BG – Biogeosciences

BG1.2 – Fire in the Earth system: interactions with land, atmosphere and society

EGU22-2442 | Presentations | BG1.2

Pyrogenic carbon from wildfire or from the laboratory 

Daquan Sun

Wildfires remove well-developed vegetation but restore it from an ecological point of view, although they are often called disasters when their intensity and extent in forests are large. Thermochemical decomposition of organic material at high temperatures (200 - 750 °C) in the absence of oxygen (or any halogen) to decompose biosolids has been recognised as a method with numerous benefits for waste management, carbon sequestration and sustainable agriculture. The effects of pyrogenic carbon (PyC) from wildfire and from the laboratory are believed to be different. The evidence to date is informative in bridging pyrogenic carbon from wildfire and pyrolysis, including aspects of: 1) PyC as a microsite for microbial communities; 2) the role of PyC of different sizes in soil aggregation; 3) the role of the soil microbiome in soil aggregation; 4) nutrient release - phosphorus availability in PyC. Future work is needed to investigate 1) the role of nano- or micro-sized PyC in the guts of soil fauna - nutrient uptake and function of the microbiome; 2) linking municipal biowaste to carbon sequestration; 3) improving efficiency in composting and vermicomposting; and 4) negative impacts on soil fauna such as earthworms. Knowledge of PyC in materials science, waste management and environmental microbiology offers opportunities to make breakthroughs in biowaste management and climate change mitigation.

How to cite: Sun, D.: Pyrogenic carbon from wildfire or from the laboratory , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2442, https://doi.org/10.5194/egusphere-egu22-2442, 2022.

Paddy stubble burning is a major environmental issue that plagues the ambient air quality of the Indo-Gangetic Plain. Every year, during the post-monsoon season (October and November), approximately 17 million tons of paddy stubble are burnt openly in the fields of Punjab and Haryana. Over two months, this large-scale biomass burning results in persistent smog and severely perturbs the regional air quality. The emission of reactive gaseous pollutants like volatile organic compounds (VOCs) from this source drive the surface ozone and aerosol formation. However, there is a considerable knowledge gap regarding their identification, amounts and spatial distribution over North India. Widely used top-down global fire emission inventories like GFED, GFAS and FINN rely on the high-resolution MODIS and VIIRS satellite fire products. However, they are severely constrained by the missed fires, limited VOC speciation and uncertain biomass burnt calculations due to non-region-specific emission and land use parametrization factors. The current bottom-up emission estimates also have high uncertainties because of non-region-specific emission factors and burning practices. This work presents a new “hybrid” gridded emission inventory for paddy stubble burning over Punjab and Haryana in 2017 at 1 km × 1 km spatial resolution. First, the emission factors (EFs) of 77 VOCs were measured in smoke samples collected from the on-field paddy fires of Punjab. These were then combined with 1 km × 1 km stubble burning activity, constrained by annual crop production yields, regional rice cultivars, burning practices and satellite-detected fire radiative power. The results revealed that paddy stubble burning is a significant source of oxygenated VOCs like acetaldehyde (37.5±9.6 Ggy-1), 2-furaldehyde (37.1±12.5 Ggy-1), acetone (34.7±13.6 Ggy-1), and toxic VOCs like benzene (9.9±2.8 Ggy-1) and isocyanic acid (0.4±0.2 Ggy-1). These compounds are also significantly underestimated and unaccounted for by existing top-down and bottom-up emission inventories. Additionally, it was found that the emissions of NMVOC (346±65 Ggy-1), NOx (38±8 Ggy-1), NH3 (16±4 Ggy-1), PM2.5 (129±9 Ggy-1), GHG CO2 equivalents (22.1±3.7 Tgy-1) from paddy stubble were up to 20 times higher than the corresponding emissions from traffic and municipal waste burning over north-west India during October and November 2017. Mitigation of this source alone can yield massive air-quality climate co-benefits for more than 500 million people.

How to cite: Kumar, A., Hakkim, H., Sinha, B., and Sinha, V.: Gridded 1 km × 1 km emission inventory for paddy stubble burning emissions over north-west India constrained by measured emission factors of 77 VOCs and district-wise crop yield data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2565, https://doi.org/10.5194/egusphere-egu22-2565, 2022.

EGU22-4095 | Presentations | BG1.2

Emission characteristics of atmospheric pollutants from field-scale crop residue burning in Northeast China

Lili Wang, Qinglu Wang, Miaomiao Cheng, Tianran Zhang, and Jinyuan Xin

Crop residue burning in china increased significantly in the last decade, especially it took up a majority in Northeast China, which plays an important role of severe haze pollution. Hence, two main types of crop residues (corn and rice straw) were chosen to characterize the particle number concentration, chemical components of fine particulate matter and optical properties of carbonaceous aerosols by a suite of fast-response online portable instruments, together with offline sampling and analysis, during the field-based combustion experiments in Northeast China. For the range of 0.25 and 2.5 µm, more particles were emitted from rice straw burning than those from corn straw burning, and the time-averaged number concentration of particles during the flaming process was approximately 2 times higher than that during the smoldering process for these two straws. Organic carbon (OC), elemental carbon (EC) and water-soluble ions were the most abundant components and accounted for 42.5±7.5%, 7.7±1.7% and 18.0±3.4% of the PM2.5, respectively. Furthermore, rice straw burning emitted higher OC and lower Cl- and K+ than those from corn straw burning. The average absorption Ångström exponent (AAE) of carbonaceous aerosols was 2.1±0.3, while the AAE of brown carbon (BrC) was 4.7±0.4 during the whole burning process. On average, BrC contributed to 63% and 20% of the total light absorption at 375 nm and 625 nm, respectively. Parameterization of BrC absorption revealed that the fraction of absorption from BrC has a reasonably good correlation with EC/OC (-0.84) and AAE (0.94) at 375 nm. Generally, combustion conditions can affect the optical properties of carbonaceous aerosols, and a negative correlation (-0.77) was observed between the AAE and modified combustion efficiency; in addition, the percentage of absorption due to BrC were lower at the flaming phase. To explorer the spatial and temporal variability of open agricultural burning in Northeast China from 2014 to 2019, the emission inventory of key gaseous and particle pollutants was established, which derived from a combination of geostationary (Himawari) and polar (VIIRS) orbiter fire radiative power products. 

How to cite: Wang, L., Wang, Q., Cheng, M., Zhang, T., and Xin, J.: Emission characteristics of atmospheric pollutants from field-scale crop residue burning in Northeast China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4095, https://doi.org/10.5194/egusphere-egu22-4095, 2022.

EGU22-4394 | Presentations | BG1.2

Fire aerosols slow down the global water cycle

Fang Li, David Lawrence, Yiquan Jiang, and Xiaohong Liu

Fire is an important Earth system process and the largest source of global primary carbonaceous aerosols. Earlier studies have focused on the influence of fire aerosols on radiation, surface climate, air quality, and biogeochemical cycle. The impact of fire aerosols on the global water cycle has not been quantified and related mechanisms remain largely unclear. This study provides the first quantitative assessment and understanding of the influence of fire aerosols on the global water cycle. This is done by quantifying the difference between simulations with and without fire aerosols using the fully-coupled Community Earth System Model (CESM). Results show that presentday fire aerosols weaken the global water cycle significantly. They decrease the continental precipitation, evapotranspiration, and runoff by 4.1±1.8, 2.5±0.5, and 1.5±1.4 ×103 km3 yr-1 as well as ocean evaporation, precipitation, and water vapor transport from ocean to land by 8.1±1.9, 6.6±2.3, and 1.5±1.4 ×103 km3 yr-1. The impacts of fire aerosols are most clearly seen in the tropics and the Arctic-boreal zone. Fire aerosols affect the global water cycle mainly by cooling the surface which reduces ocean evaporation, land soil evaporation and plant transpiration. The decreased water vapor load in the atmosphere leads to a decrease in precipitation, which contributes to reduced surface runoff and sub-surface drainage.

How to cite: Li, F., Lawrence, D., Jiang, Y., and Liu, X.: Fire aerosols slow down the global water cycle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4394, https://doi.org/10.5194/egusphere-egu22-4394, 2022.

Ever-increasing wildfires in scale and duration have resulted in enormous human and material losses, and adverse health outcomes due to short- and long-term exposure to diverse air pollutants emitted from fires. Historically, the Mediterranean Basin, characterized by hot and dry summers, has been particularly affected by wildfires, and the situation is deteriorating as climate change worsens and the regional populations grow rapidly. To assess the health impacts due to short-term exposure to air pollution caused by the 2021 summer wildfires in eastern and central Mediterranean Basin, we demonstrate a multi-pollutant approach based on the Weather Research and Forecasting online-coupled Chemistry (WRF-Chem) model. The WRF-Chem model was used to simulate concentrations of major air pollutants such as fine particulate matter (PM2.5), SO2, NO2, and O3, in a fire and no-fire scenario. Elevated short-term exposure of the population to air pollutants were associated with excess all-cause mortality using relative risks (RRs) for individual pollutants based on previously published meta-analyses.

Our estimates indicate that the additional short-term exposure to O3, which is predicted to increase due to the wildfires, resulted in the highest number of excess deaths of 608 (95% CI: 456-771) over the entire region of investigation during the wildfire season between mid-July to early October 2021. This is followed by 270 (95% CI: 177- 370) excess deaths due to elevated PM2.5 exposure, rendering the health effect of increased O3 from wildfires larger than the effect of increased PM2.5. This is shown to be largely reasoned by the spatially more widespread impact of wildfires on O3. In contrast, the excess mortality caused by NO2 and SO2 emitted from wildfires is estimated low. This may be ascribed to the different sources of air pollutants, with NO2 a marker of traffic, while SO2 originating primarily from emissions from fossil fuel combustion, e.g., from power plants. Our study concludes with a discussion on uncertainties associated with the multi-pollutant health impact assessment and suggests a critical scrutiny of estimates based thereupon.

How to cite: Zhou, B. and Knote, C.: Multi-pollutant assessment of health impacts of 2021 summer wildfires in eastern and central Mediterranean Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7258, https://doi.org/10.5194/egusphere-egu22-7258, 2022.

EGU22-11223 | Presentations | BG1.2 | Highlight

Future fire impact on PM2.5 pollution and attributable mortality

Chaeyeon Park, Kiyoshi Takahashi, Shinichiro Fujimori, Fang Li, Vera Ling Hui Phung, Junya Takakura, Tomoko Hasegawa, and Ahihiko Ito

Fine particulate matter with a diameter of ≤ 2.5  (PM2.5), one of the hazardous air pollutants, contributed 4.5 million to 8.9 million global mortality annually. Among the total PM2.5 related mortality, 5%–21% were attributed to fires. While anthropogenic fire has been declined by reduced land fragmentation and changed land use, climate change has increased fire activities especially in fire seasons. These fires eventually lead to high PM2.5 in many regions, leading to public health concern. However, the impact of future fires on PM2.5 and its health burden according to climate change and socioeconomic scenarios has not been studied globally. We estimated fire related PM2.5 at the end of 21st century under various future scenarios (combination of Shared Socioeconomic Pathways (SSPs) and Representative Concentration Pathways (RCPs)) and its attributable mortality. We used modified CLM and GEOSChem for simulating fire emissions and PM2.5 concentration, respectively. The Global Burden of Disease (GBD) method was used for estimating attributable mortality. We also evaluated how global inequality in fire-PM2.5 mortality by income (economic inequality) would change. We found that future climate change led to higher fire-PM2.5 by increasing drought and biomass carbon density, whereas future increased GDP would offset the increase in fire-PM2.5. The results of fire-PM2.5 mortality varied significantly by SSPs. Population increase under SSP3 would lead to increase in mortality and economic inequality. The total fire-PM2.5 mortality decreased under SSP1–4, but the economic inequality increased under SSP4. If the world follows SSP1-RCP2.6 scenario, fire-PM2.5 mortality would reduce about 40% and improve economic equality.

This research was supported by the Environment Research and Technology Development Fund (JPMEERF20202002) of the Environmental Restoration and Conservation Agency of Japan.

How to cite: Park, C., Takahashi, K., Fujimori, S., Li, F., Phung, V. L. H., Takakura, J., Hasegawa, T., and Ito, A.: Future fire impact on PM2.5 pollution and attributable mortality, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11223, https://doi.org/10.5194/egusphere-egu22-11223, 2022.

EGU22-4831 | Presentations | BG1.2

Influence of Atmospheric Teleconnections on Interannual Variability of Arctic-boreal Fires

Zhiyi Zhao, Zhongda Lin, Fang Li, and Brendan M. Rogers

Fires across the Arctic-boreal zone (ABZ) play an important role in the boreal forest succession, permafrost thaw, and the regional and global carbon cycle and climate. These fires occur mainly in summer with large interannual variability. Previous studies primarily focused on the impacts of local surface climate and tropical El Niño-Southern Oscillation (ENSO). This study, for the first time, comprehensively investigates the influence of summer leading large-scale atmospheric teleconnection patterns in the Northern Hemisphere extra-tropics on interannual variability of ABZ fires. We use correlation and regression analysis of 1997–2019 multiple satellite-based products of burned area and observed/reanalyzed climate data. Results show that eight leading teleconnection patterns significantly affect 63±2% of burned areas across the ABZ. Western North America is affected by the East Pacific/North Pacific pattern (EP/NP) and the West Pacific pattern (WP); boreal Europe by the Scandinavia pattern (SCA); eastern North America, western and central Siberia, and southeastern Siberia by the North Atlantic Oscillation (NAO); and eastern Siberia /Russian Far East by the East Atlantic pattern (EA). NAO/EA induces lower-tropospheric drier northwesterly/northerly airflow passing through the east of boreal North America/Eurasia, which decreases surface relative humidity. Other teleconnections trigger a high-pressure anomaly, forcing downward motion that suppresses cloud formation and increases solar radiation reaching the ground to warm the surface air as well as brings drier air downward to reduce surface relative humidity. The drier and/or warmer surface air can decrease fuel wetness and thus increase burned area. Our study highlights the important role of the extra-tropical teleconnection patterns on ABZ fires, which is much stronger than ENSO that was thought to control interannual variability of global fires. It also establishes a theoretical foundation for ABZ fire prediction based on extra-tropical teleconnections, and has the potential to facilitate ABZ fire prediction and management.

How to cite: Zhao, Z., Lin, Z., Li, F., and Rogers, B. M.: Influence of Atmospheric Teleconnections on Interannual Variability of Arctic-boreal Fires, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4831, https://doi.org/10.5194/egusphere-egu22-4831, 2022.

EGU22-3927 | Presentations | BG1.2

Siberian fire ignition caused by the dry lightning activity

Jin-Soo Kim, Seung-Ki Min, Min-Gyu Seong, Daehyun Kim, Robert Holzworth, Ja-Ho Koo, Axel Timmermann, and Gabriela Schaepman-Strub

Wildfire activity in Siberia (60E-180E, 55N-80N) has been observed to be more frequent and stronger in recent years. To understand the underlying mechanism of the positive trend in the frequency and strength of wildfire events, especially the role of lightning, we analyzed the relationship among fire ignition, Convective Available Potential Energy (CAPE), precipitation, and lightning flash density over Siberia using observations and reanalysis products for the period 2012–2020. A similar analysis was performed on an ultra-high-resolution (25-km) climate model simulation made with Community Earth System Model version 1.2.2 (CESM) under a greenhouse gas-induced warming scenario. In the observations, we found that while the number of lightning flashes is proportional to CAPE and precipitation, the number of fire ignition is only proportional to CAPE. In particular, we identified a threshold of 3.5 mm/day of precipitation, below which fire ignition occurs more frequently. Our analyses reveal that precipitation plays a role in suppressing fire ignition, but dry lightning with high CAPE and low precipitation effectively cause fire ignitions. In the CESM simulation, we found a robust increase in the number of days with high CAPE (> 700 J/kg) and low precipitation (< 3.5 mm/day), which suggests an increase in the frequency of dry lightning events, and therefore more lightning-induced wildfire events in Siberia.

How to cite: Kim, J.-S., Min, S.-K., Seong, M.-G., Kim, D., Holzworth, R., Koo, J.-H., Timmermann, A., and Schaepman-Strub, G.: Siberian fire ignition caused by the dry lightning activity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3927, https://doi.org/10.5194/egusphere-egu22-3927, 2022.

EGU22-4551 | Presentations | BG1.2

Fire prevents the regrowth of the Amazon rainforest after complete deforestation in a fire-enabled Earth system model

Markus Drüke, Werner von Bloh, Boris Sakschewski, Wolfgang Lucht, and Kirsten Thonicke

The terrestrial biosphere is exposed to land use and anthropogenic climate change, which not only affects vegetation dynamics, but also changes land-atmosphere feedbacks. In particular, tropical rainforests are endangered by anthropogenic activities and are recognized as one of the terrestrial tipping elements. An ecosystem regime change to a new state could have profound impacts on regional and global climate, once the biome has transitioned from a forest into a savanna or grassland state. Fire is a potentially major driver in the position of the transition boundary and could hence impact the dynamic equilibrium between these possible vegetation states under a changing climate. However, systematic tests of fire-controlled tipping points and hysteretic behaviour using comprehensive Earth system models are still lacking.

Here, we specifically test the recovery of the Amazon rainforest after a complete deforestation at different atmospheric CO2 levels, by using the Earth system model CM2Mc-LPJmL v1.0 with a state-of-the-art representation of vegetation dynamics and fire. We find that fire prevents large-scale forest regrowth after complete deforestation and locks large parts of the Amazon in a stable grassland state. While slightly elevated atmospheric CO2 values had beneficial effects on the forest regrowth efficiency due to the fertilization effect, larger CO2 amounts further hampered the regrowth due to increasing heat stress. In a no-fire control experiment the Amazon rainforest recovered after 250 years to nearly its original extent at various atmospheric CO2 forcing levels. This study highlights the potential of comprehensive fire-enabled Earth system models to investigate and quantify tipping points and their feedback on regional and global climate.

How to cite: Drüke, M., von Bloh, W., Sakschewski, B., Lucht, W., and Thonicke, K.: Fire prevents the regrowth of the Amazon rainforest after complete deforestation in a fire-enabled Earth system model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4551, https://doi.org/10.5194/egusphere-egu22-4551, 2022.

EGU22-6549 | Presentations | BG1.2

Remote sensing of tropical vegetation properties in response to fire return time

Ramesh K. Ningthoujam, Nayane Cristina Candida dos Santos Prestes, Marcelo Feitosa de Andrade, Maria Antonia Carniello, Corli Wigley Coetsee, Mark E. Harrison, Kitso Kusin, Azad Rasul, Agata Hoscilo, Adam Pellegrini, Imma Oliveras, Ted R. Feldpausch, Susan Page, Keith J. Bloomfield, Sandy P. Harrison, and Iain Colin Prentice

Fire modifies vegetation spectral reflectances in the optical, thermal and microwave domains due to the changes it induces in vegetation canopy components (leaves, needles, branches) and in soil properties. Freely available satellite-derived (Landsat) Vegetation Indices (VIs) and PALSAR Mosaic backscatter measurements (known to be sensitive to vegetation structure) were used to help understand vegetation properties (species richness, basal area) in relation to fire return time (FRT) across a range of tropical biomes (open savanna, savanna forest, evergreen forest, peat-swamp forest) in Mato Grosso (Brazil), Kruger National Park (South Africa) and Central Kalimantan (Indonesia).

For each site, we combined: (i) post-fire Landsat imagery (30 m) to derive VIs sensitive to vegetation diversity with (ii) PALSAR (25 m) backscatter that employes a longer wavelength (21 cm) and dual polarisation (Horizontal-Horizontal, Horizontal-Vertical) enabling the capture of strong backscattering of signal by branches and trunks.

Most of the Landsat VI values showed greater variability in forests compared to open savanna, reflecting the greater diversity in species’ composition and growth form. A strong positive relationship was found between VIs and FRT across biomes and especially in forests. The amount of vegetation burned per fire as recorded by the magnitude of changes in these VIs, was highest in annual burn regimes (FRT = 1 year). Green and red-edge bands provided better discrimination of vegetation species richness and basal area. A significant positive relationship to basal area in response to fire return time was also found using PALSAR data due to its deeper canopy penetration level and strong backscattering from woody components. The observed responses of VI- and PALSAR-inferred species’ richness and basal area in response to FRT in different tropical biomes suggest that the green and red-edge channels from optical and longer wavelength HV-backscatter are useful metrics to quantify post-fire tropical vegetation dynamics.

How to cite: Ningthoujam, R. K., Prestes, N. C. C. D. S., Andrade, M. F. D., Carniello, M. A., Coetsee, C. W., Harrison, M. E., Kusin, K., Rasul, A., Hoscilo, A., Pellegrini, A., Oliveras, I., Feldpausch, T. R., Page, S., Bloomfield, K. J., Harrison, S. P., and Prentice, I. C.: Remote sensing of tropical vegetation properties in response to fire return time, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6549, https://doi.org/10.5194/egusphere-egu22-6549, 2022.

Fires play a critical role in global biogeochemical and hydrological cycles through influencing vegetation succession and ecosystem functioning. Observational evidence shows that fire regimes across global ecosystems have been altered by climate change and human activities. However, most fire-enabled terrestrial biosphere models (TBMs) poorly capture the spatial and temporal patterns of fire ignitions, burned area, vegetation mortality and post-fire recovery. To improve our ability in predicting fire behavior and its impacts on the ecosystem and climate, it is essential to better represent fire-vegetation interactions in TBMs. Here, we improve the fire module of the Dynamic Land Ecosystem Model (DLEM-Fire) and optimize the parameters by using the satellite observed fire ignitions, burned area and leaf area index (LAI) products. Our results show that the improved fire model can describe the magnitude, spatial patterns, and interannual variations of burned area and vegetation mortality more accurately. Moreover, the model is capable of providing robust estimations of post-fire vegetation regeneration to characterize the vegetation resistance and resilience to fire disturbances. This study emphasizes the importance of integrating terrestrial biosphere models and satellite observation data for fire monitoring and prediction.

How to cite: Li, X., Tian, H., Yang, J., You, Y., and Pan, S.: Understanding and quantifying fire-vegetation interactions through integrating satellite observation data with the Dynamic Land Ecosystem Model (DLEM), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5893, https://doi.org/10.5194/egusphere-egu22-5893, 2022.

EGU22-8767 | Presentations | BG1.2

The Impacts of the 2017 Catastrophic Fire Season in Portugal on Vegetation Productivity

Tiago Ermitão, Célia Gouveia, and Ana Russo

Wildfires have become a serious threat to ecosystems and human society over the last years of the 21st century, with many hectares being destroyed every year globally. The lengthening of the fire seasons and the increase of wildfires risk, which have been promoted by climate change, input many losses on society, economy and mostly in diverse ecosystems. In Portugal, the 2017 catastrophic fire season burned more than 450,000 hectares and caused the death of more than 100 people. In this context, relying on remotely sense products from MODIS collections, our study proposes an analysis of the effect of summer heat and water availability deficit in vegetation productivity decline that led to large fires propagation, especially in June and October of 2017. With the aim to evaluate the magnitude of the impact that compound or cascading extreme events had on the vegetation productivity decline, considering the 2001-2019 historical values, we defined three different classes of pixels that should reflect the conditions before the fire: affected by hot, by dry or by hot/dry conditions. Moreover, we assess the influence of favourable winter/spring meteorological conditions on enhancing vegetation productivity that promote high fuel accumulations susceptible to burn some months later. Our results reinforce the water and energy dependency of the vegetation of the region during the growing season and highlight that the combination of higher temperatures and water availability in spring can trigger summer wildfires propagation, flammability and intensity due to the accumulation of biomass. Considering that the example of 2017 can be more recurrent under the context of climate change, this study also highlights the need to improve the awareness strategies in fire prone regions like Portugal, especially on biomass accumulation control during growing season.

This study was supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project FIRECAST (PCIF/GRF/0204/2017) and IMPECAF (PTDC/CTA-CLI/28902/2017).

How to cite: Ermitão, T., Gouveia, C., and Russo, A.: The Impacts of the 2017 Catastrophic Fire Season in Portugal on Vegetation Productivity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8767, https://doi.org/10.5194/egusphere-egu22-8767, 2022.

