山核桃林闭合区内径流氮磷流失特征

为研究自然降雨条件下整个水文年中山核桃Carya cathayensis林闭合区内径流-土壤-泥沙氮磷流失特征，以杭州市临安区山核桃林闭合区作为研究对象，测定总氮、总磷和水解氮等指标。结果表明:降雨是影响径流的重要因子，径流量和降雨量存在显著正相关（P < 0.05）；在2016年6月至2017年5月的观测期间，山核桃林径流水中氮素平均质量浓度较高（2.86 mg·L-1），水解氮是氮素流失的主要形式，占总氮的60.7%；径流水中磷素平均质量浓度较低（0.01 mg·L-1）。径流氮质量浓度与土壤碱解氮之间不存在显著的相关性（P>0.05），而径流磷质量浓度与土壤有效磷质量分数之间呈显著相关（P < 0.05）；径流中总氮和总磷的年累积流失量分别为11.01 kg·hm-2·a-1和133.70 g·hm-2·a-1，泥沙中全氮和全磷的年累积流失量分别为11.49和1.12 g·hm-2·a-1，山核桃林氮磷流失严重。

Nitrogen and phosphorus loss in runoff and sediment for a closed zone of a Carya cathayensis stand

This study was designed to determine the characteristics of nitrogen (N) and phosphorus (P) losses in runoff and sediment with only natural rainfall in a Carya cathayensis stand for a whole hydrological year. The closed zone of a C. cathayensis stand in Lin'an District of Hangzhou setted up a monitoring station for location monitoring was selected to measure total nitrogen (TN), total phosphorus (TP), and dissolved nitrogen (DN) from June 2016 to May 2017 and analyzed. Results showed a significantly positive linear correlation (r=0.940 6, P < 0.05) between runoff and rainfall. During the observation period, the average concentration of N in runoff water was far higher (2.86 mg·L-1) than mass concentration of eutrophication in water. DN in the runoff was a main form of N loss accounting for 60.7% of TN; whereas, the average concentration of P was lower (0.01 mg·L-1) than concentration in other economic forest runoff. There was no significant relationship (P>0.05) between N concentration from runoff and soil available N, but P concentration from the runoff was significantly linearly related to available P (P < 0.05). Accumulated loss of TN in the runoff was 11.01 kg·hm-2·a-1 and TP was 133.70 g·hm-2·a-1; whereas, accumulated loss of TN in the sediment was 11.49 g·hm-2·a-1 and TP was 1.12 g·hm-2·a-1. Thus, in the C. cathayensis stand, rainfall was an important factor affecting runoff with losses of N and P serious.