Content:

BG – Biogeosciences

BG2 – Tropical ecosystems – biomes of global significance in transition

EGU21-11283 | vPICO presentations | BG2 | Highlight

How Weather Events Modify Amazonian Surface Aerosol Particle Size Distributions

Luiz A. T. Machado, Mira Pöhlker, Paulo Artaxo, Micael Cecchini, Florian Ditas, Marco A. M. Franco, Leslie Kremper, Meinrat O. Andreae, Ivan Saraiva, Ulrich Pöschl, and Christopher Pöhlker

In the last years, several studies were published evaluating aerosol-cloud-precipitation interactions. These studies improved the knowledge and reduced the uncertainties in the quantification of the aerosol aerosol-cloud interactions. However, there were only very few attempts to describe how clouds modify the aerosol properties. The main goal of this study is to evaluate the effect of weather events on the Particle Size Distribution (PSD) at the Amazon Tall Tower Observatory (ATTO). This research combines different types of datasets, all co-located at the ATTO towers. Basically, the data were obtained from the new generation of GOES satellites, GOES-16, the SIPAM S Band radar and two Scanning Mobility Particle Sizers (SMPS) installed at the heights of 60 and 325 m from 2017 to 2020. In addition, the LAP 3000 radar wind profile recently installed at the ATTO- Campina site was employed to evaluate the vertical distribution of the vertical velocity. The combination of these datasets allows to explore changes in PSD due to the different meteorological processes. The diurnal cycle shows an increase of nucleation particles and decrease in Aitken and accumulation modes during the night. The early morning is the time of minimum mass concentration. From the early morning to the middle of the afternoon, a contrary behaviour is observed, where the concentration of nucleation particles decreases and Aitken and accumulation mode increase, characterizing a typical particle growth process. In the late afternoon, when rain starts, PSD begin to have the night behaviour described above. Composite studies were computed to evaluate how the PSD evolve during rainfall events. The composite from lighting density shows a large increase in nucleation particles from around 100 minutes before the maximum lighting density, reaching maximum values nearly 200 minutes later. The nucleation particles growth rate increases exponentially with the thunderstorm intensity. Aitken and accumulation modes have a different behaviour, with decreasing number concentration from around 100 minutes before the maximum lighting activity and reaching the minimum concentration at the time of maximum lighting activity. This effect could be related to the more intense downdraft in thunderstorms that intensify the transport of ultrafine particles from the upper atmosphere as described in recent studies using GoAmazon and ACRIDICON-CHUVA data. Another possibility could be the transport of O3 and NO2 column densities during thunderstorms events, helping the oxidation of volatile organic component forming secondary organic aerosol at the surface. This is an open question and needs further studies specifically designed to understand the chemical processes occurring near-surface during intense rainfall events. The first data from the radar wind profile installed at the ATTO-Campina site was employed to compute the vertical distribution of the vertical velocity. The downdrafts are mainly located below 10km, but the layer of maximum concentration of ultrafine particles is mainly above 10km. In addition, the number concentration of nucleation particles at 60m is around twice the value at 325 m, in contrast to former studies showing an increase in ultrafine particles with height. CAFE-Brazil, scheduled for 2022, will be an opportunity to study these open questions.

How to cite: T. Machado, L. A., Pöhlker, M., Artaxo, P., Cecchini, M., Ditas, F., M. Franco, M. A., Kremper, L., Andreae, M. O., Saraiva, I., Pöschl, U., and Pöhlker, C.: How Weather Events Modify Amazonian Surface Aerosol Particle Size Distributions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11283, https://doi.org/10.5194/egusphere-egu21-11283, 2021.

EGU21-12971 | vPICO presentations | BG2

Influence of Atmospheric Stability on the flow dynamics within and above a dense Amazonian forest

Luca Mortarini, Cléo Quaresma Dias-Júnior, Otavio Acevedo, Pablo Oliveira, Daiane Brondani, Umberto Giostra, Matthias Sörgel, Anywhere Tsokankunku, Alessandro Araújo, Luiz Augusto Toledo Machado, and Daniela Cava

This study provides a detailed analysis of the influence of atmospheric stratification on the flow dynamics above and within a dense forest for a 19-days campaign at the Amazon Tall Tower Observatory (ATTO) site. Observations taken at seven levels within and above the forest along an 81-meter and a 325-meter towers allow a unique investigation of the vertical evolution of the turbulent field in the roughness sublayer and in the surface layer above it.

Five different stability classes were defined on the basis of the behavior of turbulent heat, momentum and CO2 fluxes and variance ratio as a function of h/L stability parameter (where h is the canopy height and L is the Obukhov length). The novelty is the identification of a ‘super-stable’ (SS) regime (h/L>3) characterized by extremely low wind speeds, the almost completely suppression of turbulence and a clear dominance of submeso motions both above and within the forest.

The obtained data classification was used to study the influence of atmospheric stratification on the vertical profiles of turbulent statistics. The spectral characteristics of coherent structures and of submeso motions (that may influence the energy and mass exchange above the Amazon forest) have been analyzed by wavelet analyses. The role of the main structures in momentum, heat and CO2 transport at the different levels inside and above the forest and in different diabatic conditions was thoroughly investigated through multiresolution and quadrant analyses.

In unstable and neutral stability, the flow above the canopy appears modulated by ejections, whereas downward and intermittent sweeps dominate the transport inside the canopy. In the roughness sublayer (z £ 2h) the coherent structures dominating the transport within and above the canopy have a characteristic temporal scale of about 100 sec, whereas above this layer the transport is mainly driven by larger scale convection (temporal scale of about 15 min).

In stable conditions the height of roughness sublayer progressively decreases with increasing stability reaching the minimum value (z<1.35h) in the SS regime. Above the canopy the flow is clearly dominated by ejections but characterized by a higher intermittency mainly in SS conditions. On the other hand, the rapid shear stress absorption in the highest part of the vegetation produces a less clear dominance of sweeps and a less defined role of odd and even quadrants inside the canopy in the transport of momentum, heat and CO2. In the weakly stable regime (0.15<h/L<1) transport is dominated in the roughness sublayer by canopy coherent structures with a characteristic temporal scale of about 60 sec. As stability increases the influence of low-frequency (submeso) processes, with a temporal scale of 20-30 min, on flow dynamics progressively increases and becomes dominant in the SS regime where the buoyancy strongly dampens or completely inhibits turbulent structures whereas the large-scale oscillations propagate in the interior of the canopy modulating the heat and CO2 transport.

 

How to cite: Mortarini, L., Quaresma Dias-Júnior, C., Acevedo, O., Oliveira, P., Brondani, D., Giostra, U., Sörgel, M., Tsokankunku, A., Araújo, A., Toledo Machado, L. A., and Cava, D.: Influence of Atmospheric Stability on the flow dynamics within and above a dense Amazonian forest, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12971, https://doi.org/10.5194/egusphere-egu21-12971, 2021.

EGU21-961 | vPICO presentations | BG2

River Breezes in the Central Amazon: Cluster Analysis of Meteorological and Chemical Data Sets Collected by an Unmanned Aerial Vehicle

Tianning Zhao, Jianhuai Ye, Igor Ribeiro, Yongjing Ma, Hui-Ming Hung, Carla Batista, Matthew Stewart, Jessica dos Santos Silva, Ricardo Godoi, Jordi Vilà-Guerau de Arellano, Rodrigo de Souza, and Scot Martin

Local atmospheric circulation induced by wide rivers in Amazonia can strongly affect the transport of urban, industrial, fire, and forest emissions. Herein, a copter-type unmanned aerial vehicle (UAV) operated from a boat was used to collect vertical profiles of meteorological parameters and chemical concentrations during Sep-Oct 2019 of the dry season. Sensor packages mounted on the UAV measured wind speed and direction together with concentrations of carbon monoxide (CO) and total oxidants (Ox, defined as O3 + NO2). Multivariate statistical analysis identified distinguishing patterns for meteorological variables. The occurrence of river breeze circulations was linked to meteorological conditions from in-situ measurement and satellite images. Vertical profiles of chemical concentrations both from in-situ measurements and large eddy simulations confirmed that under some conditions a river breeze can facilitate pollutant mixing perpendicular to the river orientation. The results of this study advance an urgent need to quantify the occurrence and the properties of river breeze circulations in respect to microscale chemical dispersion, air quality, and human health.

How to cite: Zhao, T., Ye, J., Ribeiro, I., Ma, Y., Hung, H.-M., Batista, C., Stewart, M., dos Santos Silva, J., Godoi, R., Vilà-Guerau de Arellano, J., de Souza, R., and Martin, S.: River Breezes in the Central Amazon: Cluster Analysis of Meteorological and Chemical Data Sets Collected by an Unmanned Aerial Vehicle, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-961, https://doi.org/10.5194/egusphere-egu21-961, 2021.

EGU21-12869 | vPICO presentations | BG2

Understanding in and above canopy-atmosphere interactions by combining large-eddy simulations with a comprehensive observational set

Xabier Pedruzo-Bagazgoitia, Arnold F. Moene, Huug Ouwersloot, Tobias Gerken, Luiz A.T. Machado, Scot T. Martin, Edward G. Patton, Matthias Sörgel, Paul C. Stoy, Marcia A. Yamasoe, and Jordi Vilà-Guerau de Arellano

The vegetated canopy plays a key role in regulating the surface fluxes and, therefore, the global energy, water and carbon cycles. In particular, vulnerable ecosystems like the Amazonia basin can be very sensitive to changes in vegetation that exert subsequent shifts in the partition of the energy, water and carbon in and above the canopy. Despite this relevance, most 3D atmospheric models represent the vegetated canopy as a flat 2D layer with, at most, a rough imitation of its effect in the atmospheric boundary layer through a modified roughness length. Thus, the representations often describe quite crudely the surface fluxes. In this work, particular emphasis is placed in the biophysical processes that take place within the canopy and its impact above. Our approach is to represent the coupling of the flow between the canopy and the atmosphere including the following processes: radiative transfer, photosynthesis, soil evaporation and CO2 respiration, combined with the mostly explicit atmospheric turbulence within and above the canopy. To this end, we implemented in LES a detailed multi-layer canopy model that solves the leaf energy balance for sunlit and shaded leaves independently, regulating the exchange of heat, moisture and carbon between the leaves and the air around. This allows us to connect the mechanistically represented processes occurring at the leaf level and strongly regulated by the transfer of diffuse and direct radiation within the canopy to the turbulent mixing explicitly resolved at the meter scale.

We test and validate this combined photosynthesis-turbulence-canopy model by simulating a representative clear day transitioning to shallow cumulus. We based our evaluation on observations by the GoAmazon2014/5 campaign in Brazil in 2014. More specifically, we systematically validate the in-canopy radiation profiles; sources, sinks and turbulent fluxes of moisture, heat and CO2, and main state variables within the canopy, and also study the effects of these in the air above. Preliminary results show an encouraging satisfactory match to the observed evolution of the profiles. As a first exploration and demonstration of the capabilities of the model, we test the effects of a coarser in-canopy resolution, a different radiation scheme and the use of a more simple 2D canopy representation.

How to cite: Pedruzo-Bagazgoitia, X., Moene, A. F., Ouwersloot, H., Gerken, T., Machado, L. A. T., Martin, S. T., Patton, E. G., Sörgel, M., Stoy, P. C., Yamasoe, M. A., and Vilà-Guerau de Arellano, J.: Understanding in and above canopy-atmosphere interactions by combining large-eddy simulations with a comprehensive observational set, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12869, https://doi.org/10.5194/egusphere-egu21-12869, 2021.

EGU21-15847 | vPICO presentations | BG2

The Amazonian Low-Level Jet and its effect on Ozone concentrations above the rain forest

Stefan Wolff, David Walter, Anywhere Tsokankunku, Daiane Brondani, Fernando Rossato, Sam Jones, Sebastian Brill, Eva Pfannerstill, Achim Edtbauer, Rodrigo Souza, Marta de Oliveira Sá, Alessandro C. de Araújo, Cléo Q. Dias-Júnior, Christopher Pöhlker, and Matthias Sörgel

The pristine Amazon rainforest is a unique place to study ozone (O3) deposition rates and tropospheric transport, due to the absence of nearby sources of anthropogenic pollution. Parts of the low background O3 are considered to be transported from the stratosphere into the troposphere. This occurs due to general entrainment of stratospheric air at the tropopause. Within the troposphere, downdrafts provide effective vertical mixing and are known to increase surface O3 values. Low-level jets can also enhance O3 concentrations due to long range transport and locally induced mixing in the nocturnal boundary layer. Therefore, we study these phenomena based on long term datasets from 2012 to present from tall measurements towers (80 m and 325 m).

Ozone mixing ratios were measured at the ATTO site (Amazon Tall Tower Observatory) in the Central Amazon (02°08’38.8’’S, 58°59’59.5’’W) since 2012 at 8 different heights between 5 cm and 80 meters and additional measurements from 80 m up to 325 meters are running since 2017. From 2015 to 2017, 3-dimensional wind measurements have been performed in 150 meters height in 10 Hz sampling rate, showing evidences for the formation of a nocturnal low-level jet (LLJ), which leads to higher turbulent mixing inside the residual layer/ stable nocturnal layer. We were comparing the nocturnal LLJ with downdrafts of air due to strong thunderstorms which led to increases of O3 as well. We are analyzing these events regarding their in-canopy air exchange, their frequency and seasonality and comparing them with the effects of the nocturnal LLJ. As the data series comprises more than eight years of data we are also analyzing the interannual variability.

How to cite: Wolff, S., Walter, D., Tsokankunku, A., Brondani, D., Rossato, F., Jones, S., Brill, S., Pfannerstill, E., Edtbauer, A., Souza, R., de Oliveira Sá, M., de Araújo, A. C., Dias-Júnior, C. Q., Pöhlker, C., and Sörgel, M.: The Amazonian Low-Level Jet and its effect on Ozone concentrations above the rain forest, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15847, https://doi.org/10.5194/egusphere-egu21-15847, 2021.

EGU21-13468 | vPICO presentations | BG2 | Highlight

Tropical forest CH4: from termite mounds to tower  measurements

Hella van Asperen, Thorsten Warneke, Alessandro C De Araújo, Bruce Forsberg, Leonardo Ramos de Oliveira, Thiago de Lima Xavier, Marta Sá, Paulo Teixeira, Robson Azevedo de Oliveira, Leila Leal, Veber Moura, João Rafael Alves-Oliveira, Santiago Botia, Jost Lavrič, Shujiro Komiya, Arnoud Frumau, Arjan Hensen, Danielle van Dinther, Pim van den Bulk, 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, continous CH4 concentration and flux measurements are still rare.

The 50 m high K34 tower (field site ZF2) is located in a pristine ‘Terra Firme’ tropical forest region 60 km northwest of Manaus (Brazil), and is located next to a waterlogged valley, a possible location for anaerobic CH4 production. In October 2018, in addition to the existing EC CO2 system, an in-situ FTIR-analyzer (measuring CO2, CO, CH4, N2O and δ13CO2) was set up to measure tower profile concentrations, above and below the canopy, continuously. By analyses of vertical and temporal nighttime concentrations patterns, an emission estimate for all gases could be made, and an ecosystem emission of ~1 nmol CH4 m-2 s-1  was estimated. In addition, by use of different types of flux chambers, possible  CH4 sinks and sources such as soils, trees, water and termite mounds were measured.

By combining tower and flux chamber measurements, the role and magnitude of different ecosystem sources could be assessed. In this presentation, an overview of the measured CH4 forest concentrations and fluxes will be given.

How to cite: van Asperen, H., Warneke, T., C De Araújo, A., Forsberg, B., Ramos de Oliveira, L., de Lima Xavier, T., Sá, M., Teixeira, P., Azevedo de Oliveira, R., Leal, L., Moura, V., Rafael Alves-Oliveira, J., Botia, S., Lavrič, J., Komiya, S., Frumau, A., Hensen, A., van Dinther, D., van den Bulk, P., and Notholt, J.: Tropical forest CH4: from termite mounds to tower  measurements, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13468, https://doi.org/10.5194/egusphere-egu21-13468, 2021.

EGU21-831 | vPICO presentations | BG2

Spatial and temporal variability of soil N2O and CH4 fluxes along a degradation gradient in a palm swamp peat forest in the Peruvian Amazon

Kristell Hergoualc’h, Nelda Dezzeo, Louis Verchot, Christopher Martius, Jeffrey van Lent, Jhon Del Aguila Pasquel, and Mariela Lopez

Mauritia flexuosa palm swamp, the prevailing Peruvian Amazon peatland ecosystem, is

extensively threatened by degradation. The unsustainable practice of cutting whole

palms for fruit extraction modifies forest's structure and composition and eventually

alters peat-derived greenhouse gas (GHG) emissions. We evaluated the spatio-temporal

variability of soil N2O and CH4 fluxes and environmental controls along a palm swamp

degradation gradient formed by one undegraded site (Intact), one moderately degraded

site (mDeg) and one heavily degraded site (hDeg). Microscale variability differentiated

hummocks supporting live or cut palms from surrounding hollows. Macroscale analysis

considered structural changes in vegetation and soil microtopography as impacted

by degradation. Variables were monitored monthly over 3 years to evaluate intra- and

inter-annual variability. Degradation induced microscale changes in N2O and CH4 emission

trends and controls. Site-scale average annual CH4 emissions were similar along the

degradation gradient (225.6 ± 50.7, 160.5 ± 65.9 and 169.4 ± 20.7 kg C ha−1 year−1 at

the Intact, mDeg and hDeg sites, respectively). Site-scale average annual N2O emissions

(kg N ha−1 year−1) were lower at the mDeg site (0.5 ± 0.1) than at the Intact (1.3 ± 0.6) and

hDeg sites (1.1 ± 0.4), but the difference seemed linked to heterogeneous fluctuations

in soil water-filled pore space (WFPS) along the forest complex rather than to degradation.

Monthly and annual emissions were mainly controlled by variations in WFPS, water

table level (WT) and net nitrification for N2O; WT, air temperature and net nitrification

for CH4. Site-scale N2O emissions remained steady over years, whereas CH4 emissions

rose exponentially with increased precipitation. While the minor impact of degradation

on palm swamp peatland N2O and CH4 fluxes should be tested elsewhere, the evidenced

large and variable CH4 emissions and significant N2O emissions call for improved modeling

of GHG dynamics in tropical peatlands to test their response to climate changes.

How to cite: Hergoualc’h, K., Dezzeo, N., Verchot, L., Martius, C., van Lent, J., Del Aguila Pasquel, J., and Lopez, M.: Spatial and temporal variability of soil N2O and CH4 fluxes along a degradation gradient in a palm swamp peat forest in the Peruvian Amazon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-831, https://doi.org/10.5194/egusphere-egu21-831, 2021.

