黄土高原人工油松林水文生态效应

Studies on hydro-ecological effects of artificial Chinese pine stand in Loess Plateau

在陕北黄龙山区利用对降水和设置在林分中的径流小区进行长期定位观测的方法 ,研究了黄土高原主要造林树种油松林的水文生态效应 ,据 1 995～ 2 0 0 0年观测结果 ,中龄人工油松林林冠平均截留率为2 5 .1 % ,树干茎流量占大气降水量的 3.3% ,枯枝落叶层的截留率为 1 1 .6%。在森林的作用下 ,林地土壤的理化性质得到了明显的改善。与农地相比 ,林地容重低 8.6% ,有机质含量、全氮含量和阳离子代换量分别高 1 30 .1 %、84.2 %和 5 3.2 % ,细土颗粒组分比例增加。与此同时 ,林地地表径流量和土壤侵蚀量则分别减少 84.5 %和 99.9% ,表明了人工油松林巨大的水文生态作用。

Chinese pine (Pinus tabulaeformis Carr.) is widely distributed in the Loess Plateau and is one of the main species for afforestation in the region. In order to expound the role of its stand in controlling serious soil and water losses and the mechanism of the role a study on the hydro-ecological effects of the stand, including its canopy, litter and root system is carried out in the period from 1995 to 2000, using the long term observation on rainfall and runoff plots set up in its stand and the method of the physical and chemical analyses of its soil. The experimental stand is a representative middle-aged artificial chinese pine stand which is located in the Huanglongshan mountainous area of northern Shaanxi, where the average air temperature is 9.8℃, and the annual precipitation is 574.4mm. The density of the stand is 0.7, and the litter thickness under the stand averages 2~3cm. The results of the study show, that the intercepting rate of the canopy varies from 19.7% to 31.6% and on an average, is 25.1%. Its stemflow accounts for 3.3% of rainfall. The average intercepting rate of litter is 11.6%. It means that the stand can intercept 36.7% of annual rainfall in all, resulting in reducing net rainfall causing runoff on surface of soil. Litter and roots after death may decompose into organic matter and nutrient substances with the help of microbe, thus distinctly improving the physical and chemical properties of its soil. In comparison with farmland the volume weight of soil in woodland is decreased by 8.6%, while the content of organic matter and total N and CEC are increased by 130.1%, 84.2% and 53.2%, respectively. The proportion of thin soil particle in the woodland is increased too. Under the comprehensive action of the stand the surface runoff and soil erosion from the woodland are decreased by 84.5% and 99.9%, respectively, over the farmland, indicating the great hydro-ecological functions of chinese pine stand.