红壤丘陵区经济林坡地氮磷流失特征

Losses Characteristics of Nitrogen and Phosphorus of Economic Forest in the Slope of Red Soil Hilly Region of South China

为了探究红壤丘陵区经济林坡地氮磷流失时间分布规律,以及地形坡度和林下管理措施对氮磷流失的影响作用,选择永康市方山柿经济林坡地为试验区,在区域内设置7个具有变量对比的标准径流小区,每个径流小区都设有沉砂池,用于收集产生的径流,并且在一年的时间内,对于每个小区的氮磷流失情况进行监测,结果表明:(1)试验区内坡顶、凸坡和凹坡的不同地形条件氮磷流失差异明显,且均符合坡地养分流失的"坡度临界"规律,临界坡度在10.22°和18.55°之间。不同地形坡度径流小区的TN和NO-3-N流失强度关系为坡顶>凹坡>凸坡。NH+4-N和TP流失强度关系为凹坡>坡顶>凸坡。TP、TN、NH+4-N和NO-3-N的年内流失均呈幂函数型增长。(2)试验区氮磷的径流流失均存在显著的降水同步性特征,TP、TN、NH+4-N和NO-3-N在雨季(6月梅雨季节和8,9月台风季节)的流失量占全年总流失流量的50%左右。(3)通过对照小区监测,发现保留地被覆盖的7号径流小区的TN、NH+4-N、NO-3-N和TP径流浓度比除草的6号径流小区分别减少9.0%,34.7%,25.5%和8.6%,草被覆盖对于经济林坡地减少氮磷径流流失上均具有明显效果。

In order to explore the time distribution of nitrogen and phosphorus loss of economic forest in slope of red soil hilly region, as well as the influence of terrain slope and forest management practices on nitrogen and phosphorus loss. The economic forest in Yongkang was took as experimental area and set on seven standard runoff plots with variable contrast. Each runoff plots had a grit chamber to collect the runoff. In a hydrological year, a located monitoring of nitrogen and phosphorus loss was conducted. Results showed that： （1）Obvious differences existed among crest, convex and concave slope in nitrogen and phosphorus losses of runoff. The influence on nitrogen and phosphorus losses of different slopes conditions met the critical gradient law. The critical slope was between 10.22° and 18.55°. The relationship of losses on TN and NO3- --N was crest ）concave ）convex. And the relationship of losses on NH4＋-N and TP was concave crest 〉convex. Losses of TP, TN, NH4＋ -N and NO3- -N had typical power function increase in the hydrological year. （2）Nitrogen and phosphorus losses were seasonal. Most losses occurred in the rainy and typhoon season. The TN, TP, NO3--N and NH4＋ -N losses of these 3 months respectively accounted for about 50% of the year. （3）Through monitoring of the contrast grit chamber, it indicated that grass coverage made obvious effects on reducing nitrogen and phosphorus losses of the runoff plots. TN, NH4＋ -N, NO3- -N and TP content of runoff losses in the No. 7 plot decreased by 9.0%, 34.7%, 25.5% and 8.6%, respectively compared with those in No. 6 plot.