放牧强度对荒漠草原建群种短花针茅空间异质性的影响

[目的]探讨荒漠草原建群种短花针茅在不同放牧强度下空间异质性的特征和变化。[方法]以建群种短花针茅（Stipa breviflora）为对象,采用半方差函数、克里格插值法和多重分形维数等方法对其空间异质性进行研究。[结果]不同放牧强度下,短花针茅种群密度均值大小为重度放牧（HG）>禁牧（CK）>中度放牧（MG）;短花针茅种群具有多重分形特点;不同放牧强度下短花针茅空间分布有所差异,CK处理区结构比（C/C₀+C）最大,HG处理区次之,均大于75%,说明CK处理区和HG处理区都具有强烈的空间自相关性,而MG处理区最小,小于75%但大于25%,具有中等的空间自相关性;结构因素是导致短花针茅空间变异的主要原因。[结论]重度放牧增加了短花针茅种群密度,而中度放牧因家畜采食践踏作用小,导致短花针茅种群密度降低;在不同放牧强度下,结构因素是影响短花针茅空间异质性的主要因素;禁牧处理区内短花针茅种群空间分布最复杂,具有较强的空间异质性。

Effects of Grazing Intensity on Spatial Heterogeneity of Stipa breviflora as Constructive Species in Desert Steppe

[Objective] To assess the characteristics and variation of spatial heterogeneity of Stipa breviflora as constructive species in desert steppe under different grazing intensities. [Method] The constructive species of Stipa breviflora was taken as the research object. The semi-variance function, Kriging interpolation and multi-fractal dimension were used to assess its spatial heterogeneity.[Result] Under different grazing intensities, the mean population density of Stipa breviflora was heavy-grazing area （HG） > no-grazing area （CK） > moderate-grazing area （MG）; Stipa breviflora population had multi-fractal characteristics; the spatial distribution of Stipa breviflora varied under different grazing intensities; the structure ratio （C/C₀+C） of CK was the largest, followed by HG, and both of them were greater than 75%, indicating that CK and HG had strong spatial autocorrelation; the structure ratio （C/C₀+C） of MG was the lowest, which ranged from 25% to 75%, indicating that MG had moderate spatial autocorrelation; structural factors were the main causes of spatial variation of Stipa breviflora.[Conclusion] Heavy-grazing increases the population density of Stipa breviflora, while moderate-grazing decreases the population density of Stipa breviflora due to the low-intensity feeding and trampling from livestock; under different grazing intensities, structural factors mainly contribute to the spatial heterogeneity of Stipa breviflora; the Stipa breviflora population in CK has the most complex spatial distribution and strong spatial heterogeneity.