Dynamics of a Neotropical Forest: The First Decade

尽管最近取得了进展，但物种丰富的热带森林的组成、结构和动态以及热带树木的人口统计学在很大程度上仍然不为人知。对这种热带森林的长期研究很少有足够的种群样本来分析个别树种的生活史，或进行社区层面的分析。这项研究将监测巴拿马巴罗科罗拉多岛50公顷永久林地中306种树木、树苗和灌木的25万多个单独标记、绘制和识别的树木、树苗和灌木的命运(生长、存活和再繁殖)。对情节的两次普查已经完成，第一次是在1980年至1982年之间，第二次是在1985年。由于若干原因，1990年的重新人口普查特别重要。在第一次人口普查期间，巴拿马中部发生了60多年来最严重的干旱，导致地块中的许多树种严重死亡，以及相对物种丰度的变化。在这次人口普查期间，没有发生类似的干旱。因此，有可能评估一次重大气候事件对树木死亡、生长和恢复的长期模式的社区水平影响。重新普查还将揭示每个物种的种群变化方向在过去十年中是否保持一致。它还将改进对树木生长和存活措施的分析，因为每棵树的当前表现不仅取决于其当前的当地生物和物理环境，而且还取决于其过去的表现和最近的环境历史。第一次，可以测试单个树木的生长率在多大程度上是时间上的自相关。根据一种假设，只有生长最快的个体才能存活下来，到达树冠。如果这是真的，那么冠层成虫可能比根据种群平均和随机大小特定增长率--通常的预测方法--估计的年龄要年轻得多。最后，但并非最不重要的是，重新普查的结果是必要的，因为目前的地块数据被相当多的科学家使用，不再准确。根据初步的茎计数，据估计，该地块直径超过1厘米的植物已经经历了大约10%-12%的总周转率。

In spite of recent progress, the composition, structure and dynamics of species-rich tropical forests, and the demography of tropical trees, remain largely unknown. Few long-term studies of such tropical forests exist that have population samples adequate for life history analyses of individual tree species, or for community-level analyses. This research will monitor the fate (growth, survival, and recuitement) of over a quarter of a million individuallly tagged, mapped, and identified trees, saplings, and shrubs of 306 species in a 50 ha permanent forest plot on Barro Colorado Island, Panama. Two censuses of the plot have been completed, the first between 1980 and 1982, and the second in 1985. This 1990 recensus is particularly important for a number of reasons. During the first census interval, the worst drought in more than 60 years occurred in central Panama, causing heavy mortality in many tree species in the plot as well as shifts in relative species abundance. No comparable drought has occurred during this census interval. Thus it will be possible to assess the community-level effects of a major episodic climatic event on longer-term patterns of tree mortality, growth, and recuitment. The recensus will also reveal whether the direction of population change for each species has remained consistent over the past decade. It will also enable an improved analyses of tree growth and survival measures current performance of each tree as a function of not only of its current local biotic and physical environment but also as a function of its past performance and recent environmental history. For the first time, the extent to which individual tree growth rates are temporally autocorrelated can be tested. According to one hypothesis, only the fastest growing individuals survive to reach the canopy. If this is true, then canopy adults may be much younger than ages estimated from averaged and randomized size- specific growth rates in the population--the usual projection metnods. Finally, but not least, the recensus results are needed because the present plot data, which are used by a sizeable number of scientists, are no longer accurate. Based on preliminary stem counts, it is estimated that the plot has already experienced about 10-12% total turnover in plants with diameters greater than one centimeter.