The Susceptibility of Southeastern Amazon Forests to Fire: Insights from a Large-Scale Burn Experiment

Abstract

The interaction between droughts and land-use fires threaten the carbon stocks, climate regulatory functions, and biodiversity of Amazon forests, particularly in the southeast, where deforestation and land-use ignitions are high. Repeated, severe, or combined fires and droughts result in tropical forest degradation via nonlinear dynamics and may lead to an alternate vegetation state. Here, we discuss the major insights from the longest (more than 10 years) and largest (150-hectare) experimental burn in Amazon forests. Despite initial forest resistance to low-intensity fires, repeated fire during drought killed the majority of trees, reduced canopy cover by half, and favored invasive grasses - but the persistence of this novel vegetation state is unknown. Forest edges, where drying, fire intensity and grass invasion are greatest, were most vulnerable. Crucial to advancing fire ecology in tropical forests, we need to scale these results to understand how flammability and resilience postfire varies across Amazon forest types.