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分析了黄土高原沟壑区森林小流域和自然草地小流域的水文效应，并利用实测资料和模型计算结果比较了两流域的水循环特点，结果发现在郁闭度相同的情况下，森林小流域较自然草地小流域有较小的径流量、较大的蒸散量和较低的３ｍ土层平均含水量，也就是说森林的覆盖增强了水分小循环，削弱了水文大循环，并导致土壤含水量降低。同时也发现森林的上述水文效应仅当其郁闭度达到一定程度时才能表现出来。通过比较两类生态系统植物生长的土壤水分环境条件和水分利用率，认为黄土高原沟壑区在大力发展林业时应以沟谷为主
The hydrological effects of small watersheds and natural grasslands in the gully region of the Loess Plateau were analyzed. The characteristics of the water cycle in the two basins were compared with the measured data and the model calculation results. The results showed that under the same canopy density, Grassland small watersheds have smaller runoff, larger evapotranspiration and lower average water content of 3m soil, which means that the forest cover enhances the small water cycle, weaken the hydrological cycle and lead to the decrease of soil water content . At the same time, it is also found that the above hydrological effects of forests can only be manifested when the degree of canopy closure reaches a certain level. By comparing the environmental conditions of soil moisture and water use efficiency of plant growth in two types of ecosystems, it is considered that the gully area in the Loess Plateau should be mainly dominated by valleys when vigorously developing forestry