Life forms of amazonian palms in relation to forest structure and dynamics

Two Amazonian terra firme forests present contrasting structures and palm compositions: one is characterized by tall and broadtrunked trees up to 50 m in height and 2.5 m in DBH, and by tall arborescent palms; the other by more modest-sized trees up to 40 m in height and 1.3 m in DBH, and by abundant acaulescent and smaller arborescent palms. This comparison strongly suggests that forest structure and dynamics influence life forms, palm size, and species diversity. Gap size, which mainly depends on the size of upper-canopy trees, determines the intensity of light reaching the understory and thus influences the development of arborescent palms. In this analysis, acaulescent forms are regarded as an adaptation to forests with small trees and resultant small gaps.