In this session we focus on GHG emissions and an understanding of how management activities and different land use combinations modify the GHG exchanges of different landscape mosaics. A particular emphasis will be placed on how to parcel different management practices and land uses together to provide an optimum configuration that minimizes GHG emissions. We also welcome contributions that report on the GHG mitigation potential of different management practices or land uses. Given the potential role of forests in GHG offsetting this session also seeks to bring together scientists working on the exchange of CO2, CH4 and N2O in forest ecosystems. We also welcome contributions from conventional flux measurements on cropland, grazing systems, and forests, as well as innovative approaches for gas sampling and small scale/on-farm micrometeorological measurements, together with satellite and modelling studies that seek to integrate our understanding of landscape GHG exchanges. We further invite contributions that aim at combining measurements with modelling approaches, and/or those that are trying to disentangle how management practices modify the processes responsible for GHG production and consumption at the farm or ecosystem level. This session also will benefit from contributions from FACCE ERA-GAS programme.

Public information:
This session is focused on land use mosaics and greenhouse gas emissions.

We have a varied programme, including methane uptake by forest soils, re-wetting effects on nitrous oxide emissions, solar panel forests and hedgerow carbon sequestration, so there is something for everyone!

I would encourage you to look at the abstracts and presentations for this session so that we can have an informed and lively discussion.

Please join us on Thursday 7 May, from 1400-15.45

Bruce Osborne

Convener: Bruce Osborne | Co-conveners: Syed Faiz-ul IslamECSECS, Mohammad I. Khalil, Katja Klumpp, Anna WalkiewiczECSECS
| Attendance Thu, 07 May, 14:00–15:45 (CEST)

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Chat time: Thursday, 7 May 2020, 14:00–15:45

Chairperson: Professor Bruce Osborne
D490 |
Dan Kou, Tarmo Virtanen, Aleksi Räsänen, Sari Juutinen, Mika Aurela, Lauri Heiskanen, Mingyang Guo, Qianlai Zhuang, Claire Treat, Atte Korhola, and Narasinha Shurpali

The large amounts of carbon (C) stored in the Arctic region can strongly interact with the climate system through the exchange of carbon dioxide (CO2) and methane (CH4) under the unmitigated environmental changes. Currently, there are still large uncertainties in the C exchange and the subsequent C-climate feedbacks between the land and atmosphere across the Arctic region, to which the highly heterogeneous landscapes make a key contribution. However, our knowledge on the present and future ecosystem C balance jointly considering the exchange of CO2 and CH4 in the Arctic region with heterogeneous landscapes is still limited. In this study, a process-based biogeochemistry model was calibrated and validated using the empirical data on concurrently measured CO2 and CH4 exchange observed using eddy covariance, automatic and manual chamber methods and associated climate, soil and plant data derived from several heterogeneous landscapes in the Kaamanen region. With the validated model, decadal C balance during 2005-2018 and its response to 2 oC warming were evaluated for the constituent land cover types (LCTs). Our results showed that most LCTs were a sink for atmospheric CO2 and a source of CH4 during 2005-2018. Under the 2 oC warming scenario, most ecosystems continued to be CO2 sinks and CH4 sources. Moreover, the CO2 budget in most LCTs did not change significantly as the two major fluxes of gross primary productivity (GPP) and total ecosystem respiration (TER) increased simultaneously thus maintaining similar rates of net ecosystem exchange (NEE) in response to warming, while a significant increase in CH4 emission from most LCTs was evident. Our results presented here provide us a better understanding and prediction of C dynamics and the inherent C-climate feedbacks in the Arctic region.

How to cite: Kou, D., Virtanen, T., Räsänen, A., Juutinen, S., Aurela, M., Heiskanen, L., Guo, M., Zhuang, Q., Treat, C., Korhola, A., and Shurpali, N.: Decadal carbon balance and its response to 2 degree warming among heterogenous Arctic landscapes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3087, https://doi.org/10.5194/egusphere-egu2020-3087, 2020.

