摘要
水土保持林有效覆盖率是水土保持林建设中的一个重要指标。该术语虽出现较早且已被逐渐采用，但由于缺乏严格的定义和统一确定标准，以至水土保持林有效覆盖率数值从３０％～７５％，这严重影响了水土流失区林业生产的宏观决策。通过对水土保持林系统的详细分析，定义了水土保持林有效覆盖率为在一定防护范围内的土壤流失量等于允许流失量时的森林覆盖率：ａｅ￣（－ｂＦ）＝ＳＬＡ。并指出有效覆盖率的确定涉及２个方面、３个步骤；水土保持林有效覆盖率为时间和空间的函数。此外还以黄土高原水土流失区为例，介绍了水土保持林有效覆盖率的确定方法。
Effective cover rate for soil and water conservation forests is an important index in the construction of forestry.This terminology appeared early,but its value are fluctuating from 30%to 75%for there is not a definite concept and the same method for determining it.In view of this,based on analvsis of the svstem of soil and water conservation forest in detail,he concept of the effective cover rate for soil and water conservation forest is advanced as the cover rate when the amount of soil loss is equal to the permissible amount of soil loss in a given range:ae￣((-bF))=SLA.And its determining method is concerned with two important aspects and three steps,the effective cover rate is a function of time and space. Finallv the soil and water loss re-gion in Loess Plateau was exampled to introduce the determining method of effective cover rate.
关键词
水土保持林
有效覆盖率
允许失量
水土流失
黄土高原
soil and water conservation forest
effective cover rate
permissible amount of soil loss
function of time and space
