Estimating capacity of managed pine forests in the southeastern U.S. to provide open pine woodland condition and gopher tortoise habitat

Abstract

Pine forests managed for economic return comprise 19% of southeastern U. S. forests and can provide vegetation structure and composition necessary for many wildlife species adapted to open pine conditions. However, in the absence of frequent fire and other disturbance in southeastern pine (Pinus spp.) forests, midstory hardwoods create closed canopy conditions limiting value of pine stands for many endemic, disturbance-adapted wildlife species. Limitations of past research investigating exact mechanisms for producing and maintaining open pine conditions in managed pine systems have led to a paucity of information regarding ecoregion applications and outcomes. This study evaluated (1) to what extent managed pine stands replicate open pine structural conditions and (2) to what extent managed pine stands provide habitat for the gopher tortoise, an open pine keystone species. We used summary statistics from existing literature to identify structural metrics provided by managed loblolly pine (P. taeda) stands and compared them to disturbance-maintained open pine woodlands. We used spatially-explicit forest management simulations to determine amount and configuration of open pine woodland conditions within two large (>9000 ha), economically-feasible managed pine landscapes in the East and West Gulf Coastal Plains ecoregions. As a case study, we estimated availability and connectivity of gopher tortoise (Gopherus polyphemus) habitat, in managed pine stands of the East Gulf Coastal Plains. Pine stands planted at ≤1310 stems/ha (≤530 stems/ac) provide up to four years of “excellent” open pine condition for wildlife following commercial thinning, based on desired conditions for southern pine forests, with temporal availability depending on site quality. Mid-rotation applications of prescribed fire and selective herbicide can extend “excellent” open pine condition initiated by commercial thinning up to an additional four years. Landscape metrics indicated that, under typical management practices, open pine stands can be spatially and temporally connected to the extent necessary to facilitate among-patch movement for many open pine-adapted species of conservation concern. Our landscape analyses indicated tortoises using primarily regenerating and thinned stands potentially can have a relatively even flow of suitable habitat conditions and opportunities to move to adjacent or nearby open stands when currently-occupied stands reach canopy closure. The disturbance regimes inherent in pine plantation management create diverse landscapes that conserve plant and wildlife biodiversity while meeting economic objectives. Therefore, pine plantations may complement current conservation efforts for open pine woodland species dependent on or tolerant of large-scale disturbance and shifting habitat conditions while offering refuge for high vagility species.