A landscape assessment of frost damage in the northmost Neotropical dry forest

Extreme climatic and weather events are inducing widespread tree mortality in many forest ecosystems worldwide. A severe frost related to the historic cold wave that affected much of North America in early February 2011 triggered extensive tree mortality in the lowland tropical dry forest in northwestern Mexico. In this landscape, we assessed frost-induced vegetation damage using anomalies of the widely used NDVI spectral index calculated with a 12-year pre-disturbance reference period. In addition, NDVI anomalies were related to ground-based measures of frost-disturbance severity (density of frost-killed trees) and forest recovery (post-frost recruits and resprouting of surviving trees) obtained in 48 1-ha study plots distributed across the landscape. We found negative NDVI anomalies in 84% of our study area, indicating widespread frost-induced vegetation damage. The relationship between NDVI anomalies and density of frost-killed trees confirmed the level of frost damage across the lowland vegetation, suggesting that even small deviations from long-term mean NDVI values may hint to severe disturbance on forest structure and function. Higher frost-disturbance severity stimulated more new recruitment and less tree resprouting. Our results demonstrate the reliability of spectral indices for rapid assessment of climate-induced vegetation change, the high vulnerability of tropical dry forests to extreme frost and the predominant mechanism of vegetation recovery after severe frost disturbance.