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Climate change scenarios predict more frequent and intense drought periods for 2071 to 2100 for many regions of the world including Austria. Current and predicted lower precipitation scenarios were simulated at a lysimeter station containing a fertile and less fertile agricultural soil for 9 years. 13C and 15N-labeled green manure was added in year 8 with the aim to analyze how the predicted precipitation regime affects soil fauna and microbial groups and consequently nitrogen (N) and carbon (C) cycling. Among the investigated mesofauna (collembola and oribatida), the abundance and biodiversity of oribatida was significantly reduced by drought, possibly because they mainly represent K-strategist species with low mobility and consequently the need to adapt to long-term adverse environmental conditions. Microbial community composition and microbial biomass, investigated by phospholipid fatty acid (PLFA) analysis, was indistinguishable between the current and the predicted precipitation scenarios. Nonetheless, soil 13C-CO2 emissions and soil water 15N-NO3 data revealed decelerated mineralization of green manure under reduced precipitation in the first 2 weeks, but no effects were observed on soil C sequestration or on 13C incorporation into microbial PLFAs in the following 1.2 years. We found that over a 1-year time period, decomposition was rather driven by plant residue availability than water limitation of microorganisms in the investigated agroecosystem. In contrast, N2O emissions were significantly reduced under drought, and green manure derived 15N accumulated in the soil under drought, which might necessitate the adjustment of future fertilization regimes. The impacts of reduced precipitation and drought were less pronounced in the more fertile agricultural soil, due to its greater buffering capacity in terms of water storage and organic matter and nutrient availability. [ABSTRACT FROM AUTHOR]

Climate change affects precipitation patterns in the future, and as such is a determining factor in agricultural systems in terms of soil organic matter mineralization, nutrient release and therefore plant production. This study investigates the impact of precipitation on two different soil types – a sandy calcaric phaeozem (S) and a calcic chernozem (T) representative of the Pannonian area of the Marchfeld region in Austria. A regionalized scenario RCP 6.0 derived from the 5th IPCC was used on a long-term lysimeter study in the Marchfeld, where future rainfall patterns were compared with current precipitation since 2011. Simple concentration measurements did not show clear differences in carbon and nutrient cycling between scenarios as heterogeneity between lysimeters was high. However, a more precise way of tracing carbon and nitrogen turnover in soils is using a stable isotope labelling approach. In this study, green manure (Sinapis alba) labelled with 13C and 15N stable isotopes was applied to the lysimeter soil in April 2018. Gaseous emissions, soil, plant and groundwater samples were collected at different time points throughout the growing season and analysed using isotope ratio mass spectrometry. Results showed decreased plant biomass production in the future scenario due to drought stress as indicated by increased δ13C values of the plants. Mineralization of green manure and label uptake into soil microorganisms was shown to start within hours of application. As expected, concentration measurements did not reveal differences between current and future scenarios. However, isotope results showed that inorganic N (NO3-) was released from the green manure more slowly under the future scenario in the initial days but its proportion in crops increased during summer, emphasizing the importance of plant biomass production on NO3- uptake from soil. This study provides a nice example how isotope tools can uncover differences in soil processes which are otherwise masked due to soil heterogeneity. [ABSTRACT FROM AUTHOR]

Climate change is likely to affect precipitation patterns in the future, and as such is a determining factor in agricultural systems in terms of soil organic matter mineralization, nutrient release and therefore plant production. This study investigates the impact of precipitation on two different soil types – a sandy calcaric phaeozem (S) and a calcic chernozem (T) – representative of the Pannonian area of the Marchfeld region in Austria. A regionalized scenario RCP 6.0 derived from the 5th IPCC was used on a long-term lysimeter study in the Marchfeld, where future rainfall patterns were compared with current precipitation since 2011. In this study, green manure (Sinapis alba) labelled with 13C and 15N stable isotopes was applied to the lysimeter soil in April 2018. Mineralization of green manure and release of inorganic bioavailable 15N NO3 was confirmed after soil sampling at different time points throughout the growing season and elemental analyser – isotope ratio mass spectrometer (EA-IRMS) measurements. In addition to soil, plant and groundwater sampling, 15N N2O and 13C CO2 measurements were conducted by using a cavity ring down spectrometer (CRDS) installed in the field and gas chromatography – isotope ratio mass spectrometry (GC-IRMS) respectively. Results showed initially low emissions of N2O (0.01 – 0.02 µg N2O m-2 h-1) after addition of green manure. In the second week N2O emission were higher under the current precipitation scenario. Incorporation of 15N label from the green manure into N2O was not observed. A simulated heavy rainfall event (60 mm) increased N2O emissions within a few hours with up to ten fold higher emissions in the future scenario, still no incorporation of label was observed. Highest N2O emissions especially in the current scenario was observed after commercial fertilizer (50 kg/ha) was added. Source signatures of CO2 according to the Keeling plots showed an immediate uptake (~hours) of the labelled manure. Differences in the green manure mineralization rate was identified for the soil types (S faster than T) but not for the future precipitation regime. However, total CO2 emission (40 – 250 mgC m-2 h-1) from the calcic chernozem (T) were less for the future scenario. This study suggests that soil CO2 emissions will become lower in these future precipitation scenarios. It also demonstrated the relevance of green manure as a fertilization strategy to avoid N2O emissions. [ABSTRACT FROM AUTHOR]