Data from: Canopy height variation and environmental heterogeneity in the tropical dry forests of coastal Oaxaca, Mexico

Despite its importance for carbon storage and other ecosystem functions, the variation of vegetation canopy height is not yet well understood. We examined the relationship between this community attribute and environmental heterogeneity in a tropical dry forest of southern Mexico. We sampled vegetation in 15 sites along a 100-km coastal stretch of Oaxaca State, and measured the heights of all woody plants (excluding lianas). The majority of the ca. 4000 individuals recorded concentrated in the 4–8 m height range. We defined three plant sets to describe overall community canopy height at each site: a set including all plants, a set made up by the tallest plants representing 10 percent of all individuals, and a set comprising the 10 tallest plants. For each site we computed maximum height and the mean and median heights of the three sets. Significant collinearity was observed between the seven resulting height variables, but null distributions constructed through bootstrap revealed their different behaviors as functions of species richness and density of individuals. Through linear modeling and a model selection procedure, we identified 21 models that best described the variation of canopy height variables. These models pointed out to soil (measured as PC1 of a principal component analysis performed on 10 soil variables), water stress, and elevation as the main drivers of canopy height variation in the region. In the event of increasing water stress resulting from global climate change, the studied tropical dry forests could become shorter and thus decrease their carbon storage potential.尽管植被冠层高度的变化对于碳封存及其他生态系统功能至关重要，但目前学界对其认知仍较为有限。本研究针对墨西哥南部的一处热带旱林，探究了该群落属性与环境异质性之间的关联。我们在瓦哈卡州100公里沿海沿岸带的15个样地开展植被采样，并测定了所有木本植物（藤本植物除外）的株高。本次记录的约4000株个体中，绝大多数株高集中在4至8米区间内。我们定义了三类植株集合，用以表征每个样地的群落整体冠层高度：其一为包含所有植株的全量集合，其二为占总个体数10%的最高大植株集合，其三为株高排名前10的植株集合。针对每个样地，我们分别计算了三类集合的最大株高、平均株高与中位株高。所得到的7个冠层高度变量间存在显著的多重共线性，但通过自举法（Bootstrap）构建的零分布显示，这些变量随物种丰富度与植株个体密度的变化呈现出不同的响应规律。通过线性建模与模型选择流程，我们筛选出21个最优模型，用以精准刻画冠层高度变量的变化规律。上述模型表明，土壤因子（以10项土壤变量的主成分分析（Principal Component Analysis, PCA）第一主成分PC1表征）、水分胁迫与海拔是该区域冠层高度变化的主要驱动因子。若全球气候变化导致区域水分胁迫加剧，本研究涉及的热带旱林株高可能会出现下降，进而降低其碳封存潜力。