BG3.15 | Linkages between soil fauna and biogeochemical cycles
EDI
Linkages between soil fauna and biogeochemical cycles
Co-organized by SSS8
Convener: Robert Bradley | Co-conveners: Ingrid Lubbers, Jan Willem Van Groenigen, Gerrit Angst
Orals
| Tue, 16 Apr, 08:30–10:15 (CEST)
 
Room 2.17
Posters on site
| Attendance Tue, 16 Apr, 16:15–18:00 (CEST) | Display Tue, 16 Apr, 14:00–18:00
 
Hall X1
Orals |
Tue, 08:30
Tue, 16:15
Soil fauna perform many ecological functions that control ecosystem nutrient dynamics, regulate primary productivity, develop and maintain soil structure, and contribute to the quality of the atmosphere and water supply. Over recent decades, research has revealed interesting facts about soil fauna such as their contribution to ecosystem stability, pesticide remediation, multitrophic interactions that link above and belowground energy fluxes, etc. The proposed session encourages submissions from all aspects of research dealing with the effects of soil fauna on biogeochemical cycles, such as (1) the regulation of soil organic matter decomposition, (2) nutrient cycling and soil fertility, (3) soil carbon storage, (4) greenhouse gas emissions, (5) soil hydrology and nutrient leaching, (6) ecosystem energy fluxes, (etc.). The organizers are hoping to attract participants with diverse backgrounds, with the intended purpose of fostering scientific interactions and collaborations among individuals and established research networks. We welcome submissions from students, early-career and well-established researchers.

Orals: Tue, 16 Apr | Room 2.17

08:30–08:35
08:35–08:45
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EGU24-1454
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ECS
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On-site presentation
Raquel Juan-Ovejero, Marie L.C. Bartz, Dilmar Baretta, José Paulo Sousa, and Verónica Ferreira

Eucalypt plantations may have negative consequences on soil properties, yet a comprehensive understanding of their impact on soil invertebrate communities is lacking. This knowledge gap constrains our ability to unravel the potential effects of these fast-growing plantations on soil functioning. Hence, to analyze the overall impact of eucalypt plantations on soil invertebrates and to determine the main factors influencing these effects, we conducted a meta-analysis of studies comparing eucalypt plantations with different land use types (i.e. native forests, other forestry plantations, croplands, grasslands, integrated production systems, and invasive copses). We assessed their effects on both the density (analyzing 26 studies with 143 comparisons) and diversity (examining 14 studies with 168 comparisons) of soil invertebrate communities. The impact of eucalypt plantations on the density and diversity of soil invertebrate communities did not show statistically significant differences when considering all land use types together. However, the effects of eucalypt plantations on soil invertebrate density and diversity varied based on the specific land use types considered for comparison. The density was lower in eucalypt plantations relative to other forestry plantations but higher than in grasslands and integrated production systems. Contrarily, diversity was lower in eucalypt plantations compared to native forests but higher compared to other forestry plantations. Furthermore, the impacts of eucalypt plantations on soil invertebrates relative to other forestry plantations were influenced by factors such as the type of other forestry plantation (angiosperms versus gymnosperms), mean annual temperature, and annual precipitation of the study sites. These findings suggest that the effects of eucalypt plantations on soil invertebrate communities are context-specific and heavily influenced by the diverse characteristics of the different land use types considered for comparison. Taking into account the specific management practices and environmental conditions within eucalypt plantations and other land use types can provide insight into how alterations in land cover affect soil invertebrate communities.

How to cite: Juan-Ovejero, R., Bartz, M. L. C., Baretta, D., Sousa, J. P., and Ferreira, V.: A meta-analysis addressing the effects of eucalypt plantations on soil invertebrate density and diversity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1454, https://doi.org/10.5194/egusphere-egu24-1454, 2024.

08:45–08:55
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EGU24-9456
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On-site presentation
Andrea Watzinger, Noller Christoph, Janet Wissuwa, and Wolfgang Friesl-Hanl

The most powerful tool to explore nutrient turnover in complex systems such as soils are stable isotope fractionation and labelling studies. This has been extensively used when investigating microbial carbon cycles by targeting the carbon stable isotopes in microbial phospholipid fatty acids (PLFA). However, exploring the role of mesofauna during carbon turnover in soil ecosystems has long been limited due to the small size and weight of those organisms and therefore issues in the detection and quantification of carbon stable isotope ratios. Only recently, carbon stable isotope analysis of fatty acids (FA) have been established and opened the window to include mesofauna into carbon turnover studies. We have used this new possibility after refining the available FA method to discover the role of microarthropods together with the microbial PLFA analysis. This study is to our knowledge the first, which has used 13C labelled plant material and has followed its incorporation into microbial PLFAs and microarthropodal FAs in a greenhouse experiment containing heavy metal contaminated and remediated soils.

Total microbial biomass and 13C incorporation into microorganisms was significantly increased and the PLFA pattern shifted after remediation of heavy metal contaminated soil. In accordance, the abundance of the microarthropodal groups Gamasina, Oribatida and Collembola were also increased, while Astigmata were not affected. The relative FA patterns of those groups differentiated significantly among each other, but were not influenced by soil treatment, meaning that the altered microbial PLFA pattern was not transferred into microarthropodal FA. However, the amount (nmol FA) per individuum was elevated in the heavy metal contaminated soil. In contrast, incorporation of 13C into FA was lower in contaminated soil in Gamasina, Astigmata and Collembola. 13C incorporation of Oribatida was at a constantly high level over the different soil treatments.