EGU21-13194 | vPICO presentations | BG2 | Highlight

Pyrogenic carbon and forest dynamics during drought in Amazonian forests

Laura Vedovato, Lidiany Carvalho, Luiz Aragão, and Ted Feldpausch

During extreme drought events, aboveground biomass (AGB) dynamics in Amazonian forests are altered through reduced productivity and increased tree mortality and carbon loss. Tree adaptations developed in response to historical drought may reduce the severity of carbon loss. Past droughts were likely associated with fire, which produced Pyrogenic Carbon (PyC), a form of carbon formed by the incomplete combustion of biomass burn and fossil fuel. PyC has specific properties that improve soil fertility and water holding capacity and decrease aluminium toxicity, among others. PyC can be found in different concentrations across the Amazon Basin, since it can be produced by local fires and aerosol deposition. It is unknown whether PyC could explain tree adaptations or contributes to Amazon forest dynamics, especially for extreme drought events. We hypothesize that PyC in soil can serve as a proxy of fire history and fire/drought adaptations and also support the forest during drought events because of its properties, decreasing mortality rates and maintaining rates of AGB gain equivalent to a non-extreme drought year. To evaluate this hypothesis, we used a dataset with more than 70 plots with repeat censuses distributed across the Amazon Basin and classified extreme drought events using maximum cumulative water deficit (MCWD) analysis. Soil samples were collected from the same plots during an intensive fieldwork campaign and PyC was quantified by hydrogen pyrolysis (HyPy). Forest plots were classified into high and low PyC based on the median across the whole dataset. Our preliminary results show that during extreme drought events, plots that have a greater concentration of PyC had significantly higher rates of AGB gain when compared with plots with lower concentrations of PyC (t-test, p < 0.05). During non-extreme drought years there was no significant difference in rates of AGB gain between plots with different concentrations of PyC. When we focus on plots with lower concentrations of PyC there is a significant decrease in rates of AGB gain during drought years compared to non-extreme drought years (t-test, p < 0.05). However, in plots with high concentrations of PyC there is no significant difference in rates of AGB gain, showing trees are able to maintain normal forest dynamics during extreme drought years. We conclude that PyC has an important role in mediating drought resistance and productivity in Amazonian forests.

How to cite: Vedovato, L., Carvalho, L., Aragão, L., and Feldpausch, T.: Pyrogenic carbon and forest dynamics during drought in Amazonian forests, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13194, https://doi.org/10.5194/egusphere-egu21-13194, 2021.

EGU21-7956 | vPICO presentations | BG2

Quantifying the spatial patterns of Secondary Forest carbon sequestration potential in the Brazilian Amazon

Viola Heinrich, Ricardo Dalagnol, Henrique Cassol, Thais Rosan, Catherine Torres de Almeida, Celso Silva Junior, Welsey Campanharo, Joanna House, Stephen Sitch, Tristram Hales, Marcos Adami, Liana Anderson, and Luiz Aragão

Overall, global forests are expected to contribute about a quarter of pledged mitigation under the Paris Agreement, by limiting deforestation and by encouraging forest regrowth.

Secondary Forests in the Neo-tropics have a large climate mitigation potential, given their ability to sequester carbon up to 20 times faster than old-growth forests. However, this rate does not account for the spatial patterns in secondary forest regrowth influenced by regional and local-scale environmental and anthropogenic disturbance drivers.

Secondary Forests in the Brazilian Amazon are expected to play a key role in achieving the goals of the Paris Agreement, however, the Amazon is a large and geographically complex region such that regrowth rates are not uniform across the biome.

To understand the impact of key drivers we used a multi-satellite data approach with the aim of understanding the spatial variations in secondary forest regrowth in the Brazilian Amazon. We mapped secondary forest area and age using a land-use-land-cover dataset – MapBiomas – and, combined with the European Space Agency Aboveground Carbon dataset, constructed regional regrowth curves for the year 2017.

We found large variations in the regrowth rates across the Brazilian Amazon due to large-scale environmental drivers such as rainfall and shortwave-radiation. Regrowth rates are similar to previous pan-Amazonian estimates in the North-West (3 ±1.0 MgC ha-1 yr-1), which are double than those in the North-East Amazon (1.3 ±0.3 MgC ha-1 yr-1). The impact of anthropogenic disturbances, namely fire and repeated deforestation prior to the most recent regrowth only reduces the regrowth by 20% in the North-West (2.4 ±0.8 MgC ha-1 yr-1) compared to 55% in the North-East (0.8 ±0.8 MgC ha-1 yr-1). Overall, secondary forest carbon stock of 294 TgC in the year 2017, could have been 8% higher with avoided fires and repeat deforestation. We found that the 2017 area of secondary forest, which occupies only ~4% of the Brazilian Amazon biome, can contribute significantly (~5.5%) to Brazil’s net emissions reduction targets, accumulating ~19.0 TgC yr-1until 2030 if the current area of secondary forest is maintained (13.8 Mha). However,this value reduces rapidly to less than 1% if only secondary forests older than 20 years are preserved (2.2 Mha).

Preserving the remaining old-growth forest carbon stock and implementing legal mechanisms to protect and expand secondary forest areas are key to realising the potential of secondary forest as a nature-based climate change mitigation solution.

How to cite: Heinrich, V., Dalagnol, R., Cassol, H., Rosan, T., Torres de Almeida, C., Silva Junior, C., Campanharo, W., House, J., Sitch, S., Hales, T., Adami, M., Anderson, L., and Aragão, L.: Quantifying the spatial patterns of Secondary Forest carbon sequestration potential in the Brazilian Amazon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7956, https://doi.org/10.5194/egusphere-egu21-7956, 2021.

EGU21-14109 | vPICO presentations | BG2

Analysis of bioaerosol emission patterns of tropical fungi in the Amazon region

Sebastian Brill, Nina Löbs, Cybelli G. G. Barbosa, Juliana F. de Camargo, David Walter, Florian Ditas, Marta de Oliveira Sá, Alessandro C. de Araújo, Leonardo R. de Oliveira, Ricardo H. M. Godoi, Stefan Wolff, Meike Piepenbring, Jürgen Kesselmeier, Paulo Artaxo, Meinrat O. Andreae, Ulrich Pöschl, Christopher Pöhlker, and Bettina Weber

Primary biological aerosol particles (PBAP), better known as bioaerosols, are considered to play a role in atmospheric and climate influencing processes. Fungal spores, as a part of PBAP, account for a large fraction of coarse particulate matter in some ecosystems, as for example the Amazon rainforest. In such highly diverse ecosystems, fungi play key roles as mycorrhizal fungi for nutrient uptake of plants and as decomposers in nutrient and water cycling, and thus their community structure strongly influences local ecosystem conditions. Despite this relevance, fungal spore emission patterns under natural conditions and the corresponding triggering factors are not well characterized, yet. In this study, we present a laboratory and field measurement techniques to quantify and analyze bioaerosol emission patterns and the effect of precipitation on fungal spore emission.

For investigations under field conditions, the particle emissions of fungi (Agaricomycetes) were characterized at their site of growth in the field using an optical particle sizer and a data logger. Particle concentrations and their size distribution (0.3 to 10 µm), as well as the microclimatic temperature and humidity were measured in close vicinity to the fungal fruiting body. Generally, field measurements were performed over a time span of 24 h with some exceptions ranging up to 6 days. For laboratory measurements, a newly developed glass chamber system was used to measure particle emissions of fungi under controlled conditions. During the chamber measurements, the humidity and temperature conditions were varied and recorded with a datalogger. To simulate precipitation events, the fruiting bodies were sprayed with water between measurement sections and particle emissions were monitored before and after moistening.

First measurements of fungi under field and lab conditions showed that high humidity values were necessary to trigger fungal spore emissions. In many cases, precipitation events and the moisture status of the fungus and substrate had an influence on spore release. Based on the results of 47 field measurements, it was possible to establish a function simulating the spore emission patterns of fungi during their diurnal emission cycle. During field measurements, an emission of up to 55,000 spores per second was recorded directly at the fungus, which, according to the function, may correspond to emissions of up to 2.8 x 109 spores per day. Chamber measurements showed that spore emissions generally started 2-3 hours after artificial moistening.

Increasing deforestation is expected to cause drier conditions and to increase the possibility of droughts, which will have an impact on the species composition and quantity of fungi in the Amazon. A combination of our field and lab emission data is expected to allow a new interpretation of bioaerosol emissions and composition in the Amazon, which can be used as a baseline to analyze the potential relevance of bioaerosols in regional atmosphere and climate processes.

How to cite: Brill, S., Löbs, N., Barbosa, C. G. G., de Camargo, J. F., Walter, D., Ditas, F., de Oliveira Sá, M., de Araújo, A. C., de Oliveira, L. R., Godoi, R. H. M., Wolff, S., Piepenbring, M., Kesselmeier, J., Artaxo, P., Andreae, M. O., Pöschl, U., Pöhlker, C., and Weber, B.: Analysis of bioaerosol emission patterns of tropical fungi in the Amazon region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14109, https://doi.org/10.5194/egusphere-egu21-14109, 2021.

EGU21-8739 | vPICO presentations | BG2

Beta effect of eCO2 can cause as much rainfall decrease as large-scale deforestation in the Amazon

David Lapola, Gilvan Sampaio, Marília Shimizu, Carlos Guimarães-Júnior, Felipe Alexandre, Manoel Cardoso, Tomas Domingues, Anja Rammig, Celso von Randow, and Luiz Rezende

Amazon region’s climate is particularly sensitive to surface processes and properties such as heat fluxes and vegetation coverage. Rainfall is a key expression of such land surface-atmosphere interactions in the region due to its strong dependence on forest transpiration. While a large number of past studies have shown the impacts of large-scale deforestation on annual rainfall, studies on the isolated effects of elevated atmospheric CO2 concentration (eCO2) on plant physiology (i.e. the β effect), for example on canopy transpiration and rainfall, are scarcer. Here we make a systematic comparison of the plant physiological effects of eCO2 and deforestation on Amazon rainfall. We use the CPTEC-Brazilian Atmospheric Model (BAM) with dynamic vegetation under a 1.5xCO2 and a 100% substitution of the forest by pasture grassland, with all other conditions held similar between the two scenarios. We find that both scenarios result in equivalent average annual rainfall reductions (Physiology: -252 mm,-12%; Deforestation: -292 mm, -13%) that are well above observed Amazon rainfall interannual variability of 5.1%. Rainfall decrease in the two scenarios are caused by a reduction of approximately 20% of canopy transpiration, but for different reasons: eCO2-driven reduction of stomatal conductance in the Physiology run; decreased leaf area index of pasture (-66%) and its dry-season lower surface vegetation coverage in the Deforestation run. Walker circulation is strengthened in the two scenarios (with enhanced convection over the Andes and a weak subsidence branch over east Amazon) but, again, through different mechanisms: enhanced west winds from the Pacific and reduced easterlies entering the basin in Physiology, and strongly increased easterlies in Deforestation. Although our results for the Deforestation scenario are in agreement with previous observational and modelling studies, the lack of direct field-based ecosystem-level experimental evidence on the effect of eCO2 in moisture fluxes of tropical forests confers a substantial level of uncertainty to this and any other projections on the physiological effect of eCO2 on Amazon rainfall. Furthermore, our results denote the incurred responsibilities of both Amazonian and non- Amazonian countries to mitigate potential future climatic change and its impacts in the region driven either by local deforestation (to be tackled by Amazonian countries) or global CO2 emissions (to be handled by all countries).

How to cite: Lapola, D., Sampaio, G., Shimizu, M., Guimarães-Júnior, C., Alexandre, F., Cardoso, M., Domingues, T., Rammig, A., von Randow, C., and Rezende, L.: Beta effect of eCO2 can cause as much rainfall decrease as large-scale deforestation in the Amazon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8739, https://doi.org/10.5194/egusphere-egu21-8739, 2021.

EGU21-8937 | vPICO presentations | BG2

Analysis of determinants of forest - savanna transition in the northern South America

Santiago Valencia, Juan Camilo Villegas, and Juan F. Salazar

Forest - savanna transition is the most widespread and perhaps more dynamic ecotone in the tropics, and extremely sensitive to climate and environmental change. Both kinds of tropical ecosystems are globally strategic and their presence and dynamics have important ecological, climatic and biogeochemical implications, even at the global scale. However, the processes and mechanisms that control this transition vary among regions and remain not fully understood. In general, this transition is influenced by multiple interactions between vegetation and environmental factors such as climate, soil properties, fire, and herbivory. However, the magnitude of these effects can vary substantially across continents, which can result in different responses to environmental change. For this reason, more regional studies are needed to describe and understand the factors and interactions that control forest - savanna transition, particularly in Northern South America, where climate alone has failed to explain this transition. Based on a combination of LiDAR and satellite-derived data, we developed a statistical analysis on the interactive effects of rainfall, soil properties, and fire on the forest - savanna transition in Northern South America, in the savanna region between Colombia and Venezuela, using tree cover as an indicator variable that differentiates forest from savanna. Specifically, we analyze the relationships of tree cover (from GEDI) with soil sand content (from SoilGrids), fire frequency (from Fire_CCI v5.1) as well as three rainfall variability components (from CHIRPS): mean dry-season rainfall, length of the dry season, and frequency of rainy days within the dry season. Our results show that tree cover increased with mean dry-season rainfall and frequency of rainy days within the dry season, whereas it decreased with increased fire frequency. In particular, mean dry-season rainfall followed by fire frequency are the most important predictors of tree cover gradient in the transition. Importantly, our results also suggest that areas with high annual rainfall (2000 to 2800 mm) have low tree cover (i.e. savanna) if the local rainfall climatology consists of infrequent (< 0.35) and low total rainfall (< 650 mm) in the dry season. This highlights the role of water availability and fire disturbance in determining the limits between forest and the second largest area of savanna in South America. Further, our results support that future projections for forest - savanna transition should include not only changes in mean annual rainfall but also changes in rainfall variability, which is expected to be more impacted by climate change. 

How to cite: Valencia, S., Villegas, J. C., and Salazar, J. F.: Analysis of determinants of forest - savanna transition in the northern South America, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8937, https://doi.org/10.5194/egusphere-egu21-8937, 2021.

EGU21-4121 | vPICO presentations | BG2

Soil organic carbon stocks under different páramo vegetation covers in Ecuador’s northern Andes

Marlon Calispa, Raphaël van Ypersele, Benoît Pereira, Sebastián Páez-Bimos, Veerle Vanacker, Marcos Villacís, Armando Molina, Bert de Bièvre, Teresa Muñoz, and Pierre Delmelle

The Ecuadorian páramo, a neotropical ecosystem located in the upper Andes, acts as a constant source of high-quality water. It also stores significant amounts of C at the regional scale. In this region, volcanic ash soils sustain most of the paramo, and C storage results partly from their propensity to accumulate organic matter. Vegetation type is known to influence the balance between plant C inputs and soil C losses, ultimately affecting the soil organic C (SOC) content and stock. Tussock-forming grass (spp. Calamagrostis Intermedia; TU), cushion-like plants (spp. Azorella pedunculata; CU) and shrubs and trees (Polylepis stands) are commonly found in the páramo. Our understanding of SOC stocks and dynamics in the páramo remains limited, despite mounting concerns that human activities are increasingly affecting vegetation and potentially, the capacity of these ecosystems to store C.

Here, we compare the organic C content and stock in soils under tussock-forming grass (spp. Calamagrostis Intermedia; TU) and soils under cushion-like plants (spp. Azorella pedunculata; CU). The study took place at Jatunhuayco, a watershed on the western slopes of Antisana volcano in the northern Ecuadorian Andes. Two areas of similar size (~0.35 km2) were surveyed. Fourty soil samples were collected randomly in each area to depths varying from 10 to 30 cm (A horizon) and from 30 to 75 cm (2Ab horizon). The soils are Vitric Andosols and the 2Ab horizon corresponds to a soil buried by the tephra fall from the Quilotoa eruption about 800 yr. BP. Sixteen intact soil samples were collected in Kopecky's cylinders for bulk density (BD) determination of each horizon.

The average SOC content in the A horizon of the CU sites (9.4±0.5%) is significantly higher (Mann-Whitney U test, p<0.05) than that of the TU sites (8.0±0.4%), probably reflecting a larger input of root biomass from the cushion-forming plants. The 2Ab horizon contains less organic C (i.e. TU: 4.3±0.3% and CU: 4.0±0.4%) than the A horizon, but the SOC contents are undistinguishable between the two vegetation types. This suggests that the influence of vegetation type on SOC is limited to the A horizon. The average SOC stocks (in the first 30 cm from the soil) for TU and CU are 20.04±1.1 and 18.23±1.0 kg/m2,respectively. These values are almost two times greater than the global average reported for Vitric Andosols (~8.2 kg/m2 ), but are lower than the estimates obtained for some wetter Andean páramos (22.5±5 kg/m2, 270% higher rainfall) from Ecuador. Our stock values further indicate that vegetation type has a limited effect on C storage in the young volcanic ash soils found at Jatunhuyaco. Despite a higher SOC content, the CU soils store a stock of organic C similar to that estimated for the TU soils. This likely reflects the comparatively lower BD of the former soils (650±100 vs. 840±30 kg/m3). Additional studies are needed in order to establish the vegetation-related factors driving the SOC content and stability in the TU and CU soils.

How to cite: Calispa, M., van Ypersele, R., Pereira, B., Páez-Bimos, S., Vanacker, V., Villacís, M., Molina, A., de Bièvre, B., Muñoz, T., and Delmelle, P.: Soil organic carbon stocks under different páramo vegetation covers in Ecuador’s northern Andes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4121, https://doi.org/10.5194/egusphere-egu21-4121, 2021.

EGU21-13301 | vPICO presentations | BG2

Meteorological and fire impacts on tropospheric ozone concentration over tropical forest in the Congo Basin

Inês Vieira, Hans Verbeeck, Félicien Meunier, Marc Peaucelle, Lodewijk Lefevre, Alexander Cheesman, Stephen Sitch, José Mbifo, Pascal Boeckx, and Marijn Bauters

Tropospheric ozone is a greenhouse gas, and high tropospheric ozone levels can directly impact plant growth and human health. In the Congo basin, simulations predict high ozone concentrations, induced by high ozone precursor (VOC and NOx) concentrations and high solar irradiation, which trigger the chemical reactions that form ozone. Additionally, biomass burning activities are widespread on the African continent, playing a crucial role in ozone precursor production. How these potentially high ozone levels impact tropical forest primary productivity remains poorly understood, and field-based ozone monitoring is completely lacking from the Congo basin. This study intends to show preliminary results from the first full year of in situ measurements of ozone concentration in the Congo Basin (i.e., Yangambi, Democratic Republic of the Congo). We show the relationships between meteorological variables (temperature, precipitation, radiation, wind direction and speed), fire occurrence (derived from remote sensing products) and ozone concentrations at a new continuous monitoring station in the heart of the Congo Basin. First results show higher daily mean ozone levels (e.g. 43 ppb registered in January 2020) during dry season months (December-February). We identify a strong diurnal cycle, where minimum values of ozone (almost near zero) are registered during night hours, and maximum values (near 100 ppb) are registered during the daytime. We also verify that around 2.5% of the ozone measurements exceeds a toxicity level (potential for ozone to damage vegetation) of 40 ppb. In the longer term, these measurements should improve the accuracy of future model simulations in the Congo Basin and will be used to assess the impact of ozone on the tropical forest’s primary productivity.

How to cite: Vieira, I., Verbeeck, H., Meunier, F., Peaucelle, M., Lefevre, L., Cheesman, A., Sitch, S., Mbifo, J., Boeckx, P., and Bauters, M.: Meteorological and fire impacts on tropospheric ozone concentration over tropical forest in the Congo Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13301, https://doi.org/10.5194/egusphere-egu21-13301, 2021.

EGU21-7704 | vPICO presentations | BG2

Greenhouse gas fluxes from an oil palm plantation on mineral soil in Indonesia undergoing riparian restoration 

Stella White, Ribka Sionita Tarigan, Anak Agung Ketut Aryawan, Edgar Turner, Sarah Luke, Pujianto Pujianto, Jean-Pierre Caliman, and Julia Drewer

Oil palm (OP) growers are under pressure to reduce their environmental impact. Ecosystem function and biodiversity are at the forefront of the issue, but what effect do changes in management practices have on greenhouse gas (GHG) fluxes from plantations? 

