Vegetative Regeneration Delays but Does Not Prevent Regeneration Debt: Thirty Years of Compositional and Structural Change in Adjacent Appalachian Forest Communities

Eastern deciduous forests are undergoing directional compositional shifts, marked by the progressive replacement of Quercus-dominated canopies with generalists and shade-tolerant taxa. These shifts are increasingly interpreted within a regeneration debt framework, in which canopy composition persists despite recruitment failure and regeneration mismatch in smaller size classes. We evaluated 30 years (1995–2025) of compositional and structural change in adjacent upland and cove forests on the southern Cumberland Plateau, Tennessee, using a permanent nested circular plot design to determine whether previously observed upland resistance reflects durable resilience or delayed demographic transition. Both habitats exhibited continued Quercus decline while remaining compositionally distinct. As documented in prior analyses, reductions in small-diameter stems were more pronounced in the cove forest, but now reveal demographic mismatches between canopy and regeneration layers in both habitats. Upland forests maintained a higher representation of species capable of basal sprouting and clonal growth via root suckering, indicating that vegetative regeneration buffered short-term demographic change. However, recruitment into larger size classes declined in both habitats, demonstrating that buffering facilitated by vegetative regeneration delayed but did not prevent the accumulation of regeneration debt. What appeared as differential resistance through 2014 is more accurately interpreted as temporal offset in regeneration debt accumulation.