This session highlights research that integrates microbial physiology and diversity into our understanding of soil biogeochemistry under global change. Contributions range from controlled studies with microbial isolates to ecosystem-level assessments across diverse climates, employing flux quantification techniques and advanced approaches such as omics, isotope tracing, microscopy, and spectroscopy. We feature empirical and theoretical studies addressing soil microbial resistance, resilience, and adaptation to single and multi-factorial climatic disturbances, as well as research on the interactions between soil microorganisms, plants and fauna. Join us to exchange ideas, share new findings, and discuss how linking soil microbes to ecosystem processes can improve our predictions of ecological responses in a rapidly changing world.
Plants and their soil microbial communities are connected by plant-root exudates that shape the soil microbiome. Monocultures of plants give a clearer plant-soil signal than mixtures of plant species, but the latter is what we deal with in natural systems. Grasses, herbs and legumes and their plant-root traits all have their own exudate types that alter plants and soil communities to cope with prolonged periods of drought and with repelling or attracting plant pathogens or symbionts. Having an insight in how plants shape soil microbiomes and how soil microbiomes shape plant communities are therefore crucial to sustain soil health and food security for the future but also important in the restoration of degraded soils. This talk will cover some possibilities to influence soil quality with plants steering the microbiome and how the microbiome steers the plant community in return. For the future of our planet it will be important to use plant-soil interactions to keep our soils healthy and resilient to ensure food security for the generations ahead. My current and past work focusses on plant-soil interactions and microbiome steering via plants to increase soil carbon stabilization. I pledge that fungi are superhero’s in this respect because they are very active in most soils even when low in biomass. Moreover, fungi have a high carbon use efficiency and if they are hyphal, their necromass tissue can be resilient against quick decomposition, and therefore can potentially contribute to stable carbon inputs.
How to cite: Morriën, E.: Using plant-soil-microbe interactions to retain soil functions under global change, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11469, https://doi.org/10.5194/egusphere-egu26-11469, 2026.
Microbial growth and carbon use efficiency (CUE) play a central role in soil organic carbon (SOC) cycling by regulating microbial biomass production and subsequent necromass contributions to persistent SOC pools. Due to dynamic responses of CUE to environmental changes, it remains unclear how microbial physiological trade-offs translate into SOC stabilization via necromass retention. In this study, we investigated how microbial respiration, growth, and CUE are regulated by land-use type, management intensity, and soil properties across 300 grassland and forest plots in three regions of Germany. We aim to disentangle the abiotic and biotic drivers of microbial contribution to SOC accumulation along gradients of land-use intensity and biodiversity.
Grasslands exhibited higher microbial growth and respiration than forests (growth ≈ 0.35 vs 0.12 mg C kg⁻¹ h⁻¹, respiration ≈ 2.3 vs 1.0 mg C kg⁻¹ h⁻¹), while CUE did not differ between land-use types. In forests, tree species strongly influenced microbial physiology with higher growth and CUE in deciduous stands than in coniferous stands. Management intensity in grasslands, particularly nitrogen inputs, exerted positive indirect effects on microbial growth and CUE, whereas forest management had predominantly negative effects on CUE through direct and indirect changes in abiotic soil properties. Microbial biomass carbon and soil pH emerged as key drivers in forests, while grasslands showed more dynamic responses, likely driven by resource availability in soil.
To examine how microbial growth and carbon use efficiency (CUE) translate into necromass accumulation, we compared organic soils derived from degraded peat with mineral soils at different depths that differ fundamentally in substrate availability and soil properties. Mineral soils contained a higher proportion of microbial-derived carbon per unit SOC than organic soils, despite greater substrate availability and higher microbial activity in organic soils, consistent with stronger microbial necromass retention in mineral soils.
Together, these results show that microbial carbon dynamics and contributions to SOC are regulated by land use, management, and soil type through distinct controls on microbial growth, carbon use efficiency, and necromass retention, thereby influencing SOC persistence across managed ecosystems.
How to cite: Jose, J., Glaser, B., Kaiser, K., Mehrotra, A., Goldmann, K., Prada Salcedo, L. D., Schoening, I., Schrumpf, M., and Bi, Q.: From microbial physiology to soil carbon stabilization: Controls across land use, management, and soil types, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16794, https://doi.org/10.5194/egusphere-egu26-16794, 2026.
Carbon use efficiency (CUE) of microbial communities in soil quantifies the proportion of organic carbon (C) taken up by microorganisms that is allocated to growing microbial biomass as well as used for reparation of cell components. This C amount in microbial biomass is subsequently involved in microbial turnover, partly leading to microbial necromass formation, which can be further stabilized in soil. To unravel the underlying regulatory factors and spatial patterns of CUE on a large scale and across biomes (forests, grasslands, croplands), we evaluated 670 individual CUE data obtained by three commonly used approaches: (i) tracing of a substrate C by 13C or 14C incorporation into microbial biomass and respired CO2 (hereafter 13C-substrate), (ii) incorporation of 18O from water into DNA (18O-water), and (iii) stoichiometric modelling based on the activities of enzymes responsible for C and nitrogen (N) cycles. The global mean of microbial CUE in soil depends on the approach: 0.59 for the 13C-substrate approach, and 0.34 for the stoichiometric modelling and for the 18O-water approaches. Across biomes, microbial CUE was highest in grassland soils, followed by cropland and forest soils. A power-law relationship was identified between microbial CUE and growth rates, indicating that faster C utilization for growth corresponds to reduced C losses for maintenance and associated with mortality. Microbial growth rate increased with the content of soil organic C, total N, total phosphorus, and fungi/ bacteria ratio. Our results contribute to understanding the linkage between microbial growth rates and CUE, thereby offering insights into the impacts of climate change and ecosystem disturbances on microbial physiology with consequences for C cycling.
How to cite: Kuzyakov, Y. and Hu, J.: Microbial Carbon Use Efficiency and Growth Rates in Soil: Global Patterns and Drivers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7686, https://doi.org/10.5194/egusphere-egu26-7686, 2026.
