On the conservative nature of the leaf mass-area relationship.

In a previous empirical study, Hughes and colleagues showed that for several herbaceous species there is apparently a unique species-specific relationship between the area and mass of leaves. We tested this proposition using measurements from 15 broad-leaved species. We found that to a reasonable approximation, leaf area was proportional to leaf mass within a given species despite relatively large variations in both leaf thickness and the mass fraction of liquid matter. These observations show that the inverse density-thickness of leaves from a given species, which we call the Hughes constant, is approximately conserved. We conclude that the Hughes constant is likely to be more conservative than other traits traditionally used to describe leaves.