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Linking patterns and processes of tree community assembly across spatial scales in tropical montane forests
Ecology ( IF 4.8 ) Pub Date : 2020-06-08 , DOI: 10.1002/ecy.3058
Guillermo Bañares-de-Dios 1 , Manuel J Macía 2, 3 , Íñigo Granzow-de la Cerda 1 , Itziar Arnelas 4 , Gabriel Martins de Carvalho 1 , Carlos I Espinosa 5 , Norma Salinas 6, 7 , Nathan G Swenson 8 , Luis Cayuela 1
Affiliation  

Many studies have tried to assess the role of both deterministic and stochastic processes in community assembly, yet a lack of consensus exists on which processes are more prevalent and at which spatial scales they operate. To shed light on this issue, we tested two non-mutually exclusive, scale-dependent hypotheses: 1) that competitive exclusion dominates at small spatial scales; and 2) environmental filtering does so at larger ones. To accomplish this, we studied the functional patterns of tropical montane forest communities along two elevational gradients, in Ecuador and Peru, using floristic and functional data from 60 plots of 0.1 ha. We found no evidence of either functional overdispersion or clustering at small spatial scales, but we did find functional clustering at larger ones. The observed pattern of clustering, consistent with an environmental filtering process, was more evident when maximizing the environmental differences among any pair of plots. To strengthen the link between the observed community functional pattern and the underlying process of environmental filtering, we explored differences in the climatic preferences of the most abundant species found at lower and higher elevations and examined whether their abundances shifted along the elevation gradient. We found: 1) that greater community functional differences (observed between lower and upper tropical montane forest assemblies) were mostly the result of strong climatic preferences, maintained across the Neotropics; and 2) that the abundances of such species shifted along the elevational gradient. Our findings support the conclusion that at large spatial scales environmental filtering is the overriding mechanism for community assembly, since the pattern of functional clustering was linked to species` similarities in their climatic preferences, which ultimately resulted in shifts in species abundances along the gradient. However, there was no evidence of competitive exclusion at more homogeneous, smaller spatial scales, where plant species effectively compete for resources.

中文翻译:

热带山地森林中跨空间尺度的树木群落组装模式和过程的联系

许多研究试图评估确定性和随机过程在社区组装中的作用,但对于哪些过程更普遍以及它们在哪些空间尺度上运作缺乏共识。为了阐明这个问题,我们测试了两个非互斥的、与尺度相关的假设:1)竞争排斥在小空间尺度上占主导地位;和 2) 环境过滤在较大的情况下这样做。为了实现这一目标,我们使用来自 60 个 0.1 公顷地块的植物区系和功能数据,研究了厄瓜多尔和秘鲁两个海拔梯度上热带山地森林群落的功能模式。我们在小空间尺度上没有发现功能过度分散或聚类的证据,但我们确实在较大的空间尺度上发现了功能聚类。观察到的聚类模式,与环境过滤过程一致,在最大化任何一对地块之间的环境差异时更加明显。为了加强观察到的群落功能模式与环境过滤的潜在过程之间的联系,我们探索了在低海拔和高海拔发现的最丰富物种的气候偏好差异,并检查了它们的丰度是否沿海拔梯度变化。我们发现:1)更大的群落功能差异(在热带山地森林下层和上层森林集合之间观察到)主要是强烈的气候偏好的结果,在整个新热带地区都保持着;2)这些物种的丰度沿着海拔梯度变化。我们的研究结果支持这样一个结论,即在大空间尺度上,环境过滤是群落组装的首要机制,因为功能聚类的模式与物种气候偏好的相似性有关,最终导致物种丰度沿梯度发生变化。然而,没有证据表明在更同质、更小的空间尺度上存在竞争排斥,在这些尺度上,植物物种有效地争夺资源。
更新日期:2020-06-08
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