Effects of whole-soil warming on CH4 and N2O fluxes in an alpine grassland

Abstract

Global climate warming could affect the methane (CH4) and nitrous oxide (N2O) fluxes between soils and the atmosphere, but how CH4 and N2O fluxes respond to whole-soil warming is unclear. Here, we for the first time investigated the effects of whole-soil warming on CH4 and N2O fluxes in an alpine grassland ecosystem on the Tibetan Plateau, and also studied the effects of experimental warming on CH4 and N2O fluxes across terrestrial ecosystems through a global-scale meta-analysis. The whole-soil warming (0–100 cm, +4°C) significantly elevated soil N2O emission by 101%, but had a minor effect on soil CH4 uptake. However, the meta-analysis revealed that experimental warming did not significantly alter CH4 and N2O fluxes, and it may be that most field warming experiments could only heat the surface soils. Moreover, the warming-induced higher plant litter and available N in soils may be the main reason for the higher N2O emission under whole-soil warming in the alpine grassland. We need to pay more attention to the long-term response of greenhouse gases (including CH4 and N2O fluxes) from different soil depths to whole-soil warming over year-round, which could help us more accurately assess and predict the ecosystem-climate feedback under realistic warming scenarios in the future.