EGU22-1916 | Presentations | BG1.2

Application of biochar to irrigated technosoils: Effects on germination and agronomic properties

José María De la Rosa, Paloma Campos, Arturo Santa-Olalla, Águeda Sanchez-Martín, Ana Miller, and Elena Fernández-Boy

Today's agriculture faces the challenge of safely feeding a growing population. This situation generates additional pressures on the environment such as increased organic waste generation, irrigated cropland and the consumption of mineral fertilizers. Moreover, in the present context of global warming, it is necessary to transform the linear economy into a circular economy, in which organic waste should be valorized and greenhouse gas emissions reduced. During the last decade the transformation of organic waste into biochar, the carbon-rich material produced during pyrolysis of biomass to be applied as soil ameliorant [1], to increase the amount of pyrogenic C at soils have been developed [2]. Here, green compost and biochar were produced from contrasting agricultural wastes and applied at greenhouse under limited irrigation conditions.

Results showed that raw material, together with the pyrolysis conditions, determined physical properties of biochars, and thus its performance as soil amendment. In all cases, an increase in the pyrogenic carbon content and a general improvement in the physical properties of agronomic interest of the technosoils were observed. However, the use of high doses of olive-pomace biochar negatively affected the germination due to its high salinity.

Biochar, although beneficial, is therefore not a universal solution and must be characterized, have the appropriate properties and be applied in a specific way to correct specific soil deficiencies.

Acknowledgements: The BBVA foundation is gratefully acknowledged for funding the scholarship Leonardo to “Investigadores y Creadores Culturales 2020” (Proyecto realizado con la Beca Leonardo a Investigadores y Creadores Culturales 2020 de la Fundación BBVA).

References:

[1] Campos, P., Miller, A., Knicker, H., Costa-Pereira, M., Merino, A., De la Rosa, J.M., 2020. Waste Manag., 105, 256-267.

[2] De la Rosa, J.M., Rosado, M., Paneque, M., Miller, A.Z., Knicker, H., 2018. Sci. Tot. Environ., 613-614, 969-976.

How to cite: De la Rosa, J. M., Campos, P., Santa-Olalla, A., Sanchez-Martín, Á., Miller, A., and Fernández-Boy, E.: Application of biochar to irrigated technosoils: Effects on germination and agronomic properties, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1916, https://doi.org/10.5194/egusphere-egu22-1916, 2022.

In this work, a multi-sensors temporal and spatial approach was carried out to monitor the vegetation post-fire recovery rate in a Mediterranean site (in part falling within the Nature2000 network) through the use of the optical Sentinel-2 and SAR C-band Sentinel-1 imagery temporal-series. The study area was observed for one year before and three years after the fire event. Several vegetation indices (VIs) were calculated for both optical (normalized difference vegetation index, NDVI; green NDVI, GNDVI; normalized red-edge vegetation index, NDRE, normal burn index, NBR; normalized difference water index, NDWI) and SAR (radar vegetation index, RVI; dual-polarized SAR vegetation index, DPSVI; radar forest degradation index, RFDI) data from which the temporal spectral profiles were extracted in the function of one of the three vegetation types (natural/semi-natural native forest, eucalyptus plantation and grasslands), of the burn-severity gradient, and of the orbit path of SAR satellite. What emerged is that the recovery spectral dynamics are highly influenced in terms of time and magnitude by both vegetation type and, mainly, burn severity. Optical Sentinel-2 observations showed that native woody and non-woody vegetation presented higher efficiency in restoring the ecological and physiological equilibrium by the observed time, whereas C-band SAR Sentinel-1 information seems to point out that the structural characteristics cannot be recovered in such a short time, although both the data appeared impacted by saturation. Climate variables, in particular monthly rainfall, compared and correlated with the temporal spectral profiles,  demonstrated to be very influential on the SAR signal, especially for a higher degree of burn severity. The spatial distribution of the post-fire recovery rate was estimated by calculating the burn recovery ratio (BRR), optimized using the random forest (RF) machine learning regressor model to account the natural phenological changes which affect unburned vegetation during the time.  The BRR results validated what had been recorded in the temporal profiles. The effectiveness of open-source data, software, and models interoperability for post-risk monitoring purposes of vulnerable habitats was also emphasized in this study.

How to cite: De Luca, G., Silva, J. M. N., and Modica, G.: Temporal and spatial analysis for post-fire vegetation recovery in a Mediterranean site. An approach using optical Sentinel-2 and SAR Sentinel-1 imagery., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12542, https://doi.org/10.5194/egusphere-egu22-12542, 2022.

EGU22-10772 | Presentations | BG1.2

The impact of heat waves in forest fires over the Amazon rainforest

Luiza Narcizo, Filippe LM Santos, Leonardo F. Peres, Ricardo Trigo, and Renata Libonati

Wildfires have become an imminent threat to ecosystems, consequently leading to economic loss and generating negative impacts on population health. Considering IPCC’s projection of a significant increase in the frequency of these events, it is important to understand which conditions lead to a fire intensification, as recently happened in California, Australia, and Brazilian Pantanal. Some of the greatest wildfires registered in North America and in Europe occurred in concomitance to intense heat waves and drought events. The lack of a comprehensive understanding of the physical mechanisms associated with extreme wildfire events in the Amazon rainforest, underlines the current inability to properly prevent them. Therefore, this study aimed to identify the role of extreme temperature events, such as heat waves (HW), in forest fires behaviour in the Brazilian Amazon during extreme drought years. The relationship between wildfires and HWs was hereby analysed during both dry and wet years in the Amazon Forest, in order to understand the association between different time and spatial scale events in forest fires magnitude. Accordingly, CPC/NOAA reanalysis data of daily maximum temperature between 1979 and 2019 were used as input to determine HW events in a multi-method global heatwave and warm-spell data record and analysis toolbox1. A standard HW definition was applied, where an event corresponds to at least three consecutive days in which the maximum temperature exceeds the 90th percentile for that day. Wildfire magnitude analyses were calculated through active fire (AF) and fire radiative power (FRP) data from MODIS C6 sensor, obtained at FIRMS/NASA for the comprehended period between 2003 and 2019. Spatial intensity of HW was classified and then confronted with precipitation anomaly in both normal and dry years. Also, statistical comparison of fire magnitude (i.e., AF and FRP) in HW and non heat wave (NHW) days was analysed to measure extreme temperature events impacts in wildfire. Results showed a significant increasing trend in HW occurrences in recent decades, with peaks in known drier years. An increase of AF counting and fire intensity was noticed during HW events. This latter effect appears even when the HW occurs during extremely dry seasons, such as happened at the Amazon Forest in 2005, 2010 and 2015. Extreme values of AF and FRP were a quarter higher in 2005, doubled in 2010 and tripled in 2015 at HW days when compared to NHW days.

 

References 

[1] Raei, E., Nikoo, M., AghaKouchak, A. et al. GHWR, a multi-method global heatwave and warm-spell record and toolbox. Sci Data 5, 180206 (2018).

Acknowledgements

This study was supported by FAPERJ project number E26/202.714/2019. L. N. was supported by CNPq PIBIC  number 160099/2021-8.

How to cite: Narcizo, L., Santos, F. L., Peres, L. F., Trigo, R., and Libonati, R.: The impact of heat waves in forest fires over the Amazon rainforest, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10772, https://doi.org/10.5194/egusphere-egu22-10772, 2022.

EGU22-4571 | Presentations | BG1.2

Molecular characterisation of soil organic matter under different burned vegetation canopies

Nicasio T. Jiménez-Morillo, Ana Z. Miller, Nuno Guiomar, José M. De la Rosa, Cristina Barrocas-Dias, Ana Manhita, and José A. González-Pérez

Forest fires are a recurrent ecological phenomenon in the Mediterranean basin. They induce molecular changes in soil organic matter (SOM) leading to immediate and long-term environmental consequences [1]. The SOM is of paramount importance as indicator of soil health [2]. Fire-induced changes in SOM include the alteration of biogenic chemical structures and the accumulation of newly formed ones, enhancing dynamics in the complex balance between the different C-types [2,3]. Therefore, understanding SOM molecular composition, before and after fire, is fundamental to monitor changes in soil health, as well as its natural or man-mediated recovery [3,4]. Our aim was to assess the molecular composition of organic matter in fire-affected leptosols, at two depths (0–2 and 2–5 cm) under different vegetation types located in the southwestern of Portugal (Aljezur, Algarve). The SOM characterization was conducted by analytical pyrolysis (Py-GC/MS), a technique based on the thermochemical breakdown of organic compounds in the absence of oxygen at elevated temperatures [5]. The Py-GC/MS has been found suitable for the structural characterization of complex organic matrices [4], providing detailed structural information of individual compounds considered fingerprinting of SOM. However, due to the relative high number of molecular compounds released by analytical pyrolysis, the use of graphical-statistical methods, such as van Krevelen diagrams, are usually applied to help monitoring SOM molecular changes produced by fire [3,4]. This work represents the first attempt to evaluate the fire effects in SOM using a detailed molecular characterisation of SOM under different vegetation canopies, recently affected by wildfire, in southern Portugal.

 

References:

[1] Naveh, Z., 1990. Fire in the Mediterranean – a landscape ecological perspective. In: Goldammer, J.G., Jenkins, M.J. (Eds.), Fire in Ecosystems Dynamics: Mediterranean and Northern Perspective. SPB Academic Publishing, The Hague.

[2] González-Pérez, J.A., González-Vila, F.J., Almendros, G., Knicker, H., 2004. The effect of fire on soil organic matter—a review. Environ. Int. 30, 855–870.

[3] Jiménez-Morillo, N.T., De la Rosa, J.M., Waggoner, D., et al., 2016. Fire effects in the molecular structure of soil organic matter fractions under Quercus suber cover. Catena 145, 266–273.

[4] Jiménez-Morillo, N.T.; Almendros, G.; De la Rosa, J.M.; et al., 2020. Effect of a wildfire and of post-fire restoration actions in the organic matter structure in soil fractions. Sci. Total Environ. 728, 138715.

[5] Irwin, W.J., 1982. Analytical pyrolysis—a comprehensive guide. In: Cazes, J. (Ed.), Chromatographic Science Series, 22: Chapter 6. Marcel Dekker, New York.

 

Acknowledgments: This work was funded by national funds through FCT–Fundação para a Ciência e a Tecnologia (EROFIRE project, ref. PCIF-RPG-0079-2018). This research was funded by the European Union through the European Regional Development Funds in the framework of the Interreg V A Spain-Portugal program (POCTEP) through the CILIFO (Ref.: 0753_CILIFO_5_E) and FIREPOCTEP (Ref.: 0756_FIREPOCTEP_6_E) projects. In addition, this research was funded by the EU-FEDER co-funded project MARKFIRE (ref. P20_01073) from Junta de Andalucía. A.Z.M was supported by a CEECIND/01147/2017 contract from FCT, and a Ramón y Cajal contract (RYC2019-026885-I) from the Spanish Government (Ministerio de Ciencia en Innovación – MCIN).

How to cite: Jiménez-Morillo, N. T., Miller, A. Z., Guiomar, N., De la Rosa, J. M., Barrocas-Dias, C., Manhita, A., and González-Pérez, J. A.: Molecular characterisation of soil organic matter under different burned vegetation canopies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4571, https://doi.org/10.5194/egusphere-egu22-4571, 2022.

EGU22-4271 | Presentations | BG1.2

Forest fire risk assessment with soil data in Croatia

Diana Škurić Kuraži, Ivana Nižetić Kosović, and Ivana Herceg Bulić

Forest fire research can comprise forest fire case studies, laboratory experiments, fire detection by ground sensors, unmanned aerial vehicles and satellites, development of fire behaviour models, fire danger forecast, fire risk assessment, and much more. Commonly used and accepted Canadian method for forest fire danger forecast is expressed as Fire Weather Index (FWI) uses weather data. The index estimates the danger of wildfire and is based on meteorological parameters (air temperature, air humidity, wind speed, and rainfall amount) referring to 12 UTC for that day at the meteorological station or on a numerical weather prediction model grid point.

Knowing how weather and soil interact and affect each other, we propose a new fire risk index based on the innovative Soil Index. Using open-access data, we collected different soil data such as soil temperature and soil moisture, land cover, vegetation, slope, etc. Since there are different types of vegetation and states, Leaf Area Index (LAI) and Normalized Difference Vegetation Index (NDVI) are considered as well. Being focused on forest fires, data about the burned area were also taken into account as well as the slope of the terrain for which the fire risk is calculated.

Since all mentioned data have a diverse horizontal and temporal resolution, we decided to group them by temporal resolution: static, semi-static, and dynamic data. Static data refers to data that rarely change (never or every few years; e.g. land cover). Semi-static data refers to data that vary weekly or monthly (e.g. LAI). Dynamic data group refers to data that is strongly influenced by weather conditions (like soil temperature) and varies every hour. Because of various horizontal resolutions, soil parameters are interpolated to the same horizontal grid. Soil parameters are analysed concerning historical forest fires in Croatia. Despite Soil Index being based on soil parameters, we compared it with Fire Weather Index using data records for historical forest fires in Croatia. Obtained results indicate that the soil index has a better prediction performance compared to FWI. This study also highlights that not only the meteorological environment but also soil conditions are important parameters for fire risk assessment.

How to cite: Škurić Kuraži, D., Nižetić Kosović, I., and Herceg Bulić, I.: Forest fire risk assessment with soil data in Croatia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4271, https://doi.org/10.5194/egusphere-egu22-4271, 2022.

EGU22-10035 | Presentations | BG1.2

Live fuel moisture content approach using satellite data for Portugal mainland

Catarina Alonso, Rita Durão, and Célia Gouveia

The fuel moisture content (FMC) is an important property to assess fire danger, to control fuel ignition and fire propagation. The wetting and drying rates of the fuels are driven by the fuel characteristics and weather conditions, being FMC strongly driven by solar radiation influencing fuel temperature in the highly exposed fuels. Usually, FMC is divided into Dead Fuel Moisture Content (DFMC) and Life Fuel Moisture Content (LFMC). LFMC is not easily estimated due to plants’ adaptation to drought and capacity of extracting water from soils that significantly vary among different vegetation species. Extreme climate events (such as droughts and heatwaves) are important factors addressed to fire danger assessment and related activities, due to their significant impacts on fuel conditions and in the vegetation status. High-impact mega-fires have been reported over areas where biomass and fuel accumulation present significant amounts. Therefore, the estimation LFMC is a useful approach to improve fire danger assessment, bringing also advantages in the study of the dynamics of biodiversity and biomass understory recovery.

Although LFMC in-situ measurements have limited spatial coverage and temporal sampling, the use of remote sensing data is essential to overcome space-time constraints and to develop methodological approaches to assess space-time LFMC variations over Portugal. Accordingly, to previous studies, LFMC estimation results improve when using a vegetation index together with the minimum temperature. The Leaf Area Index (LAI) is a quantitative measure of the amount of live green leaf material present in the canopy per unit ground surface. Since LAI and LFMC are interdependent variables with similar seasonal and interannual trends, it is possible to estimate LFMC based on LAI data.

The present work aims to obtain LFMC statistical model to pixel by pixel for Portuguese national scale, using LAI and Land Surface Temperature (LST) products, delivered by the EUMETSAT Land Surface Analysis Satellite Applications Facility (LSA SAF) and LFMC in-situ data for Atlantic Scrub that are routinely collected over 10 monitoring sites by AGIF (Agência para a Gestão Integrada de Fogos Rurais, IP).

Results revealed very good correlation values between LFMC in-situ data and LFMC estimated, ranging between 0.68 and 0.92, decreasing to values ranging from 0.30 and 0.90, highlighting the robustness of the model in the majority of the locations.  These results vary spatially, being higher over the most sampled locations, as expected; and have the drawback of being site-specific. The influence of LAI is higher than the minimum of LST however being less important LST in the northeast of Portugal.  Further work will focus on the assessment of the remote sensing-based LFMC estimations uncertainty and the linking of LFMC to fire danger and behavior.

 

Acknowledgments: This study was performed within the framework of the LSA-SAF, co-funded by EUMETSAT and was partially supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project FIRECAST (PCIF/GRF/0204/2017) and by the 2021 FirEUrisk project funded by European Union’s Horizon 2020 research and innovation programme under the Grant Agreement no. 101003890).

How to cite: Alonso, C., Durão, R., and Gouveia, C.: Live fuel moisture content approach using satellite data for Portugal mainland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10035, https://doi.org/10.5194/egusphere-egu22-10035, 2022.

EGU22-6512 | Presentations | BG1.2

Likely future(s) of global wildfires

Douglas I Kelley, Camilla Mathison, Chantelle Burton, Megan Brown, Andrew Sullivan, Elaine Baker, and Tiina Kurvits

We show likely substantial increases in burning by 2100 in Boreal and Tropical Forests irrespective of future emissions and after accounting for the (often considerable) uncertainties and biases in global fire and climate modelling. Rather than projecting future fire regimes directly, we used the ConFire Bayesian framework to model the likelihood of all possible future burning levels given historic fire and climate model performance. Driving the framework with bias-corrected outputs from four ISIMIP2b GCMs run under RCP2.6 and RCP6.0 accounts for uncertainties in future emissions and climate model projections. 

While we forecast the potential for substantial shifts in fire regimes of much of the world by the end of the century, many show low likelihood given our confidence in the fire, vegetation and climate model projections. Tropical savannas show the largest potential for change, though without confidence in the direction of change due to uncertainty in future precipitation projections.  An increase in dry fuel drives an increase in burnt area in northern Australia. However, this is not significant against uncertainty associated with present-day veg/fire model performance. There is a significant agreement for decreased burning in Southern Brazil, Uruguay and northern Argentina, and the US east coast under RCP2.6, but not RCP6.0.

We do show a high likelihood of drying fuel loads driving an increase in burning in Indonesia, Southern Amazon, central and eastern Siberian Taiga and many Arctic areas across RCPs. These areas are of particular concern given the potential to release the high carbon content of forests and peatlands irrecoverable carbon. Mitigating from RCP6.0 to 2.6 will likely alleviate some though not all of this burning. This is important for future mitigation planning and determining likely temperature and emission targets to avoid the worst impacts of fire in our warmer world.

How to cite: Kelley, D. I., Mathison, C., Burton, C., Brown, M., Sullivan, A., Baker, E., and Kurvits, T.: Likely future(s) of global wildfires, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6512, https://doi.org/10.5194/egusphere-egu22-6512, 2022.

EGU22-1671 | Presentations | BG1.2

Representing socio-economic factors in INFERNO using the Human Development Index

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

INFERNO human fire ignitions and fire suppression functions excluded the representation of socio-economic factors (aside population density) that can affect anthropogenic behaviour regarding fire ignitions. To address this, we implement a socio-economic factor in the fire ignition and suppression parametrisation in INFERNO based on an Human Development Index (HDI) term. The HDI is calculated based on three indicators designed to capture the income, health, and education dimensions of human development. Therefore, we assume this leads to a representation where if there is more effort in improving human development, there is also investment on higher fire suppression by the population. Including this representation of socio-economic factors in INFERNO we were able to reduce large positive biases that were found for the regions of Temperate North America, Central America, Europe and Southern Hemisphere South America without significant impact to other regions, improving the model performance at a regional level and better representing processes that drive fire behaviour in the Earth System.

How to cite: Teixeira, J., Burton, C., Kelley, D. I., Folberth, G., O'Connor, F. M., Betts, R., and Voulgarakis, A.: Representing socio-economic factors in INFERNO using the Human Development Index, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1671, https://doi.org/10.5194/egusphere-egu22-1671, 2022.

Fire danger rating systems (FDRS) are widely used for many purposes from planning for daily deployment of fire suppression resources to the evaluation of fire management strategies. FDRS can also be incorporated in different types of models to assess the short and long-term effects of specific fire regimes and fire management policies.

The Canadian Forest Fire Weather Index System (CFFWIS) is one of the most known FDRS’s, being extensively used for a fire early warning in several regions around the world, namely in Europe. The CFFWIS includes a set of 6 indices, based on meteorological data, which is used to predict fire weather danger and fire behavior over regions under study. To obtain a reliable assessment of the fire danger based on the CFFWIS it is crucial to determine the threshold values for each class of the CFFWIS sub-indices over different regions. One of the simplest methods to define the classes is to use percentiles based on historical data, but this method lacks information regarding wildfire history and its relation to CFFWIS sub-indices.

The proposed method is based on Fire Radiative Energy (FRE) released by fires, computed from Fire Radiative Power (FRP) product, that is generated, and disseminated in near real-time by EUMETSAT Land Surface Analysis Satellite Applications Facility. Since FRP estimates the radiative power emitted by a fire, it can be linked to fuel burned amounts and used as a proxy of fire intensity. By integrating FRP measures over a fire’s lifetime, an estimate of the total FRE released can be obtained for each event. In this work, daily FRE was derived for the 2010-2021 period, over the Mediterranean region countries. Thresholds values of each defined danger class for the FWI, FFMC, and ISI indices were obtained considering the FRE percentiles computed for different regions of the Mediterranean basin and discussed based on the different fire regimes for the region. A trend analysis of the CFFWIS sub-indices was performed to assess the fire danger behavior and the extreme fire weather over the different Mediterranean regions.

The regions where the extreme fire weather conditions have become more prevalent were identified considering the spatial correlations, and applying field significance testing allows the identification of the regions with significant trends. Since fire regimes in Southern Mediterranean countries have been changing over the last two decades, mostly due to climate-driven factors changes and to the load and structure of fuels, the observed trend towards warmer and drier conditions are expected to continue in the next years, possibly leading to an increased risk of large fires. In this context, the knowledge of fire danger trends and variability is a key factor for fire managing activities, planning and preparedness, and resources allocation.

Acknowledgments:

This study was performed within the framework of the LSA-SAF, co-funded by EUMETSAT and was partially supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project FIRECAST (PCIF/GRF/0204/2017) and by the 2021 FirEUrisk project funded by European Union’s Horizon 2020 research and innovation programme under the Grant Agreement no. 101003890).

How to cite: Durao, R., Silva, M., Alonso, C., and Gouveia, C.: Calibration of the Fire Danger Classes and Trend analysis over the Mediterranean basin, based on the Canadian Forest Fire Weather Index System and the Fire Released Energy from SEVIRI/MSG. , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9651, https://doi.org/10.5194/egusphere-egu22-9651, 2022.

EGU22-12805 | Presentations | BG1.2

The role of meteorological factors on interannual variability of fire activity in Iberia: an assessment performed over four subregions

Carlos C. DaCamara, Sílvia A. Nunes, and José M.C. Pereira

The Iberian Peninsula is recurrently affected by devastating wildfires that result from an interplay of human activities, landscape features, and atmospheric conditions. The fact that the Mediterranean basin, and the Iberian Peninsula in particular, is a hotspot of climate change, strongly suggests that particular attention should be devoted to the role played by atmospheric conditions on wildfire activity.

Here we present a statistical model that is able to simulate the probability of occurrence of a fire event that releases a given amount of Fire Radiative Power, provided a specified level of meteorological fire danger as rated by the Fire Weather Index.

The model combines a lognormal distribution central body with a lower and an upper tail, both consisting of Generalized Pareto (GP) distributions, and daily FWI is used as a covariate of the parameters of the lognormal and the two GP distributions.

The Iberian Peninsula is subdivided into four spatially homogeneous pyro-regions, namely the northwest(NW), southwest (SW), north (N) and east (E) regions. Fire data cover the period 2001-2020 and consist of Fire Radiative Power (FRP) as acquired by the MODIS instrument on-board Aqua and Terra Satellites. Fire Weather (FWI) data covering the same period were obtained from the Copernicus Emergency Management Service.

For each region, the statistical model is fitted to the sample of FRP of all recorded events. First a base model (with fixed parameters) is fitted to the decimal logarithm of FRP, and the quality of fit is assessed using an Anderson-Darling test. Then the model is improved using FWI as a covariate, and performances of models without and with covariate are compared by computing the Bayes Factor as well as by applying the Vuong’s closeness test.

For each region, a set of 100 synthetic time series of total annual FRP is set up using the statistical models without and with FWI as a covariate. This is achieved by randomly generating probabilities for each observed event, generating the FRP associated to that probability and then adding up the generated FRP all events for each year. The interannual variability of synthetic time series obtained is then compared with the corresponding interannual variability of the recorded events.