These first results revealed, that the relative FA pattern of the microarthropodal groups was not affected by changes in the microbial PLFA pattern due to soil treatments. Differences in the absolute FA amount per individuum and the 13C uptake were rather governed by the life and reproduction strategies, with higher fattiness and low abundance under adverse environmental conditions (contaminated soil), constant 13C incorporation in K-strategist (Oribatida) and higher 13C incorporation of mainly r-strategist (Gamasina, Astigmata and Collembola) under improved conditions.

How to cite: Watzinger, A., Christoph, N., Wissuwa, J., and Friesl-Hanl, W.: The role of microarthropodal groups in carbon turnover as revealed by 13C fatty acids analysis – method development and impact of heavy metal remediation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9456, https://doi.org/10.5194/egusphere-egu24-9456, 2024.

08:55–09:05
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EGU24-6967
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ECS
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On-site presentation
Florian Jordan and Rock Ouimet

Sugar maple (Acer saccharum Marsh.) forests are the dominant ecosystems in southern Quebec (Canada) and are widely used for maple syrup production, wood products manufacturing, recreation, and sometimes converted to hybrid poplar plantations. Consequently, human footprints on these ecosystems are multifarious, with potential impacts on soil greenhouse gas (GHG) emissions. We studied the principal and interactive effects of three anthropogenic factors (liming, introduction of non-native earthworms, and tree litter quality) on soil CO2 and N2O emissions, and on related soil properties. Thirty-two PVC pipes (1.0 m x 30 cm dia.) were set upright and filled with homogenized soil collected from a sugar maple stand. Each of these mesocosms was assigned one of eight treatments from a 2×2×2 factorial array of three experimental factors (± liming, ± earthworms, maple vs. poplar litter), replicated in four complete blocks. Over the course of a 15-month trial, we measured soil CO2 and N2O emissions from each mesocosm. At the conclusion of the trial, we measured soil pH, % organic matter (SOM), mineralizable nitrogen (Nmin), water-stable aggregate index (WSAI), δ13C, and mineral-associated organic matter (C-MAOM) at each of four soil depths (0, 20, 40 and 60 cm). The effects of earthworms (+EW) and liming on the response variables were generally greater than the effects of litter types. Liming increased pH by 0.6 units in the soil surface layer. Treatments had negligible effects on SOM throughout the soil profile. Nmin increased by factors of ×15 and ×7 in the surface layer of the Liming and EW treatments respectively. In contrast, mineralizable NO3-/NH4+ ratios were 125 and 80 in the EW and EW+Liming treatments respectively, and only 30 in the Liming and Control treatments, suggesting that nitrification was stimulated by soil mixing/aeration rather than by pH. Accordingly, cumulative N2O emissions were higher in the EW and Ew+Liming treatments (500 and 250 mg N2O-N m-2, respectively) compared to the Control and Liming treatments (< 50 mg N2O-N m-2). Likewise, cumulative CO2 emissions increased in the EW treatment and decreased in the Liming treatment relative to the Control; liming offset the positive effect of earthworms when both factors were combined.  Liming increased δ13C by 3‰ in the soil surface layer, hinting that lower CO2 emissions in this treatment could have resulted from higher microbial processing of litter leading to more stable SOM. However, all treatments had no effect on C-MAOM, suggesting instead that higher δ13C in the Liming treatment resulted from higher 13C in the liming material compared to native soil C. Moreover, both Liming and EW treatments increased WSAI, thus refuting the premise that CO2 and aggregate stability were related. We conclude that the spread of non-native earthworms in sugar maple forests of southern Quebec is potentially increasing soil N2O and CO2 emissions by up to one order of magnitude. Increased N2O emissions are likely due to increased nitrification, whereas CO2 emissions cannot be predicted by changes in C-stability. Liming could potentially be used to mitigate the positive effects of earthworms on soil GHG emissions.

How to cite: Jordan, F. and Ouimet, R.: Liming offsets the increase in soil greenhouse gas emissions due to non-native earthworms in sugar maple forests., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6967, https://doi.org/10.5194/egusphere-egu24-6967, 2024.

09:05–09:15
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EGU24-5867
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On-site presentation
Lars Vesterdal, Christina Steffens, Yan Peng, Haifeng Zheng, Huimin Yi, and Petr Hedênec

Tree species with leaf litter traits driving slow rates of leaf litter decomposition have traditionally been associated with accumulation of higher soil organic carbon (SOC) stocks than tree species with fast litter decomposition rates. This hypothesis has mainly been based on observations of thick C-rich forest floors under tree species associated with ectomycorrhizae (ECM). However, a recent hypothesis suggested that tree species with foliar litter traits conducive to fast decomposition will lead to more pronounced microbial transformation and stabilization of litter C. The latter tree species are often associated with arbuscular mycorrhizae (AM) and may enhance deeper incorporation of C by more active soil fauna communities and by higher belowground rates of litter input. The Danish multi-site common garden tree species experiment includes ECM and AM tree species that differ widely in traits such as foliar litter chemistry. The experiment has been studied over the last 15 years to document and explain soil C stocks supported by emerging studies of soil fauna and soil microbial community composition and functioning.

The six common European tree species formed distinct groups in soil carbon characteristics as well as in soil biota community composition and functioning that partly reflected their mycorrhizal association. Forest floor C stocks were consistent with the traditional perception of slowly decomposing leaf litter in ECM species being conducive to high C stocks. However, an intriguing pattern of higher C stocks in the mineral soil in AM tree species with high litter quality and characteristic soil biota functioning supported the recent microbial stabilization hypothesis and suggested deeper incorporation of C in more stable forms.

Based on new results on microbial, macro- and mesofauna communities and their functioning, and on repeated soil sampling, this talk will revisit the common garden experiments for a synthesis of processes and patterns in organic matter formation that may explain observed patterns in quantity and quality of SOC.

