西江中下游针阔混交林优势种群的结构及分布格局研究

以西江中下游的针阔混交林为研究对象，通过固定样地、每木调查和林下更新层调查法获得野外资料，采用径级代龄级的方法，研究主要优势树种的种群结构，以及应用方差／均值比、平均拥挤度指数、聚块指数、丛生指标、负二项式参数等5个指标分析其种群格局状况。结果表明不同优势种群的径级结构差异明显：马尾松和烟斗柯缺失或缺乏幼苗，为衰退型种群；福建青冈幼苗充足，中龄级立木占绝对优势，表现为增长型种群，但结构不稳定；鸭脚木幼苗数量丰富，径级分布呈倒J字型，为稳定的增长种群。种群的格局动态因树种和发育阶段而不同，表现为马尾松由均匀分布过渡到集群分布，福建青冈始终为群集分布，鸭脚木和烟斗柯则由幼苗的集群分布向成树阶段的随机分布转变，4个种群的格局动态呈现出聚集强度降低的扩散趋势。

Structure and Spatial Patterns of Dominant Populations in the Conifer and Broadleaf Mixed Forest in Middle-Lower Reaches of Xijiang River

This study was carried out in the conifer and broadleaf mixed forest in middle-lower reachers of Xijiang river with Pinus massoniana, Cyclobalanopsis chungii, Schefflera octophylla, and Lithocarpus corneus as the most important dominant species. Field data were obtained by tallying of permanent sample plot, complete enumeration tally scaling, and regeneration measuring. The floristic composition and community structure of dominant pop- ulations were examined by applying the age class substituting for size structure change. The distribution patterns of dominant populations were discussed on the basis of assembling intensity indexed, such as Variance/mean, negative binomial distribution, mean crowding, diffusion index and index of patchiness. The results showed that the age structures of the population of P. massoniana and L. corneus were spindle type and declining due to lack of seedlings, S. octophylla had a large reserve of seedings, showing a inverse J of population structure, and C. chungii both had a certain amount of seedlings and median trees, showing increase structure, but instabilization. As to the distribution pattern of dominant trees are different among species and various developmental stage. The spatial distribution patterns of P. massoniana were from uniform to clump, C. chungii was always clump, S. octophylla and L. corneus clump for saplings, random for adult trees and big trees. Generally speaking, with the progressive succession, the aggregation intensity was decrease.