Tropical Rain Forest Biodiversity Analyzed by a Large Research Plot

利用1993年在马来西亚沙捞越兰比尔国家公园建立的一块面积为52公顷的大型研究样地，对热带雨林的物种丰富度进行了分析。本研究的问卷调查主要是对两种不同的假设--平衡生态位假说和非平衡假说--解释热带雨林生物多样性工作机制的有效性进行检验。通过将整个样地面积划分为1300、20m×20m林分，计算了每1300个林分的4个地形变量和5个森林结构变量。地形变量表明，地块的陡峭、陡峭起伏和复杂的一分为二的地形。森林结构变量也反映了一个巨大而复杂的森林层数叠加结构。地形变量和结构变量高度相关，表明森林结构相对于地形是可预测的。在5个林分结构变量中，20m×20m林分的平均单层胸径随林分密度的增加而减小，表现出对单株生长的密度依赖性。样地的物种总数为1175种，远远超过马来西亚西部的Pasoh(820种/50公顷)和巴拿马的BCI(306种/50公顷)。一些优势种的空间格局也与地形变量高度相关。所有这些结果表明，兰比尔热带雨林庞大而复杂的结构发生了可预测的变化，似乎有利于平衡假说作为热带生物多样性的一种工作机制。通过对叶片同工酶图谱的分析，揭示了基因漂移对丰富的热带生物多样性的重要性。

The species richness of a tropical rain forest was analyzed by using a large-scale research plot, which has a size of 52 ha and was established at the Lambir National Park, Sarawak, Malaysia in 1993. Questionnaires of the present study are mainly concerned with the tests of availability of two contrasting hypotheses, equilibrium hyporthesis (niche theory) and non-equilibrium hypothesis, for the explanations of working mechanisms of the biodiversity of tropical rain forest. By dividing the whole plot area into 1300,20mx20m stands, four topographic and five forest-structural variables were calculated for each of 1300 stands. The topographic variables suggested the steeply sloped, sharply undulating, and complexly bisected topography of the plot. The forest structural variables also suggested a huge and complex structure with superimposed forest layrs. Both topographic and structural variables were highly correlative, suggesting a predictability of forest structure with respect to topography. Out of the five forest structural variables, mean dbh per forest layr in a 20mx20m stand decreased with and increase of tree density per forest layr, showing a density dependency of individual tree growth. The total number of species in the plot was 1175, which was far greater than those at Pasoh (820 spp/50ha) in west Malaysia and BCI (306) spp/50ha) in Panama. The spatial patterns of some dominant species were also highly correlative with topographic variables. All these results suggested the predictable change of the huge and complex architecture of the rain forest at Lambir and seemed to be favored by the equilibrium hypothesis as a working mechanism of tropical biodiversity. The genetic diversity was studied by analyzing isozyme patterns in leaves and implied the importance of gene drifts for producing the rich tropical biodiversity.