Microbial communities are central to soil ecosystem function. However, the extent to which functional diversity is conserved across communities, providing resilience to environmental change, remains uncertain. Here, we investigated how microbial legacy and soil properties shape community assembly and function, by cross-inoculating distinct microbial communities into sterilised soils from agricultural and semi-natural habitats within a 6 km radius. Over a 10-month incubation, the soil environment drove microbial community convergence at high taxonomic ranks, but fine-scale community composition and functional outcomes remained distinct. Distinct microbial communities showed a ‘home-field advantage’ in soil carbon use that increased cumulative respiration by 16-26% in agricultural soils and by 26-84% in semi-natural soils, demonstrating limited redundancy of broad ecological function between soil communities. Increased soil respiration in home-field soil communities was associated with significantly higher microbial diversity, indicating filtering selection driven by unfamiliar soil abiotic environments. Distinct communities also caused significant shifts in soil pH associated with contrasting inorganic nitrogen transformations, exposing limited conservation of specialised metabolic functions. In summary, microbial community legacy had a lasting influence on carbon and nitrogen cycling, and thus, the effects of anthropogenic land use change on soil microbial functional diversity will likely have substantial impacts on these key ecosystem processes. These findings have implications for the resilience of soil health and function under land use change and the potential for predicting the success of ecosystem restoration efforts, given the limited conservation in functional potential.
How to cite: Child, H. T., Friggens, N. L., Hook, C., Cressey, E. L., Wierzbicki, L., Joslin, G. R., Dowdle, J., Bore, E. K., van Groenigen, K. J., Tennant, R. K., and Hartley, I. P.: Land-use driven microbial community legacy shapes soil functionality, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3996, https://doi.org/10.5194/egusphere-egu26-3996, 2026.
Soil water availability is a key driver of microbial function and exerts influence on a variety of temporal scales—ranging from short-term pulse dynamics to long-term seasonal and annual precipitation patterns. Determining the impact of changing water dynamics on microbial growth and activity is crucial for assessing how changes in weather patterns may impact soil functionality. In Mediterranean grasslands, the first substantial annual rainfall after months of drought is a driver of substantial soil microbial activity and coincides with a pulse of CO2 emissions that can equal 10% of annual ecosystem productivity. To understand how altered precipitation regimes in semi-arid soils affect the microbial ecophysiological traits associated with soil carbon cycling, we use quantitative stable isotope probing (qSIP) to interrogate Who is where? and What are they doing? in wild soil communities collected during multiple points in the Mediterranean climate water-year. We also use multi-omics approaches, including metagenomics, metatranscriptomics, lipidomics, and metabolomics. Our qSIP results indicate only a fraction of the microbial community is actively growing at any moment or location; at the start of the growing season, the growing portion was 28%, 48% and 58% at wet, intermediate and dry sites. In a year-long study examining growth rates (measured with metagenomic qSIP) at three soil depths, we found distinct groups of actively growing organisms associated with seasonal changes in soil moisture. In a second study, we examined short-term pulse dynamics following the rewetting of dry soil. The first rain event after the dry season is a period of high growth and mortality where a large portion of annual carbon cycling occurs. To assess the impact of drought intensity on the rewetting response, soils were collected from two precipitation treatments in the field (50 or 100% mean annual precipitation) and rewet in a laboratory incubation. Wet-up triggered a rapid succession of bacterial populations, a large increase in the number of viruses (vOTUs), and strong indications of active viral lysis. We found that reduced precipitation influenced the composition of organic compounds in the soil—increasing tannin-like compounds and reducing the concentration of lipid-like compounds and changes the structure of trophic networks. Using metagenomics and 16S rRNA gene qSIP, we tracked growth and mortality following rewetting. We found that a history of limited moisture (50% precipitation) reduced both growth and mortality, demonstrating the interplay between annual/seasonal dynamics and short-term responses. Additionally, we found that growth after rewetting can be predicted from genomic traits such as genome size, codon bias, and GC content—indicating key features of fast-responding taxa to soil water pulse-dynamics. These results point to genome level traits that are predictive of microbial growth responses, and show how differences in legacy precipitation can influence microbial activities long after changes in soil moisture are no longer detectable.
How to cite: Pett-Ridge, J., Chuckran, P., Hernandez, L., Penev, P., Estera-Molina, K., Trubl, G., Kimbrel, J., Nicolas, A., Firestone, M., Banfield, J., and Blazewicz, S.: Microbes Persist: how soil moisture regimes shape the ecophysiology and C cycling of wild soil microbiomes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17213, https://doi.org/10.5194/egusphere-egu26-17213, 2026.
Climate projections predict an increase of frequency and/or intensity of extreme precipitation and drought events in temperate agroecosystems, leading to more pronounced drying–rewetting cycles (DWC). These moisture fluctuations trigger pulses of CO2 emissions from soil microbial activity—the Birch effect—which may destabilize soil organic carbon (SOC) stocks. However, large variability in the magnitude of this effect persists across studies, suggesting a strong influence of soil properties and land management, as well as methodological differences (e.g. lack of continuous CO2 measurement, inconsistent controls).
We addressed this issue through a controlled incubation of undisturbed soil cores from three French agricultural sites with contrasting textures (sandy, loamy, clayey) and management (conventional cropping, organic farming, conservation agriculture, permanent grassland). Soils were subjected to (i) five successive temperate DWC (1 week drying, 1 week rewetting, 70 days), (ii) five successive semi-arid DWC (6 weeks drying, 1 week rewetting, 245 days) and (iii) a constant moisture control. For each texture and management, the water content of the control was set to the mean value calculated over the temperate DWC. CO2 fluxes were monitored continuously, including during drying phases, enabling unbiased comparison of cumulative SOC mineralization across moisture regimes.
For both temperate and semi-arid scenarios, all soils showed pronounced CO₂ pulses upon rewetting, with declining amplitudes across successive cycles and strong modulation by soil texture and management. Relative to the constant-moisture control over the 70-day incubation, temperate DWC increased cumulative SOC mineralization for loamy soils managed conventionally and organically, and in sandy soils under permanent grassland. These differences were primarily explained by soil texture and water retention properties, with management effects depending on their interaction with clay content. Prolonged drought did not systematically increase SOC mineralization, indicating a context-dependent saturation of the Birch effect. Microbial biomass generally declined under longer droughts, whereas the metabolic quotient—defined as the ratio of cumulative mineralization during the last rewetting to final microbial biomass—increased with drought duration, except in grassland soils.
These results indicate a buffering effect of finer-textured and structurally stable soils, consistent with a joint biotic–abiotic control of the Birch effect shaped by soil texture and its interaction with land management. Recurrent DWC may progressively deplete labile SOC and destabilize protected SOC pools, with implications for SOC persistence under future climates. More mechanistic understanding is needed to improve predictions across soils, land uses, and management systems, and to integrate these dynamics into SOC models.
Keywords Drying–rewetting cycles ; Birch effect ; Soil texture ; Land use ; Agricultural management; Carbon mineralization ; Soil organic carbon; Climate change.
How to cite: Plaçais, T.: Soil texture and management jointly control the Birch effect under repeated drying–rewetting cycles, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13336, https://doi.org/10.5194/egusphere-egu26-13336, 2026.
