Laurance, W.F. et al. (2004) Pervasive alteration of tree communities
in undisturbed Amazonian forests. Nature 428, 171–175
Abstract:
Amazonian rainforests are some of the most species-rich tree
communities on earth1. Here we show that, over the past two
decades, forests in a central Amazonian landscape have experienced
highly nonrandom changes in dynamics and composition.
Our analyses are based on a network of 18 permanent plots
unaffected by any detectable disturbance. Within these plots,
rates of tree mortality, recruitment and growth have increased
over time. Of 115 relatively abundant tree genera, 27 changed
significantly in population density or basal area—a value nearly
14 times greater than that expected by chance. An independent,
eight-year study in nearby forests corroborates these shifts in
composition. Contrary to recent predictions2–5, we observed no
increase in pioneer trees. However, genera of faster-growing
trees, including many canopy and emergent species, are increasing
in dominance or density, whereas genera of slower-growing
trees, including many subcanopy species, are declining. Rising
atmospheric CO2 concentrations6 may explain these changes,
although the effects of this and other large-scale environmental
alterations remain uncertain. These compositional changes could
have important impacts on the carbon storage, dynamics and
biota of Amazonian forests.