content could be defined to obtain its 𝜀 or σ at a predefined frequency, or, inversely, its water content could be predicted based on changing σ.

However, as soil properties required as input parameters for pedophysical models are often unknown, it can, in such cases, be impossible to obtain a viable prediction outcome. The pedophysics package accounts for such limitations by implementing pedotransfer functions, that allow obtaining the missing properties from the available ones. For example, if CEC is unknown, it is determined based on soil texture and a location.

In summary, the package synthesizes specific pedophysical modeling knowledge. Time-varying properties can be calculated in a straightforward way, and, through the integration of pedotransfer functions, target properties can be predicted with a minimum of information about the studied soil. Thus, by translating known properties to targeted ones, pedophysics is contributing to improve interpretability of near surface modeling schemes; enhancing soil electromagnetic geophysical exploration techniques in ecosystem services applications.  

How to cite: Mendoza Veirana, G., de Smedt, P., Verhegge, J., and Cornelis, W.: Pedophysics: a python package for soil geophysics., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-297, https://doi.org/10.5194/egusphere-egu23-297, 2023.

EGU23-2251 | ECS | Orals | SSS9.1

Sensor-based mapping of Danish peatlands 

Triven Koganti, Diana Vigah Adetsu, Martin Larsen, Kristoffer Skovgaard Mohr, Amélie Beucher, and Mogens H. Greve

Pristine peatlands are precious for their Carbon (C) storage ability and the vast range of ecosystem services they provide. Globally, peatlands were heavily altered over the years especially by draining the water table for meeting energy and agricultural needs. Draining the peat results in its enhanced microbial decomposition, increased dissolved C leaching and increased susceptibility to peat fires, thus turning peatlands into C-source ecosystems. Currently, the carbon dioxide (CO2) released from degraded peatlands amounts to approximately 5% of global anthropogenic emissions. Climate change concerns have sparked an interest to reduce these emissions and different initiatives are put forward for the protection, proper management, and restoration of the peatlands. Denmark has its own national goal of reducing CO2 emissions by 70% by 2030; of which agriculture is expected to be a significant contributor. Comprehensive characterization of peat inventory providing status on the C stocks, water table depths and emissions is required for improved land use planning as almost 4.8 million tonnes of CO2 per annum is released from cultivated organic lands (~ 170,000 ha in total). To achieve this, measurements of peat depth (PD) for volume characterization are invaluable. The conventional mapping approach of PD using peat probes is laborious, time-consuming, and provides only localized and discrete measurements. In addition, these manual probing measurements are also prone to errors as occasionally the probes are obstructed by stones, wood and human artefacts causing underestimation and other times they might easily penetrate the soil underlying the actual peat causing overestimation. In Denmark, we are comparing and contrasting the suitability of different electromagnetic sensors, precisely, working on electromagnetic induction (EMI), ground penetrating radar (GPR), and gamma-ray radiometric (GR) principles to accurately characterize the Danish peatlands. We are testing the sensors on both ground-based and air-borne configurations to improve the feasibility, increase accessibility and save costs. A novel drone-based transient EMI sensor is being designed in this direction. So far the results suggest that the EMI and GR techniques are promising to demarcate the peatland boundaries and estimate the PDs up to a certain extent; depending on the gradient in transition between the mineral and organic soils. Ground penetrating radar provided unequivocal results in high-resistive ombrotrophic peat while failing in low-resistive minerotrophic peat due to low signal penetration. In the drone-borne configuration, GR proved superior due to its ease of use and less to no success was achieved using a GPR. Moving forward, we plan on fusing the multisensor datasets using machine learning to improve the prediction accuracy of PDs, find a means for mapping water table depths and perform advanced modelling for comprehending the effects of different management scenarios on CO2 emissions.

How to cite: Koganti, T., Vigah Adetsu, D., Larsen, M., Skovgaard Mohr, K., Beucher, A., and H. Greve, M.: Sensor-based mapping of Danish peatlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2251, https://doi.org/10.5194/egusphere-egu23-2251, 2023.

Farms in Western Australia (WA) are highly variable in soil texture and water retention capacity; therefore, spatial information of soil moisture status in the field is important for crop management. In practice, farmers often rely on point sensors to determine soil moisture in their fields for crop planning. The limitation of point measurements to account for spatial variability highlights the need to develop methods to assess soil moisture across variable broadacre fields. This information could be used for more effective site-specific crop management practices. In this study, we used a mobile nonintrusive electromagnetic induction (EMI) sensor to map soil apparent electrical conductivity (ECa) and to predict soil moisture levels across the field at three depths (0 – 0.5, 0.5 – 0.8 and 0.8 – 1.6m). The predicted soil moisture was compared with the point measurements of soil moisture sensors and soil samples. The inverted electrical conductivity (EC) from EMI surveys was converted into soil moisture using calibrations between electrical resistivity tomography (ERT) to volumetric moisture, which were developed for the different soil textural classes of the field, with R2 of 0.97 to 0.99. The soil moisture variability of the field was also compared with the spatial distribution of 2019 barley yield production. No significant difference was found between the EMI estimated soil moisture values and the point moisture measurements, as well as moisture extracted from soil samples for 0 – 0.5m and 0.5 – 0.8 m depths with Pearson R values of 0.62 and 0.73 respectively. Barley yield was not correlated with mapped soil moisture or soil texture, which may be due to relatively high initial moisture levels following two years of fallow rotation. This study successfully demonstrated spatial soil moisture estimation using EMI sensor in a field with horizontally and vertically variable soil texture.

How to cite: Shaukat, H., Flower, K., and Leopold, M.: Comparing quasi-3D soil moisture derived from electromagnetic induction with 1D moisture sensors and correlation to barley yield in variable duplex soil, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4650, https://doi.org/10.5194/egusphere-egu23-4650, 2023.

EGU23-5601 | ECS | Posters on site | SSS9.1

Monitoring soil status in an irrigated saline reclaimed marsh area in SW Spain using multi-receiver electromagnetic induction sensing and inversion 

Mario Ramos, Mohammad Farzamian, José Luis Gómez Flores, and Karl Vanderlinde

Multi-receiver electromagnetic induction (EMI) shows increasing potential for effective depth-specific monitoring of shallow soil properties as EMI sensors become available that provide simultaneous apparent electrical conductivity (ECa) measurements for small depths of exploration (DOE). Inversion of such ECa data results in more detailed soil profile EC estimates that can provide a completer understanding the soil hydrology and chemistry near the surface (<1 m depth). We demonstrated this by monitoring the soil status weekly at eight measurement locations in an irrigated cotton field in a saline reclaimed and tile-drained marsh area in SW Spain using a multi-receiver EMI instrument that provided ECa for 12 different DOEs. Soil water content and water table depth and conductivity were monitored at the eight locations. Inversion of the ECa data at the eight locations yielded characteristic EC profiles that depended on soil water content, irrigation and salt leaching, and water table depth. A depth-specific correlation analysis of the EC profiles and their first derivative elucidated the depths where the correlations were strongest and for which the best estimates of water content and water table depth and salinity could be obtained. The established relationships were then used to estimate these properties along two transects that contained each four of the monitoring locations. This approach allowed the detection of areas where a shallow water table emerged during the irrigation season which led to topsoil and crop salinization and can therefore assist decision-making in soil, water and crop management in this area.

 

Acknowledgement

This work is funded by the Spanish State Agency for Research through grant PID2019-104136RR-C21/AEI/10.13039/501100011033 and by IFAPA/FEDER through grant AVA2019.018.

How to cite: Ramos, M., Farzamian, M., Gómez Flores, J. L., and Vanderlinde, K.: Monitoring soil status in an irrigated saline reclaimed marsh area in SW Spain using multi-receiver electromagnetic induction sensing and inversion, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5601, https://doi.org/10.5194/egusphere-egu23-5601, 2023.

EGU23-5663 | Posters on site | SSS9.1

Development of a non-invasive modular electromagnetic induction (EMI) system with spatial high resolution for agricultural applications 

Markus Dick, Egon Zimmermann, Johan Alexander Huisman, Achim Mester, Martial Tchantcho Amin Tazifor, Peter Wüstner, Michael Ramm, and Stefan van Waasen

The acquisition of high-resolution soil information is essential for more environmentally friendly and efficient management of agricultural areas in the context of precision farming. The electrical conductivity (EC) of the soil can be measured quickly and without direct contact using electromagnetic induction (EMI) systems. The EC can be related to soil properties such as soil water content, pore water electrical conductivity, nutrition, clay content and salinity. EMI devices provide an apparent conductivity value that averages electrical conductivity variations with depth. To reconstruct the depth-dependent conductivity from measured data, EMI devices with different coil separations between transmitter and receiver or coil orientations are required. For the measurement with different coil separations, measurements with several commercial devices are commonly combined. However, mutual interference between devices is problematic here, so that measurements with the individual devices must be carried out either one after the other or with sufficient spatial separation, which complicates data acquisition substantially. To simplify EMI data acquisition and to improve depth resolution, an EMI device is required that provides simultaneous measurements with a larger number of freely selectable coil distances. To achieve this, a modular scalable multi-coil system (SELMA) with one transmitter and 12 receiver coils was developed. In the first test configuration, the receiver coils are arranged in a coplanar configuration and equally distributed from 0.3 to 3.6 m in a straight line. The system currently operates at a transmission frequency of 20 kHz and is designed for a measurement range from 2 mS/m to 100 mS/m. The noise of the measured apparent electrical conductivity is below 1 mS/m at a measurement rate of 10 Hz. To achieve modularity, decentralised System-on-Chip modules are used for the data acquisition, which are connected to the control unit (PC) via Ethernet. In addition to the apparent conductivity values, temperatures, pressure, and acceleration are recorded. The reliability of the EMI measurements was checked by repeatedly measuring a transect using a custom-made sled.

How to cite: Dick, M., Zimmermann, E., Huisman, J. A., Mester, A., Tchantcho Amin Tazifor, M., Wüstner, P., Ramm, M., and van Waasen, S.: Development of a non-invasive modular electromagnetic induction (EMI) system with spatial high resolution for agricultural applications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5663, https://doi.org/10.5194/egusphere-egu23-5663, 2023.

EGU23-5785 | ECS | Posters on site | SSS9.1

Optimisation of an ERT acquisition for soil-plant interaction in presence of biochar 

Marco D. Vasconez-Maza, Julien Thiesson, Roger Guerin, Frederic Delarue, Aida Mendieta, and Damien Jougnot

In the mitigating strategies of human impact on environments, the biochar addition to shallow soil horizon represents a promising way among the existing Carbon Dioxide Removal technique. This study is part of a project that aims at evaluating the impact of the presence of biochar in soils on the growth of roots. Geophysical techniques are a good candidate for non-invasive investigation and field monitoring. Among the existing techniques, Electrical Resistivity Tomography (ERT) has already shown great potential for detecting the presence and growth of roots in agricultural soils.

In this study, our goal is to test whether ERT is able to track changes in root growth in a technosol. The field experiment takes place on a setup consisting of 20 plots of 2 meters by 3 meters where the first 0.3 meters were disturbed and for half of them biochar has been incorporated (ca. 2% wt.). As we are expecting 3D effect on this specific field (effects of the limits of the plot, effects of the roots), we design a numerical study to determine the best experimental setup for a 2D ERT profile using pyGIMLi, an open-source software library for geophysical inversion.

We conducted several numerical simulations to determine the optimal dimensions of a meshed body, which was considered as a semi-infinite space, to simulate profiles of 48 and 96 electrodes separated by 0.1 meters. Field measurements on plots with and without biochar showed electric resistivity values of 45 ohm m and 56 ohm m, respectively, suggesting that ERT might be able to detect the biochar presence. Using this information, we focus our numerical simulations on a suitable configuration to assess the effect of biochar onto root growth.

How to cite: Vasconez-Maza, M. D., Thiesson, J., Guerin, R., Delarue, F., Mendieta, A., and Jougnot, D.: Optimisation of an ERT acquisition for soil-plant interaction in presence of biochar, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5785, https://doi.org/10.5194/egusphere-egu23-5785, 2023.

EGU23-5921 | ECS | Posters on site | SSS9.1

Remote sensing techniques to assess the weeds adaptability to salinity stress induced by soil changes 

Nebojša Nikolić, Sara Cucchiaro, Eugenio Straffelini, Paolo Tarolli, and Roberta Masin

Weeds pose one of the major threats to plant production, as they can reduce yield, interfere with harvest, and host different harmful organisms. Unlike crops, weeds are characterized by great plasticity and adaptability to agroecosystem changes, making them an even more critical threat in a constantly changing environment. The influence of climate change in the form of different stresses to which plants are being more and more exposed is being extensively studied in crops, yet there are few studies concerning weeds. Still, considering the adaptability potential of weeds, they can represent an even more significant threat to agricultural production when abiotic stress, such as salinity, is introduced in the agroecosystem. Currently, remote sensing techniques may be exploited to derive useful, frequent, and low-cost information at different spatial scales. In this work, the Structure from motion (SfM) technique paired with Unmanned Aerial Vehicles (UAV) was used to map the distribution changes of Abutilon theophrasti in July and August 2022 in three different crop fields in the Po river delta, North-Eastern Italy. The multi-temporal orthomosaics obtained by two various SfM surveys had an image resolution of 2 cm, allowing an accurate photo interpretation and the realization of precise maps of species distribution. In the meantime, different soil samples have been taken from the fields above, and their position was measured by a Global Navigation Satellite System (GNSS), GeoMax Zenith 40. The salinity level of soil samples has been determined by measuring the electrical conductivity using XS Instruments COND 80 electrical conductivity meter (Giorgio Bormac s.r.l, Carpi, Italy) at a sensitivity of 1 µS. Salinity values were spatialized in the study areas, realizing salinity maps through the spatial interpolation tools of the Geographic information system (GIS) software. The salinity maps overlapped the maps of single plants of A. theophrasti. In both of the multi-temporal surveys performed, results show that plants of A. theophrasti can be found in areas where the soil salinity is higher than 8 dS/m, where most of the crop plants have perished.  Considering that the weed plants were present at the same place in both surveys, this indicates that A. theophrasti can tolerate the rise of salinity in the fields better than the crop plants and can therefore outcompete them. These results suggest that soil salinization can have a double negative effect on crop production, both causing abiotic stress and increasing competition.

Acknowledgments: This study was carried out within the Agritech National Research Center and received funding from the European Union Next-GenerationEU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) – MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 – D.D. 1032 17/06/2022, CN00000022).

How to cite: Nikolić, N., Cucchiaro, S., Straffelini, E., Tarolli, P., and Masin, R.: Remote sensing techniques to assess the weeds adaptability to salinity stress induced by soil changes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5921, https://doi.org/10.5194/egusphere-egu23-5921, 2023.

EGU23-7128 | ECS | Orals | SSS9.1

Electrical Resistivity Tomography (ERT) to assess the drip irrigation water in a field cultivated with melon 

Agnese Innocenti, Veronica Pazzi, Marco Napoli, Riccardo Fanti, and Simone Orlandini

Characterization of agricultural soils using geophysical techniques makes it possible to study the heterogeneity of a soil and the preferential pathways of water flows without causing disturbances to soil and plants. Increased knowledge of soil heterogeneity allows the most optimal management of the water resource in terms of crop, yield and sustainability. In this study, time lapse monitoring, using electrical resistivity tomography (ERT), is proposed as a reliable and non-invasive technique to quantify the movement of water flows during the irrigation process.

ERT surveys were conducted in melon cultivated land in southern Tuscany (Italy). Four survey campaigns were carried out between June and August 2022, in which ERT data were collected by taking measurements, before, during, and after the irrigation phase. The investigation was conducted with a 3-D grid in which the 72 electrodes were spaced 0.3 m apart and arranged in three parallel lines, 0.3 m apart and 6.9 m long, for a total of 24 electrodes in each line. The plants were located above a ridge having a height of 20 cm with respect to the ground level and the electrodes were positioned to incorporate 5 melon plants in the configuration. A dipole-dipole configuration was adopted for the acquisition of electrical resistivity data. Commercial ViewLab 3D software was used to process the geoelectrical data.

The interpretation of the ERT results provided information on the spatial and temporal distribution of water flows in the soil and in the root zone of melons during the irrigation phases. The investigation made it possible to identify the preferential ways of infiltration of the irrigation water, the points where the water is absorbed by the roots, and the points where the water instead follows a preferential way distributing itself entirely below the area of root growth. During the investigations, the irrigation time underwent changes dictated by the climatic conditions, therefore the irrigation time and frequency were increased. This manifested itself in the ERT sections with an increase in the conductivity below the roots, i.e., at a depth of about 35 - 40 cm with respect to the ground level. This phenomenon can be explained by the fact that over time the water has developed a greater preferential path, completely bypassed the root system and collected below it, in the zone delimiting the worked soil with the unworked soil.

In the present case study, the ERT technique proved to be a valid survey and monitoring method for mapping the preferential paths of water flows in agricultural land. The ERT sections made it possible to study the distribution of water along the soil profile, highlighting the presence of preferential paths that produce an accumulation of water below the root zone and therefore in an area that is not very usable for cultivation. This technique can therefore be used in this context to study a better irrigation system and an optimal management of the water resource, avoiding preferential paths of the flows which lead to a lower availability of water for the plant.

How to cite: Innocenti, A., Pazzi, V., Napoli, M., Fanti, R., and Orlandini, S.: Electrical Resistivity Tomography (ERT) to assess the drip irrigation water in a field cultivated with melon, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7128, https://doi.org/10.5194/egusphere-egu23-7128, 2023.

EGU23-7736 | Orals | SSS9.1

Geophysical monitoring of the fresh-saline groundwater interface in Belgian polders 

Guillaume Blanchy, Ali Mehmandoostkotlar, Bert Everaert, Dominique Huits, Sarah Garré, Thomas Hermans, and Frédéric Nguyen

Polders are areas reclaimed on the sea thanks to hydraulic structures like dikes. To prevent flooding, these low-lying areas are constantly drained by a network of ditches that release excess water in the sea (e.g. at low tide). The use of subsurface drainage pipes connected to existing drainage ditches further enabled the drainage of the lands and made them suitable for agriculture. While the groundwater remains saline water from its seaborn nature, with years and precipitation, a fresh water lens, lighter than the deeper saline water, developed near the soil surface, on top of the saline water. This fresh water lens is essential for most conventional crops that would suffer from saline conditions. The thickness of freshwater lenses varies throughout the year as a function of the recharge from rainfall and evapotranspiration.

However, intensive rainfall events and prolonged summer droughts are becoming more frequent with Climate Change and lead to decreasing freshwater lens thickness, endangering crop yield. Controlled drainage systems that enable to regulate the water level in the subsurface drains has the potential to mitigate this issue by imposing a temporary higher water level, hence increasing recharge of the freshwater lens. 

To better understand the dynamics of the fresh/saline water interface throughout the year, we equipped two fields with multilevel piezometers with both head and salinity sensors replicated three times in each field. Along each multilevel piezometer we also installed 1D resistivity sticks with 16 electrodes to obtain a vertical electrical resistivity profile. In addition, electromagnetic induction surveys enabled us to expand the local observations to the entire area (4 ha in total).

The datasets collected in the two fields in the conventional scenario (i.e. without controlled drainage) during the first year, showcase the usual dynamics of the interface, its lateral as well as vertical variability. The use of geoelectrical techniques enable us to distinguish fresh and saline water boundaries and its variability per soil layers. The electromagnetic induction surveys reveal old paleochannels that influence the dynamics of the freshwater lens at the field-scale. Moreover, the dataset also demonstrates how different crops (grass and flax) lead to different ground water and salinization dynamics. In this work, we present our first year of collected field data and related interpretation before the installation of the controlled drainage system.

How to cite: Blanchy, G., Mehmandoostkotlar, A., Everaert, B., Huits, D., Garré, S., Hermans, T., and Nguyen, F.: Geophysical monitoring of the fresh-saline groundwater interface in Belgian polders, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7736, https://doi.org/10.5194/egusphere-egu23-7736, 2023.

EGU23-8126 | ECS | Orals | SSS9.1

Impact of drought on the water status of vines in a Bordeaux vineyard 

Quentin Chaffaut, Myriam Schmutz, and Jehanne Cavailhes

France is one of the largest producer of wine in the world. Thus, viticulture is a major activity area, particularly in south-west of France where vineyards occupy as much as 42% of the agricultural surface. Vineyards worldwide are being subjected to stress brought about by changes in average temperatures, precipitation, seasonal timing that drives phenology, as well as extreme weather events (van Leeuwen, 2004). Specifically, the Bordeaux vineyards are submitted to strong climate change impact, due to the increase in the duration of heat waves (i.e., increase in evaporative demand), and the decrease in summer precipitations (i.e., decrease in water availability in the soils; Soubeyroux et al., 2020). These stressors contribute to Grape yield and quality.

Our approach consists of identifying the factors that control water availability in vineyard soils in order to adapt cultivation practices.

For this purpose, we have instrumented a vineyard plot (~1 ha) in Medoc. This observatory allows the monitoring of water fluxes within the soil-vine-atmosphere continuum on two rows of vines located in areas with contrasting soil types: one is located in a sandy area, while the other is located in a clayey area. The observatory combines:

  • Soil water status monitoring with
  • Spectral Induced Polarization (SIP) measurement campaigns carried out along the two selected rows of vines and repeated at a bi-monthly rhythm,
  • two permanent multi-level soil water content probes
  • Vines water status monitoring using sap flow sensors, together with water potential measurement campaigns repeated on a monthly basis
  • Ground water level continuous measurement sensors
  • Meteorological parameters monitoring

Our observations show that during the drought of the summer 2022, the vines in the sandy row suffer of greater water stress than the vines in the clay row, and that the soil in the sandy row dries out more quickly and to a greater depth than the soil in the clay row. This highlights the impact of soil type on soil water availability. Our early results suggest that in the case of a prolonged drought period, the vines located on clay plots would thus suffer less from water stress than in the case of plots with more draining soil.

Références:

Soubeyroux, JM, Bernus, S, Corre, L, Gouget, V, Kerdoncuff, M, Somot, S, Tocquer, F, 2020. Le nouveau jeu de simulations climatiques régionalisées sur la France pour le service DRIAS, XXXIIIeme colloque de l’Assoc Internat de Climatologie, pp 637-642.

Van Leeuwen, Cornelis, Philippe Friant, Xavier Choné, Olivier Tregoat, Stephanos Koundouras, and Denis Dubourdieu. 2004. Influence of Climate, Soil, and Cultivar on Terroir. American Journal of Enology and Viticulture 55(3):207–17. doi: 10.5344/ajev.2004.55.3.207.

How to cite: Chaffaut, Q., Schmutz, M., and Cavailhes, J.: Impact of drought on the water status of vines in a Bordeaux vineyard, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8126, https://doi.org/10.5194/egusphere-egu23-8126, 2023.

EGU23-9070 | ECS | Posters on site | SSS9.1

Wet grassland biomass yield prediction considering species composition dynamic 

Valeh Khaledi, Gunnar Lischeid, Bahareh Kamali, Ottfried Dietrich, and Claas Nendel

Introduction

Every grassland has considerable annual vegetation composition dynamics, especially in sites with shallow water levels (Toogood & Joyce, 2009). These wet grasslands, where the vegetation is regularly consuming capillary water, are very sensitive to water availability and respond rapidly by changing their species composition. As different species produce different biomass, the biomass yield is constantly altering alongside species composition change (White et al., 2000). These dynamics limit the use of mechanistic models for the prediction of biomass yields, especially in response to the water supply. Grassland models have been developed to simulate vegetation growth since the late 1980s (Coffin & Lauenroth, 1990; Thornley & Verberne, 1989). However, none of the existing models can deal with capillary water ascending from shallow groundwater considering the vegetation composition change. In this study, we demonstrate that mechanistic plant growth models for grassland productivity would benefit from the consideration of vegetation composition change in wet grasslands.

Material and method

The data from an extensively agriculturally used wet grassland lysimeter station in Germany, Spreewald (SPW, 51◦52´ N, 14◦02´ E, 50.5 m above sea level) (Dietrich & Kaiser, 2017) was used in this study. In this study, we followed an analytical approach and a modeling approach to reveal the importance of vegetation composition change impact on biomass yield prediction. First, we did a Pearson correlation analysis between vegetation composition indices and biomass. In the modeling approach, the mechanistic process-based simulation model MONICA (MOdel for NItrogen and Carbon dynamics in Agroecosystems) was employed to simulate water fluxes in the soil. In the model, an empirical approach was used for ascending water in the capillary fringe above the groundwater table, using daily rise rates from the German Soil Survey Manual ("Bodenkundliche Kartieranleitung. ," 2005)

Results

The correlation analysis showed a significant association between the vegetation index and biomass yield, with a time lag of one year between the groundwater level and the respective response in the vegetation index. The results from the modeling approach showed that the model did not reproduce the year-to-year variation in biomass well. However, when we removed the effect of the groundwater level on the vegetation composition from the biomass data, the simulation model agreed much better with the remaining pattern. As a result, we conclude that long-term biomass patterns can only be reproduced with mechanistic simulation models when vegetation composition dynamics are considered, e.g. by using it alongside a species competition model.

Keywords: Wet grassland, vegetation composition, capillary rise, process-based model

Reference

Dietrich, O., & Kaiser, T. (2017). Impact of groundwater regimes on water balance components of a site with a shallow water table [RESEARCH A R T I C L E]. Ecohydrology.

Toogood, S., & Joyce, C. (2009). Effects of raised water levels on wet grassland plant communities. Applied Vegetation Science, 12, 283-294.

White, R., Murray, S., & Rohweder, M. (2000). PILOT ANALYSIS OF GLOBAL ECOSYSTEMS (Grassland Ecosystems).

How to cite: Khaledi, V., Lischeid, G., Kamali, B., Dietrich, O., and Nendel, C.: Wet grassland biomass yield prediction considering species composition dynamic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9070, https://doi.org/10.5194/egusphere-egu23-9070, 2023.

EGU23-11597 | ECS | Posters on site | SSS9.1

Comparison of vegetation indices using measurement techniques on a scale from plant leaves to plots 

Tibor Zsigmond, Imre Zagyva, and Ágota Horel

In agricultural systems, rapid information from data collection and processing is an important factor for stakeholders and researchers to correctly account for the spatial and temporal variability of crop and soil factors. The aim of the present study was to investigate soil-plant-water systems and interactions using manual and remote sensing techniques in a small agricultural catchment. Four land use types of forest, grassland, vineyard, and cropland (sunflower) were investigated in different slope positions. At the same time, three different tillage practices were applied in the vineyard between the rows: grassed (NT), cover cropped (CC), and tilled (T) inter rows. We evaluated NDVI measurements from three different sources (PlantPen - PP, Meter Group - MG, Sentinel-2 - S2) representing different scales (leaves, 0.33m2, and 100m2). We also compared ground and satellite measurements of varying vegetation indices.

Spectral reflectance sensors were used on the slopes of grassland, cropland, and three vineyard sites. The Normalized Difference Vegetation Index (NDVI) and Photochemical Reflectance Index (PRI) sensors were used to measure leaf reflectance. A hemispherical sensor set was used for each measurement. Hand-held instruments were used to measure the topsoil soil water content (SWC) and temperature, leaf NDVI and chlorophyll concentrations, and Leaf Area Index (LAI) every two weeks. Satellite data, such as NDVI, green (GCI) and red edge (RECI) chlorophyll indices, and soil-adjusted vegetation index (SAVI), were obtained from the Sentinel-2 database on days when both ground and satellite overpass occurred within 24 hours.

Land use types and slope position have a strong influence on vegetation growth. The highest overall NDVI and leaf chlorophyll values were observed in vineyard and forest samples, and the lowest in grassland. SWC and temperature were the lowest in the forest and vineyards. SWCs were significantly different for T and CC samples (p<0.05) based on slope positions, while soil temperatures were not significantly different between upper and lower slope positions (p>0.05). For the other three land use types, there were no significant differences in values between slope positions. Chlorophyll data showed a very strong correlation between Sentinel-2 retrieved data and hand-held measurements, with r=0.84 for grassland (GCI), r=0.83 for NT (GCI), and r=0.87 for T (RECI). Strong correlations were found between the different sources of NDVI for the grassland samples (e.g. r=0.97, p<0.05 for S2 and MG). Weaker correlations were observed between different inter-row managed vineyard samples (e.g. for tilled inter-row r=0.70 between S2 and PP and r=0.35 between S2 and MG). Since inter-row management strongly influences the overall values of S2, adjustments are needed.

How to cite: Zsigmond, T., Zagyva, I., and Horel, Á.: Comparison of vegetation indices using measurement techniques on a scale from plant leaves to plots, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11597, https://doi.org/10.5194/egusphere-egu23-11597, 2023.

EGU23-12699 | ECS | Orals | SSS9.1

On the use of seismic geophysical methods to characterize different soil compaction levels 

Alberto Carrera, Mirko Pavoni, Ilaria Barone, Jacopo Boaga, Nicola Dal Ferro, Giorgio Cassiani, and Francesco Morari

To address the non-invasive way of studying soil structure and its dynamics at different scales, several geophysical techniques can complement traditional characterization methodologies. In this context, the most widespread methods for soil investigations rely on the different electrical properties of earth materials which change with the content and salinity of the incorporated fluids. Although the use of seismic methods in soil science studies is not as common as for geotechnical and reservoir characterization, seismic wave fields contain information about the mechanical properties of the subsurface and may offer insights about soil compaction that other geophysical methods cannot provide.

In this work, we evaluate the ability of seismic techniques to assess the differences between small and strong degrees of compaction in soils, relating and validating them with traditional direct measurements. The experiment was conducted at the Experimental Farm “L. Toniolo” of the University of Padova in Legnaro (northeastern Italy), under controlled conditions. The acquisition scheme was designed to resolve small-scale seismic velocity contrasts. Three different levels of induced compaction were investigated with indirect (i.e. geophysics) and direct (i.e. bulk density, texture, volumetric water content) measures.

Preliminary results of refraction and surface waves seismic analysis clearly agree with traditional direct measurements. We demonstrate that this approach is not only sensitive to the compaction phenomenon, but it allows to observe both its lateral and in-depth variability. This study opens up interesting future scenarios for geophysics to highlight the different mechanical responses caused both by soil plastic deformation and soil water distribution due to increasing compaction.

 

How to cite: Carrera, A., Pavoni, M., Barone, I., Boaga, J., Dal Ferro, N., Cassiani, G., and Morari, F.: On the use of seismic geophysical methods to characterize different soil compaction levels, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12699, https://doi.org/10.5194/egusphere-egu23-12699, 2023.

EGU23-13024 | Orals | SSS9.1

Electrical resistivity tomography and sap flow measurements on date palm stems to support irrigation management 

Tarig Bukhary, Johan Alexander Huisman, Haoran Wang, Egon Zimmermann, and Naftali Lazarovitch

The cultivation of date palms (Phoenix dactylifera) is widespread in hyper-arid regions and relies on high-frequency irrigation to achieve satisfactory yields. Adequate irrigation management is of great importance, and requires understanding of the dynamics of sap flow and water storage within the date palm stem. Traditionally, sap flow estimates are obtained using heat dissipation probes. This method provides point estimates that may not represent the spatial distribution of sap flow within the date palm stem. The aim of this study is to investigate whether electrical resistivity tomography (ERT) measurements on date palm stems can be used to obtain information on the spatial distribution of sap flow in order to obtain improved estimates of transpiration. In a first step, laboratory experiments were used to improve understanding of the electrical and hydraulic properties of date palm stems. A laboratory set-up was developed that induced flow in a date palm stem segment using vacuum pressure while making time-lapse ERT measurements. It was found that such ERT monitoring allows to visualize changes in radial flow variability due to different flow conditions. In addition, the electrical conductivity of the outflow was considerably higher than that of the introduced solution, which suggest the presence of stored salt in the stem segment. The relationship between bulk electrical conductivity and water content of date palm stem segments was investigated on smaller samples using multi-step-outflow experiments combined with bulk electrical conductivity measurements. The results showed that the water redistribution in the sample was slow after the initial desaturation, which suggests that the water is tightly bound as in a clay soil. The observed relationship between bulk electrical conductivity and saturation could be described with models established for porous media. In a second step, field experiments were performed that combined ERT and sap flow measurements on both juvenile date palm trees growing in lysimeters and mature date palm trees. For this, a custom-made measurement system was used to acquire high-speed ERT measurements with a temporal resolution of several minutes. The high-resolution monitoring of both the juvenile and mature date palms showed a high spatial variability in electrical conductivity within both the juvenile and mature date palm stems. This has obvious implications for the installation of sap flow sensors, where low-conductivity areas likely indicating regions without flow should be avoided. ERT monitoring also revealed diurnal changes in the spatial distribution of the electrical conductivity that are associated with the tree response to irrigation. An induced drought period for the juvenile date palm in the lysimeter also resulted in a noticeable decrease in the mean electrical conductivity on the second day after irrigation was stopped, suggesting that ERT may also provide an early indicator of water stress.

How to cite: Bukhary, T., Huisman, J. A., Wang, H., Zimmermann, E., and Lazarovitch, N.: Electrical resistivity tomography and sap flow measurements on date palm stems to support irrigation management, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13024, https://doi.org/10.5194/egusphere-egu23-13024, 2023.

EGU23-13502 | ECS | Posters on site | SSS9.1

In-situ effect of Si fertilization on Soil-plant-water relation for different soil erosion states 

MHD Wael Al Hamwi, Mathias Hoffmann, Joerg Schaller, Mathias Stein, Michael Sommer, Shrijana Vaidya, Katja Kramp, Valerie Pusch, Reena Macagga, Gernot Verch, Norbert Bonk, Peter Rakowski, and Maren Dubbert

Crop production is affected by drought duration and severity, which become more frequent with climate change. Several studies reported the positive effect of Silicate (Si) fertilization on soil and plant water balance. However, the relation between soil type and the impact of Silicate (Si) fertilization on plant performance, as well as the underlying mechanism for water stress tolerance, is poorly understood. To investigate the effect of Si fertilization on soil-plant-water relation in different soil types, we set up a Si fertilization experiment in an arable landscape of Northeast Germany (Uckermark region, 53° 23' N, 13° 47' E) using Barley (Hordeum vulgare) at three different sites with different soil types and erosion stages: 1) Haplic luvisol (non-eroded), 2) Haplic Regesol (extremely eroded) and 3) Endogleyic colluvic regosol (deposition). 3 Kg "Aerosil 300"   are applied to the soil (~1% ASi in topsoil) compared to control plots (no fertilization), with four replicates per treatment at each site. A campaign of 2-3 consecutive days was conducted throughout the experiment period (from April to July 2022) every two weeks. During these campaigns, we measured leaf water potential, gas fluxes (CO2 and Evapotranspiration), NDVI (normalized difference vegetation index) and biomass sampling. Soil water content and temperature were continuously monitored by soil sensors planted in situ at each plot. We harvested Barley at the end of the growing season and measured each plot's plant biomass and seed production. Our data showed that Si fertilization significantly increased the soil water content in the different soil erosion stages by 2-3%. At the plant's early growth stage, the increase in the soil water content related to Si fertilization significantly affected drought mitigation, balancing leaf water potential decrease during drought. Moreover, while plant development was not generally affected by Si fertilization, germination was delayed in non-fertilized plots. However, the vegetation period in 2022 was rather wet and a drought occurred only during the early phenological development of the plant, and no significant effects of Si fertilization on plant performance were visible (leaf water potential, net ecosystem exchange, evapotranspiration, NDVI and yield) after the early stages. Thus, no lasting effect of Si fertilization on drought mitigation on Barley could be detected, as Barley recovered quickly from drought during the early vegetation stage, irrespective of Si fertilization. All things considered, Si fertilization as an approach to enhance plant tolerance during drought is more complex than previously expected. Our results suggest that the timing and duration of drought, as well as soil type, are important factors to consider.

