Declining global leaf nitrogen content : smart resource use by flexible plants?

The availability of data on plant traits and function has expanded markedly in the last decade. Despite this, vegetation model development remains a data-limited activity. Modellers are alert to unifying principles that can substitute rules-demonstrated empirically and supported by theory-for sparse species-level data. This helps the models, which are often applied at large (regional to global) scales, to be more general, tractable and gain adequate predictive skill to be useful. In this light, the evidence that canopy nitrogen content may be a predictable outcome of smart investment of a limited resource by functionally flexible plants is compelling.