LONG-TERM FIRE EXCLUSION WEAKENS THE RESISTANCE OF FIRE-ADAPTED SOUTHERN APPALACHIAN FORESTS TO WILDFIRE

The long-term exclusion of fire may weaken forest resiliency to the return of fire. Tree traits for fire adaption often co-occur with traits for nutrient conservation, including the ectomycorrhizal (ECM) association. In the absence of fire, the ECM strategy may facilitate the accumulation of organic matter, which becomes colonized by fine roots that are vulnerable to consumption. Therefore, stands of fire-adapted trees may become less resistant to wildfire than stands of fire-intolerant trees. We tested this idea following the 2016 Rock Mountain wildfire. We found increasing depth and stocks of the organic horizon and greater fine root abundance within this horizon with increasing ECM dominance, and that the wildfire consumed an equal proportion of organic matter and fine roots across plots. The probability of tree stress and above-ground mortality increased with ECM dominance post fire, indicating that stands of fire-adapted, ECM species had a weakened forest resistance to wildfire.