Keywords: Si fertilization, Drought, Soil erosion, Water Stress, Soil water content, Leaf water potential, NDVI, Gas fluxes, Plant performance.

How to cite: Al Hamwi, M. W., Hoffmann, M., Schaller, J., Stein, M., Sommer, M., Vaidya, S., Kramp, K., Pusch, V., Macagga, R., Verch, G., Bonk, N., Rakowski, P., and Dubbert, M.: In-situ effect of Si fertilization on Soil-plant-water relation for different soil erosion states, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13502, https://doi.org/10.5194/egusphere-egu23-13502, 2023.

EGU23-14364 | ECS | Posters on site | SSS9.1

Soil phosphorus prediction by visNIR could be dependent on the conversional P determination method 

Tadesse Gashaw Asrat, Stephan M Haefele, Ruben Sakrabani, Kirsty L Hassall, Fassil Kebede, Timo Breure, and Ron Corstanje

Proximal soil spectroscopy can be useful to estimate relevant soil properties in real time and cheaply for agricultural decision support and soil health monitoring. However, prediction performance of plant available soil phosphorus by the visNIR has been unsatisfactory as it is considered among the least spectrally active soil properties. Hence, we compared prediction performance among plant available soil phosphorus (Olsen P), extractable soil phosphorus (ammonium-oxalate extract of P - AmOxP), total soil phosphorus (Aqua regia extract of P - TP) and phosphorus buffer index (PBI) using visNIR soil spectral sensing instrumentations (Neospectra and Fieldspec-4) using East African agricultural soils. The comparison was made by scanning 360 archived soil samples which were collected from 0-20cm soil depth in Ethiopia, Kenya and Tanzania. The spectra data was pre-treated with SavitskyGolay smoothing + first derivative and a PLSR was used to develop the predictive models from a 75% of the dataset (#270) subsampled by a conditioned Latin Hypercubic sampling (cLHS) method using the spectra space. The model performance was evaluated by an independent set of samples (#90) by calculating the concordance correlation coefficient (CCC), ratio of performance to interquartile range (RPIQ), bias and root mean square error of prediction (RMSEP).  The most important wavelengths for all soil P indicators in the NIR instrument ranged between 2150 -2400 nm whereas it included 500-570 nm for the visNIR instrument. PBI was predicted with higher CCC value of 0.94 and 0.89 for visNIR and NIR, respectively, however it has the least RPIQ (0.4 and 0.3, respectively) values when compared to other soil P prediction by both instruments. TP and AmOxP were predicted with higher accuracy and model consistency when compared to OlsenP and PBI. The visNIR range gave better prediction accuracy and model consistency for all soil P indicators than the NIR range. Hence, our findings indicated that TP and AmOxP could be preferred to predict soil phosphorus status for any agricultural and soil health monitoring using soil spectroscopic techniques.

Keywords: proximal soil spectroscopy, PLSR model, Savitzky-Golay smoothing filter, first derivative, Neospectra, Fieldspec-4, East Africa.

How to cite: Asrat, T. G., Haefele, S. M., Sakrabani, R., Hassall, K. L., Kebede, F., Breure, T., and Corstanje, R.: Soil phosphorus prediction by visNIR could be dependent on the conversional P determination method, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14364, https://doi.org/10.5194/egusphere-egu23-14364, 2023.

EGU23-15692 | Posters on site | SSS9.1

UAV-based heterogeneity analysis of soil-plant-water system of small-plot experiment with different oat genotypes under Si and S foliar fertilization treatments 

Erika Budayné Bódi, Erika Kutasy, József Csajbók, Solange Paola Acosta Santamaría, Tamás Magyar, Nikolett Szőllősi, Zsolt Zoltán Fehér, Péter Tamás Nagy, Attila Nagy, and Tamás János

Five winter oat (Avena sativa L.) varieties were set in a small-plot field experiment to examine the abiotic stress considering silicone and sulphur foliar fertilization treatments under temperate and dry climatic conditions in Hungary. Numerous in situ and laboratory measurements were performed to describe the crop's condition at various phenological stages. Drones with multispectral, thermal and LiDAR payloads monitored the field both with high temporal and spatial resolution. A high level of GIS data assimilation was performed in order to handle the different spatial-related parameters in one interface.

It is a multi-purpose experiment, and for all of them it is an important criterion whether the study was carried out in a truly homogeneous area. Practically, it means that we ignore the patterns of the crop or the soil. If this is not the case, the various parameters measured should be evaluated accordingly. Hence, our study's main goal here is to reveal the soil and crop heterogeneity level. For this, all the measured parameters are involved in the multi-parameter analysis by which the heterogeneity level of the site can be assessed.

Practically, by this, we can answer the main question: is the field suitable to carry out analysis such as abiotic stress studies or yield prediction modelling on it or shall we handle certain parts differently?

Based on the example of our experiment we design a workflow by which the heterogeneity level of a small-plot field can be assessed and provide a solution for how to handle it in order not to involve data which may mislead analysis.

How to cite: Budayné Bódi, E., Kutasy, E., Csajbók, J., Acosta Santamaría, S. P., Magyar, T., Szőllősi, N., Fehér, Z. Z., Nagy, P. T., Nagy, A., and János, T.: UAV-based heterogeneity analysis of soil-plant-water system of small-plot experiment with different oat genotypes under Si and S foliar fertilization treatments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15692, https://doi.org/10.5194/egusphere-egu23-15692, 2023.

EGU23-16030 | Orals | SSS9.1

Geophysics for managing Norwegian agrohydrological threats 

Esther Bloem, Robert Barneveld, Dominika Krzeminska, and Jannes Stolte

Norwegian agriculture is challenged by increased production demand and climate change while being faced with tight restrictions to its environmental impact. Due to climate change, an increase in extreme weather events is expected. High intensity rainfall events lead to flooding and water-logged conditions, which have negative impacts on yield and operational conditions related to tillage and transport (trafficability of the soil). Two thirds of Norway's agricultural area is drained to prevent water logging, but at times these drained soils have problems with too high water content, leading to delayed tillage in spring time resulting in lower yields. About 10% of the cultivated land is considered poorly drained.

Saturation and infiltration excess overland flow leads to sheet erosion. Erosion rates often follow a seasonal pattern with the highest soil losses during late autumn and early spring. For most of the total soil loss only a few runoff events are responsible each year. Soil loss from agricultural areas in Norway is not only harmful because of the loss of nutrient rich topsoil, but also because of off-site effects, especially in freshwater systems.

Poorly drained soils are prone to deterioration of its structure. In areas where overland flow concentrates, this may lead to the development of gullies. Ephemeral gullies make up a considerable part of the sediment losses from agricultural areas. In addition, they are shortcuts for sediment transport, forming a connection between the hillslope and the surface water system.

Seasonal saturation excess because of snow melt and rain also leads to high flow rates in Norway’s stream and river network. Flooding problems at the intersection between streams and roads occur even in first order streams.

While many soil conservation and water retention measures complement each other, they sometimes affect each other adversely. Intensification of tile drainage, for example, may reduce sheet and gully erosion risk levels, but will have an adverse effect on peak flow rates and flood risk. Other measures, like buffer zones, serve both purposes. But when, how and under which circumstances water retention and soil conservation measures function remains a complex question.

Understanding the spatio-temporal dynamics of water in the vadose and groundwater zones therefore is a key component of integrated agro-ecological management strategy at low (farm) and high (regional) levels. While the mechanics of overland water movement and infiltration are generally well understood, there are many significant challenges for system understanding at larger spatial scales, especially under increasingly non-normal weather conditions.

NIBIO endeavors to reconcile measurements and observations with agrohydrological system understanding. Complexity and scale (time and space) are the main challenges in this endeavor. In this presentation we will present how NIBIO uses geophysics for understanding agrohydrological threats and solutions, with focus on drainage, erosion and buffer zones.

How to cite: Bloem, E., Barneveld, R., Krzeminska, D., and Stolte, J.: Geophysics for managing Norwegian agrohydrological threats, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16030, https://doi.org/10.5194/egusphere-egu23-16030, 2023.

To improve the efficiency of irrigation water application it is necessary to understand 3 important aspects. The depth of wetting reached by each irrigation episode, the overlap between irrigation emitters and the depth where the largest root volume is found. The joint use of electrical resistivity tomography (ERT) with mechanistic hydrological model allows establishing an appropriate irrigation schedule for the particular condition of each irrigation sector, considering aspects for intra-farm soil variability and variations in the root volume of the orchard. For a correct characterization of the existing soil variability in a field, we propose the use of high-resolution ERT (several measurements per hectare) and clustering using k-means for the definition of sites of interest where it is necessary to obtain a petrophysical relationship. (Waxman & Smits, 1968) that allows obtaining the moisture content of the soil from the electrical resistivity of the soil. For the calibration of the mechanistic hydrological model in these same sites, the use of disk infiltrometers measurements is proposed. Through time-lapse ERT measurements in periods between irrigation, it is possible to observe areas of greater water absorption and define areas where there is a greater root volume. Through time-lapse ERT measurements in irrigation episodes, it is possible to determine the depth of wetting reached and use this information to calibrate model parameters of the mechanistic hydrological model. Finally, the use of computer simulations in the defined clusters makes it possible to establish irrigation times and frequencies that ensure a correct overlap between emitters and a wetting depth that reaches the areas of greatest water absorption.

How to cite: Cabrera, D., Faundez, C., and Diaz, P.: The use of high resolution electrical resistivity tomography (ERT) and mechanistic hydrological models to increase the efficiency of the wáter applied by irrigation., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16173, https://doi.org/10.5194/egusphere-egu23-16173, 2023.

EGU23-17083 | Orals | SSS9.1

Determination of upward/downward soil water fluxes using soil thermal profile series : two field case studies 

Sailhac Pascal, Harrouet Titouan, Rivière Agnès, Maugis Pascal, Léger Emmanuel, and Zeyen Hermann

Water transfer through the unsaturated zone, in terms of upward or downward water fluxes, is a critical term for estimation of the water budget. As fluid flow modifies diffusive heat transfer through advective processes, since the early 90s several studies have attempted to deduce vertical water flow from soil temperature series. Likewise, if information on the water content profiles is known, bulk thermal properties can be inferred from thermal time series at different depths.

In this study we compare two field sites in the Paris Basin Area, with two different types of soil and vegetation. We present our preliminary results from two approaches aiming at retrieving inferring soil bulk thermal parameters, namely heat capacity and conductivity, as well as vertical water flow.

On the one hand, thermal measurements until a depth of 1.8 m have been carried out in a managed crop field. Using frequency decomposition of the thermal series, the upward and downward flows are determined. The water fluxes are compared with high-frequency EM time-lapse maps in an attempt to spatialize the variations.

On the other hand, the thermal properties of a wetland area are inferred from soil thermal time series inversion using the thermo-hydrodynamic code suite Ginette, and are compared with spatial distribution of vegetation derived from remote sensing imagery.

The two approaches are compared and discussed with their respective caveats and abilities.

How to cite: Pascal, S., Titouan, H., Agnès, R., Pascal, M., Emmanuel, L., and Hermann, Z.: Determination of upward/downward soil water fluxes using soil thermal profile series : two field case studies, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17083, https://doi.org/10.5194/egusphere-egu23-17083, 2023.

BG3 – Terrestrial Biogeosciences

EGU23-1310 | ECS | Orals | BG3.1 | Highlight

The evidence and global extent of alternative stable states in forest leaf phenology 

Yibiao Zou, Constantin Zohner, Colin Averill, Haozhi Ma, Julian Merder, Miguel Berdugo, Lalasia Bialic-Murphy, Lidong Mo, and Thomas Crowther

Whether forests are composed of evergreen or deciduous species largely affects biogeochemical cycles and the functioning, structure and biodiversity of ecosystems. These leaf phenology types may be self-promoted through positive plant-soil feedbacks, which may shift the distribution of forest types towards alternative stable states. However, we still lack empirical evidence of phenological alternative stable states and a spatial understanding of where they might be present. Here, we test the presence of alternative stable states using forest inventory data at the continental (North America and Europe) and global scale. We show that the distribution of forest leaf phenology types is bimodal, and demonstrate the presence of positive feedbacks in recruitment, growth and mortality. Data-driven simulations show that the observed positive feedbacks are sufficient and necessary to produce the alternative stable states, which also lead to hysteresis during ecosystem transition. Spatial random forest models further reveal hotspots of alternative stable states in evergreen-deciduous ecotones and the poleward range limit of forests, which appear largely driven by soil feedbacks. Given the close connection between forest leaf phenology and ecosystem biogeochemical processes, our insights on evergreen vs. deciduous alternative stable states inform our understanding of the distribution of forest biomes, allowing more accurate quantification of carbon turnover and terrestrial climate feedbacks.

How to cite: Zou, Y., Zohner, C., Averill, C., Ma, H., Merder, J., Berdugo, M., Bialic-Murphy, L., Mo, L., and Crowther, T.: The evidence and global extent of alternative stable states in forest leaf phenology, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1310, https://doi.org/10.5194/egusphere-egu23-1310, 2023.

EGU23-1469 | ECS | Orals | BG3.1

Field and satellite-estimated seasonal ground vegetation patterns in boreal ecosystems 

Yuwen Pang, Aleksi Räsänen, Teemu Juselius, Mika Aurela, Sari Juutinen, Minna Väliranta, and Tarmo Virtanen

Boreal ecosystems, in particular peatlands, are one of the most essential terrestrial carbon pools. Aboveground biomass (AGB) and leaf area index (LAI) are key plant traits widely used to characterise their ecosystem processes. However, it has remained poorly understood how these variables develop over seasons among different vegetation types (VTs) and plant functional types (PFTs), and how well their seasonal spatiotemporal patterns can be detected by satellite images.

To address these gaps, we carried out field measurements between May and September during one growing season to investigate the seasonal development of ground vegetation AGB and LAI in seven VTs and PFTs within three peatland and forest study areas in northern Finland. We linked field-based AGB and LAI estimations to Sentinel-2 (S2) multi-temporal images via Random Forest (RF) regressions, yielding seasonal AGB and LAI maps.

Although AGB and LAI followed a clear unimodal curve in most VTs, their seasonal trajectories were more stable in forests and fen lawns than in fen strings and flarks. AGB peaked around the first week of August in about 900 DD5 (the sum of degree days above 5 °C), and, in most cases, one to two week(s) later than LAI. Besides evergreen shrubs, other three vascular PFTs presented clear unimodal seasonal patterns in AGB and LAI, while the AGB of mosses remained steady over the season. When upscaling to the landscape-level, the R2 of regressions was 24.2-50.2% (RMSE: 78.8-198.7 g*m-2) for AGB and 48.5-56.1% (RMSE: 0.207-0.497 m2*m-2) for LAI. The S2-estimated AGB and LAI had unimodal seasonal patterns, though peaking dates were one to three week(s) earlier than in the corresponding field-based estimates.

Our findings suggest that S2 data which has relatively high spatial and temporal resolution has potential to monitor ground vegetation seasonality in boreal landscapes, especially in areas with sparse or no tree cover.

How to cite: Pang, Y., Räsänen, A., Juselius, T., Aurela, M., Juutinen, S., Väliranta, M., and Virtanen, T.: Field and satellite-estimated seasonal ground vegetation patterns in boreal ecosystems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1469, https://doi.org/10.5194/egusphere-egu23-1469, 2023.

EGU23-2415 | ECS | Orals | BG3.1 | Highlight

Citizen science observations capture global patterns of plant traits 

Sophie Wolf, Miguel Mahecha, Francesco Maria Sabatini, Christian Wirth, Helge Bruelheide, Jens Kattge, Álvaro Moreno Martínez, Karin Mora, and Teja Kattenborn

As global change accelerates, the urgency for a solid understanding of biosphere-environment interactions grows. However, we need more data on plant functional traits to test such relationships reliably across ecosystems. The TRY database contains an impressive collection of plant trait measurements for thousands of species already, and there have been some approaches to spatially extrapolate them using geospatial predictors and remote sensing data; however, the original data is spatially sparse so that extrapolations come with substantial uncertainties. At the same time, citizen scientists have collected increasingly dense observations of species occurrences around the globe. Here, we test if we can link species occurrences from the citizen science project iNaturalist with trait observations from TRY to produce global trait maps without the need for spatial extrapolation. We generated spatial grids for 18 traits, calculating a mean for each grid cell by averaging trait values associated with observations within that cell. We compared mean trait values from iNaturalist observations to community-weighted mean traits from sPlotOpen, a globally sampled dataset of vegetation plot data. 

Our results show correlations between the two datasets of up to r = 0.69, especially in biomes with higher iNaturalist observation density and those not dominated by trees. Also, we show that iNaturalist-derived maps have higher correlations to sPlotOpen-derived maps than previously published trait maps. This strong correlation between two fundamentally different datasets is astounding and unexpected. iNaturalist is noisy and heterogenous, sampled by citizen scientists who share the species they encounter and find interesting; sPlotOpen is a data collection of vegetation plots that were measured and recorded within the framework of specific research questions. The fact that these two datasets exhibit such a strong resemblance opens up a promising avenue for using the data treasure trove that is crowd-sourced data to help fill the gaps in plant trait data and demonstrates that crowd-sourced data, such as the iNaturalist observations, can be used to complement professional data collection efforts.

How to cite: Wolf, S., Mahecha, M., Sabatini, F. M., Wirth, C., Bruelheide, H., Kattge, J., Moreno Martínez, Á., Mora, K., and Kattenborn, T.: Citizen science observations capture global patterns of plant traits, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2415, https://doi.org/10.5194/egusphere-egu23-2415, 2023.

EGU23-2530 | ECS | Orals | BG3.1

An open-field multifactor experiment to simulate extreme climate events for observation of soils and plants 

Gwang-Jung Kim, Heejae Jo, Min Seok Cho, Nam Jin Noh, Seung Hyun Han, and Yowhan Son

Extreme climate events, generally defined as inordinately hotter, drier, or wetter compared to the historical period, are showing an increasing trend in terms of their frequency, intensity, and magnitude. They can impair the recovery system of plants, and thus, there is a need to understand their effects on plants. Here, we constructed a temperature and precipitation manipulation system to simulate extreme climate events for plants in the open field in April, 2020. We applied a factorial combination of three temperature levels (control, +3 °C, and +6 °C) and three precipitation levels (control, drought, and heavy rainfall) with six replicates (i.e., 54 plots of 1.5 m × 1.0 m) from April to June, 2020. Infrared heaters were adopted for simulating extreme heat since they are able to provide a realistic heating mechanism. The targeted temperature was automatically maintained by the data loggers and relays. For the extreme drought simulation, automatic rainout shelters intercepted ambient rainfall, closing only when detecting rainfall to avoid a disturbance of light absorption and passive warming. The rainfall simulator sprayed water from a height of 1.6 m above the ground using spraying nozzles and, the spraying time and pressure were set by the hooked-up pump and control panel to generate realistic rainfall. An infrared thermometer and a soil moisture and temperature sensor per plot measured the soil surface temperature and soil water content, respectively. As a result, the infrared heaters increased the mean soil surface temperature (°C ± standard error) by 2.7 ± 0.2 and 5.7 ± 0.5 in the +3 °C and +6 °C plots, respectively, compared to that in the control. The rainout shelter and rainfall simulator successfully produced extreme drought and heavy rainfall conditions, showing higher mean soil water contents (vol. %) of 4.44 ± 0.01 in the drought plots and 8.45 ± 0.03 in the heavy rainfall plots than that in the control (7.19 ± 0.03). Our multifactor manipulation system can provide a mechanistic understanding of the combined extreme stresses on soils and plants (e.g., soil microbial activity, seed germination, and growth of seedlings) through the comparison between the impact of single and multiple factors. Furthermore, the system has the advantage of applying diverse intensities of extreme climate events without restrictions on regions and scenarios by altering the settings of data loggers or the control panel. The system in this study can aid in investigating and modeling the mechanisms between extreme climate events, and soils and plants.

Acknowledgment: This study was carried out with the support of the National Research Foundation, Republic of Korea (Project No. 2022R1A2C1011309) and Korea Forest Service (Project No. 2020181A00-2222-BB01).

How to cite: Kim, G.-J., Jo, H., Cho, M. S., Noh, N. J., Han, S. H., and Son, Y.: An open-field multifactor experiment to simulate extreme climate events for observation of soils and plants, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2530, https://doi.org/10.5194/egusphere-egu23-2530, 2023.

Leaf angle distribution (LAD) is an important plant structural trait that determines radiation interception, biomass production, rainfall interception, and evapotranspiration. Assessment of LAD is a challenging task and a significant source of uncertainty in ecological models. So far, the information on leaf inclination angle distributions of different plant species is scarce in literature and databases (e.g. TRY). Approximate quantification of LAD is often made by means of modeling.

The aim of this study is to find a user-friendly and accessible method to estimate leaf angle distribution type. We used Google’s TensorFlow convolutional neural network (CNN) to test for the first time the possibility of using machine learning for automatically classifying LAD types from leveled digital photographs. We used different combinations of five LAD distribution types (planophile, erectophile, spherical, plagiophile and uniform). The highest training accuracy of 95% and validation accuracy of 91% were achieved by using the two most distinct leaf angle distribution types – planophile and erectophile. As expected, the accuracy subsequently decreased with the addition of other leaf angle distribution types (spherical, plagiophile, uniform). However, our results indicate that the involvement of machine learning may indeed hold the potential to remove the current bottleneck in retrieving the information on leaf angle distribution and its better quantification in ecosystem modeling.

How to cite: Aun, M. and Pisek, J.: Exploring the potential of machine learning for leaf angle distribution estimation from leveled digital photography, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3783, https://doi.org/10.5194/egusphere-egu23-3783, 2023.

EGU23-4831 | ECS | Posters virtual | BG3.1

Encroaching Mongolian oak aggravates nitrogen limitation in southern Asian boreal forest 

Yang Tang and Enzai Du

Mitigation of temperate broadleaved trees into southern boreal forest has occurred in response to rapid climatic warming, consequently resulting in profound changes in species composition and ecosystem functions of southern boreal forest. However, the biogeochemical effect of migrating temperate trees on boreal forest trees remains poorly understood. Here we performed a 52-sites survey along the temperate-boreal forest ecotones in Northeastern China to uncover that the encroaching Mongolian oak, dominant trees in temperate forest, has affected N nutrition of Dahurian larch, the dominant trees of regional boreal forest. Specifically, we tested following hypotheses: (i) encroaching Mongolian oak affects N availability for Dahurian larch via modifying soil N availability; (ii) Mongolian oak directly affects N dynamic of Dahurian larch via competing for available N against Dahurian larch. Our results show that the foliar 15N is significantly lower in Mongolian oak than in co-occurring Dahurian larch. Soil 15N is negatively correlated with soil C:N ratio and stand slope but is not affected by the encroachment of Mongolian oak. Both foliar 15N abundance and difference (δ15Nfoliage15Nsoil) of Dahurian larch are significantly affected by the dominance of Mongolian oak, suggesting that encroaching Mongolian oak aggravates N limitation of boreal Dahurian larch. Our findings highlight an unexpected biogeochemical effect of migrating temperate trees on boreal forest.

How to cite: Tang, Y. and Du, E.: Encroaching Mongolian oak aggravates nitrogen limitation in southern Asian boreal forest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4831, https://doi.org/10.5194/egusphere-egu23-4831, 2023.

EGU23-5362 | Posters on site | BG3.1

Impact of evolutionary populations on soil organic matter characteristics 

Cornelia Rumpel, Charlotte Vedere, Giovanna Visioli, Laura Gazza, and Gianni Galaverna

In Mediterranean areas, agricultural systems have to adapt to an environment presenting few water resources with severe drought events, which are expected to increase in frequency and intensity due to global warming. Therefore, these regions are particularly exposed to climate change and need to implement solutions in order to maintain food production.           
Our objective is to assess the benefits of innovative cropping systems capable to face these constraints. Evolutionary population are mixtures of plants of the same species presenting a high degree of crop genetic diversity needing lower inputs while allowing higher buffering capacities to adapt environmental stress like water shortage. In this study, we investigated the influence that these plants can have on organic matter quality and dynamics and hypothesised that the abilities of the crop to face drought can participate at increasing soil carbon storage in soil.     
We conducted a field experiment with five different evolutionary populations of wheat, i.e. a bread wheat (Monnalisa), an einkorn wheat (Norberto) and 2 evolutionary populations (Furat-Li Rosi, Furat-Floriddia and BIO2), cultivated following four other plants species (Wheat, Pea, Cickpea or Clover) on two different sites in Italy presenting contrasted conditions (hot-summer Mediterranean climate in Roma and humid subtropical climate in Parma). Bulk soil and rhizosphere soils were sampled and C, N contents as well as organic matter functional groups using Mid Infrared Spectroscopy (MIRS) were assessed.  
We observed that the infrared signatures differed between our two sites and depending on the previous cropping species. Evolutionary population of wheat showed different signatures than durum and bread wheat. Our results demonstrate that evolutionary population in particular pedoclimatic conditions can influence the fate of soil organic matter.

How to cite: Rumpel, C., Vedere, C., Visioli, G., Gazza, L., and Galaverna, G.: Impact of evolutionary populations on soil organic matter characteristics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5362, https://doi.org/10.5194/egusphere-egu23-5362, 2023.

EGU23-6385 | ECS | Orals | BG3.1

Investigating the spatial and temporal variation of plants traits across flux sites using a trait-based dynamic vegetation model 

Dushyant Kumar, Simon Scheiter, Liam Langan, Sujan Koirala, Mirjam Pfeiffer, Carola Martens, Ulrich Weber, and Nuno Carvalhais

The study of plant trait variability is critical for understanding ecosystem dynamics and predicting the response of vegetation to varying climatic conditions. Understanding the factors controlling the spatial and temporal variability in vegetation traits is key for addressing the ecosystem responses and feedbacks to changes in climate. In this study, we used the adaptive dynamic global vegetation model version 2 (aDGVM2) to simulate the temporal evolution and spatial distribution of plant traits across a wide range in edapho-climatic conditions. For such, we select locations of existing different ecosystem types and where in situ meteorological and eddy covariance flux measurements are taken.

We forced the aDGVM2 with FAO soil and flux site climate data, extended until 2020 and gap-filled with ERA5 data. To ensure that the simulated vegetation had sufficient time to adapt to prevailing local environmental conditions we conducted simulations for 500 years, split into a 400-year spin-up phase and a 100-year transient phase. For the spin-up phase, we randomly sampled years of the first 30 years of daily climate. Stochasticity in the selection-driven assembly of plant communities within the model can lead to multiple potential state; therefore, 10 replicate runs were conducted for each site with same model configuration.

We examine the differences in the 25 simulated trait values across sites, replicates and time via an analysis of variance (ANOVA). The analysis shows significant differences in trait values between sites, with some traits showing higher variability than others. In particular, we find that traits related to plant structural support (height, stem counts) were highly variable across sites, while traits related to resource acquisition (e.g., specific leaf area, leaf nitrogen content) are more stable. These results provide important insights into the factors that influence trait variability in space, and will be valuable for predicting the response of terrestrial ecosystems to environmental change. Further understanding the factors driving trait variability is of essential value in the design of mitigation and adaptation strategies and guide conservation efforts in the face of a rapidly changing world.

How to cite: Kumar, D., Scheiter, S., Langan, L., Koirala, S., Pfeiffer, M., Martens, C., Weber, U., and Carvalhais, N.: Investigating the spatial and temporal variation of plants traits across flux sites using a trait-based dynamic vegetation model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6385, https://doi.org/10.5194/egusphere-egu23-6385, 2023.

EGU23-6596 | Posters on site | BG3.1

The atmosphere as an inoculator of a functional phyllosphere microbiota 

Frédéric Mathonat, Anne-Catherine Lehours, Antoine Vergne, Barbara Ervens, and Pierre Amato

The aerial parts of plants constituting the phyllosphere are in constant interaction with the atmosphere and the microorganisms it transports. Some plants have specialized structures that allow them to collect rainwater, the phytotelms. Dipsacus fullonum is a pioneer plant found in the Auvergne region of France that forms water reservoirs around its stem, called phytotelms. Rainfall feeds these reservoirs with water and inoculate them with a particular microbiota, including a high population of anoxygenic phototrophic bacteria (APB), i.e. bacteria capable of utilizing light to generate energy, without fixing carbon dioxide and releasing oxygen. These bacteria often have an impressive capacity to fix atmospheric nitrogen, which is likely beneficial to the plant, which stimulates their development through specialized molecules and structures found inside the phytotelms: glandular hairs. A high concentration of bacteriochlorophyll, a photosynthetic pigment typical of APBs, has been identified by HPLC in reservoir’s water. The pufM gene coding for the small subunit of the photosynthetic reaction centre of APBs was detected by PCR in DNA extracted from phytotelm water, and it was also found prevalent in cloud and rain water samples. Living APB strains were also cultured and isolated from cloud water samples. The prevalence of these bacteria in the atmosphere suggests that anoxygenic photosynthesis could represent a strong selective advantage for survival, and so for long distance microbial dispersion. These bacteria could participate to the fixation of nitrogen in clouds and wet aerosols, and contribute to the biogeochemical cycle of nitrogen by reducing atmospheric N2 into NH3/NH4+ to an unsuspected extent globally.

How to cite: Mathonat, F., Lehours, A.-C., Vergne, A., Ervens, B., and Amato, P.: The atmosphere as an inoculator of a functional phyllosphere microbiota, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6596, https://doi.org/10.5194/egusphere-egu23-6596, 2023.

EGU23-6949 | ECS | Posters on site | BG3.1

The temperature effect on the Intrinsic quantum yield at the ecosystem level 

David Sandoval, Victor Flo, Catherine Morfopoulos, and Iain Colin Prentice

The intrinsic quantum yield (φ0) is a measure of the efficiency of photosynthesis at low light levels and it is a crucial parameter for modelling gross primary productivity using “light use efficiency” (LUE) models. These models often assume that φ0 is constant, but there is evidence retrieved at leaf level in the lab, that it may depend on temperature in a bell-shaped curve, with a peak around 30°C. This temperature dependence of φ0(T) is still not fully understood, thus, it is still unknown if the shape of φ0(T) is universal or if the responses at the leaf and ecosystem levels widely differ. Here we derived φ0(T) at the ecosystem level for different sites during their growing season. We used sub-daily above and below-canopy measurements of photosynthetic flux density, long-wave radiation measurements to derive surface canopy temperature, and eddy covariance measurements of CO2 exchange. We then compared our estimations with empirical models found in the literature and propose a new empirical equation. We found that φ0(T) at the ecosystem level also follows a bell-shaped curve, with a rapid increase after 5 °C to peak around 20 °C to 25 °C, and a slight decrease with further increasing temperature. Overall, our estimations show lower values than previous leaf-level observations reported in the literature.  The results suggest that this new formulation for φ0(T) may improve the predictions of current LUE models, but further testing is needed.

How to cite: Sandoval, D., Flo, V., Morfopoulos, C., and Prentice, I. C.: The temperature effect on the Intrinsic quantum yield at the ecosystem level, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6949, https://doi.org/10.5194/egusphere-egu23-6949, 2023.

EGU23-7428 | ECS | Orals | BG3.1 | Highlight

Global patterns of plant functional traits and their relationships to climate 

Jiaze Li and Iain Colin Prentice

Plant functional traits (FTs) determine the survival strategies of plants and their adaptations to the environment, which affect the structure and productivity of vegetation. However, global patterns of many FTs remain uncertain. Currently available global maps of FTs generated by different upscaling approaches show considerable divergence. Potentially different trait responses could be induced by climate change in herbaceous, evergreen and deciduous taxa. Better understanding of these variations should improve our ability to predict global trait patterns and the consequences of global environmental change for vegetation.

We compiled a global data set for 18 FTs, including 42,676 species from 89,478 natural vegetation plots. All FTs in the data set have community-weighted mean values for each plot; seven also have species-mean values. We grouped the species into non-woody, woody deciduous and woody evergreen categories according to their life form and leaf phenology. Then we calculated community-weighted mean values of the seven FTs having species-mean records for the three plant groups. We selected three bioclimatic variables: a moisture index (MI, representing plant-available moisture), mean temperature of the coldest month (MTCO, representing winter cold), and mean growing season temperature (MGST, representing summer warmth) to create a three-dimensional global climate space and define global climate classes. Principal Component Analysis (PCA) was used to estimate the main functional continua on which FTs converge for each plant group. Redundancy Analysis (RDA) was used to describe the extent to which variation in trait combinations can be explained by bioclimatic variables. Correlations between each trait and bioclimatic variables for the three plant groups were described by Generalized Additive Models (GAMs). We used the GAMs to visualise the trait distribution in global climate space for all seven FTs, group by group. We finally fitted new comprehensive GAMs considering bioclimatic variables and remotely-sensed global cover of the three plant groups in order to predict global patterns for all 18 FTs at 0.1° spatial resolution.

Bioclimatic variables explain more trait variance for woody than non-woody plants. Two trait combinations are common to all plant groups: one is plant height (H) – diaspore mass (DM), positively associated with seasonal temperatures; the other is leaf mass per unit area (LMA) – leaf nitrogen content per unit area (Narea), decreasing with moisture availability. Stem specific density (SSD) of non-woody plants is correlated with the LMA–Narea axis, but SSD of woody evergreen plants is correlated with the H–DM axis. For woody deciduous plants, SSD is correlated with leaf nitrogen content per unit mass (Nmass). Leaf area (LA) is positively correlated with all bioclimatic variables and shows variation in all plant groups that is independent of other traits. FTs within the same trait combination tend to present similar patterns in the global climate space. GAMs based on bioclimatic variables and vegetation cover explain up to three-quarters (on average about a half) of global trait variation.

Our study reveals universal relationships among traits and between traits and climates, highlights certain key differences between within non-woody, woody deciduous and woody evergreen taxa, and produces high-resolution global maps for plant functional traits.

How to cite: Li, J. and Prentice, I. C.: Global patterns of plant functional traits and their relationships to climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7428, https://doi.org/10.5194/egusphere-egu23-7428, 2023.

