The severe deforestation of Brazil’s Atlantic Forest and the increasing effects of climate change underscore the need to understand how tree species respond to climate and edaphic factors. To identify the most important environmental drivers of coastal Atlantic Forest diversity and functional composition, we studied 42 plots of coastal Atlantic Forest (restinga), which has a high diversity of plant communities and spans strong environmental gradients. We examined how forest physiognomy and functional composition respond to changes in the environment, hydraulic, and soil properties. We tested different hypotheses relating the roles of nutrients and soil water availability in driving shifts in tropical forest diversity and functioning. We collected wood samples and leaves from ˜85% of the plant species identified in the forest inventory and estimated the community-weighted tree height, aboveground biomass, basal area of individual plants, specific leaf area, wood density, and the total tree biomass per community by the sum of all trees’ aboveground biomass per plot. We measured water table depth and 24 physicochemical soil parameters. Hypotheses relating to these factors were formalized via both generalized additive models and piecewise structural equation models and null models of community assembly. Increasing drought, as reflected by increasing water table depth, coarse sand, and soil concentration of aluminum (>6 cmol/kg), was found to be a primary driver of shifts in all measured functional traits. Water table depth was found to be the main environmental driver of restinga species diversity, but shifts in species richness were largely decoupled from functional richness and functional dispersion. Our results suggest that decreases in soil water availability are a central driver of local phenotype–environment matching and that increasing water limitation increases the role of environmental filtering on multiple traits. Our results show that drought leads to a strong convergence (standardized effect size < −1.95) in forest function and leads to shifts to smaller statured forest in particular. These findings reveal important differences in the drivers of forest structure and functioning, suggesting that changes in local spatial variation in soil and moisture variables will be a central issue in restinga management and conservation.

中文翻译：

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大西洋森林沿海树木群落植物性状和功能组成的土壤相关驱动因素

巴西大西洋森林的严重森林砍伐和气候变化的影响越来越大，强调需要了解树种如何应对气候和土壤因素。为了确定沿海大西洋森林多样性和功能组成的最重要的环境驱动因素，我们研究了 42 个沿海大西洋森林 (restinga) 地块，这些地块具有高度多样性的植物群落并跨越强烈的环境梯度。我们研究了森林地貌和功能组成如何响应环境、水力和土壤特性的变化。我们测试了有关养分和土壤水分可用性在推动热带森林多样性和功能转变中的作用的不同假设。我们从森林清单中确定的约 85% 的植物物种中收集了木材样品和叶子，并估计了社区加权的树高、地上生物量、单个植物的基面积、比叶面积、木材密度和每株树木的总生物量。群落由每个地块所有树木地上生物量的总和。我们测量了地下水位深度和 24 个物理化学土壤参数。与这些因素相关的假设是通过广义加性模型和分段结构方程模型以及群落集会的零模型形式化的。水位深度、粗沙和土壤铝浓度（>6 cmol/kg）的增加反映了干旱的加剧，被发现是所有测量功能性状变化的主要驱动因素。发现地下水位深度是 restinga 物种多样性的主要环境驱动因素，但物种丰富度的变化在很大程度上与功能丰富度和功能分散脱钩。我们的研究结果表明，土壤可用水量的减少是局部表型-环境匹配的核心驱动因素，而水分限制的增加会增加环境过滤对多种性状的作用。我们的结果表明，干旱导致森林功能的强收敛（标准化效应大小 < -1.95），并导致特别是向较小的森林转移。这些发现揭示了森林结构和功能驱动因素的重要差异，表明土壤和水分变量局部空间变化的变化将成为森林管理和保护的核心问题。