Abstract: Wetland can produce and store large amount of organic matters, playing a significant role in the global carbon and nitrogen cycles, and in particular, greenhouse gases (CO2, CH4 and N2O) fluxes. Most of the previous studies are focused on the greenhouse gas emissions from peat lands, lakes, and crop fields, but few are targeted on reservoirs, especially those located in temperate zone. In this study, three greenhouse gases (CO2, CH4, and N2O) fluxes and their environmental determinants at different locations (eulittoral zone, reservoir entrance, and shallow water zone) in Yudushan Reservoir of Beijing were measured by using static opaque chamber-GC technique during the growth season (May, August, and October) in 2009 and 2010. A great variation in the greenhouse gases (CO2, CH4， and N2O) fluxes was observed among the sampling locations, and this variation was affected by the combined effect of sampling location and sampling month. In May, the CO2 flux in the eulittoral zone reached the highest (664.31 mg·m-2·h-1), which was significantly higher than that at the reservoir entrance and in shallow water zone. In August, the CH4 and N2O fluxes in the eulittoral zone was the highest (0.87 mg·m-2·h-1 for CH4 and 3.05 mg·m-2·h-1 for N2O), but the fluxes of CO2, CH4 and N2O in the zone had somewhat decrease after the vegetations above the ground were removed. Pearson correlation analysis indicated that CO2 flux was significantly positively correlated with soil temperature and redox potential at 5 cm depth and water total nitrogen content but significantly negatively correlated with above-ground biomass and water pH, CH4 flux was significantly correlated with surface soil temperature, above-ground biomass, and water pH but negatively correlated with water total nitrogen and NH4+ contents, while N2O flux was significantly correlated with water
total nitrogen content but negatively correlated with water pH. By the mean value estimation method, it was deduced that the total greenhouse gas emissions in the eulittoral zone, reservoir entrance, and shallow water zone during growth season were 15960, 2160 and -70 kg·hm-2 for CO2, 20.04, -7.05 and 14.8 kg·hm-2 for CH4, and 83.42, 3.79 and -1.54 kg·hm-2 for N2O, respectively, suggesting that the eulittoral zone was the most important zone for the greenhouse gas emissions in the Yudushan Reservoir.

Key words: plant functional trait, micro-topography, soil nutrient, species-level, community-level.