Assessment of a 15-year white-tailed deer management program and woody recovery in a suburban forest preserve

Abstract

Overbrowsing by highly abundant white-tailed deer (Odocoileus virginianus) negatively impacts the regeneration of the forest understory throughout the eastern United States. Deer management programs are often used by land managers to reduce deer densities and promote forest regeneration. This study examines the impact of a 15-year-long archery-based deer management program on the understory of a nature preserve in southern NY consisting of an old-growth hemlock and second-growth mixed hardwood forest. Vegetation plots were sampled every 3–5 years between 2004 and 2019, while deer density was estimated using camera trap survey data annually since 2009. Generalized mixed-effects models were used to determine the influence of deer density, forest type, canopy cover, and time on species richness, native stem density and total stem density. The most predictive models showed an increase in richness as time went on. Additionally, stem density had a negative relationship with deer density (i.e., stem density and species richness increased as deer density declined over time). For both native and total stem density, the highest-ranked model included only deer density as a predictor. Generally, woody species richness and stem density increased in the seedling (<0.3 m tall) and sapling (0.3–0.9 m tall) size classes but remained relatively constant for the transgressive (>0.9 m) size class over time and as deer density decreased. Many native species exhibited density increases in the smallest size classes, but black birch (Betula lenta), American beech (Fagus grandifolia), and mapleleaf viburnum (Viburnum acerifolium) were the only native species to increase in the transgressive (>0.9 m tall) class. Several non-native species, however, did increase in the transgressive size class since 2004. These results indicate that the forest has improved as a result of the DMP, but long-term recruitment of native species is still uncertain. The DMP has shown the potential to help restore woody regeneration but monitoring should continue to ultimately determine whether deer management can allow for true recruitment of native seedlings into the forest understory and canopy.