D491 |
Anna Walkiewicz, Piotr Bulak, Bruce Osborne, Mohammad Ibrahim Khalil, Syed Faiz-ul Islam, Bart Kruijt, Ronald Hutjes, Daniel Spengler, Pia Gottschalk, Torsten Sachs, Katja Klumpp, Aurore Vigan, Mélynda Hassouna, Donagh Henessy, and Laurence Shalloo

Forest soils are often a sink for atmospheric methane (CH4) and are thus worth special attention in the context of mitigation of greenhouse gases (GHGs) and offset of agricultural GHG emissions at farm to national levels. The litter layer influences the exchange of GHGs between soil and atmosphere; however, most studies focus on the contribution of only soil to the CH4 cycle. In order to improve the inventory of this gas, it is worth investigating how litter influences the exchange of GHGs. Its effect on CH4 uptake may vary in deciduous and coniferous sites due to the different properties of litter. Field experiments were carried out to assess the CH4 uptake capability in 5 different soil types (with and without litter) under different forest types (deciduous, coniferous, and mixed) in Poland. During summer 2019, the highest CH4 uptake (about 2 mg C m-2 day-1) in a variant without litter on the ground was detected in Dystric Cambisol (with the highest C/N ratio) under a 100-year-old coniferous forest and in Albic Luvisol under a 58-year-old mixed forest. The presence of the litter level reduced the CH4 flux in the range of 6-27% in these locations. Methane consumption was the lowest in silty soils (~ 0.4 – 1 mg C m-2 day-1) in the mixed forest and decreased by 13-29% when covered with the litter layer. The negative effect of the litter layer on CH4 absorption was the lowest (~ 3-4%) in sandy Eutric Gleysol under a 75-year-old deciduous forest with 90% of oak and 10% of European hornbeam. The dry conditions in the summer 2019 (with total rainfall 163 mm during the tested months in the studied region) resulted in low moisture in both the litter and soil. However, even low-humidity litter (below 10%) reduced CH4 consumption rates in the measured sites.

Research was partially conducted under the project financed by Polish National Centre for Research and Development within of ERA-NET CO-FUND ERA-GAS Programme (ERA-GAS/I/GHG-MANAGE/01/2018).

How to cite: Walkiewicz, A., Bulak, P., Osborne, B., Khalil, M. I., Islam, S. F., Kruijt, B., Hutjes, R., Spengler, D., Gottschalk, P., Sachs, T., Klumpp, K., Vigan, A., Hassouna, M., Henessy, D., and Shalloo, L.: Methane uptake by various forest soils with and without litter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4900, https://doi.org/10.5194/egusphere-egu2020-4900, 2020.

D492 |
Saoirse Cummins, John Finn, Gary Lanigan, Karl Richards, Tom Misselbrook, Laura Cardenas, Chris Reynolds, and Dominika Krol

It is predicted that climate change will result in more extreme and frequent weather events including flooding and drought. Nitrous oxide (N2O) is a potent greenhouse gas having 298 times the global warming potential of CO2. The ‘Birch effect’, the term given to high  N2O fluxes following the drying and re-wetting of soils, is an accelerator of this process. Multi species grasslands have been shown have higher nitrogen use efficiency and potential for drought resilience and recovery. This experiment analysed the nitrogen dynamics of multi-species grasslands by means of quantifying the responses of soil mineral nitrogen (NH4+ and NO3-) and N2O fluxes during an eight week simulated drought, re-wetting and fertiliser application two weeks after the re-wetting event. A simplex experimental design was used to determine species and functional group effects which could potentially influence responses. The hypothesis of this study was therefore that multi species grasslands would mitigate the ‘Birch effect’ resulting in less erratic transformations of soil mineral nitrogen and lower N2O fluxes compared to monocultures. This study also predicted a lasting legacy effect of drought on soil systems resulting in prolonged heightened N2O fluxes. Drought resulted in a depletion of soil NO3-, increased  levels of NH4+ and background level N2O emissions. Following re-wetting soil mineral N underwent transformations from NH4+ to NO3- indicating nitrification. Four times more N2O emissions were recorded during re-wetting period compared to fertilizer application. There was no lasting legacy effect of drought and re-wetting on N2O fluxes observed during fertilizer application two weeks after re-wetting bar T. repens which has implications for grassland management strategies.