The Riparian Ecosystem Restoration in Tropical Agriculture (RERTA) Project is a collaboration between the University of Cambridge and the SMART Research Institute in Riau, Indonesia. This project explores the ecological changes resulting from the restoration of riparian margins between plantations and watercourses. Four management strategies were applied on both sides of a river to create 50m riparian buffers, 400m in length: (1) A control treatment of no restoration, the removal of mature OP and replanting of young OP to the river margin; (2) Little to no agricultural management of mature OP; (3) Clearance of mature OP and enrichment planting with native forest trees; (4) Little or no agricultural management of mature OP and enrichment planting with native forest trees. Here we present a specific objective to investigate the effect of riparian restoration – and related changes in soil characteristics, structure and vegetation cover – on fluxes of N2O, CH4 and CO2 from mineral soils.

The experimental site began as a mature OP plantation, with monthly background measurements taken between January and April 2019. Palms were felled in April 2019 and monthly sampling was resumed when replanting and restoration began, in October 2019. We measured GHGs using static chambers; 6 in each riparian treatment and 16 in the actual OP plantation, 40 chambers in total. Samples were analysed using GC-FID/µECD.

Background measurements before felling showed high variability, but indicated no difference between the four experimental plots and the rest of the plantation. Fluxes measured following replanting were also highly variable, with no significant differences observed between treatments. N2O fluxes were relatively low before felling as the mature palms were no longer fertilised. Higher emissions were seen in the disturbed immature OP and forest tree treatments following replanting. Though the sites appeared to recover quickly and emission fluxes decreased after a few months, presumably as the soil settled and new vegetation began to grow. CH4 uptake was seen in the immature OP treatment immediately after replanting. In subsequent months no clear trends of CH4 uptake or emission were observed, with the greatest variability generally seen in the forest tree treatment. CH4 emissions increased in October 2020 with the beginning of the rainy season, most notably in mature OP and mature OP with forest tree treatments. Following restoration CO2 emissions were higher in treatments with established plant communities – mature OP and mature OP with forest trees.

These results suggest that riparian restoration had no significant effect on GHG fluxes from mineral soils, and would not alter the overall GHG budget of a plantation. If there is no additional GHG burden and riparian restoration results in enhancing biodiversity and ecosystem services as well as improving water quality, it will be a viable management option to improve the environmental impact of an OP plantation.

How to cite: White, S., Sionita Tarigan, R., Ketut Aryawan, A. A., Turner, E., Luke, S., Pujianto, P., Caliman, J.-P., and Drewer, J.: Greenhouse gas fluxes from an oil palm plantation on mineral soil in Indonesia undergoing riparian restoration , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7704, https://doi.org/10.5194/egusphere-egu21-7704, 2021.

EGU21-15996 | vPICO presentations | BG2 | Highlight

Refined past, current and future greenhouse gas footprints of palm oil production

Ana Meijide, Cristina de la Rúa, Martin Ehbrecht, and Alexander Röll

Oil palm (Elaeis guineensis) is the most important oil crop in the world, with more than 85% of the global production coming from Indonesia and Malaysia. However, knowledge of country-wide past, current and likely future greenhouse gas (GHG) footprints from palm oil production remains largely incomplete. Over the past year, first studies reporting measurements of net ecosystem carbon dioxide (CO2) fluxes in oil palm plantations of different ages and on different soil types became available. Combining the recent CO2 flux estimates with existing measurements on methane and nitrous oxide fluxes allows for a refined quantification of the GHG footprint of palm oil production over the whole plantation life cycle.

To derive country-wide GHG emissions from palm oil production for both Indonesia and Malaysia, we applied the refined GHG footprint estimates to oil palm area extents. Therein, we differentiated between mineral and peat soils, second- and first-generation plantations and within the latter category also among previous land-use systems from which conversion to oil palm likely occurred. For deriving the current (2020) proportions for each category, we combined FAO data with existing remotely sensed maps on oil palm extent and tree density as well as peatland and intact forest layers. These area proportions were then applied to available historic (1970 – 2010) and future (2030 – 2050) oil palm extent estimates as a business-as-usual scenario (BAU), complemented by alternative scenarios. GHG footprint estimates comprise all GHG emissions from palm oil production, i.e. from land-use change, cultivation, milling and use.

Our refined approach estimates the 2020 GHG emissions from palm oil production at 1011 Tg CO2-eq. yr-1 for Indonesia and at 261 Tg CO2-eq. yr-1 for Malaysia. Our results show that while plantations on peatland only represented 17% and 15% of the total plantation area in 2020 for Indonesia and Malaysia, they accounted for 73% and 72% of the total GHG emissions from palm oil production. Emissions in 1980 and 2000 were estimated to be only 1% and 14% of the 2020 palm oil emissions for Indonesia, but already 24% and 96% for Malaysia due to the earlier oil palm expansion. Projected emissions for 2050, assuming further oil palm expansion on suitable land and constant yields from 2020 on, represent 64% of the 2020 value for Indonesia and 97% for Malaysia under a BAU expansion scenario. These lower or constant GHG emissions for future scenarios despite assumed increases in cultivated area are the consequence of lower GHG emissions in second and subsequent rotation cycles. For both countries, the 2050 BAU emissions could be reduced by more than 50% by halting all conversion of peatlands and forests to oil palm from 2020 on, and by more than 75% when additionally restoring all peatlands currently under oil palm to forest until 2050. Closing yield gaps could potentially lead to further emissions savings.   

How to cite: Meijide, A., de la Rúa, C., Ehbrecht, M., and Röll, A.: Refined past, current and future greenhouse gas footprints of palm oil production, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15996, https://doi.org/10.5194/egusphere-egu21-15996, 2021.

EGU21-10765 | vPICO presentations | BG2

Using Airborne Laser Scanning to characterize different land uses in a tropical landscape based on their structural complexity

Nicoló Camarretta, Martin Ehbrecht, Arne Wenzel, Mohd Zuhdi, Miryam S. Merk, Michael Schlund, Alexander Knohl, and Stefan Erasmi

Accurate characterization of land use and land cover (LULC) is important in a rapidly changing environment such as the Indonesian tropics. Over the past 30 years, native tropical forests have been cleared and replaced by fast-growing cash-crops, such as oil palm and rubber plantations. This change in land use dramatically alters the vegetation structure of the entire region. Vegetation structural complexity is highly variable in tropical forests, and provides habitat to a large number of native species. In addition, vegetation structure has an impact on micro-climate and the exchange of greenhouse gases (GHG), water and energy. Measuring vegetation structure in the field can be costly and time consuming, particularly in remote, inaccessible areas of tropical forest. In contrast, Airborne Laser Scanning (ALS) can provide very detailed three-dimensional information on forest structure without the need to reach remote areas in the field. Here, we aim to study the potential of ALS-derived measures of structural complexity as ecological indicators to highlight differences in forest structure across a gradient of LULC in Sumatra, Indonesia. We analysed the structural complexity of four main LULC types relevant to the region: tropical secondary forests, rubber agroforests, oil palm plantations and shrublands. Several structural metrics have been extracted from ALS data over 136 circular 0.1 ha plots (34 plots per LULC type): top height, height percentiles, rumple index, leaf area index (LAI), effective number of layers (ENL), vegetation cover, number of gaps. Results from a Principal Component Analysis (PCA) indicated number of gaps to be a major driver associated with the occurrence of oil palm plantations, while higher values of key structural metrics, such as top height, LAI and ENL were strongly linked with the presence of secondary tropical forest plots. Furthermore, a clear separation in metrics behaviour between forest and oil palm plots was evident from the pairwise comparison of these metrics, with rubber and shrubland plots behaving similarly to either forests or oil palm plantings according to different metrics. Our results show clear distinctions in several structural attributes among different LULC, which indicate the need for careful considerations regarding the impact of land-use change on ecosystem functioning, biodiversity and climate.

How to cite: Camarretta, N., Ehbrecht, M., Wenzel, A., Zuhdi, M., Merk, M. S., Schlund, M., Knohl, A., and Erasmi, S.: Using Airborne Laser Scanning to characterize different land uses in a tropical landscape based on their structural complexity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10765, https://doi.org/10.5194/egusphere-egu21-10765, 2021.

EGU21-11776 | vPICO presentations | BG2

Agriculture effects on geochemical soil properties and stability of soil organic carbon on tropical Andosols

Sastrika Anindita, Steven Sleutel, and Peter Finke

The impact of soil age on geochemical properties and carbon cycling has been studied via chronosequences. However, only few studies have addressed how land-use and soil age might interactively shape properties of Andosols and in turn their capability to retain organic carbon (OC). Geochemical soil analyses and laboratory incubation experiments were carried out to assess soil characteristics and mineralization of soil organic carbon (SOC) in Indonesian soils with two contrasting land uses, viz. pine forest and horticulture. Both of these land uses are the results of conversion of primary forest which had similar parent materials, soil age, as well as weathering intensity. Results showed that intensive agricultural practices (+ 40-50 years) did not result in a significant loss of SOC or the increase of bulk density compared to forest. On the other hand, they were found to increase pH, exchangeable cations, base saturation, and most strikingly non-crystalline materials (i.e. Alo + ½ Feo) leading to phenotype formation in agricultural soils. Positive correlations were found between non-crystalline materials with properties such as soil specific surface area and micropores volume, and it was also positively correlated with SOC, particularly in the subsoil. This study highlighted the resilience of Andosols to soil degradation under agricultural practices and its ability to stabilize SOC.

How to cite: Anindita, S., Sleutel, S., and Finke, P.: Agriculture effects on geochemical soil properties and stability of soil organic carbon on tropical Andosols, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11776, https://doi.org/10.5194/egusphere-egu21-11776, 2021.

EGU21-8240 | vPICO presentations | BG2

Reuse of Pineapple Residue in Philippine Agriculture: determination of the net ecosystem C balance for a CAM plant in a pot-scale experiment

Reena Macagga, Shrijana Vaidya, Danica Antonijevic, Marten Schmidt, Matthias Lueck, Mihály Jancsó, Juergen Augustin, Pearl Sanchez, and Mathias Hoffmann

The Philippines is one of the world’s leading producers of pineapples, wherein production is comprised mostly of small family farms that are less than 2 hectares in size. As by-product, they generate a large amount of plant residues (e.g., crowns and stems) that are commonly left at the edge of the field. This practice releases substantial amount of greenhouse gas (GHG) emissions and neglects the potential value of pineapple residue. Enabling a waste treatment by returning them to the field through incorporation or mulching holds the potential to maintain soil fertility, reduce climate impact, secure yield stability, and achieving a high resource efficiency by closing material cycles locally. It may also increase soil organic carbon stock (SOC) and reduce greenhouse gas (GHG) emissions. To date, however, the knowledge about this is still very sparse.

The rePRISING project aims to demonstrate that returning pineapple residue either through mulching or incorporation to the field may help promote the closing of nutrient-cycles (C/N/P/K) locally, thus helping to increase soil fertility and soil C sequestration, while reducing GHG emissions. Within the project, the recycling of pineapple residue together with various local organic and inorganic amendments will be studied during a two-year field experiment using the manual closed chamber method. The field study will be supplemented by pot-scale greenhouse and incubation experiments, used inter alia to determine baseline GHG emissions and carbon budgets of pineapple cultivation systems and residue treatments.

Here we present first results of a pot experiment performed during winter 2020-2021 used to develop a suitable procedure for the in-situ determination of dynamic net ecosystem C balances (NECB) for pineapple cultivation systems. This will be further utilized for upcoming field study. This is challenging in so far as pineapple plants use the Crassulacean acid metabolism (CAM photosynthesis) and the manual closed chamber method has not yet been applied to determine NECB from CAM plants.

Keywords: nutrient-cycling, carbon sequestration, greenhouse gas (GHG) emissions, pineapple residue, climate change mitigation

How to cite: Macagga, R., Vaidya, S., Antonijevic, D., Schmidt, M., Lueck, M., Jancsó, M., Augustin, J., Sanchez, P., and Hoffmann, M.: Reuse of Pineapple Residue in Philippine Agriculture: determination of the net ecosystem C balance for a CAM plant in a pot-scale experiment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8240, https://doi.org/10.5194/egusphere-egu21-8240, 2021.

EGU21-16162 | vPICO presentations | BG2

Assessment of the dissolved inorganic and organic carbon flux in Cauvery, a tropical river of Southern India.

RamyaPriya Ramesh and Elango Lakshmanan

The carbon fluxes in rivers plays a critical role in the global carbon cycle but its role is always understated. The tropical rivers alone accounts for about 70% of global riverine carbon fluxes due to their large areal extent, varying climatic conditions and land use. Studies on the dissolved carbon fluxes in non-perennial tropical rivers are limited, but it holds much importance as that of perennial rivers. Hence, the present study was carried out with an objective to understand about the inorganic and organic carbon fluxes in a large non-perennial tropical river of Southern India. The samples were collected from 28 locations along the river thrice in a year from 2013-2020 and were analysed for major ions, DIC and DOC. The concentration of DIC in the river water in most of the locations is greater than that of DOC. The DOC concentration is greater at pristine locations thereby decreasing along the flow direction of the river, whereas the DIC concentration increases along the flow direction. The spatial and temporal variability in DOC and DIC concentrations is attributed due to the changes in the rainfall, river flow, climate, lithology, land use patterns, in the catchment. The DIC concentration was found to be majorly governed by silicate and carbonate weathering along with biogenic process, mineralisation and other river process, whereas the primary production, microbial process along with soil organic carbon influences the DOC concentration in the rivers. Thus, this study identifies the sources of DIC and DOC in rivers and the processes which influences the carbon export to the sea.

How to cite: Ramesh, R. and Lakshmanan, E.: Assessment of the dissolved inorganic and organic carbon flux in Cauvery, a tropical river of Southern India., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16162, https://doi.org/10.5194/egusphere-egu21-16162, 2021.

EGU21-4075 | vPICO presentations | BG2

The role of hydrological processes on enhanced weathering for carbon sequestration in soils in tropical areas

Giuseppe Cipolla, Salvatore Calabrese, Leonardo Valerio Noto, and Amilcare Porporato

To mitigate global warming, a noticeable research effort is being devoted to NCS (Natural Climate Solutions) as means to reduce greenhouse gas emissions or sequester carbon within the oceans or terrestrial environments by exploiting natural processes. Enhanced weathering is a NCS that aims to increase the weathering reaction rates of silicate minerals, by amending soils with crushed reactive minerals. Various studies have shown that this technique is favored by hot and humid climates (i.e., tropical ecosystems), since weathering reactions are mostly effective under high temperature and soil moisture. Despite olivine dissolution dynamics in laboratory conditions are quite well known, understanding and modeling them in field is still a challenge. Indeed, apart from some pot experiments involving soils of agricultural fields, only few weathering models are available. Given the urgency of the problem, models play a very important role for extrapolating results of laboratory and field experiments in both time and space, as well as for quantifying the impact of hydroclimatic fluctuations on the involved biogeochemical processes.

The present study explores the role of hydrological processes on long-term Forsterite dissolution, a highly reactive silicate mineral also known as Mg-olivine or simply olivine. Toward this goal, we present a novel dynamic mass balance model coupling ecohydrological and biogeochemical dynamics, including mineral dissolution. Results under different climate scenarios highlight that hydrological fluctuations lead to hysteretic patterns of weathering rate with soil moisture, meaning that the process maintains a memory of past events (i.e., dry or wet periods). The model allows to explore the twofold role of organic matter on enhanced weathering; indeed, while its decomposition is a source of CO2, organic matter also increases the soil CEC, thus buffering changes in soil pH. Carbon sequestration and nutrients availability due to enhanced weathering are quantified, in this study, as a function of MAP (Mean Annual Precipitation). Average CO2 that reacts with olivine can exceed 40 t ha-1 y-1 for MAP higher than 2000 mm, condition that is always reached in the tropics. This CO2 can be found as dissolved in soil water in the form of bicarbonate (HCO3-) and carbonate (CO32-) ions and will be leached away from the domain, eventually reaching the ocean. In presence of tropical climate olivine application also leads to an increase of soil pH and nutrients availability, especially calcium and magnesium, which in turn can enhance plant productivity. This study paves the way for a potential integration of enhanced weathering in agroecosystem management practices, especially in humid tropical regions since these are characterized by high MAP and temperature.

How to cite: Cipolla, G., Calabrese, S., Noto, L. V., and Porporato, A.: The role of hydrological processes on enhanced weathering for carbon sequestration in soils in tropical areas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4075, https://doi.org/10.5194/egusphere-egu21-4075, 2021.

BG3 – Land use and land cover change effects on surface biogeophysics, biogeochemistry and climate

EGU21-1654 | vPICO presentations | BG3

European Forest Management Portfolios Optimized for Uncertain Future Climate

Konstantin Gregor, Thomas Knoke, Andreas Krause, Mats Lindeskog, and Anja Rammig

Forests are considered a major player in climate change mitigation since they influence local and global climate through biogeochemical and biogeophysical feedbacks. However, they are themselves vulnerable to future environmental changes. Thus, forest management needs to focus on both mitigation and adaptation. The special challenge is that decisions on management strategies must be taken today while still a broad range of emission pathways is possible, and a good decision regarding one assumed pathway might turn out to be a bad decision when a different one materializes.

With our study we try to aid this decision-making process by finding management portfolios that provide relevant ecosystem functions such as local and global climate regulation, water availability, flood protection, and timber production for a wide range of future climate scenarios. To simulate according ecosystem processes and functions, we run the dynamic vegetation model LPJ-GUESS for the most relevant forest types across Europe for four different RCPs and five different management options. We analyze our simulation outputs using robust optimization techniques to determine optimal forest management portfolios for each 0.5° grid cell in Europe that ensure a balanced provision of all considered ecosystem functions in the future under any of the four RCPs.

Generally, our simulations and optimizations show that diversified management portfolios are most suitable to provide the set of considered ecosystem functions in all climate scenarios everywhere in Europe. While the portfolios show different compositions in different regions, they are quite similar in adjacent grid cells. The suggested future forest composition in Europe tends to be fairly close to present day values except for Northern Europe where a much higher proportion of deciduous types is proposed.

Management as high forest (trees emerging from seeds) remains the most important form of management. The proposed share of coppice management is much higher in Central and Northern Europe (~20%) than in Southern Europe, where its disadvantages (e.g., high water consumption and its non-suitability to provide long-lived wood products) are more pronounced.

A succession of ~30% of managed forest to natural forest is proposed by the optimization as it provides highest carbon storage and surface roughness values. However, this infeasibly high share is reduced if the provision of wood harvest is valued higher in the optimization compared to the other ecosystem functions.

Current public focus on forests lies often on their potential for carbon sequestration, but future forest management must also address the other services that they provide. This work gives insights on how this may be done.

How to cite: Gregor, K., Knoke, T., Krause, A., Lindeskog, M., and Rammig, A.: European Forest Management Portfolios Optimized for Uncertain Future Climate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1654, https://doi.org/10.5194/egusphere-egu21-1654, 2021.