EGU23-8794 | ECS | Orals | BG3.1

Global patterns of tree wood density 

Hui Yang, Vitus Benson, Yahai Zhang, Rackhun Son, Siyuan Wang, Weijie Zhang, Yuzhen Zhang, Claire Robin, Dmitry Schepaschenko, Zbigniew Karaszewski, Sterenczak Krzysztof, Álvaro Moreno-Martínez, Cristina Nabais, Thomas Ibanez, Ghislain Vieilledent, Ulrich Weber, and Nuno Carvalhais

Wood density is an emergent property resultant of tree growth strategies modulated by local edapho-climatic and stand development conditions. It is associated with the biomechanical support of trees and hydraulic conductivity or safety, directly and indirectly influencing a range of ecological processes, including, among others, tree growth, tree resistance to disturbances, and mortality. Tree wood density is also crucial for assessing vegetation carbon stocks by supporting the link between a volumetric retrieval and a mass estimate. Earlier studies based on tree-level wood density measurements have reported significant relationships between wood density, environmental conditions, and tree growth strategies. However, these were either regionally focused or suffering from data availability, lacking a representative large-scale and spatially explicit representation of factors influencing tree wood density. This study collects and collates information from several sources to construct a global database of 28,822 tree-level wood density measurements alongside with a wide set of climate, soils, topography, and Earth observation covariates to support the development of statistical models for wood density. The dataset, consisting of more than 3,000 global covariates, is used for training different machine learning models, including random forest model (RF), light gradient boosting model (LGBM), extreme gradient boosting model (XGBoost), and bagged trees models. The experimental design considers six cross-validation approaches: either random 5-fold; according to two sets of climate classifications, land cover types, ecozones, or latitudinal ranges. Model performances are assessed with the coefficient of determination (R2) and Root-mean-square errors (RMSE) when predicting an independent test subset of wood density. The top ten models show a prominent performance (R2 > 0.67 and RMSE < 0.09), and their ensemble mean, and standard deviation are considered the best estimation and uncertainty in wood density predictions, respectively. Systematic underestimation biases are observed around the low northern latitudes (0º-20ºN), primarily due to the lack of wood density measurements. Further analysis of sources of uncertainties and their quantification support the generation of a global quantitative and spatially explicit representation of wood density. The ecological interpretation and quantitative assessment of global wood density, and associated uncertainties aim to contribute to improving predictions of vegetation biomass and inferring ecosystem resistance under current and future climate scenarios.

How to cite: Yang, H., Benson, V., Zhang, Y., Son, R., Wang, S., Zhang, W., Zhang, Y., Robin, C., Schepaschenko, D., Karaszewski, Z., Krzysztof, S., Moreno-Martínez, Á., Nabais, C., Ibanez, T., Vieilledent, G., Weber, U., and Carvalhais, N.: Global patterns of tree wood density, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8794, https://doi.org/10.5194/egusphere-egu23-8794, 2023.

EGU23-8897 | ECS | Orals | BG3.1

Nitrogen reallocation during alpine plant senescence contributed to plant nutrient conservation and ecosystem nitrogen retention 

Qingzhou Zhao, Gabriel Smith, Peng Wang, Lingyan Hu, Miaojun Ma, Colin Averill, Thomas Crowther, and Shuijin Hu

To conserve limiting nitrogen (N) in alpine ecosystems, herbaceous plants resorb and reallocate N from senescing tissues. However, the extent of N resorption and reallocation in aboveground tissues, coarse roots, fine roots and their relative contributions to whole-plant N conservation and ecosystem N retention remain poorly understood. Utilizing N stable isotope (15N) as a tracer, we quantified N partitions and N retranslocation efficiencies (NRE, % of N changes for each N pool) during senescence among different plant organs in a Tibetan alpine system. We found that compared to the N pools at the peak biomass stage, substantial 15N infine roots (FR, 39.93%) and aboveground tissues (shoot, 50.94%) was retranslocated primarily to coarse roots (CR, an increase of 79.02% in 15N) and non-extractable soil organic matter (an increase of 37.39% in 15N), corresponding to a temporal shift of plant trait syndrome from poor conservation to strong conservation during senescence. 15N in particulate organic matter and mineral-associated organic matter fractions during the senescence stage increased by 29.80% and 24.30%, respectively, but microbial biomass 15N significantly decreased. Our results illustrate the key role of N retranslocation to coarse roots and organic matter in N retention and the dual role of plant roots and organic matter as N sink and source in the plant-microbe-soil system. These findings suggest that plant N retranslocation and seasonal trait alternation facilitate the spatial and temporal coupling between plant N demand and bioavailable N supply in N-limiting alpine systems.

 

How to cite: Zhao, Q., Smith, G., Wang, P., Hu, L., Ma, M., Averill, C., Crowther, T., and Hu, S.: Nitrogen reallocation during alpine plant senescence contributed to plant nutrient conservation and ecosystem nitrogen retention, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8897, https://doi.org/10.5194/egusphere-egu23-8897, 2023.

EGU23-9142 | Orals | BG3.1

Simulating the success of plant hydraulic strategies within a global vegetation model 

Thomas A. M. Pugh, Annemarie Eckes-Shephard, Daijun Liu, Adriane Esquivel-Muelbert, Thomas Matthews, Phillip Papastefanou, Anja Rammig, and Jonathan Sadler

Today’s forest carbon stocks are threatened by climate change through many types of disturbances, including drought. State-of-the-art Dynamic Global Vegetation Models (DGVMs) have hitherto not been able to explicitly simulate the response of tree hydraulic systems to drought, which are ultimately important determinants of tree resilience during drought events. Increasingly, more detailed representations of plant hydraulics, including death by cavitation, are being included in DGVMs, but simulations at the global level have been challenging, partially due to the lack of data for parameterisation. To overcome these issues, we compiled a large dataset of hydraulics-relevant plant traits from the literature (including TRY). To overcome the sparseness of the available trait data, we used literature on the functional relationships between traits to create a hypothesis framework that functionally links multiple traits and their trade-offs together in a network. From this network of traits we can sample parameter sets that reflect coherent plant strategies. We applied these strategies in the plant-hydraulics-enabled DGVM LPJ-GUESS and show how they can be used to provide model-based hypotheses of how both strategies and individual trait values vary across different forest environments. These results provide a basis for global-scale hydraulic model parameterisation, as well as providing verifiable hypotheses for testing in the field. 

How to cite: Pugh, T. A. M., Eckes-Shephard, A., Liu, D., Esquivel-Muelbert, A., Matthews, T., Papastefanou, P., Rammig, A., and Sadler, J.: Simulating the success of plant hydraulic strategies within a global vegetation model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9142, https://doi.org/10.5194/egusphere-egu23-9142, 2023.

EGU23-9264 | ECS | Posters on site | BG3.1

Functional traits associated with multiple abiotic stress tolerance strategies in woody plants of the Northern Hemisphere 

Nicola Pavanetto, Carlos P. Carmona, Ülo Niinemets, Lauri Laanisto, and Giacomo Puglielli

Climate change is altering abiotic stress regimes, and thus woody plants performance, at every scale. Functional traits have become a staple for understanding species' resistance to abiotic stressors. However, we still miss consensus on the set of traits defining general woody plant adaptations to tolerate multiple abiotic stresses. We used a dataset of 779 woody species from the Northern Hemisphere to link the key traits defining the global spectrum of plant form and function (GSPFF) with two dimensions summarizing tolerance syndromes to drought, shade, cold and waterlogging. We evaluated these trait-tolerance relationships using generalized additive models at the plant functional type level (PFT, deciduous and evergreen angiosperms, and evergreen gymnosperms). Drought-tolerant angiosperms showed greater specific stem density and seed mass (SSD-SM), and lower specific leaf area and leaf nitrogen content (SLA-LN), compared to the cold/waterlogging tolerant species. Shade-tolerant angiosperms displayed greater SSD-SM and lower SLA-LN compared to intolerant angiosperms. For evergreen gymnosperms, the shade-drought trade-off was the key tolerance strategic axis of differentiation in trait variations. Independently of PFT, specialized tolerance strategies towards considered stressors were associated with different positioning in the GSPFF, and thus to contrasting trait combinations, marking the existence of pervasive functional constraints over polytolerance in woody plants. However, the trait combinations underlying different stress tolerance strategies mostly differed between angiosperms and gymnosperms, suggesting contrasting trait-tolerance relationships only at a broad taxonomic level.

How to cite: Pavanetto, N., Carmona, C. P., Niinemets, Ü., Laanisto, L., and Puglielli, G.: Functional traits associated with multiple abiotic stress tolerance strategies in woody plants of the Northern Hemisphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9264, https://doi.org/10.5194/egusphere-egu23-9264, 2023.

EGU23-9691 | ECS | Posters on site | BG3.1

Global biogeography of the biodiversity-productivity relationship in forests 

Haozhi Ma, Constantin Zohner, Daniel Maynard, Camille Delavaux, Miguel Berdugo, Lalasia Bialic-Murphy, Lidong Mo, Leila Mirzagholi, and Thomas Crowther

The biodiversity-productivity relationship (BPR) is central to our understanding of ecosystem functioning and restoration practices. Quantifying variation in the BPR across environmental gradients is thus critical for a spatially-explicit understanding of this key ecosystem property. Here, by integrating plot-level tree occurrence information from the Global Forest Biodiversity initiative (GFBi), satellite-derived net primary productivity, and environmental covariates, we estimated global variation in the BPR of forests along spatial and environmental gradients. The results show that variation in the forest BPR correlates with temperature and water availability, leading to significant differences in the forest BPR across biomes: the highest positive BPR occurs in arid and boreal forests, the lowest BPR in temperate broadleaved and mixed forests. In addition, forest age played a key role in mediating the BPR, with no BPR found in young forests (<100 years) and an increasingly positive BPR found in older forests. By quantifying the main drivers of global variation in the forest BPR, our study aids to a better understanding of forest ecosystem functioning and carbon storage and the global consequences of biodiversity loss.

How to cite: Ma, H., Zohner, C., Maynard, D., Delavaux, C., Berdugo, M., Bialic-Murphy, L., Mo, L., Mirzagholi, L., and Crowther, T.: Global biogeography of the biodiversity-productivity relationship in forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9691, https://doi.org/10.5194/egusphere-egu23-9691, 2023.

EGU23-10013 | Posters virtual | BG3.1

Design of a joint experimental and modelling platform to improve understanding of mechanisms and impacts of abiotic and biotic stress interactions in cereals 

Reimund P. Rötter, Michaela A. Dippold, Timothy Beissinger, Klaus Dittert, Susanne Neugart, Johannes Isselstein, Stefan Scholten, Michael Rostas, Stefan Siebert, Andreas von Tiedemann, Hans-Peter Piepho, Gennady Bracho-Mujica, Issaka Abdulai, Livia Paleari, Roberto Confalonieri, Dennis Otieno, Stephen G. Agong, and Senthold Asseng

A deeper understanding of the mechanisms underlying the impacts of multiple stresses in crops is direly needed given the climate change-induced risks to achieving food security for a growing world population. Global warming has already led to a higher frequency of multiple stresses occurring concurrently or subsequently and will continue to do so for the next decades. Plant-stress interactions are commonly subdivided into abiotic and biotic stresses and studied separately. Under field conditions, these stress interactions are usually multiple and interactive in character.

To date, the mechanisms determining interactions between abiotic and biotic stresses and their effects on crop performance are unknown for most crops and stress combinations. Field data are particularly scarce as most studies have focused on laboratory model systems using few environmental parameters in controlled conditions, which cannot reflect the dynamics in the field. Adequate modelling approaches capable of describing basic crop growth processes and simultaneously capturing response to abiotic and biotic stress interactions and their impacts on crop yield and quality do not exist so far.

The aim of this paper is to present the design of a joint experimental and modelling platform (MultiStress) capable of creating a deeper understanding of the overall impact of combined (abiotic+biotic) stresses on crop physiology and productivity (grain yield, biomass, grain and stover quality, nutrient/water use efficiency, etc.) using the cereal maize as one of the most important crops globally as a model.

The empirical knowledge gained from the experimental set-up and formalized in an associated modelling platform is utilized to define traits for stress tolerant breeding to be considered in ideotyping cereal cultivars for future target environments. In our example, in a research Pillar I, we describe a field experimental platform (with rainout shelters) applicable under temperate and tropical climate conditions to investigate the interactions of drought and nitrogen deficiency with the foliar disease Northern Corn Leaf Blight caused by Setosphaeria turcica on the one hand, and stem borer caterpillars on the other.  Pillar II is an associated process-based modelling platform enabling integration of new genetic and ecophysiological knowledge and extrapolate the findings in time and space.

Applying a systems approach in conjunction with this platform we can test the following hypotheses: (i) the impact of combined abiotic and biotic stress interactions on crop growth and yield formation and quality is non-additive and thus differs from the sum of individual stress impacts; (ii) while the mechanisms underlying the abiotic and biotic stress interactions are of universal validity, their impacts are modulated by certain environmental conditions (such as temperature, light conditions and soil properties).

Realization and evaluation of such platform will allow consideration of interactions between abiotic and biotic stresses and hence improve the predictive skill of crop growth models.

How to cite: Rötter, R. P., Dippold, M. A., Beissinger, T., Dittert, K., Neugart, S., Isselstein, J., Scholten, S., Rostas, M., Siebert, S., von Tiedemann, A., Piepho, H.-P., Bracho-Mujica, G., Abdulai, I., Paleari, L., Confalonieri, R., Otieno, D., Agong, S. G., and Asseng, S.: Design of a joint experimental and modelling platform to improve understanding of mechanisms and impacts of abiotic and biotic stress interactions in cereals, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10013, https://doi.org/10.5194/egusphere-egu23-10013, 2023.

EGU23-10049 | ECS | Orals | BG3.1

Using Machine Learning to Reveal the Relationships Between Plant Functional Traits and Flux Regimes at Eddy-Covariance Towers 

Jon Cranko Page, Gab Abramowitz, Martin G. De Kauwe, and Andy J. Pitman
The current-generation of land surface models (LSMs) are powerful tools used in predictions of the future global climate and carbon cycle. Many of these LSMs are parametrised using plant functional types (PFTs), often of a coarse nature with only relatively few possible groups. In turn, extensive use of eddy-covariance data is utilised when calibrating these LSMs, with the model PFT matched to the classification reported by the site owners. Importantly, the PFT group is one of the few site characteristics that is consistently supplied across FLUXNET sites. However, there are issues with this method of LSM calibration. It is well-known that many PFT classification schemes cannot be predicted from climate, and that traits may vary more within species or sites than between them.
Here we present our results assessing the suitability of PFTs for capturing site flux regimes using a suite of machine learning techniques. We explore natural groupings of sites based on the measurements used for LSM calibration and identify potential site characteristics and traits that might allow these natural groupings to be predicted. Our results identify driving characteristics of site flux regime differences, and can be used to direct LSM development and highlight priority locations for future eddy-covariance flux towers.

How to cite: Cranko Page, J., Abramowitz, G., De Kauwe, M. G., and Pitman, A. J.: Using Machine Learning to Reveal the Relationships Between Plant Functional Traits and Flux Regimes at Eddy-Covariance Towers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10049, https://doi.org/10.5194/egusphere-egu23-10049, 2023.

EGU23-13087 | ECS | Orals | BG3.1

Plant community changes in the arctic: effects on Carbon and Nitrogen stocks distribution in the environment. 

Hugo M. G. Potier, Xavier Raynaud, Yannick Agnan, Alienor Allain, Maryse Rouelle, and Marie A. Alexis

Arctic environments undergo important climatic changes that affect, among others, hydrology, soil processes, and plant communities of these systems. At large scale, tree-line and shrub cover have been reported to expand northward, although permafrost melting, increased snow cover and raised soil water content can promote herbaceous covers at the local scale. Our study evaluated carbon (C) and nitrogen (N) stocks in diverse environments at Abisko, northern Sweden: a mire site with palsa, bog, and fen and a shrub tundra site with a bog to broad-leaved forest gradient. Based on plant community survey and vegetation and soil C and N analysis, results showed that proportions of ligneous and herbaceous covers do not reflect the total biomass C and N stocks, with 140.1 ± 56.9 and 3.7 ± 1.5 g per square meter of ground-level vegetation on average, respectively. However, differences in the distribution of short-lived (e.g. leaves) and long-lived (e.g. woody) biomasses were found, with an increase of 1% to up to 40% of woody biomass in dryer sites. Those results were even more important in the broad-leaved forest where C and N stocks in wood, leaves and deadwood of birch trees were over thrice the stock of ground-level vegetation and represented 515.0 ± 115.9 and 17.0 ± 3.8 g.m-2, respectively. Regarding soils, C and N stocks varied mainly at large scale between the mire (47.1 ± 9.1 kgC.m-2 and 2.6 ± 0.4 kgN.m-2 for palsa; 20.2 ± 6.9 kgC.m-2 and 0.9 ± 0.4 kgN.m-2 for bog subsites) and other dryer environments (5.8 ± 1.4 kgC.m-2 and 0.21 ± 0.02 kgN.m-2 for shrub tundra and forest) with differences mostly driven by soil density, soil depth, and water content and not by the composition of the plant community. Our results suggest that plant community shrubification at a large scale is likely to increase the overall C and N stocks in these ecosystems, with more important stocks in long-lived biomass such as wood. While plant community composition and proportion of ligneous/herbaceous species seemed to be a good indicator of biomass distribution, soil stocks appeared not to be well predicted by our results. Those results could be used as a base to compute C and N stocks using remote-sensing data, to obtain information at larger scales for which extensive field measurements are harder to conduct.

How to cite: Potier, H. M. G., Raynaud, X., Agnan, Y., Allain, A., Rouelle, M., and Alexis, M. A.: Plant community changes in the arctic: effects on Carbon and Nitrogen stocks distribution in the environment., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13087, https://doi.org/10.5194/egusphere-egu23-13087, 2023.

EGU23-13211 | Orals | BG3.1

Do fine root morphological and functional adaptations support regrowth success in a tropical forest restoration experiment? 

Florian Hofhansl, Oscar Valverde Barrantes, Eduardo Chacón-Madrigal, Peter Hietz, Anton Weissenhofer, Judith Prommer, Wolfgang Wanek, and Lucia Fuchslueger

In early stages of forest succession plants have a high nutrient demand, but it is still a matter of debate if regrowth success of pioneer species is related to plant functional traits favoring fast soil colonization and nutrient acquisition. In general, we would expect trade-offs between plant growth performance and fine root morphological properties in association with different plant life-history strategies. Hence, we hypothesized that fast growing plants should have a more efficient root system that allows them to outcompete slow-growing neighbors in a resource-limited environment.

To test our hypothesis we monitored plant successional growth dynamics in a tropical lowland rainforest reforestation experiment conducted in southwest Costa Rica. We collected absorptive roots (<2mm diameter) from plant individuals (comprising 20 tree species and 11 plant families) with different growth dynamics (as indicated by measurements of stem diameter and height). For these samples we assessed a suite of fine root morphological traits, such as legume nodulation status, and furthermore quantified fine root nutrient concentration and phosphatase activities, as well as microbial biomass and phosphatase activity in soils in the close vicinity of fine roots.

We found stark differences in fine root characteristics between the tree species investigated in this study, such that fast growing species exhibited relatively larger specific root length and higher turnover, whereas slow growing species tend to rely on mechanical resistance by increasing root tissue density and root life span. Our results suggest that the identified differences in the root trait spectrum between fast and slow growing species reflect plant functional adaptions to resource limitation, edaphic properties and soil microbial symbioses. Our findings further highlight the crucial need to foster our understanding of belowground root morphological and physiological traits during forest succession, especially so when aiming to restore forest ecosystem functioning in formerly intensified land-use systems.

How to cite: Hofhansl, F., Valverde Barrantes, O., Chacón-Madrigal, E., Hietz, P., Weissenhofer, A., Prommer, J., Wanek, W., and Fuchslueger, L.: Do fine root morphological and functional adaptations support regrowth success in a tropical forest restoration experiment?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13211, https://doi.org/10.5194/egusphere-egu23-13211, 2023.

EGU23-13427 | ECS | Orals | BG3.1

Environmental niche characterization of plant functional groups 

Julia Joswig and Meredith C. Schuman

Ecosystem functioning is thought to be mediated by traits of organisms living within phylogenetic constraints. Plant groups of similar traits (functional groups) are likely to fit into a similar environmental niche. Characterizing functional groups’ niche space along environmental gradients would allow us to better understand patterns of trait variation.

We aim at defining the global environmental niche, i.e. the trait space filled at a given environment, of different functional groups of plants. 

In particular, we compare the environmental functional diversity (FD) gradients of four functional plant groups. These functional groups represent major differences in size and plant economy, derived from global in situ trait data of the TRY database. We find their gradients to vary in shape and strength. For example, tall-and-slow species’ FD varies more than small-and-slow ones, with a high FD in the Mediterranean. 

This study's findings point to how global change may affect functional groups differently and may ultimately provide valuable insights into ecosystem functioning.

How to cite: Joswig, J. and Schuman, M. C.: Environmental niche characterization of plant functional groups, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13427, https://doi.org/10.5194/egusphere-egu23-13427, 2023.

EGU23-13750 | ECS | Orals | BG3.1

Comprehensive intercomparison and evaluation of global upscaled foliar trait maps 

Benjamin Dechant, Ryan Pavlick, Fabian Schneider, and Philip Townsend and the sTRAITS working group

Global trait maps of specific leaf area (SLA), leaf nitrogen (N) and phosphorus (P) contents have been generated using a wide range of data-driven upscaling approaches. We comprehensively studied their consistency and agreement with sPlotOpen data at 0.5 degee grid cells. For this, we developed approaches to separate the maps into their plant functional type (PFT) components by taking into account within-grid-cell heterogeneity and stratified sPlotOpen data by PFT.

We found that despite many differences in the upscaling approaches, the maps fall into two groups: One group using remote sensing based, fractional PFT cover  in the upscaling, while the other did not. Spatially, the main differences between the two groups are located in areas of high within-grid-cell trait heterogeneity and these areas dominate global trait variations due to the combined effects of fractional PFT cover and trait differences between-PFTs.

The agreement of upscaled maps with sPlotOpen data strongly depends on the way sPlotOpen data are scaled to the grid cell. When using a similar scaling approach as the upscaling approaches a similar level of agreement can be observed for both groups of maps. However, only the maps that used PFT information could capture main features of between-PFT differences, especially the low values of SLA and N in evergreen needleleaf forests. Within-PFT trait variations of upscaled maps partly showed similar patterns as sPlotOpen data when aggregated to latitudinal averages but considerable differences remain and the evaluation is challenging without having the original maps per PFT. 

We conclude that fractional PFT cover contains essential information for capturing global, top-of-canopy trait patterns using upscaling approaches at moderate to coarse spatial resolution.

How to cite: Dechant, B., Pavlick, R., Schneider, F., and Townsend, P. and the sTRAITS working group: Comprehensive intercomparison and evaluation of global upscaled foliar trait maps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13750, https://doi.org/10.5194/egusphere-egu23-13750, 2023.

EGU23-14748 | Orals | BG3.1

Towards ecosystem functionality: the case of sulphide mining tailings colonization. 

Juan Antonio Campos, Jaime Villena, Marta Maria Moreno, and Jesús Daniel Peco

The enormous diversity of variables that come together in the functioning of ecosystems makes it very difficult to establish reliable patterns of functionality, understood as the ability of ecosystems to progress in a balanced way with their own resources. The natural colonization of spaces degraded by mining offers us the opportunity to study the construction of an ecosystem from its beginnings. The scarcity of resources and the geochemical conditions that occur in these spaces carry out a screening of species and, consequently, the communities that establish in these soils are much simpler. In a mining area close to the city of Ciudad Real (Spain), large deposits of fine material, originating from mining processes, have remained untouched for more than 70 years and have become an exceptional place to study the rate of natural colonization and soil formation on a short scale of time and space. The transition between a bare regolithic substratum and a functional soil was monitored and analyzed to find out which are the key factors on which the functionality of the ecosystem is based. The special abilities of some pioneer plant species, the collaboration between them and the climatic factors of the study area, establish a unique path towards the achievement of a viable and functional ecosystem. In our work we have studied the natural colonization process that has occurred in a mining tailings dump (6 ha), analyzing the essential role of the reed (Phragmites australis) as a colonizing plant. Indeed, this species creates a dense network of rhizomes that favors the retention of edaphic resources such as organic matter, water and clay that will help other species to settle. In this way, a process of creating a new ecosystem begins, whose evolution will be conditioned only by the restrictions imposed by climatic patterns of rainfall and extreme temperatures. Plant species specific distribution, the standing biomass the microbial composition and enzymatic activity of the soil have been monitored, as well as the standardized soil parameters such as pH, texture, organic matter characterization, etc.

How to cite: Campos, J. A., Villena, J., Moreno, M. M., and Peco, J. D.: Towards ecosystem functionality: the case of sulphide mining tailings colonization., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14748, https://doi.org/10.5194/egusphere-egu23-14748, 2023.

EGU23-15379 | ECS | Orals | BG3.1

Global biodiversity patterns of woody and herbaceous flowering plants in space and time 

Ao Luo, Xiaoting Xu, Yunpeng Liu, Yaoqi Li, Xiangyan Su, Yichao Li, Tong Lyu, Dimitar Dimitrov, Markku Larjavaara, Shijia Peng, Yongsheng Chen, Qinggng Wang, Niklaus Zimmermann, Loïc Pellissier, Bernhard Schmid, and Zhiheng Wang

Plant biodiversity can be structured into different growth forms (i.e. woody vs. herbaceous) with divergent distributions, evolutionary histories, and relationships with climate thus they should be separately analyzed to better understand plant diversity. Flowering plants (angiosperms) are the most successful group of plants and have a diversity of growth forms that differs from other groups such as gymnosperms, all of which are woody species. However, there is still a gap in current growth form databases to cover most angiosperms. To fill the gap, this study collect data on growth forms of angiosperm species from published floras, online databases, and peer-reviewed journal articles and compiled a massive database of growth forms (woody and herbaceous, 300,750 species). Combined with distributions of 332,293 species, we mapped the current global geographical patterns in woody and herbaceous species as well as their relative proportion and assess their relationship with climate. This study also reconstructed ancestral states of growth forms through the angiosperm phylogeny to demonstrate the Cenozoic evolutionary dynamics of growth forms and explore the evolutionary transitions between the two growth forms.

How to cite: Luo, A., Xu, X., Liu, Y., Li, Y., Su, X., Li, Y., Lyu, T., Dimitrov, D., Larjavaara, M., Peng, S., Chen, Y., Wang, Q., Zimmermann, N., Pellissier, L., Schmid, B., and Wang, Z.: Global biodiversity patterns of woody and herbaceous flowering plants in space and time, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15379, https://doi.org/10.5194/egusphere-egu23-15379, 2023.

EGU23-15628 | Orals | BG3.1

Simultaneous O2 and CO2 Flux Measurements with Custom-made Branch Chambers for Fagus sylvatica 

Alexander Knohl, Anne Klosterhalfen, Jan Muhr, Emanuel Blei, Mattia Bonazza, Dietmar Fellert, Andrew Manning, Christian Markwitz, Penelope A. Pickers, Frank Tiedemann, Edgar Tunsch, and Yuan Yan

The O2:CO2 exchange ratio of plants is an only recently explored new plant trait and provides novel insights into the carbon cycle. Measurements of O2 fluxes at field sites are, however, scarce due to a number of technical challenges. This work presents unique field measurements of O2 and CO2 mole fractions and exchange fluxes of tree branches using a custom-made fully automated chamber system for quasi-continuous, high-precision measurements between Fagus sylvatica leaves and the atmosphere. Data from the vegetation period of 2021 in a temperate beech forest in Germany are shown.

Four steady-state, open-throughflow branch chambers were part of a larger chamber measurement set-up that also included four stem and eight soil chambers that were connected via a custom-built valve switching system to a modified FC-2 Differential Oxygen Analyzer (Oxzilla, Sable Systems International), and an LI-820 analyzer (LI-COR Biogeosciences GmbH). Precision was 1.3 ppm for O2 and 0.3 ppm for CO2. Both analyzers were located in an air-conditioned hut. O2 and CO2 mole fractions were measured continuously and logged in 10-sec intervals. Chambers were measured sequentially with typical observation times of 20-45 min per chamber, i.e. long enough for the mole fractions to reach steady state and allowing for at least two full measurement cycles of all sixteen chambers per day. For data processing, a quality check routine was developed for the branch chamber measurements, where spikes and non-steady-state conditions were excluded, and finally leaf exchange fluxes were quantified.

Diel, diurnal, and day-to-day variabilities were related to environmental and meteorological conditions. Further, the O2:CO2 exchange ratio on leaf-level was investigated for day- and nighttime. We could observe that the O2:CO2 exchange ratio varied stronger during nighttime than daytime and was affected mostly by the flux magnitude, the photosynthetically active radiation, and vapor pressure deficit. The exchange ratio was usually between 0.9 and 1.0 μmol μmol-1.

Finally, we evaluated simulated photosynthetical O2 and CO2 fluxes of an extended version of the one-dimensional, multi-layer atmosphere-biosphere gas exchange model CANVEG based on the obtained measurements.

How to cite: Knohl, A., Klosterhalfen, A., Muhr, J., Blei, E., Bonazza, M., Fellert, D., Manning, A., Markwitz, C., Pickers, P. A., Tiedemann, F., Tunsch, E., and Yan, Y.: Simultaneous O2 and CO2 Flux Measurements with Custom-made Branch Chambers for Fagus sylvatica, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15628, https://doi.org/10.5194/egusphere-egu23-15628, 2023.

EGU23-16063 | ECS | Orals | BG3.1

AngleCam - Tracking leaf angle distributions through time with image series and deep learning 

Teja Kattenborn, Ronny Richter, Claudia Guimarães-Steinicke, Hannes Feilhauer, and Christian Wirth

Vertical leaf angles and their temporal variation are directly related to multiple ecophysiological and environmental processes and properties. However, there is no efficient method for tracking leaf angles of plant canopies under field conditions.

Here, we present AngleCam, a method to estimate leaf angle distributions from horizontal photographs acquired with timelapse cameras and deep learning. The AngleCam is a pattern recognition model based on convolutional neural networks and was trained with leaf angle distributions obtained from visual interpretation of more than 2500 plant photographs across different species and scene conditions.

Leaf angle predictions were evaluated over a wide range of species, plant functional types and scene conditions using independent samples from visual interpretation (R2 = 0.84). Moreover, the method was evaluated using leaf angle estimates obtained from terrestrial laser scanning (R2 = 0.75). AngleCam was successfully tested under field-conditions for the long-term monitoring of leaf angles for two broadleaf tree species in a temperate forest. The plausibility of the predicted leaf angle time series was underlined by its close relationship with environmental variables related to transpiration. Moreover, showed that the variation in leaf angles resembles changes in several leaf-water related traits.

The evaluations showed that AngleCam is a robust and efficient method to track leaf angles under field conditions. The output of AngleCam is compatible and relevant for with a range of applications, including functional-structural plant modelling, Earth system modelling or radiative transfer modelling of plant canopies. AngleCam may also be used to predict leaf angle distributions from existing data, such as curated in PhenoCam networks or citizen science projects.

How to cite: Kattenborn, T., Richter, R., Guimarães-Steinicke, C., Feilhauer, H., and Wirth, C.: AngleCam - Tracking leaf angle distributions through time with image series and deep learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16063, https://doi.org/10.5194/egusphere-egu23-16063, 2023.

EGU23-16466 | ECS | Orals | BG3.1

The Nitrogen Games – the invasive success of Fallopia japonica 

Sierra Grange, Johanna Girardi, Clara Mendoza Lera, Jens Dyckmans, Melanie Brunn, and Hermann Jungkunst

The high invasion success of Fallopia japonica in Europe and North America is related to its niche construction strategy. A hotly debated and prominent possibility is that F. japonica uses weapons for chemical niche construction, which could have considerable consequences for plant nutrition and ecosystem functioning. At least one of its phenolic compounds is capable of inhibiting nitrification and nitrification is actually lower in F. japonica invaded systems. It was assumed that F. japonica has a higher affinity for ammonium and can therefore outcompete native plants that prefer nitrate. However, the uptake of ammonium by F. japonica has only been minimally studied and it has been shown that nitrogen-use efficiency seems to be the main trait. In a lab study using stable isotope labelling we tested nitrogen and carbon uptake of F. japonica against the strongest native competitor in European riparian zones U. dioica. We hypothesized that F. japonica has a greater potential to take up ammonium and that U. dioica would take advantage of the nitrate supply, and that F. japonica would have a slightly better nitrogen-use efficiency than U. .

We performed combined ¹³C-CO2 and ¹⁵N-NO3 and -NH4 labelling on young F. japonica and U. dioica plants. They were pulse labelled with ¹³CO₂ and fertilized with ¹⁵N enriched nitrate or ammonium (44 mg N kg -¹ dry soil). Atom excess of ¹⁵N and ¹³C, was measured after seven days in non-rooted soil, rhizosphere, fine roots, transport roots, and shoots. Contrary to our expectations, F. japonica always utilized less soil mineral N independent of the type of nitrogen.Overall, our data revealed that the ability of F. japonica to inhibit nitrification is not based on an affinity for ammonium. Therefore, it appears that F. japonica constructs its biogeochemical niche in a way to benefit from nitrogen-use efficiency, which we found to be higher, by supressing nitrification in nutrient rich habitats.

How to cite: Grange, S., Girardi, J., Mendoza Lera, C., Dyckmans, J., Brunn, M., and Jungkunst, H.: The Nitrogen Games – the invasive success of Fallopia japonica, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16466, https://doi.org/10.5194/egusphere-egu23-16466, 2023.

EGU23-1232 | Orals | BG3.2 | Highlight

Carbon storage pools of trees: fixed or flexible? 

Guenter Hoch, Raphael Weber, Cedric Zahnd, and Ansgar Kahmen

Most of the carbon (C) reserves in trees are stored in the living parenchyma of stems and roots and exhibit characteristic variations with phenology, growth and environmental stress. Up to date, it is only partially understood how the formation and re-mobilization of stored C in sapwood is regulated and synchronized over tissues and long distances. Mechanistic concepts of C storage therefore often assume simple bucket-models, where the amount of stored C equals the net-balance between C assimilation and the sum of all C sink activities (e.g., respiration and growth).

Here, we summarize results from previous experimental and observational studies in our group, that tested the reaction of non-structural carbohydrate reserve pools in trees to situations of limited photosynthetic C supply. Overall, these studies suggested that C reserve concentrations in sapwood follow abrupt changes of the net C-source-sink balance in the short-term and at severe C starvation, but they consistently reach homeostatic levels that are very similar across different C-source-sink conditions over longer time periods. According to our findings, we propose that C reserve pool sizes in tree are determined and closely controlled rather than the simple net-result of C source vs. -sink activities. With respect to mechanistic C models of trees, this suggests that C reserves should be rather treated as a fixed C-sink than a variable parameter.

How to cite: Hoch, G., Weber, R., Zahnd, C., and Kahmen, A.: Carbon storage pools of trees: fixed or flexible?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1232, https://doi.org/10.5194/egusphere-egu23-1232, 2023.