How to cite: Cummins, S., Finn, J., Lanigan, G., Richards, K., Misselbrook, T., Cardenas, L., Reynolds, C., and Krol, D.: The Nitrogen Dynamics of Multi-species Grasslands when Subject to Drought and Re-wetting., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5432, https://doi.org/10.5194/egusphere-egu2020-5432, 2020.

D493 |
Bart Kruijt, Reinder Nouta, Cor Jacobs, Merit van den Berg, Christian Fritz, Katja Klumpp, Ronald Hutjes, Wietse Franssen, and Bruce Osborne

With the increasing  need to mitigate rising atmospheric greenhouse gas (GHG) concentrations more attention is being directed at the quantification  of the GHG exchange characteristics of heterogenous landscape assemblages that vary in land cover and land use.   Whilst emission-limiting or uptake-enhancing management actions are often being proposed for specific land use most remain to be experimentally tested and  validated at the landscape scale. This is a challenge because the typical size of different landscape elements  (fields, afforested areas and unmanaged land at hectare scale) or experimental fields where emission reduction measures are being tested, is at the lower limit of what micrometeorological techniques such as eddy covariance measurements can deal with. With large heterogeneity the use  of chamber measurements is also limited. The investments to be made in equipment are a challenge for operational monitoring of GHG budgets.

To address this we assess the feasibility of several options to acquire appropriate data in a way that is achievable for stakeholders, such as land managers and regional authorities. We use existing and new flux data from an agricultural landscape in the North of the Netherlands  to: 1) compare paired eddy covariance (EC) data and automatic chamber (AC) data to test the representativity of small footprints. Results from a test site on drained meadows show almost identical CO2 fluxes. Future research should compare grass length and soil moisture of EC- and AC footprints; 2) test simplified alternatives to EC, such as those relying on concentration variances. Data from the peat meadow site suggest that time-averaged fluxes can be estimated in an empirical way with reasonable accuracy from concentration variances; 3) analyze the value of information gathered with mobile, roving/temporary EC approaches interpolated with gap filling models. The indications are  that the values and variability of fluxes is largely  conserved and predictable within seasons In all these analyses, we will consider the tradeoffs between the need for accuracy and pragmatism in operational practice.

How to cite: Kruijt, B., Nouta, R., Jacobs, C., van den Berg, M., Fritz, C., Klumpp, K., Hutjes, R., Franssen, W., and Osborne, B.: Towards operational quantification of GHG exchange in heterogeneous agricultural landscapes and experimental plots, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6122, https://doi.org/10.5194/egusphere-egu2020-6122, 2020.

D494 |
| Highlight
Juan Pablo Iñamagua Uyaguari, Pamela Sangoluisa, David R Green, Nuala Fitton, and Pete Smith

