Assessing the generality of global leaf trait relationships

TLDR

Global-scale trait relationships provide insight into vegetation evolution and are essential for parameterizing vegetation–climate models. The study aims to enable future vegetation–climate models to incorporate these generalized leaf trait relationships. The authors compiled a large database of hundreds to thousands of species, recording core leaf economics traits such as lifespan, mass per area, photosynthetic capacity, dark respiration, nitrogen and phosphorus concentrations, potassium, photosynthetic N‑use efficiency, and N:P ratio. The analysis shows that although core leaf traits form a global leaf economics spectrum and are intercorrelated across plant functional types, the magnitude of trait variation within groups often exceeds differences among groups, and significant site‑specific heterogeneity—partly driven by sample size—limits the universality of these relationships, with PNUE fitting the spectrum while leaf K and N:P ratios are only loosely linked.

Abstract

• Global-scale quantification of relationships between plant traits gives insight into the evolution of the world's vegetation, and is crucial for parameterizing vegetation–climate models. • A database was compiled, comprising data for hundreds to thousands of species for the core 'leaf economics' traits leaf lifespan, leaf mass per area, photosynthetic capacity, dark respiration, and leaf nitrogen and phosphorus concentrations, as well as leaf potassium, photosynthetic N-use efficiency (PNUE), and leaf N : P ratio. • While mean trait values differed between plant functional types, the range found within groups was often larger than differences among them. Future vegetation–climate models could incorporate this knowledge. • The core leaf traits were intercorrelated, both globally and within plant functional types, forming a 'leaf economics spectrum'. While these relationships are very general, they are not universal, as significant heterogeneity exists between relationships fitted to individual sites. Much, but not all, heterogeneity can be explained by variation in sample size alone. PNUE can also be considered as part of this trait spectrum, whereas leaf K and N : P ratios are only loosely related.