Tree species in tropical rain forests vary widely in their maximum height at adulthood and thus occupy many levels in the forest. In contrast, trees in temperate forests tend to concentrate in the upper canopy, and there is a relative scarcity of understory or subcanopy species.
King et al. tested a recent forest dynamics model indicating that greater diversity in adult stature in tropical forests as compared to temperate forests reflects the reduced exclusion of smaller species by canopy species. Measurements of the relative abundances of adult subcanopy species and saplings of canopy species in temperate, subtropical, and tropical forests indicate that there are greater rates of recruitment and establishment of subcanopy species in low-latitude habitats. The underlying mechanism that allows the greater diversity in tree stature in tropical forests may be a combination of varying crown geometries, the length of the growing season, and the extent of light penetration to lower levels in the forest through gaps in the upper canopy. -- AMS
J. Trop. Ecol. 22, 11 (2006).
