Long-term effects of drought and rewetting manipulations on the greenhouse gas balance of a temperate forest soil.

Climate change is increasing the frequency and intensity of extreme weather events such as drought and episodic heavy rainfall events in large areas of the world, including Central Europe. These disturbances affect fundamental biogeochemical processes and alter greenhouse gas fluxes in forest soils. In this framework, we operate an in-situ lab to investigate long-term effects on forest soils due to altered precipitation patterns. At Lehrforst Rosalia, an eLTER site, we have been performing active manipulations since 2013, involving different frequencies and intensities of drought and rewetting cycles. Since 2020, we have expanded the experiment to include increased atmospheric N-deposition. Soil greenhouse gas fluxes (CO 2 , CH 4 , N 2 O) are measured at high temporal resolution, together with soil moisture and temperature. Furthermore, periodic soil sampling campaigns are conducted to explore dynamics of soil chemical and microbiological properties. Our long-term data shows that increased frequency and intensity of drought and rewetting results in a reduction of soil respiration rates together with an increase in soil CH 4 uptake. This pattern is associated with both altered water dynamics and changes in soil microbial communities. Overall, our results clearly show that the effects of drought dominate the effects of rewetting. The data we generate at Lehrforst Rosalia are critical for understanding how ecosystems react to environmental stressors and feed process-based models to develop further scenarios.