EGU23-1764 | ECS | Posters on site | BG3.2

Global variation in the ratio of sapwood to leaf area explained by optimality principles 

Huiying Xu, Han Wang, I. Colin Prentice, Sandy P. Harrison, Lucy Rowland, Maurizio Mencuccini, Pablo Sanchez-Martinez, Pengcheng He, Ian J. Wright, Stephen Sitch, and Qing Ye

The sapwood area supporting a given leaf area (vH) reflects a coordinated coupling between carbon uptake, water transport and loss at a whole plant level. Worldwide variation in vH reflects diverse plants strategies adapt to prevailing environments, and impact the evolution of global carbon and water cycles. Why such a variation has not been convincingly explained yet, thus hinder its representation in Earth System Models. Here we hypothese that optimal vH tends to mediate between sapwood conductance and climates so that leaf water loss matches both sapwood hydraulics and leaf photosynthesis. By compiling and testing against two extensive datasets, we show that our hypothesis explains nearly 60% of vH variation responding to light, vapor pressure deficit, temperature, and sapwood conductance in a quantitively predictable manner. Sapwood conductance or warming-enhanced hydraulic efficiency reduces the demand on sapwood area for a given total leaf area and, whereas brightening and air dryness enhance photosynthetic capacities consequently increasing the demand. This knowledge can enrich Earth System Models where carbon allocation and water hydraulics play key roles in predicting future climate-carbon feedback.

How to cite: Xu, H., Wang, H., Prentice, I. C., Harrison, S. P., Rowland, L., Mencuccini, M., Sanchez-Martinez, P., He, P., Wright, I. J., Sitch, S., and Ye, Q.: Global variation in the ratio of sapwood to leaf area explained by optimality principles, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1764, https://doi.org/10.5194/egusphere-egu23-1764, 2023.

EGU23-2971 | ECS | Orals | BG3.2 | Highlight

Allocation mediates plant drought stress and productivity in a changing climate 

Anna Trugman and Gregory Quetin

The extent to which future climate change will increase forest stress and the amount to which species and forest ecosystems can acclimate or adapt to increased stress is a major unknown. We used high resolution maps of hydraulic traits representing the diversity in tree drought tolerance across the United States combined with a hydraulically-enabled tree model to quantify the ability for within-species changes in allocation and between-species range shifts to mediate climate stress. We found that forests are likely to experience increases in chronic hydraulic stress with climate change, even with expected increases in atmospheric CO2. Based on current species distributions, regional hydraulic trait diversity was sufficient to buffer against increased stress in 86% of forested areas. Importantly, changes in leaf allocation have the potential to substantially decrease stress, reducing the need for biogeographic shifts in species distributions. However, observed trait velocities are not keeping up with the rate required to ameliorate projected future stress.

How to cite: Trugman, A. and Quetin, G.: Allocation mediates plant drought stress and productivity in a changing climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2971, https://doi.org/10.5194/egusphere-egu23-2971, 2023.

EGU23-3944 | ECS | Posters virtual | BG3.2

Variation in ecosystem carbon allocation patterns among different vegetation types in Western Ghats, India 

Subashree Kothandaraman, Javid Dar, Somaiah Sundarapandian, and Mohammed Khan

A major global challenge is the urgent need to bend the curve of rising atmospheric carbon dioxide (CO2) concentration. Carbon (C) pools in forests play an important role in regulating the regional and global C cycles. In this study, C stocks of all the pools {live biomass (trees and non-tree vegetation), detritus (deadwood and forest floor litter), and soil} were assessed from six vegetation types {3 natural forests (tropical dry deciduous, semi-evergreen and evergreen) and 3 plantations (teak, rubber and areca nut)} in Kanyakumari Wildlife Sanctuary, Western Ghats, India. The total ecosystem C stock averaged 262.7 ± 56 Mg C ha-1 and ranged between 94.7 and 506.8 56 Mg C ha-1. Soil was the major C pool in tropical dry deciduous forest and areca nut plantation, whereas biomass was the largest pool in other vegetation types. The C stocks of teak and rubber plantations were comparable with those of dry deciduous and semi-evergreen forest types respectively. The C stocks were significantly positively correlated with stand density, basal area and mean annual precipitation, and negatively correlated with mean annual temperature. The present study would improve our understanding on C allocation patterns at ecosystem-level in different vegetation types of Western Ghats, and can be used for ecosystem restoration and forest management programmes to enhance C sequestration.

How to cite: Kothandaraman, S., Dar, J., Sundarapandian, S., and Khan, M.: Variation in ecosystem carbon allocation patterns among different vegetation types in Western Ghats, India, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3944, https://doi.org/10.5194/egusphere-egu23-3944, 2023.

Root exudates are an important pathway for plant-microbial interactions and are highly sensitive to climate change. However, how extreme drought affects root exudate and its components, as well as species-specific difference in response magnitude and direction, are poorly understood. In this study, root exudation rates of total carbon (C) and its components (e.g., sugar, organic acid, and amino acid) were measured under the control and drought treatments (i.e., 70% throughfall reduction) by in situ collection of four tree species with different growth rates in a subtropical forest. We also quantified soil properties, root morphological traits, and mycorrhizal infection rates to examine the driving factors underlying variations in root exudation. Our results showed that drought significantly decreased root exudation rates of total C, sugar, and amino acid by 17.8%, 30.8%, and 35.0%, respectively, but increased root exudation rate of organic acid by 38.6%. These changes were largely associated with drought-induced changes in tree growth rates, root morphological traits, and mycorrhizal infection rates. Specifically, trees with relatively high growth rates were more responsive to drought for root exudation rates compared to those with relatively low growth rates, which were closely related to root morphological traits and mycorrhizal infection rates. These findings highlight the importance of plant growth strategy in mediating drought-induced changes in root exudation rates. The trade-offs between root exudation rates, root morphological traits, and mycorrhizal symbioses in response to drought could be incorporated into land surface models to improve the prediction of climate change impacts on rhizosphere C dynamics in forest ecosystems. 

How to cite: Zhou, X., Jiang, Z., and Fu, Y.: Plant growth strategy determines the magnitude and direction of drought-induced changes in root exudates in subtropical forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4097, https://doi.org/10.5194/egusphere-egu23-4097, 2023.

EGU23-4386 | Posters on site | BG3.2

The role of the bole: constraints in the remobilization of stem reserves under experimental carbon limitation 

Simon M. Landhäusser, Coral Fermaniuk, Killian G. Fleurial, and Erin Wiley

Assimilated non-structural carbohydrates (NSC) can be stored as reserves in plants and remobilized during periods of asynchrony between carbon acquisition and carbon demand to fuel essential metabolic functions and growth. However, the framework of NSC allocation to reserves and their remobilization remains unclear, especially for mature trees which potentially can store large quantities of reserves. Here, we explore the role of stem reserves and potential constraints in their remobilization in large Betula papyrifera trees. To explore reserve remobilizations between organs, we use different patterns of phloem girdling to induce carbon stress and to isolate crown, stem, and root NSC storage pools.  Our results suggest that NSC reserves in the stem tissues may not be easily remobilized to other, more distant, organ sinks. However, we also found that some root reserves may be allocated toward the lowermost stem/root collar position, indicating that under carbon limiting conditions the roots might not be the strongest sink for NSC reserves. We suggest this response represents an adaptive recovery strategy for a collar-sprouting species like B. papyrifera, which occupies areas prone to aboveground disturbance. We also found that storage capacity of tissues (here stem wood and crown) can far exceed the concentrations that are normally stored in these trees.  Additionally, we found stem NSC concentrations positively correlated with disease resistance and branch water content.  These relationships suggest that a maintenance of greater stem reserves may be required to support other important roles directly or indirectly, such as defense or spring leaf flush, respectively.  Overall, it appears that the remobilization of different organ reserve storage pools is regulated somewhat autonomously, which, particularly under carbon limiting conditions, could potentially limit the sharing of reserves within a large tree.

How to cite: Landhäusser, S. M., Fermaniuk, C., Fleurial, K. G., and Wiley, E.: The role of the bole: constraints in the remobilization of stem reserves under experimental carbon limitation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4386, https://doi.org/10.5194/egusphere-egu23-4386, 2023.

EGU23-5105 | ECS | Posters on site | BG3.2

Implication of carbon allocation in plants for soil organic matter cycling. 

Baptiste Hulin and Samuel Abiven

Plants allocate carbon to roots, shoots, respiration and rhizodeposition. The quantitative partitioning depends on genetic and environmental factors, as well as on the plant’s phenology. The first two or three pools represent most of the carbon input to the soil, depending on the ecosystem considered. Quantifying this partitioning is of major importance as roots, shoots, and rhizodeposition are constituted of several organic compounds differing in residence time. Moreover, besides being carbon inputs, these compounds modify in different ways their surroundings and might slow down or accelerate the cycling of carbon and nutrients.

One frequently used method to quantify this partitioning is the 13C labelling of atmospheric CO2, which allows to trace organic carbon in the soil-plant system. 13C labelling of CO2 can be either continuous, or as single or multiple pulses. It can be combined with gas measurements that estimate the priming effect induced by the plant inputs. This poster aims at synthesizing the literature about experimental quantification of carbon allocation to different plant pools, and comparing the methods used. It allows to identify the plant traits that predict this allocation. Moreover, we show the preliminary results of a continuous 13C labelling experiment that compares plant traits with carbon content variations in soil columns.

Whereas shoots and roots are relatively simple to quantify, rhizodeposition is not. It therefore represents a major incertitude when considering the carbon inputs to soil. Moreover, labile exudates represent an important part of rhizodeposition that induce an increase of older soil carbon mineralisation. Several experiments show that the loss of carbon induced by rhizodeposition priming effect is bigger than the input. These results are often associated to plants with high photosynthetic activity.

A trade-off is to be found when considering 13C labelling. Continuous labelling allows a quantification of net rhizodeposition which is independent of the phenology and that integrates the whole plant growth. On the other side, pulse labelling is easier and less expensive. Regarding priming effect quantification, gas flux measurements are precise but do not integrate the whole plant growth. Mass quantification through carbon content change do, but it requires very accurate estimations of these changes.

How to cite: Hulin, B. and Abiven, S.: Implication of carbon allocation in plants for soil organic matter cycling., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5105, https://doi.org/10.5194/egusphere-egu23-5105, 2023.

EGU23-5112 | ECS | Posters on site | BG3.2

Experimental investigation of the relationship between root:shoot ratio and soil-plant hydraulics. 

Andrea Cecere and Mathieu Javaux

In a context of global change, it is crucial to understand the factors and processes by which plants respond to drought and by which crops may limit the development of their aboveground biomass.

Experimental studies have showed that soil water status, soil structure and soil texture impact carbon allocation within plant and in particular the root:shoot ratio. We used a conceptual soil-plant hydraulic model to analyze the results of a meta-analysis gathering literature data of root:shoot ratio measured in controlled conditions. For each paper, information on soil water status, soil and plant traits and abiotic factors were collected. Soil hydraulic conductivity was estimated based on pedotransfer functions, when unavailable.

The results feature that the root:shoot ratio is an adaptation strategy that depends on the soil conductance in order to balance the water availability with the transpiration demand. The partitioning response varies between plant types. This study gives an explanation to current observations and shows the necessity to collect accurate soil measurements and information for further experiments.  

How to cite: Cecere, A. and Javaux, M.: Experimental investigation of the relationship between root:shoot ratio and soil-plant hydraulics., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5112, https://doi.org/10.5194/egusphere-egu23-5112, 2023.

EGU23-5188 | ECS | Orals | BG3.2

Drought intensity controls carbon allocation dynamics within experimental Scots pine-soil systems 

Emily Solly, Astrid Jaeger, Matti Barthel, Roland Werner, Alois Zürcher, Frank Hagedorn, Johan Six, and Martin Hartmann

Climate change is causing negative effects on forests and their functioning through more frequent and intense periods of drought. Repeated conditions of water limitation not only affect the growth and vitality of trees but also feed back on the cycling of carbon (C) at the plant-soil interface. However, the impact of the intensity of drought on the transfer of assimilated C belowground remains quantitatively unresolved. We assessed how increasing levels of soil water limitation affect the growth of Scots pine (Pinus sylvestris L.) saplings and performed a 13C-CO2 pulse labelling experiment to trace the pathway of newly-assimilated C into needles, fine roots, soil pore CO2, and phospholipid fatty acids of soil microbial groups. We hypothesized that increased water stress would reduce tree C uptake, and the magnitude and velocity at which newly-assimilated C is allocated belowground and further metabolized. Moreover, we expected that severe levels of soil water deficit would lead to a build-up of newly-assimilated C in fine roots. Our data indicated that with more intense water limitation, trees reduced their growth despite initially partitioning more biomass to belowground tissues under severe water stress. Moderate levels of water limitation barely affected the uptake of 13C label and the magnitude and transit times of C being allocated from needles to the rhizosphere. In contrast, severe water limitation increased the fraction of 13C label allocated to roots and soil fungi while a lower fraction of 13CO2 was respired from the soil. We conclude that when soil water becomes largely unavailable, C cycling within trees becomes slower, and a major fraction of C allocated belowground is accumulated in roots or transferred to the soil and associated microorganisms without being metabolically used. Our experiment overall demonstrates the relevance of quantifying the level of water limitation at which C allocation dynamics within trees and soils are altered to inform about the trajectory of forests to the environmental pressures they face.

How to cite: Solly, E., Jaeger, A., Barthel, M., Werner, R., Zürcher, A., Hagedorn, F., Six, J., and Hartmann, M.: Drought intensity controls carbon allocation dynamics within experimental Scots pine-soil systems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5188, https://doi.org/10.5194/egusphere-egu23-5188, 2023.

EGU23-5410 | Orals | BG3.2

Carbon and nitrogen exchange between trees and mycorrhizal fungi at treeline ecotone 

Boaz Hilman, Emily Solly, Ivano Brunner, Susan Trumbore, and Frank Hagedorn

The formation of high elevation treelines is thought to result from direct low-temperature growth limitation, but the in-direct role of nitrogen (N) in modifying growth has rarely been evaluated. Slow N mineralization rates in cold soils may push trees to rely more on N supplied by symbiotic mycorrhizal fungi. Here, we investigated the carbon (C) and N exchange between trees and mycorrhizal fungi along an Alpine treeline ecotone using bomb 14C and natural abundance isotopes (13C and 15N). We collected fine roots, branches, and needles from two tree species (Larix decidua L. and Pinus mugo spp. uncinata Ramond) and sporocarps of mycorrhizal and free-living (saprotrophic) fungal genera. 14C measurements demonstrated that mycorrhizal fungi rely on new photo-assimilates derived from fine roots, while saprotrophic fungi feed on several years old C (4-10 yr). The C transfer root-fungi seems to have isotopic fractionation that enriches the fungi with 13C in 1-5‰. Mycorrhizal fungi had higher δ15N values and C:N ratio than saprotrophic fungi. Assuming that the two fungi types share the same N source in the soil, the 15N enrichment and the lower N concentration of the mycorrhizal fungi could be explained through preferential transfer of 14N to the hosting trees. The δ15N in the trees generally decreased with increasing elevation, suggesting a greater reliance on N supplied by mycorrhizal fungi in colder soils. However, abrupt increase in the Larix δ15N at the treeline suggests opening of the N cycle for this deciduous tree species, either by a decreasing N demand of slow-growing trees or a reduced competition for N with other plants. Overall, our results indicate that in cold treeline ecotones the sources and availabilities of soil N have a key influence on determing the N uptake pathways of trees and consequently plant growth.

How to cite: Hilman, B., Solly, E., Brunner, I., Trumbore, S., and Hagedorn, F.: Carbon and nitrogen exchange between trees and mycorrhizal fungi at treeline ecotone, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5410, https://doi.org/10.5194/egusphere-egu23-5410, 2023.

EGU23-5745 | ECS | Orals | BG3.2

Increased belowground tree carbon allocation in a mature mixed forest in a dry vs. a wet year 

Ido Rog, Boaz Hilman, Hagar Fox, Shifra Avital, and Tamir Klein

Climate change is expected to increase the frequency and severity of droughts in Mediterranean forests. Tree survival and storage of atmospheric CO2 in these forests depend on how individual tree species allocate their carbon (C). Here, we measured a complete set of above- and belowground C pools and fluxes in five coniferous and broadleaf species co-existing in a mature evergreen forest. Our study period included a drought year, followed by an above-average wet year, and the seasonal long dry period characterizes Mediterranean climate. To quantify the exact timing and spatial distribution of belowground C allocation, we additionally applied 13CO2 pulse labelling of one of the tree species (Quercus calliprinos). We found that during the dry versus wet year, photosynthetic C uptake decreased, C use in the C sinks remained unchanged and C allocation to belowground sinks increased. Among the five major C sinks, respiration was the main flux (~64%), while smaller fluxes like exudation (~9%) and reproduction (~1%) were those which increased the most in the dry year. To cope with seasonal drought, most trees relied on starch to maintain the C supply, but between years we found no significant differences in starch and sugars in aboveground tissues. Relative to the C storage dynamics, higher water use efficiency was found in conifers, while species-specific differences between dry and wet years were found among the broadleaves. Interestingly, in the wet season, after pulse labelling, C was allocated from the labeled leaves to the roots in two main time-lags: first after 3-5 days and second after 15-20 days. Labeled C reached fine roots at a distance of 0-6 m from the labeled tree. These detailed tree-level observations expose inter-annual and interspecific differences in C allocation among fluxes and tissues, specifically in response to varying water availability.

How to cite: Rog, I., Hilman, B., Fox, H., Avital, S., and Klein, T.: Increased belowground tree carbon allocation in a mature mixed forest in a dry vs. a wet year, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5745, https://doi.org/10.5194/egusphere-egu23-5745, 2023.

EGU23-6348 | Posters on site | BG3.2

Day-night root dynamics change through the growing season 

Richard Nair, Martin Strube, Marion Schrumpf, and Mirco Migliavacca

Roots are difficult to measure at high temporal resolution but are important as belowground sinks and sources of CO2. Even in an age of automated and remote estimation of many ecosystem properties, belowground plant biomass is opaque at all but the coarsest timescales. Further, root dynamics are not fully predictable from aerial biomass change. Many uncertainties in predicting whole ecosystem function derive from this lack of data belowground.

Using automated minirhizotrons, we captured images of root dynamics four times a day from February to October in a permanent temperate grassland in Germany. We processed all images collected using a trained neural network model and image analysis scripts to extract morphological traits from segmented images. We found root growth occurring continuously, even at sub-zero aboveground air temperatures. As a whole population, most of the root growth was in spring, although turnover and replacement happened at all times. Root length density and extractable root surface area increased through spring but decreased through a dry summer into autumn. Mean rooting depth increased until summer but did not decrease during the study period. Mean root diameter only increased once the dry period began.

We also examined the patterns of growth between day and night. Early in the year roots grew in both day and night time periods, but after initial rapid biomass growth, root growth was at night. We examine the  reasons for this switch relating to source and sink control of plant growth. We also consider implications for an accurate partitioning of carbon budgets in terrestrial ecosystems.

 

How to cite: Nair, R., Strube, M., Schrumpf, M., and Migliavacca, M.: Day-night root dynamics change through the growing season, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6348, https://doi.org/10.5194/egusphere-egu23-6348, 2023.

EGU23-6985 | ECS | Posters on site | BG3.2

Modeling the partitioning of assimilated C along the soil-plant-atmosphere continuum based on a 13C labeling experiment 

Ruth Adamczewski, Qiong Liu, Johanna Pausch, and Mohsen Zarebanadkouki

Modeling and quantification of carbon (C) allocation through the soil-plant-atmosphere continuum (SPAC) has received increasing attention in recent years. Although advanced imaging and numerical methods have boosted our knowledge, we still lack an experimental and mechanistic understanding of C flux and its partitioning across the SPAC. Here we combined a 13C pulse labeling technique with modeling of C transport across the SPAC to describe the flow of newly assimilated C from shoots to roots, to soils and then respired back to the atmosphere. To do so, different plants - maize (Zea mays L.), soybean (Glycine max (L.) merr. cv. sohae), and wheat (Triticum aestivum L.) - were exposed to a 13CO2 pulse for 2 hoursduring daytime. A CO2 Isotope Analyzer (CCIA-38d-EP, Los Gatos Research) was used to continuously monitor 13CO2 flux from the soils. Subsequently, after harvest the respective 13C contents of shoot and root biomass and of the soil was quantified.

To model the C fluxes, we developed a simple multi-compartment domain, representing the SPAC. The SPAC was envisioned as four interconnected horizontal compartments namely atmosphere, shoots, roots, and soil compartment. The shoots and roots compartment were further simplified in three vertical compartments (phloem, storage, and structural pool). The C transport between these pools was represented by constant rates. These rates were inversely estimated by adjusting the model parameters to best reproduce the measured C flux and C contents in the various compartments.   

Our model described the allocation and transport of 13C within the shoots, roots, and soil well. The best-fitted coefficients of the model were reproducible among different replications of the same plant species. We also checked the sensitivity of our model to its parameters and observed a good sensitivity to most of the model parameters. In particular, our model was very sensitive to C loading and unloading in the phloem and also root exudation rates. The results of our study show that the combination of tracing 13C and modeling of 13C transport across SPAC is a promising tool to study C flux and its partitioning across SPAC.

How to cite: Adamczewski, R., Liu, Q., Pausch, J., and Zarebanadkouki, M.: Modeling the partitioning of assimilated C along the soil-plant-atmosphere continuum based on a 13C labeling experiment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6985, https://doi.org/10.5194/egusphere-egu23-6985, 2023.

Woody plants rely on the remobilization of carbon (C) and nitrogen (N) reserves to support growth and survival when resource demand exceeds supply at seasonally predictable times like spring leaf flush and following unpredictable disturbances like defoliation. Despite their importance, we still have a poor understanding of how reserve remobilization is regulated and whether remobilization and the allocation of mobilized reserves is constrained by distance between source and sink tissues. This leads to uncertainty in which reserves—and how much—are actually available to support plant functions like leaf growth during spring flush or following defoliation. To better understand the source of remobilized reserves and constraints on their allocation, we used stable isotopes (13C,15N) to label C and N reserve pools in aspen (Populus tremuloides Michx.) saplings, and then grafted unlabeled and labelled stems to labelled and unlabeled root stocks, to create organ-specific labelled reserves.  We then tested for differences in reliance on reserves from different organs between 1) upper and lower leaves 2) early and late leaves and 3) early flush and reflush leaves produced after defoliation.  During spring flush, both C and N reserves were preferentially allocated to sinks nearer the reserve source (i.e the roots), but reliance on C reserves was reduced over time.  Additionally, N appeared to be preferentially remobilized from sources closer to the developing leaves.  However, following defoliation, we found that reflush leaves imported the same proportion of N from the roots as spring flush leaves, but that a lower proportion of C was imported from root reserves. The lower import of reserve C suggests reflush leaves must rely more on their own photosynthetic gains to fuel leaf growth, which may explain the reduced total leaf mass of reflush canopies (31% of initial mass).  The reduced import of reserves occurred even though roots retained significant starch reserves (~5% dry wt), suggesting aspen prioritizes the maintenance of root C reserves at the expense of fast canopy recovery.

How to cite: Wiley, E., Hart, A., and Landhäusser, S.: Tracing the origin of imported carbon and nitrogen reserves: remobilization during spring leaf expansion and recovery following defoliation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7551, https://doi.org/10.5194/egusphere-egu23-7551, 2023.

EGU23-8002 | ECS | Orals | BG3.2

Carbon allocation to root exudates in a mature mixed F. sylvatica – P. abies forest under drought and one year after drought release. 

Benjamin D. Hafner, Melanie Brunn, Marie J. Zwetsloot, Kyohsuke Hikino, Fabian Weikl, Karin Pritsch, Emma J. Sayer, Nadine K. Ruehr, and Taryn L. Bauerle

In recent years, important processes controlling ecosystem carbon dynamics have been connected to fine-root exudation of soluble carbon compounds. Root exudation patterns may change depending on plant interactions and plant susceptibility to and recovery from drought. Recent investigations suggest that root exudation tends to increase with stress events, but quantification of the amount of carbon released from roots across soil depths with differing water availability and species interactions are missing.

We tested if root exudation rates were negatively correlated with soil water content across soil depths during and after drought. We further tested if species in mixture, often considered to be less stressed under drought, exuded less carbon than species in monospecific environments. Exudates were sampled in a mature Fagus sylvatica L. and Picea abies (L.) Karst. forest at the end of a five-year throughfall exclusion period and again one year after the drought ended. We quantified root exudates and their variation with soil depth for both tree species in monospecific and mixed species zones.

Carbon exudation significantly increased in fine roots exposed to dry soils (< c. 10vol-% SWC), with fine roots growing in driest surface soils exuding the most. Under drought, the proportion of net assimilated carbon allocated to exudates doubled for F. sylvatica and tripled for P. abies, respectively. One year after drought release, carbon allocation to exudates was not different for F. sylvatica between previously drought stressed and control trees, while the proportion was still significantly increased in previously drought stressed P. abies compared to control trees. This indicates long-term disruptions in carbon allocation patterns even after the end of a drought period in evergreen vs. broadleaved temperate tree species. Both species exuded significantly more carbon when in monoculture than when in a mixed zone, especially in the surface soil layer.

Our results demonstrate that carbon is released preferentially in the surface soil layers exposed to more variable soil water contents and exudation amounts are maintained by allocating bigger proportions of net-assimilated carbon into exudates even among variable carbon assimilation rates throughout periods of drought and re-wetting. In addition, plant interactions significantly influenced root exudation patterns. Further studies are planned to understand if differences in exudate quantity correlate to differences in functioning of released exudates in monospecific and mixed environments by analyzing the chemical profile of the exudate metabolome.

How to cite: Hafner, B. D., Brunn, M., Zwetsloot, M. J., Hikino, K., Weikl, F., Pritsch, K., Sayer, E. J., Ruehr, N. K., and Bauerle, T. L.: Carbon allocation to root exudates in a mature mixed F. sylvatica – P. abies forest under drought and one year after drought release., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8002, https://doi.org/10.5194/egusphere-egu23-8002, 2023.

EGU23-8387 | ECS | Posters on site | BG3.2

Increasing importance of ecosystem respiration for ecosystem carbon exchange dynamics from weekly to interannual timescales 

Nora Linscheid, Miguel D. Mahecha, Anja Rammig, Ana Bastos, Jacob A. Nelson, and Markus Reichstein

 

Vegetation carbon uptake is a major sink for anthropogenic greenhouse gas emissions, yet inferring longer-term behaviour of ecosystems as carbon sinks or sources is still difficult. Here, using a time series decomposition technique and eddy covariance data, we show that while at subseasonal scales net ecosystem CO2 uptake (NEP) is closely related to photosynthetic uptake, there is an increased importance of ecosystem respiration for determining NEP on longer time scales. 

 

The interannual evolution of net ecosystem CO2 uptake (NEP) is insufficiently understood and often not well captured in state-of-the-art vegetation models and data products. This lack of understanding may in part be due to different drivers between interannual and seasonal scales affecting the two terms balancing NEP - photosynthetic uptake of CO2 (GPP) and ecosystem respiration (Reco).

Here, we extract timescale specific carbon flux dynamics at 20 long-running FLUXNET eddy covariance sites (>13 years) using time series decomposition to relate variability in GPP and Reco to NEP at subseasonal to interannual timescales. The results indicate that relations between NEP and GPP or Reco, respectively, are not constant across different timescales, but that GPP and Reco exert differential control on NEP between sub-seasonal, seasonal, and longer timescales.

  • Overall, the fraction of variance in NEP explained by GPP variance is decreased at longer timescales, while the fraction of NEP variance explained by Reco variance and by the covariance of GPP and Reco generally increases at longer timescales.

  • Regarding GPP, we find that the slopes between NEP and GPP, which could be interpreted as scale specific apparent carbon use efficiencies (NEP/GPP) are highest and most consistent at subseasonal scales, while generally smaller in magnitude and less constrained at interannual scales. This indicates that GPP and NEP are generally more strongly and directly linked at the subseasonalscale.

  • Regarding Reco, we find a positive relationship between NEP and Reco at the seasonal scale. This is counterintuitive given NEP = GPP – Reco, but similar to spatial relations in other studies and likely related to GPP seasonality as a common driver. In contrast, the subseasonal and interannual NEP-Reco relations are mostly negative, as would be expected since higher respiratory loss would generally indicate lower ecosystem carbon retention, i.e. lower NEP. 

The timescale specific relations extracted here based on direct ecosystem CO2 exchange measurements suggest an increased importance of ecosystem respiration for long-term carbon source or sink behavior for some ecosystems. These results give insight into ecosystem functioning, as well as demonstrate the utility of time series decomposition as a diagnostic of ecosystem dynamics at different timescales. Such information may eventually serve as a basis to infer turnover times of ecosystem carbon pools and better characterize interannual ecosystem carbon dynamics.

 

How to cite: Linscheid, N., Mahecha, M. D., Rammig, A., Bastos, A., Nelson, J. A., and Reichstein, M.: Increasing importance of ecosystem respiration for ecosystem carbon exchange dynamics from weekly to interannual timescales, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8387, https://doi.org/10.5194/egusphere-egu23-8387, 2023.

EGU23-8562 | ECS | Posters on site | BG3.2

Temporal decoupling between carbon assimilation and tree growth in temperate oaks 

Mukund Palat Rao, Arturo Pacheco-Solana, Kevin Griffin, Johanna Elizabeth Jensen, Neil Pederson, Bar Oryan, Troy Nixon, Milagros Rocio Rodriguez Caton, Laia Andreu Hayles, Jeremy Hise, Josep Peñuelas, and Troy Magney

The ‘growing season’ of trees is often assumed to be coupled with climatology (e.g., summer vs winter) and visual canopy phenology cues (e.g., leaf emergence in spring and senescence in autumn). However, green leaves are not always photosynthetically active and actual tree radial growth via cambial cell division is ‘invisible’ since it is hard to see and occurs at micrometer resolution. Therefore, despite the presence of apparently green vegetation, trees may not be assimilating carbon or growing. Here, we study photosynthesis and tree-growth at near-instantaneous timescales using in-situ and satellite remote sensing, point dendrometers, quantitative wood anatomy, and Pulse Amplitude Modulated chlorophyll fluorescence. Tree and leaf-level measurements are being made on eight oak (Quercus spp.) trees in a temperate forest in southern New York, USA. We find that oak trees commence radial growth in the first week of April approximately one-month prior to canopy development that is not completed until the first week of May. Additionally, the development of foliar photosynthetic capacity lags leaf expansion by nearly two weeks. Further, we find that oak growth for the season is completed by late July while photosynthetic activity is maintained for three additional months until early November. Finally, we examine the growth climate sensitivity across a network of 16 oak tree-ring width chronologies distributed across the northeastern US. These relationships suggest that oak earlywood growth relies on carbon assimilated in prior year autumn while oak latewood relies on current year assimilated carbon. Therefore, photosynthesis and tree-growth in Northeastern US oaks occurs asynchronously, since trees don’t reach peak photosynthetic performance the moment leaves emerge or grow through the ‘growing season’.

How to cite: Rao, M. P., Pacheco-Solana, A., Griffin, K., Jensen, J. E., Pederson, N., Oryan, B., Nixon, T., Rodriguez Caton, M. R., Andreu Hayles, L., Hise, J., Peñuelas, J., and Magney, T.: Temporal decoupling between carbon assimilation and tree growth in temperate oaks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8562, https://doi.org/10.5194/egusphere-egu23-8562, 2023.

Herbaceous dominated ecosystems are found throughout the world representing a wide variety of locations that differ in their mean annual precipitation, annual temperature ranges, light availability, and soil nutrient concentrations. This is reflected in a wide range of annual above- and belowground biomass production, plant diversity and canopy density between these ecosystems worldwide. Our study aims to understand how nutrient availability and disturbance impact species relative abundance, diversity, and annual aboveground production. Here, we present background data on herbaceous dominated ecosystems found in coastal South Carolina, USA that are part of a global network (DragNet) of herbaceous dominated ecosystem study sites distributed across the world. Dominated by both grass species and forbs, we found that within a site, there is variation in the relationship between species diversity and biomass production. Aboveground biomass and accumulated litter are not correlated suggesting that the drivers for carbon assimilation and decomposition are different. This research will serve as the foundation for future research on how nutrients and soil disturbance interact with the amount of carbon assimilation and if some species show trait variation in response to these treatments in different regions of the world.

How to cite: O'Halloran, L.: Aboveground biomass production and litter accumulation in coastal grassland ecosystems: the basis of a global study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10322, https://doi.org/10.5194/egusphere-egu23-10322, 2023.

EGU23-11020 | ECS | Posters on site | BG3.2

The relative importance of grassed alleys in C dynamics of open-canopy vineyards 

Torben Oliver Callesen, Leonardo Montagnani, Carina Verónica Gonzales, Flávio Bastos Campos, Massimo Tagliavini, and Damiano Zanotelli

Vineyards have the potential to act as potential carbon sinks due to various characteristics such as low soil disturbance, high biodiversity and long-term carbon reservoirs. In mountainous regions where soil stability and erosion are priorities, grassed alleys are essential to vineyard management. Cover cropping is also frequently employed to improve soil quality and provide various ecosystem services. Among them, these practices are generally considered to have a positive impact on carbon sequestration, although there is still debate over the extent of this. Disentangling the carbon fluxes of grapevines and resident herbaceous vegetation as well as the in-plant allocation is essential for understanding the effects of management decisions and environmental conditions on the fate of sequestered carbon.

To this end, we conducted continuous carbon flux measurements over the growing season of 2021 (15 April – 15 November) using an eddy covariance tower mounted in a grassed and irrigated hillside vineyard in Alto Adige, Italy. The cultivars present were Chardonnay and Sauvingon blanc on SO4 rootstock (average density: 6500 vines ha -1) and the vines were trained in a vertical shoot position manner with Guyot pruning. Eddy covariance measurements were complemented with surveys using soil respiration chambers and biometric measurements of net primary production (NPP).

Results showed that the seasonal gross primary production (GPP) of the vineyard was very high (2409 ± 35 g C m-2) relative to other studies, but was closely matched by the carbon lost as respiration (Reco; 2163 ± 88 g C m-2), of which the majority originated from the soil. The resulting carbon accumulation during the season (NEP, net ecosystem production; 246 ± 54 g C m-2) was moderate, and a large portion was accounted for by the berries exported after harvest. The grassed alleys played an important role carbon assimilation, accounting for roughly half of the above-ground vegetative growth for the season. 25% of the final carbon storage was attributed to the growth of permanent grapevine organs. Periods of summer heat in combination with relatively long absences of rain occurred, during which the NEP decreased and drought stress was observed in the grass cover but not the grapevines.

In comparison with other studies reported in literature, the patterns of observed ecosystem fluxes of our site more closely resembled managed grasslands in the area than forests or other vineyards, possibly due to the open structure of the canopy, which may differ between vineyard training systems. However, literature suggests that the biomass produced by the grasses is more easily decomposed than the grapevine leaf litter and pruning material, so although the ground cover accounts for a large portion of the carbon accumulated, we speculate that it contributes proportionally less to long-term storage by increasing soil organic carbon. Therefore, while changing climate conditions may adversely affect the short-term carbon sequestration of vineyards, they are likely to have less of an impact on long-term accumulation attributable to grapevines.

