Influence of Vegetation Characteristics on Soil Denitrification in Shoreline Wetlands of the Danjiangkou Reservoir in China

Soil denitrification in reservoir shoreline wetlands is an important process for remov- ing excess inorganic nitrogen from upland runoff and controlling eutrophication in aquatic ecosystems. As yet, little is known about the influence of vegetation characteristics on the soil denitrification potential in reservoir shoreline wetlands, although vegetation can affect both denitrifying bacteria and soil properties. In this study, we measured the spatial variability of denitrification enzyme activity (DEA) using acetylene block method in shoreline wetlands of the Danjiangkou Reservoir, a water source of the South-to-North Water Transfer Project in China. Results indicated that DEA ranged from 0.001 to 2.449 μg N (N 2 O) g -1 h -1 , with a mean of 0.384 μg N (N 2 O) g -1 h -1 . DEA varied significantly among five representative plant communities and the highest DEA (0.248-2.449 μg N (N 2 O) g -1 h -1 ) was observed in the Polygonum hydropiper community. Plant biomass and vegetation cover were significantly and positively related to DEA and together explained 44.2% of the total variance. These results suggest that vegetation characteristics should also be considered in assessing soil denitrification capacity and restoring shoreline wetlands for nitrogen pollution removal in the Danjiangkou Reservoir after dam heightening.

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