Many theories have been proposed to explain the high diversity of plants in the tropics. However, we lack an understanding of the processes that drive plant diversity and community assembly at different spatial scales. Here, we applied beta-diversity partitioning to test how biotic and abiotic factors are associated with seedling beta-diversity in a tropical montane forest in southern Ecuador. We recorded seedling communities on 81 subplots in nine plots located at three elevations along a 2000 m elevational gradient. We measured biotic pressures (i.e. herbivory and fungal pathogen attacks) and environmental conditions (i.e. soil moisture and canopy closure) in all subplots and related them to species turnover and richness differences in seedling communities within and between elevations. We found that species turnover increased with differences in biotic dissimilarity within elevations, while differences in species richness within elevations increased with increasing environmental dissimilarity. Between elevations, species turnover increased with increasing environmental dissimilarity. Our findings show that species turnover and changes in species richness are related differently to abiotic and biotic factors, and that the importance of these factors for shaping seedling diversity is scale-dependent. Our study contributes to better understand the processes driving seedling beta-diversity and the assembly of plant communities in highly diverse tropical montane forests.

中文翻译：

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生物压力和环境异质性塑造了热带山地森林幼苗群落的 β 多样性

人们提出了许多理论来解释热带植物的高度多样性。然而，我们对在不同空间尺度上驱动植物多样性和群落组装的过程缺乏了解。在这里，我们应用 β 多样性划分来测试生物和非生物因素如何与厄瓜多尔南部热带山地森林中的幼苗 β 多样性相关联。我们记录了位于沿 2000 米海拔梯度的三个海拔高度的九个地块中的 81 个子地块上的幼苗群落。我们测量了所有子图中的生物压力（即食草动物和真菌病原体攻击）和环境条件（即土壤水分和树冠关闭），并将它们与海拔内和海拔之间的幼苗群落的物种更替和丰富度差异相关联。我们发现物种更替随着海拔内生物差异的增加而增加，而海拔内物种丰富度的差异随着环境差异的增加而增加。在海拔之间，物种更替随着环境差异的增加而增加。我们的研究结果表明，物种更替和物种丰富度的变化与非生物和生物因素的相关性不同，并且这些因素对塑造幼苗多样性的重要性具有规模依赖性。我们的研究有助于更好地了解在高度多样化的热带山地森林中推动幼苗 β 多样性和植物群落组装的过程。在海拔之间，物种更替随着环境差异的增加而增加。我们的研究结果表明，物种更替和物种丰富度的变化与非生物和生物因素的相关性不同，并且这些因素对塑造幼苗多样性的重要性具有规模依赖性。我们的研究有助于更好地了解在高度多样化的热带山地森林中推动幼苗 β 多样性和植物群落组装的过程。在海拔之间，物种更替随着环境差异的增加而增加。我们的研究结果表明，物种更替和物种丰富度的变化与非生物和生物因素的相关性不同，并且这些因素对塑造幼苗多样性的重要性具有规模依赖性。我们的研究有助于更好地了解在高度多样化的热带山地森林中推动幼苗 β 多样性和植物群落组装的过程。