Stand dynamics of a tropical rain forest and its responses to climate changes during the last two decades in Sumatara

通过对苏门答腊中部热带雨林近几十年的长期野外观察，揭示了该地区热带雨林的植物区系特征和林分动态。在西苏门答腊省巴里桑山脉的西山坡上，可观察到40种壳斗科植物。特别是壳斗科植物多样性高、断面积优势度高，是该地区山地森林植被的显著特征。山地雨林林分断面积的增长率在近10年比前10年有所下降。这是由于在过去的十年里，一棵大树的生长率较低，死亡率较高。这一现象在该地区其他林分中也可以同步观察到。讨论了异常干旱天气频繁发生对这些林木的影响。通过对林窗水平分布格局的研究，可以明确林窗水平分布格局的时间变化趋势。根据这一观测结果，我们可以估算出山地雨林林冠的周转时间为45年。最近冠层树木的高死亡率导致增加优势的树种，木材更软，更高的增长率，在成熟和次生林也。

We could show floristic traits and stand dynamics of a tropical rain forest in Central Sumatra by basing on long-term field observation over the last decades. Forty species of Fagaceae could be observed in west faced slopes of the Barisan Mountains in West Sumatra Province. High species diversity and high dominance in basal area of Fagaceae over Dipterocarpaceae were notable characteristics in vegetation of a hill forest in this area particularly. We could discuss the dominance to be caused not only by natural factors such as climate, soils and geographical factors but also by recent human impacts.The growth rates of basal area of a hill rain forest stand decreased at the last ten years in comparison with one during the former ten years. This was resulted from lower growth rates and higher mortality of a big trees in the last ten years. This phenomenon could be observed at other forest stands in this area synchronously. We discuss impacts of frequent occurrence of abnormal dry weather on these forest trees. We could make clear the time trends of horizontal distribution pattern of canopy-gaps. Basing on this observation, we could estimate the turnover time of forest canopy to be 45 years in a hill rain forest. Recent high mortality of canopy trees caused to increase dominance of tree species with softer wood and higher growth rates in a mature and secondary forest also.