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Comparing tropical forest tree size distributions with the pbkp_redictions of metabolic ecology and equilibrium models

Abstract:

Tropical forests vary substantially in the densities of trees of different sizes and thus in above-ground biomass and carbon stores. However, these tree size distributions show fundamental similarities suggestive of underlying general principles. The theory of metabolic ecology pbkp_redicts that tree abundances will scale as the -2 power of diameter. Demographic equilibrium theory explains tree abundances in terms of the scaling of growth and mortality. We use demographic equilibrium theory to derive analytic pbkp_redictions for tree size distributions corresponding to different growth and mortality functions. We test both sets of pbkp_redictions using data from 14 large-scale tropical forest plots encompassing censuses of 473 ha and > 2 million trees. The data are uniformly inconsistent with the pbkp_redictions of metabolic ecology. In most forests, size distributions are much closer to the pbkp_redictions of demographic equilibrium, and thus, intersite variation in size distributions is explained partly by intersite variation in growth and mortality. © 2006 Blackwell Publishing Ltd/CNRS.