The root economics spectrum (RES), a common hypothesis postulating a tradeoff between resource acquisition and conservation traits, is being challenged by conflicting relationships between root diameter, tissue density (RTD) and root nitrogen concentration (RN). Here, we analyze a global trait dataset of absorptive roots for over 800 plant species. For woody species (but not for non-woody species), we find nonlinear relationships between root diameter and RTD and RN, which stem from the allometric relationship between stele and cortical tissues. These nonlinear relationships explain how sampling bias from different ends of the nonlinear curves can result in conflicting trait relationships. Further, the shape of the relationships varies depending on evolutionary context and mycorrhizal affiliation. Importantly, the observed nonlinear trait relationships do not support the RES predictions. Allometry-based nonlinearity of root trait relationships improves our understanding of the ecology, physiology and evolution of absorptive roots.

中文翻译：

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根性状关系和根经济学谱的非线性。

根系经济学谱 (RES) 是一种假设资源获取和保护性状之间权衡的常见假设，它正受到根系直径、组织密度 (RTD) 和根系氮浓度 (RN) 之间相互矛盾的关系的挑战。在这里，我们分析了 800 多种植物的吸收根的全球性状数据集。对于木本植物（但不是非木本植物），我们发现根直径与 RTD 和 RN 之间存在非线性关系，这源于石碑和皮质组织之间的异速关系。这些非线性关系解释了来自非线性曲线不同端的抽样偏差如何导致相互冲突的性状关系。此外，关系的形状因进化背景和菌根隶属关系而异。重要的，观察到的非线性特征关系不支持 RES 预测。基于异速生长的根性状关系非线性提高了我们对吸收性根的生态学、生理学和进化的理解。