Large scale disturbances are known to impact the alpha and beta diversity of communities. However, whether these disturbances increase or decrease diversity is often debated. The goal of this study was to quantify how the diversity of the seedling community was impacted within and across elevation in the El Yunque forest of Puerto Rico following a major hurricane. We tested two alternative hypotheses, that hurricanes are relatively more homogenizing or non-homogenizing forces, by quantifying changes in alpha and beta diversity of the seedling community post-hurricane. This approach highlights whether ecological mechanisms associated with community homogenization (species-specific survival, successional processes, and reduced environmental heterogeneity) or non-homogenization (resource release, increased environmental heterogeneity, and stochastic processes) structure the seedling community post-hurricane. We compared species richness, Fisher’s α, Simpson’s evenness, and multiple aspects of beta diversity within and among 25 seedling plots at 300, 400, and 500 m in elevation pre- and post-hurricane. We found that species richness, diversity, and evenness were higher post-hurricane, but abundance decreased 19%. Increases in alpha diversity suggest that hurricanes are non-homogenizing forces potentially linked with increases in light levels promoting colonization of early-successional species and resource release for other light-demanding species. The beta diversity results varied in their support for hurricanes as homogenizing depending upon the spatial scale of the analysis, potentially due to a combination of mechanisms including species-specific survival and site-specific differences. To fully grasp how the seedling community responds and recovers from disturbance, additional long-term monitoring will be needed to allow insight into the future of species richness, abundance, and spatial and temporal changes in community composition.

中文翻译：

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一场主要飓风对热带森林幼苗群落中 alpha 和 beta 多样性的特定地点影响

众所周知，大规模干扰会影响社区的 alpha 和 beta 多样性。然而，这些干扰是增加还是减少多样性经常被争论。本研究的目的是量化波多黎各 El Yunque 森林在一场大飓风之后，幼苗群落的多样性如何在海拔内和海拔之间受到影响。我们通过量化飓风后幼苗群落的 alpha 和 beta 多样性的变化，测试了两种替代假设，即飓风是相对更均匀或非均匀的力量。这种方法强调了与群落同质化（特定物种的生存、演替过程和减少的环境异质性）或非同质化（资源释放、环境异质性增加、和随机过程）构建飓风后的幼苗群落。我们比较了飓风前后海拔 300、400 和 500 m 的 25 个苗圃内和之间的物种丰富度、Fisher α、辛普森均匀度和 beta 多样性的多个方面。我们发现飓风后物种丰富度、多样性和均匀度更高，但丰度下降了 19%。阿尔法多样性的增加表明，飓风是非均质化的力量，可能与光照水平的增加有关，促进早期物种的定植和其他需要光照的物种的资源释放。根据分析的空间尺度，β多样性结果对飓风的支持因同质化而异，可能是由于多种机制的组合，包括物种特异性存活和位点特异性差异。为了充分掌握幼苗群落如何响应和从干扰中恢复，需要进行额外的长期监测，以了解未来物种丰富度、丰度以及群落组成的时空变化。