以浙江省永康市方山柿经济林坡地为试验区,依据不同地形条件及林下管理措施,设置7个径流小区和沉砂池,定期采集沉砂池水样,测定径流中不同形态氮素浓度。通过为期一年的监测分析,得到如下结论:(1)试验区氮素流失与水文年内降水具有明显的同步性,氮素流失多发生在降水集中的梅雨和台风季节。这两个季节的降水量占全年降水的66.2%,TN、NO-3-N和NH+4-N流失量分别占全年总流失量的80.3%、78.2%和83.0%。(2)坡顶、凸坡和凹坡径流小区的氮素流失符合养分流失的“临界坡度”规律,临界坡度在坡顶(10.22°)与凹坡(18.55°)之间。水文年内TN和NO-3-N流失量关系为坡顶>凹坡>凸坡,NH+4-N流失量关系为凹坡>坡顶>凸坡。三种地形径流小区的年内氮素累积流失量均呈幂函数型增加。(3)对照林下管理措施不同的6号(林下除草)和7号(林下不除草)径流小区,发现草被覆盖对减少经济林坡地氮素径流流失具有明显效果。保留草被覆盖的7号小区比除草的6号小区的TN、NO-3-N和NH+4-N径流流失分别减少了22.1%、36.2%和44.1%。 Based on different topographic conditions and under-forest management measures, seven runoff plots and grit chamber were set up. The grit chamber water samples were collected on a regular basis, and the concentrations of different forms of nitrogen in runoff . Through the one-year monitoring and analysis, the following conclusions are obtained: (1) The nitrogen loss in the experimental area is obviously synchronized with the precipitation during the hydrological year, and the nitrogen loss occurs mostly in the rainy season and typhoon season in which the precipitation is concentrated. The precipitation in these two seasons accounted for 66.2% of the annual precipitation. The losses of TN, NO-3-N and NH + 4-N accounted for 80.3%, 78.2% and 83.0% of the total annual total losses respectively. (2) The nitrogen loss on the top, slope and depression runoff plots complies with the law of “critical slope” of nutrient loss with the critical slope between the top of the slope (10.22 °) and the concave slope (18.55 °). The relation between TN and NO-3-N loss during the year of hydrology is as follows: slope top> concave slope> convex slope, and NH + 4-N loss relation is concave slope> top slope> convex slope. During the year, all three kinds of terrain runoff communities showed a power function increase in cumulative nitrogen loss. (3) According to the management measures of undergrowth, No.6 (grass under weeds) and runoff No.7 (under weeds without forest), we found that the grass cover was effective in reducing the runoff of nitrogen from economic forest slopes. The runoff loss of TN, NO-3-N and NH + 4-N in No.7 plots of reserved grass decreased by 22.1%, 36.2% and 44.1% respectively compared with that in No.6 plots.