HERBIVORY IMPACTS ON GROWTH AND SURVIVAL OF SEEDLINGS IN BOTTOMLAND HARDWOOD FOREST RESTORATION SITES IN THE POST OAK SAVANNAH AND BLACKLAND PRAIRIE ECOREGIONS OF TEXAS, USA
Interest in bottomland hardwood forests (BLHW) ecology and restoration has increased over the past 40 years. These communities aid in water quality improvement, streambank stabilization, and urban expansion mitigation. They also provide important habitat for many species of wildlife. Since the majority of remaining BLHW are degraded due to land fragmentation, restoration attempts are becoming commonplace within the Western Gulf Coastal Plain. However, restoration success has been mixed, with managers observing survival rates of <15% for desirable species due to various factors. Over two growing seasons, I investigated multiple factors that have potential to limit BLHW restoration success in East Texas. Specifically, I tested the impacts of herbivory by white-tailed deer (Odocoileus virginianus) and feral swine (Sus scrofa) on Nuttall oak (Quercus texana Buckley), Shumard oak (Q. shumardii Buckley), bur oak (Q. macrocarpa Michx.), and pecan (Carya illinoinensis K. Koch) at BLHW restoration sites at four study areas in east Texas. I also tested the effectiveness of portable electric fences and individual tree shelters in protecting seedlings from herbivory. Herbivory was not the major contributor to seedling mortality, but where it occurred, all protected areas demonstrated higher survival (x̅ = 17%) than non-fenced areas (x̅ = 9%). Feral swine were the major contributors to herbivory, while white-tailed deer did not cause notable amounts of seedling mortality. In areas of high white-tailed deer density, prominent browsing was evident, resulting less growth after two years in non-fenced (x̅ = 2.3 cm) and electric fenced (x̅ = 4.3 cm) plots compared to high fence (x̅ = 13.0 cm) and individual tree shelters (x̅ = 24.2 cm). In addition to seedling survival and growth, we observed reduced survival rates (<10%) on sites that were inundated more than 40 days during the growing season. Matching species of interest to the site conditions, specifically local hydrologic regimes, should carry a higher priority in planning a restoration project within BLHW in the Western Gulf Coastal Plain.
feral swine, white-tailed deer, restoration, wildlife impacts, mitigation, Forest Management
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