Allometry and life history of tropical trees

The scaling of crown size and trunk diameter with tree height (allometry) was determined for 14 common species of the tropical wet lowland forest at La Selva, Costa Rica. The study showed that allometric differences between species are related to adult size, regeneration niche (gap vs. non-gap) and longevity, as follows: (1) adults of understorey species are larger crowned than similar statured (6-15 m) saplings of canopy trees; (2) species commonly found in gaps as saplings are somewhat larger crowned than shade-tolerant species over the 1-6 m height range; and (3) long-lived canopy species show greater increases in crown breadth with increasing height than do short-lived species. Trunkallometryis related to mechanical requirements for support, including the need to withstand greater wind forces in the upper canopy. The common canopy species, Pentaclethra macroloba, which comprises 40% of the basal area at La Selva, is particularly wide-crowned and thick-trunked at its maximum height. On the other hand, the comparatively narrower crowns and trunks of the other canopy species allow them to reach a given height with less biomass. These differences in allometry may influence tree density and forest structure at La Selva.