Effects of short-term warming and nitrogen addition on CO_2 emission during growing season in an alpine swamp meadow ecosystem of Qinghai-Tibetan Plateau
To investigate the interactive effects of global warming and increased nitrogen deposition on ecosystem respiration,a short-term experiment was carried out during growth season in an alpine swamp meadow of Qinghai-Tibetan Plateau,using open top champers (OTC) and nitrogen addition to simulate warming and nitrogen deposition,respectively. Warming,nitrogen addition, and their interaction significantly increased ecosystem respiration rate by affecting plant biomass, soil microbial quantity and activity,and soil nutrient status. The correlations between ecosystem respiration and each of the environmental factors were exponential or quadric multinomial,with the significance levels of such regressions declining with the increases of complexity of treatments. As soil water availability is sufficient in swamp meadow,air temperature and soil temperature at the depth of 5 cm could explain 80% of the variations of ecosystem respiration. Warming significantly increased above- and below-ground biomass,and enhanced the proportions of belowground biomass. Nitrogen addition significantly increased above-ground biomass and had no effect on below-ground biomass. Under warming condition,nitrogen addition significantly increased above-and below-ground biomass,but with no impacts on biomass allocation.