准噶尔盆地南缘洪积扇无叶假木贼种群空间点格局

Spatial Point Patters of Anabasis aphylla Populations in the Proluvial Fan of South Junggar Basin

以准噶尔盆地南缘洪积扇斜坡、缓坡和平缓坡3个典型地段上的无叶假木贼种群为研究对象,运用点格局方法研究不同生境、不同发育阶段的种群空间分布格局及其空间关联性,探讨无叶假木贼空间格局形成和种群维持与动态机制。结果表明:在3个生境中无叶假木贼种群均表现出聚集分布,其中斜坡和平缓坡在50 m的范围内聚集;各发育阶段在小尺度上的聚集分布特征都比较明显,随尺度增加种群的聚集强度减弱,其中缓坡各发育阶段均表现出偏均匀分布的趋势;幼苗具有明显的聚集分布和最大的聚集强度,从幼苗到成年植株则表现出聚集强度降低;各发育阶段之间在小尺度上强烈正关联,在大尺度上幼苗和幼株、成年植株之间表现出负关联或无关联,而幼株和成年植株间表现出正关联或无关联,其中缓坡各发育阶段之间在大尺度上的空间关联均趋于负关联。

Study on spatial patterns of species populations can provide many important clues about the underlying processes of these patterns formation. Natural Anabasis aphylla populations are representative vegetation types of the proluvial fan in south Junggar basin. Three sample plots were respectively established on steep slope,gentle slope and flat slope to analyze and compare spatial patterns of A. aphylla populations. The pair correlation function and univariate statistics of the point patterns were used to analyze spatial distribution of different developmental stages and different habitats,while bivariate statistics was used to analyze spatial associations of different developmental stages in each plot. The change of population spatial pattern and association among different development stages was compared to explore inherent formation mechanism of spatial patterns. The results showed that： A. aphylla populations were all aggregated distributions in the three habitats,and on steep slope and flat slope A. aphylla individuals were all aggregated at 50 m scales; Different types of A. aphylla populations on the three slopes showed significantly aggregated distributions at relatively smaller scales and the degree of aggregation decreased with increasing spatial scales,and it tended to uniform distributions at larger scales in the gentle slope; Seedlings had more obviously aggregated distribution and stronger aggregated intensity than the larger individuals; At relatively smaller scales,there was a significantly positive association among different developmental stages in the three slopes. However,at larger scales either negative or uncorrelated association was found between seedling and the other two stages,whereas positive or uncorrelated association was found between juvenile and mature plant. Among them pattern association among different developmental stages tended to negative association in the gentle slope.