Intraspecific trait variation can weaken interspecific trait correlations when assessing the whole-plant economic spectrum.
Intraspecific trait variation can weaken interspecific trait correlations when assessing the whole-plant economic spectrum.
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DOI：
10.1002/ece3.3447
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发表时间：
2017-11
影响因子：
2.6
通讯作者：
Kramer-Walter KR
中科院分区：
文献类型：
--
作者：
Laughlin DC;Lusk CH;Bellingham PJ;Burslem DFRP;Simpson AH;Kramer-Walter KR
全球植物经济谱假说预测，在维管植物物种中，叶、茎和根的性状是相关的，因为碳的获得依赖于叶片获得充足的水分和营养，而且每个器官的构建涉及到性能和持久性之间的权衡。尽管这一假设具有逻辑和直觉上的吸引力，但它得到了不同的经验支持。如果物种内的性状在对环境梯度的反应中存在差异，那么在自然生态系统中测量时，种间性状相关性可能会减弱。为了验证这一预测，我们测量了56种功能不同树种的相对生长率（RGR）和7个与水、养分和碳通量相关的功能性状，分别是：(1)受控环境下的幼树、(2)林下的幼树和(3)森林中的成熟树木。受控环境下幼体的叶、茎、细根性状相互间密切相关，并与RGR密切相关。值得注意的是，当在受控环境中测量时，七个叶，茎和细根组织性状跨越了一个单一的变化维度。森林生长的幼苗比温室生长的幼苗的单位面积叶质量低，但木材和细根组织密度更高。林生幼树和成熟树的性状和生长速率是不耦合的。结果表明，植物各营养器官间的共变异存在一定的制约因素，而不仅仅是变异；然而，物种内部性状对环境梯度的不同反应掩盖了自然环境中种间性状的相关性。在标准化环境下，植物的器官间、性状间与RGR的相关性较强。我们的研究结果表明，如果在不同的环境中比较物种的性状和生长速度，那么在受控条件下观察到的器官间性状相关性可能会减弱或消失，从而可以调和研究之间的差异。
The worldwide plant economic spectrum hypothesis predicts that leaf, stem, and root traits are correlated across vascular plant species because carbon gain depends on leaves being adequately supplied with water and nutrients, and because construction of each organ involves a trade‐off between performance and persistence. Despite its logical and intuitive appeal, this hypothesis has received mixed empirical support. If traits within species diverge in their responses to an environmental gradient, then interspecific trait correlations could be weakened when measured in natural ecosystems. To test this prediction, we measured relative growth rates (RGR) and seven functional traits that have been shown to be related to fluxes of water, nutrients, and carbon across 56 functionally diverse tree species on (1) juveniles in a controlled environment, (2) juveniles in forest understories, and (3) mature trees in forests. Leaf, stem, and fine root traits of juveniles grown in a controlled environment were closely correlated with each other, and with RGR. Remarkably, the seven leaf, stem, and fine root tissue traits spanned a single dimension of variation when measured in the controlled environment. Forest‐grown juveniles expressed lower leaf mass per area, but higher wood and fine root tissue density, than greenhouse‐grown juveniles. Traits and growth rates were decoupled in forest‐grown juveniles and mature trees. Our results indicate that constraints exist on the covariation, not just the variation, among vegetative plant organs; however, divergent responses of traits within species to environmental gradients can mask interspecific trait correlations in natural environments. Correlations among organs and relationships between traits and RGR were strong when plants were compared in a standardized environment. Our results may reconcile the discrepancies seen among studies, by showing that if traits and growth rates of species are compared across varied environments, then the interorgan trait correlations observed in controlled conditions can weaken or disappear.
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