Results obtained for region SW show an increase from 91 to 96% of interannual explained variance of FRP when going from the model without to the model with FWI. Increases from 95 to 96%, 84 to 90% and from 78 to 86% were obtained for regions NW, N and E. It is worth stressing that these are conservative estimates of change since the dependence of number of ignitions on FWI was not taken into account.

 

This work was supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project FIRECAST (PCIF/GRF/0204/2017).

How to cite: DaCamara, C. C., Nunes, S. A., and Pereira, J. M. C.: The role of meteorological factors on interannual variability of fire activity in Iberia: an assessment performed over four subregions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12805, https://doi.org/10.5194/egusphere-egu22-12805, 2022.

EGU22-5199 | Presentations | BG1.2

Global changes, fire and spruce-forest dynamics in Québec-Labrador during the Holocene.

Jonathan Lesven, Milva Druguet-Dayras, Laurent Millet, Adam Ali, Yves Bergeron, André Arsenault, François Gillet, and Damien Rius

Context

Boreal ecosystems provide numerous goods and services essential to human activities, such as wood and paper supply or the regulation of natural phenomena (floods, diseases) (Hassan et al., 2005). They also play a major role in the global climate balance, storing ~32% of the world's biogenic carbon (Pan et al., 2011; Bradshaw, 2015). Their dynamics are also intrinsically linked to fire activity, main disturbance driver in North American boreal forests (Kuuluvainen and Aakala, 2011), mainly controlled by climate-vegetation interactions (Ali et al., 2012). Under global warming, recent work predicts an increase of fire regimes, and a potential shift of the carbon sink function (Walker et al., 2019). However, Labrador and eastern Quebec regions remain poorly studied on multimillennial time scales. This study provides new insights on fire-climate-vegetation interactions in eastern Canadian forests, allowing us to better characterize the mechanisms by which climate change impacts fire regimes, and consequently forest structure and functioning.

 

Material and methods

To cover a wide range of fire-climate-vegetation interactions, this study is based on a North-South transect of 5 lacustrine sediment cores, covering the last 6,000 to 10,000 years across Quebec and Labrador regions. Chronologies were based on 210Pb/137Cs and 14C dating. Finally, to reconstruct local fire regimes, vegetation dynamics and climatic fluctuations during the Holocene, our study is based respectively on macrocharcoals (≥ 150 µm), pollen grains and chironomids assemblages.

 

Results and Discussion

Our study reveals that black spruce (Picea mariana (Mill.)) is the dominant species across the transect, but its proportion varies greatly, and is marked by a codominance with balsam fir in the south and with green alder in the north. In the south (white birch fir stand and spruce-lichen woodlands bioclimatic domains), our results show a high frequency but relatively low fire sizes during the warmest and driest periods, such as the Holocene Climate Optimum (HCO), followed by a reverse trend during the coldest and wettest periods such as the Neoglacial Period (NG), probably due to a longer fuel accumulation time promoting larger fires (Carcaillet et al., 2001). In the North (forest tundra bioclimatic domain), the HCO is marked by the absence of fire, whereas the NP is characterised by a strong increase in fire frequency, related to the progressive increase of black spruce after the deglaciation. Despite this north-south contrast, possibly related to the impact of the Atlantic Ocean, all sequences show an increase in both fire frequency and size after the industrial revolution, inducing a major change in vegetation trajectory towards more open environments marked by an increase in pioneer taxa.

 

Conclusion

During the Holocene, climate change induced variations in fire regimes in eastern Canada, but show spatial differences explained by black spruce dynamics and moisture inputs. Our study also reveals that temperature rises over the last 150 years have led to an increase in the frequency and size of fires and consequently to a progressive opening of the environment. This could ultimately alter the carbon sink function of boreal forests in the future (Bastianelli et al., 2017).

How to cite: Lesven, J., Druguet-Dayras, M., Millet, L., Ali, A., Bergeron, Y., Arsenault, A., Gillet, F., and Rius, D.: Global changes, fire and spruce-forest dynamics in Québec-Labrador during the Holocene., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5199, https://doi.org/10.5194/egusphere-egu22-5199, 2022.

EGU22-11099 | Presentations | BG1.2

Reconstructing fire regimes using micro-charcoal in modern marine sediments off Africa

Aritina Haliuc, Anne-Laure Daniau, Florent Mouillot, Wentao Chen, Valérie David, Vincent Hanquiez, Bernard Dennielou, Enno Schefuß, Germain Bayon, and Xavier Crosta

Fire is a pervasive component of almost every terrestrial ecosystem, but the African continent is rather unique, holding the most vulnerable ecosystems to fire which account for most of the global burned area and for more than half of fire-carbon emissions. Fire has a significant role in ecosystem functioning though our understanding of this complex process is still limited which hinders our ability to model and predict fire.

Paleofire records go beyond the short instrumental records of the last decades and can provide long-term information about fire, but only at a descriptive scale and with difficulties in relating it to the fire regime. To address these limitations, we attempt to develop a quantitative calibration model based on the examination of micro-charcoal from 137 surface sediment samples collected offshore the African continent in conjunction with a set of fire parameters (burnt perimeter, fire radiative power, fire spread) derived from satellite data, environmental information (hydrographic basins, vegetation cover, climatic parameters) and a wind dispersal particle model. Our results show that changes in charcoal concentration and morphometry are linked with fire regime and the type of burnt vegetation on the adjacent continent. In (sub)tropical settings, elongated micro-charcoal particles in high concentrations relate to rare but intense fires spreading in graminoid-mixed ecosystems whereas squared particles in low concentrations are typical for frequent but low intensity fires, characteristic for tree-dominated ecosystems.

This work provides the first calibration model of micro-charcoal in marine sediments which can be applied to long marine charcoal records to help reconstruct past fire regimes. This investigation addresses a key issue in unlocking specific methodological and theoretical problems related to fire research; it provides a better understanding of the local to regional processes that govern the fire signal and contextualize current and past environmental changes.

How to cite: Haliuc, A., Daniau, A.-L., Mouillot, F., Chen, W., David, V., Hanquiez, V., Dennielou, B., Schefuß, E., Bayon, G., and Crosta, X.: Reconstructing fire regimes using micro-charcoal in modern marine sediments off Africa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11099, https://doi.org/10.5194/egusphere-egu22-11099, 2022.

EGU22-1217 | Presentations | BG1.2 | Highlight

Palaeofire: current status and future opportunities

Sandy Harrison, Daniel Gallagher, Paul Lincoln, Mengmeng Liu, Yicheng Shen, Luke Sweeney, and Roberto Villegas-Diaz

Sedimentary charcoal records are widely used to reconstruct regional changes in fire regimes through time in the geological past. The Reading Palaeofire Database (RPD) represents the most comprehensive compilation of sedimentary charcoal data currently available. It contains 1673 individual charcoal records from 1480 sites worldwide, with sufficient metadata to allow for the appropriate selection of sites to address specific questions. Most of the records have new age models, made by re-calibrating the radiocarbon ages using INTCAL2020 and Bayesian age-modelling software. In this talk we will show how these data are being used to document changing fire regimes during the Late Quaternary and to explore how fire regimes have responded to changes in climate, vegetation and human activities. We will demonstrate the progress that has been made to calibrate the charcoal records and make quantitative estimates of fire properties. We will also explore how these data can be used to evaluate and benchmark process-based fire-enabled models. Finally, we will highlight opportunities to use the palaeo-record together with models to explore fire regimes and their consequences for land-surface processes, biogeochemical cycles and climate.

How to cite: Harrison, S., Gallagher, D., Lincoln, P., Liu, M., Shen, Y., Sweeney, L., and Villegas-Diaz, R.: Palaeofire: current status and future opportunities, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1217, https://doi.org/10.5194/egusphere-egu22-1217, 2022.

EGU22-7457 | Presentations | BG1.2

Evaluation of simulations of the Last Glacial Maximum with fire-enabled vegetation models from the FireMIP intercomparison project 

Paul Lincoln, Sandy P. Harrison, Matthew Forrest, Jed Kaplan, and Chao Yue

Fire-enabled vegetation models are an important component of earth system modelling. Understanding the sensitivity of vegetation and wildfire to climate change benefits from out-of-sample experiments, of which the Last Glacial Maximum (LGM; 21 ka BP) is a preferred test. Here, we compared wildfire simulations for the LGM made with four fire-enabled vegetation models using a standardized protocol and driven by a climate-model simulation of the response to known LGM changes in ice-sheet extent, atmospheric composition and insolation. We compare the resulting model output with inferred changes in fire based on charcoal records from the Reading Palaeofire Database (RPD).

All four models show a global decrease in fire at the LGM compared to the present day, consistent with the charcoal records which also record less fire. The simulated change in fire is driven principally by changes in vegetation cover at the LGM, particularly the shift from forest to more open vegetation. The simulated reduction in forest cover is consistent with pollen-based reconstructions of LGM vegetation. Despite this general agreement among models, there are differences between the simulated fire anomalies at a regional scale. The largest differences between the models occur in equatorial Africa, South America and East Asia where the amplitude and spatial extent of regions of increased fire (driven principally by the replacement of tropical trees by grassland); in some regions even the direction of change is not consistent. Comparison of the simulated changes with charcoal records from these regions identifies which model(s) perform best, but also make it clear that there is no one model that simulates observed patterns of change in fire across all of the regions.

How to cite: Lincoln, P., Harrison, S. P., Forrest, M., Kaplan, J., and Yue, C.: Evaluation of simulations of the Last Glacial Maximum with fire-enabled vegetation models from the FireMIP intercomparison project , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7457, https://doi.org/10.5194/egusphere-egu22-7457, 2022.

EGU22-8737 | Presentations | BG1.2

Fire variability in the southeastern France over the past 8500 years

Marion Genet, Anne-Laure Daniau, Maria-Angela Bassetti, Bassem Jalali, Marie-Alexandrine Sicre, Julien Azuara, and Serge Berné

The Mediterranean region is strongly impacted by fires at present day. Projected warming scenarios suggest increase fire risk in the Mediterranean region (Pechony et Shindell, 2010). However, models based on modern-day statistical relationships do not consider interactions between climate, vegetation, and fire. In addition, process-based models must be tested not only against modern observations but also against climate observations different from today to cover the range of climate variability projected for the next centuries. Here, we present a new biomass burning record for the last 8,500 years in southeastern France with a mean temporal resolution of 45 years based on a marine sedimentary microcharcoal from the Gulf of Lion, located in the Rhone River prodelta. Periodicities of 500 and 1,100 years emerge from this record. Most of the peaks coincide with cold and dry periods of several century duration reflecting enhanced burning of open evergreen sclerophyllous Mediterranean forests. Among the 15 peaks of biomass burning, 7 are associated with negative North Atlantic Oscillation (NAO) phase, 8 with cold events, and 13 with low solar activity. We suggest that cold and wet conditions during negative NAO led to the accumulation of biomass while dry and cold winds during negative East Atlantic (EA) phase favored fuel flammability resulting in peaks in biomass burning. Today, large fires in southeastern France occur during negative NAO or during the Atlantic Ridge weather regime, the latter being similar to the EA (Ruffault et al. 2017). The frequency of heat-induced fire-weather favoring the largest wildfires observed in recent years in the Mediterranean region is projected to increase under global warming (Ruffault et al., 2020). Our study suggests also that the French Mediterranean region might be affected by large wind-driven fires developing in the event of negative NAO and EA modes.

 

References

Ruffault et al., 2017 Daily synoptic conditions associated with large fire occurrence in Mediterranean France: evidence for a wind-driven fire regime. https://doi.org/10.1007/s10584-012-0559-5

Ruffault et al., 2020. Increased likelihood of heat-induced large wildfires in the Mediterranean Basin. https://doi.org/10.1101/2020.01.09.896878

Pechony et Shindell, 2010. Driving forces of global wildfires over the past millennium and the forthcoming century. https://doi.org/10.1073/pnas.1003669107

How to cite: Genet, M., Daniau, A.-L., Bassetti, M.-A., Jalali, B., Sicre, M.-A., Azuara, J., and Berné, S.: Fire variability in the southeastern France over the past 8500 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8737, https://doi.org/10.5194/egusphere-egu22-8737, 2022.

EGU22-8312 | Presentations | BG1.2

Pyrogenic carbon in temperate forests - long-lasting impact of historical charcoal production on soils and ecosystems

Alexander Bonhage, Thomas Raab, Anna Schneider, Alexandra Raab, Shaghayegh Ramezany, and William Ouimet

Pre- and early industrial charcoal production has left a striking legacy effect on today’s soil landscapes in many forests of Central Europe and the North Eastern USA. Charcoaling in upright standing hearths (also called kilns) resulted in distinct circular micro relief structures, easily identifiable today in the field and on high resolution LiDAR-based digital elevation maps. Soils on these sites are characterized by one or multiple layers of decimetre thick charcoal rich substrate, which makes them Spolic Technosols according to the WRB soil classification. The focus of research on these sites increasingly deals with the difference of their soil physical and chemical properties in relation to unaffected forest soils and the potential implications for changes in vegetation and faunal growth. The controlling factor thereby is the soils large content of charcoal in various particle sizes, ranging from fine dust to large chunks. Studies have repeatedly shown the soils significant increase in total organic- and pyrogenic carbon content. The increase in total carbon stocks is thereby not only caused by pyrogenic carbon, but also by an apparently increased accumulation of non-pyrogenic organic matter. Here we present the latest findings regarding the carbon contents of centennially old charcoal rich technogenic substrates, sampled as part of multiple research projects in Brandenburg, Germany and the Litchfield hills in North-western Connecticut, USA. A focus will be the determination of highly aromatic carbon by the molecular marker Benzene-polycarboxylic acid (BPCA) and its prediction by FTIR-MIR chemometric methods. We discuss the results on forest soil carbon stocks on a site specific to a landscape and regional scale. Furthermore, the potential to use these sites to study the long term effects of charcoal admixture to soils by wildfires or biochar application will be discussed.  

How to cite: Bonhage, A., Raab, T., Schneider, A., Raab, A., Ramezany, S., and Ouimet, W.: Pyrogenic carbon in temperate forests - long-lasting impact of historical charcoal production on soils and ecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8312, https://doi.org/10.5194/egusphere-egu22-8312, 2022.

EGU22-1169 | Presentations | BG1.2

Recent and future intense fire seasons in the Mediterranean basin: the increasing role of droughts and heatwaves

Ricardo Trigo, Marco Turco, Sonia Jerez, Pedro Sousa, Ana Russo, and Julien Ruffault

Mediterranean ecosystems are prone to forest fires, as evidenced by several extreme fire seasons which struck in the last two decades, including both western (2003, 2005, 2017) and eastern (2007, 2018, 2021) Mediterranean sectors. These fire seasons had a massive impact on the economy and the environment, having also caused many human casualties, including 145 in Portugal 2017 and about 100 in Greece 2018. Moreover, it is now widely accepted that these outstanding fire seasons are often associated with unusually intense droughts and heatwaves (Turco et al., 2019; Ruffault et al, 2020). Additionally, there is strong evidence that the frequency of drought events in the Mediterranean basin has increased significantly in the last decades and is bound to increase further under different climate change scenarios (Tramblay et al., 2020).

The relentless tendency for increasing summer temperatures in Europe in recent decades, when compared to the last 500 hundred years, also underlines that the increment in temperatures is extensive to central and Scandinavian countries (Sousa et al., 2020), where forest fires have become considerably more frequent. Recent assessments have emphasised the synergy between drought and extremely hot summers in the Mediterranean (Russo et al., 2020).

In addition to this climate change scenarios point to a likely increase in the frequency of two specific heat-induced fire-weather types, precisely those that have been related to the largest wildfires observed in recent years (Ruffault et al., 2020). Heat-induced fire-weather types are characterized by compound dry and warm conditions occurring during summer heatwaves, either under moderate (heatwave type) or intense (hot drought type) drought. The frequency of heat-induced fire-weather is projected to increase by 14% by the end of the century (2071-2100) under the RCP4.5 scenario, and by 30% under the RCP8.5. In summary, these results consistently suggest that the frequency and extent of wildfires will increase throughout the Mediterranean Basin.

 

Ruffault J., Curt T., Moron V., Trigo R.M., Mouillot F., Koutsias N., Pimont F., Martin-StPaul N., Barbero R., Dupuy J.-L., Russo A., Belhadj-Khedher C., (2020) Scientific Reports, 10, 13790, doi: 10.1038/s41598-020-70069-z

Russo A., Gouveia C.M., Dutra E., Soares P.M.M., Trigo R.M.  (2019) Environmental Research Letters, 14(1), 014011, doi: 10.1088/1748-9326/aaf09e

Sousa P., Barriopedro D., García-Herrera R., Ordoñez C., Soares P.MM, Trigo R.M. (2020) Communications Earth & Environment, 1, 48, doi: 10.1038/s43247-020-00048-9

Turco M., Jerez S., Augusto S., Tarín-Carrasco P., Ratola N., Jimenez-Guerrero P., Trigo, R.M. (2019) Scientific Reports, 9, 1, doi: 10.1038/s41598-019-50281-2

 

This work was supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project FIRECAST (PCIF/GRF/0204/2017). M.T. is supported by the Spanish Ministry of Science, Innovation and Universities - Spanish State Research Agency and the European Regional Development Fund through the PREDFIRE projects (RTI2018-099711-J-I00, MCI/AEI/FEDER, EU) and the Ramón y Cajal grant (RYC2019-027115-I). S.J. thanks the Spanish Ministry of Science, Innovation and Universities - Agencia Estatal de Investigación and the European Regional Development Fund for the support received through the EASE project (RTI2018 100870 A I00).

How to cite: Trigo, R., Turco, M., Jerez, S., Sousa, P., Russo, A., and Ruffault, J.: Recent and future intense fire seasons in the Mediterranean basin: the increasing role of droughts and heatwaves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1169, https://doi.org/10.5194/egusphere-egu22-1169, 2022.

EGU22-11616 | Presentations | BG1.2

Fire weather risk analysis over Portugal in the last decades and their impacts over the atmosphere  - The Monchique study case

Filippe LM Santos, Flavio T Couto, Vanda Salgueiro, Miguel Potes, Maria João Costa, Daniele Bortoli, and Rui Salgado

More intense fire seasons have been favoured by climate changes worldwide, like Russia, Brazil, the USA, Canada and Portugal. Portugal experienced numerous severe fire seasons with catastrophic wildfires that caused enormous impacts in the last years. This study aimed to investigate the fire risk evolution in Portugal over the last 40 years and the extreme wildfire emission impacts derived from remote sensing data. First, the Fire Weather Index (FWI) from 1979 to 2020, at 0.25º spatial resolution, provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis version 4 based on meteorological variables, was used. Then, FWI monthly mean values and trends were analysed for four districts of Southern Portugal (Beja, Evora, Faro and Portalegre). The results indicate that the Faro district presented extreme fire risk values, which peaked on August 2, 2018, one day before the Monchique (a mountain in Faro) wildfire began and lasted between August 3 and 10. The Monchique wildfire was the most destructive in Portugal during 2018, with almost 27.000 ha burned. Second, based on the previous results, atmospheric products derived from the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Sentinel-5 Precursor satellite, the first Copernicus mission dedicated to atmospheric composition monitoring, were collected. These datasets were obtained from Google Earth Engine (GEE), the online platform that combines multiple imageries and datasets with cloud processing to perform analyses. The Carbon monoxide (CO) and Nitrogen dioxide (NO2) concentrations, as well as Absorbing Aerosol Index (AAI) products were analysed during the fire event. The concentrations released by the wildfire reached values 3 and 5 times higher than usual for CO and NO2, respectively. Therefore, the work confirms that extreme wildfire events can release huge pollutant concentrations into the atmosphere. Also, the Sentinel-5 products are useful to evaluate the fire emission evolution in extreme wildfires events and may constitute additional valuable information to combine with ground-based information to map air quality related to wildfire occurrences.

This research was funded by the European Union through the European Regional Development Fund in the framework of the Interreg V A Spain - Portugal program (POCTEP) through the CILIFO project (Ref.: 0753-CILIFO-5-E), FIREPOCTEP project (0756-FIREPOCTEP-6-E), and also by national funds through FCT - Foundation for Science and Technology, I.P. under the PyroC.pt project (Refs. PCIF/MPG/0175/2019), ICT project (Refs. UIDB/04683/2020 and UIDP/04683/2020), and TOMAQAPA (PTDC/CTAMET/ 29678/2017).

How to cite: Santos, F. L., Couto, F. T., Salgueiro, V., Potes, M., Costa, M. J., Bortoli, D., and Salgado, R.: Fire weather risk analysis over Portugal in the last decades and their impacts over the atmosphere  - The Monchique study case, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11616, https://doi.org/10.5194/egusphere-egu22-11616, 2022.

EGU22-12015 | Presentations | BG1.2 | Highlight

Evidence for a stronger global impact of fire on atmospheric composition

James Randerson, Yang Chen, Li Xu, Joanne Hall, Louis Giglio, Dave van Wees, Sander Veraverbeke, Guido van der Werf, Douglas Morton, Elizabeth Wiggins, Niels Andela, and Stijn Hantson

Toward the development of the 5th generation of the Global Fire Emission Database (GFED5), we provide evidence for a significantly higher level of contemporary global fire emissions than what has been reported in previous inventories, as a result of advances in our understanding of burned area, fuel consumption, and emission factors. Increases in the availability of high-resolution burned area datasets from Sentinel and Landsat now allow for more effective estimation of fire scars associated with small and discontinuous fires in many biomes. By combining these regional-scale datasets with burned area and active fire observations from MODIS, we estimate that global burned area exceeded 700 Mha per year during 2001-2020. This estimate is more than 40% higher than previous estimates from GFED4 with small fires (GFED4s), mostly as a consequence of increases in savanna and grassland burning across Africa, South America, and Southeast Asia. At the same time, more extensive field observations in boreal forest ecosystems provide evidence for higher levels of fuel consumption than has been integrated into previous regional and global inventories. New emission factor observations from tropical peatlands and boreal forests provide evidence for a stronger smoldering phase of emissions, elevating emissions of carbon monoxide and organic carbon aerosol. Together, these advances suggest the impact of contemporary wildfires may have been underestimated in past work; we conclude by exploring the compatibility of this inventory with atmospheric aerosol and trace gas observations using a global atmospheric chemistry model.

How to cite: Randerson, J., Chen, Y., Xu, L., Hall, J., Giglio, L., van Wees, D., Veraverbeke, S., van der Werf, G., Morton, D., Wiggins, E., Andela, N., and Hantson, S.: Evidence for a stronger global impact of fire on atmospheric composition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12015, https://doi.org/10.5194/egusphere-egu22-12015, 2022.

EGU22-2611 | Presentations | BG1.2 | Highlight

Present and future tropical fire risks associated with compound events

Andreia F. S. Ribeiro, Paulo M. Brando, Lucas Santos, Ludmila Rattis, Martin Hirschi, Mathias Hauser, Sonia I. Seneviratne, and Jakob Zscheischler

Complex interactions between climate and land-use are altering the course of the fire regimes across the tropics. In Brazil, many recent peaks of burned area have co-occurred with extreme climate events, high deforestation rates and agricultural expansion. Particularly during compound dry and hot years, widespread fires have become increasingly common, and an intensification of the fire activity due to climate change may be already underway.

Based on a compound-event-oriented framework to assess fire risk, we provide evidence on the extent to which fire activity and the associated impacts could be constrained if anthropogenic global warming is limited. Here we quantify the nonlinear relationships between compound climate drivers and burned area across two main Brazilian biocultural heritage sites (Xingu and Pantanal) and estimate compound-event-related fire risks in terms of the occurrences of compound drivers beyond which the fire response becomes extreme.

Our results show that the exponential response of burned area to climate is well explained by compound events characterized by air dryness and precipitation deficits (high VPD and low precipitation) and that climate-change induced fire risks will increase due to the co-occurrence of drier and warmer climatic conditions under global warming. However, if global warming is constrained to +1.5°C instead of +3°C, the likelihood of fire risk can be reduced by ~11% in the case of the most prominent fire types (forest fires in Xingu and grassland fires in the Pantanal). We thus conclude that if we slow down the rate of warming and follow more sustainable uses of land, we might be able to prevent the crossing of tipping points and the consequent downward spiral of socio-environmental impacts that threatens these regions.

