A test of the generality of leaf trait relationships on the Tibetan Plateau.

Leaf mass per area (LMA), nitrogen concentration (on mass and area bases, N(mass) and N(area), respectively), photosynthetic capacity (A(mass) and A(area)) and photosynthetic nitrogen use efficiency (PNUE) are key foliar traits, but few data are available from cold, high-altitude environments. Here, we systematically measured these leaf traits in 74 species at 49 research sites on the Tibetan Plateau to examine how these traits, measured near the extremes of plant tolerance, compare with global patterns. Overall, Tibetan species had higher leaf nitrogen concentrations and photosynthetic capacities compared with a global dataset, but they had a slightly lower A(mass) at a given N(mass). These leaf trait relationships were consistent with those reported from the global dataset, with slopes of the standardized major axes A(mass)-LMA, N(mass)-LMA and A(mass)-N(mass) identical to those from the global dataset. Climate only weakly modulated leaf traits. Our data indicate that covarying sets of leaf traits are consistent across environments and biogeographic regions. Our results demonstrate functional convergence of leaf trait relationships in an extreme environment.