Effects Of Long-term Enclosure And Grazing Intensity On Spatial Heterogeneity Of Plant Diversity And Soil Nutrient In Typical Steppe

Soil spatial heterogeneity is an important factor for the formation and maintenance of terrestrial ecosystem biodiversity.Research on the impact of different grassland utilization and managements on the spatial heterogeneity of plant communities and soil resources is of paramount importance to protect grassland biodiversity,maintain grassland ecosystem function and sustainable grassland management.In this study,two enclosed plots(in 1983 and 1996)and plots with four grazing intensities in the typical steppe of Xilin Gol were selected.Two different spatial heterogeneity components(i.e.,coefficient of variation(CV)and spatial structure variation:(C/(C+C₀))were selected to reveal the effects of long-term enclosure,grazing and topography on the spatial heterogeneity of diversity indexes(e.g.,species richness,Shannon-Wiener and Simpson)and soil nutrient contents(e.g.,total soil carbon,total nitrogen,available phosphorus,available kalium,available nitrogen using sampling methods with small-scale and high-density,classical statistical and geostatistical analysis.The main results were as follows:1.Compared with enclosed plots for 24 years,the species richness and Shannon-Wiener were significantly increased in enclosed plots for 37 years,and the contents of total carbon,total nitrogen,available phosphorus,available kalium and nitrate nitrogen also increased;There was no significant difference in the variation coefficient and spatial structure of species diversity and soil nutrients between the two enclosed plots.The spatial structure variation of soil available nitrogen was much higher in enclosed plots 37 years.2.Light grazing significantly reduced species richness and Shannon-Wiener index,while heavy grazing significantly increased three diversity indexes,moderate grazing significantly reduced soil total carbon and total nitrogen content.Heavy grazing significantly reduced the available nitrogen content,light grazing significantly reduced available phosphorus content,and different grazing intensity had no significant effect on soil available kalium content.3.Grazing intensity had no effect on the variation coefficient of species diversity and soil variation coefficient,but affected its spatial structure variation.The different grazing intensities significantly increased the spatial structural variation of Shannon-Wiener and Simpson indices,reduced the spatial structural variation of total carbon and total nitrogen,and increased the spatial structural variation of available kalium;Light and moderate grazing significantly reduced species richness and soil available phosphorus of spatial structure variation;Soil available nitrogen spatial structure variation was not affected by grazing intensity.4.After excluding grazing,slope position had weak effects on species diversity,soil nutrient content and spatial structure variation,but did no effect on variation coefficient.With increaseing slope,the species richness,Shannon-Wiener and Simpson decreased significantly,and the spatial structure variation increased significantly.The spatial structure variation of soil total carbon,total nitrogen,available phosphorus and nitrate nitrogen increased significantly.The contents of soil total carbon,total nitrogen and available nitrogen were much lower in the middle slope than in the upper and lower slope.5.Grazing weakened the influence of slope position on spatial structure variation in plant diversity index,soil total carbon and total nitrogen,so that there was no obvious difference among slope positions.The influence of slope position on soil total carbon,total nitrogen and available nitrogen content was much greater than grazing;With increasing slope,the spatial structure variation in available phosphorus under different grazing intensities.