The contribution of interspecific variation in maximum tree height to tropical and temperate diversity

Maximum height was assessed for tree species from seven temperate deciduous forests, one subtropical forest and one tropical forest and combined with published tree heights for three other tropical forests. The temperate deciduous forests showed a strong concentration of canopy species and a dearth of subcanopy species. In contrast. the four tropical forests showed more uniform distributions of maximum heights, while the subtropical forest had an intermediate distribution. The tropical and subtropical sites had greater densities of small trees than did the temperate sites and most of these small trees were members of small- to medium-sized species. Sapling recruitment per unit stem basal area increased with declining maximum height in Panama, which is consistent with the criterion for coexistence of species of differing stature derived from Kohyama's forest architecture hypothesis. Greater penetration of light into gaps and favourable conditions for growth over most of the year may allow more smaller-statured species to coexist with canopy trees in tropical vs. temperate forests.