How to cite: Callesen, T. O., Montagnani, L., Gonzales, C. V., Bastos Campos, F., Tagliavini, M., and Zanotelli, D.: The relative importance of grassed alleys in C dynamics of open-canopy vineyards, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11020, https://doi.org/10.5194/egusphere-egu23-11020, 2023.

EGU23-11113 | ECS | Orals | BG3.2 | Highlight

A novel mechanistic boreal forest model with dynamical carbon allocation to quantify climate mitigation potential of management scenarios 

Holger Metzler, Samuli Launiainen, and Giulia Vico

Boreal forests have enormous potential to mitigate climate change by taking up and holding back carbon (C) from the atmosphere, but often they are managed to maximize wood productivity. To achieve regional and global climate goals, boreal forest management must consider trade-offs between wood productivity and potential climate change mitigation. Quantifying forests' climate change mitigation potentials requires knowledge of both the amount of C fixed from the atmosphere and how long trees and subsequently soil and wood products withhold it from the atmosphere (C transit time). Despite its importance for climate change mitigation, transit time is often overlooked when focusing on climate change mitigation potential.

We developed a novel mass-balanced and process-based compartmental forest management model comprising trees of different ages and species in a single stand. The model follows the C path from photosynthetical fixation to return to the atmosphere by autotrophic or heterotrophic respiration or by wood-product burning. The fixed C is allocated to different tree organs according to dynamically changing allometries derived from site- and species-specific forest inventory data and affected by the tree's physiological state (healthy or stressed). The compartmental model structure and its mathematical description as a system of ordinary differential equations enable computing stored nonstructural C age as well as age and provenance of C used for tissue growth and respiration. Furthermore, the dynamical implementation of nonstructural C provides a measure of the forest stands' resilience to stressors and a mechanism for tree mortality .

We apply the model to even-aged pure Scots pine and Norway spruce stands as well as to an even-aged mixed-species stand and to a mixed-aged pine stand, under conditions for southern Finland. We compute: 1) wood productivity as the amount of C in harvested wood products, 2) the net balance of C in trees, soil, and wood products, and 3) the amount of fixed C together with its transit time - a key metric to assess climate change mitigation potential. Different metrics entail different conclusions regarding the most beneficial stand structure and management strategy. Even-aged stand management strategies provide more long-lasting wood products than the mixed-aged stand, and the same amount of short-lasting and long-lasting wood products combined. Furthermore, they have substantially better net C balance afters an 80-years rotation. However, it takes them about 40 years to regain the C lost at initial clear cut. Considering also the transit time of C, the even-aged strategies need almost the entire rotation to offset early clear-cut related C losses. While C sequestration assessed by the net C balance evaluates even-aged strategies as beneficial, a trade-off emerges between considering long-lasting wood products and climate change mitigation potential when taking the C transit time into account.

These results show the importance of considering the transit time in the assessment of forest management strategies and highlight that clear-cut based, even-aged management strategies on stand level undermine climate goals on regional and global scale.

How to cite: Metzler, H., Launiainen, S., and Vico, G.: A novel mechanistic boreal forest model with dynamical carbon allocation to quantify climate mitigation potential of management scenarios, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11113, https://doi.org/10.5194/egusphere-egu23-11113, 2023.

EGU23-12082 | Posters on site | BG3.2

Influence of gross primary productivity and soil carbon content on soil CO2 efflux in dry grasslands 

János Balogh, Szilvia Fóti, Giulia de Luca, Ádám Mészáros, Krisztina Pintér, and Zoltán Nagy

Soil respiration of grasslands is highly variable both in time and space reflecting the topographic characteristics, the changing environmental constrains and biological activity of the vegetation. The aim of this study was to describe the effect of gross primary productivity (GPP) and soil organic carbon content (SOC) on soil respiration under varying environmental conditions in a dry grassland site in Hungary. We made spatially explicit measurements of variables including soil respiration, aboveground biomass, green vegetation index, soil water content, and soil temperature during an 8-year study in the vegetation periods. Sampling was conducted 23 times in 80 x 60 m grids of 10 m resolution with 78 sampling points. Altitude, slope, and soil organic carbon were used as background factors at each sampling position. Site-level GPP data were derived from eddy-covariance measurements and used for the estimation of GPP at every sampling position as a weighted metric on the basis of the biomass and green vegetation index of the positions. Data were analyzed using generalized additive models (GAM). Spatially, soil respiration had negative correlation with soil temperature, altitude and slope, while it was positively correlated with soil water content, aboveground biomass, green vegetation index and SOC. Soil respiration was significantly different between SOC groups (low-medium-high carbon content), mean soil respiration increased with soil carbon content. According to the GAM analysis, the shape of the GPP response was almost linear in each SOC groups and GPP had a strong influence on soil respiration in all of the groups besides temperature and soil water content. The results suggest that GPP and the resulting belowground carbon allocation affecting mainly the autotrophic components of soil respiration have similar influence on soil respiration as the main environmental variables.

How to cite: Balogh, J., Fóti, S., de Luca, G., Mészáros, Á., Pintér, K., and Nagy, Z.: Influence of gross primary productivity and soil carbon content on soil CO2 efflux in dry grasslands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12082, https://doi.org/10.5194/egusphere-egu23-12082, 2023.

EGU23-13571 | ECS | Orals | BG3.2

Carbon allocation in banana plants – the effects of drought stress and suckers 

Mathilde Vantyghem, Eline Beelen, Rebecca Hood-Nowotny, Roel Merckx, and Gerd Dercon

Banana is a perennial crop that propagates vegetatively through the formation of so-called suckers. Suckers are photosynthetically active, but remain connected to the mother plant. Their initial formation is driven by a carbon flux from the mother plant, but it is not known to which extent this flux persists once the sucker develops further. Drought stress is one of the most important limitations to banana production. Nonetheless, the effect of drought stress on the integrated system of mother plant and suckers remains unknown. In a greenhouse experiment, we aimed to quantify carbon fluxes in banana plants and assess the effects of drought stress and suckers on carbon allocation. We labeled banana mother plants with and without suckers with 13CO2, while the suckers were sealed gas tight. An optimal and suboptimal watering treatment were applied. The label was then traced in the phloem sap, in the leaves of mother plant and sucker and in the underground corm for a period of two weeks. Most of the label was either lost through respiration (37.5 ± 3.0 %) or allocated to the mother plant leaves (35.6 ± 2.2 %). Plants without suckers did not invest more in the growing mother plant, but instead, had higher respiratory losses. In plants with suckers, 3.1 ± 0.7 % of 13C assimilated by the mother plant was translocated to the sucker. Drought stress reduced the allocation to the sucker. On average, 5.8 ± 0.4 % of the label ended up in the corm, which connects all leaves and plant parts but also serves as a storage organ, by accumulating starch. Both drought stress and sucker presence increased overall translocation to the corm. Starch accumulation also increased under drought stress or in the presence of a sucker. However, when drought stress and a sucker were both present, starch accumulation was severely reduced. Finally, 17.2 ± 1.1 % of the label ended up in the wrapped leaf sheaths of the mother plant, that form the structurally important pseudostem. The pseudostem as well serves as a source of carbohydrates for future fruit and sucker development. Sucker presence increased carbon allocation to the pseudostem. In conclusion, it seems that suckers and drought stress affected carbon dynamics in banana plants similarly, namely by increasing carbon allocation to storage tissues. Their combination, however, resulted in an imbalance between carbon supply and demand and hence the plants’ investment in sucker growth, as well as in long-term storage were reduced.

How to cite: Vantyghem, M., Beelen, E., Hood-Nowotny, R., Merckx, R., and Dercon, G.: Carbon allocation in banana plants – the effects of drought stress and suckers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13571, https://doi.org/10.5194/egusphere-egu23-13571, 2023.

EGU23-13662 | ECS | Posters on site | BG3.2

Dynamics of mycorrhizal respiration in relation to GPP in a Central-Hungarian dry grassland 

Giulia De Luca, Marianna Papp, Szilvia Fóti, Krisztina Pintér, Ádám Mészáros, Zoltán Nagy, and János Balogh

Soil respiration is a highly complex process including a wide range of soil biota (autotrophic and heterotrophic functioning) and different pathways of carbon cycling (decomposition, arbon allocation), all being under the control of environmental and biotic drivers. The most important biotic driver is the photosynthetic activity of the vegetation providing supply mainly for the autotrophic component of soil respiration: plant roots and their symbiotic partners - such as arbuscular mycorrhizal fungi (AMF). By acting as a source of CO2 and a pathway of carbon to the SOM, the role of AMF in carbon balance is unquestionable, not to mention that mycorrhizal C allocation could determine the long-term C storage potential of an ecosystem.

The objective of this study was to describe the time-lagged relationship between gross primary production (GPP) and the mycorrhizal soil respiration component, so to determine the amount of carbon derived from GPP appearing as mycorrhizal mycelial respiration. Measurements of CO2 efflux were conducted in three different treatments – i) undisturbed, root and AMF-included (Rs), ii) root-excluded (Rbasal + myc) and iii) root- and AMF-excluded (Rbasal) plots – for three consecutive years in a Central-Hungarian dry sandy grassland between July 2011 and May 2014. GPP data were derived from eddy-covariance (EC) measurements, while an automated soil respiration system (SRS) consisting of ten chambers was used for continuous and long-term measurement of soil CO2 efflux. We analysed the relationship between mycorrhizal mycelial respiration and GPP by using cross-correlation and GAMs (generalized additive models). Besides, we used sine wave models to describe the diel pattern of basal and mycorrhizal fungi respiration in the soil together with the diel patterns of soil temperature and GPP.

Considering the whole dataset correlation between GPP and mycorrhizal fungi respiration was highest at 13.5 hours time lag, while the average difference between peak timing of mycorrhizal fungi respiration and peak timing of GPP was 15 hours. However, the time lag and the peak timing difference varied from 10-24 hours. According to the results, carbon allocation to mycorrhizal fungi is a fast process in dry grasslands and the main driver of this respiration component is the GPP.

How to cite: De Luca, G., Papp, M., Fóti, S., Pintér, K., Mészáros, Á., Nagy, Z., and Balogh, J.: Dynamics of mycorrhizal respiration in relation to GPP in a Central-Hungarian dry grassland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13662, https://doi.org/10.5194/egusphere-egu23-13662, 2023.

EGU23-13892 | ECS | Posters on site | BG3.2 | Highlight

Plant water use strategies drive the fate of newly fixed carbon in an experimental rainforest under drought 

Jianbei Huang, Nemiah Ladd, Laura Meredith, Christiane Werner, and Marco Lehmann and the the coauthors

Nonstructural carbohydrates (NSCs) play a crucial role in plant functioning and survival. Nonetheless, substantial knowledge gaps remain regarding NSC mobilization and transport in forests experiencing more frequent extreme droughts. We combined drought manipulation and 13CO2 pulse-labeling in an enclosed rainforest, and assessed changes in tissue NSC content and allocation of recent photosynthates in eight species that represent ecosystem biomass and cover different positions and hydraulic strategies. Drought reduced starch in leaves but not in stem phloem and roots across species. However, soluble sugars remained constant or increased in understory plants and anisohydric trees, and decreased only in leaves of isohydric trees with relatively constant leaf water potential and sap flow. Drought slowed export and transport of recent photosynthates, not only for anisohydric species with a strong decrease in leaf water potential and sap flow but also for isohydric species with a strong decrease in photosynthetic supply and carbohydrate levels.  We provide evidence that tropical plants under drought mobilize starch to buffer carbon deficiency, while regulating local utilization, export and transport of soluble sugars depending on position and isohydricity. We highlight the importance of plant functional types for understanding NSC dynamics and their role in determining forest carbon balance under drought. 

How to cite: Huang, J., Ladd, N., Meredith, L., Werner, C., and Lehmann, M. and the the coauthors: Plant water use strategies drive the fate of newly fixed carbon in an experimental rainforest under drought, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13892, https://doi.org/10.5194/egusphere-egu23-13892, 2023.

EGU23-13912 | ECS | Orals | BG3.2

Incorporating nonstructural carbohydrate dynamics in the ISBA biomass allocation scheme 

Jan De Pue, José Miguel Barrios, Alirio Arboleda, Rafiq Hamdi, Manuela Balzarolo, Fabienne Maignan, Christine Delire, Ivan Janssens, and Françoise Gellens-Meulenberghs

Within land surface models (LSM), the biomass allocation scheme (BAS) allows to simulate the dynamics of vegetation growth in response to climatic variation and other drivers. It distributes the assimilated carbon across different biomass pools, and consequently determines the spatio-temporal variability of the leaf area index (LAI).

In many LSM, large uncertainties are associated with the BAS, which propagate via the prognostic LAI to the surface fluxes. Here, we propose a revision to the BAS of the ISBA land surface model, by incorporating the dynamics of non-structural carbohydrates (NSC) explicitly. The target of the proposed BAS is the reproduction of LAI as observed with remote sensing, coupled to the modelled surface fluxes. Using in situ eddy covariance observations of the carbon fluxes, and remote sensing observations of the leaf biomass, estimates can be made of the biomass allocation and NSC dynamics. By combining this dataset with other (climatological) variables, a machine-learning based BAS is developed.

The simulated evolution of the biomass pools is evaluated using in situ observations of leaf turnover and remote sensing observations of leaf biomass. The proposed model is compared to the standard photosynthesis-driven BAS of ISBA and the more advanced BAS in ORCHIDEE.

How to cite: De Pue, J., Barrios, J. M., Arboleda, A., Hamdi, R., Balzarolo, M., Maignan, F., Delire, C., Janssens, I., and Gellens-Meulenberghs, F.: Incorporating nonstructural carbohydrate dynamics in the ISBA biomass allocation scheme, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13912, https://doi.org/10.5194/egusphere-egu23-13912, 2023.

EGU23-1175 | ECS | Orals | BG3.3

Diverse responses of multiple crops to drought and salinity stress  

Wen Wen, Joris Timmermans, Qi Chen, and Peter M. van Bodegom

Food security is threatened by co-occurring stresses (e.g. salinity and drought) under global climate change. To circumvent major impacts on food production, the vulnerabilities and tolerances to these threats need to be characterized. Traditionally, the tolerance of crops is evaluated in highly controlled small-scale experiments involving only a limited number of crop types. To increase our understanding in actual agricultural tolerances, plant functioning, as observed by functional traits, need to be performed in real-life scenarios for as many crops as possible. Remote sensing is presently the only tool capable of monitoring such plant functional traits simultaneously over large areas.

The aim of this research therefore is to evaluate the crop tolerances to combined drought and salinity stress across various plant functions in real-life conditions. We evaluated drought and salinity tolerance impacts on different types of crops across the entire US continent, using five traits representative of different plant functions. Given crop tolerance highly depended on the moments, we evaluated the dominant stress and the onset among individual and combined effects of drought and salinity for five traits from March to October.

We found strong interaction effects between stress and time using two-way ANOVAs. In general, crops were more sensitive to combined drought and salinity, although they differ significantly between species and moments. Of the individual traits, LAI was triggered first by stresses, followed by FAPAR and FVC, and Cab and Cw were the last to respond to stresses. This implies that plants reduce primary production before reducing water content.

Our study provides a way of evaluating the tolerance of diverse crops to co-occurrence stresses both separately and in combination. Through applications to other vegetation types and stresses, our approach creates a quantitative backbone to inform sustainable food production.

How to cite: Wen, W., Timmermans, J., Chen, Q., and van Bodegom, P. M.: Diverse responses of multiple crops to drought and salinity stress , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1175, https://doi.org/10.5194/egusphere-egu23-1175, 2023.

EGU23-3743 | Posters on site | BG3.3

Developing Tailored Agro-met Predictions for Target Cropping Systems in Vanuatu: tailOred System of Climate services for AgRiculutre (OSCAR) 

Jong Ahn Chun, Sugyeong Park, Imgook Jung, Seongkyu Lee, and Kyungwon Park

Vanuatu as one of Small Island Developing States (SIDS) in the Pacific region is one of the most vulnerable countries to climate impacts including climate-related natural disasters. In order to build the adaptive capacity of vulnerable communities and users of climate information and services. The Climate Information Services for Resilient Development Planning in Vanuatu (Van-CISRDP; Vanuatu Klaemet Infomesen blong Redy, Adapt mo Protekt (Van-KIRAP) in Bislama) project was approved at the Green Climate Fund (GCF) 15th meeting of the board in Apia, Samoa in December 2016 (FP 035). The two implementing entities: Secretariat of the Pacific Environment Program (SPREP) and Geo-Hazard Department (VMGD) and three delivery partners:  APEC Climate Center (APCC), Commonwealth Scientific and Industrial Research Organization (CSIRO) and Australia Bureau of Meteorology are collaboratively conducted the Van-KIRAP project. In the Van-KIRAP project, the major activities of APCC consist of (1) Develop Agro met information portal including new on line IT infrastructure and software (OSCAR prototype), (2) Collecting, modelling, analysis and reporting of agro-met data to determine optimal agriculture crop planning options, (3) Undertaking field trials and validation prior to incorporation into DSS delivery platforms, ground truthing and outreach with target Next/End Users, and (4) Develop the crop-climate diary (CCD) customised for agro-met data collection. In this presentation, we will introduce the APCC portion of the Van-KIRAP project including experimental field trials for major staple crops, various training and education programs in both on-line and on-site, and the development of the OSCAR system incorporating various Artificial Intelligence techniques and modelling approaches. These will provide relevant climate information applied to the agriculture sector. The CCD will serve as a tool to collect data in an efficient streamlined manner from different areas of Vanuatu. Utilizing the data from CCD, OSCAR will be a hub for the interaction of climate information and agriculture.

How to cite: Chun, J. A., Park, S., Jung, I., Lee, S., and Park, K.: Developing Tailored Agro-met Predictions for Target Cropping Systems in Vanuatu: tailOred System of Climate services for AgRiculutre (OSCAR), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3743, https://doi.org/10.5194/egusphere-egu23-3743, 2023.

Agricultural lands provide a near-term opportunity to address climate change, food, and water security challenges. Addressing these complex challenges will require the integration of empirical data on the natural variation of vegetation traits with computational approaches that can integrate this empirical information toward an understanding of canopy-scale impacts. The relationships between leaf chlorophyll content, leaf optical properties, and biochemical photosynthetic capacity were measured in a collection of soybean (Glycine max) accessions showing large variations in leaf chlorophyll content (Chl). These relationships were integrated into a biophysical model of canopy-scale photosynthesis to simulate the within-canopy light environment, carbon dioxide assimilation and water use. Simulations were conducted for each accession to identify possible opportunities for improving canopy photosynthesis through foliar chlorophyll modification. These simulations demonstrate that canopy photosynthesis may not increase as Chl is reduced due to increases in leaf reflectance and nonoptimal distribution of canopy nitrogen. However, similar rates of canopy photosynthesis can be maintained with a 9% savings in leaf nitrogen resulting from decreased Chl. Additionally, analysis of these simulations indicates that the inability of Chl reductions to increase photosynthesis arises primarily from the connection between Chl and leaf reflectance and secondarily from the mismatch between the vertical distribution of leaf nitrogen and the light absorption profile. These simulations motivated the use of numerical optimization to quantify the extent to which low Chl mutations can be used to improve canopy performance by adapting the distribution of the “saved” nitrogen within the canopy to take greater advantage of the more deeply penetrating light. We conclude with a discussion of the impact of the re-distribution of nitrogen vertically through the canopy to improve photosynthesis and canopy water use.

How to cite: Drewry, D.: Simulating the field-scale potential of natural variation in soybean leaf optical properties on carbon assimilation and water use, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4045, https://doi.org/10.5194/egusphere-egu23-4045, 2023.

EGU23-5633 | ECS | Orals | BG3.3

From tree-tip to trunk-base: interplay of resistance to embolism formation and wood anatomy in two conifers 

Tadeja Savi, Dario Zambonini, Khristina Zagudaeva, Sabine Rosner, and Giai Petit

Efficient and safe water transport in plants depends on specific wood anatomical structures. Comparing the hydraulic vulnerability among tree species and individuals can be biased by differences in the sampling procedure resulting in unjustified conclusions. In fact, water-transporting conduits of the xylem widen from the tree-tip toward the base potentially influencing xylem vulnerability to embolism formation.

The resistance to cavitation and embolism formation (hydraulic vulnerability curves) was empirically tested at different positions from the tree-tip to the trunk base in a mature Norway spruce and a silver fir tree. Anatomical analyses (conduit diameter, pit traits) were performed on the same material used for hydraulic measurements.

Substantial intra-plant variation in xylem anatomy and vulnerability to embolism was observed in both species scaling with the distance from the apex. The P50 values (i.e. the water potential resulting in 50% loss of hydraulic conductivity) were about 3 MPa more negative at the tip than at the trunk base. Tracheid diameters and pit dimensions increased from the apex downwards, confirming the tip-to-base conduit widening. The highest variability of both anatomical and physiological traits was observed within the first 3 m from the apex. We propose a method for the prediction of drought vulnerability based on hydraulically weighed conduit diameter distribution.

A clear pattern of anatomical traits’ variation along the longitudinal axes of the tree was observed, likely playing a role in the increase of vulnerability to embolism. In comparative studies, we thus recommend to standardize the sampling of material according to the distance from the apex.

How to cite: Savi, T., Zambonini, D., Zagudaeva, K., Rosner, S., and Petit, G.: From tree-tip to trunk-base: interplay of resistance to embolism formation and wood anatomy in two conifers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5633, https://doi.org/10.5194/egusphere-egu23-5633, 2023.

EGU23-6187 | ECS | Orals | BG3.3

Species richness and drought-tolerance traits explain opposing tree growth and δ13C responses to climate extremes 

Florian Schnabel, Kathryn E. Barry, Susanne Eckhardt, Joannès Guillemot, Heike Geilmann, Anja Kahl, Heiko Moossen, Jürgen Bauhus, and Christian Wirth

The increasing occurrence and intensity of climate extremes, such as droughts, threaten forests and the many services they provide to society. Mixed-species forests are promoted as a forest management strategy for climate change adaptation, but whether they are generally more resistant to drought than monospecific forests remains unresolved. Particularly, the trait-based mechanisms driving tree resistance to drought remain elusive, making it difficult to predict which functional identities of species best improve tree growth and decrease tree physiological water stress under drought.

Here, we investigated tree growth and physiological stress responses (i.e. increase in wood carbon isotopic ratio; δ13C) to changes in climate-induced water availability (wet-to-dry years) along gradients in neighbourhood tree species richness and drought-tolerance traits. For this purpose, we sampled tree cores in a large-scale forest biodiversity experiment (BEF-China experiment). We tested the overarching hypothesis that neighbourhood species richness increases growth and decreases δ13C. We further hypothesized that the abiotic (i.e. climatic conditions) and the biotic context modulate these biodiversity-ecosystem functioning relationships. We characterized the biotic context using drought-tolerance traits of focal trees and their neighbours. These traits are related to cavitation resistance vs. resource acquisition and stomatal control.

We found that tree growth increased with neighbourhood species richness. However, we did not observe a universal relief of water stress in species-rich neighbourhoods, nor an increase in the strength of the relationship between richness and growth and between richness and δ13C from wet-to-dry years. Instead, these relationships depended on both the traits of the focal trees and their neighbours. At either end of the resistance-acquisition and stomatal control trait gradient, species responded in opposing directions during drought and non-drought years.

We report that the biotic context can determine the nature of biodiversity-ecosystem functioning relationships in experimental tree communities. We derive two key conclusions: (1) drought-tolerance traits of focal trees and their neighbours can explain divergent tree responses to drought and diversity, and (2) contrasting, trait-driven responses of tree species to wet vs dry climatic conditions can promote forest community stability. Mixing tree species with a range of drought-tolerance traits may therefore increase forest productivity and stability but may not universally relieve drought stress.

How to cite: Schnabel, F., Barry, K. E., Eckhardt, S., Guillemot, J., Geilmann, H., Kahl, A., Moossen, H., Bauhus, J., and Wirth, C.: Species richness and drought-tolerance traits explain opposing tree growth and δ13C responses to climate extremes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6187, https://doi.org/10.5194/egusphere-egu23-6187, 2023.

EGU23-7239 | ECS | Posters on site | BG3.3

The study of morpho-anatomical and biochemical traits on irradiated microgreens to unlock crop potential in Space  

Chiara Amitrano, Sara De Francesco, Walter Tinganelli, Marco Durante, Ermenegilda Vitale, Carmen Arena, and Veronica De Micco

In the upcoming years, agriculture will have a central role not only in feeding a growing population worldwide, but also in Space-related research, through the implementation of protected cultivation systems. To make it possible, it is fundamental to understand plants’ ability to cope with a dynamic environment, made worst by harsh Space conditions including microgravity and ionizing radiation.

Plant plasticity in adaptation relies on the development of both structural and physiological traits, which are deeply influenced by the environment; therefore, leaf morpho-anatomical traits are critical for balancing plant water and CO2 exchange and determine the efficiency of CO2 diffusion within the mesophyll. Their relationship has been widely studied; however, it remains unclear at what extent leaf anatomical traits may drive leaf hydraulic and photosynthetic acclimation to Space environmental stressors.

Previous studies have proven that ionizing radiation can induce positive, null or negative effects depending on the radiation type, dose and exposure (acute or chronic) as well as plant developmental stage and species.

In this study, we compared functional, anatomical (e.g., leaf area, leaf dry matter content, leaf mass per area, stomatal and vein size and density, mesophyll organization, chloroplast distribution) and biochemical traits (e.g. chlorophyll and carotenoids content, polyphenols, ascorbic acid) of brassica microgreens (Brassica rapa L. subsp. sylvestris var. esculenta) exposed to three different types of radiation (X-rays, Carbon ion 12C, Iron ion 56Fe) at the same doses (0-control, 0.3, 1, 10, 20, and 25 Gy). Irradiation took place at the GSI Helmholtzzentrum für Schwerionenforschung GmbH, and then microgreens were cultivated in a growth chamber under controlled condition. Microgreens were chosen as study model for two main reasons. First, microgreens are good candidates for the diet integration of astronauts because they are rich in nutraceutical compounds and can be cultivated directly in Space with very low input resources. From a fundamental science viewpoint, understanding the morpho-functional responses of microgreens is needed because at this stage of development plants are very vulnerable: overcoming the microgreens stage may represent a bottleneck in the cultivation of adult plants in bioregenerative life support systems.

The results suggest the different radiation type and doses determined alterations in morpo-anatomical and biochemical traits which may determine the limits of crop responses and biomass production. These findings should be considered when studying plant adaptation to Space environment, trying to optimize plant growth in controlled environment to achieve the sustainability of the system.

 

Part of the results presented here is based on the experiment Bio_08_DeMicco, which was performed at the SIS18 at the GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany) in the frame of FAIR Phase-0. 

How to cite: Amitrano, C., De Francesco, S., Tinganelli, W., Durante, M., Vitale, E., Arena, C., and De Micco, V.: The study of morpho-anatomical and biochemical traits on irradiated microgreens to unlock crop potential in Space , EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7239, https://doi.org/10.5194/egusphere-egu23-7239, 2023.

EGU23-7999 | ECS | Orals | BG3.3

Drought response behavior of risk-taking and conserving spring barley cultivars 

Mercy Appiah, Issaka Abdulai, Elvira S. Dewi, Agata Daszkowska-Golec, Gennady Bracho-Mujica, Alan Schulman, Menachem Moshelion, and Reimund P. Rötter

Breeding drought resilient crops requires understanding the mechanisms underlying plant physiological responses to different drought patterns and how these vary within species.Two main plant water use strategies are distinguished in the literature, referred to as “risk – taking” (anisohydric) and “conserving” (isohydric). Under well-watered conditions, risk takers exhibit a higher transpiration rate (TR) associated with a greater CO2 assimilation rate, and hence, greater dry matter production than conserving plants which have a tighter stomatal control. Depending on the root traits the transpiration-limiting soil moisture level (θcrit) can differ between plants with similar shoot traits. A high θcrit (e.g. due to shallow roots) entails early stomata closure. This study aimed at examining the drought response of four high-yielding European spring barley cultivars considered to exhibit different response behavior.

We collected detailed plant physiological data with a high- throughput functional phenotyping platform (Plantarray®, Plant-Ditech) and analyzed final yield parameters. Around flowering cv. Chanelle (CHAN), RGT Planet (RGT), Formula (FORM), and Baroness (BAR) were exposed to 12 days of drought. Based on higher TR, higher biomass and grain yield under well-watered conditions and the faster TR reduction below θcrit ,CHAN ranked as very risk taking and RGT as risk taking in contrast to conserving FORM and very conserving BAR.

Drought effects on final yield are closely linked to the plants recovery potential, i.e. the ability to increase TR to control plant levels upon re-irrigation. The highest yielding cultivar under ample water supply, CHAN, showed a significantly impaired recovery potential and suffered notable yield penalties under drought (24%). The very conserving response behavior of BAR resulted in good recovery, minimal yield loss (-2% yield) and a final grain yield that was almost similar to very risk taking CHAN (Δ 5g/pot). FORM produced the lowest yields under control and stress conditions yet suffered no drought induced yield penalties, probably due to a better adapted root system. The lower θcrit of FORM delayed stomata closure and the breakdown of assimilation. FORM and RGT had similar recovery rates.

RGT produced the second highest yield under well-watered conditions and drought did not cause any yield losses. Under ample water supply, RGT behaved like a risk taker, whereby the high TR allowed it to be more productive than the conserving cultivars. RGT switched to a more conserving behavior under drought where it only gradually (same slope as FORM) decreased TR below θcrit and was thereby more productive than very risk taking CHAN. This rather dynamic water use behavior made RGT the best performing cultivar in the here examined drought scenario.

A higher number of seeds per spike (along with reduced kernel size) likely contributed to the yield stability observed under drought in FORM and RGT the exact physiological mechanisms of which still require more investigation. Prospective studies will examine different drought patterns and durations and implement the gained knowledge into crop simulation models for upscaling.

 

Keywords: water-response behavior, isohydric; anisohydric; spring barley, drought

How to cite: Appiah, M., Abdulai, I., Dewi, E. S., Daszkowska-Golec, A., Bracho-Mujica, G., Schulman, A., Moshelion, M., and Rötter, R. P.: Drought response behavior of risk-taking and conserving spring barley cultivars, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7999, https://doi.org/10.5194/egusphere-egu23-7999, 2023.

EGU23-8395 | ECS | Orals | BG3.3

Morpho-anatomical and biochemical modifications in Lactuca sativa L. plants in response to increasing doses of High-LET ionizing radiation 

Sara De Francesco, Chiara Amitrano, Walter Tinganelli, Marco Durante, Stefania De Pascale, Carmen Arena, and Veronica De Micco

The presence of unique environmental factors such as ionizing radiation (IR) in Space may be a major hindrance to the survival of terrestrial organisms. Therefore, understanding the impact of Space radiation on organisms is an essential part of exploration research to successfully inhabit Moon and Mars.

Given the pivotal role of plants in sustainable closed artificial ecosystems in Space (i.e. Bioregenerative Life Support Systems) as food producers and bio-regenerators of environmental resources such as oxygen and water, and, plant resistance to IR is undoubtedly one of the first trait to consider. Indeed, IR may influence plants growth and development, potentially affecting their bioregenerative performance, jeopardizing astronaut survival and in turn the success of future Space missions. Notwithstanding, available information on plants' responses to IR remain unclear, and intrinsic IR and plant factors (e.g., type of radiation, dose, plant species, cultivar, and developmental stage at the time of irradiation) interactions must be considered.

The purpose of this study was to test the radio resistance of the Salanova® lettuce (Lactuca sativa L. var. capitata) to different doses of high-LET (Linear Energy Transfer) radiation, in terms of morpho-anatomical and nutritional traits. At the GSI Helmholtzzentrum für Schwerionenforschung GmbH, dry seeds were exposed to increasing doses (0-control, 0.3, 1, 10, 20, and 25 Gy) of iron ions (56Fe) (one of the most damaging ions in the galactic cosmic ray spectrum). Following irradiation, plants were grown in a growth chamber under controlled light, temperature, and relative humidity conditions.

Seed germination percentage, as well as plant growth and leaf photosynthesis performances were monitored during cultivation.

Morpho-biometric parameters such as plant total leaf area, number of leaves, and fresh and dry biomass were quantified at harvest. Leaf functional anatomical traits (e.g., lamina thickness, stomatal frequency and size, vein density) were also analyzed using light and epifluorescence microscopy and digital image analysis. Finally, to assess the phytochemical and nutritional profile, the antioxidant capacity, chlorophylls, carotenoid, and mineral composition content were determined.

Results showed that responses of Salanova lettuce from irradiated seeds changed depending on the IR dose delivered, with the occurrence of both hormetic and detrimental outcomes, as well as possible plant radioprotective strategies. This information will be helpful to unveil the mechanisms behind plant radiotolerance and to define the shielding requirements for Space cultivation facilities.

Part of the results presented here is based on the experiment Bio_08_DeMicco, which was performed at the SIS18 at the GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany) in the frame of FAIR Phase-0.

How to cite: De Francesco, S., Amitrano, C., Tinganelli, W., Durante, M., De Pascale, S., Arena, C., and De Micco, V.: Morpho-anatomical and biochemical modifications in Lactuca sativa L. plants in response to increasing doses of High-LET ionizing radiation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8395, https://doi.org/10.5194/egusphere-egu23-8395, 2023.

EGU23-9556 | ECS | Orals | BG3.3

Biostimulant applications to mitigate multiple summer stress effects on potted Corylus avellana L. young plants 

Lucia Vanacore, Giuseppe Carlo Modarelli, Christophe El-Nakhel, Antonio Pannico, Youssef Rouphael, and Chiara Cirillo

In the current scenario of decreasing in precipitation and water resources, and increasing in temperature,   it is pivotal to define multiple strategies to cope with the negative consequences on the crop production and food security. Hazelnut (Corylus avellana L.) is an important nut tree crop grown in several countries all over the world and mainly in the Mediterranean Basin area. Among the producer countries Italy is the second main worldwide producer, soon after Turkey. Despite the long-lasting and traditional cultivation of hazelnut in the hilly areas and a recent wider spread of its orchards to newly cultivated fertile plains, hazelnut is well known as a very sensitive species to both water stress and high temperatures. The main aim of this study was to evaluate growth performances and morpho-physiological adaptive responses to prolonged water stress in potted young hazelnut plants. Secondarily, the effect of biostimulant treatments in mitigating the effects of water and heat stresses were evaluated. The research was conducted on one-year-old cultivar micro propagated plants of cv “Tonda di Giffoni” grown in a cold polycarbonate greenhouse at the Department of Agricultural Sciences of the University of Naples “Federico II” during two consecutive growing seasons. Three irrigation levels (i.e. 100, 80, and 60% of the daily water requirement) were applied in combination with two different biostimulant treatments. In particular, they consisted in the application near the roots of protein hydrolysate or mycorrhizae inoculation. The first one was applied every two weeks with a dosage of 2.5 ml/l according to the chemical characteristics of the product, during the whole growing season; instead, the second one was applied with a single-dose of 15 g per plant at the beginning of each growing season. During the two seasons, growth rate (i.e. basal diameter, branch length, leaf number, leaf area, and buds), eco-physiological behaviour (i.e. gas exchanges measurements, Chlorophyll a fluorescence emission, SPAD index, and leaf water potential), and leaf functional traits were investigated. Results   showed that the use of biostimulant and mycorrhizae positively influenced physiological behaviour and growth of plants by counteracting deficit irrigation stress effects. In conclusion, our study demonstrate how these type of treatments help to improve the quality of plants.

