| Soil is a continuous variant in space—time,which has high degree spatial heterogeneity. The essential of grazing is an ecological disturbance,which is one of the most important causes of spatial heterogeneity in ecological system.In this study,the ways of investigating in outdoor typical field and analysis in laboratory were used,and the traditional statistics and geostatistics were used to analysis and treat the data,the variogram analysis of geostatistical and Kriging estimation method were used to study the soil nutrition spatial variances of degraded Seriphidium desert grassland,the main results are as follows:1.The related coefficients between SOM and total nitrogen and total phosphorus and available phosphorus are higher,the positive correlation between SOM and total nitrogen and total phosphorus are extremely significant,the positive correlation between SOM and available phosphorus is significant.2.The change trends of SOM,total nitrogen,total phosphorus,available nitrogen and available potassium are moderate degradation grassland＞severe degradation grassland＞extreme degradation grassland at 0-10 cm and 10-20cm soil layer.The change trend of Soil available phosphorus is severe degradation stage＞moderate degradation stage＞extreme degradation.3.Variations coefficient(CV) of soil nutrients in different three degradation grassland are all in the range of 10～100%,which are medium variant,only the variation coefficient of soil total potassium was low(7%) in severe degradation grassland.The Semi—variance model of soil nutrition in different three degradation stages were best described by Exponential model, Spherical model,Gaussian model,Linear model.Spatial correlations of available nitrogen and total potassium were weak at 0～10cm soil layer in moderate degradation stage.Stage of moderate degradation of 0～10cm layer of soil had weak spatial autocorrelation.The ratio of nugget to sill of available K was 76.1%,the Spatial autocorrelation was weak.The Spatial correlation of soil nutrients in extreme degradation was in middle.The soil nutrients had middle spatial correlation in 10～20cm soil layer of there degradation stages.Judging from the spatial correlation distance,the soil variance tune ranged was 42m～61m in moderate degradation stage,the soil variance tune ranged was 7m～61m in severe degradation stage,the soil variance tune ranged was 22m～61m in extreme degradation stage.The interpolation figure based on Kriging analysis that SOM,available phosphorus available nitrogen were highly similar.4.Organic matter and total phosphorus of Moderate degradation,organic matter of severe degradation,and available phosphorus of extreme degradation at different directions have the same sill and have different variance tune range,which are typical variation of the geometric anisotropy,the nugget value and sill of other soil nutrients have some differences at different directions,Scale of spatial variability of all nutrients is different.5.The variability isotropic of Organic matter and total amount available nutrients and available nutrient in moderate and severe degradation had medium spatial autocorrelation, with the degradation increased,the Spatial autocorrelation Weakened.The spatial autocorrelation of total nitrogen,available nitrogen and total potassium in extreme degradation is weak.The ratio of nugget to sill was higher than 75%,the spatial correlation were affected stronger by man—made factors(grazing activities) than the inherent factor of soil parent material and so on,the spatial autocorrelation were weakened by the human factor.6.The results of Kriging interpolation showed that the nutrient in soil have highly spatial heterogeneity.
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