Study On The Soil Water Cycle On Slope With Different Conditions Of Vegetation Covering In Water-Wind Erosion Crisscross Region

The water-wind erosion crisscross on the Loess Plateau is a special region with severe soil erosion and brittle ecosystem and being the main sediment source of the Yellow river. 60 percent of total farmland in the Loess Plateau are sloping land and its erosion nearly 50-60 percent of the total erosion. So the return of the croplands to forestland and grassland on hill slopes is an effective approach to improve the quality of the ecosystem. But croplands to forestland and grassland conversion should be done in such a way that vegetation should be planted according to the quantity and spatial distribution of soil moisture on slope lands. Four different typical vegetation man-made slope plots were bulit in Liudaogou watershed in Shenmu county, north of Shaanxi province, for looking at water infiltration,evapotranspiration,soil water redistribution,erosion and scouring to obtain the mechamisms and characteristics of soil water cycle on the slope with different conditions of vegetation covering and soil erosion. The results showed that:(1) Alfalfa land was the best, then Caragana kanshinskii land was better than wilderness meadow, and bare land was the worst in terms of rainfall conversion efficiency and soil moisture restoration. In the soil water redistribution process, the wetting front movement with time of four conditions of vegetation could be described by a power function.(2) Comparing among the three types of 2-years vegetated plots, the vegetation coverage of alfalfa land was the greatest, Caragana kanshinskii land was the lowest, and wilderness meadow was middle. The water stored in the soil profile of alfalfa was the greatest, Caragana kanshinskii was the lowest, and grass was middle. The yield of Caragana kanshinskii land was the greatest, alfalfa land was the lowest and wilderness meadow was middle. The grow rate of Caragana kanshinskii was the fastest, alfalfa was the slowest, and grass was middle. The evapotranspiration intensity in 2005 was in the order: alfalfa land> Caragana kanshinskii land > wilderness meadow> bare land.(3) Measured results of evapotranspiration by micro-lysimeter,water balance method,Trimble TDR indicated the same tendency between different vegetation covering plots. Water balance method is better in calculation of the evapotranspiration in large area, micro-lysimeter is better in bare land, and Trimble TDR is better in accuracy for small plots.