How to cite: Vanacore, L., Modarelli, G. C., El-Nakhel, C., Pannico, A., Rouphael, Y., and Cirillo, C.: Biostimulant applications to mitigate multiple summer stress effects on potted Corylus avellana L. young plants, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9556, https://doi.org/10.5194/egusphere-egu23-9556, 2023.

EGU23-10375 | ECS | Posters on site | BG3.3

Ecosystems threatened by intensified drought with varied vulnerability in Europe 

Qi Chen, Joris Timmermans, Wen Wen, and Peter van Bodegom

With climate change increasing the severity and duration of droughts, ecosystems may not be able to withstand such droughts causing a rapid collapse. However, at present we lack a quantitative understanding of this ‘buffer capacity’ of ecosystems to these deteriorating droughts. Here, we established continental-scale models to quantify the ecosystem vulnerability and associated drought characteristics impacts for different ecosystems in Europe using high spatial and temporal resolution drought and traits data from remote sensing. Specifically, we observed varying vulnerabilities across ecosystems where vegetation damage increases with earlier, longer and more intense droughts. However, we also found that vulnerability of most ecosystems increases disproportionally when drought severity begins to increase. Collectively, the results suggest that the intensified drought under future climate change could threaten a vast range of ecosystem types. The multi-characteristics assessment of ecosystem vulnerability based on traits in our study will help to forecast and quantify vegetation damage to future global climate change challenges and inform drought mitigation policies.

How to cite: Chen, Q., Timmermans, J., Wen, W., and van Bodegom, P.: Ecosystems threatened by intensified drought with varied vulnerability in Europe, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10375, https://doi.org/10.5194/egusphere-egu23-10375, 2023.

EGU23-12407 | Posters virtual | BG3.3

Monitoring of plant phenological traits in a mixed Mediterranean forest species based on colour vegetation indices 

Carla Cesaraccio, Alessandra Piga, Simone Mereu, Andrea Ventura, Pierpaolo Masia, and Pierpaolo Duce

Phenology reflect the influences of climate change on individual plant biodiversity. Meteorological factors (temperature, precipitation, sunshine period) are reported to have major influence for determining variation of time phenophases through changes in biological activities.

Functional traits are morphological, physiological, and phenological features that show the plant functional response to a specific environmental condition. Traits are therefore connected to physiological functions and mechanisms that allow species to face the climatic changes.

Phenological traits can help explaining variation in plant growth strategies as it is closely associated with carbon gain and nutrient conservation. The beginning of leaf emergence and senescence can maximize plant survival and productivity, as the duration of stages are closely related to resource acquisition and distribution. Intraspecific trait variation, complementarity, and environmental stress are investigated at several hierarchical levels with the final goal of identify the mechanisms through which individuals and species interact and coexist for the use of resources. Therefore, it is fundamental to understanding how species modulate their phenological traits.

In this work, phenological traits for 12 forest species are monitored and studied. The research was conducted on an experimental site in Sardinia, Italy. A selection of monocultures and mixed communities, with different levels of species richness and functional diversity, were under observation over a 2-years period.

Phenological traits were investigated by using automated monitoring systems for recording high-resolution digital images in the visible spectrum. Start and duration of the growing season were monitored to acquire information regarding the plant status in relation to environmental conditions (temperature/drought). The images were collected at daily interval during the period 2017-2019. Six systems were set-up and installed on a metal pole, at 2.5 m height above ground.

The phenological traits for each individual were determined by analysing images visually. Moreover, a digital image processing, for deriving colour vegetation indices, was performed using a routine specifically developed under the software application MATLAB. RGB color channel information were recorded as digital numbers (DN) in a region of interest (ROI). To reduce the effects of scene illumination, the DNs are converted in to chromatic coordinates. Daily values of vegetation indices (ExG, REI, GRVI, etc) were then calculated.

The pattern of vegetation indices during the growing season were analysed for each species, showing how the color index performance works in capturing vegetation phenological change, and the performance of species growing under different levels of richness and functional diversity.

Information from this study can provide a valid contribution to a more detailed understanding on how plant responds to different environmental conditions, in particular in relation to phenological behaviour in response to climatic changes in Mediterranean regions.

How to cite: Cesaraccio, C., Piga, A., Mereu, S., Ventura, A., Masia, P., and Duce, P.: Monitoring of plant phenological traits in a mixed Mediterranean forest species based on colour vegetation indices, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12407, https://doi.org/10.5194/egusphere-egu23-12407, 2023.

EGU23-12429 | ECS | Posters on site | BG3.3

Self-DNA early exposure in cultivated and weedy Setaria triggers ROS degradation signaling pathways and root growth inhibition 

Alessia Ronchi, Alessandro Foscari, Giusi Zaina, Emanuele De Paoli, and Guido Incerti

The accumulation of fragmented extracellular DNA in decomposing plant litter reduces conspecific seed germination and plantlet growth in a concentration-dependent manner. An inverse relationship between DNA inhibition magnitude and taxonomic distance between the DNA source and the target species has been reported. This phenomenon bears important implications in plant ecology, as the accumulation or removal of DNA in litter can play a fundamental role in determining biodiversity patterns in different ecosystems and could represent a further explanatory process underlying negative plant–soil feedback. In this context, self-DNA has been suggested to act as a stress signaling molecule, possibly as damage-associated molecular pattern (DAMP), triggering plant resistance and growth inhibition in response to environmental stressors (e.g., herbivory, pathogens attack, intraspecific competition) causing death and subsequent release of conspecific DNA in the soil. The underlying mechanisms at cellular and molecular levels are not yet fully clarified, but previous studies reported the induction, in plants, of early innate immune response, ROS production, MAPK activation, extra-floral nectar production, increased intracellular [Ca2+] and plasma membrane depolarization. Moreover, a recent whole-plant transcriptome profiling and confocal microscopy analyses in Arabidopsis thaliana suggested that cells are capable of discriminating self from non-self DNA by specific sensing and highlighted an association between self-DNA exposure and abiotic stress gene response. In the present work we investigated, for the first time, the species-specificity of self-DNA inhibition in cultivated vs. weed congeneric species (respectively, Setaria italica and S. pumila) and carried out a targeted real-time qPCR analysis, under the hypothesis that self-DNA elicits molecular pathways responsive to abiotic stressors. The results of a first cross-factorial experiment on root elongation of plantlets exposed to self-DNA, congeneric DNA and heterospecific DNA from Brassica napus and Salmon salar questioned the species-specificity of the inhibitory effect, possibly related to the confounding effect of contaminants in the treatment solutions. A repeated test after ultra-purification of the treatment solutions confirmed a significantly higher inhibition by self-DNA as compared to non-self treatments, the latter showing a magnitude of the effect consistent with the phylogenetic distance between the DNA source and the target species. Targeted gene expression analysis highlighted an early activation of genes involved in ROS degradation and management (FSD2, ALDH22A1, CSD3, MAPK17) and deactivation of scaffolding molecules acting as negative regulators of stress signaling pathways (WD40-155). While being the first exploration of early response to self-DNA inhibition at molecular level on C4 model plants, our study highlights the need for further investigation of the relationships between DNA exposure and stress signaling pathways, discussing potential applications for species-specific sustainable weed control in agriculture.

How to cite: Ronchi, A., Foscari, A., Zaina, G., De Paoli, E., and Incerti, G.: Self-DNA early exposure in cultivated and weedy Setaria triggers ROS degradation signaling pathways and root growth inhibition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12429, https://doi.org/10.5194/egusphere-egu23-12429, 2023.

EGU23-12765 | Posters on site | BG3.3

Trends in plant species-wise abundances with parallel maintenance of community-level diversity in a Hungarian sandy pasture 

Szilvia Fóti, János Balogh, Sándor Bartha, Krisztina Pintér, and Zoltán Nagy

The relative importance or the abundance of plant species in ecosystems shows large spatio-temporal variability due to habitat- and species-related factors. What is more, in Hungary, climate change is accompanied by an increased probability of droughts and heat waves with further consequences on community attributes both in time and space.

The finely undulating (no more than 1.5 m elevation differences within the study site) surface in our sandy grassland study site was formed through the combined effects of wind, water erosion, and drought, and resulted in uneven soil nutrient and water distributions. We surveyed the vegetation of an ~ 1 ha area along 15 campaigns covering spring, summer, and autumn aspects for 7 years in 80 × 60 m grids where the surface cover of plant species within 78 patches of 0.5 × 0.5 m quadrates was recorded. The large spatial and temporal dataset (n=78 × 15=1170 quadrates with an overall species number of 114) enabled us to follow both species-wise (abundances) and community-level (e.g., diversity) patterns along with different terrain attributes for years.

During the study period, the grassland functioned as a carbon sink with a balanced physiological performance with year-to-year variability. The yearly sum of precipitation was very variable without any statistically significant change since the establishment of the study station (2002); however, significant warming was observable since then.

Within the study area, vegetation differentiation was detectable along with the terrain attributes. This vegetation differentiation was temporally variable following the patterns of how species with different environmental requirements split available places/resources through time. At hotter, dryer, more elevated positions, and more on the ridges, we could differentiate a larger ratio and diversity of a group of species favoring such conditions, while another group was more abundant in areas with opposite conditions. The presence of such different species groups and functional types within this relatively small area with a slight surface undulation may have been responsible for the observed balanced physiological performance of the grassland. However, although the diversity of the community as a whole didn’t change significantly during the study period, one of the ecological group diversities, that of species favoring cooler, wetter positions, decreased. So, not only temporal variability but also trend-like shifts were observable in the vegetation composition through time, and the stability of the diversity was found to show a terrain-related pattern.

How to cite: Fóti, S., Balogh, J., Bartha, S., Pintér, K., and Nagy, Z.: Trends in plant species-wise abundances with parallel maintenance of community-level diversity in a Hungarian sandy pasture, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12765, https://doi.org/10.5194/egusphere-egu23-12765, 2023.

Although evidence of the incidence of foliar water uptake has previously been documented in white spruce (Picea glauca), its eco-physiological importance remains unclear. Our aim was to evaluate the ecological significance of functional differences in foliar water uptake between populations relative to their climate of origin, foliar anatomy, and aquaporin expression.

To investigate needle radial anatomies, micrographs were made using new growth needles collected from 11 provenances growing in a range-wide common garden experiment near Athabasca Alberta. Correlations were then performed to determine relationships between the anatomies and climatic parameters of origin. A foliar water uptake experiment was then conducted on twigs with new growth needles from 6 representative provenances, 3 pairs, each from a different climatic ecozone to best capture a gradient of differences in latitude and marked differences in climate of origin and needle anatomy. The experiment was run using two initial desiccation levels on the 3 ecozones selected—mild, and severe—and mass measurements and tissue samples for RT-qPCR of PIP aquaporins were taken before dehydration, and at t=0, 30, 60, and 240 minutes.

Provenances with thinner Casparian strips and hypodermis layers lost more water during needle dehydration but were also able to take up water faster when wet. Dry climate, Boreal Plains provenances, were anatomically maladapted to drought but had a greater water influx than the others over the first 30 minutes of wetting, which may be explained by their greater aquaporin expression levels during uptake. Expression rates of PIP aquaporins 1;1, and 2;2 were strongly positively correlated with RWC and 1;2 was negatively correlated with the hypodermis thickness.

We conclude that population level differences in foliar water uptake are facilitated by needle anatomy and mediated by aquaporin expression. Our results suggest that there are inherent trade-offs between productivity maintenance in cold climates, drought tolerance, and foliar water uptake. Colder climate populations are anatomically maladapted to drought, but some may be able to compensate with foliar water uptake.

How to cite: Fleurial, K. G., Sebastián Azcona, J., Hamann, A., and Zwiazek, J. J.: Threading the white spruce needle: hydraulic foliar adaptive traits stitch a story of diffusion trade-offs between growth maintenance, drought resistance, and needle water uptake, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13695, https://doi.org/10.5194/egusphere-egu23-13695, 2023.

EGU23-15576 | ECS | Posters on site | BG3.3

Understanding plant vulnerability to stressors with automated image analysis 

Giorgia Del Cioppo, Simone Scalabrino, Melissa Simiele, Gabriella Stefania Scippa, and Dalila Trupiano

Plants often experience adverse or stressful environments that might have an impact on their growth and development, thus, phenotype. Visible symptoms of stress had been long studied, but their manual scrutiny can be challenging, time-consuming, and error-prone. However, there are currently very few instances of machine learning (ML) models that can automatically predict plant stresses, especially abiotic ones, from image-derived morphological traits. This study aims to fill this gap using digital phenotyping tools for stress detection based on automated image analysis and to further compare them with standard analytical procedures commonly carried out in laboratories. Two preliminary models for classifying salt stress levels have been developed to achieve this goal on Arabidopsis thaliana plants. Seedlings were grown on different substrates (soil and perlite) and exposed to “medium” and “high” salinity stress levels (50 mM and 150 mM NaCl) for 10 days. Biochemical parameters – Electrolyte Leakage (EL), Relative Water Content (RWC), and Dry weight (DW) – were measured, along with morphological traits – colorimetrical and geometrical – obtained from RGB images using both manual and automated approaches. The resulting data was then used to evaluate the performance of decision trees on 2-classes (presence or absence of stress) and 3-classes models (absence, medium, and high-stress levels). We noticed that plants’ development was influenced both by the growing environment and substrate type. Visible symptoms of stress included a reduction in leaf number and rosette size, as opposed to a chlorosis increment. RWC and DW decreased in response to high NaCl concentration, whereas EL increased. Nevertheless, while differences were significant among high-stressed plants and control ones, medium-stressed plants were hard to discern from both conditions. The Principal Component Analysis, which grouped the two levels of stress, also supported this conclusion. These results were further validated by classification algorithms tested: the 3-classes model only achieved 73% accuracy, compared to the binary model’s 90%. EL appears to be one of the key features for stress detection, but other important image-derived functional traits have also emerged from this preliminary study that can be used as indicators of plant health status and to study plant strategy to cope with environmental stressors, thus predicting their vulnerability/resilience to extreme climate conditions. With these findings, we demonstrate the great potential of image analysis methods and we highlight the positive impacts of automation, including increased analysis speed and decreased error rates. Moreover, we emphasize the importance of explainable ML models that can be easily interpreted and indicate essential traits needed for the model’s deployment and improvement. Given the modest size of our dataset, an integrated strategy is still necessary to obtain an adequate degree of classification accuracy. Therefore, in the future, by increasing the number of instances, we aim to enhance the model’s robustness and reliability and generalize it for the detection of various abiotic stresses in diverse species.

How to cite: Del Cioppo, G., Scalabrino, S., Simiele, M., Scippa, G. S., and Trupiano, D.: Understanding plant vulnerability to stressors with automated image analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15576, https://doi.org/10.5194/egusphere-egu23-15576, 2023.

EGU23-16069 | ECS | Posters on site | BG3.3

Managing climatic risk in cocoa by designing resilient agroforestry systems based on a functional trait approach 

Issaka Abdulai, Munir Hoffman, Michaela Dippold, Richard Asare, and Reimund Rötter

Climate change projections indicate that significant areas of the current cocoa cultivation areas in West Africa are likely to experience unfavorable climatic conditions by 2050. Water use efficient agroforestry systems are considered to be an important option to adapt cocoa to climate change. Water use efficiency and complementary soil water use between cocoa and shade trees have been reported in previous studies in Indonesia but in our previous study in Ghana, popular native shade tree species Albizia ferruginea and Antiaris toxicaria were found to have a strong competitive water use advantage over cocoa plants during an extreme drought experienced during 2015/16. Cocoa plants under no shade were relatively more resilient with higher survival rate and post drought recovery.

While past research studies   were each limited to few selected shade tree species being investigated despite the huge numbers within cocoa landscapes. To overcome this limitation, an approach based on functional traits of trees in terms of water use is proposed to understand their effect on water use efficiency and drought resilience in cocoa agroforestry systems rather than describing individual species. We apply this concept across temporal and spatial scales in a marginally suitable cocoa climate in Ghana. Shade tree species have been categorized into phenological trait groups (evergreen, deciduous, or brevi-deciduous) under which detailed above- and belowground traits interactions with cocoa plant and effect on water use has been evaluated.

The following hypotheses are being tested: (i) shade trees in the three phenological trait groups exhibit significant difference in their root and water uptake depth, and, thus, affect environmental conditions relevant for cocoa, (ii) cocoa plant above- and belowground morphological and physiological traits are influenced by shade tree phenological and morphological traits and their modification by micro-climatic (light, temperature, relative humidity and VPD), and soil (water and nutrients) conditions over different seasons.

Replicated plots of 19 shade tree species distributed across the three phenological trait groups have been established for analysis of functional traits interactions in such a multi-species agroforestry system. We determine root specific traits through direct sampling, stable isotope analysis for assessment of water use portioning between the various shade tree groups and cocoa plants. Soil moisture, temperature and relative humidity and light sensors were installed in each plot. Cocoa plants under different micro-climatic impact zones of the shade trees have been monitored for a full production cycle.  The shade trees impact on the cocoa plant productivity (morphology and yield traits) has been evaluated. Complementary and non-complementary shade tree species with respect to their trait interactions and effect on cocoa plant productivity have been identified.

How to cite: Abdulai, I., Hoffman, M., Dippold, M., Asare, R., and Rötter, R.: Managing climatic risk in cocoa by designing resilient agroforestry systems based on a functional trait approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16069, https://doi.org/10.5194/egusphere-egu23-16069, 2023.

EGU23-17297 | Orals | BG3.3

Fine-root morphological traits may improve understanding of the vulnerability of Fagus sylvatica natural forests to late-fall unusual wildfire 

Antonio Montagnoli, Mattia Terzaghi, Alessio Miali, Donato Chiatante, and Kasten Dumroese

Extraordinary changes in alpine fire regimes have been often associated with heat waves, which are generally regarded as an indication of a changing climate that will lead to new fire regimes in the Alps. Fine roots function of absorbing water and nutrients is crucial to plant survival and their traits such as biomass, length, specific root length, production, death, and decomposition can inform how trees interact with their environments and provide ecological functions in response to exogenous stresses. After an unusual, late-fall wildfire in a European beech (Fagus sylvatica L.) forest in the pre-Alps of northern Italy, the response of fine roots (< 2 mm diameter) was analysed and appeared more evident when fine roots were further subdivided by diameter size and soil depth. The finest roots (0‒0.3 mm diameter) were generally the most responsive to fire, with the effect more pronounced at the shallowest soil depth. While roots 0.3‒1 mm in diameter had their length and biomass at the shallowest soil depth reduced by fire, fire stimulated more length and biomass at the deepest soil depth compared to the control. Fire elevated the total length of dead roots and their biomass immediately and this result persisted through the first spring, after which control and fire-impacted trees had similar fine root turnover. Our results add to the paucity of data concerning fire impacts on beech roots in a natural condition and provide the basis for understanding fine-root morphological traits approach to assess plant species vulnerability and resilience to unusual fire occurrence due to climate changes. Changes in disturbance regimes might be most realized by distribution of the finest of fine roots at differing soil depths, and the dynamics of these roots may provide the most resilience to disturbance.

How to cite: Montagnoli, A., Terzaghi, M., Miali, A., Chiatante, D., and Dumroese, K.: Fine-root morphological traits may improve understanding of the vulnerability of Fagus sylvatica natural forests to late-fall unusual wildfire, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17297, https://doi.org/10.5194/egusphere-egu23-17297, 2023.

EGU23-1418 | ECS | Posters on site | BG3.4 | Highlight

Digital forest inventory based on UAV imagery 

Steffen Dietenberger, Marlin M. Mueller, Felix Bachmann, Markus Adam, Friederike Metz, Maximilian Nestler, Sören Hese, and Christian Thiel

Data on forest parameters defining the structure, health and condition of a forest stand is essential for forest management and conservation. The increasing frequency of forest changes, such as those caused by climate change-related drought and heat events, highlight the importance of having a forest database with high spatial and temporal resolution. Automated forest parameter extraction based on unmanned aerial vehicle (UAV) imagery is a cost-effective way to address the need for accurate and up-to-date forest data.

The aim of this project is to develop user-friendly tools based on optical data from UAVs that can be applied to accurately and efficiently conduct digital forest inventories. We are using spectral and geometric information from UAV data to create methods for automated derivation of forest parameters such as diameter at breast height (DBH), tree stem positions, individual tree crown delineation, and coarse wood debris. These methods are being designed with the practical needs of potential users from the forestry sector in mind. Different flight configurations, such as nadir and oblique camera angles, as well as different acquisition times, were combined to generate structure from motion (SfM) data products (dense 3D point clouds, orthomosaics and height models) containing both ground and canopy information. For a study site within the Hainich National Park, Germany, we analyzed how leaf-off and leaf-on data can be combined to improve the derivation of stand parameters, such as tree stem positions and individual tree crowns, using point- and raster-based algorithms. Additionally, DBH on an individual tree basis was derived for the same study site using the cast shadows of tree trunks. To do so, a deep learning model was trained to identify stem shadows based on an orthomosaic of only ground points acquired during sunny and leaf-off conditions.

How to cite: Dietenberger, S., Mueller, M. M., Bachmann, F., Adam, M., Metz, F., Nestler, M., Hese, S., and Thiel, C.: Digital forest inventory based on UAV imagery, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1418, https://doi.org/10.5194/egusphere-egu23-1418, 2023.

EGU23-2212 | Posters on site | BG3.4

Is growth of Swiss stone pine at the alpine treeline impaired or enhanced by competition with N2-fixing green alder? 

Walter Oberhuber, Ethan Salino, Lena Obexer, Gerhard Wieser, and Andreas Gruber

Green alder (Alnus alnobetula (Ehrh.) K. Koch = Alnus viridis (Chaix) DC) is a nitrogen-fixing pioneer species that is widely distributed at high altitude and latitude in the northern hemisphere. Due to changes in land management green alder is currently the most expanding shrub in the European Alps. It forms dense, tall thickets that are thought to impair establishment and growth of trees. The main focus of this study therefore was (i) to compare annual increments of Swiss stone pine (Pinus cembra L.), which is the dominant tree species at high elevation in the Central Eastern Alps, with that of green alder, and (ii) to determine radial growth of Swiss stone pine in competition and in absence of competition with green alder. The study area is situated within the treeline ecotone stretching from c. 1950 up to 2200 m in the Central Tyrolean Alps (Mt. Patscherkofel: 47.21 N, 11.46 E; Kühtai: 47.22 N, 11.04 E). A comparison of radial growth between similar aged stems (c. 20 yrs) revealed that annual increments of Swiss stone pine (2311 ± 628 µm) were more than four-times larger than those of green alder (519 ± 92 µm). This finding can be explained by different carbon allocation strategies, i.e., favouring vertical stem growth in single stemmed Swiss stone pine over preference of horizontal spreading in multi-stemmed green alder. This interpretation is supported by aerial photographs, which show that green alder stands are spreading vigorously within the treeline ecotone on Mt. Patscherkofel, amounting to c. 450 m2 ha−1 decade−1. Radial growth measurements of Swiss stone pine occurring inside and outside green alder thickets (canopy height 2–3 m) revealed that Swiss stone pine individuals with a comparable height to green alder (tree height: 2.9 ± 0.8 m) showed significantly lower growth inside green alder stands than outside, while Swiss stone pine trees taller than green alder thickets (tree height: 6.1 ± 1.6 m) grew better inside than outside green alder thickets. We explain these findings by source limitation of Swiss stone pine growth at low tree height, whereas with increasing tree height carbon assimilation is no longer a limiting factor and the higher N2 availability within green alder thickets can be exploited for stem growth. We conclude from this study that due to its horizontal competition strategy and dense cover of its foliage green alder is able to strongly impede the establishment and growth of co-occurring late-successional Swiss stone pine. Hence, spreading of green alder due to land abandonment and decrease in grazing pressure causes a delay in the development of closed forest stands, and also hampers climate warming induced advance of the alpine treeline.

This research was funded by the Austrian Science Fund (FWF), P34706-B.

How to cite: Oberhuber, W., Salino, E., Obexer, L., Wieser, G., and Gruber, A.: Is growth of Swiss stone pine at the alpine treeline impaired or enhanced by competition with N2-fixing green alder?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2212, https://doi.org/10.5194/egusphere-egu23-2212, 2023.

EGU23-2903 | ECS | Orals | BG3.4

Mega-Disturbances and forest decline in the Sierra Nevada of California, USA: Insights for managing disturbance dynamics 

Zack Steel, Gavin Jones, Brandon Collins, Rebecca Green, Alex Koltunov, Kathryn Purcell, Sarah Sawyer, Michele Slaton, Scott Stephens, Peter Stine, and Craig Thompson

Mature forests characterized by high cover of tall trees and complex understories are important habitat for native plant and wildlife species and support critical ecosystem functions globally. In California’s Sierra Nevada a combination of a century of fire exclusion and worsening climate change has led to increasingly severe wildfires and extreme drought that threaten habitats of sensitive species. Using spatially explicit datasets of forest structure and the Ecosystem Disturbance and Recovery Tracker, we quantified the loss of conifer forest cover in the southern Sierra Nevada between 2011 and 2020, a decade and region characterized by unprecedented mega-disturbances. Due to the combination of wildfires, drought, and drought-associated beetle kill, 30% of conifer forest extent was lost (fell below 25% canopy cover) during this period. Of the spatially limited mature forest habitats, 56% of moderate density (40-60% canopy cover) and 84% of high density (>60% canopy cover) forests were degraded. Drought and beetle-kill caused greater cumulative degradation than areas where wildfire mortality overlapped with the other disturbances. However, burned areas resulted in larger patches of forest loss and greater forest fragmentation on average. These results highlight that current conservation approaches are failing to protect mature forest habitats within disturbance-prone ecosystems like the conifer forests of California. We emphasize the need to switch from a static approach to conservation toward one focused on managing healthy disturbance dynamics, especially using frequent low-severity fire to increase forest resilience to future mega-disturbances. Without rapid management interventions, remaining mature forest habitat in the Sierra Nevada may be susceptible to complete loss in the coming decades.

How to cite: Steel, Z., Jones, G., Collins, B., Green, R., Koltunov, A., Purcell, K., Sawyer, S., Slaton, M., Stephens, S., Stine, P., and Thompson, C.: Mega-Disturbances and forest decline in the Sierra Nevada of California, USA: Insights for managing disturbance dynamics, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2903, https://doi.org/10.5194/egusphere-egu23-2903, 2023.

EGU23-3564 | ECS | Orals | BG3.4

Linking remotely sensed ecosystem resilience with forest mortality across the continental United States 

Xiaonan Tai, Anna Trugman, and William Anderegg

Episodes of forest mortality have been observed worldwide associated with climate change, impacting species composition and ecosystem services such as water re- sources and carbon sequestration. Yet our ability to predict forest mortality remains limited, especially across large scales. Time series of satellite imagery has been used to document ecosystem resilience globally, but it is not clear how well remotely sensed resilience can inform the prediction of forest mortality across continental, multi-biome scales. Here, we leverage forest inventories across the continental United States to systematically assess the potential of ecosystem resilience derived using different data sets and methods to predict forest mortality. We found high resilience was as- sociated with low mortality in eastern forests but was associated with high mortality in western regions. The unexpected resilience–mortality relation in western United States may be due to several factors including plant trait acclimation, insect popula- tion dynamics, or resource competition. Overall, our results not only supported the opportunity to use remotely sensed ecosystem resilience to predict forest mortality but also highlighted that ecological factors may have crucial influences because they can reverse the sign of the resilience–mortality relationships.

How to cite: Tai, X., Trugman, A., and Anderegg, W.: Linking remotely sensed ecosystem resilience with forest mortality across the continental United States, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3564, https://doi.org/10.5194/egusphere-egu23-3564, 2023.

EGU23-4068 | ECS | Orals | BG3.4

Drought resistance enhanced by tree species diversity in global forests 

Dan Liu, Tao Wang, Josep Peñuelas, and Shilong Piao

Restoring species diversity is proposed as a strategy to improve ecosystem resistance to extreme droughts, but the impact of species diversity on resistance has not been evaluated across global forests. Here we compile a database that contains tree species richness from more than 0.7 million forest plots and satellite-based estimation of drought resistance. Using this database, we provide a spatially explicit map of species diversity effect on drought resistance. We found that higher species diversity could notably enhance drought resistance in about half of global forests but was spatially highly variable. Drought regimes (frequency and intensity) and climatic water deficit were important determinants of differences in the extent that species diversity could enhance forest drought resistance among regions, with such benefits being larger in dry and drought-prone forests. According to a predictive model of species diversity effect, the conversion of current monoculture to mixed-species tree plantations could improve drought resistance, with the large increase in dry forests. Our findings provide evidence that species diversity could buffer global forests against droughts. Restoration of species diversity could then be an effective way to mitigate the impact of extreme droughts on large scales, especially in dry and drought-prone regions.

How to cite: Liu, D., Wang, T., Peñuelas, J., and Piao, S.: Drought resistance enhanced by tree species diversity in global forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4068, https://doi.org/10.5194/egusphere-egu23-4068, 2023.

EGU23-4614 | ECS | Orals | BG3.4

Can process-based BGC models simulate drought-induced tree mortality worldwide? 

Nanghyeon Jo, Casimir Agossou, Eunsook Kim, Jong-Hwan Lim, and Sinkyu Kang

Drought-induced tree mortality has been increasing worldwide under climate change; therefore, forests will become more vulnerable as warming continues. With growing interest in tree decline due to increased climate variability, ecophysiological roles and dynamics of non-structural carbohydrates (NSCs) have drawn wide attention recently. Accordingly, a lot of field data have been collected, but these achievements were not well incorporated in process-based vegetation models yet, where NSCs ecophysiology was implicitly applied or ignored. In this study, we addressed five key modeling issues in simulating spatial and temporal patterns of NSCs dynamics across different scales as follows: (1) interconversion between dual NSCs pools (i.e., rapid soluble sugar and slown starch pools), (2) incorporation of the sink-limited growth allocation strategy, (3) hydraulic limitation of NSCs transports between organs, (4) feedback mechanisms between tree NSCs and root symbionts, and (5) large-scale simulations of NSCs dynamics. In addtion, we applied key issues (1) and (2) of NSCs to the BIOME-BGC model and evlauated across biomes. As a result, modified BGC model (BGC-NSCs) successfully simulated vegetation traits across different biomes, such as seasonal and interannual variations of St (mean R2 of, 0.55, 0.62), and site-specific SS-to-St ratios, while the model did not simulate the SS temporal variation well. Nevertheless, in the factor analysis of several variables for the global tree mortality data, physiological variables such as NSCs and PLC (Percent loss of conductivity) produced in the BGC-NSCs model were important. Despite limitations of the current BGC modeling and simple assumptions of mortality mechanisms, this study demonstrated a potential to use key ecophysiological variables for simulating widespread drought-induced mortality across different biomes and climate regions. 

How to cite: Jo, N., Agossou, C., Kim, E., Lim, J.-H., and Kang, S.: Can process-based BGC models simulate drought-induced tree mortality worldwide?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4614, https://doi.org/10.5194/egusphere-egu23-4614, 2023.

EGU23-4657 | ECS | Posters on site | BG3.4

Integration of TreeTalker proximal data with remote sensing for monitoring seasonal phenological dynamics at the species level in Italy 

Alexander Cotrina-Sánchez, Gaia Vaglio Laurin, Jerzy Piotr Kabala, Francesco Niccoli, Jim Yates, Riccardo Valentini, and Giovanna Battipaglia

Over the years, remote sensing and spectroscopy have contributed significantly to vegetation monitoring, primarily to understand the interaction of plants with solar radiation. However, due to spatial and temporal heterogeneity, light availability below and within tree canopies is challenging to estimate or time-consuming. Therefore, it is essential to know the structure of the tree canopy through vertical light transmission profiles, which will allow estimating plant development, biophysical properties throughout the canopy and the seasonal phenology of the species.

Currently, technologies based on the Internet of Things (IoT) are constituted as efficient and low-cost tools for monitoring forest ecology at the individual and species levels. A device applied to ecology and based on IoT is the "TreeTalker" (TT +), which allows measuring in semi-real time, in addition to water transport in trees, diametrical growth, the spectral transmittance of light through the canopy in 12 spectral bands, using spectrometers in the visible range (VIS) between 450 – 650 nm and 610 – 860 nm in the near-infrared (NIR). These parameters are acquired and stored by each TT+ every hour, sent to a node (TT-Cloud), and transmitted and stored on a server.

In this context, our study integrates remote sensing data and those obtained through IoT to evaluate the variability of the spectral response at the population level in forest species: Quercus cerris, Fagus Sylvatica and Pinus pinaster. Cloud computing was used through Google Earth Engine (GEE) to extract multitemporal values from the Sentinel 2 satellite and its subsequent integration with data from the TreeTalker spectrometer, devices installed in trees of 05 plots located in central and southern Italy, precisely in the Rocarespampani sector in Viterbo, Vesuvio National Park and Matese Regional Park in Campania Region.

Preliminary results show the ability of the TT+ spectrometer to store daily information at different wavelengths during the year. The spectral response of the near-infrared (NIR) bands is the most susceptible to foliage changes for deciduous species, mainly in the summer and spring seasons. In the case of visible bands (VIS), it is more susceptible to energy input in coniferous species and in the winter and autumn seasons. Finally, a higher correlation was obtained between the NIR bands of Sentinel 2 and TT+, mainly for the deciduous species Q. cerris and F. Sylvatica.

The seasonal assessment of the species will be continued during the following years at local and regional scales to understand their responses to climate change. Also, light transmission through the forest canopy will contribute to identifying and complementing knowledge of forest-climate interactions, allowing a more detailed understanding of the ecophysiological parameters of forest vegetation and phenological changes at the species and ecosystem level.

How to cite: Cotrina-Sánchez, A., Vaglio Laurin, G., Kabala, J. P., Niccoli, F., Yates, J., Valentini, R., and Battipaglia, G.: Integration of TreeTalker proximal data with remote sensing for monitoring seasonal phenological dynamics at the species level in Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4657, https://doi.org/10.5194/egusphere-egu23-4657, 2023.

EGU23-5947 | ECS | Posters on site | BG3.4

Responses of Fagus sylvatica growing in Southern Italy to climate change: insight from sap flow continuous monitoring 

Jerzy Piotr Kabala, Francesco Niccoli, and Giovanna Battipaglia

The ongoing climate change, with altered precipitation regimes and altered evaporative demand due to the increase in temperature are affecting hydrological conditions in most forest sites in Europe. This change has strong consequences on the distribution, composition and ecological functioning of forest species . Fagus sylvatica is one of the most important species in Europe, spanning from southern Scandinavia to the Mediterranean region. Species distribution models forecast a reduction of the area of distribution of F. sylvatica in Italy under the climate change scenarios. The hydraulic behaviour and transpiration responses of the beech to climate conditions have been studied in central Europe. However, this has been scarcely addressed in the southernmost part of its distribution area, where this knowledge might be critical in understanding the physiological responses of this species to climate change, and then its capability to persist in the area.

