根据植被估算黄土高原的自然侵蚀和加速侵蚀──以安塞县为例

Estimation of Natural Erosion and Accelerated Erosion of Human Action on Loess Plateau 一Taking Ansai County as an Example

植被具有很好的水土保持作用。已有的研究成果证实：当森林郁被度或植被群落总盖度或森林覆盖度达到４０％左右时，植被的水土保持效益发生质的飞跃，较之裸荒地可减少土壤流失５０％以上；当植被群落总盖度达到８０％时，就能基本控制水土流失。目前黄土高原的植被很差，以安塞县为例，林草总覆盖度只有４５％，而且群落盖度很低，大多在３０％～５０％。而若无人类破坏，在同样的气候、地质条件下，安塞县的自然植被类型为森林和疏林灌丛草原，植被群落总盖度在８０％、乃至９０％以上，根据植被的水土保持规律和有无人类破坏情况下的植被对比情况，计算了黄土高原安塞县无人类破坏情况下的自然侵蚀及其占目前的总侵蚀量的比重。结果表明：位于黄土高原丘陵沟壑区的安塞县，自然侵蚀仅占总侵蚀量的９．５５％，按最不利的情况估计也只占１６．７６％，而若按较有利的情况估计则只占２．０３％。说明人为加速侵蚀占目前黄土高原总侵蚀量的绝大部分。

It is showed by many studies that vegetation has very strong effect on water and soilconservation,When the total vegetation coverage density of plant community is great than 40%,vegetation can diminish more than 50%of the total soil erosion with respect to naked land. If thetotal coverage density of plant community is great than 80%, vegetation will basically control all thesoil erosion. Now,tinder the condition of human disturbing,the real vegetation coverage density onloess plateau is generally lower than 40%. If there were no human action,under the same conditionof clamate and geology ,the total vegetation(whether forest or steppe)coverage density would begreat than 80%on loess plateau according to the ecologic theory and the remnant good vegetation insome rare areas on loess plateau. Through the comparison of the real vegetation and the possiblevegetation under the condition of no human action to all kinds of land,we come to the conclutionthat the accelerated erosion by human action is about 90%of the total erosion at present on loessplateau.