Denitrification Potential of Marsh Soils in Two Natural Saline-alkaline Wetlands

Little information is available on denitrification potential of marsh soils in natural saline-alkaline wetlands. The denitrifica- tion potentials of an open wetland in the floodplain （Erbaifangzi wetland） and a closed wetland （Fulaowenpao wetland） in backwater areas in Jilin Province of Northeast China were monitored by an anaerobic incubation at 30℃ for 25 days. Our results showed that the relative denitrification index （RDI） increased gradually with incubation time, and showed a rapid increase in the first 5 days of incuba- tion. The RDI values declined quickly from surface soils to subsurface soils and then kept a small change in deeper soils along soil pro- files over the incubation time. Denitrification proceeded much faster in the top 20 cm soils of open wetland than in the closed wetland, whereas no significant differences in RDI values were observed in deeper soils between both wetlands. The RDIs were significantly negatively correlated with bulk density and sand content, while a significantly positive correlation with clay content, soil organic matter, total nitrogen and phosphorous. The maximum net NO3--N loss through denitrification in 1 m depth were higher in the open wetland than the closed wetland with higher soil pH values. Future research should be focused on understanding the influencing mechanisms of soil alkalinity.