Successional trajectories differ among post-harvest and mature cove and upland hardwood forests

Oak (Quercus) dominance in undisturbed eastern hardwood forests is declining as shade-tolerant species (e.g., red maple; Acer rubrum) gradually replace them (termed “mesophication”), especially on mesic sites. In contrast, compositional change can be accelerated after regeneration harvests as regeneration responds to overstory removal. We evaluated the tree and sapling strata over 17 years in mesic, mature cove hardwood (CHM) and subxeric upland hardwood (UHM) forests, and young cove hardwood and upland hardwood stands created by shelterwood-with-reserves harvests (CHSW and UHSW) to assess whether compositional shifts were evident or likely over time. In SWs, saplings comprised the dominant canopy. Compositional differences between the tree and sapling strata in mature forests suggested that CHM will become less “mesophytic” as red maple (a widespread generalist) replaces oak and yellow-poplar (L. tulipifera; a mesophyte) as overstory dominants in the gradual process of forest turnover; UHM will become more “xerophytic-generalist” as red maple and xerophytes (blackgum (Nyssa sylvatica), sourwood (Oxydendrum arboreum) replace oak trees. In contrast, differences between the sapling strata in SWs and the overstory strata in mature forest controls showed that both mesic (CHSW) and subxeric (UHSW) forest types rapidly transitioned to a “mesophytic-generalist” composition as red maple and mesophytes (yellow-poplar, sweet birch (Betula lenta)) quickly dominated the canopy. Interspecific competition may continue to alter successional trajectories as SW stands develop. Our study illustrates strikingly different pathways, rates, and outcomes for shifting species dominance among undisturbed mature and post-harvest stands on mesic and subxeric sites and suggests that changes do not always imply increases in mesophytic species, or “mesophication”.