Nonlinearity of root trait relationships and the root economics spectrum

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, ...根经济谱（root economics spectrum, RES）是一套通用假说，提出资源获取与保守型性状之间存在权衡关系，但该假说正受到根直径、根组织密度（root tissue density, RTD）与根氮浓度（root nitrogen concentration, RN）之间矛盾关系的挑战。本研究分析了涵盖800余种植物的全球吸收根性状数据集。针对木本植物（而非非木本植物），我们发现根直径与RTD、RN之间存在非线性关系，这一关系源于中柱与皮层组织间的异速生长关系。这类非线性关系解释了为何基于非线性曲线不同端点的采样偏差会导致性状关系出现矛盾。此外，这些关系的形态会随进化背景和菌根共生类型的不同而改变。值得注意的是，本研究观测到的非线性性状关系并不支持根经济谱的预测。基于异速生长的根性状关系的非线性，有助于我们深化对植物生态学的认知，……