Dynamics of tree species composition and community structure of a tropical seasonal rain forest in Xishuangbanna,Southwest China
Dynamics of tree species composition and community structure of a tropical seasonal rain forest in Xishuangbanna,Southwest China
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作者：
Li Lu-xiang
对1993年至2007年两次普查西双版纳1 hm2热带季节性雨林样地的树种组成和群落结构动态进行了研究。样地内所有胸径≥5 cm的树木分别于1993年和2007年进行了测定和鉴定。2007年的调查结果显示，科属层面的热带亲缘性比例为分别为91%和94%，与14年前第一次普查的格局基本一致。样地树种数量从1993年的145种增加到2007年的179种，只有一、二个体的树种比例从1993年的54%下降到2007年的5个1.1%。A、B、C层树木死亡率分别为12.8%、12.9%和19.0%。相应地，A、B、C层树补充率分别为-8.5%、-1.4%和44.8%，同时小径级茎比例明显增加。但A、B层树木数和树种数保持相对稳定。近14年来，A、B层先锋树种为1993年2007年，尽管一些其他先锋树种（少于5个）被排除在外，综上所述，这片森林的物种组成和结构在过去14年中在树木砍伐和补充方面发生了变化，但森林的总体植被格局保持了动态平衡状态。
We studied the dynamics of tree species composition and community structure in an 1 hm2 tropical seasonal rain forest plot in Xishuangbanna between two censuses in 1993 and 2007.All the trees DBH(diameter at breast height) ≥ 5 cm in the plot were measured and identified in 1993 and 2007 respectively.The results of 2007 survey showed that the proportions of tropical affinity at the levels of family and genus were 91% and 94% respectively,which was generally consistent with the pattern of the first census conducted 14 years ago.The number of tree species in the plot increased from 145 in 1993 to 179 in 2007,and the proportion of tree species with only one or two individuals decreased from 54% in 1993 to 5 1.1% in 2007.The mortalities of trees in layers A,B and C were 12.8%,12.9% and 19.0%.Correspondingly,the rate of tree recruitment were-8.5%,-1.4% and 44.8% in layers A,B and C.Meanwhile the proportion of stems with small DBH classes increased significantly.However,the number of trees and the number of species in layers A and B kept relatively stable.Over the last 14 years,the pioneer tree species in layers A and B in 1993 were excluded,even though some other pioneer tree species(fewer than five) were recruited into the layer C in 2007.In conclusion,the species composition and structure of this forest were changed in terms of treefall and recruitment during the past 14 years,but the general vegetation pattern of the the forest was kept in a state of dynamic equilibrium.