How to cite: Ribeiro, A. F. S., Brando, P. M., Santos, L., Rattis, L., Hirschi, M., Hauser, M., Seneviratne, S. I., and Zscheischler, J.: Present and future tropical fire risks associated with compound events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2611, https://doi.org/10.5194/egusphere-egu22-2611, 2022.

EGU22-10524 | Presentations | BG1.2 | Highlight

Observing the climate impact of large wildfires on stratospheric temperature

Matthias Stocker, Florian Ladstädter, and Andrea K. Steiner

In the future, large wildfires are expected to become more frequent and intense. Not only do they pose a serious threat to people and ecosystems, but they also affect the Earth's atmosphere. Aerosols from large wildfires can even reach the stratosphere where they can linger for months to years. However, little is known about their impact on climate. In particular, the potential of large wildfires to cause temperature changes in the stratosphere has hardly been studied.

In our study, we analyze two extreme wildfire events, those in 2017 in North America and those in 2019/20 in Australia, using new satellite observational data. We find strong effects of the fires on the atmospheric temperature structure and short-term climate in the stratosphere. The results show significant warming of the lower stratosphere by up to 10 K within the aerosol clouds emitted by the wildfires immediately after their formation. The climate signal in the lower stratosphere persists for several months, reaching 1 K for the 2017 North American wildfires and a remarkable 3.5 K for the 2019/20 Australian wildfires. This is stronger than any signal from volcanic eruptions in the past two decades. Such extreme events potentially influence the atmospheric composition and stratospheric temperature trends, underscoring their importance for future climate.

Improved knowledge of the temperature signals from extreme wildfires is particularly important for trend analysis. Our ongoing research on this topic aims to further improve the separation of natural variability from anthropogenic influences in climate trend detection, especially in the stratosphere.

How to cite: Stocker, M., Ladstädter, F., and Steiner, A. K.: Observing the climate impact of large wildfires on stratospheric temperature, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10524, https://doi.org/10.5194/egusphere-egu22-10524, 2022.

EGU22-10391 | Presentations | BG1.2

Impacts of Fires on Convective Cloud Features in Southeast Asia: Variability with ENSO

Azusa Takeishi and Chien Wang

Located right in the middle of the tropical warm pool, convective activities over Southeast Asia are subject to interannual variability in sea surface temperature due primarily to varying phases of the El Niño-Southern Oscillation (ENSO). Observations often show a reduction in the amount of rainfall during El Niño and its increase during La Niña over Southeast Asia. Because of this interannual variability in rainfall and humidity, emissions of aerosol particles and their abundance in the atmosphere, often manifested in aerosol optical depths, are also subject to interannual variability; they increase during El Niño and are reduced during La Niña on average. Our previous study has shown an impact of biomass-burning aerosols on convective clouds, which enhanced rainfall and generally invigorated convection. Here we present the comparison of this aerosol effect among different years with different ENSO phases. We utilized month-long cloud-resolving simulations by the WRF-CHEM model that are capable of including both aerosol direct and indirect effects. The extensive simulation domain size and time period enabled the inclusion of a wide range of contributors to cloud development over the area, from aerosol activation to ENSO-affected meteorology. We show whether the invigoration effect that we found from the year of strong El Niño in 2015 still holds in years of weaker El Niño or even during La Niña.

How to cite: Takeishi, A. and Wang, C.: Impacts of Fires on Convective Cloud Features in Southeast Asia: Variability with ENSO, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10391, https://doi.org/10.5194/egusphere-egu22-10391, 2022.

EGU22-7318 | Presentations | BG1.2

Evaluating the effects of fire severity and post-fire management decisions on the carbon balance of a Swedish forest

Julia Kelly, Stefan H. Doerr, Johan Ekroos, Theresa S. Ibáñez, Cristina Santín, Margarida Soares, and Natascha Kljun

Boreal forest fires are increasing in frequency and intensity due to climate change. Yet there is little knowledge on the impacts of fire severity and post-fire management decisions on the regeneration and carbon balance of production forests in Eurasia. To investigate these issues, we established 6 sites in a Swedish Pinus sylvestris forest that burned in 2018. Specifically, we evaluated the effects of (i) fire severity (low severity ground fire vs high severity stand-replacing canopy fire), (ii) post-fire wood management (salvage-logged vs unlogged) and (iii) post-fire vegetation management (natural regeneration, seeding or planting nursery seedlings of P. sylvestris). At each site, we measured soil respiration (CO2 release to the atmosphere) and methane fluxes (soil CH4 uptake) using the manual chamber approach, soil microclimate and vegetation cover for the first 3 years after the fire (2019-2021). Two of the sites also have eddy covariance flux measurements, which provided an insight into the ecosystem-scale carbon balance.

 

Fire severity had a strong impact on forest soils, with high fire severity sites having lower soil respiration, warmer soils and less vegetation regrowth compared to a low fire severity site. Surprisingly, soil respiration was similar at a low fire severity site and unburnt site, despite the almost complete loss of the soil organic layer during the ground fire. There were no clear effects of fire or post-fire management on the soil methane fluxes. Salvage-logging of a high fire severity site had no additional effects on soil respiration compared to leaving the dead trees standing. Salvage-logging of a low fire severity site led to a decline in soil respiration, but turned the ecosystem into a net source of CO2 due to the removal of the living trees. In terms of P. sylvestris regeneration, our results showed that the seedling density following natural regeneration was similar to or higher than the seedling density in sites which had been manually seeded or replanted with nursery seedlings.

 

Our results suggest that post-fire management interventions may not facilitate faster vegetation regrowth and the recovery of carbon uptake by forests compared to natural regeneration in the immediate post-fire years. Furthermore, despite the start of new vegetation growth and declines in soil CO2 release, the high fire severity and/or salvage-logged sites remain net CO2 sources 3 years after the fire, which must be considered in estimations of the net effect of fires on Sweden’s forest carbon balance.

How to cite: Kelly, J., Doerr, S. H., Ekroos, J., Ibáñez, T. S., Santín, C., Soares, M., and Kljun, N.: Evaluating the effects of fire severity and post-fire management decisions on the carbon balance of a Swedish forest, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7318, https://doi.org/10.5194/egusphere-egu22-7318, 2022.

EGU22-3357 | Presentations | BG1.2

High concentrations of environmentally persistent free radicals in fire derived pyrogenic organic matter

Gabriel Sigmund, Cristina Santin Nuno, Marc Pignitter, Nathalie Tepe, Stefan Helmut Doerr, and Thilo Hofmann

Fire derived pyrogenic organic matter / charcoal is a source of environmentally persistent free radicals, which are precursors of potentially harmful reactive oxygen species. We analyzed charcoal samples from ten wildfires, including crown as well as surface fires in boreal, temperate, subtropical and tropical climate regions. Concentrations of environmentally persistent free radicals in these samples were orders of magnitude higher than those found in soils or other “background” matrices, as measured via electron spin resonance spectroscopy. The highest concentrations were measured in woody charcoals that were highly carbonized. We also found that environmentally persistent free radicals remained unexpectedly stable in the field for at least 5 years.

More details can be found in our recently published article: https://www.nature.com/articles/s43247-021-00138-2

How to cite: Sigmund, G., Santin Nuno, C., Pignitter, M., Tepe, N., Doerr, S. H., and Hofmann, T.: High concentrations of environmentally persistent free radicals in fire derived pyrogenic organic matter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3357, https://doi.org/10.5194/egusphere-egu22-3357, 2022.

EGU22-1007 | Presentations | BG1.2

Investigating woody species resprouting in response to fire

Yicheng Shen, Colin Prentice, and Sandy Harrison

Fire is a major disturbance in natural ecosystems and more extreme fires are predicted to occur in the future. Plant species can survive or resist wildfires and adapt to fire-prone regimes by exhibiting fire-related plant traits such as serotiny and heat-simulated germination. Resprouting is one of the most common plant traits that confer resilience to fire, promoting rapid post-fire recovery and affecting ecosystem dynamics. We investigated the relationships between the abundance of resprouting woody species, fire return interval and fire intensity in three regions: Europe, Australia and South and Central America. Species abundance data were obtained from the SplotOpen database while resprouting information are derived from regional and global databases, field information and the literature. Fire return time and fire intensity at each site were estimated using remotely sensed observations (MODIS MCD64CMQ, MODIS MCD14ML and Fire Atlas). We show that the abundance of resprouting woody species decreases with increasing fire return interval but that resprouters are most abundant at intermediate levels of fire intensity. These patterns are seen in all the three regions. Given that the abundance of resprouting woody species is strongly related to the fire regime, it should be possible to model their distribution in an optimality framework. Since the abundance of resprouters will affect ecosystem post-fire recovery, it is important to include this trait in fire-enabled vegetation models in order to simulate ecosystem dynamics adequately.

How to cite: Shen, Y., Prentice, C., and Harrison, S.: Investigating woody species resprouting in response to fire, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1007, https://doi.org/10.5194/egusphere-egu22-1007, 2022.

EGU22-1372 | Presentations | BG1.2

Pyrogenic carbon decomposition critical to resolving fire's role in the Earth system

Simon P.K. Bowring, Matthew W. Jones, Philippe Ciais, Bertrand Guenet, and Samuel Abiven

Recently identified post-fire carbon fluxes indicate that in order to understand if global fires represent a net carbon source or sink, one must consider both terrestrial carbon retention through pyrogenic carbon (PyC) production, and carbon losses via multiple pathways. Here, these legacy source and sink pathways are quantified using a CMIP6 land surface model to estimate Earth's fire carbon budget. Over 1901-2010, global PyC drives annual soil carbon accumulation of 337 TgCyr-1, offset by legacy carbon losses totalling -248 TgCyr-1. The residual of these values constrains maximum annual pyrogenic carbon mineralisation to 89 TgCyr-1, and PyC mean residence time to 5387 years, assuming steady state.   However, paucity of observational constraints for representing PyC mineralisation mean that without assuming steady state, we are unable to determine the sign of the overall fire carbon balance. 

The residual is negative over forests and positive over grassland-savannahs (implying a potential sink), suggesting contrasting roles of vegetation in the fire carbon cycle. Without widespread tropical grassland-savannah coverage, the legacy effects of fires could not feasibly enhance terrestrial C storage -a result afforded by grasses’ capacity for fire recovery. The dependency of the fire C residual on vegetation composition suggests that the preservation/restoration of native grasslands may be an important vector for decreasing C losses from future fire activity. We call for significant investments in understanding of PyC degradation and its drivers, in addition to improved estimates of legacy fire C fluxes. Reliable quantification of PyC mineralisation and erosion, particularly over grasslands, remains the principal missing link in a holistic understanding of fire’s role in the Earth system.

How to cite: Bowring, S. P. K., Jones, M. W., Ciais, P., Guenet, B., and Abiven, S.: Pyrogenic carbon decomposition critical to resolving fire's role in the Earth system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1372, https://doi.org/10.5194/egusphere-egu22-1372, 2022.

Climate change has several impacts on our Earth. Even though wildfires are natural processes to sustain structure of an ecosystem, there is a significant increase in the global fire cases and their extent in the recent years caused by the climate change. These wildfires have important impacts on air quality, climate and relatedly public health. Copernicus Atmospheric Monitoring Service (CAMS) indicated that Siberia, North America, and the Mediterranean regions are greatly impacted by wildfires and the intensities of these fires are expressed as Fire Radiative Power (FRP). Effect of wildfires can also be observed with gas pollutant satellite retrievals of CO, NO2, and HCHO which is an important volatile organic carbon (VOC).

Turkey was challenged with wildfires that result in the destruction of forests, the death of animals and devastating impacts on local people in 2021. CAMS Global Fire Assimilation System (GFAS) indicated that the worst fire case observed in Turkey compared with other Mediterranean countries. Global Forest Watch fire counts showed that, fire counts reached up to 695 and 385 in summer (between June-August) 2021 for Antalya and Mugla provinces, respectively. However, fire counts did not exceed 165 fires in the summer season for either Antalya or Mugla in the last five years. Moreover, there was a significant increase in fires in the forested lands for Mersin province as well. Fire counts reached up to 171 per day (31st August) in Antalya province and fire smokes were observable from MODIS Corrected Reflectance images in the fire period. In addition, air pollutants caused by these fires were observable with high resolution TROPOMI retrievals.

In this study, multi-pollutant satellite retrievals were used to investigate the wildfires air quality impacts on the Southwestern Turkey. VIIRS S-NPP Fire Radiative Power product and TROPOMI CO, NO2, and HCHO, products were used to analyze impacts of these extreme wildfire cases. Products were processed spatially and temporally for two months (July-August 2021). A specific attention was given on period of 28th July-12th August. A 1×1 km2 gridded domain covering the impacted region was selected to investigate the spatial distribution of these pollutants. 29th and 31st of July were the days where the impacts of wildfires were analyzed specifically. Wind speed and direction were used to understand the relation between meteorological conditions and the pollution distribution caused by the wildfires. Aerosol signals will be also investigated using MODIS aerosol optical depth (AOD) and TROPOMI aerosol index (AI) retrievals.

How to cite: Eke, M., Cingiroglu, F., and Kaynak, B.: Impacts of summer 2021 wildfire events in Southwestern Turkey on air quality with multi-pollutant satellite retrievals, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12134, https://doi.org/10.5194/egusphere-egu22-12134, 2022.

EGU22-12301 | Presentations | BG1.2

Spatiotemporal post-fire change analysis using optical and SAR imagery

Yeji Lee, Junse Oh, Su Young Kim, Yoon Taek Jung, and Sang-Eun Park

Wildfires on permafrost covered with the boreal forest can influence vegetation composition, surface soil moisture, and the active layer. Since wildfires on permafrost occur extensively in unpredictable areas, remote sensing is a useful tool for monitoring burn severity and ecosystem changes. Optical spectral indices such as the differenced normalized burn ratio (dNBR) and normalized difference vegetation index (NDVI) were traditionally used to detect burn severity and vegetation regrowth. However, since optical imagery is significantly affected by cloud cover and weather conditions, there is a limitation in acquiring temporally dense images. Synthetic Aperture Radar (SAR) can obtain images regardless of day/night or weather conditions, so it is possible to densely observe the area of interest spatiotemporally. In addition, SAR images, unlike optical images, can acquire information on the active layer of the permafrost in the winter season. This study aimed to analyze winter season time-series SAR backscattering coefficient change with burn severity in south Northwest Territories, Canada using optical and SAR data. The study area, south Northwest Territories, belongs to the discontinuous permafrost zone and consisted of the taiga. Burn severity and vegetation regrowth were estimated by dNBR and NDVI using optical imagery. To increase the temporal resolution, Landsat-8 OLI and Sentinel-2 MSI were acquired through the cloud-based Google Earth Engine (GEE) in the summer season. C-band dual-polarization Sentinel-1 and X-band single-polarization TerraSAR-X were obtained to understand the multi-frequency backscattering coefficient to fire-induced changes. The changes pattern of the SAR backscattering coefficient varies according to the burn severity, especially in the winter season, not affected by vegetation and soil moisture. It can be seen that the wildfires affected the changes in the scattering mechanism in permafrost on the boreal forests. These results represent that C-band and X-band SAR images have the potential to monitor the changes of the active layer with burn severity.

How to cite: Lee, Y., Oh, J., Kim, S. Y., Jung, Y. T., and Park, S.-E.: Spatiotemporal post-fire change analysis using optical and SAR imagery, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12301, https://doi.org/10.5194/egusphere-egu22-12301, 2022.

EGU22-2463 | Presentations | BG1.2

Role of human impact on fire history and vegetation succession in one of the oldest protected forests in Europe

Niina Kuosmanen, Tuomas Aakala, and Heikki Seppä

Fire is naturally an integral part of the northern boreal forests dynamics. However, anthropogenic activity has greatly affected the fire history in Fennoscandia, especially during the last millennia and the effective fire suppression practically led to the absence of a natural fire regime in boreal forests in Finland. However, the changing climate conditions may increase the risk of severe fire events regardless of the fire management. Therefore, it is important to look into the long-term interactions between human impact, fire and vegetation succession in order to understand the possible future role of fire in boreal forests.

One of the oldest protected areas in Europe is located in Central Finland and provides a good opportunity to investigate the change from natural fire and vegetation dynamics to human controlled fire regime and the natural vegetation succession after cessation of the slash-and-burn cultivation. The site is known to have been under slash-and-burn cultivation until the beginning of the 19th century and the last known burnings were done in the 1840s after which the site has been left to natural succession. The site was partly protected in 1911 and it was included into national the old-growth forest reserve protection program in 1994.

In order to investigate the long-term natural fire history and the role of human impact in the fire and the vegetation dynamics during last 3000 years we collected peat cores covering from two small forest hollows from the Kuusmäki old-growth forests protected area. Macroscopic (> 150 µm) charcoal and Neurospora-fungal spores are used to reconstruct the fire history and pollen analysis is performed to reconstruct the long-term vegetation dynamics in the study area.

The preliminary results demonstrate an increase in charcoal abundance from 16th century suggesting increased fire activity and a more intensive period of slash and burn cultivation in the area until the beginning of the 19th century. The absence of charcoal during the last century suggests absence of fire after the cessation of slash and burn cultivation. These results together with the vegetation succession will be further discussed in the presentation.

How to cite: Kuosmanen, N., Aakala, T., and Seppä, H.: Role of human impact on fire history and vegetation succession in one of the oldest protected forests in Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2463, https://doi.org/10.5194/egusphere-egu22-2463, 2022.

EGU22-3871 | Presentations | BG1.2

Projected changes in variability of fire weather in boreal regions under different levels of global warming

Marianne T. Lund, Kalle Nordling, Astrid B. Gjelsvik, and Bjørn H. Samset

Recent years have seen unprecedented fire activity at Arctic latitudes, leading to severe consequences including unhealthy air quality in high latitude towns and cities. While wildfire occurrence and severity result from a complex interplay between natural and anthropogenic factors, weather is a key factor.

Weather conditions that promote high wildfire risk are characterized by the combination of high temperatures, little precipitation and low humidity, and often high winds. All of these can be affected by human-induced climate change and evidence is emerging that wildfire risk is already increasing in many regions. Such changes not only manifest as shifts in the means and extremes of the weather variables but can also be changes in the shape of their distributions. The importance of the full, regional Probability Density Functions (PDFs) of individual and aggregated variables, which contain information on expected weather not apparent from the distribution mean or tails, but through changes to their overall shape, for understanding climate risk has been broadly discussed in the literature. Furthermore, while simulations with regional climate models to derive such information are costly and time consuming, the advent of large ensembles of coupled climate model simulations has recently opened new opportunities.

Here we present a detailed characterization of the distribution and variability of weather variables conducive to wildfire risk across five high-latitude boreal regions in North America, Scandinavia and Russia. Building on methodology developed in Samset et al. (2019), we quantify the PDFs of daily data for a broad set of individual variables, as well as for the aggregate change expressed using the Canadian Fire Weather Index. Using ensembles of coupled simulations from two climate models (CanESM5 and MPI-ESM1-2) and two CMIP6 scenarios (the Shared Socioeconomic Pathways SSP1-2.6 and SSP5-8.5), we consistently quantify the changes of regionally and seasonally resolved PDFs under different levels of global warming.  

Our results provide a comprehensive picture of the potential future changes in drivers of fire weather and wildfire risk in the pan-Arctic region and demonstrate the difference between regions. We also show how statistical descriptions combined with emulation of Earth System Model (ESM) information can offer an alternative pathway to resource demanding model runs, for rapidly translating science to user-oriented information.

How to cite: Lund, M. T., Nordling, K., Gjelsvik, A. B., and Samset, B. H.: Projected changes in variability of fire weather in boreal regions under different levels of global warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3871, https://doi.org/10.5194/egusphere-egu22-3871, 2022.

Unprecedented wildfires swept Mediterranean Europe in the summer of 2021 wreaking havoc economically and socially while clearing large swaths of forest land. Those that scorched the southern coastal highlands in Turkey came on the heels of a heat wave and at the peak of the arid season. Nearly two thirds of the Anatolian Peninsula are under the influence of Mediterranean-type climate and prone to seasonal wildfires, a quality that also encourages high species diversity. The region’s heterogenous topography is home to different meso- and micro-climates which in turn translate into high rates of endemism. Although fire as disturbance is essential for the regeneration of Mediterranean-type ecosystems, potential changes in fire frequency and severity, coupled with longer periods of drought expectations - mainly as a result of anthropogenic deforestation and climate change - is duly raising concerns. The expected increase in the frequency and intensity of climate-based disturbances necessitates some form of a predictive mechanism for future protection and mitigation, especially for these otherwise fire-adapted ecosystems. Dynamic Global Vegetation Models (DGVMs) with built in disturbance schemes when forced with future projections of climate models can be powerful tools in this regard.

In this study, we present our preliminary findings from six different model simulations, run with LPJ-GUESS, a process based DGVM. We initially introduced three native conifer species with different fire histories and significant distributions in the Anatolian Peninsula to the model and forced it with climatic drivers from ERA5 Land reanalysis dataset for the historical period. Once confident that our simulation results closely reflected the historical fires in the remote sensing datasets available through Google Earth Engine, we continued to force the model with climatic drivers from different model contributions to CMIP6, bias-corrected, interpolated to the 9-km horizontal resolution of ERA5 Land reanalysis and reflecting the RCP 8.5 scenario. All simulation results were analyzed using Climate Data Operators (CDO), ArcGIS, and R computing language.

Our preliminary results indicate an overall increase in pyro-diversity for the country across all simulations. A potential expansion of wildfire range towards the northwest was also observed, a curious outcome as this region includes the western Black Sea mountain ranges that are known for high precipitation rates. These mountains are also home to a rich forest cover with a fine mixture of broadleaved and conifer species spreading horizontally along different altitudinal belts. In light of our preliminary findings and along with our continuing research on the effects of any potential future climate-change related shifts in the fire regime on forest composition, we urge additional study of different landscape scale disturbances (i.e. soil erosion and landslides) which may potentially be triggered as a result of a diversifying and intensifying fire regime and which may have a significant impact for the terrestrial ecosystems and livelihood. 

This study benefited from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) grant 118C329. The financial support received from TUBITAK doesn’t mean that the content of the publication is scientifically approved by TUBITAK.

How to cite: Ekberzade, B., Yetemen, O., and Sen, O. L.: Looking into a fuzzy future: coupled effect of pyrogeography and a changing climate on an already fragile terrestrial ecosystem , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-239, https://doi.org/10.5194/egusphere-egu22-239, 2022.

EGU22-11760 | Presentations | BG1.2

Climatic drivers explain the interannual variability of the global burned area

Andrina Gincheva, Sonia Jerez, Juli G. Pausas, Joaquín Bedía, Sergio M Vicente-Serrano, Antonello Provenzale, Emilio Chuvieco, John Abatzoglou, and Marco Turco

Understanding the response of fire to climate variations is essential to adapt fire management systems under climate change. Although several studies have analysed the drivers of the average spatial variability of fire, the assessment of the temporal variability of fire in response to climate across the globe has proved challenging, largely due to complexity of the processes involved, the limitation of observation data and the compound effect of the multiple drivers, which usually cause non-linear effects.

In this study, we analyse how much of the interannual variability in observed burned area (BA) is linked with temporal variations in climate at global scale. To solve this question, we use the burned area data of the FireCCI51. product for the period 2001-2019 at the global scale, and different climate metrics that are directly related to drought occurrence, including indices like the Fire Weather Index (FWI), the Standardized Precipitation Evapotranspiration Index (SPEI), and the Standardized Precipitation Index (SPI). Our study shows complex spatial patterns in the relationship between climate drivers and BA variability, highlighting where variations in FWI, SPI, SPEI or their interaction explain BA variability. While in some areas the interannual variability of burned area does not show a statistically significant influence of climate variability, over a substantial portion of the global burnable area (~60%) the BA variability can be explained by interannual variability of climate drivers. Globally, climate variability accounts for roughly two thirds (64%) of the observed temporal BA variability.

