Allometric scaling of production and life-history variation in vascular plants

A prominent feature of comparative life histories is the well documented ne gative correlation between growth rate and life span(1,2). Patterns of reso urce allocation during growth and reproduction reflect life-history differe nces between species(1,2). This is particularly striking in tropical forest s, where tree species can differ greatly in their rates of growth and ages of maturity but still attain similar canopy sizes(3,4). Here we provide a t heoretical framework for relating life-history variables to rates of produc tion, dM/dt, where M is above-ground mass and t is time. As metabolic rate limits production as an individual grows, dM/dt proportional to M-3/4. Inco rporating interspecific variation in resource allocation to wood density, w e derive a universal growth law that quantitatively fits data for a large s ample of tropical tree species with diverse life histories. Combined with e volutionary life-history theory(1), the growth law also predicts several qu alitative features of tree demography and reproduction. This framework also provides a general quantitative answer to why relative growth rate (1/M)(d M/df) decreases with increasing plant size (proportional to M-1/4) and how it varies with differing allocation strategies(5-8).