Ecuador, as a signatory to the United Nations Framework Convention on Climate Change, in its Nationally Determined Contribution, has expressed its intention to reduce greenhouse gas emissions (GHG), with a focus on the energy and forest sectors. Despite the socio-economic importance and the growing pressure of agricultural and livestock activities on land use change, this sector is not explicitly considered in the national mitigation goals. Currently, grasslands occupy 57% of agricultural land in Ecuador and cattle, being the main livestock activity, is responsible for at least 46% of agricultural emissions, the third largest source of GHG emissions, after land use change and energy. The foot and mouth disease national eradication campaign carried out in 2016, shows that the cattle population is distributed over approximately 275000 farms, where 80% of these farms can be considered as subsistence systems (<20 animals/farm). Due to the heterogeneity of these systems, mitigation strategies focused on reducing methane from enteric fermentation can be difficult to apply, measure, and report. Another possibility for cattle livestock systems is to focus the mitigation opportunities on maintaining carbon stocks and enhancing carbon sequestration through the management of trees on farms. This study analyses the contribution of trees in pasture areas and forests on small livestock systems for offsetting GHG emissions from cattle activities. In 2018, a survey was performed on 101 farms distributed across the Amazon and coastal region in Ecuador, where herd characteristics and management were recorded.  Farmers were asked to draw the boundaries of the farm on a Google Earth map, identifying the extent of primary and secondary forest areas. Trees in pasture areas were measured on plots of 1000m2, with two plots per farm. A UAV survey was performed using a DJI Mavic Pro quadcopter, equipped with an RGB camera, over plots off 125m2, and at a flying altitude of 70m. For this work, 37 farms were selected (13 in the Amazon region and 24 in the Coastal region) and GHG emissions calculated from cattle livestock activities using IPCC Tier 1 equations. The aboveground biomass for pasture areas was estimated using the Jucker et al., 2017 equation, with tree characteristics derived from the UAV survey. Average results were extrapolated to the total pasture area reported by farmers in the survey. Primary and secondary forest areas were identified from satellite images. Forest state (degradation level) was estimated using NIR data from SENTINEL-2/LANDSAT 8/PlanetScope. Aboveground biomass estimates for forests were obtained from published data using similar site conditions. Emissions from cattle activities are expressed as carbon equivalent. Biomass carbon was estimated as 0.47 of total biomass.

How to cite: Iñamagua Uyaguari, J. P., Sangoluisa, P., Green, D. R., Fitton, N., and Smith, P.: Do we need more trees to achieve carbon neutrality on livestock farms? Accounting for the negative emissions on small tropical livestock farms in Ecuador , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8017, https://doi.org/10.5194/egusphere-egu2020-8017, 2020.

D495 |
Mohammad I. Khalil and Bruce A. Osborne

Quantification and reporting of soil organic carbon density (SOCρ) changes and greenhouse gases (GHGs), particularly nitrous oxide (N2O), emissions from agricultural soils using higher tiers remain a key challenge. Modelling approaches can provide largescale land use and management coverage whilst minimizing spatial and temporal variability. Identification of an advanced tool to simulate the net balance of SOC and GHG for mitigation, offsetting and policy formulation is a global concern. We tested the widely used latest version of Denitrification-Decomposition (DNDC95) model, a process-based one, to simulate both SOCρ and N2O emissions and their annual changes over 45 years. The moist temperate grass silage was managed with inorganic fertilizer as urea and organic ones as cattle and pig slurry applied at low, medium and high rates. The model performed well for urea, cattle slurry and pig slurry to predict both SOCρ and N2O emissions. The measured data for SOCρ at a 0-15 cm depth for unfertilized and urea-fertilized fields (73-77 t C ha-1) were significantly higher than the simulated ones (54-55). However, the model-estimates showed good agreement with the measured values (R2 = 0.66) and revealed increased C sequestration with increasing added-C (0.46±0.06 vs. 0.37±0.01 t C ha-1 yr-1). The model simulated N2O emissions well and the resulted emission factors (EFs) estimated on average to be 0.35 ± 0.02, 1.80 ± 0.28 and 1.53 ± 0.41%, respectively, which are close to national and IPCC estimates. Variations in the simulated-SOCρ and derived-EFs could be explained mainly by differences in nitrogen inputs (49%) and added-C (62%), respectively, where the impact of rainfall (15-16%) and temperature (10-11%) was identical. Generally, SOCρ and N2O EFs were sensitive to soil texture, pH, bulk density and organic carbon (R2 = 0.77-0.99) but annual changes in SOCρ decreased with the latter two (R2 = -0.99). Application of animal slurry during autumn demonstrated more C being sequestered in the clay loam soil (Dystric Gleysol) and strategic replacement of slurry either after the second or third silage cuts by urea decreased N2O EFs significantly. Results  imply that the updated DNDC95 could provide an accurate representation of the key drivers influencing both SOCρ and N2O fluxes in temperate grass silage.

