Nonstructural carbohydrates explain post-fire tree mortality and recovery patterns.

This article investigates the role of nonstructural carbohydrates (NSCs)—stored sugars and starches—in the survival and recovery of young Ponderosa pine (Pinus ponderosa Lawson & C. Lawson) trees following a low-intensity prescribed fire in western Montana, USA. The study found that fire-caused crown injury, measured primarily as crown scorch, leads to significant depletion of NSCs in needles and inner bark (secondary phloem) of branches and main stems, with greater NSC declines associated with higher crown scorch levels. Trees that eventually died exhibited larger NSC reductions, particularly in the main stem phloem, compared to those that survived, suggesting that NSC depletion may be a mechanistic link between fire injury and delayed post-fire mortality. The findings highlight the importance of NSC dynamics in post-fire tree outcomes and suggest that incorporating NSC measures could improve models predicting tree mortality and forest recovery after fire.