Soil organic carbon (SOC) is a critical carbon pool on the planet, essential for soil functions and services such as climate regulation through C sequestration. SOC is dynamically recycled within microbial biomass and channelled into long term storage in the soil (the 'microbial carbon pump'). Understanding the biotic processes that drive SOC mineralization is essential for predicting the climate warming-carbon cycle feedback. The microbial pump is influenced by trophic interactions in the soil food web and SOC mineralization is a result of complex biotic interactions.
Here, we combined Tree-of-life sequencing (TOLseq; metatranscriptomic sequencing of ribosomal RNA for three-domain profiling of soil biota) with quantitative conversion factors which links transcript abundance to biomass, using standard parameters of microbial cell stoichiometry and physiology. We show how this can form the basis for energetic food web models, an approach we refer to as TOLmodel. The novel approach was applied on soil samples originating from natural grassland sites in Iceland (‘Forhot’ sites), where geothermal activity has created soil warming for more than 60 years, with soil warming gradients up to +6 °C used in this study. Field observations showed that warming reduced SOC stocks, but after years of warming SOC mineralisation had acclimated.
Our TOLmodel approach allowed the quantification of soil biota, aligning with laboratory measurements of microbial biomass carbon, and their SOC mineralization rates, aligning with measured CO2 efflux from the field site. Furthermore, the food web model revealed how decimated soil fauna under soil warming relaxed the top-down control of microbial growth increasing SOC mineralisation rate per unit microbial biomass six-fold during summer.
How to cite: Dahl, M., Protti- Sánchez, F., Groß, V., Burns, A., Söllinger, A., Hu, D., Bhattarai, B., Dumack, K., Metze, D., Ostonen, I., Janssens, I., Sigurdsson, B., Bahn, M., Richter, A., and Urich, T.: Quantifying the role of trophic guilds in soil organic carbon mineralization, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3071, https://doi.org/10.5194/egusphere-egu26-3071, 2026.
Methane (CH4)-temperature hysteresis, i.e., significantly higher CH₄ emissions in autumn compared to spring at equivalent temperatures, have been observed in wetlands globally. However, the biological basis for these seasonal changes in the effect of temperature on wetland CH₄ emissions remain unexplained.
Peat soil from four Arctic and sub-Arctic sites: Svalbard, Northern Norway, Arctic Canada, and Greenland, were collected for investigations of the mechanisms behind CH4-temperature hysteresis. In the laboratory, under anoxic condition, the peat soils were exposed to temperature changes in weekly 2 °C increments, from 2 °C to 10 °C and back to 2 °C, simulating an Arctic spring to autumn transition. Methane accumulation rates, methanogen substrate concentrations, total microbial and archaeal RNA and DNA content, and community composition and size were monitored throughout the experiments.
Three of the four examined soils (Svalbard, Northern Norway and Greenland) expressed significantly higher CH4 production rates during cooling compared to warming. This observation of CH4-temperature hysteresis under anoxic condition demonstrate that CH4-temperature hysteresis can result from anaerobic processes, while experiment replication demonstrated that CH4-temperature hysteresis, or the lack of it, were reproducible for the respective peatlands.
The timing and extent of accumulation and depletion of methanogenic substrates and the enhanced methane production rates during cooling in the three CH4 hysteresis-positive soils suggested that the methanogenic community itself, triggered by high substrate availability and a sufficient maximum temperature, is the major driver of CH4-temperature hysteresis. Furthermore, the observation that both soils dominated by acetoclastic (Svalbard and Greenland) and hydrogenotrophic (Northern Norway) methanogens can express CH4-temperature hysteresis, demonstrate that hysteresis is not restricted to one methanogenic pathway.
As only minor changes in the methanogenic community composition were observed during the experiments, CH4-temperature hysteresis was indicated to result from physiological responses of the existing methanogenic community. In the Svalbard soil, increased methanogen population sizes, as indicated by qPCR, suggested faster methanogen growth rates during cooling, potentially explaining hysteresis, but this effect was not observed in the remaining two hysteresis positive soils. Thus, other physiological rate-increasing mechanisms are also required to explain hysteresis. Correspondingly, increased expression of genes for rate-limiting enzymes in methanogenesis, as a response to temperature and substrate increase, were demonstrated in a separate heating experiment (2 °C to 10 °C) done on Svalbard peat soil.
We propose the following CH4-temperature hysteresis mechanism: Temperature induced imbalances between fermentation and methanogenesis at low temperatures and during heating leads to high methanogen substrate concentrations. The subsequent combination of excess substrate and reaching sufficiently high temperatures promote methanogen activity through faster growth and the buildup of rate-limiting enzyme pools for methanogenesis in the form of more new cells or larger enzyme stocks per cell. This expansion of the methane production bottleneck allows enhanced CH₄ production rates during subsequent cooling, until the depletion of substrate pools.
How to cite: Bjørdal, Y., Bender, K. M., Martin, V. S., Motleleng, L., Didriksen, A., Lindgård, B., Breines, E. M., Ahlers, L. S., Schmidt, O., Røjle Christensen, T., Scheel, M., Schmider, T., Richter, A., Söllinger, A., and Tøsdal Tveit, A.: Microbial mechanisms controlling methane-temperature hysteresis in wetlands., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20417, https://doi.org/10.5194/egusphere-egu26-20417, 2026.
High-latitude soils store a disproportionate share of global soil carbon (C) and nitrogen (N) and are expected to play a critical role in future greenhouse gas feedbacks to climate warming. Despite this importance, the mechanisms controlling N losses from subarctic soils under warming, particularly nitrous oxide (N₂O) emissions, remain poorly constrained, largely due to strong interactions between temperature and microbial resource availability. Here, we assessed how warming interacts with C and N availability to regulate microbial N₂O production and N priming in a subarctic grassland ecosystem.
Soils were collected from a subarctic grassland exposed to a natural geothermal warming gradient for two years and subsequently incubated in the laboratory at the same in situ temperatures (ambient, +2 °C, and +6 °C). We applied four substrate addition treatments (water control, glucose, ammonium nitrate, and combined glucose + ammonium nitrate) using highly 13C and 15N-enriched substrates, allowing isotopic partitioning of N2O sources and quantification of N priming.
Warming increased total N₂O emissions across treatments, but the magnitude and underlying mechanisms strongly depended on substrate availability. Nitrogen addition alone caused substantial accumulation of NH₄⁺ and NO₃⁻, stimulated N₂O emissions, and enhanced N₂O derived from native soil N, indicating strong positive N priming. This priming effect intensified with increasing temperature, consistent with accelerated microbial N turnover, and increased denitrification and nitrification rates under elevated inorganic N availability. In contrast, C addition reduced inorganic N accumulation and strongly suppressed N₂O emissions, indicating enhanced microbial N immobilization. Combined C and N addition reduced NH₄⁺ accumulation but not NO₃⁻ accumulation, moderated the temperature sensitivity of N₂O emissions, and shifted N₂O production toward substrate-derived N, suggesting tighter microbial coupling of C and N metabolism under balanced resource supply, reducing reliance on native soil N pools even under warming.
