浑善达克沙地小叶锦鸡儿灌丛的空间异质性

豆科锦鸡儿属(C arag ana)植物因其可以生物固氮而在草原生态系统中具有特殊的地位。定量分析小叶锦鸡儿(C arag anam icrophy lla)灌丛在浑善达克沙地不同生境条件下的分布格局,有助于理解植被与土壤养分循环之间的关系和合理制定退化沙地的恢复对策。采用地统计学中的半方差分析和分形分析两种方法研究了浑善达克沙地小叶锦鸡儿灌丛的空间分布格局,分析了不同生境中小叶锦鸡儿灌丛的植被、土壤水分和养分间的相关性。结果表明:(1)小叶锦鸡儿灌丛在3种生境条件下(滩地、固定沙丘和半固定沙丘)的盖度、土壤有机质和全氮的空间分布符合球状模型,空间自相关显著;(2)土壤pH值在滩地和固定沙丘的空间分布符合球状模型且空间自相关显著,但在半固定沙丘空间自相关不显著;(3)土壤水分在3种生境中的空间分布都符合线性模型,空间自相关显著。(4)植被的变异尺度(变程)小于各个土壤要素的变异尺度。植被(小叶锦鸡儿灌丛)的分布和形成过程决定了土壤养分的分布和形成过程。当地的小叶锦鸡儿灌丛在养分“沃岛”现象的形成中起了重要作用,合理的利用和布局当地的小叶锦鸡儿灌丛的分布,可以更加有效地补充草地生态系统的养分,从而有利于加快生态系统的恢复进程。

Spatial heterogeneity of Caragana microphylla shrub communities in the Otindag Sandland

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.