Growth model for all-aged shortleaf pine stands

A site- and density-dependent matrix growth model for all-aged shortleaf pine (Pinus echinata) stands was developed with data from naturally regenerated, permanent plots in the mid-South. Reproduction, growth and mortality equations predict the number shortleaf pine and other softwood, oak, and non-oak hardwood trees per acre in each of 13 two-inch diameter-at-breast height size classes. The model predicted the growth of independent validation plots between the last two inventories with reasonable accuracy, and in accord with previous knowledge, shortleaf pine and other softwoods became the dominant species group in long-term simulations of undisturbed growth on poor sites but was replaced by hardwoods on good sites. For economic analysis, equations to predict total tree height and sawlog length were also developed. To aid the evaluation of alternative management regimes, the growth and yield equations were incorporated into a simulation program, SouthPro. SouthPro predicts stand development, by year and over multiple cutting cycles, given a user-specified initial diameter frequency distribution and cutting regime and reports diameter frequency distributions, basal areas, volumes, incomes, net present values, and the Shannon indices of tree species group and size class diversity in tabulated and graphic form.