An economic analysis of hardwood treatment in loblolly pine plantations--a whole rotation dynamic programming approach

Graduation date: 1985To accomplish an economic evaluation of vegetation management in\ud loblolly pine (Pinus taeda L.) at regeneration and a subsequent release\ud time, two existing growth models were linked together in a dynamic\ud programming analysis. The first model (Burkhart and Sprinz, 1984) provides\ud a projection of stands regenerated with varying hardwood components but\ud does not allow intermediate thinning or release entries. The second model\ud (Cao et a/.,, 1982) permits density control through intermediate thinning in\ud pure conifer stands without hardwoods. The combined growth model covers a\ud whole rotation and, hence, vegetation control, intermediate thinnings, and\ud final harvest can be optimized jointly.\ud The resulting analytic model can be used to assess most vegetation\ud management and thinning alternatives including site preparation treatment\ud without subsequent density control of hardwoods. It excludes alternatives that\ud involve conifer density control without previous or concurrent total hardwood\ud removal. The performance of the model indicates that the dynamic programming formulation was able to characterize the economic problem and\ud the interrelationships between vegetation management and further stand\ud development.\ud The economic gains with high interest rates (8 Z) are comparable to\ud current vegetation management costs experienced, while at lower rates the\ud gains are several times current costs. Additional insights to vegetation\ud management impacts are provided through observations on the rotation\ud lengthening impact of any sizeable hardwood component, and through the\ud Impacts of hardwood vegetation on both volume and large diameter tree\ud production.\ud The optimization model also gives new opportunities for analysis of pure\ud loblolly pine stands. The three dimensional dynamic programming network\ud takes Into account the acceleration in diameter growth resulting from thinnings.\ud Quality premiums in sawtimber prices and thinning entry costs can be varied to\ud provide flexibility for economic analysis.\ud Keywords: Dynamic programming optimization, economic analysis, loblolly\ud pine (Pinus Teede L.), thinning regime, vegetation management