Increased methane uptake but unchanged nitrous oxide flux in montane grasslands under simulated climate change conditions

Summary Montane grasslands of C entral E urope are expected to be exposed to strong warming and to altered precipitation patterns, suggesting that biosphere–atmosphere–hydrosphere exchange of carbon ( C ) and nitrogen ( N ) compounds may be vulnerable to future climatic conditions. By transferring small lysimeters along an altitudinal gradient, we assessed the impact of climate change conditions on soil–atmosphere exchange of methane ( CH 4 ) and nitrous oxide ( N 2 O ) as well as on ammonium ( NH 4 + ) and nitrate ( NO 3 − ) in soil water in extensively managed montane grassland in southern G ermany. Lysimeter transfer to lower altitude increased air and soil temperatures by more than 2°C and reduced summer precipitation as well as soil moisture throughout the year compared with a control transfer within the high altitude site. This simulation of climate change conditions almost doubled the CH 4 sink strength from −0.11 to −0.19 g C m −2  year −1 , which appeared to be mainly related to improved gas diffusion after reduced soil moisture. Mean NH 4 + and NO 3 − concentrations in soil water (0.05 mg NH 4 + –N  l −1 and 0.08 mg NO 3 − –N  l −1 ) and N 2 O emissions (approximately 0.03 g N m −2  year −1 ) remained small and unaffected by climate change simulation. Our study suggests that expected climate change conditions will have positive effects on the non‐ CO 2 greenhouse gas balance in extensively managed montane grassland because of increased net CH 4 uptake in soil. For N 2 O emission, we conclude that potential effects of management changes may override the small effects of simulated climate change on N 2 O emissions observed in this study.