The Characteristics and Seasonal Variation of Methane Fluxes From an Alpine Wetland in the Qinghai Lake watershed, China

Abstract

Alpine wetlands are an important natural source of methane (CH4) to the atmosphere. However, the temporal variations and main driving factors of CH4 fluxes in alpine wetlands are not yet well understood. In this study, CH4 fluxes were measured from an alpine wetland in the Qinghai Lake using eddy covariance (EC) technique. Strong seasonal variability in the daily CH4 fluxes was observed, ranging from − 18.24 mg CH4 m− 2 d− 1 during the non-growing season to 117.44 mg CH4 m− 2 d− 1 during the growing season in 2017. The annual CH4 budget was 9.41 g CH4 m− 2. The growing season CH4 flux accounted for 91.5 % of the annual budget. At the daily scale, the CH4 fluxes increased significantly as the net radiation, air temperature, vapor pressure deficit, soil temperature, and soil volumetric water content at 5 cm depth increased. Additionally, correlation analysis also revealed that daily CH4 flux was significantly related to CO2 flux when daily CO2 flux was negative, but there was no correlation when daily CO2 flux was positive. Path analysis showed that seasonal variations of soil temperature at 5 cm depth and CO2 flux had strong direct effects on daily CH4 fluxes.