Role and Status of Pioneer Species in the Dynamics of the Mixed Dipterocarp Forests

龙脑果混交林是亚洲热带野生自然的象征，其特点是物种多样性大，建筑高大，森林内的地方差异大。世界上热带雨林研究的主要专业人员通过建立50公顷的大型生态样地，认识到长期进行森林生态研究的必要性，以了解森林的真实面貌。本研究通过以下活动为沙捞越龙脑果混交林的长期和大规模生态研究做准备：1)建立50公顷样地，2)制图、森林调查和DBHs大于1.0 cm的活树标本收集，3)物种多样性、森林结构和群落动态分析，4)先锋树种生活策略的比较，5)先锋树种在混交林动态中的作用和地位的综合和生态学讨论。为了准确划定50公顷样地，我们使用了电子测速仪。在森林调查中，样地闭合误差为1.0m。该地块地形非常复杂，包括各种植物栖息地。10公顷的森林调查是在两年的研究活动中完成的。先锋树种寿命短，生长快，更新依赖树冠空隙，叶片中没有有效的抗草食物质，采用有毒种皮物质种子库策略。

Mixed dipterocarp forest is a symbol of wild nature in Asian tropics and is characterized by the great species diversity, tall architecture, and big local variations within the forest. Major professionals in tropical forest researches in the world become aware of the necessity of the long-term ecological research of the forests by establishing the large ecological plots with sizes such as 50 ha, for understanding the forests as they really are. This research project was carried out as a preparation for the long-term and large scale ecological research of the mixed dipterocarp forest in Sarawak through the following activities : 1) the establishment of the 50 ha plot, 2) mapping, forest inventory, and herbarium collection of living trees with DBHs over 1.0 cm, 3) the analysis of species diversity, forest structure, and community dynamics, 4) the comparison of life strategies among pioneer tree species, and 5) synthetic and ecological discussions about the role and status of pioneer species in the dynamics of mixed dipterocarp forest.To demarcate the 50 ha plot with a reliable accuracy, we used an electronic tacheometer. The closure error of the plot was 1.0 m in forest survey. The plot was very complex in topography and included various habitats for plants. The 10 ha forest inventory was done during two year research activities. Pioneer species is short lived and grew faster than climax species, depended their regeneration on canopy gaps, had not effective anti-herbivory substances in leaves, and adopted seed bank strategy using toxic seed coat substances.