四川省喇叭河自然保护区珙桐种群结构与分布格局

采用相邻格子法，研究了四川省喇叭河自然保护区珙桐Davidia involucrata种群径级结构和高度结构，编制了种群的静态生命表，绘制了种群存活曲线，并用4个生存函数进行种群的生存分析：运用方差／均值比的t检验法、负二项参数、平均拥挤度和聚块性指数等方法，分析了珙桐种群的空间分布格局及其动态。结果表明：珙桐种群的径级结构和高度结构都近似于倒金字塔型，幼苗严重不足，种群有衰退的趋势：其更新是以无性繁殖为主：珙桐种群有前期生长不稳定，中期稳定，后期衰退的特点；其存活曲线属于DeevevⅢ曲线；种群分布格局整体上呈集群分布，从幼苗到大树，其集群程度减弱：基株种群和分株种群在不同取样尺度下其聚集强度有所变化。珙桐种群结构和分布格局可能受其繁殖特性影响。

Population structure and distribution pattern of Davidia involucrate at Labahe Nature Reserve of Sichuan Province

Davidia involucrata is a relic species of paleotropical kingdom in Tertiary period, belonging to Davidiaceae with a single genus. In recent years, the increase of regional developing projects has led to a sharp decrease of this species in natural population. The population characteristics of D. involucrata were discussed here, and the dynamic changes of its population were analyzed systematically, in order to provide basic data for further study, and tO probe into conservation policy on this species. Quadrates with a contiguous grid were used to collect field data of D. involucrata at Labahe Nature Reserve of Sichuan Province. Size and height Class structures were established; a time-specific life table was produced; and survivorship curves were drawn. A t-test of the variance/mean （v/m） ratio, the negative binomial parameter, the mean crowding index, and the patchiness index were used to analyze the distribution pattern and dynamics. The results showed： （1） the population structure of the D. involucrata population was a inverse-pyramid type. （2）The structure of D. involucrata population was declining due to a lack of seedlings. （3） Also, the main regeneration mode of D. involucrata was asexual reproduction. （4）From early age to old age, the population was first characterized as unstable, then stable, and finally degraded with a type m Deevey Curve describing survival. （5）Generally, the D. involucrata population was clumpy, and the aggregation intensity tended to decrease from the sapling to the mature tree stage, the aggregation intensity also changed with block sizes. The results above indicated that the interaction between biological and ecological properties mainly decided the spatial population structure and distribution pattern.