EGU21-2818 | vPICO presentations | BG3

Biogeophysical effects of idealised land cover and land management changes on the climate

Steven De Hertog, Inne Vanderkelen, Felix Havermann, Suqi Guo, Julia Pongratz, Iris Manola, Dim Coumou, Edouard Davin, Sonia Seneviratne, Quentin Lejeune, Inga Menke, Carl-Friedrich Schleussner, and Wim Thiery

Land cover and land management (LCLM) changes have been highlighted for their critical role in low-end warming scenarios, both in terms of global mitigation and local adaptation. Yet the overall potential of LCLM options and their combination is still poorly understood. Here we model the climatic effects of four LCLM options using three state-of-the-art Earth system models, including the Community Earth System Model (CESM), the Max Planck Institute Earth System Model (MPI-ESM) and the European Consortium Earth System Model (EC-EARTH). The considered LCLM options represent idealized conditions:(i) a fully afforested world, (ii) a fully deforested world, (ii) a fully afforested world with extensive wood harvesting, and (iv) a fully deforested world with extensive irrigation. In these idealized sensitivity experiments, ran under present-day climate conditions, the effects of the different LCLM strategies represent an upper bound of the potential for global mitigation and local adaptation. To disentangle the local and non-local effects from the LCLM changes, a checkerboard perturbation, as proposed by Winckler et al. (2017) is applied.

Our first results show that deforestation leads to a pronounced warming in 2m air temperature in CESM over most regions, being most pronounced in the tropics (up to 4°C). In contrast, in the boreal regions of North America and Asia, deforestation causes a ~1°C cooling in 2m air temperature. In CESM, the local effect seems to dominate the temperature response from deforestation, while the resulting non-local effect overall has a smaller magnitude. This contrasts to the effect from afforestation, of which the non-local component dominates the 2m air temperature signal. Afforestation indeed shows a strong local cooling in the tropics and a slight local warming in the temperate and boreal regions, yet, the local cooling is regionally offset by  a global, non-local warming of up to 2 °C. In a next step, we will extend this analysis to the ensemble of Earth system models and increase our process-based understanding of these results and their implications on hot extremes as well as the effects on other temperature metrics (surface temperature and temperature of the lowest level of atmospheric column). Finally, we will perform a subgrid-scale comparison of the effects of LCLM on temperature.

References:

Winckler, J., Reick, C.H., Pongratz, J., 2017. Robust identification of local biogeophysical effects of land-cover change in a global climate model, American Meteorological society, 30(2), DOI: 10.1175/JCLI-D-16-0067.1

How to cite: De Hertog, S., Vanderkelen, I., Havermann, F., Guo, S., Pongratz, J., Manola, I., Coumou, D., Davin, E., Seneviratne, S., Lejeune, Q., Menke, I., Schleussner, C.-F., and Thiery, W.: Biogeophysical effects of idealised land cover and land management changes on the climate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2818, https://doi.org/10.5194/egusphere-egu21-2818, 2021.

EGU21-3552 | vPICO presentations | BG3

Assessing global biogeophysical effects of reconstructed land use and land cover change on climate since 1950 using a coupled land–atmosphere–ocean model

Huilin Huang, Yongkang Xue, Nagaraju Chilukoti, Ye Liu, Gang Chen, and Ismaila Diallo

Land use and land cover change (LULCC) is one of the most important forcings affecting climate in the past century. This study evaluates the global biogeophysical LULCC impacts in 1950–2015 by employing an annually updated LULCC map in a coupled land–atmosphere–ocean model. The difference between LULCC and control experiments shows an overall land surface temperature (LST) increase by 0.48 K in the LULCC regions and a widespread LST decrease by 0.18 K outside the LULCC regions. A decomposed temperature metric (DTM) is applied to quantify the relative contribution of surface processes to temperature changes. Furthermore, while precipitation in the LULCC areas is reduced in agreement with declined evaporation, LULCC causes a southward displacement of the intertropical convergence zone (ITCZ) with a narrowing by 0.5°, leading to a tripole anomalous precipitation pattern over the warm pool. The DTM shows that the temperature response in LULCC regions results from the competing effect between increased albedo (cooling) and reduced evaporation (warming). The reduced evaporation indicates less atmospheric latent heat release in convective processes and thus a drier and cooler troposphere, resulting in a reduction in surface cooling outside the LULCC regions. The southward shift of the ITCZ implies a northward cross-equatorial energy transport anomaly in response to reduced latent/sensible heat of the atmosphere in the Northern Hemisphere, where LULCC is more intensive. Tropospheric cooling results in the equatorward shift of the upper-tropospheric westerly jet in both hemispheres, which, in turn, leads to an equatorward narrowing of the Hadley circulation and ITCZ.

How to cite: Huang, H., Xue, Y., Chilukoti, N., Liu, Y., Chen, G., and Diallo, I.: Assessing global biogeophysical effects of reconstructed land use and land cover change on climate since 1950 using a coupled land–atmosphere–ocean model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3552, https://doi.org/10.5194/egusphere-egu21-3552, 2021.

EGU21-5789 | vPICO presentations | BG3

Integrating Land Cover and Land Management feedbacks into climate models: an emulator approach

Quentin Lejeune, Shruti Nath, Carl Schleussner, Jonas Schwaab, and Sonia Seneviratne

The role of Land Cover and Land Management (LCLM) changes in shaping the climate has garnered increasing interest, particularly in light of its potential for climate adaptation and mitigation. Earth System Models (ESMs), however, have hitherto handled LCLM-climate interactions as a unidirectional process, lacking explicit treatment of LCLM-Climate feedbacks. These feedbacks nevertheless are linked to extreme climate events such as heat waves and drought, which in turn carry economic costs through worker productivity, crop yields and food prices. It is thus essential to integrate LCLM processes and their feedbacks into a ESMs, in order to build consistent storylines for future development pathways that take into account their potential for adaptation and mitigation. Emulators represent a computationally cheap but effective way of approximating ESM with an added advantage of agility in scenario exploration. Here we outline an emulator approach to represent LCLM-Climate feedbacks based on a framework developed by Beusch et al. (2020). The emulator provides monthly, spatially explicit data from yearly global mean temperature and uses Generalised Additive Models (GAMs) to represent LCLM-Climate feedbacks. The emulator is to be used in the LAnd MAnagement for CLImate Mitigation and Adaptation (LAMACLIMA) project, and is trained on dedicated ESM simulations that isolate the effects of key land management practices focussed on by LAMACLIMA: irrigation, de/reforestation and wood. Key variables produced by the emulator include temperature, Wet Bulb Globe Temperature and labour productivity.

 

Beusch, L., Gudmundsson, L., & Seneviratne, S. I. (2020). Emulating Earth System Model temperatures: from global mean temperature trajectories to grid-point level realizations on land. Earth System Dynamics, 11(1), 139–159. https://doi.org/10.5194/esd-11-139-2020

How to cite: Lejeune, Q., Nath, S., Schleussner, C., Schwaab, J., and Seneviratne, S.: Integrating Land Cover and Land Management feedbacks into climate models: an emulator approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5789, https://doi.org/10.5194/egusphere-egu21-5789, 2021.

EGU21-6002 | vPICO presentations | BG3

Carbon storage in soils and plant biomass under future climate and land use pressures

Dmitry Yumashev, Victoria Janes-Bassett, John Redhead, Ed Rowe, and Jessica Davies

It is widely accepted in the scientific, business and policy communities that meeting the Paris Agreement targets will require a large-scale deployment of negative emission technologies and practices. As a result, nature-based climate solutions, including carbon sequestration (Cseq) in soils and forests, have received much attention in the literature recently. Several national and global assessments have identified considerable potential for terrestrial Cseq, while other studies have raised doubts regarding its practical limits in the face of the likely future pressures from climate change and land use change. In general, the existing Cseq assessments lack sensitivity to climate change, perspective on local land use and nutrient limitations. Accounting for these factors requires process-based modelling, and is feasible only at national to regional scales at present, underpinned by a wide body of local evidence. Here, we apply an integrated terrestrial C-N-P cycle model (N14CP) with representative ranges of high-resolution climate and land use scenarios to estimate Cseq potential in temperate regions, using the UK as a national-scale example. Meeting realistic UK targets for grassland restoration and forestation over the next 30 years is estimated to sequester an additional 120 TgC by 2100 (similar to current annual UK greenhouse gas emissions), conditional on climate change of <2°C. Conversely, UK arable expansion would reduce Cseq by a similar magnitude, while alternative arable management practices such as extensive rotations with grass leys would have a comparatively small effect on country-wide Cseq outcomes. Most importantly, the simulations suggest that warmer climates will cause net reductions in Cseq as soil carbon losses exceed gains from increased plant productivity. Our analysis concludes that concerted land use change can make a moderate contribution to Cseq, but this is dependent on us cutting emissions from fossil fuels, soil degradation and deforestation in line with a <2°C pathway.

How to cite: Yumashev, D., Janes-Bassett, V., Redhead, J., Rowe, E., and Davies, J.: Carbon storage in soils and plant biomass under future climate and land use pressures, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6002, https://doi.org/10.5194/egusphere-egu21-6002, 2021.

EGU21-7085 | vPICO presentations | BG3

The Role of El Niño in Modulating the Effects of Deforestation in the Maritime Continent

Tinghui lee and Minhui lo

The deforestation rate in the Maritime Continent (MC) has been accelerating during the past several decades. Understanding the changes in local hydro-climatological cycles as deforestation takes place is essential because the MC is suffering from frequent and extreme droughts and fires, which often occur during the dry season and are more severe during El Niños. Therefore, this study explores how deforestation affects the hydrological cycle and precipitation in the MC during El Niños, focusing on the boreal autumn season and using the coupled atmosphere-land model simulations. It is found that the precipitation over the MC increases in the deforestation experiments, and the precipitation responses can be magnified during El Niño events. A strong subsidence anomaly associated with El Niño does not prevent enhanced convection associated with local deforestation. Instead, the subsidence reduces the cloud cover in the MC region during El Niño, which increases the incoming solar radiation and increases surface temperatures. Under a warmer environment induced by El Niño, the nonlinear biogeophysical feedbacks associated with deforestation also play a critical role in more substantial land surface warming. A warmer land surface induces a more unstable atmospheric environment associated with a tendency toward enhanced local convection and lateral moisture convergence. This study highlights how the different mean climate states may modulate the impact of local land-use changes on hydroclimatological cycles in the Maritime Continent, and sheds light on the state of our knowledge of interactions between the local land surface and remote large-scale atmospheric circulations.

How to cite: lee, T. and lo, M.: The Role of El Niño in Modulating the Effects of Deforestation in the Maritime Continent, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7085, https://doi.org/10.5194/egusphere-egu21-7085, 2021.

EGU21-7715 | vPICO presentations | BG3

Reconciling different approaches to quantifying surface cooling induced by afforestation in China using satellite observations

Huanhuan Wang, Chao Yue, Sebastiaan Luyssaert, Jie Zhao, and Hongfei Zhao

Forest cover change can cause strong local biophysical feedbacks on climate. Satellite observations of land surface temperature (T) and land cover distribution or forest cover change have been widely used to examine the effects of afforestation/deforestation on local surface temperature change (ΔT). However, different approaches were used by previous analyses to quantifying ΔT, and it remains unclear whether results of ΔT by these approaches are comparable. We identified three influential approaches to quantifying ΔT used by previous studies, namely the actual ΔT resulting from actual changes in forest coverage over time and accounting for changes in background climate (ΔTa proposed by Alkama and Cescatti, 2016), potential ΔT by hypothesizing potential shifts between non-forest and forest at given native spatial resolutions of satellite products (ΔTp1 by Li et al., 2015), and potential ΔT, but using the singular value decomposition technique to derive ΔT by hypothesizing a shift between a 100% complete non-forest and 100% forest (ΔTp2 by Duveiller et al., 2019). China realized large-scale afforestation making it a suitable test case to compare satellite-based approaches for estimating ΔT following afforestation. We hypothesize that (1) ΔTa depends on the fraction of ground area that’s been afforested (Faff). (2) The relative magnitude between different approaches should be: ΔTa < ΔTp1 < ΔTp2. (3) When ΔTa is extended to a hypothetical case that Faff reaches 100%, it should be comparable to ΔTp1 or ΔTp2. We used multiple satellite observation products to test these hypotheses. The results show that the magnitude of actual daytime surface cooling by afforestation (ΔTa) increases with Faff, and is significantly lower than ΔTp1 and ΔTp2. But no significant difference was found between ΔTp1 and ΔTp2. A linear regression model established between ΔTa and Faff extends the ΔTa, when Faff reaches 100%, to a comparable magnitude than ΔTp1 and ΔTp2. Our study thus highlights the importance to consider the actual surface cooling impact by afforestation projects in contrast to the potential effects, and provides a first study to reconcile different approaches to quantify the land surface temperature change due to afforestation.

How to cite: Wang, H., Yue, C., Luyssaert, S., Zhao, J., and Zhao, H.: Reconciling different approaches to quantifying surface cooling induced by afforestation in China using satellite observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7715, https://doi.org/10.5194/egusphere-egu21-7715, 2021.

EGU21-8053 | vPICO presentations | BG3

Comparison of modelled radiation budgets with observations over lichens and shrubs at Mount Imingfjell, Norway

Anastasiia Vasiakina, Hans Renssen, and Peter Aartsma

Mountains are some of the most inaccessible regions, where not many weather stations located due to the high altitudes. Thus, the amount of available mountain meteorological data is limited. One of the modern solutions to data insufficiency is modelling. However, it remains challenging to assess how well a model simulates local climate conditions.

The main goal of this study was to check the model accuracy by comparing its results to observed data, with a focus on the radiation budget.

The Community Land Model 4.5 (CLM4.5) provided by the University of Oslo was used. It is a one-dimensional model and the default land component in the Community Earth System Model 1.2. CLM4.5 simulates various biogeophysical and biogeochemical processes based on surface energy, water, and carbon balances [Oleson et al. 2013]. Here, the model was run from 1901 to 2014 in the offline mode, meaning it was getting input from a pre-existing dataset. Modelled fluxes from the radiation budget, such as incoming (Kin) and outgoing shortwave (Kout) radiation, incoming (Lin) and outgoing (Lout) longwave radiation, net all-wave (Q*), net shortwave (K*) and net longwave (L*) radiation, were used for compassion with observations.

A 2.5×0.2 km site on Mount Imingfjell (1191 m) in southern Norway was selected as the study object. Different microclimatic parameters, including radiation fluxes, were measured separately over lichens and shrubs for 44 days in the 2018-2019 summers [Aartsma et al. 2020]. These vegetation types were chosen to understand the differences between them and see the potential impact of “shrubification” on surface albedo. Since there was no time overlap between modelled and observed data, we had to make datasets more comparable. 44 days from field data were used to create composite datasets that represent three temperature regimes based on data from the nearest weather station: “cold”, “normal” and “warm”. Each observation was assigned to one of these temperature regimes. In CLM4.5, recently available years were analysed to find ones with average summer temperatures closest to the stated temperature regimes. Statistical analysis, such as a two-sample t-test, was performed to see if there were any significant differences between the datasets.

T-tests showed that modelled Kin, Lin and K* were always similar to measurements, except for Lin and K* in “cold” conditions. CLM4.5 Kout differed from observed ones in almost all regimes. Simulated L*, Q* and Lout varied between temperature conditions and vegetation types. Still, about 70% of the modelled fluxes closely resembled the shrub ones, while only around 50% resembled lichens. Modelled albedo was also closer to shrub albedo.

In conclusion, CLM4.5 most likely modelled credible values for radiation fluxes, but further research is needed for greater clarity.

References

1. Aartsma, P., Asplund, J., Odland, A., Reinhardt, S., & Renssen, H. (2020). Surface albedo of alpine lichen heaths and shrub vegetation. Arctic, Antarctic, and Alpine Research, 52(1), 312-322.

2. Oleson, K., Lawrence, D., Bonan, G., Drewniak, B., Huang, M., Koven, C., . . . Yang, Z.-L. (2013). Technical description of version 4.5 of the Community Land Model (CLM).

How to cite: Vasiakina, A., Renssen, H., and Aartsma, P.: Comparison of modelled radiation budgets with observations over lichens and shrubs at Mount Imingfjell, Norway, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8053, https://doi.org/10.5194/egusphere-egu21-8053, 2021.

EGU21-9690 | vPICO presentations | BG3

Global consistency in response of terrestrial ecosystem respiration to temperature

Huanyuan Zhang, Zhiyuan Zhang, Zikun Cui, Feng Tao, Ziwei Chen, Yaxuan Chang, Vincenzo Magliulo, Georg Wohlfahrt, and Dongsheng Zhao

Many studies have been carried out to quantify the trend of terrestrial ecosystem respiration (Re) in a warming world, but a conclusive answer has not yet been confirmed because the temperature sensitivity of Re was found inconsistent under different scales or regarding different types of respiratory flux.  Aiming at clarifying the relationship between temperature and Re across different scales, we proposed a method to counteract the confounding effect and applied nine empirical models to a 1,387 site-years FLUXNET dataset.  Regarding the temperature sensitivity of half-hourly Re records, we found a surprisingly consistent result that the sigmoid functions outcompeted other statistical models in almost all datasets (account for 82%), and on average, achieved a staggering R2 value of 0.92, indicating the positive correlation between Re and temperature on fine time scale (within one site-year dataset).  Even though Re of all biomes followed sigmoid functions, the parameters of the S-curve varied strongly across sites.  This explains why measured Q10 value (an index denote temperature sensitivity) largely depends on observation season and site.  Furthermore, on the interannual variation of Re, we did not find any relationship between mean annual temperature (MAT) and mean annual Re within any site, which implies that the small year-to-year variation of the sigmoid pattern is large enough to counteract the warming effect on Re.  This study thereby put forward a conceptual model to integrate the relationship between temperature and Re under different scales. It also provided evidences to support the argument that the relationship between MAT and mean annual Re (i.e., respiration under global warming) should not be inferred from studies on other temporal or spatial scales.

How to cite: Zhang, H., Zhang, Z., Cui, Z., Tao, F., Chen, Z., Chang, Y., Magliulo, V., Wohlfahrt, G., and Zhao, D.: Global consistency in response of terrestrial ecosystem respiration to temperature, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9690, https://doi.org/10.5194/egusphere-egu21-9690, 2021.

EGU21-9826 | vPICO presentations | BG3

Simulated biogeochemical effects of idealized land cover and land management changes

Suqi Guo, Julia Pongratz, Felix Havermann, Steven De Hertog, Wim Thiery, Iris Manola, Dim Coumou, Quentin Lejeune, and Carl-Friedrich Schleussner

Land cover and land management (LCLM) changes are important sources and sinks for anthropogenic CO2 fluxes. Current earth system models (ESMs) are capable to simulate the globally most sensitive LCLM changes (strong effects or large spatial extent in the earth system) such as de- and afforestation, wood harvest and irrigation, however, a comprehensive analysis between these ESMs is still absent. The present study aims to quantify the biogeochemical effects of forest cover changes, wood harvesting and irrigation of croplands on the global carbon cycle.

 

Therefore, we conducted coupled atmosphere-ocean-land experiments of idealized global deforestation with and without cropland irrigation as well as global re-/afforestation with and without wood harvest over a 150-year period under present day solar and trace gas forcing. All experiments were simulated by three different ESMs (MPI-ESM, EC-EARTH and CESM) to quantify inter-model uncertainty and potentially uncover specific model biases. The analysis focuses on the transient response of land carbon fluxes and pools after an abrupt LCLM practice change, in order to track the emergence of signals that could potentially mitigate climate change. Additionally, we want to unravel model differences concerning the temporal dynamics of LCLM change effects. Since greenhouse gases (GHG) concentration is kept constant at present-day level, the climate changes here arise from the biogeophysical effects of LCLM changes. We use a checkerboard approach to separate local and non-local components of the climate changes as proposed by Winckler et al., 2017, i.e. we separate the changes in climate induced locally by the LCLM changes from those induced remotely by advection and changes in atmospheric circulation.

