CO2, CH4 and N2O fluxes in an alpine meadow on the Tibetan Plateau as affected by N-addition and grazing exclusion

Abstract

Abstract Limited understanding of the effects of enhanced nitrogen (N) addition and grazing exclusion (E) on greenhouse gases fluxes (GHGs: CO 2 , CH 4 , and N 2 O) in grasslands constrains our ability to respond to the challenges of future climate change. In this study, we conducted a field experiment using a static closed opaque chamber to investigate the response of GHG fluxes to N addition (69 kg N ha −1 year −1 applied in 3 splits) and grazing exclusion in an alpine meadow on the Tibetan Plateau during the growing seasons from 2011 to 2013. Our results showed that winter grazing significantly raised soil temperature (ST), while grazing exclusion (E) had no effect on soil moisture (SM), and N fertilizer (F) had no effect on ST or SM. Aboveground biomass (AB) and root biomass (RB) were not significantly affected by E in 2011-2013 ( p > 0.05), but F significantly affected AB and RB ( p < 0.05). Compared with winter grazing, only E substantially reduced seasonal mean CO 2 emissions (by about 20.1%) during the experimental period. E did not significantly directly affect CH 4 uptake, whereas N addition reduced seasonal mean CH 4 uptake by about 6.5%, and N addition changed seasonal average absorption of N 2 O into an emission source. CO 2 flux is the major contributor to CO 2 equivalent emissions in this area. Our results indicate that exclosure from livestock grazing might be a promising measure to reduce CO 2 emissions, while enhanced N addition might reduce CH 4 uptake and increase N 2 O emission in the alpine meadow under future climate change.