清新和阳山县圆叶乌桕群落物种多样性和优势种群动态探讨

为了解亚热带地区石灰岩山地圆叶乌桕(Triadica rotundifolia)群落的变化规律，应用样方调查法，对广东省清新县和阳山县两片石灰岩山区圆叶乌桕群落的物种多样性及其种群动态进行了研究。结果表明，在两个面积为2400 m2的样方中，共有维管植物140种，隶属于65科118属。群落均以大戟科、茜草科、芸香科、桑科和木犀科为优势科；其种子植物属的分布区类型以热带分布型为主，占总属数的79.6%，温带分布型属占18.3%。除草本层均匀度外，清新群落的各层丰富度、多样性指数和均匀度指数均比阳山群落的高。清新的圆叶乌桕种群缺乏小苗，为不稳定种群; 而阳山的圆叶乌桕种群相对年轻，为稳定种群。随着群落的演替发展，群落中圆叶乌桕的优势地位终将被其它耐荫型树种所取代。

Species Diversity and Dominate Population Dynamics of Triadica rotundifolia Community in Qingxin and Yangshan Counties, Guangdong

Triadica rotundifolia is a common species of secondary forest in limestone region. In order to understand the dynamic changes of T. rotundifolia community in limestone region, the species diversity and population structure of T. rotundifolia community in Qingxin and Yangshan Counties, Guangdong Province, were studied by plot method. The results showed that there were 140 vascular plants in two plots with area of 2400 m2, belonging to 65 families and 118 genera. The dominant families were Euphorbiaceae, Rubiaceae, Rutaceae, Moraceae and Oleaceae. Among them, the tropical distribution elements at genus level were dominate accounting for 79.6%, and then 18.3% for temperate distribution elements. The species richness, species diversity and evenness of T. rotundifolia community in Qingxin were higher than those in Yangshan, except for evenness of herbal layer. T. rotundifolia population in Qingxin is unstable owing to lack seedlings and small individuals, while T. rotundifolia population in Yangshan is young comparatively with abundant small trees. With succession development of the community, the dominance of T. rotundifolia in community would be replaced by other shade-tolerant species.