How to cite: Vesterdal, L., Steffens, C., Peng, Y., Zheng, H., Yi, H., and Hedênec, P.: Tree species effects on stocks and stability of soil carbon: Links to mycorrhizal association and soil biota composition and functioning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5867, https://doi.org/10.5194/egusphere-egu24-5867, 2024.

09:15–09:25
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EGU24-11070
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ECS
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On-site presentation
Junwei Hu, Meng Kong, Astrid Françoys, Farideh Yarahmadi, Orly Mendoza, Ummehani Hassi, Mesfin T. Gebremikael, Wim Wesemael, Steven Sleutel, and Stefaan De Neve

Soil nematodes, being the most abundant soil fauna, can significantly impact soil N mineralization via interaction with soil microorganisms. As a consequence, nematodes likely also influence soil N2O production and emissions but the very few studies on this matter were carried out in simplified setups with single nematode species and in (highly) disturbed soil conditions. Here we measured soil N2O emissions in a 74-day incubation experiment in the presence or absence of the entire soil nematode community with minimal disturbance of the soil microbial community and soil nutrients. This was e.g. evidenced by readily recovery of nitrifiers after the mild and selective sterilization and soil powder inoculation. N2O emissions increased in the presence of nematodes, varying between soils +747.7 % in a loamy sand, +55.8 % in a loam, and +51.9 % in a silt loam cropland topsoil, in line with nematode abundance in these soils. In particular, the loamy sand soil showed an atypical N2O emission peak at the time of high nematode abundance. Soil nematodes also increased net N mineralization by +8.4, +6.8 and +4.75 %, in these respective soils and to a smaller extent C mineralization as well. The extra soil nitrate buildup and the overall net stimulation of N mineralization by nematodes could not or just slightly explain the observed increased N2O emissions. This research revealed the important role of soil nematodes in regulating N2O emissions, and further stresses the need to consider the change in community composition and activity of denitrifiers, and connectivity of soil pores, rather than the stimulation of N mineralization as potential explanations for this role of nematodes.

How to cite: Hu, J., Kong, M., Françoys, A., Yarahmadi, F., Mendoza, O., Hassi, U., Gebremikael, M. T., Wesemael, W., Sleutel, S., and De Neve, S.: Increased N2O emissions by the soil nematode community cannot be fully explained by enhanced mineral N availability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11070, https://doi.org/10.5194/egusphere-egu24-11070, 2024.

09:25–09:35
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EGU24-3873
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On-site presentation
Eveline J. Krab, Gesche Blume-Werry, Jonatan Klaminder, and Sylvain Monteux

Alleviation of functional limitations by soil fauna is key to climate feedbacks from arctic soils

Arctic soils play an important role in Earth’s climate system, as they store large amounts of carbon that, if released, could strongly increase greenhouse gas levels in our atmosphere. Most research to date has focused on how the turnover of organic matter in these soils is regulated by abiotic factors, and few studies have considered the potential role of biotic regulation. However, arctic soils are currently missing important groups of soil organisms, and here, we highlight recent empirical evidence that soil fauna presence or absence is key to understanding and predicting future climate feedbacks from arctic soils. We propose that the arrival of certain soil fauna into arctic soils may introduce “novel functions”, resulting in increased rates of, for example, nitrogen cycling, litter fragmentation, or bioturbation, and thereby alleviate functional limitations of the current soil organism community. This alleviation can greatly enhance decomposition rates, in parity with effects predicted due to increasing temperatures. We base this argument on a series of emerging experimental evidence suggesting that the dispersal of until-then absent micro- meso-, and macroorganisms into new regions and newly thawed soil layers can drastically affect soil functioning. These new observations make us question the current view that neglects organism-driven “alleviation effects” when predicting future feedbacks between arctic ecosystems and our planet’s climate. We therefore advocate for an updated framework in which soil biota and the functions by which they influence ecosystem processes become essential when predicting the fate of soil functions in warming arctic ecosystems.

How to cite: Krab, E. J., Blume-Werry, G., Klaminder, J., and Monteux, S.: Alleviation of functional limitations by soil fauna is key to climate feedbacks from arctic soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3873, https://doi.org/10.5194/egusphere-egu24-3873, 2024.

09:35–09:45
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EGU24-7897
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ECS
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On-site presentation
Justine Lejoly, Yuxin Wang, Esther van Hoof, Valentin Favre, Casper Quist, Stefan Geisen, and Ciska Veen

The soil microbiome is widely recognized as an important driver of soil carbon (C) cycling but the role of soil fauna is largely overlooked. It is proven that microbivores, e.g., bacterivorous nematodes, can alter the microbiome composition and activity, but the microbivores themselves can be controlled by their predators. How these higher trophic interactions impact the soil microbiome, through trophic cascades, remains to be investigated, as well as the consequences for soil C cycling.

We tested the existence and direction of trophic cascades in soil food webs by manipulating the presence of bacterivorous-dominated nematode communities and their predators (nematode-feeding mite Gaeolaelaps aculeifer) in a full factorial design. After microbial re-inoculation of sterilized grassland soil and soil food web reconstruction, we monitored the decomposition of added grass litter and associated C mineralization during five weeks. We also characterized the soil microbiome composition by phospholipid fatty acid analysis and 16S sequencing.

While the presence of nematodes mostly did not affect C cycling, the addition of predators decreased C mineralization by 10 %. However, litter decomposition rates were unaffected by soil food web composition. Taken together, these results suggest that the presence of predators may result in enhanced soil C stabilization, at least in the short term. The presence of predators also resulted in a shift in microbiome composition, notably with higher Gram(+):Gram(-) ratios, but no change in microbial biomass, suggesting that nematodes may shift their diet because of predation. Our results confirm that the effects of nematodes and their predators on the soil microbiome are not additive and that predators can alter soil C cycling trough trophic cascades. As predators are often sensitive to land use change and intensification, these findings suggest that loss of belowground predators may result in increased C losses following litter decomposition.

