Postfire tree mortality and recovery: It’s all about the carbs
Heat from wild and prescribed fire can result in injuries such as crown scorch and bud kill to tree crowns. This effectively defoliates, or strips the vegetation from trees without causing immediate mortality. Trees use nonstructural carbohydrates (NSCs) to recover from these types of injuries, but their importance for recovery after fire (and whether nonstructural carbohydrate depletion contributes to postfire delayed mortality) are largely unknown.
Following a prescribed fire in a northern Rocky Mountain Ponderosa pine forest, researchers investigated how fire affected nonstructural carbohydrates based on the level of fire-caused injury a tree sustained. While all trees initially survived the fire, nonstructural carbohydrate concentrations declined quickly in burned trees relative to unburned trees. This decline was strongest for trees that eventually died. The researchers found that crown scorch was closely tied to the concentration of nonstructural carbohydrates in the main stem inner bark.
Crown scorch is a common metric of tree-level fire severity and is linked to postfire tree recovery or mortality. These results support the importance of nonstructural carbohydrates for tree survival and recovery after fire. Showing the mechanistic link between the fire-caused injury and tree outcome will help improve models of postfire tree mortality and forest recovery.
Time series of recovery (live-burned) or death (dead-burned) for trees at the burn site. Photos were taken from the same location at three timesteps after a prescribed fire on April 17th, 2021.