How to cite: Khalil, M. I. and Osborne, B. A.: Simulation of long-term changes in soil organic carbon and nitrous oxide emissions from permanent grass silage using the DNDC model, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10279, https://doi.org/10.5194/egusphere-egu2020-10279, 2020.

D496 |
Sophie Drexler and Axel Don

The establishment of hedgerows as traditional form of agroforestry in Europe is a promising strategy to promote carbon sinks in the context of climate change mitigation. However, only few studies quantified the potential of hedgerows to sequester and store carbon. We therefore conducted a meta-analysis to gain a quantitative overview about the carbon storage in the above- and below-ground biomass and soils of hedgerows.

Soil organic carbon (SOC) data of hedgerows and adjacent agricultural fields of nine studies with 83 hedgerow sites was compiled. On average, the establishment of hedgerows on cropland increased SOC by 32%. No significant differences were found between the SOC storage of hedgerows and that of grassland. The literature survey on the biomass carbon stocks of hedgerows resulted in 23 sampled hedgerows, which were supplemented by own biomass data of 49 hedgerows from northern Germany. Biomass stocks increased with time since last coppicing and hedgerow height. The mean (± SD) above-ground biomass carbon stock of the analysed hedgerows was 48 ± 29 Mg C ha-1. Below-ground biomass values seemed mostly underestimated, as they were calculated from above-ground biomass via fixed assumed root:shoot ratios not specific for hedgerows. Only one study reported measured root biomass under hedgerows with a root:shoot ratio of 0.94:1 ± 0.084. With this shoot:root ratio an average below-ground biomass carbon stock of 45 ± 28 Mg C ha-1 was estimated, but with high uncertainty.

Thus, the establishment of hedgerows on cropland could lead to a SOC sequestration of 1.0 Mg C ha-1 year-1 over a 20-year period. Additionally, up to 9.4 Mg C ha-1 year-1 could be sequestered in the hedgerow biomass over a 10 year period. In total, hedgerows store 106 ± 41 Mg C ha-1 more C than croplands. Our results indicate that organic carbon stored in hedgerows is similar high as in forests. We discuss how the establishment of hedgerows, especially on cropland, can thus be an effective option for C sequestration in agricultural landscapes, meanwhile enhance biodiversity, and soil protection.

How to cite: Drexler, S. and Don, A.: Organic carbon storage in the biomass and soils of hedgerows, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13323, https://doi.org/10.5194/egusphere-egu2020-13323, 2020.

D497 |
Adam Kubaczyński, Anna Walkiewicz, Małgorzata Brzezińska, and Bogusław Usowicz

Agricultural soils are an important landscape element in terms of climate change and this ecosystem is considered as a one of the major source of greenhouse gases (GHGs). Soil may be also a sink for GHGs, from this reason so many research projects are focused on determination of factors and conditions affecting gas exchange. Biochar is produced from biomass that has been pyrolysed in a zero or low oxygen availability. It is currently widely considered as a stable addition to the soil, which not only improve its fertility, but also can mitigate climate change. Considering landscape elements, the char also prevents carbon loss from forest soils. Higher microbial activity is usually associated with higher carbon dioxide (CO2) production (soil respiration). One of the most important questions is how does biochar influence production of GHGs such as CO2? Which doses have a critical meaning for CO2 emission? The aim of our study was to determine the effect of wide range doses of biochar (produced from sunflower husks) (from 1 to 100 Mg ha-1) to Haplic Luvisol soil from fallow fields. We investigated the changes of CO2 emission during laboratory incubation using gas chromatography method. In short-term incubations soil respiration was positively correlated with increasing biochar dose, while during long-term (several years) observation, the impact of biochar dose on the amount of emitted CO2 was not so significant. It is worthwhile to conduct short- term and long-term field studies in this area.