How to cite: Gincheva, A., Jerez, S., Pausas, J. G., Bedía, J., Vicente-Serrano, S. M., Provenzale, A., Chuvieco, E., Abatzoglou, J., and Turco, M.: Climatic drivers explain the interannual variability of the global burned area, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11760, https://doi.org/10.5194/egusphere-egu22-11760, 2022.

EGU22-11856 | Presentations | BG1.2

Analysis of the environmental conditions favoring the development of deep pyroconvection in Southern Europe 

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

Deep pyroconvection can strongly modify surface weather conditions, especially when a firestorm develops, completely altering fire spread and making it more difficult to predict and control. However, the limited number of observations constrains our understanding of this type of events, so the environmental controls on deep pyroconvection are not entirely clear and, in particular, there are still uncertainties about the atmospheric conditions conducive to the development of this phenomenon. We conduct idealised numerical simulations with the fire-atmosphere coupled model WRF-Fire initialised with selected real-case atmospheric profiles of wind, temperature and moisture, obtained from the ERA5 database, corresponding to the 100 days of highest fire risk per year during the 2010-2019 period at six different European fire-prone locations. For each of these atmospheric profiles, we perform a suite of paired experiments of an ideal fire spreading through five different fuel categories. Each pair consists of a control run with interaction between fire and atmosphere and a simulation in which the sensible and latent heat fluxes from the fire are turned off (uncoupled simulation). This experiment allows us to make a significant statistical study of pyroconvection events and thus analyse which environmental factors favour its development. We found that a high fuel load, a large vertical temperature lapse rate between the 850 hPa and the 500 hPa levels and a high moisture content in the lower layers of the atmosphere are some of the main factors in the development of firestorms. 

How to cite: Senande-Rivera, M., Insua-Costa, D., and Míguez-Macho, G.: Analysis of the environmental conditions favoring the development of deep pyroconvection in Southern Europe , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11856, https://doi.org/10.5194/egusphere-egu22-11856, 2022.

EGU22-384 | Presentations | BG1.2

Pantanal’s 2020 fire season in perspective: the case of a natural heritage reserve

Patrícia S. Silva, Joana Nogueira, and Renata Libonati

Pantanal saw a catastrophic fire season in 2020, with a quarter of the biome hit by flames (around 4 million ha). Protected and indigenous areas burnt entirely, and it is estimated that at least 17 million vertebrates died, including several endangered species endemic to the biome. These dramatic events drew attention to the occurrence and aftermath of fire within a fire-sensitive ecosystem such as Pantanal’s wetlands.

The RPPN (Reserva Particular do Patrimônio Natural) SESC Pantanal was one of such protected areas severely affected in 2020, with around 2/3 of its territory burnt. Here, we analyse the historical fire behaviour within the RPPN, including the 2020 events, using remote sensing products over the 2001-2020 period. 

Although fire has historically occurred within the RPPN at an average of 2 400 ha burned per year, the 2020 fire events were an absolute outlier with more than 70 600 ha burned. Before 2020, only 2010 reached above 10 000 ha of burned areas, and the most extreme events were found to be those above 3 000 ha. When considering the 2001-2019 period, wetlands and grasslands are the land cover types that burn the most (52 and 17% of the total burned area, respectively), followed by forests and savanna formations (16 and 9%, respectively). The year of 2020, however, changed this pattern: most burned areas occurred in forested areas (40%), followed by grasslands (26%) and savanna formations (24%). We also found that fire is not recurrent: during the 19 years of historical data the vast majority of burned areas occurred only once (60%), 35% burned up twice or thrice, and solely 5% burned more than 3 times.

Future climate change assessments seem to point at a warmer and drier future for the biome, when events such as 2020 might become more regular. Our results provide an historical characterization leading up to the 2020 fires within the RPPN SESC Pantanal, that may be of use for fire managers in light of future climate change. 

How to cite: Silva, P. S., Nogueira, J., and Libonati, R.: Pantanal’s 2020 fire season in perspective: the case of a natural heritage reserve, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-384, https://doi.org/10.5194/egusphere-egu22-384, 2022.

Biochar has become an accepted soil amendment due to its potential to improve soil properties and as a tool to increase carbon sequestration. The latter is based on its relatively high biochemical recalcitrance augmenting the slow C pool after its addition to soils. However, newer studies indicated that the longevity of biochar and naturally produced pyrogenic organic matter (PyOM) in soils is lower than commonly assumed. Many of those studies are based on the determination of CO2 production changes or on the recovery of their isotopic labels in the soil after amendment of biochar or PyC incorporation. Most probably because of the lack of appropriate techniques to differentiate between the natural soil organic matter fraction and the added black carbon, only few reports are available which relate turn-over data with chemical alterations of biochar during aging or the impact of the latter on the quality of the total SOM pool.  In order to fill this gap, we applied virtual fractionation of SOM into different organic matter pools by different solid-state NMR techniques. Whereas the most common combines the determination of turnover rates via stable isotope techniques, an alternative approach takes advantage of different relaxation behavior of biochar and humified SOM. In both cases spectra can be calculated that show either the added biochar or the respective SOM.  In the frame of the present work, the concept and the potential of the two approaches will be explained by using examples studied in our laboratory.  With this, we intend to provide a further powerful tool which can lead to a better understanding of the biochemistry related to the transformation of PyC and biochar during aging and their subsequent integration into the soil organic matter fraction.

 

Acknowledgement: Financial support has been provided by the European Institute of Innovation and Technology (EIT), a body of the European Union, under Horizon2020, the EU Framework Programme for Research and Innovation (Project 21217 Black to the future - biochar and compost as soil amendment)

How to cite: Knicker, H., Knicker, M., García de Castro Barragán, J. M., and Velasco-Molina, M.: NMR-spectroscopic virtual fractionation of soils mixed with pyrogenic carbon as a tool to separate chemical processes related to aging of pyrogenic carbon from those occurring during humification of soil organic matter , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2603, https://doi.org/10.5194/egusphere-egu22-2603, 2022.

EGU22-4922 | Presentations | BG1.2 | Highlight

Development of an arctic-boreal fire atlas using Visible Infrared Imaging Radiometer Suite active fire data

Rebecca Scholten, Yang Chen, James Randerson, and Sander Veraverbeke

Intensifying wildfires in high-latitude forest and tundra ecosystems are a major source of greenhouse gas emissions, releasing carbon through direct combustion and long-term degradation of permafrost soils and peatlands. Several remotely sensed burned area and active fire products have been developed, yet these do not provide information about the ignitions, growth and size of individual fires. Such object-based fire data is urgently needed to disentangle different anthropogenic and bioclimatic drivers of fire ignition and spread. This knowledge is required to better understand contemporary arctic-boreal fire regimes and to constrain models that predict changes in future arctic-boreal fire regimes. 
Here, we developed an object-based fire tracking system to map the evolution of arctic-boreal fires at a sub-daily scale. Our approach harnesses the improved spatial resolution of 375m Visible Infrared Imaging Radiometer Suite (VIIRS) active fire detections. The arctic-boreal fire atlas includes ignitions and daily perimeters of individual fires between 2012 and 2021, and may be complemented in the future with information on waterbodies, unburned islands, fuel types and fire severity within fire perimeters. 

How to cite: Scholten, R., Chen, Y., Randerson, J., and Veraverbeke, S.: Development of an arctic-boreal fire atlas using Visible Infrared Imaging Radiometer Suite active fire data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4922, https://doi.org/10.5194/egusphere-egu22-4922, 2022.

EGU22-5320 | Presentations | BG1.2

Accounting for the impact of slope on fire spread in a dynamic global vegetation model

Luke Oberhagemann, Markus Drueke, Maik Billing, Werner von Bloh, Boris Sakschewski, Henning Rust, and Kirsten Thonicke

Fire modelling incorporated into global dynamic vegetation models (DGVMs) allows for the projection of changes to fire-related biogeophysical and biogechemical processes under future climate scenarios, including anthropogenic climate change. Due to the large grid sizes often required to efficiently model fire and vegetation dynamics in a global manner, fire-enabled DGVMs generally neglect some finer-scale effects, including slope. However, slope can have a significant impact on the spread of individual fires and, therefore, the global area burned. As a fire moves uphill, the angle of flames is better suited to heating nearby fuel, thus increasing the rate of spread relative to fires on level ground. In this study, we apply a function to account for the impact of slope on fire spread in the SPITFIRE model incorporated into the LPJmL5.3 DGVM to improve the calculation of fire-related processes, including burnt area. We aggregate slope data across a grid cell to account for the impact of slope in a general way appropriate to the  grid size used in SPITFIRE. Our approach, while focused on the SPITFIRE model, may also be applicable to other DGVM-based fire models.

How to cite: Oberhagemann, L., Drueke, M., Billing, M., von Bloh, W., Sakschewski, B., Rust, H., and Thonicke, K.: Accounting for the impact of slope on fire spread in a dynamic global vegetation model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5320, https://doi.org/10.5194/egusphere-egu22-5320, 2022.

EGU22-12049 | Presentations | BG1.2

A novel parameterization for wildfire plumes in LPJ-GUESS

Lars Nieradzik and Tommi Bergman

Wildfires are one of the major disturbances in the global terrestrial ecosystems and can be the key driver for both vegetation composition and structure, affecting the carbon stocks above and below the surface. With a total of about 2 Pg(C)/year emitted into the atmosphere wildfires also play an important role in the global carbon cycle. Beyond this, emissions from wildfires influence regional air quality, can have a fertilizing effect on the surroundings, or alter the albedo of both the burned area itself but also of distant areas when e.g. black carbon is deposited on ice sheets or snow. Large fires creating pyrocumulonimbus-clouds even elevate trace gases into the lower stratosphere. 

The chemical and physical evolution of the compounds emitted by wildfires can be simulated by modern CTMs (Chemistry Transport Models) and ESMs (Earth-System Models). A key uncertainty in these models, though, are the fires and the resulting emissions themselves, both in space and amount. Many plume rise models use satellite retrievals for fire intensity as e.g. FRP (Fire Radiative Power) and top height for hindcast or historical simulations, where the accuracy of FRP is anti-correlated with the total emissions because the plume itself blocks the frequencies needed to measure a fire’s intensity, i.e. the larger in scale a fire is the less accurate its intensity, and therefore, it is difficult to generate a vertical emission profile. Furthermore, for future projections, these parameters need to be computed from available information within the operating model.

The approach presented here was developed in the framework of the project CoBACCA and is an attempt to invert this problem. Therefore, we use the 2nd generation dynamic global vegetation model LPJ-GUESS and its incorporated wildfire-model SIMFIRE-BLAZE. Vegetation in LPJ-GUESS is represented by 12 different Plant Functional Types (PFTs; 10 tree and 2 grass PFTs) plus litter and soil pools. In combination with meteorological parameters, the combustion model BLAZE then computes their mortality, their combustion completeness, the intensity of the fire, and finally a vertical emission profile. 

Another critical issue for the use of vertical emissions is that one of the uncertainties in atmospheric models is the height of the planetary boundary layer (PBL) which more or less determines whether emitted air-parcels remain in the mixing layer or reach the free troposphere or even the lower stratosphere. We, therefore, decided to compute the vertical emission profile relative to a model-generated PBL.

These emission profiles will be used online in the upcoming version 4 of the ESM EC-Earth but they can also be used offline as emission inventories for other models. This is a step towards a fully coupled plume-rise sub-grid model to be developed within EC-Earth4.

How to cite: Nieradzik, L. and Bergman, T.: A novel parameterization for wildfire plumes in LPJ-GUESS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12049, https://doi.org/10.5194/egusphere-egu22-12049, 2022.

BG1.3 – Nitrogen Cycling in the Anthropocene: Microbiological Processes, Land-atmosphere- Interactions and Global Change Feedbacks

EGU22-7612 | Presentations | BG1.3 | Highlight

Global hotspots of nitrous oxide mitigation potentials in croplands 

Feng Zhou and Xiaoqing Cui

Mitigating soil nitrous oxide (N2O) emissions is essential for staying below a 2°C warming threshold. However, accurate assessments of mitigation potential are limited by uncertainty and variability in direct emission factors (EFs). To assess where and why EFs differ, we create high-resolution maps of crop-specific EFs based on 1,507 georeferenced field observations. Here, using a data-driven approach, we show that EFs vary by two orders of magnitude over space. At global and regional scales, such variation is primarily driven by climatic and edaphic factors rather than the well-recognized management practices. Combining spatially explicit EFs with N surplus information, we conclude that global mitigation potential without compromising crop production is 30% [95% CI: 17-53%] of direct soil emissions of N2O, equivalent to the entire direct soil emissions of China and the United States combined. Two thirds (65%) of mitigation potential could be achieved on one fifth of global harvested area, mainly located in humid subtropical climate and across gleysols and acrisols. These findings highlight the value of a targeted policy approach on global hotspots that could deliver large N2O mitigation as well as environmental and food co-benefits.

How to cite: Zhou, F. and Cui, X.: Global hotspots of nitrous oxide mitigation potentials in croplands , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7612, https://doi.org/10.5194/egusphere-egu22-7612, 2022.

EGU22-4874 | Presentations | BG1.3

Fungi Contribute Substantially to Nitrous Oxide Production from Highly Acidic Soil

Junhui Yin, Rui Liu, and Qing Chen

EGU22-6700 | Presentations | BG1.3

Nitrification Inhibitor DMPP Reduces Nitrous Oxide Emissions from the Biogas Slurry Amended Soil 

Jilin Lei, Junhui Yin, Rui Liu, and Qing Chen

EGU22-7036 | Presentations | BG1.3

The Combined Application of Nitrification Inhibitor DMPP and Urea-ammonium Nitrogen Fertilizers Reduces Nitrous Oxide Emissions from a Paddy Soil

Dongjia Li, Siping Li, and Rui Liu

EGU22-7968 | Presentations | BG1.3

The short-term effects of enhanced efficiency fertilizers on soil N-cycling genes, and relationship with nitrogen use efficiency in a long-term field experiment

Wei Zhang, Xuan Yang, Xiuchun Xu, Rui Liu, and Fanqiao Meng

EGU22-1945 | Presentations | BG1.3

Predicting the risk of groundwater nitrate contamination using machine learning tools

Xin Huang, Menggui Jin, Xing Liang, Jingwen Su, and Bin Ma

Nitrate contamination in groundwater is affected by both anthropogenic activities and natural conditions, becoming one of the most prevalent problems worldwide. In this study, several machine learning methods including decision tree (DT), k nearest neighbors (KNN), logistic regression (LR), support vector machine (SVM), and extreme-gradient-boosted trees (Xgboost) were applied to predict the risk of groundwater nitrate contamination (NO3- > 50 mg L-1) in the riverside areas of lower reaches of Yangtze River, east China. The developed model included 13 hydrochemical parameters (K+, Na+, Ca2+, Mg2+, Cl-, SO42-, NH4+, NO2-, Fe, Mn, As, Sr, pH) and well depth as explanatory variables, and a total of 1089 groundwater samples. The results showed the hydrochemical dataset could effectively predict the risk of nitrate contamination, with a minimum accuracy of 82.7% in LR and maximal accuracy of 91.7% in SVM and Xgboost. However, only the Xgboost model under a cutoff probability of 0.3 had the best performance with the highest sensitivity of 80.3% and AUC 0.95, whereas other models had sensitivity lower than 60% with insufficient capability of identifying contaminated groundwater samples. The results showed that the ensemble learning method had a strong, robust prediction capability. In addition, the relative importance of K+, SO42-, and Cl- exceeded 0.65, indicating the dominant influence of domestic or industrial sewage in the study area due to widespread urbanization. Finally, we examined the relationship among nitrate contamination risk, land use type, the intensity of anthropogenic activities, and redox conditions and obtained the risk map of nitrate contamination in the study area. This study successfully proved the validity of predicting the risk of groundwater nitrate contamination using machine learning tools, which favors regional groundwater management and protection.

Keywords: groundwater; nitrate contamination; risk prediction; machine learning

How to cite: Huang, X., Jin, M., Liang, X., Su, J., and Ma, B.: Predicting the risk of groundwater nitrate contamination using machine learning tools, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1945, https://doi.org/10.5194/egusphere-egu22-1945, 2022.

Nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) is a crucial link between carbon and nitrogen cycles in estuarine and coastal ecosystems. However, the factors that affect the heterogeneous variability in n-DAMO microbial abundance and activity across estuarine and intertidal wetlands remain unclear. This study examined the spatiotemporal variations in n-DAMO microbial abundance and associated activity in different estuarine and intertidal habitats via quantitative PCR and 13C stable isotope experiments. The results showed that Candidatus 'Methylomirabilis oxyfera' (M. oxyfera)-like DAMO bacteria and Candidatus 'Methanoperedens nitroreducens' (M. nitroreducens)-like DAMO archaea cooccurred in estuarine and intertidal wetlands, with a relatively higher abundance of the M. oxyfera-like bacterial pmoA gene (4.0×106-7.6×107 copies g-1 dry sediment) than the M. nitroreducens-like archaeal mcrA gene (4.5×105-9.4×107 copies g-1 dry sediment). The abundance of the M. oxyfera-like bacterial pmoA gene was closely associated with sediment pH and ammonium (P<0.05), while no significant relationship was detected between M. nitroreducens-like archaeal mcrA gene abundance and the measured environmental parameters (P>0.05). High n-DAMO microbial activity was observed, which varied between 0.2 and 84.3 nmol 13CO2 g-1 dry sediment day-1 for nitrite-DAMO bacteria and between 0.4 and 32.6 nmol 13CO2 g-1 dry sediment day-1 for nitrate-DAMO archaea. The total n-DAMO potential tended to be higher in the warm season and in the upstream freshwater and low-salinity estuarine habitats and was significantly related to sediment pH, total organic carbon, Fe(II), and Fe(III) contents (P<0.05). In addition to acting as an important methane (CH4) sink, n-DAMO microbes had the potential to consume a substantial amount of reactive N in estuarine and intertidal environments, with estimated nitrogen elimination rates of 0.5-224.7 nmol N g-1 dry sediment day-1. Overall, our investigation reveals the distribution pattern and controlling factors of n-DAMO bioprocesses in estuarine and intertidal marshes and gains a better understanding of the coupling mechanisms between carbon and nitrogen cycles.

How to cite: Chen, F., Zheng, Y., and Hou, L.: Microbial abundance and activity of nitrite/nitrate-dependent anaerobic methane oxidizers in estuarine and intertidal wetlands: Heterogeneity and driving factors, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2143, https://doi.org/10.5194/egusphere-egu22-2143, 2022.

EGU22-5889 | Presentations | BG1.3

New insights into moss nitrogen fixation and associated N2 fixer communities from a 1000 Km latitudinal transect in Eastern Canada. 

Jean-Philippe Bellenger, Marie Renaudin, Robert Bradley, and Isabelle Laforest-Lapointe

EGU22-8591 | Presentations | BG1.3 | Highlight

Modelling and evaluating nitrogen transport from land into the ocean

Tobias Stacke, Stefan Hagemann, and Helmuth Thomas

EGU22-35 | Presentations | BG1.3

Nutrient limitation influences moss-associated biological nitrogen fixation in pristine ecosystems

Lina Avila Clasen, Aya Tora Foged Permin, and Kathrin Rousk

EGU22-3066 | Presentations | BG1.3 | Highlight

High off-season nitrous oxide emissions negate potential soil C-gain from cover crops in boreal cereal cropping

Peter Dörsch, Ievina Sturite, and Sigrid Trier Kjær

Enhancing carbon storage in managed soils through increased use of cover and catch crops in cereal cropping is at the heart of a carbon-negative agriculture. However, increased C storage by additional biomass production has a nitrogen cost, both in form of increased N fertilizer use and by potentially increasing nitrous oxide (N2O) emissions when cover crops decay. Frost-sensitive, N-rich aboveground biomass may be a particular problem during wintertime, as it may fuel off season N2O emissions during freezing-thawing cycles, which have been shown to dominate the annual N2O budget of many temperate and boreal sites. Here we report growing season and winter N2O emissions in a plot experiment in SE Norway, testing a barley production system with seven different catch and cover crops (perennial and Italian ryegrass, oilseed radish, summer and winter vetch, phacelia​ and an herb mixture) against a control without cover crops. Cover crops where either undersown in spring or established after harvesting barley. While ryegrass undersown to barley marginally reduced N2O emissions during the growing season, freeze-thaw cycles in winter resulted in significantly larger N2O emissions in treatments with N-rich cover crops (oilseed reddish, vetch) and Italian ryegrass. N2O budgets will be presented relative to aboveground yield and quality of cover crops and compared to potential souil organic carbon gains. 

How to cite: Dörsch, P., Sturite, I., and Trier Kjær, S.: High off-season nitrous oxide emissions negate potential soil C-gain from cover crops in boreal cereal cropping, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3066, https://doi.org/10.5194/egusphere-egu22-3066, 2022.

Most often, yield variability can be associated with differences in topography, soil properties and other environmental factors across agricultural landscapes. Ensuring high yield levels while simultaneously minimizing the risk of N-losses through inadequate use of fertilizers is especially difficult due to the high spatial variability of N transformations originating from those heterogeneities. Thus, understanding of N transformation in heterogeneous agricultural landscapes is key to an efficient and sustainable crop management.

To assess the impact of soil heterogeneity on N transformation processes, a novel field design was established in Tempelberg, North-East Germany. The experimental area was categorized in high yield and low yield potential zones based on historic yield and soil textural maps with field sizes of half a hectare. To display the small-scale soil heterogeneity within the patches, measurements were done along transects of gradients of yield potential.

We hypothesized that low yield soils with sandy texture, low soil water holding capacity (WHC) and locations at lower elevations within the field are associated with low N2O emissions and high N-leaching. In contrast, we expected high yield potential soils located at higher altitudes with a loamy texture to be characterized by high WHC, high N2O emissions and low N-leaching. Additionally, we postulated that edge effects across the transects may play a role due to patch design. We present results of the monthly N2O emission measurements done in fields cultivated with rape seed (Brassica napus L.), sunflower (Helianthus annuus L.) and maize (Zea mays L.), measured with NFT-NSS closed chambers, over a period of 6 months. 15N balances were calculated in the same fields tilled with sunflower (Helianthus annuus L.) and maize (Zea mays L.), by 15N tracer application and evaluation at three time points over growing season. Combination of N transformation processes and gaseous N fluxes in addition with WHC and topography allows for the identification of factors controlling soil N transformation and N availability in agricultural landscapes with high spatial variability of soil properties.

Soil dependent N2O measurements were observed across each transect. Elevation, texture as well as soil water content (SWC) showed a clear influence on N2O emissions. High emissions were measured in plots characterized by a loamy texture, high SWC and locations at higher elevations. In addition, lower emissions were measured at the edge point of the given transect, which could be described as an edge effect.

Evaluations of 15N tracer application results showed significant higher 15N leaching in low yield soils, which tend to have a higher sand content. High yield soils showed lower N-leaching. A strong dependence on soil texture and SWC was visible in the field cultivated with sunflower (Helianthus annuus L.): plots with higher sand content and lower SWC located at the center of the transect showed a higher N-leaching. This finding is in agreement with measured N2O emissions, which were noticeably lower in these areas.

In conclusion, soil heterogeneity in agricultural fields originating from differences in soil texture, SWC and topography show a clear impact on N transformations and N emissions.

How to cite: Zentgraf, I., Hoffmann, M., and Holz, M.: Does soil heterogeneity drive nitrogen transformation in agricultural landscapes? Towards an increased process understanding by quantification of N emissions and N transformation in soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3495, https://doi.org/10.5194/egusphere-egu22-3495, 2022.

EGU22-5064 | Presentations | BG1.3

Gas kinetics and stoichiometry from four fungi incubated under conditions favouring denitrification

Lena Rohe, Reinhard Well, Shahid Nadeem, and Peter Dörsch

Even though the ability of fungi to produce the greenhouse gas nitrous oxide (N2O) during denitrification has been demonstrated, the proportion N2O emissions from fungal denitrification in soils cannot yet be determined or predicted. In order to develop methods for estimating the fungal proportion, N2O must be partitioned to bacterial and fungal denitrification. The denitrification regulatory phenotype (DRP) is well described for a number of bacterial strains (Bergaust et al. 2010, Bergaust et al. 2011), but to our knowledge there are only few data relating to the fungal DRP in terms of oxygen (O2) tension in fully stirred cultures at which they start producing N2O. The aim of this study was to analyse the kinetics of fungal denitrification combined with analysis of the isotopic composition of N2O. In particular, the 15N site preference of N2O (SP-N2O) is known to be a promising tool to differentiate between N2O produced during bacterial and fungal denitrification.

