Growth and wood density predict tree mortality in Amazon forests

Abstract

1. Tree mortality is an important process in forest ecology. We explored the extent to which tropical tree death is a predictable outcome of taxon and individual level properties by means of mixed-species logistic regression, for trees ≥ 10 cm in diameter. We worked in two lowland forest regions with markedly different floristic composition and dynamic regimes - the high wood density, low-mortality northeastern (NE) Amazon (in eastern Venezuela), and the low wood density, high-mortality northwestern (NW) Amazon (in northern Peru). 2. Among those genera that are shared between regions there were no detectable regional differences in mortality rates. This suggests that floristic compositional differences are a major driver of the twofold regional contrast in stand-level mortality. 3. In NE forests, mortality risk of individual trees is best predicted by low taxon-level wood density, slow relative growth, and large size, reflecting phylogenetically determined life-history strategy, physiological stress and senescence. 4. In NW forests, trees with low wood density and slow relative growth are also at most risk, but probability of death is independent of tree size, indicating that senescence is unimportant in this region. 5. Synthesis. This study shows that despite fundamental floristic and dynamic differences between the two Amazonian regions, mortality risk can be predicted with mixed-species, individual-based statistical models and that the predictors are remarkably similar, such that tree growth and wood density both play important roles. © 2008 The Authors.