Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Biological Sciences

First Advisor

William J. Platt


In an analysis of latitudinally replicated one hectare samples, nine seasonal forests of the temperate and tropical Americas were found to be very similar in biomass, stratification and patterns of spatial dispersion, regardless of taxonomic composition or relative stem density. Neither basal area nor relative size class distributions of trees differed significantly among latitudes from the equator to 40$\sp\circ$ north. While overall plant density was greater in tropical forests, the numbers and composition within individual strata--shrub layer, subcanopy, canopy, and liana--interacted independently and significantly with latitude. Understory populations were denser and more speciose at middle latitudes, in forests frequently affected by hurricanes. Canopy trees were randomly dispersed at all sites; understory stems were uniformly interstitial relative to the canopy, except for lianas which varied in dispersal at each site. Species numbers did not peak in the equatorial forest, but in the continental forests of western meso-America; no latitudinal gradient of species increase was found.