Distribution characteristic of dried soil layer in Wangdonggou Watershed in gully region of the Loess Plateau
黄土高源沟壑区流域土壤干层的分布特征

Dried soil layer results in soil degradation,slows down the vegetation growth rate,makes it withering,and imperils serious ecological environmental construction in northern China,especially in the gully region of the Loess Plateau.It has aroused our attention in recent years.Based on this phenomenon,dried soil layer in Wangdonggou Watershed in gully region of the Loess Plateau was studied in this paper.First,the measured indexes of dried soil layer are discussed according to the soil properties.The result shows that in Wangdonggou Watershed,the soil layer under2m with a moisture be-low14%can be regarded as dried soil layer.Second,according to the soil moisture profile and the degree of soil water conditions affect-ing vegetation growth,the dried soil layer can be divided into4grades such as non-dried,low-grade,medium-grade,and serious grade.Third,the distribution characteristics of dried soil layer in the watershed are analyzed.The result shows that dried soil layer is a general soil water phenomena in the whole watershed.In general,farm land>grass land>orchard land>forest land in the dryness degree and thickness of dried soil layer.In the same time,distribution characteristics of dried soil layer are affected by plant density,age,biomass,slope degree,slope aspect,and slope direction.Finally,some advices on vegetation construction are put forward:1)to adjust the land use structure,increase the proportion of rosebush and grassland to form a reasonable land use struc-ture;2)to develop the native tree categories to carry tree categories diversification off;3)to re-duce community density and control community productivity to assure a relative balance of water consumption and circumstance water supply;and4)in the process of vegetation regeneration and rehabilitation,the effect of ecologic niche on the distribution of soil water should be consid-ered fully to choose feasible category and keep reasonable vegetation density.