Forest fires facilitate growth of herbaceous bamboos in central Amazonia

Severe droughts in Amazonia caused by El Nino and Atlantic dipole events are expected to become more frequent due to anthropogenic climate change. These droughts lead the tropical forests of central Amazonia to become increasingly exposed to fire. Forest-fire disturbances can create ideal scenarios for opportunistic plants, such as some bamboos. In this study, we investigate the influence of forest fires, canopy openness, and vertical distance to channel network (VDCN-a proxy for soil moisture availability) on the growth and expansion of Olyra latifolia and Taquara micrantha in the municipality of Autazes, Amazonas, Brazil. The density of these herbaceous bamboos was represented by the density of clumps (clumps ha(-1)) and of culms (culms ha(-1)), while bamboo growth was expressed as culms per clump and the average height of clumps. Forest disturbed by fire had a density of culms 116% higher than the value found in the control treatment. Plots affected by fire, which were at lower VDCN, showed evidence of higher potential for fire ignition in the low areas. The average number of culms per clump was significantly higher in post-burn forests. While canopy opening revealed a significant positive linear relationship with the abundance of herbaceous bamboo in our study area, VDCN had a negative effect on bamboo growth, suggesting that, in addition to fire, light in the understory and access to the water table are limiting factors for these two species in the upland forests of central Amazonia.