Forest structure of oak plantations after silvicultural treatment to enhance habitat for wildlife

During the past 30 years, thousands of hectares of oak-dominated bottomland hardwood plantations have been planted on agricultural fields in the Mississippi Alluvial Valley. Many of these plantations now have closed canopies and sparse understories. Silvicultural treatments could create a more heterogeneous forest structure, with canopy gaps and increased understory vegetation for wildlife. Lack of volume sufficient for commercial harvest in hardwood plantations has impeded treatments, but demand for woody biomass for energy production may provide a viable means to introduce disturbance beneficial for wildlife. We assessed forest structure in response to prescribed pre-commercial perturbations in hardwood plantations resulting from silvicultural treatments: 1) row thinning by felling every fourth planted row; 2) multiple patch cuts with canopy gaps of 20 years old. These maturing stands are often entering the stem-exclusion stage of stand development with closed canopies and sparse understories (Johnson 2004, Oliver and Larson 1996). During this stage, competition for light hinders the growth of canopy trees. Silvicultural treatments prescribed to enhance structural heterogeneity (both vertical and horizontal) and increase the floristic complexity within these stands may increase availability of food and cover for wildlife species within these stands. Although the effects of forest management on forest structure have been examined (Lorimer 1989, Meadows 1996) and the suitability of this resultant habitat for wildlife species has been evaluated (Twedt 2012, Twedt and Somershoe 2009, Wigley and Roberts 1994), little is known of the effects of forest management within relatively young (<30 year-old) plantations. Despite lack of empirical studies, enhanced wildlife habitat and improved timber production are expected to result from prescribed silvicultural treatments. Analogous forest modification has been ongoing within coniferous forests where managers have used earlystage thinning in young (33-45 years old) stands to emulate late-successional forest conditions: Thinning was deemed successful as a preliminary restoration treatment (Plummer and others 2012). Although we are not advocating late-successional conditions within young (20-30 years old) bottomland hardwood plantations, silvicultural treatment may result in more rapid attainment of stand conditions desired for wildlife as identified by the Lower Mississippi Valley Joint 1Daniel J. Twedt, Wildlife Biologist, USGS Patuxent Wildlife Research Center, University of Memphis, Memphis, TN 38141; CherrieLee P. Phillip, Natural Resource Specialist, U.S Army Corps of Engineers, Hords Creek Lake, 230 Friendship Park Rd, Coleman, TX 76834; Michael P. Guilfoyle, Research Wildlife Biologist, U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180; R. Randy Wilson, Wildlife Biologist, U.S. Fish and Wildlife Service, 6578 Dogwood View Parkway, Suite B, Jackson, MS 39213