云南德宏州西南桦天然林物种组成及多样性研究

Species Composition and Diversity of Betula alnoides Natural Forests at Dehong Prefecture,Yunnan Province

[目的]研究西南桦天然林物种组成和多样性特征,为西南桦天然林生物多样性保护及西南桦人工林近自然经营提供科学依据。[方法]在云南省德宏州瑞丽派罗山1958年皆伐后形成的天然次生林(PLS)和芒市桦桃岭刀耕火种1967年丢荒地形成的天然次生林(HTL)内分别设置总面积为10000 m^(2)和5000 m^(2)的样地开展物种多样性调查。运用Simpson优势度指数、Shannon-Wiener多样性指数和Pielou均匀度指数,分析乔木层、灌木层和草本层物种组成和多样性,并对林分整体及重要值>5.00%的乔木层主要树种绘制径级分布图。[结果]PLS林分内无绝对优势种,树种润楠的重要值最大(14.76%),其次为西南桦(9.55%);HTL林分,树种西南桦的重要值最大(26.47%),在林分内占据绝对优势。PLS林分各林层物种丰富度(草本层除外)、Simpson优势度指数、Shannon-Wiener多样性指数和Pielou均匀度指数均高于HTL,但物种优势度低于HTL,物种分布更均匀。不同林层间Simpson优势度指数、Shannon-Wiener多样性指数和Pielou均匀度指数均以灌木层最高,而物种丰富度则乔木层最高。2种林分的径级结构均呈倒J形分布,重要值>5.00%的主要树种除西南桦分布在中大径级外,均集中分布在中小径级。[结论]PLS林分较HTL更接近演替后期,二者均属于稳定的群落类型。研究结果为西南桦天然林保护以及人工纯林近自然化改造和经营提供理论依据和技术参考。

[Objective]Species composition and diversity characteristics of Betula alnoides natural forests were investigated to provide evidences for biodiversity conservation of B.alnoides natural forests as well as close-to-nature management of B.alnoides plantation.[Method]Plots with total areas of 10,000 m^(2) and 5,000 m^(2) were set up to investigate the species diversity in the forests at Pailuo Mountain,Ruili(PLS)and Huatao Ridge,Mangshi(HTL),Dehong Prefecture,Yunnan Province,respectively.The former stand was naturally regenerated after clear-cutting in 1958,while the other was naturally regenerated on abandoned land after slash-and burn cultivation in 1967.The Simpson index,Shannon-Wiener index and Pielou evenness index were used to analyze the species composition and diversity of tree,shrub and herb layers.The diameter class distributions were analyzed for the whole stand and the main tree species with importance value above 5.00%.[Result]There was no absolute dominant species in PLS stand,and the most important species in PLS was Machilus pingii(14.76%)and B.alnoides(9.55%).The species with the largest important value in HTL stands was B.alnoides(26.47%),which was absolutely dominant in the stand.The species richness(except herb layer),Simpson dominance index,Shannon-Wiener diversity index and Pielou evenness index in each layer of PLS stand were higher than those of HTL stands,but the species dominance was lower in PLS stands.The species distribution was more evenly distributed in PLS stand.Simpson dominance index,Shannon-Wiener diversity index and Pielou evenness index were the highest in shrub layer,while the highest species richness was observed in tree layer.The diameter-class structures of both the stands were inverted J-shaped,and the main tree species with important value above 5.00%were concentrated in the middle and small sized classes except B.alnoides which was in large and middle-sized classes.[Conclusion]The PLS stand is much closer to late succession stage than HTL stand,and they all belong to stable coenotypes.These findings could provide evidences and technical support for conservation of B.alnoides natural forest and close-to-nature transformation and management of B.alnoides pure plantation.