风沙侵袭影响下绿洲边缘植物群落点格局分析

以塔克拉玛干沙漠南缘策勒绿洲为研究区，运用Ripley’s K(t)函数点格局分析，研究风沙侵袭影响下植物群落结构和点分布格局的变化。风沙侵袭对植物组成种类无影响，均由骆驼刺、柽柳和花花柴组成，但自内侧向外围随着风沙侵袭强度加大，植株密度和盖度会明显降低，组成比例上从以骆驼刺为主向各种群均匀发展，并且骆驼刺的树冠面积随之显著增加，柽柳和花花柴的树冠面积显著减小。种群分布格局具有明显的尺度依赖性，3个种群在30 m的空间尺度上均以聚集分布为主，随风沙掩埋强度增加,3个种群分布类型从聚集变为随机，且聚集分布的尺度范围及聚集峰值所在尺度逐渐减小。研究区内各种群间以负关联为主，随风沙侵袭强度加大，各种群间的负关联程度及尺度范围均呈减弱趋势，最终变为不关联或部分尺度上较弱负关联。风沙掩埋的直接干扰和植物适应性及种间关联关系是种群空间格局变化的主要原因，强烈的风沙掩埋抑制了植物的生长和繁殖，促使群落退化，所以绿洲边缘的流沙深入区是过渡带建设及保护的重点区域。

Analysis on Spatial Point Pattern of Plant Communities in the Marginal Zone of Oasis under Wind-blown Sand

Spatial point pattern for plant species in the west Qira oasis-desert ecotone under wind-blown sand was analyzed in this paper.Ripley’s K(t) function was used to analyze the plant community structure,spatial point pattern of plant species and interspecies relationship.The results are as follows:(1) There was no impact of wind-blown sand on composition of plant species,all the plant communities were consisted of Alhagi sparsifolia Shap.,Tamarix ramosissima Ledeb.and Karelinia caspia(Pall.) Less.However,the plant density and coverage were reduced with the increase of wind-blown sand intensity;(2) At a 30-m spatial scale,the point distribution of these three plant communities was in an aggregative pattern,and their plant density and coverage were obviously decreased with the increase of wind-blown sand intensity.With the increase of sand burial degree,point pattern of the three plant communities was changed from aggregation to random pattern,and the scale range of aggregate distribution was gradually reduced;(3) Negative correlation among the plant communities was dominant,and it was in a decrease trend with the increase of wind-blown sand intensity.In addition,the causes resulting in the change of spatial distribution of plant communities were the direct disturbance of sand burial,plant adaptability and correlation among the plant communities.The serious sand burial restricted the plant propagation and growth and resulted in the degeneration of the plant communities.Therefore,the oasis-desert marginal zone suffering from severe wind-blown sand is the main conserving area for the oasis safety.