Spatial heterogeneity of Caragana microphylla shrub communities in the Otindag Sandland
浑善达克沙地小叶锦鸡儿灌丛的空间异质性

Caragana plants are among the important nitrogen-fixers in the Otindag Sandland,semi-arid area in China.They can provide with useful information about the relationship between vegetation and nutrient cycling as well as with powerful measure of restoration of the degraded sand land to quantify the spatial pattern of Caragana microphylla shrub communities in the various habitats.The aims of this study were to investigate the spatial patterns in C.microphylla shrub communities and resource heterogeneity in the Otindag Sandland.Using the semivariance analysis and the fractal analysis,the spatial patterns of C.microphylla shrub communities in three habitats were examined.The coverage of C.microphylla shrub communities,total N and organic C exhibited significant spatial autocorrelation in the three habitats,fitting the spherical model while the soil water content all fitted linear model.The soil pH did not exhibit significant autocorrelation in the semi-fixed sand dune but it did significant autocorrelation in the meadow and the fixed sand dune,both fitting the spherical model.The scales of autocorrelation of C.microphylla shrub communities were less than that of each soil factor,suggesting that distribution and formative process of C.microphylla shrub communities controlled the distribution of soil nutrient.The C.microphylla shrub communities were the most important factor affecting the process of the "fertility islands" of the soil nutrients in the sandland.Thus,reasonably using and placing C.microphylla shrub communities can supply the soil nutrients for the ecosystem more effectively.