Four fungal species (Fusarium oxysporum, Fusarium decemcellulare, Fusarium solani fsp. pisi and Chaetomium funicola) were incubated as batch cultures in a robotized incubation system (Molstad et al. 2007) for 165h. Batch cultures were incubated in 120 ml flasks containing 50 ml of growth medium amended with ample amounts of carbon and nitrate in a He atmosphere with 2 vol%O2. To test for pH effects, a complex medium (Shoun et al. 1992) with pH values adjusted to 6.9 and 7.4 as well a minimal medium (Dox 1910) with a pH value of about 7.9 were used. O2 consumption and production of nitric oxide (NO), N2O, dinitrogen (N2) and carbon dioxide (CO2) were monitored at high temporal resolution while isotopic composition of N2O was analysed in samples taken manually at selected time points.

All four fungal cultures quickly consumed O2. NO production increased strongly before O2 was completely consumed and was followed by immediate N2O production. The kinetics of N2O production differed to published kinetics of denitrifying prokaryotes by showing a lower sensitivity to O2. This could result in a larger share of fungal denitrification under microaerobic conditions in soil.

Isotopic analysis of N2O confirmed previous results of specifically high SP-N2O values of fungal produced N2O. We further showed that SP-N2O values of fungal N2O are quite stable and do not depend on denitrification kinetics. Likewise, incubation conditions such as pH of the medium had little impact on SP-N2O values. These findings support the usage of SP-N2O values for partitioning N2O soil fluxes and provide a tool to study the biology of fungal denitrification under field conditions, which is needed to develop mitigation strategies of N2O from fungal denitrification.

References:

  • Bergaust, Y. Mao, L. R. Bakken, Å. Frostegård, Appl Environ Microbiol 2010, 76.
  • Bergaust, L. R. Bakken, Å. Frostegård, Biochem Soc Trans 2011, 39.
  • Molstad, P. Dörsch, L. R. Bakken, J Microbiol Methods 2007, 71, 202.
  • Shoun, D.-H. Kim, H. Uchiyama, J. Sugiyama, FEMS Microbiol. Lett. 1992, 94, 277.
  • W. Dox, U.S. Dept. of Agriculture, Bureau of Animal Industry, Washington, D.C., 1910, 70 p.

How to cite: Rohe, L., Well, R., Nadeem, S., and Dörsch, P.: Gas kinetics and stoichiometry from four fungi incubated under conditions favouring denitrification, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5064, https://doi.org/10.5194/egusphere-egu22-5064, 2022.

EGU22-11621 | Presentations | BG1.3 | Highlight

A review of the importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils – changing the paradigm

Michael Dannenmann, Elisabeth Ramm, Chunyan Liu, Per Ambus, Klaus Butterbach-Bahl, Bin Hu, Pertti J. Martikainen, Maija E. Marushchak, Carsten W. Mueller, Heinz Rennenberg, Michael Schloter, Henri M. P. Siljanen, Carolina Voigt, Christian Werner, and Christina Biasi

The paradigm that permafrost-affected soils show restricted mineral nitrogen (N) cycling in favor of organic N compounds is based on the observation that net N mineralization rates in these cold climates are negligible. However, we find here that this perception is wrong. By synthesizing published data on N cycling in the plant-soil-microbe system of permafrost ecosystems we show that gross ammonification and nitrification rates in active layers were of similar magnitude and showed a similar dependence on soil organic carbon (C) and total N concentrations as observed in temperate and tropical systems. Moreover, high protein depolymerization rates and only marginal effects of C:N stoichiometry on gross N turnover provided little evidence for N limitation. Instead, the rather short period when soils are not frozen is the single main factor limiting N turnover. High gross rates of mineral N cycling are thus facilitated by released protection of organic matter in active layers with nitrification gaining particular importance in N-rich soils, such as organic soils without vegetation. Our finding that permafrost-affected soils show vigorous N cycling activity is confirmed by the rich functional microbial community which can be found both in active and permafrost layers. The high rates of N cycling and soil N availability are supported by biological N fixation, while atmospheric N deposition in the Arctic still is marginal except for fire-affected areas. In line with high soil mineral N production, recent plant physiological research indicates a higher importance of mineral plant N nutrition than previously thought.

Our synthesis shows that mineral N production and turnover rates in active layers of permafrost-affected soils do not generally differ from those observed in temperate or tropical soils. We therefore suggest to adjust the permafrost N cycle paradigm, assigning a generally important role to mineral N cycling. This new paradigm suggests larger permafrost N climate feedbacks than assumed previously.

How to cite: Dannenmann, M., Ramm, E., Liu, C., Ambus, P., Butterbach-Bahl, K., Hu, B., Martikainen, P. J., Marushchak, M. E., Mueller, C. W., Rennenberg, H., Schloter, M., Siljanen, H. M. P., Voigt, C., Werner, C., and Biasi, C.: A review of the importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils – changing the paradigm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11621, https://doi.org/10.5194/egusphere-egu22-11621, 2022.

Dissolved organic nitrogen (DON) is a kind of reactive nitrogen in the nitrogen cycling processes, which has been neglected for decades because of the difficulty in measurement, leading to underestimating the nitrogen saturation in the ecosystem. As a result, the need for a complete understanding of DON export behaviors is urgent. This study compares the DON export behaviors to previous studies, focusing on the relationship between DON, dissolved inorganic nitrogen (DIN), dissolved organic carbon (DOC), carbon-nitrogen coupling. We analyzed the data collected at the Fushan Experimental Forest (FEF) in northeastern Taiwan. Preliminary research results showed that (1) behaviors of DON export were unchanged between wet and dry seasons, but only switched at typhoon events, (2) the concentration of DOC was deficient in stream water, (3) unknown endmember between DON and DOC appeared at typhoon events, (4) the high bioavailability of DON occurred in soil and stream water, and (5) the concentration of DOC in soil pool was significantly higher than that of stream water. This study infers that typhoon disturbance appeared to alter the carbon limiting at FEF, causing the change of DON export patterns.

How to cite: Yu, Y.-L., Lee, L.-C., and Huang, J.-C.: Flow regime shifts the carbon-nitrogen coupling of dissolved organic nitrogen losses in a subtropical mountainous catchment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6942, https://doi.org/10.5194/egusphere-egu22-6942, 2022.

EGU22-8543 | Presentations | BG1.3

Real-time soil nutrients monitoring

Ernesto Saiz, Aleksandar Radu, Sami Ullah, Ruben Del-Rio-Ruiz, Mossab Alsaedi, and Sameer Sonkusale

The availability of nutrients is one of the main factors in soils that affect plant growth. This is something that has always been worrying humans; initially using natural fertilizers such as animal and human waste to enhance crop productivity. However, the industrial revolution brought the Haber-Bosch process (artificial nitrogen fixation), which posed a milestone on artificial fertilizers. The production of fertilizers increased exponentially during the twentieth century and is still increasing although at a slower pace. It has had not only positive results, e.g. food production, but is also causing major environmental, health and economic problems.

Because of these problems, it is critical to improve soil management strategies at the precise spatial scales in order to protect human health and the environment, while food production is also guaranteed. To do so, what is needed is a low-cost way to measure nutrients in the soil, in real-time, at different spatial scales.

During recent years, researchers have been working on the adaptation and modification of Ion Selective Electrodes for the analysis of nutrients directly in the soil. However, low precision and accuracy, intense instrument handling (pre and post-calibration), and complex data processing is preventing its general use.

We will present here two modifications of our first prototype of a low-cost ISE-based sensor probe. The probe allows measurements in situ and/or continuous monitoring of up to 16 chemical species. We will here showcase preliminary data obtained by measuring four replicates of four analytes. We also apply the Bayesian calibration methodology previously developed by us in order to improve the precision and accuracy of measurements.

How to cite: Saiz, E., Radu, A., Ullah, S., Del-Rio-Ruiz, R., Alsaedi, M., and Sonkusale, S.: Real-time soil nutrients monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8543, https://doi.org/10.5194/egusphere-egu22-8543, 2022.

EGU22-1481 | Presentations | BG1.3

High nitrogen fixation associated with mosses in tropical cloud forests 

Kathrin Rousk

EGU22-4806 | Presentations | BG1.3 | Highlight

Global NH3 emissions from livestock management : development of a module within a land surface model and impact on atmospheric chemistry

Maureen Beaudor, Nicolas Vuichard, Juliette Lathière, Martin Van Damme, Lieven Clarisse, and Didier Hauglustaine

Ammonia (NH3) is a key species in the atmosphere, playing a crucial role in air quality and climate through the formation of sulfate and nitrate particles. Moreover, NH3 surface deposition alters ecosystems. About 85% of NH3 global anthropogenic emissions are related to food and feed production and in particular to the use of mineral fertilizers and manure management. Even though the estimate of the emissions from livestock can reach 36 Tg N/yr, they are generally not represented explicitly in global land surface models.  Most global chemistry transport models rely on bottom-up emission inventories subject to large uncertainties. Our objective consists of replacing these external emissions data by dynamical emissions computed by ORCHIDEE, a terrestrial ecosystem model including the carbon and the nitrogen cycles. This new version of the ORCHIDEE model includes a detailed integrated scheme for livestock management, from housing and storage to grazing emissions. Ultimately, our work aims at developing an interactive nitrogen cycle model in a coupled climate-chemistry-vegetation model in order to investigate the impact of NH3 emissions from livestock on atmospheric chemistry and climate, and the associated feedbacks.

In this study, we describe and present global NH3 emissions from livestock calculated based on the new version of the ORCHIDEE land surface model . We evaluate NH3 emissions simulated by ORCHIDEE with previous inventories and model estimates. An analysis of key parameters driving the soil NH3 emissions (pH of the manure, the timing of the N application, the surface atmospheric concentration etc… ) have also been performed in order to assess the sensitivity of the simulated emissions. Last, we investigate the impact of prescribing these new simulated emissions on atmospheric chemistry, using the global atmospheric chemistry transport model LMDZ-OR-INCA. The simulated NH3 atmospheric columns are evaluated by global and regional comparisons with the spaceborne IASI instrument measurements. The products used are monthly gridded NH3 distributions using morning observations of IASI-(Metop)A and IASI-(Metop)B for the period 2011-2017. In addition, we compare the ammonia atmospheric columns simulated based on the dynamical livestock emissions and based on reference bottom-up emission inventories. Finally, we investigate the impact of the different NH3 emission inventories on key atmospheric species concentrations.

How to cite: Beaudor, M., Vuichard, N., Lathière, J., Van Damme, M., Clarisse, L., and Hauglustaine, D.: Global NH3 emissions from livestock management : development of a module within a land surface model and impact on atmospheric chemistry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4806, https://doi.org/10.5194/egusphere-egu22-4806, 2022.

EGU22-5378 | Presentations | BG1.3

Invasive mesquite (Prosopis juliflora) reducing soil nitrogen and carbon oxides emissions during rewetting in the Dead Sea valley, Israel.

Ilya Gelfand and Isaac Yagle

EGU22-6937 | Presentations | BG1.3

The effects of drip irrigation with nanobubbles aerated water on soil N transformation

Shahar Baram, Maya Weinstien, Guy Kaplan, and Shmulik Friedman

In recent years, irrigation with nanobubbles aerated water (NB-water) [i.e., air or oxygen-NB (ONB)] has emerged as a new method to alleviate transient hypoxic conditions in the rhizosphere. We aimed to study the effect of surface and subsurface drip irrigation with ONB aerated waters [i.e., fresh (0.4 dS/m), secondary urban treated wastewater (TWW; 1.3 dS/m), saline (3dS/m)] on soil nitrogen transformations. Greenhouse lysimeter experiments were conducted in vertisol (58% clay), sand (98% sand), compost, and sand:compost (1:1) mixture, under well aerated and poorly aerated conditions. Ammonium-N to nitrate-N ratios in the irrigation waters ranged from 15% to 50%.  In all the experiments, irrigation with ONB water, with dissolved oxygen (DO) concentrations of 11 to 35 mg/L, increased the transient buildup of nitrite in the porewater, even under well-aerated conditions (soil air O2> 19%). The most significant effects were observed in the sand, sand:compost, and compost media, where nitrite concentrations were 2 – 8 times greater than the controls and reached over 65 mg/L. Despite the increased nitrite concentrations, irrigation with ONB waters reduced the nitrous oxide fluxes by 4 – 85%. Both phenomena suggested higher oxygen availability in the soil. Nitrite buildup implies that ammonia (NH3) oxidation may not be the rate-limiting step of nitrification under irrigation with ONB aerated water. 

How to cite: Baram, S., Weinstien, M., Kaplan, G., and Friedman, S.: The effects of drip irrigation with nanobubbles aerated water on soil N transformation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6937, https://doi.org/10.5194/egusphere-egu22-6937, 2022.

EGU22-7562 | Presentations | BG1.3

Fertilizer type effect on nitrous oxide (N2O) emissions in a Swedish long-term field experiment

Rong Lang, Muhammad Shahbaz, Katharina H. E. Meurer, Gunnar Börjesson, and Thomas Kätterer

Fertilization in agriculture contributes substantially to an increase in nitrous oxide (N2O) emission to the atmosphere, optimizing fertilization is one of the mitigation strategies to reduce greenhouse gas (GHG) emissions while maintaining high crop production. In the Ultuna long-term frame trial, treatments including organic amendments and different types of mineral nitrogen fertilizers have been applied since1956 to quantify their effects on crop production, soil carbon and nitrogen cycling. However, the understanding of their effect on GHG emissions from soils is still quite limited. For this reason, we chose four treatments, including no fertilizer (control), calcium nitrate, ammonium sulfate and calcium cyanamide to study the mineral fertilizer type effect on N2O emissions and the plant-soil-microbe interactions over one crop growth period.  

N2O fluxes in the growing season were continuously measured from the 1 June to 15 Oct in 2019, using a Picarro N2O analyzer and 12 automated eosAC chambers. The frame trial has a randomized complete block design and we chose treatments in three blocks as replicates. In each plot, we placed two sensors to measure soil moisture and temperature. A mixed model was used to test the effect of fertilizer type and measurement date, with consideration of auto-correlations in the repeated measurements. Soil moisture and temperature were added to the regression model to quantify the controlling factors of the N2O fluxes. Measurement date was treated as a continuous variable.

The effects of both treatment and measurement date were statistically significant. Despite its higher pH values, the calcium nitrate  treatment emitted significantly more N2O than the control: 90.8±23.4 compared with 32.2±8.3 nmol m-2 s-1, respectively. The treatment with calcium cyanamide had pH-values and total N similar to those in the calcium nitrate treatment, but N2O emissions were 72% lower (25.0±6.5 nmol m-2 s-1) than the emission in the calcium nitrate treatment. Due to low soil pH, N2O fluxes were constantly low in the ammonium sulfate treatment, with an average emission of 24.3±6.3 nmol m-2 s-1. The temporal dynamics differed a lot between treatments, as suggested by significant interaction between treatment and measurement date. Further, regression with soil moisture and temperature showed that both variables contributed to explaining the temporal variation of N2O fluxes mainly in the control and calcium nitrate treatments. In contrast, N2O fluxes in the calcium cyanamide treatment were low throughout the growing season, suggesting that it effectively suppressed not only nitrification in the early growing season, but also the denitrification process in the late growing season.

Considering the highest maize biomass and lowest N2O emissions the calcium cyanamide treatment, using calcium cyanamide as nitrogen fertilizer has a great potential to reduce N2O emissions from agricultural soils without compromising crop production.  

How to cite: Lang, R., Shahbaz, M., Meurer, K. H. E., Börjesson, G., and Kätterer, T.: Fertilizer type effect on nitrous oxide (N2O) emissions in a Swedish long-term field experiment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7562, https://doi.org/10.5194/egusphere-egu22-7562, 2022.

EGU22-7977 | Presentations | BG1.3

Atmospheric acidity and its impacts on macronutrient deposition and plant growth

Andrea Arangio, Kalliopi Violaki, Juan-Carlos Quezada Rivera, Megan He, Ghislain Motos, Luca Bragazza, Charlotte Grossiord, Alexandre Buttler, and Athanasios Nenes

Biological diversity and competition among species in ecosystems are sensitive to changes in macronutrient supply and nutrient availability. Human activity is intensively and extensively altering macronutrient cycles from a regional to a global scale with rates that can far exceed natural ones. Moreover, anthropogenic pollution exposes ecosystems to additional nutrients and stressors. These processes, although not well studied, can have a strong impact on ecosystem composition and productivity. In this study, we characterize the atmospheric deposition of bioavailable macronutrients from air pollution and study their impact on plant (oat) productivity and soil quality at a site in the Bois-Chamblard forest outside of Lausanne, Switzerland by Lake Geneva.

To evaluate the importance of atmospheric deposition as a nutrient path for soil and plants, we set up a mesocosm experiment where plants and bare soil were exposed to atmospheric deposition for four months (during Spring and Summer, 2021) and compared against replicates not exposed to atmospheric deposition. Carbon (C), N, P in plant and soil, as well as soil enzymatic activity, fungi and bacterial communities are quantified for each member of the mesocosm experiment. Quantification of the total nitrogen (N) and phosphorous (P), gas- and aerosol-species (inorganic/organic species and metals) in rain water, dry deposition and airborne particles and soil is carried out.

We find that plants exposed to atmospheric deposition display higher photosynthetic activity, larger N content and higher capacity to compete for nutrients in the soil. The soil community in the atmospheric deposition treatment shown higher nitrification rate and enzymatic activity towards lignin decomposition compared to the control. These results indicates that atmospheric pollutants act as plant fertilizers fostering their control on soil microbial community and accelerating soil nutrient stocks consumption.

How to cite: Arangio, A., Violaki, K., Quezada Rivera, J.-C., He, M., Motos, G., Bragazza, L., Grossiord, C., Buttler, A., and Nenes, A.: Atmospheric acidity and its impacts on macronutrient deposition and plant growth, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7977, https://doi.org/10.5194/egusphere-egu22-7977, 2022.

EGU22-8413 | Presentations | BG1.3

Combined effects of elevated temperature and CO2 alters epiphytic cyanobacterial community composition - consequences for nitrogen fixation activity and the host Pleurozium schreberi.

Denis Warshan, Sea-Yong Kim, Andreas Novotny, Ólafur S. Andrésson, and Ulla Rasmussen

EGU22-11430 | Presentations | BG1.3

Risks of converting coniferous forests to broadleaved species

Caitlin Lewis, Martin Lukac, Elena Vanguelova, and Matthew Ascott

Non-native coniferous plantations in the UK have long been associated with potentially negative impacts on surface water and groundwater quality due to high levels of nitrogen accumulation in their soils. Recent changes in UK forestry policy and targets and in attitudes towards biodiversity triggered a shift towards restocking conifer forests with broadleaved species. Broadleaved species are typically associated with lower rates of nitrogen deposition, scavenging and nitrate leaching, so it is often assumed that this change in management will enhance water quality. However, the conversion of coniferous woodland to broadleaved woodland typically stimulates the breakdown of organic matter, leading to a pulse release of nutrients which cannot be taken up rapidly enough by the nascent broadleaved forest.

 

To assess the significance of this process we conducted a study at Thetford Forest, Norfolk, a forest exposed to elevated levels of nitrogen deposition.  We measured throughfall and soil solution chemistry, soil C/N ratios, pH and net nitrification in a chronosequence of stands (0-72 years old) in the conversion process. Observed changes in organic soil C/N ratios indicate the potential for elevated nitrate leaching fluxes within the first decade post-conversion. Results also show an increase in net nitrification in the summer five to eight years post-conversion, followed by an accumulation of nitrogen in the deep mineral soils (30-90 cm depth) ten years post-conversion. Our ongoing analysis of deep soil solution and throughfall chemistry will confirm whether these observations are linked to elevated leaching fluxes in the first decade after conversion. Mature broadleaf stands were unexpectedly associated with greater concentrations of throughfall nitrate from August-October, and lower rates of soil nitrification in the summer than coniferous stands. Further analyses from winter-spring 2022 will explore seasonal variations in throughfall chemistry between broadleaf and coniferous stands in the context of elevated nitrogen deposition.

 

Our observations highlight the need to consider interactions between the effect of land management, seasonality and elevated deposition on nitrogen cycling processes to understand the impact of intensive nitrogen use on terrestrial nitrogen fluxes.    

How to cite: Lewis, C., Lukac, M., Vanguelova, E., and Ascott, M.: Risks of converting coniferous forests to broadleaved species, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11430, https://doi.org/10.5194/egusphere-egu22-11430, 2022.

EGU22-13309 | Presentations | BG1.3

Low atmospheric nitrogen deposition in southern central Siberia does not trigger any nitrogen limitation in the growth of mountain lake phytoplankton

Daniel Diaz-de-Quijano, Aleksandr Vladimirovich Ageev, Nikolay Vladimirovich Moshkin, Elena Anatolevna Ivanova, Yulia Dmitrievna Anishchenko, Olesia Valerevna Anishchenko, and Nadezhda Nikolaevna Sushchik

Anthropogenic disturbances of the nitrogen cycle are one of the most important issues for world ecology. Increased fluxes of atmospheric nitrogen deposition, including ammonium, nitrates, nitrites and other nitrogen oxides characterize the current state of nitrogen cycle. Scientists have found that this process might provide unproductive lakes with nitrogen enough for phytoplankton to turn from nitrogen to phosphorus limitation of growth. Nevertheless, atmospheric nitrogen deposition and its effect on phytoplankton primary production have not been uniformly studied around the world and significant areas remain understudied.

In this study, we measured the winter atmospheric deposition of nitrogen and phosphorus in the snow cover of an understudied region: the Ergaki Natural Park in the south of central Siberia. The concentrations in winter precipitation (40±16 mg of NO3-N m-2 0.58±0.13 mg of total P m-2) were used to estimate yearly yields (119±71 mg of NO3-N m-2 year-1 and 1.71±0.91 mg of total P m-2 year-1). These values approximately corresponded to the forecasts of worldwide mathematical models in the literature and were notably low for terrestrial sites, especially in the case of phosphorus. Measurements of d15N, total N and P in lake sediment cores confirmed the minor role of eventual atmospheric N deposition in the studied lakes, as compared to terrestrial inputs.

The atmospheric nitrogen deposition on the Ergaki mountain ridge was slightly lower than in northern Sweden, where the low atmospheric nitrogen deposition had been found to trigger nitrogen (instead of phosphorus) limitation of phytoplankton growth in unproductive lakes. Nevertheless, atmospheric phosphorus deposition in the study site was among the lowest ones on the mainland, if not the lowest. Due to this extremely low content of atmospheric nutrient deposition, the stoichiometry of N:P in snow and lake water did not correlate, so our lakes did not belong to the group of lakes in the world that are influenced by atmospheric deposition of nutrients. According to our observations, both nitrogen and phosphorus can periodically be limiting factors of phytoplankton in Ergaki lakes.

In conclusion, firstly, the Ergaki Natural Park is an ideal place to study the effects of global warming with a minimal interference of atmospheric nitrogen deposition. Secondly, even at low levels of atmospheric nitrogen deposition in places where atmospheric phosphorus deposition is very low, nitrogen is not necessarily the limiting factor of phytoplankton growth, which may contradict the general character of the currently accepted paradigm. Further studies should check the year-round deposition of nutrients and expand the number of lakes and regions in Siberia, where a significant part of the lakes is not subject to severe anthropogenic pollution.

This study was funded by the Russian Foundation of Basic Research grant number 20-04-00960.

How to cite: Diaz-de-Quijano, D., Ageev, A. V., Moshkin, N. V., Ivanova, E. A., Anishchenko, Y. D., Anishchenko, O. V., and Sushchik, N. N.: Low atmospheric nitrogen deposition in southern central Siberia does not trigger any nitrogen limitation in the growth of mountain lake phytoplankton, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13309, https://doi.org/10.5194/egusphere-egu22-13309, 2022.

EGU22-5489 | Presentations | BG1.3

Glacial Rock Flour as soil fertility amendment increases N fixation activity in red clover and enhances soil N2O reduction.

