Optimizing uneven-aged mangement of loblolly pine stands

Although interest in uneven-aged management is growing rapidly, our experience with, and scientific knowledge of, selection silviculture lags far behind that of even-aged. To help alleviate this disparity, we developed nonlinear programming models of uneven-aged loblolly pine and loblolly pine-mixed hardwood management using the model of Lin et al. (1998), a matrix growth and yield model that recognizes three species groups (pines and other softwoods, soft hardwoods, and hard hardwoods) and 13 2-inch diameter-at-breast height (d.b.h.) size classes. The optimization models identify steady-state management regimes which maximize (1) soil expectation value (SEV), (2) annual sawtimber production, (3) the Shannon index of tree diversity, or (4) SEV subject to a constraint requiring the Shannon index of tree diversity to be at feast 75 percent of its theoretical maximum value. The optimal production and economic regimes each involve a guiding maximum diameter for pines and other softwoods and the complete control of all hardwoods each cutting cycle. The optimal production regimes yield low SEVs and moderate diversity; whereas the optimal economic regimes yield low diversity and moderate sawtimber production. Stands with a Shannon index of tree diversity near the theoretical maximum can be sustained in perpetuity but have low SEVs and sawtimber production. The compromise regimes identified by the constrained optimizations give good economic returns, sawtimber yields and diversity.