Effects of water table level and nitrogen deposition on methane and nitrous oxide emissions in an alpine peatland

[摘要] Alpine peatlands are recognized as a major natural contributor to thebudgets of atmospheric methane ( CH 4 ) but as a weak nitrous oxide( N 2 O ) source. Anthropogenic activities and climate change have putthese fragile nitrogen (N)-limited peatlands under pressure by alteringwater table (WT) levels and enhancing N deposition. The response ofgreenhouse gas (GHG) emissions from these peatlands to these changes isuncertain. To address this knowledge gap, we conducted a mesocosm experimentin 2018 and 2019 investigating individual and interactive effects of threeWT levels (WT −30 , 30 cm below soil surface; WT 0 , 0 cm at the soilsurface; WT 10 , 10 cm above soil surface) and multiple levels of Ndeposition (0, 20, 40, 80 and 160  kg N ha - 1 yr - 1 ) on growingseason CH 4 and N 2 O emissions in the Zoige alpine peatland,Qinghai–Tibetan Plateau. We found that the elevated WT levels increased CH 4 emissions, while N deposition had nonlinear effects (withstimulation at moderate levels but inhibition at higher levels). Incontrast no clear pattern of the effect of WT levels on the cumulative N 2 O emissions was evident, while N deposition led to a consistent andlinear increase (emission factor: 2.3 %–2.8 %), and this was dependenton the WT levels. Given the current N deposition in the Zoige alpinepeatland (1.08–17.81  kg N ha −1 ), our results suggested thatthe CH 4 and N 2 O emissions from the alpine peatlands could greatlyincrease in response to the possible doubling N deposition in the future. Webelieve that our results provide insights into how interactions betweenclimate change and human disturbance will alter CH 4 and N 2 O emissions from this globally important habitat.

[学科分类] 大气科学