Drivers of wildfire burn severity in the montane rainforests of northern Vietnam

Abstract

Background Fire impacts and drivers of wildfire burn severity remain poorly understood for tropical forests. Aims To assess variation and environmental drivers of burn severity for nine forest fires in northern Vietnam. Methods Burn severity was estimated from satellite image analyses, and associations with a remotely sensed index of annual fuel production, topographic factors (elevation, slope, aspect) and weather variables (temperature, rainfall, relative humidity, wind speed) were evaluated. Key results High severity burn areas were found to be fairly uncommon and were associated with steeper, south-west facing slopes, higher elevations and lower fuel abundance. There was a weak tendency for higher burn severity on days with lower relative humidity. Conclusions Conditions that increase fire intensity and the dryness and flammability of fuels are important contributors to high severity fires in wet tropical systems. However, the pattern of higher burn severity at high elevation, where forests tend to be denser and more humid, is counter to this interpretation and may be due to species compositional changes and greater vulnerability of high-elevation forests to fire impacts. Implications Better understanding of fire risk and where in the montane forests of northern Vietnam fires are most likely to burn at high severity will assist forest fire management and recovery strategies.