科尔沁沙地植物群落圆环状分布成因地统计学分析

调查发现，在科尔沁沙地中部部分梁窝状沙丘的丘顶、丘坡和丘间地，植物群落依生境梯度而分布，呈典型圆环状分布格局．沙层水分状况分析表明，同一沙丘不同部位的沙层含水量为丘顶低于丘坡地，且二者均低于丘间地．地统计学分析表明，无论是流动沙丘还是固定沙丘，从丘顶、丘坡到丘间地，沙层含水量的空间异质性呈规律性的变化，块金值与基台值之比逐渐减小，变程逐渐减小，分维数逐渐增大，表明随机部分引起的空间异质性逐渐降低，而由空间自相关部分引起的空间异质性逐渐增高．因此，沙丘不同部位沙层含水量及其空间异质性的有规律变化是科尔沁沙地中部部分梁窝状沙丘植物群落呈圆环状分布格局的一个重要原因．

Geostatistics analyzing to cause of formation of circle distribution of plant communities in Horqin Sandy Land

Investigation results in the present study showed that plant communities took typical concentric circles distribution patterns along habitat gradient from top,slope to interdune on a few large fixed dunes in middle part of Korqin Sandy Land.In order to explain this phenomenon,analysis of water content and its spatial heterogeneity in sand layers on different locations of dunes was conducted.In these dunes,water contents in sand layers of the tops were lower than those of the slopes; both of them were lower than those of the interdunes.According to the results of geostatistics analysis,whether shifting dune or fixed dune,spatial heterogeneity of water contents in sand layers took on regular changes,such as ratios between nugget and sill and ranges reduced gradually,fractal dimension increased gradually,the regular changes of these parameters indicated that random spatial heterogeneity reduced gradually,and autocorrelation spatial heterogeneity increased gradually from the top,the slope to the interdune.The regular changes of water contents in sand layers and their spatial heterogeneity of different locations of the dunes,thus,might be an important cause resulted in the formation of the concentric circles patterns of the plant communities on these fixed dunes.