西双版纳山地雨林乔木层树种20年动态研究

热带雨林中乔木层树种对群落的结构和功能起着决定性的作用,监测乔木树种的动态,能更好的了解群落的演替。基于西双版纳地区5块共1.25 hm2山地雨林固定样地20年的监测资料,从物种组成、多样性指数、个体数量、主要树种组成和径级结构等方面分析树种动态。研究对象为近成熟的山地雨林,1992—1994年初测时样地中记录到乔木层树种215种,隶属于61科128属;到2012年,乔木层树种增加到239种,隶属于62科148属。分析表明,20年来样地中乔木层树种在科、属、种三级组成水平上均呈缓慢增加趋势,增加率分别为1.64%、15.63%、11.16%。退出乔木层和新进入乔木层的树种主要是偶见种。20年来,样地乔木层总株数从1464株增加至1478株,累计死亡620株,总死亡率29.55%,年均死亡率1.48%;累计进界634株,总进界率30.22%,年均进界率1.51%;群落的多样性指数在小幅度波动中略有增加,Simpson指数、Shannon-Wiener指数和Pielou均匀度指数的增加率分别为0.28%、2.69%、0.55%;乔木层的径级组成未有明显变化,不同径级的死亡和进阶基本处于持平状态。

Study on tree layer dynamic in Xishuangbanna montane rain forest based on 20 years' monitoring

Based on 20 years'' monitoring in montane rain forest plots (1.25hm² within 5 blocks) in Xishuangbanna, we analyzed the dynamics of tree layer in terms of species composition, diversity index, changes of individual tree numbers, changes of dominant tree species, and diameter distribution. The results showed that in 20 years, the tree species numbers were increased from 215 (in 61 families and 128 genera) to 239 (in 62 families and 148 genera). The numbers of families, genera and species were slowly increased at the rates of 1.64%, 15.63% and 11.16%. Those entering into or withdrawing from the tree layer belonged to accidental species with less individuals. The total individual numbers of trees were increased from 1464 to 1478 while 620 were died with a mortality rate at 29.55%, the average annual mortality rate at 1.48%. Meanwhile, 634 trees entered into the tree layer and the total in growth rate was 30.22%, the average annual growth rate at 1.51%. The diversity index showed a slight fluctuation, with increasing rates of Simpson index, Shannon-Wiener index and Pielou''s index at 0.28%, 2.69% and 0.55%, respectively. The death and advanced of different diameter classes were basically at flat state.