西双版纳热带季节雨林的树种组成和群落结构动态

Dynamics of tree species composition and community structure of a tropical seasonal rain forest in Xishuangbanna,Southwest China

研究了西双版纳热带季节雨林1 hm2(hectare)动态监测样地1993年与2007年之间树种组成和群落结构的变化。对样地中胸径≥5 cm的乔木进行了每木调查。目前其树种组成的热带分布科、属所占比例分别为91%和94%,具有较高比例的热带植物区系性质。在1993年与2007年两次调查之间,树种数量由145种增至179种,仅有1到2个个体的稀有树种所占比例从54%降为51.1%。从森林的垂直结构来看,A、B、C三层的个体死亡率分别为12.8%、12.9%和19.0%,各层树木的增长率分别为-8.5%、-1.4%和44.8%。与此相对应,C层小径级的树木所占比例有较大提高。虽然小径级的树木在种类和数量上比例增大,但个体数量和种类组成相对稳定的A、B层优势树种变化不大,维持了群落结构的稳定性。14 a间,群落中新增加的具有先锋性质的树种不超过5个。1993年时,A、B两层尚有先锋树种存在,2007年已经从A、B两层中退出。因此,从14 a间树种组成和群落结构的变化来看,虽然具有树木的死亡和增补,但其物种成分和群落结构的总体格局没有明显的变化,处于动态平衡过程中。

We studied the dynamics of tree species composition and community structure in an 1 hm^2 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.