Tree survival and resprouting after wildfire in tropical dry and subhumid ecosystems of Chiquitania, Bolivia

Abstract

Lack of understanding the negative and positive effects of wildfires poses a challenge to the restoration and management of tropical ecosystems. Although fire can have negative impacts on tropical forests, it is known that many tropical savanna and woodland species are adapted to fire. The objective of this study was to determine the resilience of tree species to wildfire in a seasonally dry region of eastern lowland Bolivia. The study was carried out in four tropical dry Chiquitano ecosystems (Abayoy, Cerrado, Chiquitano dry forest, and sub-humid forest), in the department of Santa Cruz, 6–18 months after wildfires occurred in July - October 2019. At 45 sampling points, in both burned and unburned areas, we established 50-m x 5-m transects to determine tree species composition, number of individuals, resprout types, survival, diameter, and height of individuals that were ≥1 cm diameter at breast height (DBH). We calculated the percentages of surviving and dead stems by resprout categories and used logistic regression to determine the probability of survival and probability of resprouting as a function of pre-burn size. In the four ecosystems, 35–71% of the individuals sampled survived (crown and basal resprouting) after fire, while an additional 18–59% of individuals had only basal resprouting. Tree mortality (no reprouts) ranged from 5 to 11%. In burned areas, larger-diameter trees had a greater probability of survival. In contrast, the smaller-diameter trees had a higher probability of resprouting from the base. In conclusion, the Chiquitano tropical dry ecosystems have a high resilience to wildfire in terms of survival and resprouting. Resprouting strategy appears to be an important survival mechanism in trees, especially small trees, and must be considered in the passive restoration of burned forests.