Abstract:
The world’s greatest terrestrial stores of biodiversity and carbon
are found in the forests of northern South America, where largescale
biogeographic patterns and processes have recently begun to
be described. Seven of the nine countries with territory in the
Amazon basin and the Guiana shield have carried out large-scale
forest inventories, but such massive data sets have been little
exploited by tropical plant ecologists. Although forest inventories
often lack the species-level identifications favoured by
tropical plant ecologists, their consistency of measurement and
vast spatial coverage make them ideally suited for numerical
analyses at large scales, and a valuable resource to describe the
still poorly understood spatial variation of biomass, diversity,
community composition and forest functioning across the South
American tropics
. Here we show, by using the seven forest
inventories complemented with trait and inventory data collected
elsewhere, two dominant gradients in tree composition and function
across the Amazon, one paralleling a major gradient in soil
fertility and the other paralleling a gradient in dry season length.
The data set also indicates that the dominance of Fabaceae in the
Guiana shield is not necessarily the result of root adaptations to
poor soils (nodulation or ectomycorrhizal associations) but perhaps
also the result of their remarkably high seed mass there as a
potential adaptation to low rates of disturbance.
