Agriculture Reference
In-Depth Information
There is no end to the number of foliar traits that might characterize essential
elements of foliar function and therefore merit inclusion in a comprehensive
analysis of the leaf economic spectrum. For example, foliar phosphorus and dark
respiration rate are likely candidates (Westoby et al. 2002; Wright et al. 2004), but
the data supporting their inclusion are fewer than are those for the four primary
traits. A subsequent analysis (Wright et al. 2005a, b) gave further support to
inclusion of foliar respiration and also suggested inclusion of photosynthetic
nitrogen use efficiency (PNUE) among the cardinal traits. In the context of theory
for leaf longevity, inclusion of respiration makes some sense as a possible index of
the ongoing costs of foliar maintenance that could augment the initial construction
cost when estimating the timing of leaf senescence. PNUE makes less sense as a
unitary cardinal trait in the context of theory for leaf longevity because it is simply
the ratio of two parameters already accounted for in the syndrome of traits central
to foliar function. In general, it behooves us to look beyond correlations to a
minimal set of traits that can be integrated in a mechanistic model of foliar
function, in the present context a model that can predict leaf longevity.
