FFS: Recent Fire-Ecophysiology Research

Fire, Fuel and Smoke Science Program: Recent Fire-Ecophysiology Research

Starving after fire: crown scorch depletes stored carbohydrates and contributes to tree death. Presented by Sharon Hood

Impacts of prescribed fire on drought vulnerability of ponderosa pine and Douglas-fir. Presented by Charlotte Reed

A temperature-dependent process model of leaf necrosis by heat. Presented by Kate Fuller

Starving after fire: crown scorch depletes stored carbohydrates and contributes to tree death. Trees use nonstructural carbohydrates (NSCs) to support many functions, including recovery from disturbances. However, NSC’s importance for recovery following fire and whether NSC depletion contributes to post-fire delayed mortality is largely unknown. We investigated how fire affects NSCs based on fire-caused injury from a prescribed fire in a young Pinus ponderosa stand. We assessed crown injury (needle scorch, bud kill) and measured NSCs of needles and inner bark (i.e., secondary phloem) of branches and main stems of trees subject to fire and at an adjacent unburned site. We measured NSCs pre-fire and six timesteps post-fire (4 days through 16 months). While all trees initially survived the fire, NSC concentrations declined quickly in burned trees relative to unburned controls over the same post-fire period. This decline was strongest for trees that eventually died, but those that survived recovered to unburned levels within 14 months post-fire. Two months post-fire, the relationship between crown scorch and NSCs of the main stem inner bark was strongly negative. Our results support the importance of NSCs for tree survival and recovery post-fire and suggest that post-fire NSC depletion is in part related to reduced photosynthetic leaf area that subsequently limits carbohydrate availability for maintaining tree function. Crown scorch is a commonly measured metric of tree-level fire severity and is often linked to post-fire tree outcome (i.e., recovery or mortality). Thus, our finding that NSC depletion may be the mechanistic link between the fire-caused injury and tree outcome will help improve models of post-fire tree mortality and forest recovery.