基于土壤水分平衡的沙地草地最优植被覆盖率的研究

本文从土壤水分平衡出发，用动态仿真模型方法研究我国北方干旱半干旱沙地草地土壤不分平衡与立地条件，如坡度、坡向、土壤物理性状及植被覆盖率之间的关系。有如下初步结论和论点产生：（１）地表因植被的存在而形成的结皮对降水入渗到土壤中的阻滞作用几乎可以忽略。只有在坡度很大，瞬间降水强度很大时，结皮表面才可形成较大的迳流；（２）土壤水分的平衡随植被的覆盖率变化的情况取决于立地条件的差异，笼统地讲“植被覆盖率越

A STUDY ON THE OPTIMAL VEGETATION COVERAGE FOR SANDY GRASSLAND IN NORTHERN CHINA BASED ON SOIL WATER BUDGET

A simple simulation model is developed for soil water dynamics on a sandy slope with different soil physical properties, different geographical locations, different aspects and slopes and different vegetation types and coverage. The model is parameterized with recent colfeeted experiment data from the target area. Conclusions are: I ) the effect of resistance to penetration of precipitation to soil by the "shell" formed on the surface soil with organic mat ters and thus runoff in most cases are neglegible compared to the evapotranspiration, except with a very steep hill; 2) variation of yearly average soil water content is affected by all the factors listed above. The effect of plant coverage is complicated by other factors such as topography(slope and aspect) and root resistance to perculation. Simple conclusion can not be drawn without specifications of all these parameters.