This study aims to understand the responses of the transpiration of a Fagus sylvatica forest to meteorological variables in the southern Apennines (Matese Regional Park, Italy). The forest stand has been continuously monitored for 2 years with the TreeTalker devices, that record sap flux data at an hourly scale, along with several microenvironmental parameters. The monitoring period encompasses the droughty 2022 year, with high temperatures and precipitations well below the average.

The forest stand studied varies its sap flux in response to the environmental conditions, by reducing its transpiration in late summer, when VPD is high, but water availability is low. This conservative hydraulic behaviour seems to protect the trees from immediate damage due to drought periods, as no tree mortality has been observed. These results suggest that even if in the past Fagus sylvatica has been considered an anisohydric species, the southern ecotypes show a more isohydric behaviour than expected. The prosecution of this monitoring might provide further information about long-term trends in the ecophysiology of this forest.

How to cite: Kabala, J. P., Niccoli, F., and Battipaglia, G.: Responses of Fagus sylvatica growing in Southern Italy to climate change: insight from sap flow continuous monitoring, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5947, https://doi.org/10.5194/egusphere-egu23-5947, 2023.

EGU23-6143 | ECS | Posters on site | BG3.4

Dieback events of Scots pines caused by lack of rain in mid and late summer 

Stefan Hunziker, Michael Begert, Simon C. Scherrer, Andreas Rigling, and Arthur Gessler

Same as other parts of Europe, the inner-Alpine Swiss Rhône valley has been increasingly affected by Scots pine (Pinus sylvestris L.) dieback events since the 1990s. Such events were not confined to years of extreme heat and drought across Switzerland and Europe such as 2003 or 2018, and the severity and frequency of sudden tree mortality varied on relatively small spatial scales. Which are the relevant parameters that changed in time and which factors triggered these dieback events?

We found that sudden mortality events occurred exclusively after periods of below average precipitation between July and September. During this time of the year, soil moisture regularly drops to a minimum while the atmospheric water demand is high. Further factors such as insect infestation or spring frost may increase the magnitude of tree mortality, but they were neither a required contributor nor were they found to trigger dieback events. Consequently, the region with lowest summer precipitation within the Swiss Rhône valley outlines the area most affected by Scots pine dieback.

However, the amount and frequency of the highly variable summer precipitation did not decrease since the 1980s, but the atmospheric water demand in spring and summer increased continuously. As a result of the higher water loss to the atmosphere, the period of low soil moisture has been prolongated and intensified. Therefore, Scots pines have become more dependent on (temporary) water stress relief by precipitation events during mid and late summer.

Many Scots pine died (most likely due to hydraulic failure) within months following severe summer water stress. The effects of such periods appeared faster on tree crown defoliation (i.e., the proportion of needles that should be present on a tree, but which have been lost) than on mortality, as some trees died only after a year or two. We found that these Scots pines exceeded a defoliation threshold of about 75 % and were unable to recover. In such strongly defoliated trees, stress-related metabolites increase in needles, but get depleted in roots, indicating that mortality is linked to belowground carbon starvation negatively affecting functions central for tree survival.

How to cite: Hunziker, S., Begert, M., Scherrer, S. C., Rigling, A., and Gessler, A.: Dieback events of Scots pines caused by lack of rain in mid and late summer, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6143, https://doi.org/10.5194/egusphere-egu23-6143, 2023.

EGU23-6819 | ECS | Posters on site | BG3.4

Biodiversity threatened by increasing mountain forest loss 

Xinyue He, Zhenzhong Zeng, Joseph Holden, and Dominick Spracklen

Mountain forests are currently experiencing severe losses in many parts of the world because they are sensitive to climate change and anthropogenic pressures. However, the distribution of the world’s mountain forest loss and how it has changed in the 21st century remain unclear. Here, we conducted a global analysis on mountain forest loss by using multiple high-resolution remote sensing datasets. Our results show that the total forest loss over global mountains during 2001–2018 was 78 million ha (7% of the mountain forest area in 2000) and that annual mountain forest loss tripled by 2016. Spatially, the largest loss area occurred in the tropical and boreal mountain forests, particularly in Southeast Asia, Russia, and Canada. We find many mountain regions with considerable losses in forest cover are also biodiversity hotspots, suggesting these areas need more attention and require protection. Our findings indicate that the interaction of mountain forest changes and biodiversity impact should be incorporated into future impact assessments.

How to cite: He, X., Zeng, Z., Holden, J., and Spracklen, D.: Biodiversity threatened by increasing mountain forest loss, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6819, https://doi.org/10.5194/egusphere-egu23-6819, 2023.

EGU23-7456 | ECS | Posters on site | BG3.4

Resilience and synergism in larch-beech-spruce mixed forests 

Viktória Pipíšková, Jan Světlík, and Soham Basu

The current environmental conditions in Central Europe negatively affect tree growth and forest vitality. Mixing tree species may stabilize or even increase stand productivity and mitigate the effects of drought caused by climate change. However, the effects of mixing European larch (Larix decidua Mill.) with other species have not been assessed by systematic empirical studies. Accordingly, we studied the growth response of larch trees growing in middle-aged mixed stands with European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.) in the highlands of the Czech Republic - Drahanská vrchovina (around 500 m a.s.l.). Four research sites with similar environmental conditions were selected to observe various forest mixtures: larch-beech-spruce, larch-beech, larch-spruce, and pure larch. 10 wood cores were collected at breast height from each tree species at the site (a total of 80 samples). Cores were measured and cross-dated by the dendrochronological software Past4. The radial increment of target trees with respect to the competition of the 10 nearest neighbouring trees was evaluated. Positions were measured with a Filed-Map system (IFER, Czech Republic). The competition indexes were calculated as the ratio between the DBH of the target tree and of the competitor divided by the distance between them. The resistance (growth reduction during the extreme year), recovery (growth response after the extreme year), and resilience (capacity to reach pre-disturbance growth) of target trees were calculated.

The even-aged stands with a different proportion of larch, beech, and spruce exhibited a different growth response under the same climatic conditions. In 2018 (the year with the most stressful climatic conditions in the last decade), a decrease in the tree-radial increment of spruces and beeches was observed. This did not occur in larches. They had a similar (only marginally better) growth response in monoculture compared to mixed stands. Tree resistance to the environmental conditions in 2018 was lower than a value of 1 for all tree species. However, beeches growing in the triple mixed stand were the most resistant. Surprisingly, larches in a monoculture exhibited a higher resistance compared to mixed stands. The highest recovery after the extreme conditions of 2018 was observed in larches growing in all variations of mixed stands. On the other hand, larches in a monoculture demonstrated nearly their lowest growth in the period 2019 - 2021. Only larches growing with beeches had a wood increment as high as prior to 2018 (higher resilience of larches growing with beeches). The other tree species reached their previous (2015 – 2017) increment in all stands with larches, so we can assume a positive effect of larch presence (increases the resilience of other tree species). We determined that the larches are not significantly influenced by competition with their neighbours. Furthermore, larches in monoculture are more resistant and larches growing in mixtures are more resilient with superior recovery. 

Key words: competition, stem increment, recovery, resilience, resistance, tree-rings, wood cores

How to cite: Pipíšková, V., Světlík, J., and Basu, S.: Resilience and synergism in larch-beech-spruce mixed forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7456, https://doi.org/10.5194/egusphere-egu23-7456, 2023.

EGU23-8249 | Orals | BG3.4

Towards species-level forecasts of drought-induced tree mortality risk 

Martin De Kauwe, Manon Sabot, Belinda Medlyn, Andy Pitman, Patrick Meir, Lucas Cernusak, Anna Ukkola, Sami Rifai, and Brendan Choat

Australia is the driest inhabited continent. Annual rainfall is low and is accompanied by marked inter-annual variability, leading to multi-year droughts. n particular, ​South-East Australia​ ​has recently experienced two of the worst droughts in the historical record (2000–2009 and 2017–2020). Predicting species-level responses to drought at the landscape scale is critical to reducing uncertainty in future terrestrial carbon and water cycle projections. We embedded a stomatal optimisation model in the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model and parameterised the model for 15 canopy-dominant eucalypt tree species across South-Eastern Australia (mean annual precipitation range: 344–1424 mm yr-1). We carried out three experiments: applying CABLE to the recent drought; a theoretical future drier drought (20% reduction in rainfall); and a future drier drought (20% reduction in rainfall) with a doubling of atmospheric carbon dioxide (CO2). The drought's severity was highlighted as at least 25% of their distribution ranges, and 60% of species experienced leaf water potentials beyond the water potential at which 50% of hydraulic conductivity is lost due to embolism. We identified areas of severe hydraulic stress within species’ ranges, but we also pinpointed resilience in species found in predominantly semiarid regions. The importance of the role of CO2 in ameliorating drought stress was consistent across species. Our results represent an important advance in our capacity to forecast the resilience of individual tree species, providing an evidence base for decision-making around the resilience of restoration plantings or net-zero emission strategies.

How to cite: De Kauwe, M., Sabot, M., Medlyn, B., Pitman, A., Meir, P., Cernusak, L., Ukkola, A., Rifai, S., and Choat, B.: Towards species-level forecasts of drought-induced tree mortality risk, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8249, https://doi.org/10.5194/egusphere-egu23-8249, 2023.

EGU23-8720 | ECS | Posters on site | BG3.4

Fusion of European forest inventories with Sentinel-1 and Sentinel-2 data for improving scalability in estimating forest variables 

Milto Miltiadou, Stuart Grieve, Julian Tijerín Triviño, Julen Astigarraga, Harry Owen, Paloma Ruiz Benito, and Emily Lines

Large scale forest inventory plot data are key to monitor forest ecosystems, but while they provide very detailed information at tree level they are limited in resolution in both space and through time. Earth Observation (EO) data offer the opportunity for scaling up plot data and improving the temporal resolution of monitoring. However, there are significant challenges to this, including small field plot sizes, pre-processing and potential GPS errors in aligning the data, whilst the huge amount and variety of EO data introduce substantial challenges of high dimensionality, in addition to the noise of training and testing data, within any AI system. In this work, we fuse plot and Earth Observation data, demonstrating the value of embedding existing and newly EO derived metrics, and selecting the most important features to improve monitoring of forest properties at large scales. 

In this work we work with Sentinel-1 (SAR) and Sentinel-2 (optical) and inventory data from close to 10,000 plots in Spain, measured from onwards. SAR data require substantial pre-processing due to noise and acquisition, topographic and moisture effects. We used pre-processed SAR data, and filtered for non-shaded slopes, removed plots close to surface water and data collected on days with high precipitation. We masked out clouds from our optical data. After fusing the EO data, we removed disturbed areas using the Global Forest Change Collection and plots with high variability of pixels around them to reduce uncertainty due to the small sizes of the plots. As well as using standard indices (e.g., NDVI, RVI), we derive new metrics of the phenological cycle of the forest from monthly averages of indices and bands by selecting features from peaks and troughs. We reduce dimensionality using principal component analysis and random forest to select the most important features. Chosen features are used for training and evaluating a customized AI system to estimate forest variables such as total basal area, stem density, mean diameter at breast height and forest type. The code implemented in Google Earth Engine JavaScript and Python will be released as open source.

How to cite: Miltiadou, M., Grieve, S., Tijerín Triviño, J., Astigarraga, J., Owen, H., Ruiz Benito, P., and Lines, E.: Fusion of European forest inventories with Sentinel-1 and Sentinel-2 data for improving scalability in estimating forest variables, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8720, https://doi.org/10.5194/egusphere-egu23-8720, 2023.

EGU23-9237 | ECS | Posters on site | BG3.4

How late spring frosts affect tree-ring growth and wood anatomical traits of European beech in Mediterranean mountain forests? 

Enrico Tonelli, Alessandro Vitali, Julio J. Camarero, Michele Colangelo, Davide Frigo, Francesco Ripullone, Marco Carrer, and Carlo Urbinati

Xylem anatomical traits in series of annual tree rings, allow establishing structure-function relationships and assessing species sensitivity to environmental variability. Extreme events such as late spring frosts (LSF) and drought spells are among the main climate-induced disturbances affecting European beech (Fagus sylvatica L.) forests, especially in the Mediterranean region. In this study we aimed to i) compare chronologies of tree-ring widths and vessel traits of beech trees located along an elevation gradient and ii) determine the variability of tree-ring traits before and after LSF occurrence. The study sites, located in the Italian Apennines and Spanish Pyrenees, were hit by severe LSF in recent years. We investigated how tree growth and vessel traits varied in relation to indicators of spring frost occurrence, i.e., mean minimum temperatures, accumulated degree days and temperatures anomalies. Then, we checked vessel traits in rings formed right after the frost events and compared them to those measured in non-affected trees. Radial growth reductions ranged from 36 % to 84 % and this negative effect of LSF on radial growth was only detected during the same LSF year. Growth fully recovered within 1–2 years after the LSF. We found a decrease of vessels diameter and surface area, and higher vessel density with increasing elevations. Vessel traits did not provide added values for detecting spring frost sensitivity. In fact, LSF caused the formation of very narrow rings but no-significant differences in vessels traits. Our results indicate a good recovery capacity of European beech and no legacy effects caused by LSFs. However, other xylem proxies (e.g., fiber cell wall) could better detect LSF impacts on wood formation.

How to cite: Tonelli, E., Vitali, A., Camarero, J. J., Colangelo, M., Frigo, D., Ripullone, F., Carrer, M., and Urbinati, C.: How late spring frosts affect tree-ring growth and wood anatomical traits of European beech in Mediterranean mountain forests?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9237, https://doi.org/10.5194/egusphere-egu23-9237, 2023.

EGU23-9998 | ECS | Posters virtual | BG3.4

Structural overshoot and post-drought recovery depend on site and species-specific characteristics in Mediterranean mixed forests 

Santain Settimio Pino Italiano, Jesús Julio Camarero, Angelo Rita, Michele Colangelo, Marco Borghetti, and Francesco Ripullone

Increasing drought severity can affect the healthy status of forests and determine changes in structural and ecophysiological responses to such extreme climate events. Reduced canopy cover, productivity and tree growth and recent dieback phenomena are widespread responses to drought. However, favourable climatic conditions can improve the post-drought recovery capacity of forests, but also make them vulnerable to drought damage through structural overshoot by altering the root to shoot ratio due to wet conditions. Due to the lack of integrated and retrospective field data, the patterns and responses of forests to wet-dry climate variability are still poorly understood. In this work we used remote sensing data (NDVI) to characterise the canopy conditions and combined them with field and tree-ring width data to assess the effects of the summer 2017 drought on Mediterranean tree species in southern Italy (Fraxinus ornus, Quercus pubescens, Acer monspessulanum, Pinus pinaster). By comparing radial growth and resilience indices we found that growth responses to drought depended not only on tree species but also on site conditions. Overall, the growth decline due to drought was followed by a rapid recovery, while negative legacies to drought were found at lower quality sites, which corresponded to sites with the lowest NDVI values. Indeed, trees at these sites showed high growth rates before drought, in response to wet winter-spring conditions, and then suffered more from drought stress. Our results demonstrated how structural overshoots predisposes to drought damage and induced negative legacies. Specific knowledge on the effects of drought overshoot over time is important for analysing and understanding current forest responses and dynamics.

How to cite: Italiano, S. S. P., Camarero, J. J., Rita, A., Colangelo, M., Borghetti, M., and Ripullone, F.: Structural overshoot and post-drought recovery depend on site and species-specific characteristics in Mediterranean mixed forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9998, https://doi.org/10.5194/egusphere-egu23-9998, 2023.

EGU23-12037 | Posters on site | BG3.4

Thermodynamic Approach to Assessing Ecosystem Integrity of Gwangneung Old-Growth Forest Biosphere Reserve in Korea 

Joon Kim, Hyunyoung Yang, Minseok Kang, and Jung-Hwa Chun

Biodiversity and integrity are the key indicators representing ecosystem’s state. Much attention has been given to the former while less to the latter. This is because (1) the definition of integrity is ambiguous, (2) theoretical framework is lacking for quantitative assessment, and (3) observation data for quantification and validation are in paucity. The review of literature funnels down the definition of integrity to twofold perspectives: normative and thermodynamic. Accordingly, we define integrity as a state of ecosystem whose structure and function self-organize to an extent comparable to its reference state. Here, system’s self-organization can be expressed holistically based on non-equilibrium thermodynamics by quantifying the system’s thermodynamic entropy balance. We have tested this definition and the theoretical framework to assess the integrity of Gwangneung old-growth forest in Korea (GDK), which has been designated as one of the UNESCO’s Biosphere Reserves since 2010. Long-term observation (from 2005 to 2020) of energy, matter (water vapor and carbon dioxide) and information flows in and out of GDK were divided into the reference period (2006-2010) and the test period (2011-2020). These dataset emcompasses a wide range of environmental conditions and disturbances to examine ecosystem response and adaptability. GDK's self-organization was estimated in terms of entropy production (σ) and entropy transfer (J). Also, using information-theoretic approach, the behaviors of σ and J were analyzed in terms of the balance between informational emergence (flexibility) and self-organization (order, thus related to resilience). These results were compared and scrutinized by associating with the analyses of (1) linear cause and effect relationships between key variables representing ecosystem structure and function (e.g., energy capture, energy dissipation, biomass production, respiration, biodiversity) and (2) transfer entropy-based dynamic process network (of subsystems at various spatio-temporal scales, feedback types/loops and delay). Granting the necessity of further test and improvement, we argue that thermodynamic and information-theoretic frameworks are complementary and shed a light to development of more holistic and operational indicators for ecosystem integrity such as maximum complexity and antifragility.

How to cite: Kim, J., Yang, H., Kang, M., and Chun, J.-H.: Thermodynamic Approach to Assessing Ecosystem Integrity of Gwangneung Old-Growth Forest Biosphere Reserve in Korea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12037, https://doi.org/10.5194/egusphere-egu23-12037, 2023.

EGU23-12088 | Posters virtual | BG3.4

Assessment of changes in wood anatomical traits to forecast drought-induced dieback in Mediterranean oak forests 

Michele Colangelo, Angelo Rita, Marco Borghetti, J. Julio Camarero, Raúl Sánchez-Salguero, Luis Matias, Osvaldo Pericolo, and Francesco Ripullone

Some tree species have shown to be very vulnerable to drought and heat waves in the Mediterranean Basin, causing a loss of important socio-economic and ecosystem forest services.  In this regard, oaks are important but vulnerable species which are showing losses in terms of productivity and growth and rising mortality rates. Dendroecological studies using retrospective analysis of wood anatomical traits and tree rings have demonstrated their potential to assess long-term patterns of growth and vigor in several Mediterranean oak species. Moreover, the long-term reconstruction of wood anatomical traits such as transversal lumen area, allows investigating hydraulic adjustments of trees through time.

In this study, we reconstructed changes in wood anatomy for a 38-year long period (1980-2017) to investigate how drought impacted the hydraulic functionality and triggered dieback in five ring-porous oak species from Italy and Spain (Quercus robur, Quercus frainetto, Quercus cerris, Quercus canariensis, Quercus pubescens). We compared non-decaying (ND) and decaying (D) coexisting trees of each species showing low and high defoliation levels, respectively. We analyzed earlywood anatomical traits (vessel area, hydraulic diameter, vessel density, theoretical hydraulic conductivity, etc.) in these species and analysed them considering a ranking of increasing drought tolerance: Q. robur, Q. frainetto, Q. cerris, Q. canariensis, and Q. pubescens.

We observed differing growth patterns and xylem conduit area responses in D trees compared with ND trees. The D trees formed narrower EW vessels than ND and the Dh were lower in D trees compared with ND trees. We discuss the relationships between radial growth, changes in wood anatomy and hydraulic functioning of trees focusing on those proved more sensitive to growth decline and mortality in order to highlight the climatic triggers of dieback in ring-porous oak species as related to hydraulic failure.

How to cite: Colangelo, M., Rita, A., Borghetti, M., Camarero, J. J., Sánchez-Salguero, R., Matias, L., Pericolo, O., and Ripullone, F.: Assessment of changes in wood anatomical traits to forecast drought-induced dieback in Mediterranean oak forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12088, https://doi.org/10.5194/egusphere-egu23-12088, 2023.

EGU23-12250 | ECS | Orals | BG3.4 | Highlight

‘The application of a novel IoT driven biosensing platform, the TreeTalker®, for coppice forest monitoring in central Italy’. 

Jim Yates, Shahla Asgharinia, and Riccardo Valentini

Coppicing forest management systems represent the oldest systematic silvicultural practice across the European continent. This simplistic yet sustainable system is well defined by several silvicultural applications which are in general designed to provide a woody crop within a relatively short rotational period. Additionally, the treatment and maintenance of such forests continue to provide a variety of functions and thus ecosystem services. Although the extension of coppice forests is estimated at approximately 20 million hectares across Europe, they are often poorly utilised, undermanaged or altogether abandoned. In systems where management activity is enduring, threats from climate induced mortality remain prevalent. This coupled with poor management, which often promotes over stocking on one hand and unregulated coppice sprout management inducing stool exhaustion on the other, threaten this historical management approach. Consequently, novel monitoring efforts for these forest types and systems merits attention. This study aims to investigate the application of a novel biosensing platform, the TreeTalker, toward the continuous monitoring of individual sprouts on coppice stools and selected standards across three plots in a historically coppiced forest located in central Italy. The TreeTalker is an IoT driven device integrated platform aiming to monitor well established tree ecophysiological processes such as sap flow, stem radial growth and light canopy interactions in quasi real time via LoRa architecture and an inhouse multi sensor infrastructure. We present the results of a two year consecutive monitoring campaign using these devices. Evidently, we observed that competition among sprouts on the same stool is clearly detectable via the TreeTalkers sensors, particularly the radial dendrometer expressing different results both across the seasons monitored and among individuals. Strong signals in reduced stem radial growth across the very dry 2022 season were also observed. The results suggest that the TreeTalker provides high fidelity data on the ecophysiological behaviour of trees throughout the vegetative season. Data from these devices offers an exciting new frontier in forest monitoring. For coppice forests specifically, silvicultural activities such as timing of thinning intervention and sprout selection for standard recruitment can be guided by retrieved information in addition to real time monitoring of stem health. Scaling via more TreeTalker device installation and subsequent spatial and temporal requirements requires further investigation.

How to cite: Yates, J., Asgharinia, S., and Valentini, R.: ‘The application of a novel IoT driven biosensing platform, the TreeTalker®, for coppice forest monitoring in central Italy’., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12250, https://doi.org/10.5194/egusphere-egu23-12250, 2023.

EGU23-12291 | ECS | Posters on site | BG3.4

Ecophysiological and mechanistic post-fire strategies of Pinus pinaster Aiton growing in an area prone to multi-stress conditions. 

Francesco Niccoli, Marçal Argelich Ninot, Kabala Jerzy Piotr, Giovanna Battipaglia, Eric Verrecchia, and Pierre Vollenweider

The health of Mediterranean forests is seriously threatened by the effects of progressive climate change. Frequent droughts and heat waves induce heavy stress and favor the ignition of large wildfires causing decline in tree growth and mortality. Although trees are often able to survive the impact of fire thanks to their adaptive traits, partial injuries, such as crown defoliation, could compromise their physiology and resilience amplifying pre-existing climatic/site-specific stresses.

Expanding knowledge on the physiological and mechanistic dynamics of burned forests in areas prone to multi-stress conditions is crucial to identify the most resilient species capable of countering future rates of climate change.

In this context, our research aimed to understand the resilience of Pinus pinaster Aiton plantations located in the Vesuvius National Park, a particularly warm and dry area of southern Italy, affected by a large wildfire in 2017, which led to a progressive defoliation of trees in the post-fire years, reaching 50% in 2020. We selected different study sites along a wildfire severity gradient (control, low and medium burning intensity) and we applied a multi-parametric approach studying in the post-fire years (2017-2020): tree growth, intrinsic water use efficiency of the trees, morphological traits and needle nutrients in foliage, as well as the forest soil properties.

Morpho-anatomical analyses of foliage showed that although the burned stands suffered severe defoliation, resilience reactions already started in burned trees during weeks following wildfire, with the formation of larger but also more xeromorphic and defensive foliage (i.e. needles with higher linear weight and increased percentage area of resin ducts) than at the control site. On another hand, the needle nutrient content indicated for all sites severe deficiencies of main macro and micro-nutrients (especially N, P, K). Accordingly, soil analyzes highlighted a forest soil particularly poor in nutrients, and in burned sites the fire seems to have worsened the dystrophy by burning the nutrient pool in topsoil humus layer. Finally, the stem growth never recovered: tree-growth was steadily in decline in the burned versus control sites in the post fire years. Similarly, the intrinsic water use efficiency was reduced in burned stands indicating higher transpiration costs for assimilated carbon. The higher conductance, confirmed by the increase in the density of the stomatal lines found in needles, suggested the need of the burned trees to attempt a higher carbon uptake and counteract the carbon starvation in the stem triggered by the crown reduction.

Our results suggest that the studied burned stands are unlikely to recover their pre-fire performance. Carbon starvation will be difficult to reverse due to carbon retention in foliage to form new, heavier, and more defensive needles, also given the foliar nitrogen concentrations below deficiency level, further impeding assimilation. Therefore, the forest ecosystem reached a high vulnerability, not as a direct consequence of forest wildfire but due to the synergic effect of several stress factors: poor soil nutritional condition (exacerbated by the wildfire), an environment prone to drought stress and partial defoliation due to the fire (that lowered the tree photosynthetic capacity).

How to cite: Niccoli, F., Argelich Ninot, M., Jerzy Piotr, K., Battipaglia, G., Verrecchia, E., and Vollenweider, P.: Ecophysiological and mechanistic post-fire strategies of Pinus pinaster Aiton growing in an area prone to multi-stress conditions., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12291, https://doi.org/10.5194/egusphere-egu23-12291, 2023.

EGU23-12540 | ECS | Orals | BG3.4

Climate-driven variations in functional strategies of temperate forest ecosystems 

Daijun Liu, Adriane Esquivel-Muelbert, Jonas Fridman, Ruiz Benito Paloma, Zavala Girones Miguel Ángel, Julen Astigarraga, Suvanto Susanne, Andrzej Talarczyk, Emil Cienciala, Georges Kunstler, Mart-Jan Schelhaas, Jon Sadler, Tom Matthews, Chris Woodall, Nezha Acil, Chao Zhang, and Thomas Pugh

Tree functional strategies play a crucial role regulating the fitness and ability of forests to cope with water stress. However, current understanding on community-level functional strategies of forest ecosystems and how they vary with geographic patterns is still limited. We combined eight functional traits (e.g. leaf nitrogen content, xylem conductivity, leaf area to sapwood area ratio, leaf mass area, xylem water potential at 50% loss of conductivity, slope for the curve between P50-P88, leaf turgor loss point and wood density) with forest inventory data across the USA and Europe (12,332 0.25° gridcells) to identify functional strategies with respect to water stress and to analyse their relationships with climate factors and across functional groups. Principal components analysis suggests that functional strategies at species-level could be captured at community-level. Acquisitive-conservative strategies loaded along the first dimension, while the water storage and isohydricity strategies loaded along the second dimension. Spatial patterns of community-level strategies showed more explanatory power with temperature than aridity. Multiple community-level strategies at a grid cell were observed at water-limited sites, which were broadly captured by broad functional groups based on leaf type and phenology. Our findings promote the understanding of forest adaptation to drought and provide a basis for improving the ability of ecosystem models to predict the patterns of tree mortality and forest biomass accumulation.

How to cite: Liu, D., Esquivel-Muelbert, A., Fridman, J., Benito Paloma, R., Miguel Ángel, Z. G., Astigarraga, J., Susanne, S., Talarczyk, A., Cienciala, E., Kunstler, G., Schelhaas, M.-J., Sadler, J., Matthews, T., Woodall, C., Acil, N., Zhang, C., and Pugh, T.: Climate-driven variations in functional strategies of temperate forest ecosystems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12540, https://doi.org/10.5194/egusphere-egu23-12540, 2023.

EGU23-13210 | ECS | Posters on site | BG3.4 | Highlight

What future for pollinators in the understorey vegetation under the impact of climate change ? 

Benjamin Lanssens, Louis François, Alain Hambuckers, Merijn Moens, Tim Anders, Merja Tölle, Arpita Verma, and Laura Remy

Although understorey biomass is negligible in comparison to overstorey biomass, understorey vegetation supports the majority of biodiversity within forests. The diversity of  plant species in the understorey is important for pollinators, such as bees and butterflies, which use the available resources for food and shelter. However, the future of understorey vegetation is uncertain due to the impact of climate change and human activities.  Climate change and forest management are known to be among the most important factors affecting the diversity and abundance of understorey plant species. Most studies on understorey vegetation has often been limited in scope, either focusing on a small number of specific plant species or large-scale studies of plant functional types. In this study, we take a more comprehensive approach by combining the results of a species distribution model with a dynamic vegetation model to simulate the evolution of understorey vegetation at the species level. We select a set of 30 species important for pollinators. In order to cover a large climatic gradient, simulations are performed over the Walloon region in Belgium and the Eisenwurzen region in Austria. The climate dataset is provided by the regional climate model COSMO-CLM, which has a 3 km spatial resolution and covers the period from 1980 to 2070 under different greenhouse gas concentration scenarios (RCP 2.6 and RCP 8.5). Additionally, we investigate the effect of different forest management practices (thinning and clear-cutting) on overstorey and how they impact understorey vegetation. Overall, the study aims to provide new insights into the current and future state of understorey vegetation with a focus on the impact of climate change and forest management on key pollinator resources.

How to cite: Lanssens, B., François, L., Hambuckers, A., Moens, M., Anders, T., Tölle, M., Verma, A., and Remy, L.: What future for pollinators in the understorey vegetation under the impact of climate change ?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13210, https://doi.org/10.5194/egusphere-egu23-13210, 2023.

EGU23-13234 | ECS | Orals | BG3.4

Global analysis of deviations in climate sensitivity of tree-growth after extreme drought events 

Christopher Leifsson, Allan Buras, Anja Rammig, and Christian Zang

In the course of climate change, forests around the globe will be exposed to more frequent and more severe extreme drought events. Direct and lagging impacts of drought events on forests, so-called drought legacies, are often estimated from tree-ring derived secondary growth measurements which easily translate into biomass and are available globally. However, secondary growth is a result from multiple internal mechanisms and therefore does not reveal potential impacts on the underlying physiology, such as hydraulic dysfunction, repair mechanisms and altered carbon allocation. Instead, the carbon demand of these impacts translates to less carbon being available for secondary growth which therefore results in temporarily altered relationships between climate and growth.

Here, we advance the concept of drought legacies by additionally quantifying simultaneous “functional legacies” as climate sensitivity deviations (CSD) of secondary growth. We quantified legacies in both growth and climate sensitivity after extreme drought events using linear mixed-effects models on a global-scale, multi-species tree-ring dataset. We further differentiated the responses by clade, site aridity and hydraulic safety margins in order to determine common factors which convey heightened or lessened vulnerability to extreme drought events.

Our results show that while depressed growth was common after droughts across most of the analysed groups, although with varying legacy lengths, post-drought climate sensitivity deviations were more nuanced. The climate sensitivity of growth was decoupled for gymnosperms with small hydraulic safety margin, i.e. those with a more risk-prone hydraulic growth strategy. In comparison, the climate sensitivity of growth tightened for angiosperms growing in arid sites, a response which occurred in conjunction with a post-drought growth overshoot. These responses are consistent with current understanding of impaired hydraulic function and increased carbon allocation towards xylogenesis, respectively. In conclusion, climate sensitivity deviations reveal physiological responses not discernible from growth legacies alone and therefore serves as a promising avenue for a more comprehensive identification of drought impacts on tree growth at large scales.

How to cite: Leifsson, C., Buras, A., Rammig, A., and Zang, C.: Global analysis of deviations in climate sensitivity of tree-growth after extreme drought events, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13234, https://doi.org/10.5194/egusphere-egu23-13234, 2023.

EGU23-14520 | Posters on site | BG3.4

Stress response and transformation processes initiated by the summer drought 2018 – a multi-scale study from the Hainich forest 

Franziska Koebsch, Martina Mund, Anne Klosterhalfen, Steffen Dietenberger, Laura Donfack, Marius Heidenreich, Christian Markwitz, David Montero, Christian Thiel, Frank Tiedemann, and Alexander Knohl

More frequent and intense drought events pose one of the greatest threats to forests under climate change with substantial consequences for tree growth, ecosystem stability, and climate change mitigation. A better understanding of drought-related stress response and adaptation mechanisms is paramount to assess the adaptative capacity of forest ecosystems and deduce supportive management actions.

Here, we report on the stress effects and transformation processes initiated by the 2018 summer drought in the Hainich Nationalpark, an old-growth beech-dominated forest in Central Germany (DE-Hai). We deploy a multi-scale approach encompassing long-term eddy covariance measurements for stand-level CO2 exchange, concurrent surveys of tree increments, and satellite imagery that covers the core zone of the National Park. Thus, we can provide a comprehensive picture of the response mechanisms that occur in a mixed old-growth forest in the wake of a severe drought.

After a 15-year reference period of relatively stable net CO2 uptake of 535±73 g m2 yr-1 on average, the summer drought 2018 persistently lowered the forest’s CO2 sink function down to 333-395 g m2 yr-1 (2019-2021). The lowered CO2 sequestration was primarily due to a sustained reduction in photosynthetic CO2 uptake and went along with an increase in tree mortality from 1 to 6%. We observed a substantial shift in growth patterns among the surviving trees: Fraxinus excelsior, which in its role as competitor tree had contributed substantially to stand-level growth for a long time, showed significantly lower increments from 2018. At the same time, increments of Fagus sylvatica increased markedly after 2018. Especially younger, suppressed Fagus individuals benefitted in the post-drought period and pushed stand-level growth to a new record in 2021. On larger spatial scale encompassing the National Park core zone, drought response was overprinted by topographic effects that reflect landscape water availability, particularly altitude and routing of waterways.

Tree growth response to extreme water stress in a mixed, old-growth forest varies with regard to species-specific drought tolerance levels and/or the tree’s role in the forest structure. The natural growth dynamics emanating from drought events in unmanaged forests are modulated locally by landscape water availability, and can cumulate into profound structural change. At the early stage of transformation captured by our study, a reduction in productivity and climate change mitigation potential must be expected.

How to cite: Koebsch, F., Mund, M., Klosterhalfen, A., Dietenberger, S., Donfack, L., Heidenreich, M., Markwitz, C., Montero, D., Thiel, C., Tiedemann, F., and Knohl, A.: Stress response and transformation processes initiated by the summer drought 2018 – a multi-scale study from the Hainich forest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14520, https://doi.org/10.5194/egusphere-egu23-14520, 2023.

