Graduate Research and Discovery Symposium (GRADS)

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Shortleaf pine is one of the most important trees in the southeastern United States for lumber, plywood, and pulpwood production. Throughout its range, shortleaf pine is subjected to frequent fires that can be detrimental to seedlings, often leading to death of the stem (top-kill). Frequent fire occurrence has led to the development of fire-adapted traits in shortleaf pine, specifically thick bark and sprouting from the basal crook after top-kill. The thick bark of shortleaf pine acts as a protective barrier for the cambium layer during a fire; while the basal crook is insulated from fire in the soil, protecting auxiliary buds that can initiate sprouts after top-kill. Our study aims to determine what fire adapted traits are responsible for protecting shortleaf pine throughout its life, from seedling to mature tree. The objectives of our study were to characterize shortleaf pine sprouting after top-kill and the development of bark thickness in relation to stem size. To address our objectives, we top-killed shortleaf pines in the Clemson Experimental Forest, SC and the Ouachita National Forest, AR, and measured bark thickness and counted sprouts from the basal crook after a growing season. We found defense mechanism varied by tree size: smaller trees relied on sprouting after top-kill, while larger trees did not sprout as readily. We hypothesize that the larger trees did not sprout because the thicker bark would have protected the cambium layer to decrease the probability of mortality, ultimately demonstrating a shift in fire-defense mechanisms throughout the life of the tree.