Fotis Sgouridis, Harry Forrester, Sarah Tingey, and Jemma Wadham

The current climate trajectory in conjunction with agricultural intensification and the reliance on synthetic fertilisers, present further threat to the resilience of future food production through their contributions to soil degradation and consequent climatic feedback. Innovative sustainable agricultural technologies are needed to produce nutritious and equitable food products in line with the UN’s goal for Zero Hunger and sustainable development. Glacial Rock Flour (GRF) is a fine mineral rock dust, made available through the glacial abrasion of bedrock, and is often enriched in nutrients (e.g. Potassium, Phosphorous, Silicon, trace elements) but low in Nitrogen. It would therefore be a suitable soil fertility amendment for legume crops grown in acidic, nutrient poor soils often found in many mountainous regions (e.g. Hindu Kush Himalaya), where GRF is considered an alluvial ‘waste’ silting up dams and reservoirs. We have investigated the effect of GRF soil amendments in soil-plant mesocosms using a typical UK silt loam arable soil (pH~7) for cultivating red clover (Trifolium pratense) inoculated with Rhizobium. GRF from the Chhota Shigri (India) and Sólheimajökull (Iceland) glaciers were applied at 2 and 20 T/ha, while no GRF treatments included synthetic fertilizer applications of phosphorus (P), potassium (K) and P+K, and they were all compared against control red clover plants grown with no soil amendments. The nitrogen fixation capacity of red clover was estimated via 15N natural abundance against a rye grass control (Lolium perenne) in two harvests on weeks 14 and 19. Both 20 T/ha GRF treatments appeared to stimulate fixed nitrogen yield compared to synthetic fertilizer treatments and control red clover plants, while the stimulation was more pronounced in the 2nd harvest as the soil nutrients were progressively depleted. Soil greenhouse gas fluxes over the growth period (weeks 4-14) were monitored by enclosing pots in sealed chambers. While no difference was observed in carbon dioxide fluxes between treatments, nitrous oxide (N2O) flux was negative for all red clover mesocosms with the N2O reduction being more prominent in both 20 T/ha GRF treatments towards the end of the first growth period (week 14). Gross N mineralization and nitrification were estimated in post-harvest soils from all the mesocosms using the isotope dilution method, while 15N-N2O and 15N-N2 production were also measured after amending the soils with 98 at% 15N-NH4+ and 15N-NO3-.  Gross N mineralization was not different between treatments, while nitrification was non-detectable, indicating a very tightly coupled N cycle between Rhizobium and red clover. However, when excess nitrate was applied, bacterial denitrification was active but the amendment of the soils with GRF appeared to reduce the production of N2O and promote complete denitrification to N2. Our novel study on the properties and application of GRF as a sustainable soil fertility amendment under a low nitrogen cropping system, holds promise that it can promote leguminous nitrogen fixation and a tightly-coupled N cycle that maximises N-use efficiency while mitigating N2O emissions by promoting complete denitrification.

How to cite: Sgouridis, F., Forrester, H., Tingey, S., and Wadham, J.: Glacial Rock Flour as soil fertility amendment increases N fixation activity in red clover and enhances soil N2O reduction., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5489, https://doi.org/10.5194/egusphere-egu22-5489, 2022.

BG1.4 – Amazon forest – a natural laboratory of global significance

EGU22-1203 | Presentations | BG1.4 | Highlight

Deforestation and climate change: The multiple pressures over Amazonian forests

Paulo Artaxo, Luiz Augusto Toledo Machado, Marco Aurélio Menezes Franco, Itiara Mayra Barbosa de Albuquerque, Luciana Varanda Rizzo, Julia Shimbo, Ane Alencar, Susan Trumbore, and José Reinaldo Silva

Amazonia is under significant stress from both deforestation and climate change. Multiple pieces of evidence show that the links between the hydrological and carbon cycles are fast changing. Deforestation is increasing in Amazonia, and in 2021, about 13,35 km² of forests were converted, a value 22% larger than 2020. On the deforestation side, the government's recent public policies favor illegal occupation of public lands and invasion of indigenous territories protected by the Brazilian constitution. Deforestation brings forest degradation to the edges of deforested areas, increasing carbon emissions. The impact of climate change is less clear, with changes in the hydrological cycle and increased temperature, promoting forest degradation that makes parts of the Amazon Forest become a carbon source.

The Amazonian forest is a very complex system with multiple anthropogenic and climate change pressures. It is hard to know where a possible Amazonian tipping point could be and which variables or values could be the indicators for this possible tipping point. The role of intensified climate extremes is another critical variable, with Amazonia under increased intense droughts/inundation cycles in the last 30 years. Remote sensing measurements show that vapor pressure deficit is increasing for both perturbed Eastern and at the pristine Northern Amazonia. Several different studies show that the carbon uptake by undisturbed forests is not equilibrating the carbon emissions by deforestation for parts of Amazonia. CO2 emissions associated with deforestation are increasing. The MapBiomas system provides detailed land-use change maps linked to meteorological information to apportion carbon emissions to forest degradation or deforestation. The role of soil emissions is not fully quantified for the overall Amazonia. We are developing a basin-wide system using big data strategies with machine learning, artificial intelligence, and other advanced techniques to address drivers for land-use changes in Amazonia and carbon and methane emissions and sinks. Flooded areas in Amazonia show significant methane emissions, and the effects of increasing floods and droughts cycles have an important impact on methane emissions. First results will be presented, with CO2 and CH4 ground-based and remote sensing measurements in Amazonia, coupled with MapBiomas land-use change maps.

How to cite: Artaxo, P., Toledo Machado, L. A., Menezes Franco, M. A., Barbosa de Albuquerque, I. M., Rizzo, L. V., Shimbo, J., Alencar, A., Trumbore, S., and Silva, J. R.: Deforestation and climate change: The multiple pressures over Amazonian forests, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1203, https://doi.org/10.5194/egusphere-egu22-1203, 2022.

EGU22-8935 | Presentations | BG1.4 | Highlight

Two decades of forest monitoring shows instability in the rainforests

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

The tropical terrestrial ecosystems naturally exist as alternative stable states, commonly referred to as forest and savanna ecosystems. However, these ecosystems, especially forests, are currently threatened by the risk of drought-induced forest-to-savanna transitions across the tropics and subtropics. Therefore, a better understanding of ecosystem dynamics and characteristics behind these alternative stable states is crucial in predicting their response to future hydroclimatic changes. Previous studies have analyzed these alternative stable states against precipitation predominantly based on space-for-time substitution. However, such a substitution provides a partial picture of ecosystem adaptation dynamics and associated ecosystem structural change over time. 

Here, we empirically study the transient state of tropical ecosystems and their hydroclimatic adaptations by examining remotely sensed tree cover and root zone storage capacity over the last two decades in South America and Africa. Tree cover represents the above-ground ecosystem structure's density, and is derived directly from MODIS satellite data. Whereas root zone storage capacity is the maximum amount of soil moisture that the vegetation can access for transpiration is derived using daily precipitation and evaporation data. 

We found that ecosystems at high (>75%) and low (<10%) tree cover adapt to changing precipitation by instigating considerable subsoil investment while experiencing limited tree cover change over time. For these ecosystems, the below-ground investment does not come at the cost of changing the above-ground ecosystem structure. Thus, we deem these ecosystems as stable since ecosystems' adaptive dynamics keep the structural characteristics intact. In contrast, unstable ecosystems at intermediate (30-60%) tree cover were unable to exploit the same level of adaptation as stable ecosystems, thus showing considerable changes to their above-ground ecosystem structure. We also found that ignoring this adaptive capacity of the ecosystem can underestimate the resilience of the forest ecosystems, which we find is largely underestimated in the case of the Congo rainforests. The results from this study emphasize the importance of the ecosystem's temporal dynamics and adaptation in inferring and assessing the risk of forest-savannah transitions under rapid hydroclimatic change.

How to cite: Singh, C., van der Ent, R., Wang-Erlandsson, L., and Fetzer, I.: Two decades of forest monitoring shows instability in the rainforests, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8935, https://doi.org/10.5194/egusphere-egu22-8935, 2022.

EGU22-11505 | Presentations | BG1.4

Extreme droughts and floods in the Amazon forest

Gerbrand Koren, Santiago Botía, Lucas G. Domingues, Liesbeth Florentie, Luciana V. Gatti, Manuel Gloor, Shaun Harrigan, Maarten C. Krol, Ingrid T. Luijkx, John B. Miller, Stijn Naus, and Wouter Peters

In recent years, the Amazon forest has experienced several major droughts (2010, 2015/16) and floods (2012, 2014, 2021). Extreme events represent a threat to the Amazons important functions, but these perturbations also provide valuable insights into the underlying mechanisms. Here we studied the most recent massive drought and flood events in detail, and quantified their severity and spatiotemporal extent relative to a multi-year baseline.

First, we describe the anomalous hydrological status of these events, by bringing together a large variety of data sets, including in-situ observations and reanalysis products for precipitation, discharge, vapor pressure deficit and soil moisture. During the strong El Niño conditions following the dry season of 2015, the precipitation fell below its climatological values. This was soon reflected in low discharge rates and soil moisture levels, persisting far into the year 2016 for some regions. In contrast, we find anomalously high precipitation over the northern Amazon during the first months of 2021, resulting in high discharge rates,  and  rising river levels that have led to massive floods in downstream regions.

Finally, we quantified the impact of the 2015/16 drought on vegetation using the inverse model CarbonTacker South America (CT-SAM) and remote sensing proxies for photosynthesis. To address the uncertainty in prior emission estimates, we have used a range of different biosphere models (SiBCASA, SiB4), including a biosphere model linked to a detailed hydrological model (PCR-GLOBWB). For the fire flux we used multiple data sets (GFAS, SiBCASA-GFED4), including a modified version based on CO inversions performed with the TM5-4DVAR system. We find that photosynthesis was reduced during the 2015 drought, especially in the drier, southern part of the Amazon. This was followed by a recovery in the first months of 2016, but during the subsequent dry season a secondary impact on photosynthesis was found. The inversely derived net CO2 fluxes do not have the same high resolution as the satellite products, but when assessed over larger scales, a consistent drought signal is derived.

How to cite: Koren, G., Botía, S., Domingues, L. G., Florentie, L., Gatti, L. V., Gloor, M., Harrigan, S., Krol, M. C., Luijkx, I. T., Miller, J. B., Naus, S., and Peters, W.: Extreme droughts and floods in the Amazon forest, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11505, https://doi.org/10.5194/egusphere-egu22-11505, 2022.

EGU22-8966 | Presentations | BG1.4

Seasonal and interannual variations of carbon fluxes at the Amazon Tall Tower Observatory site in 2014-2019

Shujiro Komiya, Alessandro Carioca de Araújo, Jost V. Lavric, Bruce Nelson, Matthias Sörgel, Bettina Weber, Santiago Botia, Eliane Gomes-Alves, David Walter, Marta de Oliveira Sá, Stefan Wolff, Davieliton M. Pinho, Fumiyoshi Kondo, and Susan Trumbore

The vegetation and soils of the Amazon contain large amounts of carbon that may be vulnerable to loss given ongoing climate and land use change in the Amazon basin. Previous studies predicted that the Amazon rainforest would start to act as a net carbon source to the atmosphere by 2030-2040, and that it has switched from being a sink to source over the last decade. Using data from eddy covariance and vertical carbon dioxide profile measurement systems installed at the 80 m walk-up tower in the Amazon Tall Tower Observatory (ATTO) site, located in well-preserved central Amazon upland rainforest, we assessed net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (Reco) for the period 2014-2019. The NEE results indicate that the central Amazon upland rainforest was carbon neutral or a source during this 6-year period. Seasonal GPP variations were related to soil water availability and vapor pressure deficit. The strong 2015-2016 El Niño event decreased both GPP and Reco due to the unusually long dry period, but also contributed to carbon flux dynamics in post El Niño periods. In the 2017-dry season, we measured higher dry-season GPP compared with the other years, which we hypothesize was triggered by photosynthesis activation in sub-canopy and understory trees. This is supported by the minimum green crown fraction at upper canopy trees, indicating more light availability in lower canopy trees, and the higher fraction of absorbed photosynthetically active radiation, both recorded during the dry-season of 2017. Our results show that the ground-based measurement setup at ATTO is well suited to investigate the local carbon fluxes on seasonal to interannual time scales.

How to cite: Komiya, S., Carioca de Araújo, A., V. Lavric, J., Nelson, B., Sörgel, M., Weber, B., Botia, S., Gomes-Alves, E., Walter, D., de Oliveira Sá, M., Wolff, S., M. Pinho, D., Kondo, F., and Trumbore, S.: Seasonal and interannual variations of carbon fluxes at the Amazon Tall Tower Observatory site in 2014-2019, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8966, https://doi.org/10.5194/egusphere-egu22-8966, 2022.

EGU22-12016 | Presentations | BG1.4 | Highlight

Assessing social and ecological drivers of fire regimes in the Brazilian Amazon in the context of changing forest governance

Michel Valette, Morena Mills, Jem Woods, Yiannis Kountouris, and Minerva Singh

Whilst the deforestation rate of the Brazilian Amazon has decreased drastically over the 2005-2015 period, thanks to an ambitious program to fight deforestation, since then, forest degradation resulting from logging and wildfires became the major source of aboveground biomass losses and the Brazilian Amazon turned into a net carbon source. This could be partially explained by a decoupling of fire occurrence and deforestation, historically one of the key drivers of the fire regime in the region. Moreover, since 2015, deforestation rates and associated fires are rising again, and new deforestation frontiers are opening in previously unaffected areas in the central and western Amazon.

Fires in the Brazilian Amazon are closely related to climate and agriculture: fires are used to transform forests into pastures or cropland, and subsequent burns are used to maintain grass productivity. When nearby rainforests are sufficiently dry, deforestation and agricultural fires escape and can cause large wildfires. Local communities’ fire management practices impact greatly the likelihood of these escaping fires, but also bear a cost. High mortality rates after even low-intensity fires lead to fuel accumulation and canopy damage, increasing the vulnerability of forests to subsequent burnings. Coupled with a regional reduction of precipitations due to climate change and deforestation, the Amazon forest could be threatened by a cycle of massive dieback and increased fire activity. Thus, it is crucial to understand the drivers of different types of fires in the region and how to prevent them. Of particular interest is the role played by the policies deployed after 2004 to reduce deforestation rates in the region and their recent weakening.

Building on previously published literature on the drivers of fire regimes and deforestation in the region, data were collected on potential drivers of fire regimes related to climate, agricultural expansion, ecosystem integrity, infrastructure, populations, environmental policies and land conflict. MODIS Active-Fire dataset was used as a response variable, and also classified into deforestation fires, agricultural fires and forest fires thanks to deforestation and land use data in a second step of the study. A spatiotemporal modelling approach, relying on the Log Gaussian Cox process and R-INLA package, has been adopted to assess the relative influence of different drivers of fire regimes in the Brazilian Amazon for the 2006-2020 period. Preliminary results on the drivers of fire regime in the state of Para for the last four years show a powerful influence of drivers related to agricultural expansion (especially ranching), integrity of the forest cover, presence of rural settlements and environmental policies. Different protection regimes have varying influences on the fire regime, with sustainable use areas being the less efficient. Law enforcement efforts seem to have an inhibitory effect on fire occurrence and protected area downgrading, downsizing and degazettement favour them.

How to cite: Valette, M., Mills, M., Woods, J., Kountouris, Y., and Singh, M.: Assessing social and ecological drivers of fire regimes in the Brazilian Amazon in the context of changing forest governance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12016, https://doi.org/10.5194/egusphere-egu22-12016, 2022.

EGU22-2592 | Presentations | BG1.4

The ATTO Micrometeorological Intercomparison Experiment (ATMIX)

Luca Mortarini, Nelson Dias, Cleo Quaresma Dias, Daiane Brondani, Otavio Acevedo, Antônio Manzi, Pablo de Oliveira, Anywhere Tsokankunku, Fernando Rossato, Alessandro Araújo, Mathias Soergel, and Carlos Alberto Nobre Quesada

A central constituent of the ATTO project  is the deployment of an array of sonic anemometers to measure vertical profiles of means and second-order moments of the wind velocity vector. The two instruments used are the Campbell Scientific Instruments CSAT-3B and the Thies Ultrasonic Anemometer 3D. The accuracy of the vertical profiles of turbulent quantities critically depensds on an absence of bias between the measurement levels; however, dedicated intercomparisons of the sonic anemometers used in ATTO have not been previously performed.  The main objective of the experiment was to check how close the sonic anemometers designated to be installed respond to the same atmospheric conditions, and to develop confidence in interpreting the measured data. 

How to cite: Mortarini, L., Dias, N., Quaresma Dias, C., Brondani, D., Acevedo, O., Manzi, A., de Oliveira, P., Tsokankunku, A., Rossato, F., Araújo, A., Soergel, M., and Nobre Quesada, C. A.: The ATTO Micrometeorological Intercomparison Experiment (ATMIX), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2592, https://doi.org/10.5194/egusphere-egu22-2592, 2022.

EGU22-3731 | Presentations | BG1.4

Determination of OH radical concentrations between 80-325 m over the Amazon rainforest using BVOC measurements

Akima Ringsdorf, Achim Edtbauer, Jordi Vila-Guerau de Arellano, Jonathan Williams, and Jos Lelieveld

The tropical rainforest is the largest source of VOCs to the global atmosphere [1], where they are oxidized primarily by the hydroxyl radical (OH) [2]. In-situ measurements of OH are rare, especially from tropical forests, but indirect OH estimates can be made using VOC concentrations measured from aircraft or towers. For this it is necessary to measure the vertical change in concentration of a specific VOC with a known OH rate coefficient, within a known reaction time. In this study volatile organic compounds (VOC) were measured on the Amazon Tall Tower Observatory (ATTO) from 3 heights (80, 150 and 325 m) above the Amazon rainforest with a PTR-TOF-MS 4000 (IONICON Analytik GmbH). Typically to estimate OH, the convective timescale of the boundary layer is taken as the approximate reaction time. However, here we have developed a new method to determine the vertical transport based on the dynamic time warping technique. Median averaged transport times from 80 m to 325 m ranged from 105 to 15 minutes with decreasing values throughout the day from 06:00 to 15:00 as thermal and shear driven convection increases. We apply this method to determine effective OH concentrations between 80-325 m using isoprene and its oxidation products (methyl vinyl ketone, methacrolein and ISOPOOH) and compare these empirically derived values to values from the large-eddy simulation DALES [3]. The timescales of turbulent mixing and OH chemistry are similar, so both govern the vertical change in concentration.

[1] Guenther, Alex. “Biological and Chemical Diversity of Biogenic Volatile Organic Emissions into the Atmosphere.” ISRN Atmospheric Sciences 2013 (2013): 1–27. https://doi.org/10.1155/2013/786290.

[2] Lelieveld, Jos, Sergey Gromov, Andrea Pozzer, and Domenico Taraborrelli. “Global Tropospheric Hydroxyl Distribution, Budget and Reactivity.” Atmospheric Chemistry and Physics 16, no. 19 (2016): 12477–93. https://doi.org/10.5194/acp-16-12477-2016.

[3] Vilà-Guerau de Arellano, J., X. Wang, X. Pedruzo-Bagazgoitia, M. Sikma, A. Agustí-Panareda, S. Boussetta, G. Balsamo, et al. “Interactions Between the Amazonian Rainforest and Cumuli Clouds: A Large-Eddy Simulation, High-Resolution ECMWF, and Observational Intercomparison Study.” Journal of Advances in Modeling Earth Systems 12, no. 7 (2020): 1–33. https://doi.org/10.1029/2019MS001828.

How to cite: Ringsdorf, A., Edtbauer, A., Vila-Guerau de Arellano, J., Williams, J., and Lelieveld, J.: Determination of OH radical concentrations between 80-325 m over the Amazon rainforest using BVOC measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3731, https://doi.org/10.5194/egusphere-egu22-3731, 2022.

EGU22-8810 | Presentations | BG1.4

Amazonas Rainfall Modifying Gas Concentration and Forming Nucleation Particles Near the Surface

Luiz A. T. Machado, Christopher Pöhlker, Hartwig Harder, Meinrat O. Andreae, Paulo Artaxo, Santiago Botia, Yafang Cheng, Marco A. Franco, Leslie Kremper, Shujiro Komiya, Jost Lavric, Jos Leliveld, Su Hang, C. Alberto Quesada, Mira Pöhlker, Susan Trumbore, David Walter, Jonathan Williams, Stefan Wolff, and Ulrich Pöschl

This study combines ground-based gas phase, particle, and rainfall measurements at the ATTO site to study the impact of rainfall events on greenhouse and reactive gas concentrations and discuss how this process is relevant for producing new particles. Measurements of CO2, CH4, CO, O3, NO, and NO2 concentrations were collected from the surface to 79m using a tower at the ATTO site in the central Amazon forest northeast of Manaus, Brazil. Particle size distribution was measured by an SMPS and rainfall by a rain gauge at the top of the tower. Data collection started in 2012, and this analysis covered the period up to 2020. The 30-minute interval dataset was used to study how convective events modify the concentration of these gases. During the rainfall events, CO2, CO, and CH4 concentrations decrease, though CH4 varies less with height than CO and CO2. The daily cycle of NO2 presents an interesting characteristic showing distinct daily evolution for the concentration in the upper and lower levels. The decrease in NO2 concentration in the upper level and the increase near the surface in the afternoon, which is the typical time of rainfall events, indicate that a specific process occurs near the surface. With the joint analysis of gas-phase observations with ultrafine particles and rainfall data, it was possible to evaluate the interesting physical-chemical processes occurring during the rainfall events that might be important for particles nucleation. The time of rainfall events was defined as the first-time rain rate reaching 3 mm/hours, a typical value of the beginning of convective rainfall events. Interestingly, during rainfall events, there is a significant injection of O3 above and inside the canopy, and at this moment, its concentrations can increase by 300%. At the same time, NO decreases, and NO2 increases its concentration, suggesting a reaction between NO and O3 forming NO2. The concentration of NO2 follows the increase in particle concentration smaller than 20nm. This result opens new perspectives on the role of new particle formation related to rain and vertical mixing in the Amazon.

How to cite: Machado, L. A. T., Pöhlker, C., Harder, H., Andreae, M. O., Artaxo, P., Botia, S., Cheng, Y., Franco, M. A., Kremper, L., Komiya, S., Lavric, J., Leliveld, J., Hang, S., Quesada, C. A., Pöhlker, M., Trumbore, S., Walter, D., Williams, J., Wolff, S., and Pöschl, U.: Amazonas Rainfall Modifying Gas Concentration and Forming Nucleation Particles Near the Surface, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8810, https://doi.org/10.5194/egusphere-egu22-8810, 2022.

EGU22-11693 | Presentations | BG1.4

Tropical forest CH4 budget: the importance of local hotspots

Hella van Asperen, Thorsten Warneke, Alessandro De Araújo, Bruce Forsberg, Sávio Ferreira, João Alves-Oliveira, Leonardo Ramos de Oliveira, Thiago de Lima Xavier, Marta Sá, Paulo Teixeira, Elaine Pires, Veber Moura, Shujiro Komiya, Santiago Botia, Sam Jones, Jost Lavrič, Susan Trumbore, and Justus Notholt

Methane (CH4) is one of the most important anthropogenic greenhouse gases. Despite its importance, natural sources of methane, such as tropical wetlands and termites, are still not well understood and a large source of uncertainty in the tropical CH4 budget. The Amazon rainforest is a key region for the (global) CH4 budget but, due to its remote location, local CH4 concentration and flux measurements are still rare.

Fieldsite ZF2 (60 km NW of Manaus, Brazil) is located in pristine tropical rain forest. At this fieldsite, a Spectronus FTIR-analyzer (measuring CO2, CO, CH4, N2O & δ13CO2) was installed at the foot of the K34 tower, set up to measure different heights above and below the canopy continuously. In addition, by use of a Los Gatos portable analyzer (measuring CO2 & CH4), additional semi-continuous concentration measurements were performed at the valley tower (studying the nighttime build up of valley CH4), above the igarapé  (capturing the CH4 ebullition bubbles leaving the water surface), and on the plateau (studying the spatial horizontal heterogeneity of CH4 concentrations within the canopy). Furthermore, the portable analyzer was used for soil, water, termite mound, and termites flux measurements.

