Effects of Increased Precipitation and Nitrogen Deposition on Methane Uptake of Alpine Meadow in Qinghai-Tibet Plateau: in situ Experiments

ABSTRACT The methane (CH4) fluxes in grasslands are sensitive to changes in precipitation and soil nitrogen concentrations, which was poorly understood, especially on the Tibetan Plateau. Therefore, an experiment was conducted from May 2012 to October 2013, by using the static chamber technique and gas chromatography method. We set up five treatments: an increased 2 g m-2 NH4NO3 treatment (2gN); an increased 4 g m-2 NH4NO3 treatment (4gN); and treatment with precipitation increased by 20% (Pre), and added 2 g m-2 NH4NO3 and precipitation (20%) treatment (N+Pre), and a control treatment (CK). The five treatments showed decreasing CH4 uptake rates in the following order: CK (71.66 ± 6.6 µg m-2 h-1) > N+Pre (58.57 ± 3.7 µg m-2 h-1) > Pre (52.66 ± 2.3 µg m-2 h-1) > 2gN (47.63 ± 3.1 µg m-2 h-1) > 4gN (39.12 ± 3.3 µg m-2 h-1). The 2gN and 4gN treatment resulted in 33.5% and 45.4% lower CH4 uptake than the CK treatment, respectively. The path analysis indicated that the above-ground biomass and litter fall were the most important factor promoting and limiting the CH4 uptake rate of alpine meadow, respectively.