Nonrandom, diversifying processes are disproportionately strong in the smallest size classes of a tropical forest
Nonrandom, diversifying processes are disproportionately strong in the smallest size classes of a tropical forest
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DOI：
10.1073/pnas.1321892112
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发表时间：
2014-12-30
影响因子：
11.1
通讯作者：
Connell, Joseph H.
中科院分区：
文献类型：
--
作者：
Green, Peter T.;Harms, Kyle E.;Connell, Joseph H.
各种生态过程影响着自然群落的多样性和物种组成。这些过程中的大多数，无论是非生物的还是生物的，从出生到死亡都有差异地过滤个体，从而改变物种的相对丰度。非随机的结果可能会在整个个体发育过程中累积，或者产生它们的过程可能在某些阶段特别有影响力。热带森林生态学中一个长期存在的范式认为，成熟树木之间的相对丰富模式主要是由生命周期最早阶段的过程决定的。几项研究证实了过滤过程的某些阶段，但大树的寿命使得在没有长期人口统计数据的情况下不可能对大小类别进行严格的比较。在这里，我们使用世界上运行时间最长的，基于地块的森林动力学项目之一，比较非随机结果跨阶段类。我们考虑了1971年存活的186个物种的7，977个个体，并在42年至2013年的13次死亡率普查中进行了监测。非随机死亡率相对于物种身份更经常发生在较小的，而不是较大的大小类。此外，观察到的非随机死亡率在较小的大小类有多样化的影响，物种丰富度的幸存者是高达30%以上的预期在两个最小的大小类，但不大于预期在较大的大小类。这些结果突出了生命周期早期阶段在热带森林群落动态中的重要性。更一般地说，他们增加了一个积累的证据，早期阶段的非随机结果的重要性，在海洋和陆地环境中的社区结构。
A variety of ecological processes influence diversity and species composition in natural communities. Most of these processes, whether abiotic or biotic, differentially filter individuals from birth to death, thereby altering species' relative abundances. Nonrandom outcomes could accrue throughout ontogeny, or the processes that generate them could be particularly influential at certain stages. One long-standing paradigm in tropical forest ecology holds that patterns of relative abundance among mature trees are largely set by processes operating at the earliest life cycle stages. Several studies confirm filtering processes at some stages, but the longevity of large trees makes a rigorous comparison across size classes impossible without long-term demographic data. Here, we use one of the world's longest-running, plot-based forest dynamics projects to compare nonrandom outcomes across stage classes. We considered a cohort of 7,977 individuals in 186 species that were alive in 1971 and monitored in 13 mortality censuses over 42 y to 2013. Nonrandom mortality with respect to species identity occurred more often in the smaller rather than the larger size classes. Furthermore, observed nonrandom mortality in the smaller size classes had a diversifying influence; species richness of the survivors was up to 30% greater than expected in the two smallest size classes, but not greater than expected in the larger size classes. These results highlight the importance of early life cycle stages in tropical forest community dynamics. More generally, they add to an accumulating body of evidence for the importance of early-stage nonrandom outcomes to community structure in marine and terrestrial environments.