Composition and Structure of Seasonally Deciduous Forests in the Americas

Forest canopies with leaves shed annually (seasonally deciduous forests) produce a different subcanopy environment than canopies with persistent leaves (evergreen forests). Although causes differ with latitude, seasonality might affect structure and composition of forests similarly. We explored changes in species composition and vertical structure in seasonally deciduous forests from 0°-40° N in the Americas. We measured all woody stems ≥1 cm dbh within replicated 0.0625-ha plots (16 at each of 9 sites, N > 31 000). Numbers of species, as well as density and basal area, were analyzed parametrically for canopy trees, subcanopy trees, shrubs, and lianas. Numbers of species, especially shrubs and subcanopy trees, were greater in warm (30° N) than cool (40° N) temperate forests. Much larger numbers occurred in subtropical (20° N) and tropical (10° N and 0°) forests, but did not vary in relation to latitude. Higher than expected numbers in areas