Research was partially conducted under the project “Water in soil - satellite monitoring and improving the retention using biochar” no. BIOSTRATEG3/345940/7/NCBR/2017 which was financed by Polish National Centre for Research and Development in the framework of “Environment, agriculture and forestry” - BIOSTRATEG strategic R&D programme.

How to cite: Kubaczyński, A., Walkiewicz, A., Brzezińska, M., and Usowicz, B.: How does biochar affect soil respiration?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13343, https://doi.org/10.5194/egusphere-egu2020-13343, 2020.

D498 |
Andrzej Bieganowski, Małgorzata Brzezińska, Cezary Polakowski, Sylwia Duda, Anna Walkiewicz, Karolina Tkaczyk, Katarzyna Jaromin-Gleń, and Magdalena Frąc

The use of biofertilizers is a promising method of improving the quality of degraded and cultivated soils. High soil quality ensures high crop yields as well as is prerequisite to the proper soil functioning in the ecosystem. We tested methanotrophic activity of sandy and clayey soil (located in Poland - in Biszcza and Basznia, respectively) as affected by the use fertilizers with microorganisms and humic acids. Nine soil treatments were included (B: without microbial enrichments: (C) - Control zero without fertilization; (CF) - Control zero + fungal strains; (CB) - Control zero + bacterial strains; (UC) - Urea without microbiological amendment; (UA100) - Urea (100% + bacterial strains; (UA60) - Urea (60%) + bacterial strains; (NPK) - Control + NPK; (NPKF) - Control + NPK + fungal strains; and (NPKB) – Control + NPK + bacterial strains. Soil samples were collected two months after fertilization, and incubated in laboratory with methane (1% vol.) for 21 days. Soils differed in CH4 uptake rate and showed various response to the treatments. Generally, sandy soil showed higher methanotrophic activity than clayey soil. Fungal and bacterial strains (CF and CB) delayed CH4 oxidation in sandy soil, while not affected the process in the clay soil. Urea apparently inhibited CH4 oxidation in sandy soil without as well as with microbial enrichment (UC, UA100, UA60). In clayey soil urea had no effect. The use of NPK fertilizer without microbes inhibited CH4 consumption compared to Control (C) in sandy soil but not in clayey soil. Fungal (NPKF) and bacterial (NPKB) enrichments resulted in acceleration of the CH4 oxidation in sandy soil. In clayey soil fungal enrichments (NPKF) accelerated CH4 oxidation while bacterial amendments (NPKB) gave the opposite effect.


The presentation is financed by the National Centre for Research and Development under the program BIOSTRATEG3, contract number BIOSTRATEG3/347464/5/NCBR/2017 "BIO FERTIL"

How to cite: Bieganowski, A., Brzezińska, M., Polakowski, C., Duda, S., Walkiewicz, A., Tkaczyk, K., Jaromin-Gleń, K., and Frąc, M.: Short-term response of methane oxidation to biofertilizer treatments in sandy and clay soil., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13514, https://doi.org/10.5194/egusphere-egu2020-13514, 2020.

D499 |
Jing Zhao, Guoqing Li, and Jason Blake Cohen

Estimates of fossil-fuel carbon dioxide (FFCO2) emissions in China are contingent on large uncertainty, and currently have enormous discrepancies among different inventories/datasets. The uncertainty is most attributed to underlying causes: only a few actual measurements and consumption data, and the statistical methods to confine the spatial resolution of FFCO2. In this study, an attempt is made to assess the heterogeneities and uncertainty associated with spatial distributions of emissions in six gridded FFCO2 inventories/datasets, which are compared at a 0.25 × 0.25 degree resolution.

