塔河源荒漠河岸林灰胡杨与多枝柽柳种群空间格局与空间关联性

Spatial distribution and association between Populus pruinosa and Tamarix ramosissima population along Tarim river mainstream

【目的】研究种群的空间格局及关联性,有利于阐明群落空间格局形成和物种共存机制,对植被的恢复、生物多样性保护等具有重要意义。【方法】为探究荒漠河岸林优势种群的空间分布及关联性,2017年在塔里木河干流源头荒漠河岸林内设置1 hm2典型样地,应用点格局分析法(Ripley的K函数、L函数)对灰胡杨、柽柳种群不同径级的空间格局及空间关联性进行分析。【结果】1)塔里木荒漠河岸林群落结构简单,物种多样性低,仅有9科11属11种,灰胡杨种群呈中间大两头小的纺锤型,柽柳呈倒金字塔型,两者均为衰退型种群。2)灰胡杨与柽柳种群有极强的尺度依赖性,空间格局以聚集分布为主,随生长发育进程与空间尺度增大,聚集强度减弱,逐渐趋于随机分布。3)灰胡杨不同发育阶段的空间负关联性随径级增大,种内竞争逐渐增强。研究尺度内灰胡杨幼树、小树、中树与柽柳幼苗,柽柳成株与灰胡杨幼苗空间上呈相互排斥,影响群落更新与发展。4)灰胡杨死树与其幼龄、大龄个体及柽柳成株在空间上呈相互排斥,而与柽柳幼苗互不干扰。高盐生境与激烈的种间、种内竞争不利于荒漠河岸物种生长发育、更新及群落稳定。【结论】荒漠河岸林灰胡杨与柽柳种群空间格局受个体径级与空间尺度影响表现为聚集分布,随生长发育进程与空间尺度增大而趋于随机分布。空间关联性为负关联,且个体差异越大负关联性越强。分析空间格局及关联性得知,物种竞争、环境筛选是荒漠河岸林群落空间格局形成的主要动力。

【Objective】Studying the spatial pattern and its association of the population is beneficial to elucidate the formation of the community spatial pattern and the coexistence mechanism,which have important significance for vegetation restoration and biodiversity conservation.【Method】In order to explore the spatial distribution and association of dominant population in desert riparian forest,a typical plot of 1 hm2 was set up in the desert riparian forest at the source of the main stream of the Tarim river.The adjacent grid method was used to measure and map each individuals.The spatial point pattern analysis method(Ripley’s K function and L function)was used to analyze the spatial pattern and association of different size classes of P.prunison and T.ramosissima.【Result】1)Community structure of desert riparian forest was simple and the species diversity was low,there were only 11 species,belonging to 11 genera and 9 families.The P.prunison population has a spindle shape with the middle part large and the two ends small,and the T.ramosissima has an inverted pyramid type,and both populations would decline.2)The spatial patterns of P.prunison and T.ramosissima populations were mainly clumped distribution,and the aggregation intensity decreased with the increasing scale,and gradually from clumped to random distribution with development and scale increase.The negative spatial association of different developmental stages of P.prunison increased with size class,and the intra-specific competition increased gradually.3)In the 50 m scale range,all development stages of the P.prunison are mutually exclusive with the T.ramosissima seedlings and P.prunison seedlings with T.ramosissima except for the large tree stage,which inhibited the community regeneration and development.4)The dead trees of P.prunison had significantly negative correlation with its young trees,older trees,and T.ramosissima adults,but no correlation was found between dead trees of P.prunison and T.ramosissima seedling.The high salt habitats and intense interspecific and intra-specific competition are not conducive to the growth,regeneration and community stability of desert riparian species.【Conclusion】Competition and habitat filtering were the main driving forces for spatial pattern formation of desert riparian forest communities.