High-resolution dynamics of available N in a grassland ecosystem under a multiple climate manipulation experiment

Nitrogen (N) is the most important limiting nutrient for plants and soil microorganisms in almost all ecosystems. Global environmental changes significantly affect the terrestrial N cycle but implications for plant available N in-situ remain unclear. Here, we investigated the simultaneous effect of elevated atmospheric CO2, an increase in temperature and a drying-rewetting event on diffusive N fluxes in soil of a managed permanent grassland at the multifactor climate manipulation experimental site ClimGrass (Austria) using microdialysis. Rewetting caused a significant, but short-lived increase in diffusive NH4+ and NO3- fluxes, which subsequently dropped until the end of the experiment. Harvesting induced a significant increase in diffusive NH4+ fluxes in the drying-rewetting treatments. However, elevated CO2 and soil warming had little effect on diffusive N fluxes. Our study suggests that more frequent soil drying-rewetting cycles associated with increased extreme weather events are uppermost among the climate change drivers affecting soil N availability.