亚热带次生常绿阔叶林主要乔木种群自然恢复15年来的变化

FIFTEEN-YEAR CHANGES OF TREE POPULATIONS IN THE SECONDARY SUBTROPICAL EVERGREEN BROAD-LEAVED FORESTS IN SOUTHWESTERN CHINA

在瓦屋山定位研究了中亚热带湿性常绿阔叶林次生群落 1 5a来各乔木种群组成及其重要值、密度、大小结构、高度结构和材积生产力等的动态变化。结果表明 :自然恢复过程中次生常绿阔叶林群落乔木层物种组成变化明显 ,有 1 1种从群落乔木层消失 ,也有 1 0种出现 ,乔木层树种多样性 (丰富度 )基本保持动态平衡和发展 ;优势种地位保持不变 ,但次优势种地位得以加强 ;群落结构变化较大 ,突出表现为种群密度、胸径和树高分布格局的变化和立体空间的分化 ,群落由单优或双优种向双优或多优势种发展 ,由单一乔木层向多层次立体结构发展 ,空间加厚 ,群落更复杂、稳定性增强。乔木种群平均高生长速度在 2 4～ 4 8cm·a-1,平均DBH生长率在 0 34～ 1 1 0cm·a-1,各种群生长速度差异明显 ,按生长速度可划分为适应性强的速生树种如细梗吴茱萸叶五加 ,华木荷 (平均DBH生长在 0 70cm·a-1以上 ) ,中等速度的小叶青冈、扁刺栲 (平均DBH生长在 0 4 0cm·a-1以上 ) ,慢生种如润楠 ,石栎 (平均DBH生长在 0 4cm·a-1以下 ) ;种群材积生产力高低不一 ,优势种扁刺栲种群材积生产力并不是一直增长 ,而是在后期出现下降 ;次优势种增长速度较快。1 997年 3固定样地材积量 2 1 8～ 2 35m3·hm-2 。

The present study was conducted in the secondary subtropical evergreen broad\|leaved forests at altitude 1*!650～1*!670*!m in Mt.Wawushan National Forest Park,southwestern China.In order to understand stand restoration dynamics,the stand structure in three permanent 004*!hm2 plots for 3～4*!times were recorded from 1982 to 1997 and expounded the changes in 15 years about tree composition,important value index,several diversity indices,structure and volume productivity of both communities and populations.The results were followed:11 tree species disappeared and about another 10 species entered into tree layer in the stand,keeping tree layer dynamic equilibrium and developing tree species diversity.The dominant species,Castanopsis platyacantha,assumed the superior status,but its important value(Ⅳ)was decreased.The position of secondary dominant species,Schima sinense and Lithocarpus hancei, are gradually enhanced with gradually increased Ⅳ.The changes of densities,DBH and height distribution of tree populations displayed that the secondary evergreen forest was developed from past single or double dominant tree species to double or three dominant trees,from single tree layer to multiple levels in vertical structure.And the resulting community becomes more complicated and more stable.The growth rates of average height and DBH of all main trees were 24～48*!cm·a -1 and 034～110*!cm·a -1,respectively.According to the differentiation of growth,the main trees could be divided into three growth groups of species:fast\|growing group including species of Schima sinense and Acanthopanax evodiaefolius var.gracills,slow\|growing group of Machilus pingii and Lithocarpus hancei, and the group in between of Castanopsis platyacantha and Cyclobalanopsis myrsinaefolia. Volume productivity of the dominant population increased firstly and then decreased,but the secondary tree population increased quickly all the time.Volume productivity of all tree population in 1997 was up to between 218*!m3·hm -2 and 235*!m3·hm -2,and the change of dominant population was a key for community productivity.The relations of DBH,height growth and volume productivity in various density of the main tree populations indicated that the densities was one of the most important factors influencing productivity of tree populations under common environment with the interactions among tree populations.It is suggested that there is no contradiction between tree species diversity conservation and high volume productivity in forest restoration process.