Together, these results show that warming-induced N₂O emissions from subarctic soils are highly contingent on microbial resource balance. Carbon availability can constrain N losses under warming, whereas excess N amplifies priming-driven emissions, with important implications for predicting high-latitude greenhouse gas feedbacks and soil N losses under climate change.
How to cite: Yu, J., Leticia Zevenhuizen, A., Gonzalez Mateu, M., Mattana, S., Richter, A., and Marañón-Jiménez, S.: Warming enhances nitrogen priming of N20 emissions in subarctic soils under high nitrogen availability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20087, https://doi.org/10.5194/egusphere-egu26-20087, 2026.
Soil microbial communities are rarely represented in soil models or with extreme simplifications due to their complexity. Acknowledging that temperature and moisture are the primary controls over microbial functional diversity, this research aims to determine the extent to which soil functional diversity can be predicted based on these factors. We used the aridity index (AI), as this easy-to-measure metric includes temperature and moisture. Following the YAS framework, a widely accepted trait-based approach to characterize soil microbial communities, we hypothesized that under an identical food source, the functional strategies employed by the community will go from high growth yield (Y) in humid areas to higher investment in stress tolerance (S) in arid areas. We also expected a trade-off between investment in S and Y, while relative investment in A (resource acquisition) should remain constant. We further hypothesized that AI is a decent predictor of the microbial investments into the Y, A, and S traits. We used the DEMENTpy model, an in silico simulator, to derive YAS investments for hypothetical soil microbial communities at five sites along an aridity gradient in Spain. We validated model simulations using mass loss from Rooibos tea samples from each site and employed a Dirichlet regression model to predict YAS investments, using AI. Contrary to the hypotheses, increasing aridity changes community investment from Y to A, with limited changes in S. The A strategy could be predicted considerably well based on AI, while Y and S could not. Together with further validation of our modeling results with experimental data, our findings lay the groundwork in deriving simple mathematical formulations that can be integrated into Earth system models, allowing for upscaling from genomes to Earth system processes.
How to cite: Chavez Rodriguez, L., Martens, R., and De Deyn, G.: Predicting Microbial Functional Diversity for Decomposition along an Aridity Gradient, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3200, https://doi.org/10.5194/egusphere-egu26-3200, 2026.
Nitrifying microbes play a central role in soil N cycling by controlling N transformations and the potential for N losses (including the greenhouse gas N2O). Yet, the drivers of nitrifier communities remain poorly resolved across global drylands, which cover more than 40% of terrestrial surface. A mechanistic, global scale understanding of the controls on nitrifiers is thus critical for forecasting dryland N cycling and N loss pathways under climate change and land-use pressures. Using a standardized global dryland survey spanning 98 dryland rangelands in 25 countries, we quantified the abundance of ammonia-oxidizing bacteria (AOB), and ammonia-oxidizing archaea (AOA) across contrasting vegetated and bare microsites (a defining feature of dryland landscapes). We applied (structural/linear) equation modeling to assess climatic, edaphic, geographic, grazing, and vegetation controls. Controls on nitrifier abundance differed between microsites. Vegetated microsites were mainly driven by soil resources: ammonium showed a positive relationship with AOB and the total abundance of nitrifiers, whereas soil organic C had a consistent negative effect. Bare microsites showed stronger climatic control, with AOA and total nitrifiers exhibiting a U-shaped response to mean annual temperature. We didn’t see any effects of increased grazing pressure on total nitrifiers. Overall, these results highlight microsite context as a key regulator of nitrifier communities across global dryland rangelands. They indicate that changes in vegetation cover and patch structure through their effects on vegetated–bare soil balance and canopy buffering are likely to be a key pathway by which ongoing global change restructures nitrifier abundance and nitrogen cycling in drylands.
How to cite: Alghamdi, N., Corrochano-Monsalve, M., and T. Maestre, F.: What shapes nitrifiers in drylands? Global drivers of AOA and AOB abundance across microsites, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13381, https://doi.org/10.5194/egusphere-egu26-13381, 2026.
Biological soil crusts (biocrusts) cover ~30% of global drylands and regulate biogeochemical cycles through microbial metabolic activities. Although nutrient scarcity profoundly influences biocrust microbial communities, the general principles governing their nutrient response dynamics remain unclear. Here, we employed controlled microcosms to investigate how differential nutrient supply reshaped the community structure and interspecies interactions of both biocrust bacterial and fungal assemblages. Our findings revealed that increased nutrient supply drove a shift from K- to r-strategists in bacterial communities, while fungal assemblages exhibited distinct response patterns among abundant, intermediate, and rare taxa. Network analysis demonstrated that nutrient supply increased node number, link number, average degree, and negative correlations, indicating intensified interactions in both bacterial and fungal communities. Keystone taxa analysis identified three oligotrophic bacteria, three copiotrophic bacteria, and two fungal hub taxa consistently present across nutrient levels. Furthermore, both bacterial and fungal community structures, as well as their interaction networks, were strongly correlated with soil nutrient availability, particularly total phosphorus, available nitrogen, and available potassium. This study establishes a unified mechanistic framework for nutrient-driven microbial assembly in drylands, highlighting taxon-specific responses and interactions. The findings provide actionable strategies for ecological restoration through optimized nutrient management and targeted manipulation of keystone microbial taxa.
How to cite: Zhao, L., Chen, N., Weber, B., Gu, S., and Li, X.: Nutrient Supply Shapes Microbial Assembly in Dryland Biocrusts: Taxon-Specific Responses and Network Reorganization, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21005, https://doi.org/10.5194/egusphere-egu26-21005, 2026.
