Department: Department of Earth Sciences
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Faculty of Biology, Chemistry and Earth Sciences
Faculty of Biology, Chemistry and Earth Sciences at the University of Bayreuth
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Bayreuth, Germany
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Department of Earth Sciences at the University of Bayreuth
Fachgruppe Geowissenschaften an der Universität Bayreuth
Fachgruppe Geowissenschaften an der Universität Bayreuth
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Research Data Open Access Data from: Greenhouse gas fluxes from two drained pond sediments: a mesocosm study(2025-02-14) Borken, WernerPonds can store large amounts of organic matter (OM) in their sediments, often accumulated over long periods of time. Sediment OM is largely protected from aerobic mineralization under water saturated conditions but are vulnerable when exposed to oxygen during periods of drought. As climate change progresses, drought periods are likely to occur more frequently and may affect OM mineralization, and thus the release of greenhouse gases (GHGs) such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from pond ecosystems. Therefore, we aimed to test how GHG emissions and concentrations in the sediment respond to drought by gradually decreasing water levels to below the sediment surface. To this end, undisturbed sediment cores from two small ponds with distinct watershed and water chemistry characteristics were incubated in mesocosms for 118 days at 20°C. Water levels were sequentially tested at 3 cm above the sediment surface (Phase I) and at the level of the sediment surface (Phase II). In Phase III, water levels were continuously lowered either by evaporation or by active drainage including evaporation. Mean CH4 fluxes of both ponds were high (21 and 87 mmol m-2 d-1), contributing 90 and 96% to the GHG budget over the three phases. The highest CH4 fluxes occurred in Phase II, while active drainage strongly reduced CH4 fluxes in Phase III. A multivariate analysis suggests that dissolved organic carbon and sulphate were important drivers of CH4 fluxes in Phase III. CO2 and N2O fluxes also responded to declining water levels, but their contribution to the GHG budget was rather small. Both gases were primarily produced in the upper sediment layer as indicated by highest concentrations at 5 cm sediment depth. Compaction of sediment cores by water level lowering increased bulk density and maintained high water contents. This side effect, retarding the drying of the sediment surface, was possibly relevant for the GHG net emission of the sediments in Phase II and III. Overall, GHG fluxes from the sediments exhibited high sensitivity to falling water levels. This study suggests that drying pond sediments have great potential to emit large amounts of GHGs to the atmosphere in the event of drought, representing hot spots of GHGs in the landscape.Research Data Open Access Relative and absolute abundances of bacteria and fungi in soil at the Achenkirch soil warming experiment(2026-01-09) Borken, WernerLong-term soil warming may alter microbial community structure and functioning in forest soils, thereby affecting carbon and nutrient cycling processes. We examined the effects of >14 years of soil warming (+4°C during snow-free seasons) on the fungal biomass marker ergosterol, and on fungal and bacterial communities in a spruce dominated mountain forest in the Austrian Alps. Soil warming decreased ergosterol, and the ergosterol-to-microbial biomass carbon (MBC) ratio at 0-10 and 10-20 cm soil depth, with a stronger decline in ergosterol, indicating a higher sensitivity of fungi than bacteria to long-term warming. Warming also shifted the fungal community at both soil depths, favoring Boletus luridus, an ectomycorrhizal (ECM) fungus, which emerged as the dominant OTU in warmed plots. Its abundance was positively associated with fine root biomass, root tip density, and soil respiration in warmed plots but negatively with ergosterol and MBC in control plots at 0ï€10 cm depth. The dominance of ECM over saprotrophic fungi (SAP) under warming at topsoil likely resulted from increased fine root production and enhanced competition for substrates and nutrients. Bacterial abundance and community composition remained mostly unaffected at both depths, likely due to their greater resilience to elevated temperatures and their high taxonomic diversity. Our findings therefore suggest that long-term warming primarily affects fungal community composition and functional traits, thereby enhancing the contribution of ECM with fine roots to the carbon cycle in the calcareous forest soil.Research Data Open Access Data for "Fresh and degraded maize shoot and root residues temporarily change soil hydraulic properties"(2026-03-18) Leuther, FredericIn a laboratory study, we quantified the effect of maize crop residues (CR) in various concentrations (0, 2, and 5 wt.%) on the SHP of a loam soil and additionally measured the SHP of a mulch layer (100 wt.% CR) from saturation to oven dryness. We differentiated between shoot and root CR to quantify the effect of biomass quality and adapted the simplified evaporation method to measure the hydraulic properties of 100% CR layer. The experiments were run in triplicate and repeated after three weeks of incubation under optimal conditions for biological activity (30 °C, 90% RH) to simulate organic matter degradation after harvest. This dataset contains soil hydraulic measurements taken pre and post-incubation.