How to cite: Lejoly, J., Wang, Y., van Hoof, E., Favre, V., Quist, C., Geisen, S., and Veen, C.: Trophic cascades in simplified soil food webs and consequences for carbon cycling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7897, https://doi.org/10.5194/egusphere-egu24-7897, 2024.

09:45–09:55
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EGU24-10509
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On-site presentation
André Franco and Laureano Gherardi

To understand carbon dynamics and how it is affected by ongoing climate change, we need a better appreciation of the belowground ecological interactions driving plant allocation patterns and ecosystem carbon fixation. It has become increasingly clear that belowground root inputs contribute significantly more to soil carbon sequestration than aboveground plant inputs. Yet, current understanding of the role of belowground root herbivory in ecosystem carbon dynamics is weaker than that of aboveground herbivory. We addressed this gap by merging three complementary and novel areas of research, namely testing how: (1) biotic interactions between plants and nematode herbivores affect belowground biomass allocation in grasses; (2) how these biotic interactions and their consequences for biomass allocation are modified by a pervasive perturbation, namely drought, which is becoming more intense and frequent; and (3) how belowground responses vary across contrasting ecosystems. Results of complementary controlled and multi-site field experiments showed that: (1) nematode root herbivory modulates the relationship between water availability and belowground biomass allocation; (2) drought-induced increases in nematode root herbivory impede plants from increasing biomass allocation to roots under drought; and (3) these nematode effects are greater in magnitude in mesic compared to semiarid and arid grasslands. These findings suggest that the fate of carbon in mesic ecosystems under increasing drought frequency is highly influenced by nematode herbivores in the soil, and encourage investigations into the unknown consequences for soil carbon formation and persistence.

How to cite: Franco, A. and Gherardi, L.: The influence of belowground nematode herbivory on carbon allocation in drought-prone ecosystems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10509, https://doi.org/10.5194/egusphere-egu24-10509, 2024.

09:55–10:05
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EGU24-729
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ECS
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On-site presentation
Janey Lienau, Marlyse C. Duguid, and Oswald J. Schmitz

The dominant paradigm is that nitrogen cycles from plants to soil organic matter, being released in mineral form in the soil after organic matter is decomposed by microbes to be taken up again by plants. It is generally held that the process of decomposition is the rate-limiting step in the cycle. Ground dwelling macroinvertebrates may play a large role in ecosystem function by mediating microbe decomposition via predation and could be key links between plant litter and nitrogen availability in soil nutrient cycles. Ground beetles (Carabidae) are an abundant family of soil invertebrates that prey on groups of decomposing invertebrates. The goal of this study was to develop how predation from ground beetles contributes to nitrogen cycling as forests age. We hypothesized that ground beetles in young and old forests would indirectly impact available nitrogen. Our approach to addressing predator impacts on nitrogen cycling in forest soils was an experiment in young and old forest stands at Yale-Myers Forest in the northeastern United States using mesocosm cages stocked with predatory and detritivore ground beetles to create a trophic cascade over 68-days. Both forest sites had five blocks of three clustered treatments (n = 30). Treatments consisted of a control, detritivore, and predator and we took soil cores in each cage to assess available nitrogen. We used standard mesocosm cages that were designed for research on arthropod trophic interactions in ecosystems 1 m2, 0.8 m tall cylindrical mesocosms constructed with a scaffolding covered with fine mesh aluminum stocked with live beetles. We conducted a series of linear mixed-effect models in RSudio from the nlme package and lme() function in R Studio to predict the delta nitrogen mineralization rate by treatment in both young and old forests separately. We used ground beetle treatment as a fixed effect and block as a random effect to account for variation in microsite differences. Here we show differences in available nitrogen between forest types (P-value = 0.03). Our hypothesis that predators would impact available nitrogen was supported in young forests. Net nitrogen mineralization (P-value = 0.007) was consistently higher in the predator treatments compared to the control. In conclusion, this study suggests predator top-down control may be important for soil nitrogen availability in temperate forest soil via mediating microbe decomposition. Macroinvertebrates and their food web interactions in the soil should be further investigated and included in soil biogeochemical models.

How to cite: Lienau, J., Duguid, M. C., and Schmitz, O. J.: Ground beetles trophic interactions alter available nitrogen in forest soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-729, https://doi.org/10.5194/egusphere-egu24-729, 2024.

10:05–10:15
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EGU24-7464
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On-site presentation
Anton Potapov, Sergey Thurikov, Stefan Scheu, and Alexei Tiunov

Soil biogeochemical cycles are regulated by soil food webs. However, variation of soil food web structure and functioning across key environmental gradients remains unknown, hampering generalisations of any suggested links between fauna and biogeochemistry. Here, we used two complementary approaches to quantify soil animal food web variation across forest types, from southern taiga to rainforests. First, we applied the energy flux approach to explore patterns of energy distribution across micro-, meso- and macrofauna. We showed that tropical soil food webs have consistently higher energy flux, proportionally higher predation rates (31 vs 18-27% of the total energy flux) and relied more on the plant energy channel (21 vs 10%), but less on the bacterial (5 vs 9-18%) and litter energy channels (14 vs 18-32%), than temperate soil food webs. Second, we compiled a large database (>8000 records) of stable isotope composition of soil animals to see how detritivory and microbivory in soil animal communities change with environmental temperature and litter quality. Despite little effect of temperature, shift in 15N concentrations suggested that in most cases low litter quality (high %C and low %N) result in a switch from feeding directly on litter to feeding on microorganisms. Thus, soil animals change their functional role from competitors to consumers of microbes. Our studies show how the functioning of soil animal food webs changes across biomes with different climate and litter quality and summarise functional roles animals play in different biomes.