By combining tower and flux chamber measurements, the role and magnitude of different ecosystem sources could be assessed. We observed that, while soils in the valley are a small source of CH4 (0.1 to 0.2 nmol CH4 m-2 s-1), overall the soils of this ecosystem are expected to be a net CH4 sink (-0.3 to -0.5 nmol m-2 s-1 ). Estimated total ecosystem CH4 flux, based on nighttime concentration analyses of the tower data, indicate that the ecosystem is a net CH4 source (~1 to 2 nmol CH4 m-2 s-1). We propose that the net CH4 emission of the ecosystem is driven by local emitting hotspots, such as the valley stream and standing water, termites and termite mounds (~1 nmol CH4 m-2 s-1), anoxic soil spots and decaying dead wood.

 

How to cite: van Asperen, H., Warneke, T., De Araújo, A., Forsberg, B., Ferreira, S., Alves-Oliveira, J., Ramos de Oliveira, L., de Lima Xavier, T., Sá, M., Teixeira, P., Pires, E., Moura, V., Komiya, S., Botia, S., Jones, S., Lavrič, J., Trumbore, S., and Notholt, J.: Tropical forest CH4 budget: the importance of local hotspots, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11693, https://doi.org/10.5194/egusphere-egu22-11693, 2022.

EGU22-13294 | Presentations | BG1.4

Ecosystem nutrient budget in a Central Amazon forest: the role of nutrient stocks and flows in biogeochemical cycling

Pâmella Assis, Laynara F. Lugli, Izabela Aleixo, Luciana R. Bachega, Sabrina Garcia, Flavia Santana, and Carlos A. Quesada

Soils of tropical forests generally have low fertility, therefore nutrient cycling has great importance in these ecosystem functions, once these soil elements are essential for vegetative tissue and plant metabolic processes. Understanding and quantifying the processes that involve nutrient acquisition, storage, and output in plants, and their relationship with forest productivity and biomass, is essential to characterize the ecosystem nutrient dynamics and understand how global environmental changes, such as the increase in CO2 can affect forest processes. Therefore, we investigated the nutrient dynamics of a terra firme forest in Central Amazonia, near Manaus, Brazil through the quantification of stocks, flows, and nutrient use efficiency in different compartments to estimate forest nutritional balance. We quantified the biomass stocks in the forest compartments – fine root, leaves, litterfall and stems – and their macro (N, P, Ca, Mg e K) and micronutrients (Fe, Mn e Zn) content. We estimated the nutrient fluxes through productivity rates, the nutrient stocks, and the nutrient efficiency, the inverse of nutrients concentration. Most of this information was available from the AmazonFACE (Free-Air CO2 Enrichment) baseline data. The study area has 8 permanent plots monitored since 2015 with periodic field collections and monitoring. We hypothesized that the macronutrient that cycles more efficiently in the ecosystem will potentially be the most limiting element to forest net primary productivity, adding to a better understanding of nutrient allocation and cycling, and greater accuracy in predictions from global vegetation dynamics models. The total forest biomass (above and belowground) in our study site was 200.85±0.52 Mg C ha-1 and the productivity 9.79±0.22 Mg C ha year-1. These results are higher than previous studies reported in the amazon forest. Ecosystem nutrient flow was greater in leaves > litter standing crop > fine roots > stems. On the other hand, ecosystem nutrient stocks were greater in stems > leaves > fine root > litter standing crop.  Our preliminary results show that phosphorus stock and flow are lower than other macronutrients, being, therefore, cycled more efficiently than other elements studied here. This suggests that phosphorus is potentially the macronutrient that most limits net primary productivity. For nitrogen, we observe a low-efficiency use, which was expected since this element is abundant in Central Amazon soils;  for potassium an intermediate efficient use, so the order of stocks and flows is N > K > P. For micronutrients nutrient efficiency use was as follows: zinc > magnesium > iron. These results suggest that phosphorus could be considered the most limiting macro nutrient to forest net primary productivity while zinc availability could also play a role. Our estimates of nutrient stocks and flows for a Central Amazon forest would improve our understand different nutrient dynamics and demands that impact biogeochemical cycles and functioning of these forests.

How to cite: Assis, P., Lugli, L. F., Aleixo, I., R. Bachega, L., Garcia, S., Santana, F., and Quesada, C. A.: Ecosystem nutrient budget in a Central Amazon forest: the role of nutrient stocks and flows in biogeochemical cycling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13294, https://doi.org/10.5194/egusphere-egu22-13294, 2022.

EGU22-13341 | Presentations | BG1.4

How does leaf phenology define upper canopy functional structure in a central Amazon upland forest? 

Pedro Ivo Lembo Silveira de Assis, Giordane A. Martins, Izabella Sanches, Bruce W. Nelson, Marta Sá, Jurgen Kesselmeier, and Antonio O. Manzi

Leaf phenology impacts carbon, nutrient, and hydrological cycles from local to global scales. In central Amazon rainforest, the timing of leaf flush and abscission promotes a seasonal change in leaf age composition of the upper canopy. It has been singled out as the most important driver of photosynthetic capacity (PC) seasonality. However, limitations concerning on two important issues must be raised: 1) canopy leaf age temporal variation has not been directly assessed and 2) this approach has an empirical assumption that canopy leaf area should be fully replaced after 12 months. The first issue implies PC to be obtained by flux-towers measurements to estimate leaf age composition of the upper canopy. So, it is not a reliable representation of age distribution of the upper canopy. The concerning about the second issue relies on that tropical rainforest trees are known to present different leaf phenological patterns (e.g. deciduousness and evergreenness) which are correlated to leaf lifespan (LL), like for a year or more. Besides, leaves presenting higher LL show differences on PC compared to those of short ones, both in their maximum PC and its decay rate while aging. That means if leaves from plants with different leaf phenological pattern have the same age (e.g. in months), they will differ on their PC. Therefore, there is a necessity to elucidate leaf phenological patterns and unravel temporal changes on leaf age composition of upper canopy and LL variability. From August 2016 to November 2019 at the Amazon Tall Tower Observatory (ATTO), tagged leaves were censused monthly on ten upper canopy branches per tree (n = 36 trees). Temporal variation of storage, flush and abscission of leaves were recorded. Chronological ages were only possible for leaves flushing during the study period. Similarly, LL was obtained from leaves when both flush and abscission date were observed throughout the monitoring period. Around 80% of the trees flushed new leaves massively during the dry season. Eight of them (22%) fell into brevi-deciduous category while twenty-eight (78%) into evergreenness. Canopy leaf quantity proved to be nonseasonal as expected. On the other hand, seasonal change in leaf age composition of the upper canopy was confirmed. Still, it sheds light on its complex and diverse stratification. In the last month of monitoring, leaf age ranged from 0 to 43 months with only half of the leaves being younger than a year. Thus, leaf flush and leaf abscission present a seasonality. However, at least almost half of them have a lifetime longer than a year. This result suggests that half of the leaves from upper canopy are being neglected by the models. The LL presented a bimodal distribution (n = 2552 leaves) with two peaks around one year and two years, respectively. This suggest there are annual and biannual leaf phenological patterns between upper canopy trees. However, individual trees still show a bimodal distribution of LL frequency. This implies LL should not be used as a leaf functional trait to define plant functional groups.

How to cite: Lembo Silveira de Assis, P. I., Martins, G. A., Sanches, I., Nelson, B. W., Sá, M., Kesselmeier, J., and Manzi, A. O.: How does leaf phenology define upper canopy functional structure in a central Amazon upland forest? , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13341, https://doi.org/10.5194/egusphere-egu22-13341, 2022.

EGU22-9067 | Presentations | BG1.4 | Highlight

AmazonFACE – Assessing the response of Amazon rainforest functioning to rising atmospheric CO2 concentration

Anja Rammig and David Lapola and the AmazonFACE team

The rapid rise in atmospheric CO2 concentration over the past century is unprecedented. It has unambiguously influenced Earth’s climate system and terrestrial ecosystems. Plant responses to rising atmospheric CO2 concentrations are thought to 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, while 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 have been developing a free-air CO2 enrichment (FACE) experiment in an old-growth, highly diverse, tropical forest in the Brazilian Amazon and we 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 recent results from the open-top chamber experiments on understorey saplings under rising CO2 and phosphorus fertilization, recently conducted at the AmazonFACE site. We give an overview over phosphorus uptake strategies and potential modelling approaches.

How to cite: Rammig, A. and Lapola, D. and the AmazonFACE team: AmazonFACE – Assessing the response of Amazon rainforest functioning to rising atmospheric CO2 concentration, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9067, https://doi.org/10.5194/egusphere-egu22-9067, 2022.

EGU22-2869 | Presentations | BG1.4

An open-top chamber system for exposing Amazon understory vegetation to elevated atmospheric CO2

Iokanam Pereira, Bruno Takeshi, Alacimar Guedes, Crisvaldo Souza, Carlos Quesada, and David Lapola

Tropical forests play a key role in the flux of terrestrial carbon (C). However, recent studies show tropical forest are losing over the years the ability to sink C from the atmosphere, one of the best explanations for that is the climate change caused by humanity in the last centuries and accelerating slightly every year. One of the ways to understand the changes in C fluxes in forest ecosystems in the short, medium, and long term are the Earth system models (ESMs). Nevertheless, simulations demonstrate that ESMs are not able to represent the decline in C sink by tropical forests in recent decades. Experiments that fertilize the atmosphere with carbon dioxide (eCO2) are essential to reduce uncertainties in future ESM projections about the possible effects of eCO2 on the carbon cycle. Open top chamber (OTC) allow the exposure of understory vegetation to eCO2 allowing the control and monitoring of the microenvironment in which they are inserted. Here, we describe the OTC system currently operating in the Amazon Free-Air CO2 Enrichment research program (AmazonFACE) in a mature forest in Central Amazonia, the analysis period is from 01/01/2020 to 12/31/2020. Each OTC is 2.40 m in diameter by 3.00 m in height, in which the concentration of CO2 ([CO2]) is monitored minute-by-minute using infrared gas analyzers, allowing the spatial and temporal control of [CO2]. The operation consists of keeping the [CO2] in the treatment OTCs (i.e., with eCO2) ≈ 200 µmol. mol1 above the [CO2] of the control OTCs (i.e., without eCO2) in the daytime (between 6:00 am - 6:00 pm). The [CO2] measurements on the treatment and control OTCs show that the desired concentration was successfully delivered, +262.4 ± 25.5 µmol / mol (mean ± SD) of the desired setpoint, i.e., 31 % above setpoint target. The eCO2 in the treatment OTCs worked 91% of the analyzed operational time, the remaining time was wasted with engineering failures (3%) and problems with the supply of CO2 (6%). The system was able to maintain the [CO2] above the setpoint, showing that the system configuration is capable of exposing understory vegetation even in a highly complex environment. The results demonstrate that the in-situ OTC system presented can be reproduced in different types of ecosystems, allowing better knowledge about metabolic processes that occur between atmosphere-plant-soil.

How to cite: Pereira, I., Takeshi, B., Guedes, A., Souza, C., Quesada, C., and Lapola, D.: An open-top chamber system for exposing Amazon understory vegetation to elevated atmospheric CO2, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2869, https://doi.org/10.5194/egusphere-egu22-2869, 2022.

EGU22-8975 | Presentations | BG1.4

Short-term responses of Inga edulis Mart. seedlings growing under elevated CO2 and phosphorus addition: understanding potential phosphorus constraints on plant responses to elevated CO2 in the understory of a central Amazon forest     

Gabriela U. Neves, Vanessa R. Ferrer, Sabrina Garcia, Vinicius F. de Souza, Tomas Domingues, Izabela Aleixo, Henrique Tozzi, Pedro A. C. L. Pequeno, Nathielly P. Martins, Alacimar Guedes, Iokanam S. Pereira, Juliane C. G. Menezes, Amanda R. M. Damasceno, Yago R. Santos, Maquelle N. Garcia, Anna C. M. Moraes, Ana Caroline M. Pereira, Bart Kruijt, and Carlos A. N. Quesada and the AmazonFACE Team

The increase in atmospheric CO2 concentration positively affects plant carbon assimilation and carbon stock in different biomes. However, there are uncertainties regarding how plants in tropical forests, especially in the Amazon rainforest, will respond to this increase, since a large part of the soils in the region present natural low phosphorus (P) availability, which could constrain positive effects of elevated CO2. Here, we investigated if P addition would interfere on leaf primary carbon metabolism and aboveground development responses under elevated CO2. For that, we used 46  seedlings of Inga edulis Mart., a native leguminous nitrogen-fixing species, exposed for 10 months (November 2019 - September 2020) to CO2 and P treatments. Plants grew in pots - half with natural P availability (-P) and half with P addition (+P) -, inside CO2 enrichment chambers - half with ambient CO2 (aCO2) and half with elevated CO2 (aCO2 + 200 ppm; eCO2), - in the understory of a primary forest in Central Amazonia, Manaus, Brazil.  A factorial experimental design was used, with 11-12 plants for each treatment: aCO2-P (control), aCO2+P, eCO2-P and eCO2+P. To assess the carbon metabolism, we measured light-saturated net CO2 assimilation (Asat), leaf respiration in the light (Rlight), leaf respiration in the dark (Rdark) and photorespiration (PR). To assess aboveground development, we measured plant height and diameter, crown height and diameter,  number of leaves and total leaf area. We found that eCO2, regardless of P availability, significantly increased Asat and Rlight, while decreasing Rdark and Asat:Rdark ratio, but it did not affect PR . Those results suggest that seedlings indeed assimilated more carbon under eCO2. However, irrespective of CO2 treatment, +P significantly increased aboveground responses. Under P addition, plants showed greater height and greater crown development (higher crown height and diameter and larger leaves) compared to control or eCO2-only. Plant diameter and number of leaves did not respond to any treatment. We did not find differences between +P seedlings under different CO2 treatments (aCO2+P and eCO2+P), indicating that only P had an effect on these responses. Still, there were substantial changes on some of the aboveground responses between these treatments, particularly in total leaf area which increased 60% (aCO2+P) and 126% (eCO2+P) compared to control. Overall, we observed a distinguished pattern, in which eCO2 mainly affected physiological responses, while P addition consistently affected aboveground development. The lack of response of aboveground components under eCO2 suggests that the extra carbon assimilated was not necessarily used to aboveground development as shown by many studies. Our findings indicate that, in the short-term, eCO2 is highly important in determining changes in plant metabolism whereas it has little impact on growth, even when nutrient limitation is alleviate. However there is still need to understand if such responses will persist in the long-term and in other species, as these processes are key factors in determining forest responses to climate change.  

How to cite: U. Neves, G., R. Ferrer, V., Garcia, S., F. de Souza, V., Domingues, T., Aleixo, I., Tozzi, H., A. C. L. Pequeno, P., P. Martins, N., Guedes, A., S. Pereira, I., C. G. Menezes, J., R. M. Damasceno, A., R. Santos, Y., N. Garcia, M., C. M. Moraes, A., M. Pereira, A. C., Kruijt, B., and A. N. Quesada, C. and the AmazonFACE Team: Short-term responses of Inga edulis Mart. seedlings growing under elevated CO2 and phosphorus addition: understanding potential phosphorus constraints on plant responses to elevated CO2 in the understory of a central Amazon forest     , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8975, https://doi.org/10.5194/egusphere-egu22-8975, 2022.

EGU22-2703 | Presentations | BG1.4

The effects of elevated CO2 and phosphorus limitation shaping fine root functioning in Central Amazon forests

Laynara F. Lugli and Carlos Alberto Quesada and the AmazonFACE team

One of the most important questions that remain open in terrestrial ecology refers to how the Amazon rainforest, the largest tropical forest in the world, will respond to elevated atmospheric CO2. Since a large part of the Amazon grows in soils with very low phosphorus (P) availability, understanding how potential nutrient limitation could impact forests in a changing world becomes crucial. There is strong evidence for a positive effect of elevated CO2 on plant growth but sustaining such a response in the Amazon would require plants to increase their access to P, making it important to understand the effects of elevated CO2 on root P-uptake strategies. To this end, we installed eight Open Top Chambers (OTC) in an understory forest in Central Amazon in Manaus, Brazil, being four control with ambient CO2 (aCO2) and four treatment with +200 ppm CO2 (eCO2). Inga edulis, a common N-fixing tree in the area, was chosen as study species. In each OTC, I. edulis was grown in six pots, three containing control soil from the study area and three containing control soil with 600 mg/kg of P added as triple super phosphate. After two years, plants were harvested and total soil respiration, total root dry mass, root nodulation, root morphological traits (mean diameter, specific root length – SRL, specific root area – SRA and root tissue density – RTD) and potential root phosphatase activity were measured. Total soil respiration was significantly higher in both treatments with eCO2 when compared to treatments with aCO2. Total dry root biomass followed a similar pattern, and root biomass in the eCO2 and P+eCO2 treatments were twice that of the other two aCO2 treatments. Plants invested in more fine roots (< 1 mm diameter) than in coarse roots with eCO2-only, whilst in P+eCO2, both fine and coarse roots biomass increased. No nodules were detected in control plants, whilst almost 75% of plants growing in P+eCO2 and 30% of plants growing in eCO2-only and P-only displayed nodulation. Mean fine root diameter for plants growing in eCO2-only was significantly higher than all other treatments, leading to a significant decrease in SRL and RTD, with no changes in SRA. In both treatments with eCO2, fine root phosphatase activity (expressed per root dry mass and specific area) significantly decreased in comparison to aCO2. However, when extrapolating root phosphatase activity for total fine root biomass, pot-level phosphatase exudation was twice as high in eCO2 than in aCO2 treatments. Our results clearly point to a shift in plant belowground strategies, suggesting an even stronger control of nutrient acquisition mechanisms by eCO2 than P addition. With eCO2, plants allocated much more biomass to fine roots and nodules, rather than increased phosphatase exudation per root-unit. Such trade-off suggests that in this scenario, plants might acquire P directly by exploring higher soil volumes, whilst allocating extra C to N-fixing bacteria. We demonstrate how eCO2 and P availability can shape belowground plant traits pointing to important trade-offs that could determine ecosystem-scale changes in future climate scenarios.

How to cite: F. Lugli, L. and Quesada, C. A. and the AmazonFACE team: The effects of elevated CO2 and phosphorus limitation shaping fine root functioning in Central Amazon forests, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2703, https://doi.org/10.5194/egusphere-egu22-2703, 2022.

EGU22-10939 | Presentations | BG1.4 | Highlight

Effects of soil fertilization on aboveground biomass in an old-growth forest in Central Amazon

Bárbara Brum, Carlos A. Quesada, Rafael Assis, Juliana Schietti, Izabela Aleixo, Raffaello di Ponzio, Iain Hartley, Kelly Andersen, Hellen F. Cunha, Laynara Lugli, Nathielly Martins, Renata Almeida, Maria Pires, Nívia Pinheiro, Anna C. Moraes, José L. Camargo, Gyovanni Ribeiro, Bruno Takeshi, Lara Siebert, and Felipe Andrade

The Amazon covers an extensive area of tropical rainforest that directly affects global water and Carbon cycles. The biomass stored in this forest is a result of the dynamic balance between rates of mass gain due to productivity, and losses due to respiration and mortality. In general, these forests concentrate about 70-80% of biomass in the aboveground part, and the regional variation of AGB (aboveground biomass) can be explained by the compositional, structural, climatic and by differences in soil propriety and fertility between East-West gradient in the Amazon basin. This gradient drives a large set of variations in tree growth and mortality, resulting in differences on the forest structure and dynamics. In this context, direct manipulation of nutrients in soils is a powerful tool to investigate which elements limit tree growth and forest productivity. While nitrogen (N) is accumulated along soil development and age, the availability of rock-derived phosphorus (P) and cations may limit the ecosystems' functioning, including the potential increase in the productivity in response to elevation on CO2 concentrations in the atmosphere. To understand these patterns, a long-term, large-scale soil fertilization experiment in Amazonian forests (AFEX) was implemented in the Central Amazon. In 2017, 32 permanent plots were installed in areas of old-growth continuous forest belonging to the Biological Dynamics of Forest Fragments Project (PDBFF), in a full factorial design, with four blocks chosen at random, where 8 plots (each with a size of 50x50 m) were installed with different fertilization treatments for each block. The treatments are: P, N, cations, Control (no fertilization), N+P, N+cations, P+cations and N+P+cations. To estimate the effects of soil fertilization on AGB, we calculated the difference between biomass before and after four years of fertilization (2017 to 2021), using allometric equations performed data from diameter about 5,000 individuals (DAB ≥ 10 cm) measured annually and wood density. We analyzed the data with two different approaches, at the community and at genus level, considering three most abundant genera: Eschweilera, Pouteria and Protium. At community level, our results showed only non-significant trends between AGB in plots where N, P and cations were added. At genus level, we observed that Eschweilera and Protium had a negative relationship to N and Pouteria had a positive trend.  Conversely, only Protium increased AGB with P addition.  Pouteria and Protium was negatively affected by cations, while Eschweilera showed no response. These results indicate that, although overall positive or negative trends in biomass increment appear at the community level, the highly diverse forest studied does not have a homogeneous response to nutrient addition, and that each taxonomic group could potentially be limited by different nutrients. In the long term, we expect that these patterns may change the forest structure, dynamics and composition and, consequently, the stocks of biomass, impacting the functionality of these forests. These results improve our understanding of the role of nutrients affecting forest biomass, and may reduce uncertainties in vegetation dynamics models and predictions on environmental changes.

How to cite: Brum, B., Quesada, C. A., Assis, R., Schietti, J., Aleixo, I., di Ponzio, R., Hartley, I., Andersen, K., Cunha, H. F., Lugli, L., Martins, N., Almeida, R., Pires, M., Pinheiro, N., Moraes, A. C., Camargo, J. L., Ribeiro, G., Takeshi, B., Siebert, L., and Andrade, F.: Effects of soil fertilization on aboveground biomass in an old-growth forest in Central Amazon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10939, https://doi.org/10.5194/egusphere-egu22-10939, 2022.

BG1.6 – (Bio)geochemistry of redox sensitive elements in oxic, anoxic, and euxinic environments

EGU22-12143 | Presentations | BG1.6 | Highlight

Vertical distribution and aerobic degradation at the sediment-water interface in two urbans estuaries in Normandy, France

Amonda El Houssainy, Isabelle Poirier, Martine Bertrand, Laure Verdier, and Florian Cesbron

In the current context of climate change, the coastal area is exposed to an increasing pressure from hydrodynamic agents such as tide, flood and storm (Parry et al., 2007) and to enormous anthropogenic activities due to urbanization and industrialization of the coastline, which weakens the coastal ecosystem. In France, the Manche department presents more than a half of the Normandy coastline (330 km) and a great diversity of its shores. It is a key player in the preservation of the coastal environment. Among its conservation areas, two estuaries in Saint-Vaast-La-Hougue interested us: the Saire Estuary and Cul-de-Loup Bay, which both subjects to the impact of human activities (agriculture, shellfish farming, tourism, modification of the coastline, etc.). In order to quantify the chemical and biological exchanges in the mudflat of these two sites, we performed dissolved oxygen profiles in the sediment using a benthic microprofiler system (Unisense®). Moreover, sediment cores were collected and sliced under inert atmosphere, in order to measure diagenetic tracers (NH4+, PO43-, Fe2+ and ΣHS-) and trace metals levels, and to identify bacterial communities. The results of sediment cores and oxygen microprofiles taken from each of the mudflat indicate a greater dynamic degradation of organic matter in the superficial sediments of Saire estuary and in deep sediment of Cul-de-Loup Bay. The benthic microprofiler results show that oxygen penetration depth is around 1 mm and 1.4 mm respectively in Saire estuary (n=3) and Cul-de-Loup bay (n=5). This difference is marked by (i) an intense reduction of Fe (oxy)hydroxides at 4 cm of sediment depth in the Saire estuary, (ii) the appearance of ΣHS- from ~ 12 cm of sediment depth against 5 cm of sediment depth in the Cul-de-Loup Bay and (iii) a slight Fe(oxy)hydroxide zone at 3 cm of sediment depth. Metagenomics analysis confirm major differences between the two study sites.