Soil fauna and microbial communities are key drivers of soil organic matter turnover and nutrient cycling, but we are still far from unraveling the mechanisms underlying the full complexity of their interactions. While soil fauna is generally hypothesized to release microbes from bottom-up resource limitations, they could also exert a strong top-down control by either direct feeding or by shifting the stoichiometric balance of the soil solution, thus constraining microbial growth. To try filling this knowledge gap we report novel data on a microcosm incubation experiment in which we controlled the presence of meso and macrofauna and measured the flows of carbon (C), nitrogen (N) and phosphorus (P) from litter to the different soil pools and tracked their effects on a comprehensive set of microbial functioning variables which included growth rates, stoichiometry, enzyme activity, substrate degrading capacity, and rates of N and P mineralization and consumption. Additionally, we evaluated changes in the microbial community composition through 16S, ITS and 18S DNA marker sequencing. Soil macrofauna boosted the release of C, N and P from the litter pool. This led to a strong increase in dissolved organic C and a moderate increase in free amino acids, ammonium and phosphate concentration, thus resulting in a sharp increment of the C:N and C:P ratios in the soil solution. Microbial C and growth were greater in the microcosms with meso and macrofauna, but their C-use efficiency did not change. Macrofauna presence boosted the microbial gross production and consumption of amino acids, ammonium and nitrate, but P mobilization and uptake rates remained equal across treatments. The activity of beta-glucosidase also increased with macrofauna while N and P mining enzyme activities did not change. Overall, soil macrofauna strongly up regulated microbial communities by releasing them from C limitation.
How to cite: Peguero, G., Domene, X., Mattana, S., Asensio, D., Sanchez-Moreno, S., Fuchslueger, L., Schmidt, H., Richter, A., and Peñuelas, J.: Deciphering the mechanisms underlying soil fauna-microbe interactions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1925, https://doi.org/10.5194/egusphere-egu26-1925, 2026.
Microbial communities are central to soil biogeochemical cycling. They assimilate organic carbon and either allocate it to biomass or return to the atmosphere as CO₂. Assimilated carbon can support cell division (growth sensu stricto) and also the synthesis of storage compounds or osmolytes (growth sensu lato). Yet, microbial growth is commonly quantified solely based on cell division. Under steady-state conditions, the partitioning of carbon between replicative and non-replicative growth may remain relatively constant (balanced growth), but climate change likely alters microbial growth dynamics and C allocation to different processes (unbalanced growth).
In this study, we investigated responses of microbial growth and storage compound synthesis in a multifactorial climate change experiment (ClimGrass) that included 4 treatments: (i) future climate conditions (elevated temperatures, +3°C, and increased atmospheric CO₂ concentrations, +300 ppm), (ii) a twelve-week summer drought, and (iii) a combination of future climate conditions and drought, as well as (iv) an ambient control. For this study, samples were collected from May (at the onset of drought) to August to capture intensifying drought conditions. We measured deuterium incorporation from 2H-labelled water into PLFAs (phospholipid fatty acids) to quantify growth, and into NLFAs (neutral lipid fatty acids) and PHB (poly-3-hydroxybutyrate) to assess storage compound synthesis.
Over the progression of drought, bacterial mass-specific growth rates decreased more strongly than fungal growth rates, with fungi showing greater relative resistance to drought. Mass-specific NLFA production rates increased over the sampling period in all treatments, suggesting a seasonal increase in storage compound production that was not affected by drought or future climate conditions. However, the ratio of NLFA production to PLFA-derived growth indicated a shift in carbon allocation toward storage NLFA synthesis under drought. In contrast, PHB production rates exhibited no clear seasonal pattern. Yet, normalized to bacterial growth, PHB synthesis also significantly increased under drought in July and August.
In summary, although overall microbial activity declines, drought shifts C allocation from replicative growth to storage compound synthesis, consistent with microbes responding to prolonged summer droughts. This change in allocation of acquired carbon emphasizes the need to quantify both replicative (cell division) and non-replicative (storage) growth to interpret microbial responses and ecosystem feedbacks.
How to cite: Stein, L., Canarini, A., Fuchslueger, L., Schmidt, H., Ritter, V. M., Bahn, M., Schaumberger, A., and Richter, A.: Linking cell division and storage: seasonally intensifying drought shifts microbial C allocation towards storage, with relative fungal resistance, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16997, https://doi.org/10.5194/egusphere-egu26-16997, 2026.
The net effect of temperature variations on soil organic carbon (SOC) budgets depends on the balance of carbon (C) losses via respiration and C stabilization. Respiration increases monotonically with temperature, whereas the response of C stabilization to temperature is less clear. Microbial residues, formed via microbial growth, can get stabilized in soil and thus contribute to SOC accumulation. Here we test how the temperature dependence of the microbial SOC use for respiration (proxy for C losses) and growth (proxy for C stabilization) varies across climatic, edaphic, and substrate quality gradients, and how it responds to experimental warming. We hypothesized that the temperature dependence of microbial decomposition of organic matter is primarily governed by two factors: (i) the thermal traits of microbial communities, and (ii) SOC quality. To test these hypotheses, we collated more than 200 paired growth and respiration thermal response curves from over 20 published studies spanning a wide range of climates. Thermal traits of microbial communities (eg. minimal temperature, Tmin) were derived from microbial growth response curves, and temperature sensitivity was estimated as the ratio of microbial uptake rates at two reference temperatures offset by 10°C (Q10). Environmental temperatures at sampling sites were used as a proxy for climatic forcing, and C uptake per unit SOC (i.e., microbial assimilability) at a reference temperature as a proxy of SOC quality. Preliminary results indicate that warmer climates select for warm-shifted microbial thermal traits (i.e., higher Tmin values), and that temperature sensitivities are higher for lower-quality SOC. In addition, experimental warming alters microbial thermal responses in ways consistent with thermal adaptation. These findings allow us to describe the relative contributions of microbial thermal traits and of substrate quality in shaping the temperature dependence of SOC decomposition, thereby improving predictions of soil carbon fluxes under future climate scenarios.
How to cite: Guasconi, D., Chontos Blockström, K., Brangarí, A. C., Dumontel, H., Hicks, L., Siegenthaler, M., Varney, R., Rousk, J., and Manzoni, S.: The temperature dependence of the decomposition of soil organic matter is shaped by both microbial thermal traits and substrate quality, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20019, https://doi.org/10.5194/egusphere-egu26-20019, 2026.
Global warming increases the probability and frequency of droughts, with major consequences for soil carbon cycling. Soil microorganisms are particularly sensitive to drought because decreasing soil water content imposes osmotic stress and restricts the diffusion of substrates, enzymes, and metabolites. Previous studies have shown that drought reduced bacterial growth rates by more than half, whereas fungal and actinobacterial growth was comparatively resistant. However, in a future climate where droughts are projected to become more frequent, soils will be exposed to repeated drought events, and it remains unclear how drought history shapes microbial growth and carbon allocation during subsequent drought.
Here, we investigate how recurrent summer drought affects microbial growth, respiration, and storage compound synthesis in a unique long-term field experiment in an alpine grassland. Plots (n=4) have been exposed to 1, 3, 7, or 17 consecutive years of summer drought using rain-out shelters, with ambient plots as controls. We applied 2H-vapor-FAME-SIP (deuterium water-vapor stable isotope probing) to quantify microbial growth based on PLFAs (phospholipid fatty acids) and microbial carbon storage based on NLFA (neutral lipid fatty acid) and PHB (poly-3-hydroxybutyrate) production. Microbial respiration was determined by infrared gas analysis and microbial biomass by the chloroform-fumigation-extraction method.
