Heterogeneity of soil structure and fertility during desertification of alpine grassland in northwest Sichuan

摘要

The variations of soil structure and soil physical–chemical properties in the process of alpine grassland desertification were revealed, and the indicators of grassland desertification were put forward in order to deepen the understanding of the law of degradation succession and development of alpine grassland. It was used to provide scientific basis for ecological restoration and improvement of ecological service function of alpine grassland. With severe desertification alpine grassland as the core in the Hongyuan County, Tibetan Qiang Autonomous Prefecture of Ngawa, Sichuan Province, China, along both the directions of wetland and arid grassland, the heterogeneity of soil structure and soil fertility in both directions was studied by the analysis of the mean weight diameter (MWD), geometric mean diameter (GMD), >0.25?mm aggregate content (R _(0.25)), fractal dimension (D ), soil bulk density, soil moisture content, and soil nutrients. Our results showed that MWD, GMD, andR _(0.25)all gradually increased, but theD decreased with the reduction in the degree of desertification in the arid grassland and wetland, resulting in the strong stability of soil structure. The decreasing rate of theD in the direction of arid grassland was faster than that of wetland. Therefore, soil structure stability and erosion resistance in the direction of arid grassland were stronger than that of wetland soil; theD had different response to aggregates with different particle sizes. The aggregate less than 0.25?mm (r ?=?0.981,P ?