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Abstract
Old-growth longleaf pine ecosystems exhibit overall aesthetics due to canopy complexity of overstory individuals, with some exhibiting discrete canopies with branches concentrated at the top, while others retain more continuous lower branches comprised of additional leaf area. To investigate the influence of structural complexity on ecosystem resilience, we measured the physiological differences at two points along canopy height gradients. This research more specifically included quantifying the stand-level relative frequency of canopy types, vertical distribution of leaf area, and measurements of leaf water potential, photosynthetic assimilation, sap flow rates, and environmental variables. There were fewer discrete canopies, which exhibited more consistent physiological activity under varying environmental conditions, and more continuous canopies retaining the lower strata, which provided important contributions to physiological functions via different responses and proportional shifts from the upper strata. Therefore, greater structural complexity yielded greater resilience of longleaf pine to varying environmental conditions in this old-growth longleaf forest.