人工草地在黄土高原水土保持中的减水减沙效益与有效盖度

根据黄土高原缓德，延安，离石，安塞等地的草地径流小区资料，分析不同次降雨条件下，人工草地的送还不减沙交益和水土保持有效盖度，结表明，当降雨指标小于坡耕地侵蚀性降雨标准时，草地并不发挥水土保持作用，减少减沙效益为零，当降雨指标大于坡耕地侵蚀性标准时，其减水减沙效益随着降雨指标的增大而送还上，在土壤相对稳定的情况下，要使土壤侵蚀模数小于某一定值，降雨，地形和植被覆盖因者之间存在着一定的相互制约关系，即草地的盖度随着降雨和坡度的增大而增大，当盖度达到一定程度时，降雨与坡度对其的制约影响减弱，建立草地的减水减沙效益指标体系，及草地水土保持临界有效盖度与降雨坡度的关系式，并结合降雨频率的分析，得出草地抵抗不同年暴雨的临界有效盖度。

The Benefits of Runoff and Sediment Reducing & Effective Cover Rate for Soil and Water Conservation of Artificial Grassland on Loess Plateau

Based on the runoff plots in the Suide,Yanan,Lishi and Ansai area on the loess plateau,the benefits of runoff and sediment reduced by grassland and eff ective cover rate of grassland for soil and water conservation under different rainfall conditions are analyzed.The result showed that there will be no benefits of soil and water conservation when the rainfall index is smaller than that of erosive index of sloping field,otherwise,the benefits will be decreasing with the rainfall index increasing.There will be a conditional relationship among rainf all,landform and vegetation when the soil erosion modulus below a certain value, and the effective cover rate of grassland increase with increasing rainfall and slop when soil are relatively in the same condition,the conditional effect of rainfall and slope on effective cover rate weaken when the critical effective cover reaches a certain level.Finally,through a rainfall frequency analysis,a critical effective cover rate of grassland to fight different rainstorm is obtained.And the systems of soil and water conservation index of grassland with different coverage in different rainfall conditions,and the relationship between the critical effective cover rate rainfall index and slope steepness are established.