Using Simple Marginal Analysis and Density Management Diagrams for Prescribing Density Management

This article presents a procedure to produce management regimes that not only maximize land value but also reflect stand development with simple marginal analyses of the accumulation and control of growing stock. An upper limit of growing stock is determined by translating management objectives into a future desired structure, and with this value as a guide for thinning age, marginal analysis is used to determine the planting density and the residual basal area after thinning. The procedure is demonstrated for a hypothetical loblolly pine plantation growing on land with a site index of 65 ft at 25 yr. The effects of various interest rates for a fixed rotation length and various rotation lengths for a fixed interest rate on initial planting density and residual growing stock after low thinning are analyzed. Optimal planting density decreased with increasing interest rate and rotation length. Thinning ages increased as initial planting density decreased, which caused optimal residual growing stock to increase with increasing interest rate and rotation age. According to this study, maximum land value is achieved when the growing stock limits are set to approximately the lower limit of full-site occupancy and the threshold of self-thinning. In terms of relative density, the ideal limits in growing stock for maximizing land value identified in this study are 35 and 55% of maximum SDI. South. J. Appl. For. 26(2):85–92.