Global Leaf Trait Relationships: Mass, Area, and the Leaf Economics Spectrum

Getting It Wright? In 2004, a paper by Wright et al. comparing six leaf traits of over 2000 plant species showed that between-species variation among the traits was confined primarily to a single multidimensional axis, but only if traits were normalized by leaf mass. This “leaf economic spectrum” has been influential in guiding understanding of the roles of plants in global carbon cycling. Osnas et al. (p. 741 , published online 28 March) now show that the principal finding of Wright et al. is primarily a mathematical consequence of the way that the data were normalized. Analysis of the same data suggests that traits are primarily proportional to leaf area, not leaf mass. Using a method to analyze relationships among traits without normalization-induced correlations revealed a multidimensional correlation between leaf traits. These relationships imply weaker effects of leaf nitrogen on rates of photosynthesis and respiration, with important implications for current models of global change.