Our results show that microbial respiration progressively declines with drought history. At peak drought, respiration was reduced by 44% after a single summer drought. This reduction intensified to 62%, 66%, and 75% after 3, 7, and 17 years of recurrent summer drought, respectively. This pattern indicates a strong drought legacy effect, consistent with the formation of ecological memory which increasingly constrains microbial activity. We will also present results from microbial growth and storage compound synthesis measurements and discuss how microbial carbon allocation patterns change with drought history.
By linking drought history to microbial growth, respiration, and storage compound synthesis, this study reveals how repeated drought alters carbon allocation of soil bacteria and fungi, with consequences for soil carbon persistence and carbon–climate feedbacks under global change.
This study is part of FWF COE7 “Microbiomes drive planetary health”.
How to cite: Rottensteiner, C., Waschulin, V., Woebken, D., Bahn, M., and Richter, A.: Recurrent drought imprints ecological memory on microbial carbon allocation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17390, https://doi.org/10.5194/egusphere-egu26-17390, 2026.
Although high-latitude soils are undergoing significant warming, with potential consequences for soil carbon (C) and nitrogen (N) cycling, the way in which warming duration modulates microbial physiological responses and associated changes in soil C and N pools is not well understood. Here, we used a natural geothermal gradient ranging from +0 to +12.3 °C to assess the effects of short-term (1 year), medium-term (5 to 9 years), and long-term (>50 years) soil warming on microbial biomass C, microbial physiology (mass-specific respiration and growth), carbon use efficiency (CUE), and soil C and N pools.
Across all warming durations, microbial biomass C and CUE decreased with increasing temperature. Warming consistently accelerated microbial metabolic rates, with mass-specific respiration increasing more than mass-specific growth, thereby explaining the observed reduction in CUE. Warming also reduced plant litter biomass while increasing its N concentration, suggesting accelerated litter decomposition under enhanced microbial activity. The magnitude of these physiological and functional responses was attenuated after nine years of warming, indicating a partial acclimation of microbial metabolism to sustained warming. While cumulative soil C and N losses were not yet detectable after one year of warming, they became evident after several years of exposure. This delayed emergence of C and N losses suggests that microbial communities gradually adjusted to the new thermal conditions, leading to partial acclimation once substrate availability had been substantially altered.
These results suggest that warming-induced changes in soil C and N dynamics are governed by the interaction between intrinsic microbial temperature sensitivity and progressive substrate depletion, as mediated by their effects on microbial biomass and physiology. Our findings improve the understanding of how microbial physiological responses shape soil C and N losses over time in a warming climate.
How to cite: Zevenhuizen Martínez, A. L., Richter, A., Yu, J., Verbrigghe, N., Janssens, I. A., Leblans, N., Sigurdsson, B. D., and Marañón-Jiménez, S.: From short- to long-term warming: microbial metabolic responses control soil carbon and nitrogen losses, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19325, https://doi.org/10.5194/egusphere-egu26-19325, 2026.
Permafrost forests harbor vast, climate-sensitive carbon (C) reservoirs whose vulnerability largely depends on temperature sensitivity of microbial respiration (Q10). However, substantial uncertainties persist in predicting Q10 patterns due to complex interactions among multiple ecological factors. Here, we conducted a standardized field survey with controlled incubations across a regional gradient from continuous permafrost (CP) and discontinuous permafrost (Dis-CP, including sporadic and isolated one) in the Greater Khingan Mountains to quantify Q10 values and identify their main ecological controls. We found that the Q10 values were significantly higher in CP than Dis-CP forests, indicating a stronger microbial respiratory response to warming in the coldest permafrost regions. Statistical analysis revealed that the soil microbiome was the most important factor explaining Q10 values in CP forest (47.8%), whereas a distinct set of factors (plant production, fine texture, substrate quality, and mean annual ground temperature) explained the largest proportion (63.2%) of Q10 variation in Dis-CP forests. Our findings suggest that warming-induced permafrost degradation is likely shift the dominant controls for Q10 from microbial community to abiotic and plant-related factors, while enhancing greenhouse gas emissions from permafrost soils.
How to cite: Huang, C. and Zhou, X.: Warming-induced carbon vulnerability in permafrost forests: a shift in Q10 from continuous to discontinuous zones, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9333, https://doi.org/10.5194/egusphere-egu26-9333, 2026.
Atmospheric methane (CH4) uptake in subarctic and Arctic mineral soils is significant for the CH4 budget of high-latitude regions, but its response to warming is not well understood. The effect of soil warming on net CH4 uptake was studied in situ across a natural warming gradient (ambient to + 57.5 °C) in a geothermal area in Southwest Iceland. The study site represented a subarctic grassland on mineral soil with field measurements conducted in summer and fall 2021. Combined automatic and manual dynamic chamber CH4 flux measurements across the warming transect showed that net CH4 uptake increased with 0.26 nmol CH4 m−2 s−1 per 1 °C of soil warming from ambient soil temperature up to about + 4 °C of soil warming. Soil warming above + 4 °C resulted in a gradual decrease of net CH4 uptake corresponding to 0.1 nmol CH4 m−2 s−1 per 1 °C of soil warming up to + 13 °C. With further soil warming, in situ net CH4 fluxes were probably affected by geogenic emissions during the effective study period. These trends of enhanced in situ net CH4 uptake with mild soil warming followed by a decreasing uptake rate with further warming were confirmed in a laboratory incubation experiment showing that the in situ response to temperature < + 13 °C was biogenic rather than geogenic. It is still not known whether the observed trends are due to adaptation of the community structure to temperature, differential regulation of activity or abundance. Our findings point to a window of future soil warming up to about + 4 °C where net CH4 uptake in subarctic grassland mineral soils is likely to increase, while further soil warming may result in a decrease of this important CH4 sink below ambient level. To expand the representativeness of these findings, we encourage future studies to include similar incubation experiments of the warming response for soils across the Arctic.
How to cite: Nielsen, A. S., Larsen, K. S., and Christiansen, J. R.: Taking the heat: soil warming optimum of CH4 uptake in subarctic mineral soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5381, https://doi.org/10.5194/egusphere-egu26-5381, 2026.