We extract signals of urban CO2 emissions with a Deep Learning (DL) & Deep Reinforcement Learning (DRL) modeling framework from the existing new generation of satellite (OCO-2/GOSAT-2/TROPOMI) observations of atmospheric column CO2 (XCO2). We then use the results as a proxy to further estimate of the FFCO2 uncertainty. Subsequently, the estimated FFCO2 uncertainty is included in an up-to-date multivariate spatial statistic to analyze China’s spatiotemporal FFCO2 emissions balance, with a specific consideration made for the mitigation potential of different land-use types.

We find an interconnected system between the spatial FFCO2 emissions distribution and two diverse factors being the most important: urbanization and either croplands (rainfed, irrigated, and post-flooding) or native vegetation. We have determined that wettability in croplands or the increase in native vegetation have an association with the decrease of FFCO2 emissions. Ongoing work addresses the potential impacts of this FFCO2 uncertainty on flux inversions.

How to cite: Zhao, J., Li, G., and Cohen, J. B.: Multi-source data driven spatial changes of FFCO2 emissions balance and mitigation potential of different land use in China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15311, https://doi.org/10.5194/egusphere-egu2020-15311, 2020.

D500 |
Syed Faiz-ul Islam, Mohammad Ibrahim Khalil, Katja Klumpp, and Bruce A. Osborne

 It has been widely reported that although IPCC methodologies appropriate for national-level accounting purposes, they lack the farm level resolution and holistic approach required for whole-farm systems analysis. The importance of evaluating greenhouse gas (GHG) emissions from crop production, animal farming and agroforestry within the whole farm setting is being realized as more important than evaluating these emissions in isolation. Thus, whole-farm systems modelling is widely used for farm-level analysis. Here we compare three whole-farm models e.g. FarmSim, Holos and IFSM to simulate the effect of management practices on GHG emissions at the whole farm level and evaluate the carbon sequestration and methane oxidation potential of afforestation as a compensation mechanism for the mitigation of farm-level GHG emissions. Ideally, we would also want information on model performance in predicting GHG emissions in future climatic scenarios. Initial results indicate that these models can accurately predict CO2 emissions but the accuracy of these models for predicting methane (CH4) and nitrous oxide (N2O) emissions is quite low. We found that the most prominent drivers for GHG emissions in a whole farm setting were the enteric CH4 from animal farming and N2O emissions from soil management in cropland.  Thus, the low prediction accuracy for CH4 and N2O emissions in whole-farm models may introduce substantial errors into GHG inventories and lead to incorrect mitigation recommendations, which necessitates further fine-tuning of these models. Efforts are ongoing to integrate carbon sequestration and soil methane oxidation potential of farm-level afforestation in the whole farm models. There are indications that afforestation can be an effective mitigation strategy. The variation we found in farm system parameters, and the inherent uncertainties associated with emissions of CH4 and N2O can have substantial implications for reported agricultural emissions requiring uncertainty or sensitivity analysis in any modelling approach. Although there is considerable variation among the quality of farm data, boundary assumptions, the emission factors used we suggest that whole-farm systems models are an appropriate tool to develop and measure GHG mitigation strategies for the European farmed landscape.

How to cite: Islam, S. F., Khalil, M. I., Klumpp, K., and Osborne, B. A.: Reducing uncertainty in quantifying and reporting GHG emissions and carbon sequestration from European farming landscapes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18708, https://doi.org/10.5194/egusphere-egu2020-18708, 2020.

