Persistent, transient, and emergent influences of deer herbivory on canopy gap ground layers, 18 years postdisturbance1

Through their foraging and habitat selection, white-tailed deer (Odocoileus virginianus) can have profound effects on forest plant communities that produce persistent legacy effects. To examine the duration of persistence of potential legacy effects, we investigated the long-term consequences of deer herbivory in plant communities following canopy gap creation in a hemlock-northern hardwood forest in the Upper Peninsula of Michigan. Twenty artificial canopy gaps were created during the winter of 2002-03: seven small gaps (50-150 m2), seven medium gaps (151-250 m2), and six large gaps (251-450 m2). Herbaceous layer communities were sampled within arrays of exclosed and nonexclosed sample plots, established within a few years of gap creation, during the summer of 2020 and compared to a previous study conducted in 2007. Eighteen years following canopy gap creation, herbaceous layer communities exhibited both persistent and transient legacies of deer herbivory. Persistent legacies included similarity of small to large gaps compositionally and low abundance of browse-sensitive species outside of exclosures. Transient patterns included initial high graminoid cover and low cover of trees in the ground layer outside of exclosures and differences in diversity between gap size classes. Some emergent patterns were also observed, including declining floristic quality indices over time but sustained high occurrence of a number of species with moderately high coefficients of conservatism on deer access plots, albeit at low abundance. Differential compositional trajectories emerged based on gap-specific tree species colonization patterns. Our results suggest that through differential foraging patch selection and control of woody regeneration, white-tailed deer may alter or reinforce patterns of dominance depending on initial conditions. These interactions may result in context-specific persistent, transient, and emergent dynamics as plant communities recover from canopy disturbance