Effects of five years’ nitrogen deposition on soil properties and plant growth in a salinized reed wetland of the Yellow River Delta

Abstract

Atmospheric nitrogen (N) deposition caused by human activities has been shown to have significant impacts on ecosystem structure and function, but the reported impacts have been inconsistent among studies. To test the effects of N deposition on a salinized reed wetland, we built a long-term nitrogen deposition experimental platform in the Yellow River Delta (YRD), China. The present study investigated soil chemical properties, soil enzyme activities and plant growth parameters after five years of N deposition. Results showed that the concentration of NH4-N and NO3-N increased significantly with the increasing level of nitrogen addition, but no significant influences were observed in total nitrogen (TN), total organic carbon (TOC) and available phosphorous (AP) across N addition treatments. Higher amounts of N addition significantly increased the urease activity (Ure) and alkaline phosphatase activity (Alp), but did not enhance the activity of invertase (Inv). The activities of Ure and Alp were positively correlated with the concentration of soil NO3-N, TN and TC, respectively, but negatively correlated to soil salt content. Meanwhile, the plant height and productivity were significantly stimulated, and the surface soil salt content decreased significantly. The results suggest that atmospheric N deposition may help improve the function of salinized reed wetland ecosystems in the YRD by increasing soil nutrient content, stimulating soil enzyme activity and enhancing plant production.