D501 |
| solicited
Rafael Stern, Madi Amer, Jonathan Müller, Fyodor Tatarinov, Lior Segev, Eyal Rotenberg, and Dan Yakir

       The production of electricity from solar radiation should replace power production by burning fossil fuel and help reduce atmospheric concentrations of CO2. However, large photovoltaic (PV) fields can also influence the climate in more direct ways. The albedo of solar panels is low to allow efficient light absorption, but actual conversion efficiency is below  20%. The remaining 80% of the energy is reflected, re-emitted as thermal radiation or dissipated as sensible heat (H). These effects can heat the surface, influence local air circulations, and lead to the formation of “heat-islands”. Such effects are particularly significant in desert areas with high radiation load and high background albedo. The ultimate objective of this study will be to estimate the cost (in number of years) of CO2 emission suppression of a PV power generation (a “cooling effect”) associated with the albedo radiative forcing and the surface "warming effects" and the partitioning to its components.

       We used a state-of-the-art field laboratory to carry out eddy covariance flux measurements of sensible and latent heat, and the radiative balance of incoming and outgoing short- and long-wave radiations. A research drone equipped with a thermal and a multi-spectral camera was used to estimate the spatial average reflected and emitted radiation from the solar panels field. Measurements were carried out on campaign basis during 2018-2019, both inside and outside a PV field in the Arava desert in southern Israel.

       The preliminary results indicated that summer noon incoming solar radiation (S) is ~1000 Wm-2 and the desert surface albedo is on average 0.40. The mean solar panel field albedo is 0.23 (with panels projected area about 1/3rd of the PV field area), which is translated to ~170 Wm-2 higher S absorption by the PV field. A large fraction of the energy is converted to sensible heat flux with mid-day H values of 450 Wm-2, compared with 250 Wm-2 in the desert, or about 200 Wm-2 of extra heating above the PV field. A first approximation of the summer daily carbon suppression (assuming 12h daily average sunlight of ~500 Wm-2, PV efficiency of 0.2, and conventional power efficiency of ~200 gC/KWh) indicated ~0.08 Kg C per day per m-2 PV area. These preliminary results are being extended to include thermal emission effects and the annual scale perspective to assess the “PV forest” radiative forcing effect. But it is evident that the land use change examined here has a large impact on the surface energy budget and its surrounding environments.

How to cite: Stern, R., Amer, M., Müller, J., Tatarinov, F., Segev, L., Rotenberg, E., and Yakir, D.: “Solar panels forest” and its radiative forcing effect: preliminary results from the Arava Desert, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18924, https://doi.org/10.5194/egusphere-egu2020-18924, 2020.

D502 |
Mona Reiss, Andy Krause, and Anja Rammig

Current scenarios assume that in addition to a rapid reduction in greenhouse gas emissions, land-based carbon mitigation will also be necessary to achieve the targets of the Paris Climate Agreement. Possible measures are increased carbon sequestration via planting new forests, the cultivation of bioenergy crops, possibly in combination with carbon capture and storage (BECCS), or increasing the carbon storage of existing forests. However, currently available scenarios that are in line with IPCC storylines (SSPs, Shared Socioeconomic Pathways and RCPs, Representative Concentration Pathways) usually have  a global  perspective, while in practice mitigation projects have to be realized regionally or locally. Here, we investigate the carbon mitigation potential via alternative management of Bavarian ecosystems using an ecosystem model with an explicit representation of climate impacts and land management. Bioenergy cultivation on existing agricultural land has a larger mitigation potential than reforestation only if combined with carbon capture and storage (BECCS).  The mitigation potential in the forestry sector via alternative management is limited (converting coniferous into mixed forests, nitrogen fertilization) or even negative (suspending wood harvest) due to decreased carbon storage in product pools and associated substitution effects. Overall, the potential for land-based mitigation in Bavaria is limited because the majority of current agricultural lands will still be needed for food production and the forestry sector offers only small per-area carbon mitigation potentials.

How to cite: Reiss, M., Krause, A., and Rammig, A.: A regional assessment of land-based carbon mitigation options: Bioenergy, reforestation, forest management, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21473, https://doi.org/10.5194/egusphere-egu2020-21473, 2020.