How to cite: Potapov, A., Thurikov, S., Scheu, S., and Tiunov, A.: Structure and functioning of soil animal food webs across temperate and tropical forests, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7464, https://doi.org/10.5194/egusphere-egu24-7464, 2024.

Posters on site: Tue, 16 Apr, 16:15–18:00 | Hall X1

Display time: Tue, 16 Apr, 14:00–Tue, 16 Apr, 18:00
X1.13
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EGU24-3228
Jan Frouz

Earlier studies show that across all biomes about half of litter fall is consumed by soil fauna. Part of that litter can be incorporated in to mineral soil by process called bioturbation. Soil fauna bioturbation may affect various processes related to decomposition and stabilization of organic matter, soil water retention, formation of habitat for soil biota and so on. 

In this contribution I summarized global experiment aimed to estimate amount of litter which is incorporated in soil by soil fauna bioturbation.  To do so a I used a filed mesocosm experiment located in 23 locations in all major biomes of northern hemisphere from tundra to tropical rain forest.   Mesocosms containing litter and mineral soil in two separate compartments were exposed in soil litter interface. These mesocosm were either accessible to soil fauna or not which allow to measure removal of litter from soil surface as well as accumulation of litter in mineral soil as well as overall loss of litter from the mesocosm. Mesocosm were supplied in local litter. Overall fauna significantly increased carbon accumulation in mineral soil. The effect was higher in temperate and tropical climate and lover in cold and dry biomes. Amount of carbon incorporated by fauna into mineral soil significantly positively correlated with actual evapotranspiration and negatively with CN ratio of litter.  In comparison with previous studies of litter consumption it can be estimated that about half of litter consumed by soil fauna is incorporated in mineral soil.  To put this together it appears that in natural ecosystem about half of annual litter fall is consumed by soil fauna and half of that fauna incorporate into mineral soil. This makes soil fauna important player in global carbon cycle

How to cite: Frouz, J.: Global pattern of soil fauna drivel litter mixing incorporation to soil in relation to climate and litter quality , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3228, https://doi.org/10.5194/egusphere-egu24-3228, 2024.

X1.14
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EGU24-6636
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ECS
Wiktoria Ogar, Rüdiger M. Schmelz, Bartłomiej Woś, Tomasz Wanic, Marcin Pietrzykowski, and Agnieszka Józefowska

Soils around the world are facing increasing degradation due to human activities such as mining. This degradation adversely affects soil functioning and, consequently, the ecosystem services it provides. Therefore, our research concerns various strategies for restoring forest ecosystems at such sites. Soil fauna can play a key role in restoring degraded soils, positively influencing their properties, especially in the case of newly formed soils. Providing an influx of organic matter, such as through afforestation, can promote the growth of microorganisms and subsequently facilitate the emergence of soil fauna and the process of soil formation.

Our main research question is how different tree species and soil disturbances, in this case especially mining, affect enchytraeid and earthworm communities and how soil fauna contribute to the soil-forming process in post-mining soil. We selected sandy soil in sandpit excavations afforested with various tree species, including Scots pine (Pinus sylvestris L.), European larch (Larix decidua Mill.), Silver birch (Betula pendula Roth) and European oak (Quercus robur). Soil profiles were described and samples were taken for basic soil analysis, including pH, soil organic carbon and nitrogen content, and soil porosity. In addition, earthworms and enchytraeids were collected from all plots to assess the density and species diversity of the soil fauna.

Based on the WRB classification, the studied soils were classified as Arenosols. The studied soils generally showed acidic pH, subangular structure in the upper layers and slightly acidic pH with a lack of structure in the subsoil. Slight differences were observed in the thickness of the humus layer between the soil profiles. Areas undergoing reclamation after sand mining were characterized by low enchytraeid densities. The Shannon index reached the highest value for the birch site and was 0.64 and the lowest for the pine site and was 0.08. In turn, the highest density of enchytraeid occurred at the oak site and was 34574 ind. m-2 and the lowest at the larch site and was 10123 ind. m-2. Soils under deciduous species show higher density and biomass of earthworms compared to soils under coniferous species. The highest density of earthworms was noted at the birch site and was 25 ind. m-2 and the lowest at the larch site and was 0 ind. m-2. It is worth noting that the birch site showed the highest diversity of enchytraeid species and highest abundance of an earthworm species. The density of the studied soil fauna was not high, but their presence and diversity may indicate a positive trajectory of changes occurring in these soils. 

This research was funded by The National Science Centre, Poland, grant No. 2021/42/E/ST10/00248. The analyses were performed in the Laboratory of Forest Environment Geochemistry and Reclaimed Areas, University of Agriculture in Krakow.

Key words: earthworm, enchytraeid, sand mine, sandy soil

How to cite: Ogar, W., Schmelz, R. M., Woś, B., Wanic, T., Pietrzykowski, M., and Józefowska, A.: Soil fauna presence in post-mining area after afforestation with diverse tree species, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6636, https://doi.org/10.5194/egusphere-egu24-6636, 2024.

X1.15
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EGU24-6768
Gwenaëlle Lashermes, Luna Vion-Guibert, Yvan Capowiez, Gonzague Alavoine, Ludovic Besaury, Olivier Delfosse, and Mickaël Hedde

Earthworms contribute to numerous ecological functions by impacting the soil biogeochemistry. Through their bioturbation activity, they modify the soil structure and the distribution of its components. By ingesting soil and secreting mucus, earthworms bring microorganisms and organic matter into contact under conditions that favor microbial activity, thus stimulating the mineralization of carbon and nutrients by soil microorganisms. While these effects are relatively well known for the dominant agricultural species, the diversity of earthworm habitats and functional traits suggests that not all would have the same impact.