Global change-driven floods1 not only reshape or destroy landscapes but may also create hotspots for antimicrobial resistance. During a flooding event, contaminants and nutrients are mobilized, redistributed, and deposited across flooded areas2. While antimicrobial substances, i.e. metals and antibiotics, naturally occur in low concentrations in the environment, their levels often increase through anthropogenic activities3. These contaminants contribute to the unprecedented loss in soil health affecting the soils’ microbiome and its ecosystem functions3. As a microbial adaptation, metal (MRGs) and antibiotic resistance genes (ARGs) proliferate in the environment. Microbial resistance may enhance soil resilience, yet the spread and proliferation of ARGs poses a major public health threat, contributing to the failure of medical treatments and millions of deaths annually6. ARGs and MRGs are often co-located on the same mobile genetic elements, and are thus co-proliferated together even in the absence of one of the contaminants7. By entering rivers through runoff, leaching and discharge8 contaminants can be transferred downstream and accumulate in flood-prone areas. Thus, riverine floodplains may likely be co-exposed to metals and antibiotics and function as reservoirs for resistance genes, potentially facilitating their transfer to humans.
To evaluate how resistance acquisition evolves after flooding, a mesocosm study with combined and single metal and antibiotic contamination of a floodplain grassland from the Elbe river was conducted. Environmentally relevant concentrations of metals, antibiotics, their combination, or uncontaminated water were applied in a single flooding event. Contaminant fate in porewater and microbial resistance in soil were traced over seven weeks.
The added metal load was not detectable in the mobile phase of soil porewater one day after flooding, indicating adsorption to soil particles. Nevertheless, plants responded with a contaminant-dependent increase in the chlorophyll a/b ratio within two weeks after flooding. In addition, flooding induced microbial cell growth, with the magnitude and timing of growth peaks depending on the contamination treatment. The metal treatment induced a rapid increase in 16S rRNA gene copies as well as a slight increase of MRGs after two weeks, whereas antibiotics and the combined treatment resulted in a delayed response followed by a slower decrease in both gene abundances. Metals and antibiotics combined did not amplify but rather attenuated this microbial response. Subsequently, ARGs were correlated with MRG responses. Overall, even though the microbial community responded to the stressors, the magnitude and duration of effects indicate that the active and diverse community of floodplain soils could be able to buffer low contamination events.
Increasing frequency of extreme weather events and ongoing contaminant accumulation can further challenge the resilience of microbial communities in flood-impacted soils, highlighting their role as flood protection and water filters but also their vulnerability.
1 IPCC, 2023
2 Crawford et al., J Hazard Mater, 2022
3 Cycoń et al., Front Microbiol, 2019
4 Lado et al., Geoderma, 2008
5 IPBES, 2018
6 Naghavi et al., Lancet, 2024
7 Imran et al., Chemosphere, 2019
8 Bailey et al., J Soils Sediments, 2015
How to cite: Breit, M., Buob, D., Scholz, M., Worrich, A., and Muehe, E. M.: Does flooding proliferate metal and antibiotic resistance genes in riverine floodplains?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13033, https://doi.org/10.5194/egusphere-egu26-13033, 2026.
Peatland methanotrophs mitigate greenhouse gas emissions through oxidizing methane in shallow peat layers forming a filter that removes methane during diffusive transported towards the peat surface. Beside methanotrophs abundance, the effectiveness of this filter also depends on their affinity towards methane and oxygen, which might be affected by climate-driven changes in hydrology as wel as land management practices like drainage and restoration.
Here, we quantified the long-term effects of water-table depth (WTD) and WTD manipulation on the methanotroph affinity towards methane and oxygen. Samples were collected at the Lakkasuo peatland in central Finland. Within this site, we collected samples (10-20cm depth) from four sites along a hydrological gradient formed by long-running experiments (73 years drainage for forestry, 23 years experimental water table drawdown, undrained control) and natural in-site WTD variation (undrained lower water table). We quantified affinities (kM) and specific activities (a=vmax/kM) towards methane and oxygen in laboratory incubations with 50-50 000 ppm methane and 3-21% oxygen. At the same time, we surveyed the of the methanotroph communities at these sites through quantitative PCR of mmoX and pmoA subtypes as well as targeted metagenomics of the same genes.
Methane affinity increased from control (kM = 842 ppm, 90% central posterior distribution 702-1005ppm) to forestry drained (kM = 379 (268-506) ppm) and the low water table controls (527 (434-633) ppm), but decreased in response to experimental water table drawdown (1251 (988-1557) ppm). This indicates the establishment of relatively high affinity methanotrophs in foresty drained peat and under naturally lower WTD, but not in response to experimental water table drawdown. Substrate saturation toward oxygen was evident over 5-10% oxygen, but the precision was insufficient to identify differences along the gradient. Methanotroph composition showed a shift from pmoA II dominance at the control and undrained lower water table sites to pmoA Ia dominance in experimental water table drawdown and drainage for forestry.
Our results demonstrate that significant changes in methanotroph kinetics occur in response to WTD manipulations which may need to be considered in peatland methane models. Parameters derived from pristine peatlands may not be accurate immediately after rewetting when methanotroph communities are still adapted to low methane and high oxygen concentrations.
How to cite: Kohl, L., Acharige, N. T. G., Ranasinghe, S., Ramezanalaghehband, M., King, M., Palacin, C., Paul, D., Putkinen, A., Siljanen, H., and Tuittila, E.-S.: Decadal adaptation of methanotroph affinity to peatland water table manipulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14788, https://doi.org/10.5194/egusphere-egu26-14788, 2026.
Wetlands, as the largest natural source of methane (CH₄) emissions, have received increasing attention in climate modelling. Recognising that methanogenesis is governed by anaerobic microbial processes, some models explicitly represent methanogen activity to simulate CH₄ emissions from permanently inundated wetlands. In such models, CH₄ emissions from seasonally flooded wetlands are usually estimated using an empirical oxidation factor to represent methanotrophic consumption. However, this approach neglects an additional important effect of atmospheric oxygen ingress during hydrological drawdown: the stimulation of organic matter decomposition upon rewetting, analogous to the Birch effect in seasonally dry ecosystems.
Despite the high annual methane emissions from permanently inundated sites, some of the highest intensity CH₄ emission spikes throughout the year are exhibited by seasonally inundated systems, such as freshwater marshes, floodplain wetlands and fens. Consequently, improved mechanistic representation of biogeochemical processes in seasonally inundated wetlands is needed to robustly assess global wetland greenhouse gas contribution.
