Abstract: Freezing temperatures set the northmost distributional limit for most Neotropical tree species. For example, the Neotropical dry forest reaches almost as far as 30 degrees N in northwestern Mexico, where recurrent winter mild frosts are common. However, topoclimatic refugia may help Neotropical tree species to survive severe frost in their northmost limit. The historic cold wave that affected much of North America in early February 2011 led to freezing temperatures in northwestern Mexico for at least three consecutive days, inducing extensive vegetation damage in the northmost Neotropical dry forest. We performed an analysis of NDVI anomalies in relation to latitude, topography and climate to investigate their relative influence on frost-induced vegetation damage in the northmost Neotropical dry forest region. The growing season (summer) after the February 2011 frost, negative NDVI anomalies occurred in 23% of the region, suggesting widespread frost-induced vegetation damage. We found high negative correlations between NDVI anomalies with elevation and latitude, and moderate negative correlations with terrain roughness and slope. We conclude that topography strongly controls the regional effects of frost damage on vegetation. Tropical vegetation closer to the northmost distributional limit in America are even more vulnerable to severe frost. Therefore, identifying topoclimatic refugia in this region is essential to design biodiversity conservation strategies under future climate extremes.