Recently, Capowiez et al. (2024) proposed a classification of earthworms into functional groups (sensu Hedde et al. 2022) in relation to bioturbation (reorganization of soil particles). The aim of our work was to study the linkages between the organic matter mineralization and soil bioturbation functions performed by earthworms. We aimed to assess the different impacts on biogeochemical cycles of earthworm species belonging to different bioturbation functional groups.

Six earthworm taxa were incubated in soil columns in the presence of alfalfa litter: Octodrilus complanatus (intense tunneler or anecic), Lumbricus terrestris and Aporrectodea caliginosa meridionalis (burrower or epi-anecic), Alollobophora chlorotica (shallow biotubator or epi-endogeic), Octolasion cyaneum (deep bioturbator or hypo-endogeic), Microscolex dubius (intermediate). After 6 weeks of incubation, the gallery networks were scanned, and pictures were analyzed. The columns were then opened, and soil samples were taken to quantify carbon and nitrogen mineralization, as well as the abundance and diversity of microorganisms in different soil compartments: casts (earthworms surface excrement), drilosphere (soil around the galleries) and surrounding bulk (soil not directly altered by earthworms).

The results on earthworm bioturbation activity were consistent with those obtained by Capowiez et al. (2024) and made it possible to distinguish five functional groups (A. c. merdionalis and O. cyaneum being indistinguishable from each other). The presence of earthworms increased carbon and nitrogen content and stimulated mineralization in the casts but had low impact on the drilosphere. Biogeochemical and microbiological measurements tended to separate the taxa studied into two groups: species that stimulated carbon and nitrogen mineralization in the casts, by selecting bacteria (during passage through the digestive tract) and maintaining high humidity, and those that had little effect on microbial communities and their activity. Furthermore, the results showed that L. terrestris, often used as a "model" worm, had a higher impact on soil structure and on the mineralization of organic matter than most of the other taxa studied, and is therefore not representative of the role of earthworms in soils.

References:

Capowiez, Y., Marchán, D., Decaëns, T., Hedde, M., & Bottinelli, N. (2024). Soil Biology and Biochemistry, 188, 109209.

Hedde, M., Blight, O., Briones, M. J., Bonfanti, J., Brauman, A., Brondani, M., ... & Capowiez, Y. (2022). Geoderma, 426, 116073.

 

How to cite: Lashermes, G., Vion-Guibert, L., Capowiez, Y., Alavoine, G., Besaury, L., Delfosse, O., and Hedde, M.: Earthworms impact on soil organic matter mineralization sheds new light on their ecological groups , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6768, https://doi.org/10.5194/egusphere-egu24-6768, 2024.

X1.16
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EGU24-7303
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ECS
Péter Garamszegi, Karina E. Clemmensen, Thomas Keller, Björn D. Lindahl, and Eveline J. Krab

Earthworms are considered ecosystem engineers due to their remarkable influence on the soil system. While creating the drilosphere in the soil, they interact with microorganisms both directly and indirectly and thereby greatly affecting soil carbon and nutrient cycling. Earthworm activity may reshape soil microbial communities in several ways. Amongst others, earthworms may cause shifts in microbial communities and activities/processes by damaging hyphal networks, selectively feeding on substrates hosting certain bacteria and fungi, and by redistributing nutrients in the litter-soil continuum of the soil. However, interactions between earthworms and soil microbes, especially fungi, are poorly understood, and the mechanisms by which earthworms affect microorganisms are challenging to study. First, given the widespread presence of earthworms, finding soils that have not been previously affected by earthworms is difficult. Second, controlled laboratory incubation experiments generally exclude certain functionally important groups of fungi such as plant-associated ectomycorrhizal (EcM) fungi. In our recently initiated project, we aim to study earthworm influence on soil fungal communities and associated soil biogeochemical processes by introducing soil-dwelling earthworms into to date yet uncolonised northern forest soils. Therefore, we established mesocosm boxes filled with soil turfs including tree saplings from northern boreal forests and placed them in an experimental forest in southern Sweden. Later on, we will introduce earthworms (Aporrectodea and Lumbricus spp) into the mesocosms and measure (depth specific) changes in microbial communities and genes using RNA and DNA sequencing. Potential microbial changes will be related to measurements of carbon and nitrogen cycling, such as carbon-dioxide flux measurements and soil mineral nitrogen content analysis in the growing season after earthworm introduction.

How to cite: Garamszegi, P., Clemmensen, K. E., Keller, T., Lindahl, B. D., and Krab, E. J.: Earthworm-microbe interactions: what can we learn from controlled earthworm introduction into boreal forest soil?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7303, https://doi.org/10.5194/egusphere-egu24-7303, 2024.

