Plant trait variation drives plant function, community composition and ecosystem processes. However, our current understanding of trait variation disproportionately relies on aboveground observations. Here we integrate root traits into the global framework of plant form and function. We developed and tested an overarching conceptual framework that integrates two recently identified root trait gradients with a well-established aboveground plant trait framework. We confronted our novel framework with published relationships between above- and belowground trait analogues and with multivariate analyses of above- and belowground traits of 2510 species. Our traits represent the leaf and root conservation gradients (specific leaf area, leaf and root nitrogen concentration, and root tissue density), the root collaboration gradient (root diameter and specific root length) and the plant size gradient (plant height and rooting depth). We found that an integrated, whole-plant trait space required as much as four axes. The two main axes represented the fast–slow ‘conservation’ gradient on which leaf and fine-root traits were well aligned, and the ‘collaboration’ gradient in roots. The two additional axes were separate, orthogonal plant size axes for height and rooting depth. This perspective on the multidimensional nature of plant trait variation better encompasses plant function and influence on the surrounding environment.

中文翻译：

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植物形态和功能的综合框架：地下视角

植物性状变异驱动植物功能、群落组成和生态系统过程。然而，我们目前对性状变异的理解不成比例地依赖于地面观察。在这里，我们将根性状整合到植物形态和功能的全局框架中。我们开发并测试了一个总体概念框架，该框架将两个最近确定的根性状梯度与一个完善的地上植物性状框架相结合。我们通过公开的地上和地下性状类似物之间的关系以及对 2510 个物种的地上和地下性状进行多变量分析来面对我们的新框架。我们的性状代表叶和根的保护梯度（比叶面积、叶和根氮浓度以及根组织密度），根协作梯度（根直径和比根长）和植物大小梯度（植物高度和生根深度）。我们发现一个集成的全植物性状空间需要多达四个轴。两个主轴代表叶和细根性状很好对齐的快-慢“保守”梯度，以及根中的“协作”梯度。两个额外的轴是独立的、正交的植物大小轴，用于高度和生根深度。这种关于植物性状变异多维性质的观点更好地涵盖了植物功能和对周围环境的影响。两个主轴代表叶和细根性状很好对齐的快-慢“保守”梯度，以及根中的“协作”梯度。两个额外的轴是独立的、正交的植物大小轴，用于高度和生根深度。这种关于植物性状变异多维性质的观点更好地涵盖了植物功能和对周围环境的影响。两个主轴代表叶和细根性状很好对齐的快-慢“保守”梯度，以及根中的“协作”梯度。两个额外的轴是独立的、正交的植物大小轴，用于高度和生根深度。这种关于植物性状变异多维性质的观点更好地涵盖了植物功能和对周围环境的影响。