Demographic Variation and Demographic Niches of Trees Species in the Barro Colorado Forest

A principal goal for the 50-ha plot on Barro Colorado Island has been to understand demographic variability across the entire community of tree species. Early work used a gap-shade dichotomy, but both recent improvements in statistical methods have quantified the response of growth, survival, and recruitment to light across the entire community. These studies document the trade-off between fast growth in high light and long life in deep shade: response of growth and recruitment to light are correlated with mortality across species. Here we add a matrix analysis of expected adult lifespan of 31 dominant canopy species spanning the range of growth-mortality variation and demonstrate that the trade-off between high growth and long lifespan does not lead to equal population fitness. Instead, we find that expected adult lifespan of saplings is shorter in fast-growing pioneers than in long-lived shade-tolerant species. If reproductive output were equal across the growth-mortality axis, pioneer species could not persist. This suggests that pioneers out-reproduce shade-tolerant species.