Dispersal Limitation: Does it Limit the Distribution and Abundance of Pioneers in a Neotropical Forest?

9509026哈贝尔对巴拿马巴罗科罗拉多岛(BCI)上一块50公顷的永久新热带森林地块进行的长期研究表明，许多潜在的合适林隙地点缺乏个别先锋物种。虽然先锋物种预计不会在合适地点稀少的森林中常见，但它们似乎比偶然预期的要少。这项研究将检验BCI森林中先锋物种的分布和丰度主要受扩散限制而不是萌发和建立限制的假说。所有超过25平方米的树冠空隙将被绘制在50公顷的地块上。将在林隙中进行一系列田间试验，以确定林隙和封闭林的环境条件是否会影响种子的萌发和建立。种子落下也将被监测，作为传播限制的一种衡量标准。扩散限制的潜在重要性远远超出了对分布和丰度的解释。最近的理论工作表明，强大的扩散限制可以通过极大地减缓竞争排斥来促进树木物种丰富度。此外，这项工作将为维持由于森林砍伐而迅速消失的新热带森林群落物种多样性的机制提供重要的见解。

9509026 HUBBELL A long-term study of a 50 ha permanent plot of neotropical forest on Barro Colorado Island (BCI) Panama, has revealed that individual pioneer species are absent from many potentially suitable gap sites. Although pioneer species are not expected to be common in a forest where suitable sites are rare, they appear to be less common than would be expected by chance. This research will test the hypothesis that distribution and abundance of pioneer species in the BCI forest are primarily controlled by dispersal limitation rather than by germination and establishment limitation. All canopy gaps greater than 25 m2 will be mapped on the 50 ha plot. A series of field experiments in gaps will be conducted to determine if the environmental conditions in gaps and closed forest affect germination and establishment. Seed fall will also be monitored as a measure of dispersal limitation. The potential importance of dispersal limitation goes far beyond finding explanations for distribution and abundance. Recent theoretical work has shown that strong dispersal limitation can promote tree species richness by greatly slowing competitive exclusion. In addition, this work will provide important insights into mechanisms that maintain species diversity in neotropical forest communities that are rapidly disappearing due to deforestation.