EGU23-14740 | ECS | Posters on site | BG3.4

Assessing Resilience Components in Maritime Pine Provenances Grown in Common Gardens 

Concetta Lisella, Serena Antonucci, Giovanni Santopuoli, Marco Marchetti, and Roberto Tognetti

Knowledge acquisition on the response of tree species to drought in the Mediterranean hotspot is an important step to guide adaptation strategies to climate change impacts, e.g., assisted migration.We assessed the resilience components - i.e., resistance, recovery, and resilience - to drought
in 2003 in five provenances of maritime pine planted in four common gardens in Sardinia, and analysed the possible influence of climate variables on these indices. The provenances showed differences in growth rate but not in the components of resilience. Among the provenances, Corsica
was the most productive, while Tuscany was the least. One of the two provenances from Sardinia (Limbara) showed good performance in terms of tree growth in the comparatively drier site. The resilience components were influenced by prevailing environmental conditions at the common garden
sites. In the relatively drier sites, trees showed the lowest resistance but the highest recovery values. However, two sites - which had the lowest stand density - showed the opposite trend during the drought year, probably due to moderate thinning. Predictive models showed different probability in
the response of resilience components to climate variables. Resistance and resilience had a similar pattern, both being positively related to temperature, while recovery showed an opposite trend. The models’ results indicate a noticeable adaptation of maritime pine to the drought conditions of Sardinia, though the age factor should be considered as well. Despite only minor differences among provenances being found, environmental conditions and management practices at the common gardens were important in determining tree growth patterns. This study suggests that the provenance of Corsica may provide appropriate material for forest plantations in Mediterranean conditions with mitigation purposes.

How to cite: Lisella, C., Antonucci, S., Santopuoli, G., Marchetti, M., and Tognetti, R.: Assessing Resilience Components in Maritime Pine Provenances Grown in Common Gardens, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14740, https://doi.org/10.5194/egusphere-egu23-14740, 2023.

This paper addresses the knowledge gaps on what determines tree responses to drought, their recovery, and survival following drought release, integrating physiological and morphological responses from the rhizosphere to the canopy of mature trees. I summarize 10 years of research on an experimentally induced drought and subsequent recovery in a maturing beech-spruce forest in southern Germany. Study objects 70- to 80-year-old trees that are readily accessible via canopy crane and grow in either mono-specific or mixed stands. We studied about 100 trees in 12 plots of roughly 150 m2 each. Tress were exposed to experimentally induced summer drought for five consecutive years by complete throughfall exclusion during the growing season (Kranzberg forest ROOF experiment, kroof.wzw.tum.de).

During the first two drought summers, when both species were not yet acclimated, drought stress intensity peaked with pre-dawn leaf water potentials near -2.0 MPa and concomitant severe declines in physiological (e.g. leaf gas exchange, phloem transport) and morphological (e.g. growth) responses. After overcoming the critical first two years of drought, significant morphological acclimation in the following three years, e.g. by adjustment of leaf area or rooting depths, resulted in relaxation of physiological stress, as evidenced, for example, by increased stomatal conductance and pre-dawn leaf water potential. Reduced water consumption of spruce and thus higher water availability, also for neighboring beech trees, significantly alleviated drought stress in the trees.

After a total of five years of experimentally induced summer drought, drought release was initiated in early summer 2019 by controlled watering. Physiological parameters such as stomatal conductance or xylem sap flow recovered with hours or days after drought release, including resilience of C allocation, e.g. sugar transport along the stems, as an important prerequisite for the recovery of tree functionality and productivity. Restored coupling between canopy and rhizosphere significantly supported spruce root growth, which recovered within a few days. In contrast, other morphological responses (e.g., leaf area recovery) took years to recover. With future increases in the frequency of drought events under ongoing climate change, tree species that recover more quickly will be favored.

How to cite: Grams, T.: Drought resilience of a mixed beech-spruce forest - an experimental study linking responses from the rhizosphere to the canopy, from physiology to morphology, and from hours to years, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15805, https://doi.org/10.5194/egusphere-egu23-15805, 2023.

Climate change is expected to increase the duration and severity of heatwaves and droughts in the Mediterranean region. In this climate change hotspot, drought and heat stress have triggered the occurrence of forest mortality events over the past decades. It is thus important detecting those regions in which drought-induced forest mortality events are occurring to advance in the knowledge of why some species and populations are more vulnerable to heat and drought than others.

If localized on time, these declining forests are valuable natural laboratories to attribute potential factors triggering mortality. However, detecting and identifying drought-impacted forest is challenging because forest mortality events in the Mediterranean region are spatially heterogeneous and have a local extent.

Here I summarize the main findings of several studies performed in forests that have been impacted by drought events over the past years aiming to detect how: i) the vitality and growth of shrubs and trees varied between species, and ii) between individuals within species. Further, I discuss how these results can help to increase our capacity in detecting forest mortality hotspots.

How to cite: Gazol, A.: Quantifying the response of shrubs and trees to drought as a tool to detect vulnerable forests in Spain, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17180, https://doi.org/10.5194/egusphere-egu23-17180, 2023.

EGU23-17203 | ECS | Posters on site | BG3.4

Wildfire impacts on soil characteristics in two Pinus halepensis Mill. stands within a Natura 2000 site (Southern Italy) 

Luigi Marfella, Rossana Marzaioli, Gaetano Pazienza, Paola Mairota, Helen Catherine Glanville, and Flora Angela Rutigliano

Forest fires are a complex disturbance linked to several factors, such as climate conditions, vegetation types and human activities. Their frequency and intensity/severity have increased in recent decades and this trend is projected to continue because of climate change. Particularly critical are wildfires that frequently affect natural areas. In 2020 across Europe about 131474 hectares of surface within the Nature 2000 Network (N2K) were burnt. In addition to causing damage to vegetation, fire can affect soil characteristics influencing the functioning of the whole forest ecosystem. Understanding the influence of fire on the soil system provides information on its resilience and can be a useful tool for supporting forest management.

This research complements a larger multidisciplinary research project monitoring the conservation status, sensu Habitat Directive 92/43/EEC, of the Habitat of Priority Interest 2270*-Wooded dunes with Pinus pinea and/or Pinus pinaster, within the Special Areas of Conservation (SAC) IT9130006-Pinewoods of the Ionian Arch. Here, we explore the relationships between soil and vegetation as a function of different fire conditions considered capable of triggering multiple successional pathways, potentially leading to habitat degradation. In this context, the specific objective of this work was to evaluate the long-term effects of wildfires on the soil properties in two Aleppo pine stands within the “Romanazzi” and “Marziotta” sections of the SAC that have been influenced by fires between 1997-2006 and 2000-2012, respectively. In both stands, three sites were identified: double-fire, single-fire and unburnt (control) sites. In March 2021, a synchronic sampling across sites, covering a period of 9-24 years post-fires, was performed. In each of them, the weight and organic carbon content of the organic layer (O-layer) were measured alongside the physicochemical and biological properties of the underlying topsoil (0-10 cm depth, n=5).

Our results show the absence of the O-layer in double-fire sites, indicating a loss of this organic carbon pool. On the contrary, in both single-fire sites, this layer had successfully recovered. Our data suggest that the recovery in the O-layer in single-fire plots might be independent of the time elapsed since the wildfire. Regarding soil properties, compared to control sites, both single and double-fire sites for each stand exhibited significant alterations in specific soil chemical properties, i.e., pH, electrical conductivity, content in total organic carbon (Corg), extractable organic carbon, nitric and ammoniacal nitrogen, as well as decreases in soil microbial biomass (Cmic), respiration, and Cmic/Corg ratio. Of particular interest was a significant alteration in the N-cycle with increased mineralization and nitrification rates in all burnt sites at both stands. Principal component analysis showed that the impact of multiple fires may not depend only on frequency or time since the last fire, but also on frequency-time interaction.

In conclusion, the burnt sites have not recovered to control levels for many soil characteristics, especially for N-cycle processes. The increase in N mineralization, nitrification and, consequently, in N availability could induce shifts in the plant, fungi, and pedofauna community structure, thus affecting the successional pathways with consequences on the resilience of the target forest ecosystem.

How to cite: Marfella, L., Marzaioli, R., Pazienza, G., Mairota, P., Catherine Glanville, H., and Rutigliano, F. A.: Wildfire impacts on soil characteristics in two Pinus halepensis Mill. stands within a Natura 2000 site (Southern Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17203, https://doi.org/10.5194/egusphere-egu23-17203, 2023.

EGU23-586 | ECS | Orals | BG3.5 | Highlight

Photosynthetic thermal acclimation capacity of tropical montane rainforest trees in Rwanda and in the Colombian Andes 

Mirindi E Dusenge, Maria Wittemann, Myriam Mujawamariya, Lasse Tarvainen, Elisée Ntawuhiganayo Bahati, Etienne Zibera, Bonaventure Ntirugulirwa, Danielle Way, Donat Nsabimana, Johan Uddling, Göran Wallin, Zorayda Restrepo Correa, Sebastian Gonzalez-Carro, Patrick Meir, and Adriana Sanchez

Tropical montane forests are among the most productive ecosystems within the tropical region and store a significant amount of carbon in live biomass. With ongoing global climate warming, tropical climates are also getting warmer. The productivity and climate feedbacks of future tropical montane forests depend on the ability of trees to acclimate their photosynthetic metabolism to these new, warmer conditions. However, knowledge of acclimation ability of photosynthesis and its underlying biochemical processes to warming in trees grown under natural field conditions is currently limited due to data scarcity. To reduce this knowledge gap, we used two separate field experiments located in Colombia (with 15 species) and Rwanda (16 species), and for each experiment, tree species were grown at three different sites along an elevation gradient differing in ambient air temperature. At all three sites, we measured the responses of net CO2 assimilation at different CO2 concentration (50 to 2000 ppm) and at different leaf temperatures (15 to 40 °C) in ≈ 3 years old trees. We used these data to derive key photosynthetic biochemical parameters (maximum Rubisco carboxylation capacity - Vcmax and maximum electron transport rate - Jmax) and their temperature sensitivity, as well as the thermal optimum of net photosynthesis (ToptA). We show that tropical montane tree species from the two continents are generally able to acclimate their ToptA by increasing in trees grown in warmer conditions, but the magnitude of change in ToptA differs among species from different successional groups (early- versus late succession) and climate of origin (lowland versus montane). Shifts in ToptA are largely driven by concomitant changes in thermal sensitivity parameters of underlying biochemical processes of photosynthesis (Vcmax and Jmax) with warming. We also show that, at a standard temperature of 25 °C, Vcmax is largely constant, while Jmax decreases with warming. Our findings indicate tropical montane tree species from Latin America and Africa can thermally acclimate their photosynthetic physiology, but that this thermal acclimation ability is related to species successional group and their climate of origin.

How to cite: Dusenge, M. E., Wittemann, M., Mujawamariya, M., Tarvainen, L., Ntawuhiganayo Bahati, E., Zibera, E., Ntirugulirwa, B., Way, D., Nsabimana, D., Uddling, J., Wallin, G., Restrepo Correa, Z., Gonzalez-Carro, S., Meir, P., and Sanchez, A.: Photosynthetic thermal acclimation capacity of tropical montane rainforest trees in Rwanda and in the Colombian Andes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-586, https://doi.org/10.5194/egusphere-egu23-586, 2023.

EGU23-1802 | Orals | BG3.5 | Highlight

Conifer desiccation in the 2021 NW heatwave confirms the role of hydraulic damage 

Tamir Klein, Jose Torres-Ruiz, and John Albers

The unprecedented heatwave that hit the Pacific northwest of North America in late June-early July 2021 impacted ecosystems and communities, yet evidence and analysis of this impact are still missing. Here we bring a unique dataset quantifying the impact on conifer trees, which are keystone species of many northwest ecosystems. Moreover, we take advantage of this exceptional event as a broad, extreme, “field experiment” to test a fundamental theory in plant physiology, and prepare our forests to a harsher future. Overall, the data collected confirm the role of hydraulic vulnerability in drought-induced injury to trees. Among the recorded species, we obtained P50 data for 27 species, represented by 64 cultivars. Plotting needle browning extent by P50 revealed important thresholds of drought sensitivity: (1) species with P50 <-6 MPa were unaffected by drought. (2) species with -6 MPa< P50 <-5 MPa had mild extent of needle browning, up to 25% of the canopy. (3) species with P50 > -5 MPa had browning of up to 95%. The sharp divergence among resistant and vulnerable conifer species according to their xylem vulnerability, all of which simultaneously exposed trees to the same extreme event at the same site, is evidence to the key role of P50, in agreement with previous assessments of drought effects on angiosperms. Among local, NW conifer species, some cultivars proved hardier than others. The aftermath of the 2021 NW heatwave should take advantage of this broad, extreme, “field experiment” to prepare our forests to a harsher future.

How to cite: Klein, T., Torres-Ruiz, J., and Albers, J.: Conifer desiccation in the 2021 NW heatwave confirms the role of hydraulic damage, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1802, https://doi.org/10.5194/egusphere-egu23-1802, 2023.

EGU23-4761 | ECS | Orals | BG3.5

Does plant ecosystem thermoregulation occur? 

Zhengfei Guo, Christopher Still, Calvin Lee, Youngryel Ryu, Benjamin Blonder, Jing Wang, Timothy Bonebrake, Alice Hughes, Yan Li, Henry Yeung, Kun Zhang, Ying Law, Ziyu Lin, and Jin Wu

To what extent plants thermoregulate their canopy temperature (Tc) in response to environmental variability is a fundamental question in ecology, and influences accurate projections of plants' metabolic response and resilience to climate change. However, debate remains, with opinions ranging from no to moderate plant thermoregulation capacities. Traditionally, it has been hypothesized that if plant thermoregulation occurs (i.e. ‘limited homeothermy’ hypothesis holds): 1) Tc will change more slowly than Ta over time, leading the Tcvs. Ta regression slope < 1; 2) Tc is cooler than Ta when Ta exceeds some threshold, typically during high net radiation conditions (e.g. at midday). Here, with global datasets of Tc, air temperature (Ta), and other environmental and biotic variables from FLUXNET and satellites, we tested the ‘limited homeothermy’ hypothesis across global extratropics, including temporal and spatial dimensions.

 

Our results demonstrate that across daily to monthly timescales, over 80% of sites/ecosystems have Tcvs. Ta regression slopes≥1 or Tc>Ta around midday, which rejects the ‘limited homeothermy’ hypothesis. For those sites unsupporting the hypothesis, their Tc-Ta difference (ΔT) still exhibits considerable seasonality that is negatively, partially correlated with their canopy structure seasonality (as indicated by leaf area index), implying a certain degree of thermoregulation capability. Across global sites, both site-mean ΔT and slope indicator exhibit considerable spatial variability, with ΔT having greater variability than the slope indicator. Furthermore, this large spatial ΔT variation (0-6°C) can be mainly explained by environmental variables (38%) and, to a lesser extent, by biological factors (15%). Our results suggested that plant thermoregulation patterns are diverse across global extratropics, with most ecosystems rejecting the ‘limited homeothermy’ hypothesis, but their thermoregulation still occurs, implying that slope<1 or Tc<Ta are not necessary conditions for plant thermoregulation.

How to cite: Guo, Z., Still, C., Lee, C., Ryu, Y., Blonder, B., Wang, J., Bonebrake, T., Hughes, A., Li, Y., Yeung, H., Zhang, K., Law, Y., Lin, Z., and Wu, J.: Does plant ecosystem thermoregulation occur?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4761, https://doi.org/10.5194/egusphere-egu23-4761, 2023.

EGU23-4771 | Posters on site | BG3.5

Forest management scenarios using Korean dynamic stand growth model considering the new climate change regime 

Mina Hong, Moonil Kim, Youngjin Ko, and Woo-Kyun Lee

Climate change is a global issue affecting our lives, surrounding environments, and socioeconomic sectors. Accordingly, the recently published IPCC sixth assessment report emphasizes the role of forests as a source of greenhouse gas sink and shows the importance of climate resilient development pathways (CRDPs). South Korea is also putting forth policies such as the ‘2030 NDC’ and ‘2050 LED’ and is trying to find sustainable forest management measures to respond to the new climate change regime. Therefore, this study sought strategic measures to solve problems such as age class imbalance and mortality increase due to climate change in forests using the Korean dynamic stand growth model. Furthermore, CRDP was selected through recently announced SSP climate data and policy-based forest management scenarios to respond to the new climate change regime. As a result, the climate scenario is SSP1, the forest management scenario is when clear-cut harvest according to the legal final cutting age and thinning is implemented about 200,000 ha, reforestation of appropriate species to respond to climate change, and access to the forest road is within 1km, it was found that the overall growth of the forest increased. Although the current growth of 4.3m3 ha-1 decreases to 2.39m3 ha-1 in 2050, it is predicted to increase to 3.16m3 ha-1 in 2100 through the growth of species suitable for the climate and balance of age classes. In addition, it was analyzed to contribute to the increase in sequestration and carbon storage in logs due to harvest. In conclusion, this study is meaningful in that it presents a future strategy for responding to the new climate regime by reflecting the environmental and ecological characteristics of South Korea.

 

How to cite: Hong, M., Kim, M., Ko, Y., and Lee, W.-K.: Forest management scenarios using Korean dynamic stand growth model considering the new climate change regime, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4771, https://doi.org/10.5194/egusphere-egu23-4771, 2023.

Leaves form the primary interface between plant physiology, CO2 in the atmosphere and energy (light). Plant productivity (i.e. carbon (C) gain) is primarily determined by the amount of leaf area, leaf orientation and distribution in space. Not much attention has been paid to possible changes in leaf orientation and distribution with elevated CO2 (eCO2), but its effect on plant growth could alter the proportions of sunlit and shaded leaf areas and feedback on carbohydrate available for further growth. We report on first measurements of leaf inclination angle distribution, foliage clumping in a native evergreen Eucalyptus woodland - the EucFACE experiment in Western Sydney, New South Wales, Australia - in ambient CO2 and exposed to +150 ppm elevated CO2 (eCO2). We found that a spherical leaf angle distribution, a common assumption in ecosystem modeling, was not an appropriate supposition for present species (Eucalyptus tereticornis Sm.; Eucalyptus amplifolia Naudin) at this site. Our measurements of leaf inclination angles from imagery indicated an erectophile, highly skewed unimodal leaf inclination angle distribution function. We conclude that despite the measured steeper angles under eCO2 concentrations, the leaf angle change is not significant and falls within the expected natural variability and uncertainties connected with the measurement method. The lack of a clear response of leaf orientation and foliage clumping to eCO2 concentration indicates that the previously produced datasets of leaf inclination angles and foliage clumping maps with Earth observation data may be suitable while modelling carbon and water cycles under climate change.

How to cite: Pisek, J., Řezníčková, L., Adamson, K., and Ellsworth, D.: How can elevated CO2 (eCO2) affect the vegetation structure of a mature evergreen Eucalyptus woodland – results from the Eucalyptus Free-Air CO2 Enrichment (EucFACE) experiment in Australia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5024, https://doi.org/10.5194/egusphere-egu23-5024, 2023.

EGU23-5561 | ECS | Posters on site | BG3.5 | Highlight

Modeling the effect of elevated CO2 on root exudation and ecosystem carbon storage in mature forests 

Kristian Schufft, Katrin Fleischer, Anja Rammig, Lin Yu, and Sönke Zaehle

Increased atmospheric carbon dioxide (CO2) is known to enhance  leaf-level photosynthesis. Following the carbon fertilization hypothesis, the increased photosynthetic assimilation may lead to an increase in plant biomass, therefore representing a negative feedback mechanism to rising CO2 emissions. The magnitude and limitations of this effect remain one of the major uncertainties in projecting the future influence of increasing atmospheric CO2 on terrestrial biogeochemical cycles and climate change.

Forests contribute strongly to the contemporary terrestrial carbon (C) sink, however, the magnitude of the effect of elevated carbon dioxide (eCO2) on these ecosystems is still not fully understood. While experiments have demonstrated that young forests show increased aboveground biomass production under eCO2, the evidence for the effect on mature forests is still ambiguous. In these ecosystems, enhanced translocation of additional assimilated C belowground instead of investing in aboveground structure may significantly reduce C accumulation due to enhanced photosynthesis. One key mechanism in this process is exudation of C via roots into soil, which can increase nutrient availability to plants but also leads to soil C losses. By using a terrestrial biosphere model (QUINCY), which comprises a representation of the coupled carbon-nitrogen-phosphorus cycles in terrestrial ecosystems, we simulate the effect of elevated CO2 on exudation and its consequences for the C cycling and storage in mature forests. In comparison to other existing models we calculate exudation rates dynamic, based on plant carbon surplus and nutrient demand. We evaluate the effect using alternative representations of soil biogeochemical processes at the example of the EucFACE experiment in a mature Eucalyptus forest. We show that nutrient-stress induced increases in the exudation rate under eCO2 partially explains higher soil respiration and therefore lower C accumulation in this forest ecosystem.

How to cite: Schufft, K., Fleischer, K., Rammig, A., Yu, L., and Zaehle, S.: Modeling the effect of elevated CO2 on root exudation and ecosystem carbon storage in mature forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5561, https://doi.org/10.5194/egusphere-egu23-5561, 2023.

EGU23-5932 | ECS | Posters on site | BG3.5

Influence of climatic variables on forests condition in Poland in the period 2002-2021 

Kinga Kulesza and Agata Hościło

Forest ecosystem stress caused by climate change, in particularly prolonged and severe droughts, has already been manifested in several parts of Europe, including temperate and boreal forests. It is likely that droughts and heatwaves will occur more often, which might result in the ecological transition of the forests and loss of biodiversity. The assessment of climate change impact on forest ecosystems is complex, as response can vary in space (depending on the physiological vulnerability of ecosystems and site conditions), time, and among species (species resilience).

In this project we investigate the influence of several climatic variables (2 m temperature, rainfall, evapotranspiration and climatic water balance) on the forests condition in Poland in the period 2002-2021. To this end we use ERA-5 Land reanalysis data and vegetation indices – NDVI and EVI – derived from the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS) – MOD13Q and MYD13Q. The remotely sensed indicators on vegetation consist of 8-day composites and have 250-m spatial resolution, while the climatic data is 0.1° x 0.1° spatial and 1-day temporal resolution.

The spatio-temporal trends of NDVI and EVI were computed for forest areas only, and their statistical significance was assessed. The monthly analyses were carried out for growing season (April-October). Multi-annual trends of climatic variables were prepared not only for the period 2002-2021, but also for the longer period 1971-2021, in order to strengthen the information coming from the climate trend analysis. The influence of the variability of climate elements on vegetation indices was assessed with the methods of linear regressions and spatial correlations. The results were broken down into sub-regions of similar physical-geographical features (nature-forest classification).

Identification of the relation between changing climate and forests condition seems crucial, because forests are the important element in the planetary energy balance and CO2 absorption. In Poland almost 30% of country area (9.2 million ha) is covered with forests, but such research have not been conducted so far.

How to cite: Kulesza, K. and Hościło, A.: Influence of climatic variables on forests condition in Poland in the period 2002-2021, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5932, https://doi.org/10.5194/egusphere-egu23-5932, 2023.

EGU23-6144 | ECS | Orals | BG3.5

Quantifying Tree-species Specific Responses to the Extreme 2022 Drought in Germany 

Yixuan Wang, Yuanyuan Wang, Xiaoxiang Zhu, Anja Rammig, and Allan Buras

In recent decades, forests are increasingly suffering from so-called hotter droughts. This is because rising temperatures increase the atmospheric water demand under drought, thereby amplifying plant-water consumption. As a consequence, soil-water potentials are reaching more extreme values which eventually may result in xylem cavitation and possibly tree die-back. For instance, the extreme 2018 drought resulted in extraordinary die-back frequencies in numerous tree species across Central Europe such as European beech, Norway spruce, and Scots pine. Since forests render an important agent in terms of climate change mitigation, increasing forests' climate-change resilience via forest conversion is essential to preserve their integrity and consequently ecosystem services related to carbon sequestration.

 

In this context, better knowledge of species-specific drought responses is highly valuable since it allows for determining critical drought thresholds beyond which the functional integrity of trees is at threat. Such knowledge may serve to parameterize dynamic vegetation models, which then can be deployed to project tree-species-specific performance under various climate change scenarios. Eventually, this may guide forest managers to select more climate-resilient tree species portfolios in terms of forest conversion.

 

Yet, species-specific drought responses are typically derived from plot-based physiological monitoring networks. While this approach provides valuable and highly precise data on tree physiology and it suffers from a relatively low replication. To overcome this low-spatial replication, large-scale assessments using satellite-based remote sensing appear a promising research avenue. For instance, the recently released European forest condition monitor (EFCM) provides information on forest canopy conditions in near real-time, which was shown to successfully quantify drought impacts under previous droughts (Buras et al., 2020, 2021). However, the EFCM currently does not allow for species-specific assessments given a lack of corresponding data, in particular tree-species classifications.

 

To overcome this research gap and to deepen our knowledge of species-specific drought responses, we here present a machine-learning-based tree-species classification using Moderate Resolution Imaging Spectroradiometer (MODIS) of Germany which is subsequently used to stratify EFCM data to quantify the species-specific response of most abundant tree-species (in particular beech, oak, spruce, and pine) to the extreme 2022 drought. Preliminary results indicated a successful calibration-validation of the tree-species classification, with the corresponding F1-scores in the order of 0.55 – 0.7 and true-skill statistics in the order of 0.6 – 0.78, indicating average to good performance. Once applied to stratify the EFCM data we provide a well-replicated large-scale assessment of tree-species-specific drought response, which will improve our understanding of species-specific climate-change resilience. Corresponding information can then be used further to parameterize dynamic vegetation models, which eventually can be deployed to obtain projections of tree performance under various climate-change scenarios.

 

Buras A, Rammig A and Zang C S 2020 Quantifying impacts of the 2018 drought on European ecosystems in comparison to 2003 Biogeosciences 17 1655–72

Buras A, Rammig A and Zang C S 2021 The European Forest Condition Monitor: Using Remotely Sensed Forest Greenness to Identify Hot Spots of Forest Decline Frontiers in Plant Science 12 2355

How to cite: Wang, Y., Wang, Y., Zhu, X., Rammig, A., and Buras, A.: Quantifying Tree-species Specific Responses to the Extreme 2022 Drought in Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6144, https://doi.org/10.5194/egusphere-egu23-6144, 2023.

EGU23-6641 | Orals | BG3.5

The temperature sensitivity of mono- and sesquiterpene emissions from terrestrial vegetation: Insights from a meta-analysis 

Efstratios Bourtsoukidis, Andrea Pozzer, Jonathan Williams, David Makowski, Josep Peñuelas, Vasileios Matthaios, Theo Economou, Georgia Lazoglou, Ana Maria Yañez-Serrano, Anke Nölscher, Jos Lelieveld, Philippe Ciais, Mihalis Vrekoussis, Nikos Daskalakis, and Jean Sciare

The emission of mono- and sesquiterpenes from terrestrial vegetation plays a significant role in ecological interactions and atmospheric chemistry. Previous research has suggested that global emissions of these hydrocarbons are largely driven by responses to abiotic stress and can be simulated using a fixed exponential relationship (β coefficient) between different forest ecosystems and environmental conditions. However, our meta-analysis of published emission data (89 studies/835 β coefficients) reveals that the relationship between mono- and sesquiterpene emissions and temperature is more complex than previously thought. We have found that co-occurring environmental stresses can amplify the temperature sensitivity of monoterpene emissions, which is primarily related to the specific plant functional type (PFT). In contrast, the temperature sensitivity of sesquiterpene emissions decreases over the years. On average, warmer ecosystems appear more sensitive, indicating that plants adjust their emission rates in response to thermal stress. When a PFT-dependent β coefficient for monoterpenes was implemented in a biogenic emission model and coupled with a chemistry-climate model, it was found that atmospheric processes are highly sensitive to this coefficient and subject to amplified variations under rising temperatures.

How to cite: Bourtsoukidis, E., Pozzer, A., Williams, J., Makowski, D., Peñuelas, J., Matthaios, V., Economou, T., Lazoglou, G., Yañez-Serrano, A. M., Nölscher, A., Lelieveld, J., Ciais, P., Vrekoussis, M., Daskalakis, N., and Sciare, J.: The temperature sensitivity of mono- and sesquiterpene emissions from terrestrial vegetation: Insights from a meta-analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6641, https://doi.org/10.5194/egusphere-egu23-6641, 2023.

EGU23-6833 | Posters on site | BG3.5

High vulnerability of highland Andean forests to warming 

Lina Mercado, Zorayda Restrepo, Sebastian Gonzalez-Caro, Iain Hartley, Juan Villegas Palacio, and Patrick Meir

Tropical forests are expected to be highly vulnerable to climate change. Observations from the tropical montane Andean forests report a change in composition towards a greater relative abundance of warm affiliated species, i.e thermophilic species. These shifts are hypothesised to result from differential responses to warming of cold- and warm-affiliated species, with the former experiencing mortality and the latter migrating upslope. However, the drivers of these changes are poorly understood. Along a 2000m altitudinal gradient/thermosequence in the Colombian Andes, we planted 2-yr old individuals of cold- and warm-affiliated species under common soil and water conditions, exposing them to the hot and cold extremes of their thermal niches, respectively. We show that cold-affiliated species growing outside and on the hotter portion of their thermal ranges decreased their growth. Warm-affiliated species can survive but reduce their growth under the colder portion of their thermal distribution. We demonstrate that growth responses are related to species’ thermal distributions; survival probability increased as species’ distribution optima were warmer than the experimental site and decreased as species’ distribution optima were colder than the study sites. These results can be explained by the negative effects of heat stress on simulated photosynthesis.  Our findings highlight the potential effects of rapid warming on the composition of highland forest species in this biodiversity hotspot.

How to cite: Mercado, L., Restrepo, Z., Gonzalez-Caro, S., Hartley, I., Villegas Palacio, J., and Meir, P.: High vulnerability of highland Andean forests to warming, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6833, https://doi.org/10.5194/egusphere-egu23-6833, 2023.

EGU23-8437 | ECS | Orals | BG3.5

The strength of CO2 fertilization in forests inferred from the eddy-covariance record 

Chunhui Zhan, René Orth, Hui Yang, Markus Reichstein, Sönke Zaehle, Anja Rammig, and Alexander Winkler

Carbon sequestration, particularly in forests, is assumed to increase with increasing atmospheric CO2 concentrations due to the CO2 fertilization effect on photosynthesis (CFE). Estimating the contemporary effect of increasing atmospheric CO2 on continuous measurements of gross primary production (GPP) in forest stands is still lacking as it is challenging to disentangle the CFE from other effects on GPP acting on long time scales such as climate variability, succession, land-cover change, and nutrient deposition. Here we introduce a statistical method, i.e., the “GPP residual” method, to estimate the effect of climate on GPP based on short-term variability, to remove it from the long-term signal, yielding the GPP residual that can be, at least partly, attributed to CFE.

We validate the applicability of this “GPP residual” method by testing whether it can accurately identify the CFE in simulations of the process-based land surface model QUINCY (QUantifying Interactions between terrestrial Nutrient CYcles and the climate system). We compare (i) the difference in the simulated GPP between historical simulations forced with transient and constant CO2 concentrations with (ii) the non-climatic GPP variations determined when applying the “GPP residual” method to the transient-CO2 simulation, and find encouraging agreement.

We next apply our approach to eddy-covariance derived GPP at 32 forested sites located in Europe and the US to quantify the CFE for each site and month-of-year in growing seasons. The median CFE across all site-months is 22 ± 6 % per 100 ppm change in CO2. We note that other effects, such as nitrogen deposition and land management, also influence the GPP residual and could be incorrectly attributed to CFE. Assuming that these more site-specific effects may partially cancel out across sites as random effects, the estimated median value still reflects the strength of CFE. However, causal research will be needed to disentangle these long-term effects which cannot be separated by time scale.

In summary, our study derives for the first time an observation-based estimation of the CO2 fertilization effect across forested ecosystems based on the eddy covariance record. Our results encourage future work to reconcile the uncertainties of the effect of increasing CO2 on the global carbon cycle as determined from models, experiments and observations.

How to cite: Zhan, C., Orth, R., Yang, H., Reichstein, M., Zaehle, S., Rammig, A., and Winkler, A.: The strength of CO2 fertilization in forests inferred from the eddy-covariance record, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8437, https://doi.org/10.5194/egusphere-egu23-8437, 2023.

EGU23-8927 | Orals | BG3.5 | Highlight

Record reduction in European forest canopy greenness during the 2022 drought 

Allan Buras, Benjamin Meyer, and Anja Rammig

According to climate projections, extreme summer drought conditions as those striking Central and Southern Europe in 2022 will become more frequent under climate change. Consequently, studying forests’ response to such extreme conditions may reveal important insights on how forests will cope with anticipated climate conditions. Of particular interest are questions related to forest-type specific drought sensitivities (e.g. broadleaved vs. coniferous, Mediterranean vs. temperate) and the existence of legacy effects from previous droughts (e.g. the extreme 2018 drought, see Buras et al 2020).

While many approaches exist to address these questions at local scale, satellite borne remote sensing offers the opportunity to tackle these topics at large scale. Here, the MODIS mission provides a valuable source of information due to a relatively long observational period since the year 2000 at sufficient spatial resolution (250 m x 250 m) and a high sampling frequency (daily images which are used to compute 16-day maximum value composites). In context of monitoring forests' response to environmental conditions, MODIS NDVI renders a frequently considered data source since it reflects canopy greenness and consequently mirrors – among others – early leaf coloration and senescence as direct responses of trees to extreme drought. Yet, MODIS NDVI time-series need to pass a multi-step processing chain to mask poor-quality pixels, remove remaining outliers, gap-fill, and finally apply a pixel-specific standardization to achieve relative measures of canopy greenness. The recently launched European Forest Condition (EFCM, Buras et al 2021) provides correspondingly processed data, which can be used to monitor forest canopy condition in Europe through space and time.

Here, we present first insights on the impact of the 2022 drought on European forest ecosystems based on the EFCM. Preliminary results indicate the drought 2022 to supersede previous droughts with regards to the spatial extent of severely affected pixels, thus breaking the former record from the 2018 drought (Buras et al 2020) just four years later. Our analyses suggest that legacy effects from previous years have contributed to this development. Moreover, we found different drought sensitivities of different forest types. In combination, these factors draw a complex picture of forests climate-change resilience, which we here seek to disentangle. Corresponding knowledge will likely provide valuable empirical information to improve model-based projections of tree-species performance under anticipated climate change.

Buras A, Rammig A and Zang C S 2020 Quantifying impacts of the 2018 drought on European ecosystems in comparison to 2003 Biogeosciences 17 1655–72

Buras A, Rammig A and Zang C S 2021 The European Forest Condition Monitor: Using Remotely Sensed Forest Greenness to Identify Hot Spots of Forest Decline Frontiers in Plant Science 12 2355

How to cite: Buras, A., Meyer, B., and Rammig, A.: Record reduction in European forest canopy greenness during the 2022 drought, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8927, https://doi.org/10.5194/egusphere-egu23-8927, 2023.

Regional increases in atmospheric O3, mainly produced photochemically from anthropogenic precursor gases, have phytotoxicity due to its strong oxidizing properties. To determine the response of bamboo physiology to elevated O3 levels, three-year-o