 

First results with the MPI-ESM show that immediate global deforestation starting from present-day land-use distribution causes a 824 GtC loss of the total land carbon pool throughout the simulation period of 150 years, about 46% of which stem from tropical regions (17°S–17°N). Land carbon stocks are not balanced until the end of the simulation, which indicates that the land will continue to emit CO2 to the atmosphere and a long-term commitment by deforestation for climate change. Non-local effects lead to a loss of 26 GtC from land, again with largest losses found for the tropical regions. Even though it is a small part compared to the total loss (local plus non-local effect), it reveals potentially substantial consequences that LCLM changes at large scale can have unintendedly on other regions, including remote pristine ones, through biogeophysical climate change.

How to cite: Guo, S., Pongratz, J., Havermann, F., De Hertog, S., Thiery, W., Manola, I., Coumou, D., Lejeune, Q., and Schleussner, C.-F.: Simulated biogeochemical effects of idealized land cover and land management changes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9826, https://doi.org/10.5194/egusphere-egu21-9826, 2021.

Land-use change (LU) is a major regional climate forcing that affects carbon-water-energy fluxes and, therefore, near-surface air temperature. Although there are uncertainties in LU impacts in the historical climate, there is a growing consensus towards a cooling influence in the mid-latitudes. However, how a drier and warmer land surface condition in the future climate can change the LU impacts are not investigated well.

We use a comprehensive set of five coupled climate models from the CMIP6-LUMIP project to assess the changing influence of the LU change. We use two methodologies: (1) direct method – where LU impacts are estimated by subtracting the ‘no-LU’ climate experiment from the control experiment that includes LU, and (2) Kumar et al., 2013 (K13) method where LU impacts are estimated by comparing climate change impacts between LU and no-LU neighboring regions.

First, we compared the LU impacts in the historical climate and between the direct method and K13 methods using the multi-model analysis. In the North America LU change region, the direct method shows a cooling impact of (-0.14 ± 0.13°C). The K13 methods show a smaller cooling impact (-0.09 ± 0.08°C). In terms of energy balance, the direct method shows a reduction of net shortwave radiation (-0.82 ± 0.91 watts/m2) the K13 method shows a cleaner result of (-1.25 ± 0.60 watts/m2), as expected. We suspect that a more substantial influence of the LU change in the direct method is due to large-scale circulation driven response or due to the internal variability that has been canceled out in the K13 method.

Next, we extend the K13 method to assess the LU impacts in the future climate. Direct methods are not available for the future climate experiment in CMIP6-LUMIP datasets. We find that a cooling impact of LU change has become statistically insignificant in the future climate (-0.17 ± 0.19°C). A similar influence is also found in the reduction of the net shortwave radiation (-1.92 ± 3.34 watts/m2). We also found that climate change impacts on temperature are an order of magnitude greater than LU impact in the future climate. Hence, we hypothesize that higher warming has contributed to the larger uncertainty in LU impacts. We will also discuss LU impacts in Eurasia and Indian subcontinent.

 

 

Reference

Kumar, S., Dirmeyer, P. A., Merwade, V., DelSole, T., Adams, J. M., & Niyogi, D. (2013). Land use/cover change impacts in CMIP5 climate simulations: A new methodology and 21st century challenges. Journal of Geophysical Research: Atmospheres, 118(12), 6337-6353.

How to cite: Singh, A. and Kumar, S.: Increased uncertainty in Land-Use change impacts on temperature due to Global Warming in CMIP6-LUMIP experiments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10313, https://doi.org/10.5194/egusphere-egu21-10313, 2021.

EGU21-10471 | vPICO presentations | BG3

Local and non-local climatic impacts of land use across scales

Liang Chen

It has been widely recognized that land use/land cover changes have great potential to influence climate at different scales. However, their local and non-local impacts have not been well understood. First, previous studies are limited by the assumption that the local impacts of land use do not modify the atmospheric background states. Second, land-use impacts may vary if simulations are conducted at a different spatial scale. In this study, we investigate the local and non-local impacts of historical land use using the Community Earth System Model version 2, and explore the possible influence of model resolutions on the local and non-local impacts. The local and non-local impacts of land use are separated using atmospheric nudging, in which the horizontal winds in the upper atmosphere are forced to follow the ERA-Interim reanalysis, whereas the nudging strength is zero at the surface. The multi-resolution experiments suggest that the local impacts of land use are consistent at different spatial scales, but the non-local impacts are influenced by the model resolution. We will also discuss the local and non-local impacts of land use on climate extremes across scales. This study presents a new way to distinguish the local and non-local impacts and highlights the uncertainty in simulated land-use impact in climate studies. 

How to cite: Chen, L.: Local and non-local climatic impacts of land use across scales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10471, https://doi.org/10.5194/egusphere-egu21-10471, 2021.

EGU21-11207 | vPICO presentations | BG3

Assessing the effects of climate and land use land cover changes on recent carbon storage in terrestrial ecosystem using model-satellite approach over Wallonia, Belgium

Arpita Verma, Louis Francois, Ingrid Jacquemin, Merja Tölle, Huan Zhang, and Benjamin Lanssens

The use of a dynamic vegetation model, CARAIB, to estimate carbon sequestration from land-use and land-cover change (LULCC) offers a new approach for spatial and temporal details of carbon sink and for terrestrial ecosystem productivity affected by LULCC. Using the remote sensing satellite imagery (Landsat) we explore the role of land use land cover change (LULCC) in modifying the terrestrial carbon sequestration. We have constructed our LULCC data over Wallonia, Belgium, and compared it with the ground-based statistical data. However, the results from the satellite base LULCC are overestimating the forest data due to the single isolated trees. We know forests play an important role in mitigating climate change by capturing and sequestering atmospheric carbon. Overall, the conversion of land and increase in urban land can impact the environment. Moreover, quantitative estimation of the temporal and spatial pattern of carbon storage with the change in land use land cover is critical to estimate. The objective of this study is to estimate the inter-annual variability in carbon sequestration with the change in land use land cover. Here, with the CARAIB dynamic vegetation model, we perform simulations using remote sensing satellite-based LULCC data to analyse the sensitivity of the carbon sequestration. We propose a new method of using satellite and machine learning-based observation to reconstruct historical LULCC. It will quantify the spatial and temporal variability of land-use change during the 1985-2020 periods over Wallonia, Belgium at high resolution. This study will give the space to analyse past information and hence calibrate the dynamic vegetation model to minimize uncertainty in the future projection (until 2070). Further, we will also analyse the change in other climate variables, such as CO2, temperature, etc. Overall, this study allows us to understand the effect of changing land-use patterns and to constrain the model with an improved input dataset which minimizes the uncertainty in model estimation.

How to cite: Verma, A., Francois, L., Jacquemin, I., Tölle, M., Zhang, H., and Lanssens, B.: Assessing the effects of climate and land use land cover changes on recent carbon storage in terrestrial ecosystem using model-satellite approach over Wallonia, Belgium, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11207, https://doi.org/10.5194/egusphere-egu21-11207, 2021.

EGU21-12112 | vPICO presentations | BG3

Updated land use and land cover change (LULCC) emission estimates based on new high-resolution LULCC forcing data

Raphael Ganzenmüller, Selma Bultan, Karina Winkler, Richard Fuchs, and Julia Pongratz

Land use and land cover change (LULCC) has a significant role for the global carbon cycle. Despite big improvements in LULCC emission modelling, related uncertainties remain relatively high. Major uncertainties in quantifying LULCC emissions stem from uncertainties in underlying LULCC datasets. The novel, high-resolution (~1 km×1 km) LULCC dataset HIstoric Land Dynamics Assessment+ (HILDA+) reflects gross transitions derived from multiple remote sensing products and offers an alternative to existing land use change datasets, serving as forcing for process-based and bookkeeping models. By incorporating HILDA+ in the “bookkeeping of land use emissions” (BLUE) model, which is one of the three bookkeeping models used in the Global Carbon Budget 2020, we gain a different temporal and spatial perspective on LULCC estimates and related sources of uncertainty. 

We compare our results to emission estimates based on LUH2, which is broadly used as LULCC forcing for process-based and bookkeeping models. First results of our analysis show overall lower LULCC emissions for the estimates based on HILDA+. For the time period 1990-2019, mean yearly emission estimates based on HILDA+ are 0.595 GtC yr−1 compared to 1.368 GtC yr−1 based on LUH2. Reasons are lower emissions from cropland expansion and less carbon uptake from vegetation regrowth after abandonment of managed land (i.e. a smaller carbon sink). Furthermore, fewer discontinuities in the BLUE runs with the HILDA+ forcing compared to the LUH2-based estimates suggests a better representation of land use dynamics and their effects. Overall, the simulations based on HILDA+ capture spatial heterogeneity to a greater degree and provide a more detailed picture of local sources and sinks, which is crucial for (1) a better representation of component fluxes (e.g. deforestation, degradation) and (2) effective mitigation and adaptation policies.

How to cite: Ganzenmüller, R., Bultan, S., Winkler, K., Fuchs, R., and Pongratz, J.: Updated land use and land cover change (LULCC) emission estimates based on new high-resolution LULCC forcing data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12112, https://doi.org/10.5194/egusphere-egu21-12112, 2021.

EGU21-12561 | vPICO presentations | BG3

Evaluation of soil carbon dynamics after land use change in CMIP6 land models using chronosequences

Victor Brovkin, Lena Boysen, David Wårlind, Daniele Peano, Anne Sofie Lansø, Christine Delire, Eleanor Burke, Christopher Poeplau, and Axel Don

Land surface models are used to provide global estimates of soil organic carbon (SOC) changes after past and future land use change (LUC). To evaluate how well the models capture decadal scale changes in SOC after LUC, we provide the first consistent comparison of simulated time series of LUC by six land models all of which participated in the Coupled Model Intercomparison Project Phase 6 (CMIP6) with soil carbon chronosequences (SCC). For this comparison we use SOC measurements of adjacent plots at four high-quality data sites in temperate and tropical regions. We find that initial SOC stocks differ among models due to different approaches to represent SOC. Models generally meet the direction of SOC change after reforestation of cropland but the amplitude and rate of changes vary strongly among them. Further, models simulate SOC losses after deforestation for crop or grassland too slow due to the lack of crop harvest impacts in the models or an overestimation of the SOC recovery on grassland. The representation of management, especially nitrogen levels is important to capture drops in SOC after land abandonment for forest regrowth. Crop harvest and fire management are important to match SOC dynamics but more difficult to quantify as SCC hardly report on these events. Based on our findings, we identify strengths and propose potential improvements of the applied models in simulating SOC changes after LUC.

How to cite: Brovkin, V., Boysen, L., Wårlind, D., Peano, D., Lansø, A. S., Delire, C., Burke, E., Poeplau, C., and Don, A.: Evaluation of soil carbon dynamics after land use change in CMIP6 land models using chronosequences, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12561, https://doi.org/10.5194/egusphere-egu21-12561, 2021.

EGU21-13361 | vPICO presentations | BG3

Global Carbon Fluxes Induced by Agriculture-Related Land-Use and Land Cover Change Activities

Atul Jain, Xiaoming Xu, and Shijie Shu

The aim of this study is to estimate the net carbon fluxes from agriculture-related land-use and land cover change (LULCC) activities, which are referred to as emissions from the land due to human activities. These include land use (LU, e.g., farmland for food and feed production, including management) and land cover changes (LCC, e.g., deforestation for and reforestation of agricultural land, and conversion of grasslands and pastureland to agriculture land or vice versa). Agriculture land-use practices could be a source of atmospheric CO2. However, the management of agricultural practices may reduce carbon emissions and increase soil carbon sequestration. Simultaneously, land-cover change activities clear existing ecosystems, their biomass and disturb the soil, generating carbon emissions. Previous earth system models usually have a simple or no representation of land agriculture practices, such as planting crops, fertilization, irrigation, harvesting grains for food and livestock-feed, recovering crop residue for feed and other usages, and grazing, livestock-feed, and manure cycle. This study uses a land surface model with spatially heterogeneous representations of such agricultural land use activities, in addition to land cover change, such as the change from forest to agricultural land. Our study shows the net agricultural land area increase of 0.11 million hectares/yr during 2007-2013, including 2.12 million hectares/yr of other land converted to agricultural land and 2.01 million hectares/yr of agricultural land converted to other lands. The results show that global net carbon flux due to agriculture-related LULCC is 2.26 Pg C/yr (net emission), consisting of 38% due to land-use activities and 62% due to land cover change. South America (22%), North America (19%), and South and Southeast Asia (13%) are the top contributing regions for net carbon flux induced by LULCC. South America has contributed the most flux from land cover change (18%), while North America has generated the most carbon flux due to land-use activities (12%) among all macro geopolitical regions.  By quantifying the carbon fluxes induced by different agriculture activities this study provides a complete estimate of the yearly carbon cycle in the agriculture system at the spatial scale, which may improve the representations of agriculture land use activities in Earth System Models.

How to cite: Jain, A., Xu, X., and Shu, S.: Global Carbon Fluxes Induced by Agriculture-Related Land-Use and Land Cover Change Activities, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13361, https://doi.org/10.5194/egusphere-egu21-13361, 2021.

EGU21-13385 | vPICO presentations | BG3

Observational and Modeling Analysis of Land-Atmosphere Interactions over Adjacent Irrigated and Rainfed Cropland During the GRAINEX Field Campaign.

Eric Rappin, Rezaul Mahmood, Nair Udaysankar, and Roger Pielke Sr.

Continued scientific study has revealed that land use and land cover change play a key role in climate and that the application of irrigation is an important biogeophysical contributor to climate modification across spatial scales. The Great Plains Irrigation Experiment (GRAINEX) was conducted in the spring and summer of 2018 to investigate Land-Atmosphere interactions just prior to and through the growing season across adjacent, but distinctly unique, soil moisture regimes (contrasting irrigated and rainfed fields). GRAINEX was uniquely designed for the development and analysis of an extensive observational dataset for comprehensive process studies of Land-Atmosphere interactions, by focusing on irrigated and rainfed croplands in a ~100 x 100 km domain in southeastern Nebraska. Observation platforms included multiple NCAR EOL Integrated Surface Flux Systems and Integrated Sounding Systems, NCAR CSWR Doppler Radar on Wheels, 1200 radiosonde balloon launches from 5 sites, the NASA GREX airborne L-Band radiometer, and 75 University of Alabama-Huntsville Environmental Monitoring Economic Monitoring Sensor Hubs (EMESH mesonet stations). The presentation will provide an overview of the field campaign, the dataset collected, and investigate the contrast of L-A intractions across an irrigation gradient through observations and mesoscale/microscale modeling on timescales ranging from the diurnal to the seasonal. Attention will be given to how variations in the land surface state, as a function of irrigation fraction, impacts near-surface meteorology and atmospheric boundary layer evolution at local and regional scales.

How to cite: Rappin, E., Mahmood, R., Udaysankar, N., and Pielke Sr., R.: Observational and Modeling Analysis of Land-Atmosphere Interactions over Adjacent Irrigated and Rainfed Cropland During the GRAINEX Field Campaign., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13385, https://doi.org/10.5194/egusphere-egu21-13385, 2021.

BG6 – Sustainable phosphorus management and recovery: linking phosphorus and other element/material cycles

EGU21-14897 | vPICO presentations | BG6 | Highlight

Towards a history of Holocene P dynamics for the Northern Hemisphere using lake sediment geochemical records

Madeleine Moyle, John Boyle, and Richard Chiverrell

Present day phosphorus (P) enrichment and accelerated P cycling are changes superimposed on a dynamic Holocene history of landscape recovery from glaciation, changes in climate, and long-term low-intensity human activity. Knowledge of the changing role of human activity in driving long-term P dynamics is essential for understanding landscape P export and managing both terrestrial and aquatic environments.

Here we apply a simple process model to published lake sediment geochemical P records from 24 sites distributed across the Northern Hemisphere, producing Holocene records of landscape P yield and reconstructions of lake water TP concentrations. These records are a first attempt to produce values for average P export for the Northern Hemisphere over the Holocene, which can be used for constraining long-term landscape P cycling models.

Individual site trajectories of reconstructed Holocene landscape P yield and lake water TP varied systematically, with differences attributable to landscape development history, in turn driven by climate, human impact and other local factors. Three distinct traits are apparent across the records. Mountain sites with minimal direct human impact show falling Holocene P supply, and conform to conceptual models of natural soil development (Trait 1). Lowland sites  where substantial (pre-)historic agriculture was present show progressively increasing Holocene P supply (Trait 2). Lowland sites may also show a rapid acceleration in P supply over the last few centuries, where high intensity land use, including settlements and farming, are present (Trait 3).

This long-term perspective is pivotal to understanding drivers of change in coupled terrestrial and aquatic P cycling. Our reconstructions of long-term lake water TP are particularly useful for target-driven management of aquatic systems.

How to cite: Moyle, M., Boyle, J., and Chiverrell, R.: Towards a history of Holocene P dynamics for the Northern Hemisphere using lake sediment geochemical records, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14897, https://doi.org/10.5194/egusphere-egu21-14897, 2021.

Lake sediment records offer the opportunity to quantify past changes in catchment P exports, information essential if we are to understand the long-term drivers that control P cycling. However, the interpretation of such records generally depends on the assumption that sediment P concentration profiles remain intact after burial. This assumption appears to be in conflict with the phenomenon of internal P loading, whereby P is exported from sediment to the water column. Here we apply a simple long-term mass balance model to published sediment record data from Søbygaard, a site that has an exceptionally high internal P loading, and an exceptionally well-studied sediment P record (Søndergaard and Jeppesen, 2019). Repeat cores collected from 1985 to 2004 constrain the temporal evolution of a sediment P peak arising from past sewage inflows, providing a critical test of our modelling approach. We find that useful sediment inference of long-term mean lake water TP is preserved in the sediment record, and predict also useful inference of long-term mean external P loading. Limitation on temporal resolution of the records is examined.

How to cite: Boyle, J. and Moyle, M.: Using lake sediment P records to estimate internal and external P loading and historic long-term lake water mean TP: a case study using published records from Søbygaard Sø, Denmark., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13278, https://doi.org/10.5194/egusphere-egu21-13278, 2021.

EGU21-13066 | vPICO presentations | BG6

Statistical study of sedimentary phosphorus content in French reservoirs and identification of P variability driving factors 

Claire Lix, Marion Rabiet, Malgorzata Grybos, Pierre-Alain Danis, Anne Blondeau, François Louvet, and Véronique Deluchat

Phosphorus (P), an essential element for living organisms, is often considered as the limiting factor of eutrophication in aquatic environments, especially in reservoirs. In order to limit their environmental degradation and to meet the requirements of good ecological quality imposed by the European Water Framework Directive (WFD), actions have been implemented in the past decades to reduce the exogenous P influx to reservoirs. However, despite the decrease in external P inputs to the water from agriculture and domestic wastewater, eutrophication keeps expanding due to sedimentary P flux to the water column. Assessing the quality of sediments in reservoirs and the risk of of sedimentary P transfer to the water column is therefore a major issue. The POMOSED project aims to investigate the relevance of the WFD regulatory parameters, monitored since 2005, in the evaluation of sediment quality with respect to P. This work presents an inventory of sedimentary P contents in French reservoirs and identifies the factors contributing to the observed P variability from the physico-chemical sedimentary composition and the reservoirs and watersheds characteristics.

