Effects of Livestock Grazing and Enclosure on Vegetation and Its Spatial Variability in Horqin Sandy Steppe,Inner Mongolia,China

Abstract

Based on a series of field investigations,in this paper the characteristics of vegetation in a degenerated sandy steppe in Horqin Sandland are compared.Some traditional and geostatistical methods are used to identify the changes of the coverage,richness,mean height and density of vegetation and Shannon-wiener index and its effect on the spatial variability of vegetation in the sandy steppe.The results show that the coverage,mean height and Shannon-wiener index of vegetation in the steppe plots with enclosure are significantly higher than that under livestock grazing.Geostatistical analysis results reveal that the spatial variability of the vegetation coverage in the steppe plots with enclosure and the plant density in both of the steppes with enclosure and under livestock grazing can be well simulated with the spherical model,while the richness and Shannonwiener index of vegetation in the steppe plots with enclosure and the coverage,richness and Shannon-Wiener index of vegetation under livestock grazing can be well expressed with the exponential model.It is obvious that the variables examined show lower level of Semivariance in the plots with enclosure than that in the plot under livestock grazing.The ranges of spatial autocorrelation for the Shannon-wiener index,coverage and richness are 161.91 m,36.73 m and 85.02 m in the plots with enclosure,and 51.78 m,24.981 m and 5.64 m in the plots under livestock grazing,respectively.These reveal that livestock grazing results in an increase in spatial variability of vegetation in degenerated sandy steppe.