沱江源森林群落生物多样性垂直格局研究

在野外样带调查的基础上，分析了沱江源头九顶山植被生物多样性随海拔而变化的规律，并简要分析了植被生物多样性垂直格局的影响因子。从河谷到林线，乔木占据群落上层，其郁闭度对林下灌草层群落发育影响很大，生物多样性体现出乔木层与灌草层的相互关系：乔木盖度大的群落其灌木和草本层稀疏，而盖度小的次生林和林线上的高海拔区域灌木和草本种类与个体都迅速增加。多样性指数Hill指数及N1、N2指数变化规律基本相似：林线以下乔木层多样性指数最高，灌木层次之，草本层多样性指数最小，尤其在中度海拔体现明显，海拔3 500 m以上，草本多样性指数最高，灌木次之，而乔木已退出竞争。

VERTICAL PATTERN OF BIODIVERSITY IN FOREST COMMUNITY IN THE SOURCE OF TUOJIANG RIVER

In a study on the vegetation in Jiuding Mountain,the source of Tuojiang River,we analysed the law between species diversity and the altitude and identified the factors influencing the vertical distribution pattern of vegetation and biodiversity.In the east of Jiuding mountain,arbors dominated the upper layer of the community,and their shade has a significant effect on shrubs and grasses underneath from the valley to the forest borderline.In communities with a higher coverage of arbors,shrubs and grasses are sparsely distributed;in secondary forests with lower coverage and areas of higher altitude above the forest borderline,species and quantities of shrubs and grasses increase to a large extent.Similar change was found in Hill index,N_1 and N_2 indices: below the forest borderline,the value of diversity index decreases in the order of arbor>grass>shrub.This becomes much more significant at the altitude of more than 3 500 m,where the diversity index of grasses is the highest,second to it is shrub,while arbors no longer exist.