Statistical analyses were conducted on sedimentary composition data (total phosphorus (TP), iron (Fe), manganese (Mn), aluminium (Al), Kjeldahl nitrogen (NTK) and organic carbon (OC)) from 219 French reservoirs. The characteristics of their watersheds (geology, altitude, agricultural and artificial surfaces, …) and their morphology (e.g. depth,  surface area, …) were also included in the statistical analyses.

The sediments showed large variability in the TP concentration varying from 172 to 4350 mg.kg-1 with mean and median values of 1310 and 1060 mg.kg-1 respectively. The variability of sedimentary TP was observed both spatially and temporally. We highlighted significant correlations of PT content with Fe, Al, NTK and OC. We pointed out that the geological substratum, the level of anthropization of the watershed and the depth of the reservoirs are driving factors for TP concentration in sediments. Therefore, the WFD monitoring allows to distinguish several typologies of sediment with respect to TP. The typologies inducing an enrichment in TP of the sediments are crystalline substrate sediments rich in Fe and OC, deep reservoirs inducing anoxia development and an anthropized watershed. However, an enrichment in TP of the sediments does not necessarily indicate an anthropic pressure as shown by the influence of geology and the composition of sediments. These results might be included into multiple linear models linking PT concentrations to the other elements concentrations (CO and Fe) and the different factors (geology > anthropization > reservoir depth).

How to cite: Lix, C., Rabiet, M., Grybos, M., Danis, P.-A., Blondeau, A., Louvet, F., and Deluchat, V.: Statistical study of sedimentary phosphorus content in French reservoirs and identification of P variability driving factors , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13066, https://doi.org/10.5194/egusphere-egu21-13066, 2021.

EGU21-11061 | vPICO presentations | BG6

Population structure of magnetotactic bacteria forming intracellular polyphosphates in the water column of Lake Pavin, a freshwater ferruginous environment

Cécile Bidaud, Caroline L. Monteil, Nicolas Menguy, Vincent Busigny, Didier Jézéquel, Eric Viollier, Cynthia Travert, Fériel Skouri-Panet, Karim Benzerara, Christopher T. Lefevre, and Elodie Duprat

Phosphorus (P) is essential to life but a limiting nutrient in many ecosystems. Understanding the role of microorganisms in P cycling, especially the processes of P uptake and storage, is a major environmental issue.  Only few models with a high capability to sequester P are known, mostly in marine environments. We thus need to improve our knowledge about other model of sequestration and especially in freshwater environments.

Freshwater magnetotactic bacteria (MTB) affiliated to the Magnetococcaceae family have been identified within the water column of Lake Pavin in France [3]. Similarly, to the marine sulfoxidizers Thiomargarita and Beggiatoa [1, 2], they accumulate intracellular polyphosphates (PolyP) to a uniquely high extent, up to 90% of their cell volume. However, the MTB cocci inhabiting the water column of Lake Pavin harbor the specific capability to store P as PolyP below the oxygen detection limit (pO2 < 0.1%). Preliminary results tend to indicate that these MTB cocci represent the major population of MTB located right under the oxic-anoxic interface, in a zone of strong chemical and redox gradients. These gradients allow the study of the impacts of varying chemical conditions on the structuration of MTB populations and on the PolyP sequestration capability of MTB cocci.

We combined a variety of methods to identify the different MTB populations as a function of the water column depth and characterize their potential biogeochemical niches.

We used a new sampling system, an online pumping system, that allowed us to reach a better spatial (vertical) resolution [4], down to 20 cm. This sampling system was coupled to the measure of the physicochemical parameters of the water column (e.g. pO2, pH, redox, conductivity, FDOM, turbidity). We were therefore able to better estimate the impact of the chemical parameters on the MTB. We then sampled the water to measure the geochemical parameters using ICP-OES and to characterize MTB via optical and electron microscopy. Optical microscopy permitted the identification of the main populations of MTB and their concentrations, while electron microscopy allowed the characterization of the different magnetosome organisation and PolyP accumulation capability. We evidenced the stratification of the two main populations of MTB sequestrating two distinct sets of elements (PolyP and counterions, or amorphous calcium carbonates, respectively) and inhabiting different niches whose specific geochemical parameters were identifies using multivariate statistics.

Different environmental conditions, such as the concentration of dissolved sulfate, are correlated to the MTB cocci abundance. Moreover, the proportion of MTB cocci accumulating PolyP is negatively correlated to the concentration of dissolved sulfur. These results bring into light the potential link between the sulfur metabolism of these bacteria and their capability to sequestrate P as PolyP. Moreover, our reccurent observations of intracellular sulfur granules suggest that this new bacterial model for P sequestration below the oxygen detection limit are sulfoxidizers,

Genomic analyses will be done in the future to allow further comprehension on molecular mecanisms and PolyP formation.

[1] Brock J, Schulz-Vogt HN. (2011) ISME Journal 5, 497-506. [2] Mubmann M et al. (2007) PLoS Biology 5(9), e230. [3] Rivas-Lamelo S et al. (2017) Geochem. Persp. Let. 5, 35–41. [4] Busigny et al., 2021 Env. Microbiol. 1462-2920 .

 

How to cite: Bidaud, C., Monteil, C. L., Menguy, N., Busigny, V., Jézéquel, D., Viollier, E., Travert, C., Skouri-Panet, F., Benzerara, K., Lefevre, C. T., and Duprat, E.: Population structure of magnetotactic bacteria forming intracellular polyphosphates in the water column of Lake Pavin, a freshwater ferruginous environment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11061, https://doi.org/10.5194/egusphere-egu21-11061, 2021.

EGU21-13910 | vPICO presentations | BG6

Investigating Fast- and Slow-settling Phosphorus Fractions in Lakes using Steady-state Modeling

Hamed Khorasani and Zhenduo Zhu

Phosphorus (P) is the key and limiting nutrient in the eutrophication of freshwater resources. Modeling P retention in lakes using steady-state mass balance models (i.e. Vollenweider-type models) provides insights into the lake P management and a simple method for large-scale assessments of P in lakes. One of the basic problems in the mass balance modeling of P in lakes is the removal of P from the lake water column by settling. A fraction of the incoming P into the lake from the watershed is associated with fast-settling particles (e.g. sediment particles) that result in the removal of that fraction of P quickly at the lake entrance. However, existing models considering a constant fraction of fast-settling TP for all lakes are shown to result in overestimation of the retention of P in lakes with short hydraulic residence time. In this study, we combine a hypothesis of the fast- and slow-settling P fractions into the steady-state mass balance models of P retention in lakes. We use a large database of lakes to calibrate the model and evaluate the hypothesis. The results of this work can be used for the improvement of the prediction power of P retention models in lakes and help to better understand the processes of P cycling in lakes.

How to cite: Khorasani, H. and Zhu, Z.: Investigating Fast- and Slow-settling Phosphorus Fractions in Lakes using Steady-state Modeling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13910, https://doi.org/10.5194/egusphere-egu21-13910, 2021.

EGU21-14068 | vPICO presentations | BG6

Phosphorus recycling and retention in Lake of the Woods: Reactive-transport diagenetic modeling across spatial and temporal Scales

Md Samrat Alam, Arthur Zastepa, and Maria Dittrich

The dynamics of sediment phosphorus (P) remobilization and recycling in many polymictic systems due to distinct external and internal loading conditions are poorly understood. Here we used a multifaceted approach of quantifying sediment P binding forms and corresponding metal contents in sediment cores down to 30 cm from 8 different locations at Lake of Woods (LOW) in different seasons. We also measured pH, redox potential and dissolved oxygen uptake across the sediment-water interface and the concentration of nutrient and metals in pore water at different depths. Additionally, we applied a reaction-transport diagenetic model to construct the spatial and temporal trend of internal P loading in response to environmental variations. The summer diffusive fluxes of P ranged between 3 and 83 µmol m-2 d-1 whereas the winter fluxes were lower ranged from 0.1 to 0.35 µmol m-2 d-1. P recycling efficiency were 13% to 77%. P bound to redox sensitive iron (Fe)-P binding forms in sediments were the major source of P release in all stations, while P immobilization is controlled by redox-insensitive calcium (Ca)-P phases. The modeling results supported the notion that P release was mostly driven by the diagenetic recycling of redox sensitive and organic bound P.

How to cite: Alam, M. S., Zastepa, A., and Dittrich, M.: Phosphorus recycling and retention in Lake of the Woods: Reactive-transport diagenetic modeling across spatial and temporal Scales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14068, https://doi.org/10.5194/egusphere-egu21-14068, 2021.

EGU21-3317 | vPICO presentations | BG6

P-TRAP – Reducing diffuse phosphorus input to surface waters

Thilo Behrends and Sylvia Walter

Phosphate (P) as an essential resource for food production is becoming scarce. Its uncontrolled loss from agricultural areas is in conflict with the principles of a circular economy. Enhanced loading of surface waters with P is the main cause for eutrophication and presents a key challenge in meeting the objectives of the EU Water Framework Directive. Understanding and controlling environmental P fluxes therefore is key to target both problems, to develop new methods and approaches to manage environmental P fluxes, and to improve surface water quality.

In March 2019 the EU Marie Sklodowska-Curie Innovative Training Network P-TRAP has been launched. P-TRAP establishes a framework of partners from multiple science and engineering disciplines. Integration of non-academic partners from various stakeholder groups into the P-TRAP consortium paves the way for direct implementation of the acquired knowledge. The project is targeting the diffuse flux of phosphate (P) into surface waters, i.e. the problems of understanding and controlling environmental P fluxes. P-TRAP aims to develop new methods and approaches to trap P in drained agricultural areas and in the sediments of eutrophic lakes. Trapping of P involves the application of iron(Fe)-containing by-products from drinking water treatment. P-TRAP aspires the ideas of a circular economy and aims at recovering the retained P in agricultural systems. Novel microbial technologies will be developed to convert P-loaded Fe-minerals into marketable fertilizers whose suitability will be evaluated. The P-TRAP technologies have in common that they rely on the naturally strong connection between P and Fe and the innovative P-TRAP strategies will be underpinned by process-orientated investigations on the behaviour of P during the transformation of Fe minerals. The latter are key in trapping and recycling of P in agricultural systems and lakes. Here we will present the structure and the planned research of the project, including a first overview of achievements of the first two years. 

How to cite: Behrends, T. and Walter, S.: P-TRAP – Reducing diffuse phosphorus input to surface waters, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3317, https://doi.org/10.5194/egusphere-egu21-3317, 2021.

EGU21-13645 | vPICO presentations | BG6

Kinetics and mechanism of phosphate release upon sulfidation of phosphate-containing lepidocrocite

Mingkai Ma, Andreas Voegelin, and Thilo Behrends

Sulfidation of Fe(III) (hydr)oxides plays an important role in the phosphate(P) cycle in oceans and lakes. P has a strong affinity to Fe(III) (hydr)oxides and can either become incorporated via coprecipitation or adsorb onto the solid’s surface. Consequently, P enters aquatic sediments often associated with Fe(III) (hydr)oxides. In the sediments, when sulfidic conditions are prevalent, the reaction of Fe(III) (hydr)oxides with sulfide can lead to the formation of Fe(II) sulfides and P release. The released P can, in turn, diffuse upwards into the overlying water and thus aggravate eutrophication in water bodies.  Although it is generally expected that P is released during the sulfidation of P containing Fe(III) (hydr)oxides, questions remain whether part of the P could be re-adsorbed onto the products of the sulfidation reaction, or trigger the formation of vivianite [1] (Fe3(PO4)2 · 8H2O). Furthermore, it is still unclear how the rates of P release are related to the progress of the sulfidation reaction.

In order to study the P dynamics during sulfidation, we performed experiments in flow-through reactors with P-bearing lepidocrocite (γ-FeOOH). The inflow solution contained sulfide and we monitored P, dissolved S(-II) and Fe(II) in the outflow to follow the progress of sulfide consumption and P release. Sulfide concentrations in the outflow of reactors containing lepidocrocite with adsorbed P tended to be lower than in the outflow of reactors with lepidocrocite but no P. Consequently, the preliminary results indicate that consumption rates of sulfide by the reaction with lepidocrocite were lower when P was present, implying that adsorbed P reduced the rates of sulfidation. At the beginning of the experiment, P concentrations in the outflow remained low, then started to increase and reached a steady state after passing several reactor volumes. This indicates that P was not instantaneously released upon sulfide adsorption but only as lepidocrocite sulfidation progressed. At the end of the experiment, the fraction of P released from the reactor was significantly lower than the fraction of lepidocrocite that had reacted with sulfide(calculated from cumulative sulfide consumption and solid phase characterization). This implies that part of the P has been retained in the solid phase despite the reductive transformation of lepidocrocite. The underlying mechanisms of P retention and the complex relationship between the rates of sulfide consumption and P release will be discussed.

References

[1] Jilbert and Slomp, 2013. Geochimica et Cosmochimica Acta 107, 155-169.

How to cite: Ma, M., Voegelin, A., and Behrends, T.: Kinetics and mechanism of phosphate release upon sulfidation of phosphate-containing lepidocrocite, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13645, https://doi.org/10.5194/egusphere-egu21-13645, 2021.

EGU21-4941 | vPICO presentations | BG6 | Highlight

Effects of Fe addition on sediment P dynamics in a eutrophic lake

Melanie Münch, Rianne van Kaam, Karel As, Stefan Peiffer, Gerard ter Heerdt, Caroline P. Slomp, and Thilo Behrends

The decline of surface water quality due to excess phosphorus (P) input is a global problem of increasing urgency. Finding sustainable measures to restore the surface water quality of eutrophic lakes with respect to P, other than by decreasing P inputs, remains a challenge. The addition of iron (Fe) salts has been shown to be effective in removing dissolved phosphate from the water column of eutrophic lakes. However, the resulting changes in biogeochemical processes in sediments as well as the long-term effects of Fe additions on P dynamics in both sediments and the water column are not well understood.

In this study, we assess the impact of past Fe additions on the sediment P biogeochemistry of Lake Terra Nova, a well-mixed shallow peat lake in the Netherlands. The Fe-treatment in 2010 efficiently reduced P release from the sediments to the surface waters for 6 years. Since then, the internal sediment P source in the lake has been increasing again with a growing trend over the years.

In 2020, we sampled sediments at three locations in Terra Nova, of which one received two times more Fe during treatment than the other two. Sediment cores from all sites were sectioned under oxygen-free conditions. Both the porewaters and sediments were analysed for their chemical composition, with sequential extractions providing insight into the sediment forms of P and Fe. Additional sediment cores were incubated under oxic and anoxic conditions and the respective fluxes of P and Fe across the sediment water interface were measured.

The results suggest that Fe and P dynamics in the lake sediments are strongly coupled. We also find that the P dynamics are sensitive to the amount of Fe supplied, even though enhanced burial of P in the sediment was not detected. The results of the sequential extraction procedure for P, which distinguishes P associated with humic acids and Fe oxides, as well as reduced flux of Fe(II) across the sediment water interface in the anoxic incubations, suggest a major role of organic matter in the interaction of Fe and P in these sediments.

Further research will include investigations of the role of organic matter and sulphur in determining the success of Fe-treatment in sequestering P in lake sediments. Based on these data in combination with reactive transport modelling we aim to constrain conditions for successful lake restoration through Fe addition.

How to cite: Münch, M., van Kaam, R., As, K., Peiffer, S., ter Heerdt, G., Slomp, C. P., and Behrends, T.: Effects of Fe addition on sediment P dynamics in a eutrophic lake, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4941, https://doi.org/10.5194/egusphere-egu21-4941, 2021.

EGU21-6188 | vPICO presentations | BG6 | Highlight

Investigating methods of phosphorus recovery from eutrophic lakes through hypolimnetic withdrawal and purification

Soila Silvonen, Juha Niemistö, Jerry Myyryläinen, Simo Huotari, Leena Nurminen, Jukka Horppila, and Tom Jilbert

As global reserves of phosphorus (P) become scarce, recycling of P will be key to sustainable food production in future. The hypolimnetic withdrawal and purification circuit (HWPC) is a novel method that aims to remove and capture P accumulated in the near-bottom water of eutrophic lakes. Similar to the basic principle of wastewater treatment, the lake water is treated for the precipitation of P and other elements, and the formed particles are collected in a filtering unit while the purified water flows back into the lake. The method has been tested in a pilot project at Lake Kymijärvi, southern Finland.

In the current study, we observed the efficiency of three different water treatments in the HWPC in terms of P precipitation: 1) water aeration; 2) aeration + Ca(OH)2 addition; 3) aeration + tannin-based biopolymer addition. Moreover, we studied the chemical composition of the precipitate formed in each treatment to understand its potential for P recycling. The aim of the study was to provide a better understanding to further develop and apply techniques to recover and recycle P from eutrophic lakes.

How to cite: Silvonen, S., Niemistö, J., Myyryläinen, J., Huotari, S., Nurminen, L., Horppila, J., and Jilbert, T.: Investigating methods of phosphorus recovery from eutrophic lakes through hypolimnetic withdrawal and purification, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6188, https://doi.org/10.5194/egusphere-egu21-6188, 2021.

EGU21-13281 | vPICO presentations | BG6

Effects of aging and transformation of Fe(III)-precipitates on the retention of co-precipitated phosphate

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

The cycling of phosphorus in terrestrial and aquatic systems is tightly coupled to the redox-cycling of iron (Fe). The oxidation of dissolved Fe(II) in natural waters leads to the precipitation of amorphous to poorly crystalline Fe(III)-solids that can bind phosphate (P) and other nutrients as well as toxic compounds. The EU project P-TRAP is aimed at developing methods to reduce diffuse P inputs into surface waters to mitigate eutrophication, by using Fe-rich byproducts from water treatment (https://h2020-p-trap.eu/). Within this project, we study mechanistic aspects of the formation and transformation of P-containing Fe(III)-precipitates and their implications for P retention in soils and water filters.

Freshly formed Fe(III)-precipitates are metastable and can transform into more stable phases over time. This may lead to the release of co-precipitated P. In laboratory experiments, we assessed how Ca, Mg, silicate (Si) and P impact on the formation and transformation of Fe oxidation products (at 0.5 mM Fe) and their P retention in synthetic bicarbonate-buffered groundwater. The time-resolved experiments were performed in electrolyte solutions containing Na, Ca, or Mg as electrolyte cation, without or with Si (at molar Si/Fe of 1), and P (P/Fe of 0.3 and 0.05). Changes in dissolved element concentrations over time were linked to changes in the structure and composition of the Fe(III)-solids; with Fe coordination probed by X-ray absorption spectroscopy, mineralogy by X-ray diffraction, and nano-scale morphology and composition heterogeneity by transmission electron microscopy with energy-dispersive X-ray detection.

The freshly-formed Fe(III)-precipitates were mixtures of amorphous Fe(III)-phosphate with either poorly-crystalline lepidocrocite (without Si) or Si-containing ferrihydrite (with Si). Increases in dissolved P during aging were largest in Na electrolytes without Ca, Mg or Si, and were linked to the transformation of amorphous Fe(III)-phosphate into lepidocrocite with a lower P retention capacity than Fe(III)-phosphate. In Ca- and to a lesser extent Mg-containing electrolytes, the Ca or Mg stabilized the amorphous Fe(III)-phosphate and thereby reduced P release over time. The presence of Si increased initial P uptake and inhibited P release during aging by causing the formation of Si-ferrihydrite with higher P sorption capacity than lepidocrocite formed in the absence of Si. In conclusion, the extents to which P is trapped by fresh Fe(III)-precipitates and released during aging can be attributed to the individual and coupled impacts of Ca, Mg and Si on Fe(III)-precipitate structure, stability and transformation.

