Journal 23

Tropical trees in a wind-exposed island ecosystem: height-diameter allometry and size at onset of maturity

Sean C. Thomas, Adam R. Martin and Erin E. Mycroft

Summary

  1. Tropical tree species adapted to high wind environments might be expected to differ systematically in terms of stem allometry and life-history patterns, as compared with species found in less windy forests. We quantified height-diameter (H-D) allometries and relative size at onset of maturity (RSOM) for rain forest tree and tree fern species native to Dominica, West Indies, an island that experiences some of the highest average wind speeds pantropically.
  2. H-D allometries for 17 Dominican angiosperm tree species were strongly concave on a log–log scale with asymptotic heights ranging from 9 to 32 m among species, averaging 25 m for canopy trees. H-D allometries for species-pooled data deviated strongly from recorded patterns for other tropical forest trees: asymptotic heights for trees in Dominica were 30–116% lower than those recorded for continental rain forest trees in Australia, South America, Africa and South-East Asia. In a subset of canopy trees sampled in steep, sheltered valleys, heights were 12–26% larger at a given diameter and approached those observed in other tropical regions, suggesting large phenotypic responses of H-D allometries to wind conditions.
  3. RSOM (quantified as the ratio of height at onset of reproduction to asymptotic maximum height) for Dominican angiosperm species was highly variable, ranging from 0.23 to 0.89 (mean 0.54), similar to patterns observed in Malaysia and Panama; very low RSOM values were estimated for two tree fern species. Pooling data from Dominica with published values from other tropical forests, we observed a significant negative correlation between RSOM and wood density.
  4. Synthesis. Our data suggest that wind regimes are a critical determinant of height-diameter (H-D) allometries of tropical trees at both the local and global scale. Although we found no evidence for a systematic differences in reproductive onset related to wind regime, RSOM was negatively correlated with species’ wood density, suggesting that more shade-tolerant tree species show a longer period of gradually increasing reproductive allocation through ontogeny.

DATE: 2015-2-11