Functional traits of 7 spp of tropical palms in Costa Rica

Functional traits influence life history strategies. Leaf economics spectrum theory shows the existence of two opposing life history strategies: species with an “acquisitive” strategy that exploit high-resource environments, and species with a “conservative” strategy thriving in low-resource conditions. We analyze interspecific variation in nine functional traits related to biomass allocation and tissue quality (tissue density, dry mass fraction -dmf-, slenderness ratio, carbon content, diameter, height, leaf area, and root:shoot ratios based on biomass and carbon content) in seven species of palms from three forest strata (understory, subcanopy, and canopy). We found two groups of correlated traits. The first one included traits related to palm size (i.e., height, carbon content and leaf area), whereas the second group included traits associated to biomass distribution (i.e., dmf and tissue density). We selected four principal components explaining 87.48% of the variation. The first one (40.32%) was influenced by variables related to palm size (e.g., diameter, total carbon content, leaf area, and height), whereas the second one (16.89%) had a similar contribution of tissue density and dmf. Palms segregated in the multidimensional space defined by these two components: understory species were more related to biomass distribution traits (tissue density and dmf), whereas subcanopy and canopy species were associated to palm size traits (diameter, stem height, leaf area, total carbon content). Knowing the role of functional traits in palms is relevant to understand how different resource allocation strategies regulate plant growth in contrasting light environments. Since palms are one of the most abundant life forms in tropical forests, exploring functional trait variation within this group could significantly advance our understanding of plant adaptation to environmental gradients.功能性状（Functional traits）对植物生活史策略具有调控作用。叶片经济谱理论（Leaf economics spectrum theory）揭示了两种截然相反的生活史策略：一类为“获取型”策略物种，可高效利用高资源环境；另一类为“保守型”策略物种，能在低资源条件下存活繁衍。本研究针对7种分别分布于林下层、亚冠层、冠层3种森林层位的棕榈科植物，分析了其9种与生物量分配及组织品质相关的功能性状的种间变异，涵盖组织密度、干物质分数（dry mass fraction, dmf）、细长比、碳含量、基径、株高、叶面积，以及基于生物量和碳含量计算的根冠比（root:shoot ratios）。研究发现存在两组关联性状：第一组包含与棕榈体型相关的性状（即株高、碳含量与叶面积），第二组则与生物量分配相关（即dmf与组织密度）。本研究选取了累计解释87.48%性状变异的4个主成分（principal components），其中第一个主成分（贡献率40.32%）受棕榈体型相关变量影响（如基径、总碳含量、叶面积及株高），第二个主成分（贡献率16.89%）则由组织密度与dmf共同主导，二者贡献相近。在这两个主成分构建的多维空间中，棕榈类群呈现出明显分异：林下层物种更偏向于生物量分配相关性状（组织密度与dmf），而亚冠层与冠层物种则与棕榈体型性状（基径、株高、叶面积、总碳含量）显著相关。明晰棕榈功能性状的作用机制，有助于理解不同资源分配策略如何在异质光照环境下调控植物生长。由于棕榈是热带森林中最丰富的生命类群之一，解析该类群的功能性状变异，可显著推动我们对植物沿环境梯度适应机制的认知。