In continuing work, we aim to expand our work to study how organic compounds impact on the formation and colloidal stability of Fe(III)-precipitates and P retention.

How to cite: Nenonen, V., Kaegi, R., Hug, S. J., Mangold, S., Göttlicher, J., Winkel, L., and Voegelin, A.: Effects of aging and transformation of Fe(III)-precipitates on the retention of co-precipitated phosphate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13281, https://doi.org/10.5194/egusphere-egu21-13281, 2021.

EGU21-2716 | vPICO presentations | BG6

PO4 recovery using mixtures of biochar and carbonate materials

Carlotta Carlini, Antonio Primante, Nicolas Greggio, Enrico Balugani, Andrea Contin, and Diego Marazza

The recovery of PO4 from wastewaters by using biochar proves not to be completely satisfactory. The surface of the biochar is typically negatively charged, which prevents the adsorption of PO4. For this reason, mixtures of biochar and natural carbonate materials have been tested as a novel sorbent material for PO4 recovery from both synthetic-and waste- water. The goal of the research is to obtain a PO4 based complex starting from natural second-generation materials such as food industry byproducts, plants and other residues to prepare fertilisers compliant to the component material category CMC 6 defined in the Regulation (EU) 2019/1009/EU It has to be noted that natural carbonate materials are not pure CaCO3, but present small impurities that contribute to modify their properties. Therefore, the use of carbonate materials obtained from different sources can lead to different performances when it comes to PO4 removal from wastewaters.

In this work we present results of PO4 removal obtained from a mixture of biomass and different carbonate materials. The mixture has been treated through a specific thermal protocol to obtain two different calcium-oxide rich charcoals here named composites C1 and C2. Initially, each composite was added to synthetic waters with different PO4 concentration, with a composite:water ratio of 1:1000. The initial concentrations of PO4 were 10, 100 and 1000 mg/l. After treatment with the composite, regardless of whether C1 or C2 was used, the PO4 concentration in the waters with initial concentration of 10 and 100 mg/L was nearly zero, with pH values at equilibrium around 11.9. The treatment of the water with initial PO4 concentration of 1000 mg/l shows a reduction of 20% and 40% with C1 and C2, respectively, with final pH values around 7.8.

After addition of the composites to the water, the solutions present very high pH values except for the water with the highest concentration. Although this is an optimal situation for the removal of PO4, it leads to two problems. First, the filtered water is not suitable for direct disposition in sewers, since the pH is higher than the limit established by the wastewater legislation (9.5). Second, a pH value larger than 9 determines the precipitation of PO4 regardless of the presence of the composite, which suggests that the PO4 is not adsorbed by the composites, thus not leading to the desired complex

In order to quantify the exact amount of PO4 adsorbed by the composite, the experiments have been repeated under controlled pH, keeping it around a value of 7 by the use of a mild acid. In this condition, after 1h treatment, 50% of phosphate was removed and bound to the composite

The work intends to present the results at laboratory scale and next steps at higher TRL.

How to cite: Carlini, C., Primante, A., Greggio, N., Balugani, E., Contin, A., and Marazza, D.: PO4 recovery using mixtures of biochar and carbonate materials, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2716, https://doi.org/10.5194/egusphere-egu21-2716, 2021.

EGU21-12798 | vPICO presentations | BG6

Biogeochemical mechanisms influencing the bioavailability of P and Fe from vivianite

Rouven Metz, Naresh Kumar, Walter Schenkeveld, and Stephan Kraemer

The vital element phosphorus (P) invokes two extremes in the environment; (i) scarcity, as a non-renewable resource and as a poorly bioavailable limiting nutrient for plants, and (ii) excess, as cause of eutrophication in surface waters. To tackle both these problems, the inter-relationship between the P and the iron (Fe) cycle is widely discussed with a special interest in the ferrous iron-phosphate mineral vivianite (Fe(II)3(PO4)2*8H2O). Vivianite forms naturally in sub-/anoxic environments with high Fe(II) and PO4 concentrations, and is a sink to the dissolved P concentration. On the other hand, vivianite has been proposed as a P source through application as a slow-release Fe-P fertilizer prepared from recycled P. However, vivianite is a metastable mineral under oxic conditions; it readily oxidizes, notably changing color from white to dark blue/purple. This transformation changes the properties of the mineral (surface), and thus its suitability as a fertilizer.

We investigated the oxidation and dissolution of vivianite under different environmental conditions with the aim of developing a mechanistic and kinetic model that relates the oxidation process with dissolution rates.  Moreover, the effect of secondary mineral precipitation on the ‘net’ availability of P and Fe for soil organisms was also studied. Quantifying dissolution rates and secondary mineral formation under environmentally relevant conditions provides the fundamental knowledge needed to assess the suitability of vivianite as Fe and P fertilizer. This information is also paramount to the idea of a circular economy concept: starting with the reduction of P loads of (waste) waters and using the byproduct vivianite as P source for fertilization.

How to cite: Metz, R., Kumar, N., Schenkeveld, W., and Kraemer, S.: Biogeochemical mechanisms influencing the bioavailability of P and Fe from vivianite, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12798, https://doi.org/10.5194/egusphere-egu21-12798, 2021.

EGU21-16487 | vPICO presentations | BG6

Soil phosphorus, biology and time: A case for publishing inconclusive data, and the undeniable relevance of tennis balls

Phil Haygarth, Malika Mezeli, Timothy George, Roy Neilson, and Martin Blackwell

EGU21-16486 | vPICO presentations | BG6

Biosolids Incorporation in Mediterranean Soils Increase Phosphate Adsorption

Yaniv Freiberg, Pinchas Fine, Michael Borisover, and Shahar Baram

Contradictory data exists on the impact of biosolids incorporation on ortho-phosphate (IP) binding to arid and semi-arid Mediterranean soils. We used two mature organic amendments (OA) with low IP solubility to study the effect of OAs addition on the IP adsorption parameters of Mediterranean soils. Seven soils, encompassing a wide range of mechanical, chemical and mineralogical properties, were mixed with a biosolids compost (DSC) at 9:1 ratio (w/w dry weight basis). The soils and mixtures were either incubated for seven years under constant temperature (30℃) and moisture content (80% of 30 kPa tension) or were unincubated. IP adsorption parameters were also measured in not-incubated soil DSC mixtures at 97:3 ratio. In all the soils, DSC addition significantly increased the IP adsorption capacities (by Langmuir's model) from 126 to 397 mg IP kg-1 in the soils to 254 through 669 mg IP kg-1 in the soil-DSC-mixtures. The increased capacities were accompanied by a significant decrease in the adsorption affinities, from values of 0.12 to 1.02 L kg-1 in the soils to 0.05 and 0.25 L kg-1 in the mixtures. Biosolids addition at 97:3 ratio had a similar effect on the IP adsorption parameters as the 9:1 ratio. These two IP adsorption parameters continued to change along the incubation. The other OA tested was a municipal solid waste compost (MSWC), which was mixed with two montmorillonitic soils at 97:3 ratio (soil:OA), one with high lime and low Al/Fe-oxides contents and the other with low lime and high Al/Fe-oxides content. OA addition increased the IP adsorption capacity in the lime-rich soil, while it did not affect the other. Overall, our results show that the solid matrix of the two OA's used by us embodied IP adsorption sites, most likely through metal bridging with Ca2+, which increases the total adsorption capacity of the soil-OA mixture. Concomitantly, DOM from the OAs competes with IP on adsorption sites reducing the soil's adsorption capacity. The magnitude of each one of these two processes depends on the soil and the added OA characteristic and will determine the overall change in the soil's capability to retain IP after biosolids incorporation.

 

How to cite: Freiberg, Y., Fine, P., Borisover, M., and Baram, S.: Biosolids Incorporation in Mediterranean Soils Increase Phosphate Adsorption, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16486, https://doi.org/10.5194/egusphere-egu21-16486, 2021.

Understanding how the solubility of forms of inorganic and organically-complexed phosphorus (P) in agricultural soil is affected by inputs of organic matter (OM) could inform decisions on sustainable future farming practices. Different forms of OM provide organic P, carbon (C) and other nutrients to the system at different rates, depending upon their recalcitrance to decomposition, and the stoichiometric balance of elements between soil, OM amendment and microbial requirements.

 

We describe an 18-month pot experiment that tested the hypothesis that additions of organic matter will affect the solubility of P forms in soil. Mesocosms (~30 kg soil) of two agricultural top-soils, of moderate and low P availability, were amended with a commercial humic soil amendment (lignite) or crop residue (barley straw) at two addition levels. Treatments with/without chemical P fertilizer were superimposed on OM treatments. The system was planted with Lolium perenne (perennial rye grass) and exposed to a natural rain and temperature regime. Leachate was collected and analyzed for soluble P, nitrogen and dissolved organic C (DOC) at 6 weekly intervals in order to investigate solubility over time. Destructive sampling at the end of the experiment yielded plant and soil samples for comparison of C, N and P stoichiometry between the treatments.

 

Initial results showed increases in leachate DOC relating to crop residue OM treatments and a positive effect of P fertilizer on plant biomass in the low P soil. Concentrations of dissolved P in leachate were higher in the moderately P-sorbing soil compared to the highly P-sorbing soil. Ongoing analysis includes measures of biological activity including soil microbial biomass C, N and P by fumigation-extraction and soil phosphatase activity. Chemical measures include total C, N and P, soil carbon forms using Fourier-transform infrared spectroscopy (FTIR), total organic P and water and acid ammonium oxalate extractions. Interpretation of the final results will consider how the release of C and nutrients from OM and their subsequent impact on the system, are controlled by microbial activity and macronutrient stoichiometry. These results should help to inform future research into improving P utilization in agriculture through balancing nutrient ratios to regulate nutrient cycling. Such research seeks to improve agronomic P efficiencies alongside wider benefits associated with the drive to increase soil C.

How to cite: Tweedie, A., Haygarth, P. M., and Stutter, M.: Is the solubility of inorganic and organically complexed phosphorus in agricultural soils affected by chemical fertilizer and organic carbon additions?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7075, https://doi.org/10.5194/egusphere-egu21-7075, 2021.

Phosphorus solubilisation with varying drying and rewetting stresses under four contrasting soils from different regions of China  

Nyamdavaa Mongol1, Jianbo Shen2, Philip M. Haygarth1  

  

1Lancaster Environment  Centre, Lancaster University, Lancaster, LA1 4YW, United Kingdom.  

2Department of Plant Nutrition, China Agriculture University, Key Laboratory of Plant-Soil Interactions, Beijing 100193, PR China  

  

Abstract 

We tested the hypothesis that agricultural soils with a recent history of drying and rewetting (DRW) can trigger phosphorus (P) solubilisation in the rhizosphere, with a subsequent growth response of maize (Zea mays). Specifically, it aimed at investigating a possible delayed effect of DRW stresses on the soils by studying the relationship between P solubilisation in the rhizosphere, plant P acquisition and performance, and root growth under different types of agricultural soils with the previous history of a series of DRW events. The soils were collected from four different agricultural regions of China, Shandong, Chongqing, Heilongjiang and Beijing (sieved <2 mm), and then treated with four varying cycles of DRW events prior to the experiment to raise levels of soil biotic and abiotic activities. A controlled pot experiment was conducted in order to establish the Olsen’s P concentration in the soil, maize shoot P concentrations, root morphology and other rhizosphere parameters, for a duration of 43 days after planting. The results show a positive relationship between plant biomass, plant P concentration and Olsen`s P. The effect was most clearly demonstrated by the level of plant growth and their biological performance in the rhizosphere, as the plants responded better in the soil with a DRW background than to a soil that did not have a history of DRW in the past. Notably, the most positive results were obtained from the Haplic Phaeozems soil of Heilongjiang, leading to an acceptance of the hypothesis. However, the soluble P concentration and plant growth response varied depending on P application rates and soil types.  

 

How to cite: Mongol, N.: Phosphorus solubilisation with varying drying and rewetting stresses under four contrasting soils from different regions of China , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13596, https://doi.org/10.5194/egusphere-egu21-13596, 2021.

EGU21-15873 | vPICO presentations | BG6 | Highlight

Time to re-think agricultural phosphorus modelling for the 2020s  

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

Phosphorus (P) is critical to our food production systems with many crop systems dependent on continual inputs to meet yield demands. However, a consequence of the widespread application of P to agricultural soils in the past 60 years has led to concerns about the long-term sustainability of P fertiliser supply and to P being transferred from soil systems to watercourses, causing diffuse pollution. This highlights the multi-scaled and interdisciplinary nature of the past, present and future of P management.  

The aim of this research is to define a starting framework to consider the best ways to develop a model that addresses the contemporary understanding of P processes, integrating the needs of the crop, with biogeochemical and hydrological modelling considerations, going beyond P transfer to the role of P in both food and water challenges.  

So, this review explores some of the current P models and the future opportunities for expanding their representation of P processes in agricultural systems. This goes beyond nesting existing models and reshapes approaches to posing research and modelling questions to achieve P models that cross disciplinary boundaries and have meaning and usability in practice. As part of this contribution, we welcome modellers and P scientists to come forward and help drive this complex issue of P in agriculture. 

How to cite: Davies, J. M., Janes-Bassett, V., Blackwell, M., Burgess, A., Davies, J., and Haygarth, P. M.: Time to re-think agricultural phosphorus modelling for the 2020s  , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15873, https://doi.org/10.5194/egusphere-egu21-15873, 2021.

EGU21-3037 | vPICO presentations | BG6

Integrated carbon-nitrogen-phosphorus cycling for sustainable agriculture – a knowledge gap and investigation of the role of phosphatase enzymes

Victoria Janes-Bassett, Phil Haygarth, Martin Blackwell, Malika Mezeli, Gavin Stewart, Gordon Blair, and Jess Davies

Phosphorus is closely linked to other nutrient cycles, notably carbon and nitrogen, therefore, to understand potential risks to food production models are required that simulate integrated nutrient cycling over long timescales. The soil-plant system model N14CP meets these requirements and simulates both semi-natural and agricultural environments. N14CP has been validated both spatially and temporally across a range of long-term agricultural experimental sites comparing soil C, N and P, and crop yields, and in most instances performs well. However, under experimental conditions where N is applied in the absence of P, the model indicates exhaustion of P reserves and a decline in yields that is not observed at these sites, highlighting a gap in the model process representation. Potential sources of this ‘missing P’ such as enhanced atmospheric deposition, weathering and flexible plant stoichiometries were explored yet cannot account for this deficit. We hypothesise that access of organic P through other mechanisms not fully represented within the model, such as phosphatase enzymes, could be part of this explanation.

In order to test this, we conducted a meta-analysis of phosphatase enzyme activity in agricultural settings, comparing response to P sufficient and deficient conditions. Results suggest phosphatase enzyme activity is higher in P deficient conditions compared to inorganic P addition, yet lower compared to organic P addition. Meta-regression analysis indicates magnitude of P addition and pH of substrate are significant factors influencing enzyme response. However, due to numerous additional processes and adaption strategies in response to P deficiency and the difficulty isolating the role of phosphatase enzymes it is not possible to determine the degree to which this mechanism alone accounts for the missing P. We discuss the continuing need for additional empirical evidence to understand the cycling of organic P, and the development of models to include these processes to inform sustainable land management and ensure long-term food security.

How to cite: Janes-Bassett, V., Haygarth, P., Blackwell, M., Mezeli, M., Stewart, G., Blair, G., and Davies, J.: Integrated carbon-nitrogen-phosphorus cycling for sustainable agriculture – a knowledge gap and investigation of the role of phosphatase enzymes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3037, https://doi.org/10.5194/egusphere-egu21-3037, 2021.

EGU21-3071 | vPICO presentations | BG6

Phosphorus in Aeolian desert dust deposits can be captured, dissolved, and absorbed by plant leaves

Ran Erel, Sudeep Tiwari, Ilana Shtein, and Avner Gross

Phosphorus (P) limitation is prevalent around the world,primarily because most soil P have low bioavailability. In P poor ecosystems, deposition of P-rich desert dust is recognized as a major component of the P cycle. The acknowledged paradigm is that plants acquire P deposited in soil primarily via their roots. We tested whether, and to what extent, plants acquire P directly from dust deposited on their leaves and what are the underlining uptake mechanisms of insoluble P. P-rich dust was applied to P sufficient and P deficient chickpea, maize and wheat plants and was compared to plants which received inert silica powder. Foliar application of dust doubled the growth of P stressed chickpea and wheat, two crops originating near the Syrian Desert. P deficiency enhanced the acquisition of insoluble P through series of leaf modifications that increased foliar dust capture, acidified the leaf surface and, in chickpea, enhanced exudation of P-solubilizing organic acids. In in-situ trials, we demonstrated that the modifications of leaf pH and exudation of oxalic and malic acids substantially promoted P solubilisation from dust.  Foliar responses did not occur in maize and in P sufficient plants which displayed only a marginal response to dust. Our results demonstrate that foliar uptake of P from dust can be an alternative P acquisition pathway in P-deficient plants. Interestingly, the abovementioned foliar responses are comparable to known P uptake root responses. Given that P limitation is almost universal, foliar P uptake pathway will have significant ecological and agricultural implications.

How to cite: Erel, R., Tiwari, S., Shtein, I., and Gross, A.: Phosphorus in Aeolian desert dust deposits can be captured, dissolved, and absorbed by plant leaves, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3071, https://doi.org/10.5194/egusphere-egu21-3071, 2021.

EGU21-10508 | vPICO presentations | BG6

Phosphorus limit to the CO2 fertilization effect in tropical rainforests as informed from a coupled biogeochemical model

Zhuonan Wang, Hanqin Tian, Shufen Pan, Hao Shi, Jia Yang, Latif Kalin, Christopher Anderson, and Naishen Liang

Tropical rainforests play an important role in sequestering carbon (C) and mitigating climate warming. Many terrestrial biosphere models (TBMs) estimate productivity increase in tropical rainforests due to the CO2 fertilization effect. However, most TBMs neglect phosphorus (P) limitation on tropical rainforest productivity. Here, we used a process-based Dynamic Land Ecosystem Model with coupled C-N-P dynamics (DLEM-CNP) with varied Vcmax­25 to examine how P limitation has affected C fluxes of tropical rainforests to environmental and anthropogenic factors, including N deposition, land-use changes, climate variability, and atmospheric CO2, during 1860-2018. The model results showed that consideration of the P cycle reduced the response of tropical rainforests gross primary production (GPP) by 25% and 39%, net primary production (NPP) by 25% and 43%, and net ecosystem production (NEP) by 21% and 41% to the CO2 fertilization effect relative to CN-only and C-only models. The DLEM-CNP estimated that the tropical rainforests had a GPP of 41.1 + 0.5 Pg C year-1, NPP of 19.7 + 0.3 Pg C year-1 and NEP of 0.44 + 0.34 Pg C year-1 under 1860-2018 environmental conditions. Factorial experiments with DLEM-CNP suggested that deforestation has stronger impacts on GPP and NPP reduction compared to the enhanced GPP and NPP benefiting from the CO2 fertilization effect. Additionally, tropical rainforests NEP showed a continuously increasing trend owing to the CO2 fertilization effect. Our study highlights the importance of P limitation on the C cycle and the weakened CO2 fertilization effect due to nutrients limitation in the tropical rainforests.

