The Water Effects Of Removed Disturbance On Biological Soil Crust In Loess Area

Loess Plateau is shortage of water resources partly because of poor rainfall, which may be significantly affected by Biological Soil Crust in various water redistribution processes of soil evaporation, rainfall infiltration, runoff, sediment, soil water storage and so on. In this research, the soil hydrological effect under the condition of soil crust disturbance is divided into soil water content dynamic variation, rainfall runoff and soil evaporation by means of experiment in the field combined with laboratory analysis and the basic principles and methods of Soil Science and Ecology. Focus on the impact of removed disturbance on soil crust with different vegetation types. Main conclusions are as following:⑴The variation of the soil water content and water storage shows roughly similar trends with the distribution of precipitation, and demonstrate a significant time lag. Noticeable positive effects on soil water content and water storage is appeared after removing the disturbance of biological crust, this effect becomes more apparent especially in the case of vegetation covered.⑵The vertical variation of soil water content in different treatments is almost consistent, which decrease at first then increase, the fluctuation occurred when increasing. Soil water content in 0～130cm soil layer changes more rapidly, below 130cm vary little. After removing biological soil crust and vegetation, the change in soil water content is more stable.⑶On the whole, simple BSC can lower water infiltration, but the effect of BSC on soil water infiltration was not steady. Stipa bungeana and Caragana Korshinskii can significantly increase the infiltration; the infiltration increase further when BSC combined with vegetation, but the contribution of BSC is significantly lower than the vegetation. BSC reduce the ground runoff at the early stage of rainy season, while increase the ground runoff at the end. Stipa bungeana and Caragana Korshinskii can significantly decrease the ground runoff.⑷BSC has significant effects on soil erosion control, however, the contribution rates of BSC for reducing soil erosion varies widely in the conditions of different vegetation. Therefore, in the initial stage of vegetation growth (low coverage), the biological crust should be strongly protected against disturbance; when the vegetation developed to better stage (high coverage) and has very good effect of controlling erosion, that is, when the biological crust's contribution of reducing erosion decreased significantly, appropriate measures should be taken to disturb the biological crust, and thus to improve the soil water content in small-scale, accelerate the positive ecological succession.⑸BSC and vegetation has some inhibitory effect on soil evaporation, this can be attributed to BSC has higher capacity for holding water, enabling more precipitation remain in the surface soil longer; In addition, similar to the effect of vegetation, biological crusts form a kind of shell and cover the earth's surface, hinder the surface pores of soil, partly blocked the water transport and evaporation channels to a certain extent, which is not conducive to the conduct of soil evaporation.