Data from: 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, physiology and evolution of absorptive roots.