Fire favours expansion of bamboo-dominated forests in the south-west Amazon

Abstract

Forests dominated by semi-scandent woody bamboos of the genusGuaduacover about 165 000 km2of the south-west Amazon. Because many woody bamboo species are favoured by disturbance some authors have inferred this landscape to be a consequence of indigenous or natural disturbance. As seen in satellite images, the rounded edges of some bamboo-dominated forests indicate expansion into surrounding forest. These edges are unrelated to topography and resemble the borders of ground fires in unlogged Amazon forests, suggesting that bamboo may have been favoured by past fires. We studied the recovery ofGuadua sarcocarpaand its competitors in the face of simulated fire by cutting all plant stems at ground level in ten 100-m2plots, compared with ten control plots, and by burning a 2500-m2plot. In the clear-cuts, bamboos recovered more successfully than did palms and dicots, by two measures: biomass accumulated and per cent recovery of pre-disturbance biomass. Resprouted bamboo attained higher stem densities than in control sites at 11 mo. In the burn plot, bamboo basal area recovered to pre-burn levels after 2 y and approached that of an undisturbed control area after 3 y. Though other natural disturbances are relevant, we conclude that forest fires should favour the spread and dominance ofGuaduaspecies in the south-west Amazon.