Abstract:

Abstract  Using rainfall erosion data from a woodland and a grassland runoff plot in Suide, Yanan and Ansai on the loess plateau, the effective cover rate of woodland and grassland for soil and water conservation in different rainfall and slope conditions was analyzed. The relationship between the critical effective cover rate (v) and a rainfall index (product of total rainfall amount and maximum 30 rain rainfall intensity represented by (Pi₃₀)) and slope steepness (s) is:

            woodland: v = -103.29 + 33.81log (Pi₃₀) + 75.38log(s)

            grassland: v = -103.20 + 34.62log(Pi₃₀) + 78.97log(s)

The results indicate that the effective cover rate of woodland and grassland increases with increasing rainfall and slope when soil and vegetation are relatively in the same condition, the conditional effect of rainfall and slope on effective cover rate weaken when the critical effective cover rate reaches a certain level. When other conditions remain equal, the suggested effective cover rate of grassland is higher than that of woodland in the same soil and water conservation effectiveness. Finally, through a rainfall frequency analysis, a critical effective cover rate of wood and grass land to fight different rainstorm is obtained.

Key words: Loess plateau, Woodland and Grassland, Soil and water conservation, Effective coverage