LAUSR

The interactions between soil organic matter (SOM) and micro-topography and vegetation drive the ecology of wetland ecosystems. We investigated the distribution pattern of SOM and its relationships with elevation, slope, aspect, topographic wetness index (TWI), and normalized difference vegetation index (NDVI) in Poyang Lake, the largest freshwater lake of China. The local parameters were obtained by applying a geographically weighted regression model. Local parameter differences were analyzed between two dominant wetland types (dish-shaped pit wetland and delta wetland) and among nine land-cover types (deep water, shallow water, very shallow water, mudflat, meadow, sparse grassland, Carex-Phalaris community, Phragmites-Triarrhena community, and Artemisia-Cynodon community). The SOM response to elevation was most sensitive in the dish-shaped pit wetland and mudflat, whereas the effects of slope on SOM were more significant in the delta wetland and vegetated land-cover types. Relatively weaker correlations were observed between SOM and aspect in all study zones. Positive correlations were found between SOM and TWI, which was strongest in dish-shaped pit wetland and deep water. NDVI was positively related to SOM in most areas, but the relationships were not significant in the southern area and in the mudflat. This study helps to better understand the spatial heterogeneity of Poyang Lake.