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

Abstract

Summary Montane grasslands of Central Europe 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 (CH4) and nitrous oxide (N2O) as well as on ammonium (NH4+) and nitrate (NO3−) in soil water in extensively managed montane grassland in southern Germany. 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 CH4 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 NH4+ and NO3− concentrations in soil water (0.05 mg NH4+–N l−1 and 0.08 mg NO3−–N l−1) and N2O 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‐CO2 greenhouse gas balance in extensively managed montane grassland because of increased net CH4 uptake in soil. For N2O emission, we conclude that potential effects of management changes may override the small effects of simulated climate change on N2O emissions observed in this study.

Greenhouse gas fluxes over managed grasslands in Central Europe

“…Elevated N 2 O fluxes at low TS were probably the consequence of emission bursts during freeze/thaw cycles (Risk, Snider, & Wagner-Riddle, 2013). For CH 4 , reduced percentile fluxes at high TS in combination with relatively low WFPS both across all grassland sites ( Figure 5b) and at the site-level (e.g., DE-FEN-E, Figure 4) are in contrast to findings for wetlands, rice paddies, and aquatic ecosystems (Yvon-Durocher et al, 2014), but similar to findings for montane grasslands (Unteregelsbacher et al, 2013). The strong correlation between CH 4 fluxes and WFPS is supported by previous studies (Hofmann, Farbmacher, & Illmer, 2016;Le Mer & Roger, 2001;Wang, Zhang, Huang, Li, & Zhang, 2015).…”

Disentangling gross N2O production and consumption in soil

“…The montane grassland is manured 2–3 times a year and cut for hay three times a year19. The cropland is a conventional corn-winter wheat rotation.…”

Contribution of litter layer to soil greenhouse gas emissions in a temperate beech forest

“…Concentration changes over time were determined with quadratic best-fit equations for CO 2 and N 2 O, and an exponential best-fit equation for CH 4 . Greenhouse gas fluxes were discharged if regression coefficients (r 2 ) were below 0.70 for CH 4 and N 2 O, and below 0.90 for CO 2 (Barton et al 2008;Chadwick et al 2014;Unteregelsbacher et al 2013). Positive fluxes represent net GHG emissions, negative fluxes represent net GHG uptake.…”