Spatial Variability of Greenhouse Gas Effluxes and Their Controlling Factors in the Poyang Lake in China

CO2, CH4, and N2O (GHG) emissions are globally important in China, but few field observations have been made in freshwater lakes. In this paper, we measured the GHG effluxes from 44 sampling locations among four sub-regions in Poyang Lake in China in October 2010 using floating chambers. The mean CO2, CH4, and N2O effluxes were 0.23 μmol m ·s, 3.0 nmol·m·s, and 0.11 nmol m·s, ranging from -0.25 to 0.54 μmol·m·s, 1.4 to 8.9 nmol m·s, and 0.012 to 0.21 nmol·m·s for the CO2, CH4, and N2O efflux, respectively. We found differently related tendencies between GHG effluxes and environmental parameters for each sub-region and, totally, four sub-regions together. The 16 environmental factors explained the GHG effluxes with 55%, 70%, and 89% of the variation in CO2, CH4, and N2O efflux, respectively, in Poyang Lake. Our analysis revealed that sediment C/N ratio, water depth, and the difference of air-water temperature were significantly contributing variables for GHG effluxes in the lake.