X1.17
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EGU24-9819
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ECS
Gabriel Boilard, Ashley Cameron, and Miloslav Šimek

     Forested riparian buffer strips (FRBS) are common in temperate agroecosystems due to their ability to sequester nutrients from agricultural runoff and to sequester carbon. The full environmental benefits of FRBS can only be evaluated, however, by accounting for a wide range of criteria that go beyond stream water quality. For example, it is important to determine the net greenhouse gas (GHG) balance of FRBS relative to adjacent agricultural fields. It is also important to identify the factors controlling these GHG emissions in order to propose optimal FRBS designs that maximize their environmental benefits. One such factor is the spread of non-native earthworms, whose burrowing activities may modify soil emission rates of CO2, N2O and CH4. To test the effects of earthworms on GHG emissions, microcosm studies were conducted using a replicated factorial design comprising of three soil origins (deciduous FRBS, coniferous FRBS, agricultural field) × two soil textures (field conditions, high clay) × three EW life habits (anecic, endogeic, no earthworms). At different intervals over the course of a 10-week trial, we measured net CO2 emissions under aerobic conditions, as well as potential N2O emissions in microcosms amended with acetylene gas.  In a separate trial using the same experimental design, we measured gross production and consumption rates of CH4, in both aerobic and anaerobic conditions, using an 13CH4 isotope dilution technique. Anecic earthworms had a positive effect on soil CO2 and denitrification, which decreased after a few weeks. Increasing soil clay content had a negative effect on the emission of these two GHGs. Additionally, soils from FRBS emitted more CO2, N2O and CH4 than soils from agricultural fields. Gross CH4 consumption rates were greater under aerobic than aerobic conditions, especially under deciduous trees.  Results suggest that the inclusion of trees in riparian buffer strips combined with the introduction of non-native earthworm species could substantially increase GHG emissions of agroecosystems and mitigate the environmental benefits of FRBS.

(Note: The first and second authors contributed equally to this presentation).

How to cite: Boilard, G., Cameron, A., and Šimek, M.: The inclusion of trees and the introduction of non-native earthworms may increase greenhouse gas emissions from riparian buffer strips.  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9819, https://doi.org/10.5194/egusphere-egu24-9819, 2024.

X1.18
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EGU24-10318
Thi Hong Van Tran, Agnieszka Józefowska, Bartłomiej Woś, Marcin Pietrzykowski, Tomasz Wanic, Rüdiger M. Schmelz, and Jan Frouz

Soil fauna, particularly enchytraeids and earthworms, play a crucial role as soil engineers, actively contributing to nutrient cycling through the breakdown and ingestion of litter material. These organisms engage in intricate interactions with microorganisms responsible for decomposing and mineralizing detritus. The present study seeks to delve into the complex interplay among tree species, charcoal presence, and soil fauna within post-fire forest ecosystems. The investigation took place in Rudziniec, Poland, a site that witnessed one of Europe's largest fires in 1992. Two delineated areas were observed: one with post-fire charcoal presence and another with removed charcoal. Four distinct tree species—pine (Pinus sylvestris L.), larch (Larix decidua Mill.), birch (Betula pendula Roth), and oak (Quercus robur L.)—were selected as representative species for the study. Samples were obtained from locations adjacent to the trees at a depth of 0-10 cm for echytraeids and at a depth of 0-25 cm for earthworms. The study elucidates the impacts of post-fire charcoal removal or retention on soil fauna across diverse tree species. When considering the various tree species, enchytraeid density was higher in coniferous trees (pine and larch) compared to deciduous trees (birch and oak). Among these, oak trees exhibited the highest enchytraeid species diversity, yet their density was lowest (60944 ind.m-2). Among experimental plots, in birch plots with post-fire charcoal retention, enchytraeid density was lowest (27470 ind.m-2); conversely, in charcoal removal plots, it showed the highest number with 105355 ind.m-2. Regarding earthworm biodiversity, a maximum of two species were observed across all plots. Earthworm density was lower in coniferous trees (12.65 ind.m-2 in pine and 10.67 ind.m-2 in larch) compared to deciduous trees (20.09 ind.m-2 in birch and 14.67 ind.m-2 in oak). With charcoal presence, earthworm density sharply decreased in coniferous trees while increasing in deciduous trees. A similar trend was observed in earthworm biomass. Among all experimental plots, the highest biomass value was found in pine trees with charcoal removal (4.54 g.m-2) whereas the lowest value with charcoal presence (0.35 g.m-2). These differences suggest an intricate relationship between post-fire charcoal management, tree species, and their consequential impact on soil fauna. The insights gathered from this study hold valuable implications for informing ecosystem management and restoration strategies, contributing to a more comprehensive understanding of the intricate dynamics within post-fire environments.

This research was funded by The National Science Centre, Poland, grant No. 2021/42/E/ST10/00248. The analyses were performed in the Laboratory of Forest Environment Geochemistry and Reclaimed Areas, University of Agriculture in Krakow.

How to cite: Tran, T. H. V., Józefowska, A., Woś, B., Pietrzykowski, M., Wanic, T., Schmelz, R. M., and Frouz, J.: The Impact of Tree Species and Charcoal on Soil Fauna in Post-Fire Forest Ecosystems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10318, https://doi.org/10.5194/egusphere-egu24-10318, 2024.

X1.19
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EGU24-16422
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ECS
Rahul samrat and Wolfgang wanek

Belowground (soil) communities are highly diverse and encompass higher plants, bacteria, fungi, protists, invertebrates and vertebrates. The feeding relationships are as diverse, ranging from symbiotic associations (e.g. mycorrhizae), saprotrophs, grazers, shredders, predators and parasites. These material flows underly the biogeochemical functions of soils, driving organic matter decomposition, soil carbon sequestration, nutrient recycling and greenhouse gas emissions. Despite the importance of understanding the structure and dynamics of such complex soil food webs we are still lacking quantitative and detailed approaches to characterize them. Recently lipidomics analysis of intact polar lipids of soil communities has emerged indicating its potential to allow disentangling the food web structure beyond just abundances of bacteria and fungi based on phospholipid fatty acids or amplicon sequencing data, but extending this analysis across the whole soil food web including its base, higher plants, and including higher consumer levels with diverse protists and invertebrates Our study introduces and develops an untargeted lipidomics platform, employing reversed-phase liquid chromatography and electrospray ionization tandem mass spectrometry (UPLC ESI Orbitrap MS), to examine the intact polar lipidomes of soil biota. With advanced high resolution mass spectrometry and a newly adopted bioinformatics toolbox, we analyze lipidomes from complex soil communities and from pure cultures and single species, including plants, archaea, bacteria, fungi, protists (amoebozoa, ciliophora, cercozoa, etc.), collembola, mites, nematodes, and other soil fauna, as well as their diets. Our workflow facilitates the rapid identification and quantification of thousands of unique intact polar lipid molecules, representing a variety of biological classes, which we currently analyze for their biomarker potential, for being indicative for the presence and activity of specific groups of soil organisms. Utilizing this method of biomarker analysis, finally in combination with isotopic tracing into the fatty acyl residues (containing carbon, hydrogen and oxygen) and the lipid head groups (containing additionally nitrogen, sulfur and phosphorus), is expected to provide valuable quantitative insights into the structure of soil food webs and their activity and matter transfer, by following the incorporation and transfer of isotopically labeled matter and how this responds to climate and land use change. Thereby we foresee to improve our understanding of the contributions made by soil organisms to the stability and function of soil ecosystems, thus providing a foundation for ongoing ecological and environmental research.

