The Changes of Soil Physical Properties in Arctic-alpine Grassland Desertification Process in Northwest Sichuan -Taking Litang County for Example

In this paper, taking arctic-alpine grassland in Litang County as the research object, the method of the spatial sequence instead of the tempoal sequence was used to analyze the changes of different desertified grassland types in soil physical properties in the area. Analysis results showed the total porosity and capillary porosity of soil had a decreasing trend in the desertification process, and the soil sand content increased continuously and the soil bulk density increased to different degrees. The intial stage of the arcticalpine grassland desertification in the northwestern Sichuan was the critical stage of desertification prevention and control because the variations of soil bulk density and porosity in the early desertification stage were greater than those in the desertification progress stage. The soil bulk density of the upper layer of the soil (0~20 cm deep) was less than that of the lower layer (20 cm~40 cm deep), but the total and capillary porosities of the upper layer of the soil were greater than those of the lower layer; Besides, the average sand content in natural grassland was relatively high, which indicated that the arctic-alpine grassland in northwest Sichuan had potential desertification material conditions.