This study presents a process-based wetland biogeochemical model that explicitly represents oxygen-stimulated substrate dynamics and microbial functional differentiation. Dissolved organic carbon (DOC) is partitioned into a “dry DOC” pool that accumulates during dry periods, and a “wet DOC” pool that is replenished upon rewetting. Microbial processes include distinct aerobic and anaerobic pools, whose activities are regulated by soil water content (SWC). Aerobic microbial activity follows a Gaussian response to SWC, reflecting optimal activity under intermediate moisture conditions. Water table depth (WTD), a relatively commonly measured wetland metric, is used to infer vertical SWC profiles in the soil column through a fitted van Genuchten soil water retention curve.
The microbial-DOC framework is coupled with the Joint UK Land Environment Simulator (JULES), a community land-surface model simulating the exchanges of energy, water and carbon between the land surface and the atmosphere, which can also be used as the land surface scheme of the UK Earth System Model (UKESM). JULES drives the microbial-DOC module by providing partitioned pools of litter, soil organic carbon, and root exudates, each characterised by distinct turnover kinetics. Temperature sensitivity is represented using Arrhenius kinetics, while substrate and microbial limitations are described using Michaelis–Menten formulations. Model parameters are constrained using methane and carbon dioxide flux measurements, alongside methanogen abundance data, from flooded hardwood and palm forests in Panama.
Resolving oxygen-mediated substrate priming and microbial responses, the framework moves beyond oxidation-only representations and improves estimates of wetland carbon source–sink dynamics under climate change.
How to cite: Liu, Y., Sjogersten, S., Burke, E., Allingham, S., Chadburn, S., Bernard, J., Gallego-Sala, A., Duran-Rojas, C., and Betts, R.: Mechanistic Modelling of Wetland Methane Dynamics in the JULES Land Surface Model: Representing Redox-Driven Substrate Dynamics and Microbial Switching, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14751, https://doi.org/10.5194/egusphere-egu26-14751, 2026.
Karst tiankengs are established hotspots of biodiversity for macro-organisms. In contrast, the soil micro-food web, structured around microbes, protozoa, and nematodes, represents a critical yet understudied component of subsurface ecosystem diversity and functioning. Its patterns of diversity and underlying maintenance mechanisms remain largely unresolved. To address this, we conducted a three-year bidirectional soil translocation experiment between the interior and exterior of a tiankeng, assessing responses of the soil micro-food web and soil multifunctionality to these distinct habitats. We found that soil translocation significantly altered the diversity, composition, and structure of the micro-food web, with variation in responses across different trophic levels. These shifts were primarily driven by the contrasting environmental regimes, including temperature, humidity, and soil resource availability, between the tiankeng interior and the external environment. Specifically, outward translocation negatively impacted key attributes of the micro-food web. Enhanced competitive interactions between bacteria and fungi exerted bottom-up control, restructuring the entire network. Notably, the tiankeng interior sustained a more complex and stable soil micro-food web, supported higher levels of soil multifunctionality, and demonstrated that micro-food web complexity is pivotal in regulating multifunctionality. Our findings underscore the potential of tiankengs to act as climate refugia and biodiversity reservoirs under future climate change scenarios. Moreover, tiankengs can serve as natural open‑top laboratory models, offering a novel and powerful perspective for simulating the responses of subsurface ecosystems to climate change.
How to cite: Jiang, C., Qiu, C., Zhou, C., and Shui, W.: Response of soil micro-food webs to climate change in karst ecosystems: A soil translocation experiment based on tiankeng, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4768, https://doi.org/10.5194/egusphere-egu26-4768, 2026.
Boreal forests are significant net carbon sinks and play an essential role in the global carbon cycle. However, such forests are often subject to management practices such as clear-cutting. After clear-cutting, most root-associated mycorrhizal fungi die along with their tree hosts, opening a niche for saprotrophic microorganisms, including soil bacteria. With the competition eliminated, soil bacterial activity is expected to increase. Conversely, as forests regrow, mycorrhizal fungi suppress soil saprotrophs, potentially decreasing soil organic matter decomposition.
In this study, we utilized two parallel chronosequences in Sweden, each consisting of 18 stands that varied in time since disturbance, representing forest rotational management and a natural reference, a wildfire chronosequence. In each forest stand, we trenched plots and removed vegetation to exclude mycorrhizal fungi. We then measured bacterial growth in soil samples across the chronosequences. We hypothesized that (1) bacterial growth would increase after clear-cutting and forest fire, then decrease as forests regrow due to suppression by mycorrhizal fungi; and (2) bacterial growth would be higher in trenched plots than in non-trenched plots at each forest stand due to the elimination of competition with mycorrhizal fungi.
Contrary to both hypotheses, bacterial growth was lowest following forest clear-cutting and wildfire. With forest regrowth, bacterial growth increased. Interestingly, following clear-cutting, bacterial growth peaked when forest productivity was highest (40–70 years post-clear-cutting). Trenching also decreased bacterial growth along both the rotational forest management and wildfire chronosequences. These unexpected results suggest that bacterial communities are negatively affected by plant removal, likely due to their strong dependence on readily available carbon from root exudates.
How to cite: Tajmel, D. and Gundale, M.: The role of bacteria in soil carbon dynamics of managed boreal forests, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18789, https://doi.org/10.5194/egusphere-egu26-18789, 2026.
The Anthropocene exerts various pressures and influences on the stability and function of the Earth’s ecosystems. However, our understanding of how the microbiome responds in form and function to these disturbances is still limited, particularly when considering the phyllosphere, which represents one of the largest microbial reservoirs in the terrestrial ecosystem. In this study, we comprehensively characterized tree phyllosphere bacteria and associated nutrient-cycling genes in natural, rural, suburban, and urban habitats in China. Results revealed that phyllosphere bacterial community diversity, richness, stability, and composition heterogeneity were greatest at the most disturbed sites. Stochastic processes primarily governed the assembly of phyllosphere bacterial communities, although the role of deterministic processes (environmental selection) in shaping these communities gradually increased as we moved from rural to urban sites. Our findings also suggest that human disturbance is associated with the reduced influence of drift as increasingly layered environmental filters deterministically constrain phyllosphere bacterial communities. The intensification of human activity was mirrored in changes in functional gene expression within the phyllosphere microbiome, resulting in enhanced gene abundance, diversity, and compositional variation in highly human-driven disturbed environments. Furthermore, we found that while the relative proportion of core microbial taxa decreased in disturbed habitats, a core set of microbial taxa shaped the distributional characteristics of both microbiomes and functional genes at all levels of disturbance. In sum, this study offers valuable insights into how anthropogenic disturbance may influence phyllosphere microbial dynamics and improves our understanding of the intricate relationship between environmental stressors, microbial communities, and plant function within the Anthropocene
How to cite: Li, J.: From nature to urbanity: exploring phyllosphere microbiome and functional gene responses to the Anthropocene, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4370, https://doi.org/10.5194/egusphere-egu26-4370, 2026.
