EXtreme weather events and soil greenhouse gas fluxes in Austrian FORests. Evaluating the feedbacks under global change

Temperate forest ecosystems are naturally exposed to extreme weather events such as drought periods and heavy precipitation episodes. Due to climate change, the frequency and the intensity of extreme events is already increasing. Forest soils are responsible for the exchange of large amounts of GHG with the atmosphere and thus influence strongly the climate system. However, the overall feedback effect between extreme events and soil GHG fluxes is still unknown and challenging to address. Changes in climate induce a soil response, but its direction, magnitude and duration are probably dependent on soil conditions, whereby nitrogen (N) availability for soil microorganisms exert a strong influence on the microbial response upon environmental changes. In this project, we will simulate extreme weather events (provoking soil drying-wetting cycles) and enhanced inputs of reactive N in three experimental forest sites within a natural nitrogen deposition gradient. The three sites are equipped with state-of-the-art research infrastructure and are part of several long-term ecosystem research networks (e.g. LTER Europe, LTER Austria, LTER-CWN). We will investigate the response of the soil-atmosphere GHG exchange (carbon dioxide, CO2; methane, CH4; and nitrous oxide, N2O) with hourly resolution field automated chambers involving stable isotopes approaches for identifying distinct microbial N2O production pathways in soil. Soil nutrient cycling and the soil microbial communities will be investigated with cutting-edge methods, including quantitative and qualitative estimations of soil methanotrophic communities. Results from the field campaigns will feed and improve process-based models, allowing us to estimate the GHG balance of selected Austrian sites standardized climate scenarios. Overall, we expect to critically increase our understanding on the relationships between precipitation patterns, nitrogen availability and soil biogeochemical processes, as a requisite to get better and informed predictions on the impacts of climate change and extreme events on ecosystems and ecosystem services.