How to cite: Wang, Z., Tian, H., Pan, S., Shi, H., Yang, J., Kalin, L., Anderson, C., and Liang, N.: Phosphorus limit to the CO2 fertilization effect in tropical rainforests as informed from a coupled biogeochemical model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10508, https://doi.org/10.5194/egusphere-egu21-10508, 2021.

BG10 – Hydrocarbon seepage – from past records to modern examples and models to evaluate the future

EGU21-480 | vPICO presentations | BG10

Methane emission from seeps of West Siberian middle taiga river floodplains

Aleksandr Sabrekov, Irina Terentieva, Yuriy Litti, Mikhail Glagolev, and Ilya Filippov

Natural gas seepage is considered as a strong methane source influencing future climate predictions and creating local fire and explosion hazards. Recently numerous methane seeps were found in West Siberian middle taiga (WSMT) river floodplains. Seepage occurs in unvegetated spots and areas of saturated quicksand deposits and in the bottom of river stream beds. Based on location and size seeps found in WSMT can be classified in three groups: 1) single seeps and seep puddles away from river stream bed, 2) seep chains along the river streams, including seeps inside stream bed, 3) seep fields with numerous holes, funnels and craters with area up to several thousands m2. Origin of methane in these seeps is still not fully understood and methane emission from them is also not quantified. We aimed to fill these gaps during 2019-2020 August-September field campaigns.

To reveal the origin of seeping gas hydrocarbons concentration, methane carbon and hydrogen stable isotope ratios and methane radiocarbon concentration were measured in a gas sampled throughout the study region (250 km in north-south and 400 km in east-west directions). To compare characteristics of methane from seeps and from wetlands gas dissolved in wetland pore water and peat for incubation studies were sampled on a depth of 1-2 m in three representative bogs near seeps. During anaerobic peat incubation the dynamics of methane (including carbon stable isotope ratios), hydrogen, carbon dioxide and low-molecular fatty acids concentrations were monitored. Methane emission was estimated in the same three bogs using both static chamber method (provided a benchmark) and ecosystem-scale inverse modelling (backward Lagrangian simulation).

Obtained data indicate modern biogenic origin for the methane seeping in WSMT. Similarity in isotope signatures between methane from wetlands and seeps suggests lateral transport of methane through groundwater from raised bogs to seeps in floodplains. Methane produced in the upper layer of raised bogs emits to the atmosphere mainly through the root transport while in deeper layers vertical methane migration is limited. Raised bogs are widely developed in WSMT and cover about half of the total region area. We conclude that methane seeping observed in WSMT floodplains is caused by the lateral groundwater transport downward from the watershed to the floodplain.

Methane emission estimates for three seep fields made by chamber method and inverse modelling were in a good correspondence, although inverse modelling fluxes are 20-40% higher. Methane flux for investigated fields ranges from tens to hundreds mgCH4·m-2·h-1 with a strong difference (up to order of magnitude) between different fields.

This study improves understanding of the insufficiently investigated element of the methane biogeochemical cycle – transport through the groundwater when methane avoids oxidation in the unsaturated surface layer of the wetland. Emission from seeps can make a valuable contribution to the regional methane flux. Potential reaching of a lower explosive limit for methane concentration should be taken into account during planning of groundwater use.

This study was supported by a grant of the Russian Science Foundation (№ 19-77-10074).

How to cite: Sabrekov, A., Terentieva, I., Litti, Y., Glagolev, M., and Filippov, I.: Methane emission from seeps of West Siberian middle taiga river floodplains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-480, https://doi.org/10.5194/egusphere-egu21-480, 2021.

Gas-charged sediments of shallow water bodies are significant sources of atmospheric methane, an important greenhouse gas. Past accounts of gas bubbles developed in shallow aquatic sediments (and in their surrogates) have reported a controversial occurrence of vertical as well as horizontal bubbles topologies. Within the framework of tensile fracturing of muddy sediment produced by the growing bubbles, the vertical orientation of bubbles is well understood, however factors controlling horizontal bubble growth are largely unclear. This study is conducted by employing a mechanical/reaction–transport numerical model, which couples diffusion-led expansion of gas bubble and elastic-fracture mechanical response of sediment to its growth. Muddy sediment is assumed to exhibit a transverse anisotropy in fracture toughness (a property describing an easiness of breaking the inter particle bonds), attributed to partial or full alignment of plate-like clay particles. Our results demonstrate that bubbles growing in isotropic sediment develop a vertically oriented topology and start their ascent once reaching their mature sizes. Under an increasing measure of anisotropy, the bubbles grow horizontally at the initial stages, however at later stages they start evolving in vertical direction as well, under influence of gravity, and eventually initiate their vertical ascent as well. Our results suggest an explanation of apparent conundrum about preferred orientations of bubbles in muddy sediments. Laterally growing bubbles produced in anisotropic sediment are able to coalesce with neighboring ones and form interconnected permeable horizontal gas networks, as observed in some lab experiments. For the first time, our results reveal that anisotropy-led initial lateral bubble growth can also play a crucial role in accumulating gas reserve from long distances around large and small scale seeps and outlets, at continental margins and inland water bodies sediments. Additionally, horizontal bubbles tend to be stationary (in contrast to the vertical bubbles) thus being responsible for high gas storage (or retention) capability of aquatic sediments.

How to cite: Painuly, A. and Katsman, R.: Influence of anisotropy in sediment mechanical properties on CH4 bubble growth topology and migration pattern in muddy aquatic sediments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-583, https://doi.org/10.5194/egusphere-egu21-583, 2021.

EGU21-963 | vPICO presentations | BG10

Meiobenthos as indicator of gaseous hydrocarbons reservoirs existing under the seabed of the Black Sea

Valentina Yanko, Anna Kravchuk, Irina Kulakova, and Tatiana Kondariuk

This presentation represents a case study that reviews research into the relationship between meiobenthos distribution and concentrations of hydrocarbon gases (HG), primarily methane, in the sediments of the northwestern part of the Black Sea, including gases released by mud volcanoes and gas seeps. Evidence forming the basis of this research comes from meiobenthos here represented by 29 species of benthic foraminifers, 7 species of ostracods, and 44 species of nematodes. The potential use of these meiobenthic organisms as indicators of gaseous hydrocarbons reservoirs existing under the seabed is evaluated according to two linked axes, namely the dual analysis of abiotic factors (physical and chemical parameters of the water column, gasmetrical, geochemical, lithological, and mineralogical properties of the sediments) and biotic characteristics (quantitative and taxonomic composition of foraminifers, nematodes, and ostracods). Studies of this kind have been directed toward developing interdisciplinary methods to improve the search for HG accumulations, especially methane, under the seabed. Development of such methods might have substantial socio-economic importance for the economy of Ukraine as well as that of other Black Sea countries, and such methods might also contribute to the sustainable development of Black Sea ecosystems.

How to cite: Yanko, V., Kravchuk, A., Kulakova, I., and Kondariuk, T.: Meiobenthos as indicator of gaseous hydrocarbons reservoirs existing under the seabed of the Black Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-963, https://doi.org/10.5194/egusphere-egu21-963, 2021.

EGU21-1807 | vPICO presentations | BG10

Mathematical model of a non-stationary process of accumulation of gas hydrates, confined to deep-water mud volcanoes

Alexey L. Sobisevich, Elena I. Suetnova, and Ruslan A. Zhostkov

Large amounts of methane hydrate locked up within marine sediments are associated to mud volcanoes. We have investigated by means of mathematical modeling the unsteady process of accumulation of gas hydrates associated with the processes of mud volcanism. A mathematical model has been developed. The system of equations of the model describes the interrelated processes of filtration of gas-saturated fluid, thermal regime and pressure, and accumulation of gas hydrates in the seabed in the zone of thermobaric stability of gas hydrates. The numerical simulation of the accumulation of gas hydrates in the seabed in the deep structures of underwater mud volcanoes has been carried out using the realistic physical parameters values. The influence of the depth of the feeding reservoir and the pressure in it on the evolution of gas hydrate accumulations associated with deep-sea mud volcanoes is quantitatively analyzed. Modeling quantitatively showed that the hydrate saturation in the zones of underwater mud volcanoes is variable and its evolution depends on the geophysical properties of the bottom environment (temperature gradient, porosity, permeability, physical properties of sediments) and the depth of the mud reservoir and pressure in it. The volume of accumulated gas hydrates depends on the duration of the non-stationary process of accumulation between eruptions of a mud volcano. The rate of hydrate accumulation is tens and hundreds times the rate of hydrate accumulation in sedimentary basins of passive continental margins.

How to cite: Sobisevich, A. L., Suetnova, E. I., and Zhostkov, R. A.: Mathematical model of a non-stationary process of accumulation of gas hydrates, confined to deep-water mud volcanoes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1807, https://doi.org/10.5194/egusphere-egu21-1807, 2021.

EGU21-5628 | vPICO presentations | BG10

Wintertime Methane Emission From the Barents and Kara Seas and Sea of Okhotsk: Satellite Evidence.

Leonid Yurganov, Dustin Carroll, Andrey Pnyushkov, Igor Polyakov, and Hong Zhang

Existence of strong seabed sources of methane, including gas hydrates, in the Arctic and sub-Arctic seas with proven oil/gas deposits is well documented. Enhanced concentrations of dissolved methane in deep layers are widely observed. Many of marine sources are highly sensitive to climate change; however, the Arctic methane sea-to-air flux remains poorly understood: harsh natural conditions prevent in-situ measurements during winter. Satellite remote sensing, based on terrestrial outgoing Thermal IR radiation measurements, provides a novel alternative to those efforts. We present year-round methane data from 3 orbital sounders since 2002. Those data confirm that negligible amounts of methane are fluxed from the seabed to the atmosphere during summer. In summer, the water column is strongly stratified from sea-ice melt and solar warming. As a result, ~90% of dissolved methane is oxidized by bacteria. Conversely, some marine areas are characterized by positive atmospheric methane anomalies that begin in November. During winter, ocean stratification weakens, convection and winter storms mix the water column efficiently. We also find that the amplitudes of the seasonal cycles over Kara and Okhotsk Seas have increased during last 18 years due to winter concentration growth. There may be several factors responsible for sea-air flux: growing emission from clathrates due to warming, changes in methane transport from the seabed to the surface, changes in microbial oxidation, ice cover, etc. Finally, methane remote sensing results are compared to available observations of temperature in deep ocean layers, estimates of Mixed Layer Depth, and satellite microwave sea-ice cover measurements.

 

How to cite: Yurganov, L., Carroll, D., Pnyushkov, A., Polyakov, I., and Zhang, H.: Wintertime Methane Emission From the Barents and Kara Seas and Sea of Okhotsk: Satellite Evidence., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5628, https://doi.org/10.5194/egusphere-egu21-5628, 2021.

EGU21-2545 | vPICO presentations | BG10

Leaky salt: pipe trails record the history of cross-evaporite fluid escape in the northern Levant Basin, Eastern Mediterranean

Davide Oppo, Sian Evans, Christopher A-L Jackson, David Iacopini, SM Mainul Kabir, and Vittorio Maselli

Hydrocarbon escape systems can be regionally active on multi-million-year timescales. However, reconstructing the timing and evolution of repeated escape events can be challenging because their expression may overlap in time and space. In the northern Levant Basin, eastern Mediterranean, distinct fluid escape episodes from common leakage points formed discrete, cross-evaporite fluid escape pipes, which are preserved in the stratigraphic record due to the coeval Messinian salt tectonics.

The pipes consistently originate at the crest of prominent sub-salt anticlines, where thinning and hydrofracturing of overlying salt permitted focused fluid flow. Sequential pipes are arranged in several kilometers-long trails that were progressively deformed due to basinward gravity-gliding of salt and its overburden. The correlation of the oldest pipes within 12 trails suggests that margin-wide fluid escape started in the Late Pliocene/Early Pleistocene, coincident with a major phase of uplift of the Levant margin. We interpret that the consequent transfer of overpressure from the deeper basin areas triggered seal failure and cross-evaporite fluid flow. We infer that other triggers, mainly associated with the Messinian Salinity Crisis and compressive tectonics, played a secondary role in the northern Levant Basin. Further phases of fluid escape are unique to each anticline and, despite a common initial cause, long-term fluid escape proceeded independently according to structure-specific characteristics, such as the local dynamics of fluid migration and anticline geometry.

Whereas cross-evaporite fluid escape in the southern Levant Basin is mainly attributed to the Messinian Salinity Crisis and compaction disequilibrium, we argue that these mechanisms do not apply to the northern Levant Basin; here, fluid escape was mainly driven by the tectonic evolution of the margin. Within this context, our study shows that the causes of cross-evaporite fluid escape can vary over time, act in synergy, and have different impacts in different areas of large salt basins.

How to cite: Oppo, D., Evans, S., Jackson, C. A.-L., Iacopini, D., Kabir, S. M., and Maselli, V.: Leaky salt: pipe trails record the history of cross-evaporite fluid escape in the northern Levant Basin, Eastern Mediterranean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2545, https://doi.org/10.5194/egusphere-egu21-2545, 2021.

EGU21-8529 | vPICO presentations | BG10

Gas hydrate destabilization and sea-level changes: insights from Miocene seep carbonate deposits of the northern Apennines (Italy)

Daniela Fontana, Stefano Conti, Chiara Fioroni, and Claudio Argentino

The effects of global warming on marine gas hydrate stability along continental margins is still unclear and discussed within the scientific community. Long-term datasets can be obtained from the geological record and might help us better understand how gas-hydrate reservoirs responds to climate changes. Present-day gas hydrates are frequently associated or interlayered with authigenic carbonates, called clathrites, which have been sampled from many continental margins worldwide. These carbonates show peculiar structures, such as vacuolar or vuggy-like fabrics, and are marked by light δ13C and heavy δ18O isotopic values. Evidences of paleo-gas hydrate occurrence are recorded in paleo-clathrites hosted in Miocene deposits of the Apennine chain, Italy, and formed in different positions of the paleo foreland system: in wedge-top basins, along the outer slope of the accretionary prism, and at the leading edge of the deformational front. The accurate nannofossil biostratigraphy of sediment hosting paleo-clathrites in the northern Apennines allowed us to ascribe them to different Miocene nannofossil zones, concentrated in three main intervals: in the Langhian (MNN5a), in the upper Serravallian-lower Tortonian (MNN6b-MNN7) and the upper Tortonian-lowermost Messinian (MNN10-MNN11). By comparing paleo-clathrite distributions with 3rd order eustatic curves, they seem to match phases of sea-level lowering associated with cold periods. Therefore, we suggest that the drop in the hydraulic pressure on the plumbing system during sea-level lowering shifted the bottom of the gas hydrate stability zone to shallower depths, inducing paleo gas-hydrate destabilization. The uplift of the different sectors of the wedge-top foredeep system during tectonic migration might have amplified the effect of the concomitant eustatic sea-level drop, reducing the hydrostatic load on the seafloor and triggering gas-hydrate decomposition. We suggest that Miocene climate-induced sea-level changes played a role in controlling gas hydrate stability and methane emissions along the northern Apennine paleo-wedge, with hydrate destabilization roughly matching with sea-level drops and cooling events.

 

How to cite: Fontana, D., Conti, S., Fioroni, C., and Argentino, C.: Gas hydrate destabilization and sea-level changes: insights from Miocene seep carbonate deposits of the northern Apennines (Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8529, https://doi.org/10.5194/egusphere-egu21-8529, 2021.

EGU21-9321 | vPICO presentations | BG10

Using video images to study Haima cold seep bubble plumes

Kun Zhang, Haibin Song, Hongbin Wang, Yi Gong, Wenhao Fan, Yongxian Guan, Jun Tao, and Minghui Geng

Cold seep is a widespread geological process mainly caused by hydrocarbon fluid migration. Methane bubble plumes released from cold seeps are often observed at the seafloor. These methane bubbles might be released into the atmosphere and have a huge effect on climate changes. It is of great significance for understanding the fate of these methane bubble plumes.

Many kinds of methods have been used to observe the methane bubble plumes, e.g., acoustical, geochemical, and optical methods. Video imaging is a kind of optical methods widely used in methane bubble plume studies. Compared to other methods, video imaging is a non-intrusive, high-resolution, and quick-collected method. Many studies have estimated bubbles' size, rise velocities, behavior, and the fate of bubbles by analyzing video images manually. However, manual analysis is time-consuming, one dimension, and has not been able to determine temporospatial changes in a two-dimension profile perspective.

In this study, we applied the manual analysis method and the particle image velocimetry (PIV) method to analyze in-situ video image sequences of Haima cold seep bubble plumes, a newly discovered, active cold seep in the Qiongdongnan Basin of the northern South China Sea during 2019. Quantitative and temporospatial change information about the plume flow filed is obtained. The results show that the sizes of bubbles in the plume range from 2.556 ~ 4.624 mm, with a rising velocity of ~ 0.26 m/s. The flux for an individual bubble stream is ~ 94.8 ml/min. The flow velocity field of the bubble plume is consistent with the manual analysis, and it reveals that the bubble plume's flow field is a multiscale turbulent flow field. The bubble plumes are usually V-shaped. Through carrying the adjacent water column, the bubble plumes swell and change rapidly. The direction and velocity of the bubble plume flow change with time, and its streamlines are sinuous. The max velocity of the bubble plume flow field changes at a 6.6 s period cycle.

Although there is some indetermination, our results show that the PIV method is feasible for calculating the bubble plume flow field and that it has some unique advantages, e.g., it is fast, non-invasive, it provides two-dimension temporospatial change images, and it has a high resolution. The images of the bubble plume flow field provide a new perspective to observe the cold seep systems. We hope that this method can be improved and widely applied in cold seep plume studies in the future.

How to cite: Zhang, K., Song, H., Wang, H., Gong, Y., Fan, W., Guan, Y., Tao, J., and Geng, M.: Using video images to study Haima cold seep bubble plumes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9321, https://doi.org/10.5194/egusphere-egu21-9321, 2021.

EGU21-10216 | vPICO presentations | BG10

On the lack of widespread bottom simulating reflectors in the Mediterranean Basin

Cristina Corradin, Angelo Camerlenghi, Michela Giustiniani, Umberta Tinivella, and Claudia Bertoni

In the Mediterranean Basin, gas hydrate bottom simulating reflectors (BSR) are absent, with very few and spatially limited exceptions occurring in Eastern Mediterranean mud volcanoes and in the Nile deep sea fan. This is in spite of widespread occurrence of hydrocarbon gases in the subsurface, mainly biogenic methane, from a wide range of stratigraphic intervals.
In this study we model the methane hydrate stability field using all available information on DSDP and ODP boreholes in the Western Mediterranean and in the Levant Basin, including the downhole changes of pore water salinity. The models take into account the consequent pore water density changes and use known estimates of geothermal gradient. None of the drilled sites were located on seismic profiles in which a BSR is present.
The modelled base of the stability field of methane hydrates is located variably within, below, or even above the drilled sedimentary section (the latter case implies that it is located in the water column). We discuss the results in terms of geodynamic environments, areal distribution of Messinian evaporites, upward ion diffusion from Messinian evaporites, organic carbon content, and the peculiar thermal structure of the Mediterranean water column.
We conclude that the cumulative effects of geological and geochemical environments make the Mediterranean Basin a region that is unfavorable to the existence of BSRs in the seismic record, and most likely to the existence of natural gas hydrates below the seabed.

How to cite: Corradin, C., Camerlenghi, A., Giustiniani, M., Tinivella, U., and Bertoni, C.: On the lack of widespread bottom simulating reflectors in the Mediterranean Basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10216, https://doi.org/10.5194/egusphere-egu21-10216, 2021.