How to cite: samrat, R. and wanek, W.: Unraveling the structure and function of soil food webs using an untargeted lipidomics approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16422, https://doi.org/10.5194/egusphere-egu24-16422, 2024.

X1.20
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EGU24-18389
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ECS
Philipp de Jong, Patrick Schleppi, and Frank Hagedorn

Earthworms may act as double-edged swords for soil organic matter (SOM). While they can enhance organic matter (OM) mineralization via increased microbial activity they can also elevate OM stabilization in aggregates as particulate or mineral-associated OM. In this study, we are testing this potentially opposing impact in beech-dominated (Fagus sylvatica L.) mixed forests on limestone, a forest ecosystem with particularly high earthworm activity. A specific focus lies on OM transformation along the continuum from the forest floor (O horizons) to mineral soil (A horizons). The forest floor can represent a substantial OM-pool which is an important source for SOM formation via bioturbation or leaching but can be vulnerable to alterations due to climate change. In a lab mesocosm experiment, we are incubating local earthworm species in soil columns consisting of O and A horizons from two contrasting beech forest sites from 600 and 1250 m elevation in the Swiss Jura Mountain range. Both sites have a mull-type forest floor with the high-elevation site exhibiting an Of horizon present throughout the year while an Of horizon is not present all year at the low-elevation site. We established four earthworm treatments for each site all including the respective mineral soil and forest floor: (1) no earthworms, (2) two Octolasion cyaneum S., (3) one Lumbricus terrestris L., and (4) two O. cyaneum together with one L. terrestris. In this setup, the Ol horizon was replaced with beech litter highly enriched with 13C, 15N, and 2H. Soil respiration (CO2) and leaching (C, N, and H in dissolved OM) are repeatedly measured. Total respiration (12C and 13C) is measured weekly for the first four months and biweekly afterward. Every two months fluxes from A and O horizons are measured separately. After approximately 4 and 10 months each, a set of mesocosms is harvested to investigate isotope enrichment in earthworm biomass, cast, physical soil fractions, PLFAs, and microbial necromass. We find first indications for stabilization of new litter input as, under similar total CO2 fluxes, the litter-derived fraction is higher for treatments without worms. However, if both earthworm species are present, the cumulative heterotrophic respiration is elevated compared to the treatments involving only one earthworm species and the no-earthworm treatment. This is presumably due to higher earthworm density and, therefore, increased bioturbation. In contrast, we find no differences in the amount of dissolved organic matter leached out of the mesocosms between the treatments so far. X-ray CT scans will inform us about earthworm behavior within the mesocosms. This will help us understand how their activity translates into the vertical distribution of the isotopic label.

How to cite: de Jong, P., Schleppi, P., and Hagedorn, F.: The role of earthworms in the organic matter cycling of forest floors in temperate forests – A mesocosm experiment with labeled beech litter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18389, https://doi.org/10.5194/egusphere-egu24-18389, 2024.

X1.21
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EGU24-18778
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Carolyn-Monika Görres

Soils harbor a diverse fauna, ranging in size from <200 µm to several cm. These animals are direct producers of greenhouse gas (GHG) emissions via their respiratory and metabolic activities and can indirectly change soil carbon and nitrogen cycling by changing physical, chemical and biological soil properties, e.g. through bioturbation, defecation, herbivory, and litter fragmentation and redistribution. In addition, they can create microhabitats which offer more favorable conditions to microorganisms than bulk soil. Thus, soil fauna is able to substantially effect the spatial and temporal variability of GHG fluxes in ecosystems. However, emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from and associated with soil fauna remain poorly quantified and have been limited to only a few regions and species. The literature review presented here gives an overview of GHG emission studies addressing soil fauna taken place since 2010. For each GHG (CO2, CH4 and N2O) the keywords “emission* OR flux*” were combined with keywords querying different soil fauna groups. The initial search using the databases Web of Science Core Collection and Lens.org resulted in 282 and 531 journal articles, respectively, of which 165 studies were duplicates. This literature (n = 648) is being screened according to the following categories: i) location of study (geographical location, field, laboratory), ii) soil type, iii) ecosystem type, iv) species, v) GHG fluxes, and vi) methodologies (flux measurements, species monitoring). Based on this, the current state of knowledge, research gaps and methodological challenges will be identified to provide ideas and guidance for the design of future research projects trying to further our understanding of the quantitative role of soil fauna in the soil carbon and nitrogen cycle in natural and managed ecosystems.

How to cite: Görres, C.-M.: Greenhouse gas (CO2, CH4, N2O) emissions from soil fauna – what have we learned over the past decade?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18778, https://doi.org/10.5194/egusphere-egu24-18778, 2024.