Post-fire responses of Quercus humboldtii mediated by some functional traits in the forests of the tropical Andes

Abstract

The Andean forest is a high diversity ecosystem. These forests are negatively affected by anthropogenic pressures that have greatly increased wildfires. Wildfires may increase species susceptibility to other disturbances like insect pests. Little is known of these ecosystems, their responses to wildfires, or their interactions with other disturbances. This study seeks to understand what traits mediates the response of Quercus humboldtii to fires and whether a possible interaction of this disturbance with insect herbivory may occur. We analysed changes in biomass, structure and composition and determined the variation in oak regrowth after fires. We studied oak survival and its relationship with functional traits (height and bark thickness) and its interaction with fire and herbivory. We found that after the last fire, there was an impact on the forest in its structure with a mortality of 40% of adult trees and a reduction in tree species diversity. Structural characteristics, such as tree height and bark thickness, influenced survival of oaks while fire stimulated resprouting from the root collar. Although a high herbivory by insects was found, we did not observe any interaction with fire. This study proves that wildfires in northern Andean forests may produce a severe amount of tree mortality and decrease tree diversity. Yet, the dominant Q. humboldtii appears to be a resilient species because its ability to resprout after fire. This response should be monitored to assess potential effects that an increase in the frequency of wildfires coupled with other disturbances may have in changing species composition and structure of Andean forests under new climatic scenarios.