Natural Forest Regeneration Changes in an Urban Natural Area Forest with White-Tailed Deer (Odocoileus virginianus) Exclusion and Felling by North American Beaver (Castor canadensis)

Abstract

We examined natural regeneration changes in an urban natural area forest, the Good Woods, Cobbs Creek Park, Philadelphia, Pennsylvania, after placement of exclusion fencing to prevent white-tailed deer (Odocoileus virginianus) browsing and unplanned North American beaver (Castor canadensis) felling. Seedlings (stem dbh < 2.5 cm, stump at 15 cm < 3.0 cm), saplings (stem dbh > 2.5–10 cm, stump at 15 cm > 3.0–11 cm), and trees (stem dbh > 10 cm, stump at 15 cm > 11 cm) were surveyed in 65 permanent 10 m × 10 m plots: 6 y after fencing placement to exclude white-tailed deer and 5 mo after the start of beaver felling. Overall seedling abundance increased by 5% while sapling populations grew by 20% and the number of trees expanded by 34% after white-tailed deer exclusion. Red maple (Acer rubrum) seedlings, tulip poplar (Liriodendron tulipifera) seedlings, and red oak (Quercus rubra) saplings increased significantly while pignut hickory (Carya glabra) and white ash (Fraxinus americana) seedlings decreased significantly. Seedling and tree losses to North American beaver felling were small (<2% for all seedlings and <3% for all trees). However, beaver felling caused a greater than 60% loss of saplings for red maple, black cherry (Prunus serotina), white oak (Quercus alba), and red oak. Less than 30% of the saplings were lost for pignut hickory, white ash, and tulip poplar. Urban North American beaver preferences for native species saplings paralleled rural beaver in the eastern United States. Our results indicate white-tailed deer exclusion fencing is an effective management method for increasing natural regeneration of both seedlings and saplings in an urban natural area forest when the fencing also effectively excludes North American beaver.