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.

功能性状影响植物生活史策略。叶经济谱理论（Leaf economics spectrum theory）指出存在两类截然相反的生活史策略：一类为"攫取型"策略，可适配高资源环境；另一类为"保守型"策略，得以在低资源环境中繁盛生长。本研究针对采自3种森林层次（林下、亚冠层、冠层）的7种棕榈科植物，分析了与生物量分配及组织品质相关的9项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（slenderness ratio）、碳含量、茎直径、株高、叶面积，以及基于生物量与碳含量计算的根冠比。研究发现两类关联性状集群：第一类与棕榈体型大小相关，包括株高、碳含量与叶面积；第二类则与生物量分配相关，涵盖干物质分数与组织密度。本研究选取累计解释87.48%性状变异的4个主成分：第一主成分（贡献率40.32%）受棕榈体型相关变量驱动，包括茎直径、总碳含量、叶面积与株高；第二主成分（贡献率16.89%）则由组织密度与干物质分数共同主导，二者贡献相当。棕榈类群在该二维主成分构建的多维空间中呈现明显分异：林下物种更偏向生物量分配相关性状（组织密度与干物质分数），而亚冠层与冠层物种则与棕榈体型性状（茎直径、株高、叶面积与总碳含量）紧密关联。明确棕榈科植物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。鉴于棕榈科植物是热带森林中最为丰富的生活型类群之一，解析该类群的功能性状变异，将显著推动我们对植物适应环境梯度机制的认知。