Effects of uneven-aged silviculture on the stand structure, species composition, and economic returns of loblolly pine stands.

摘要

Uneven-aged silviculture in loblolly pine (Pinus taeda) stands in the southern USA has many economic and ecological benefits. In this paper the consequences of various uneven-aged management regimes are predicted using the SouthPro simulator, a spreadsheet program based on a site- and density-dependent multi-species matrix growth model calibrated from 991 permanent plots of the Southern Forest Inventory and Analysis (SOFIA) database. Results indicate that target distributions for pines with residual merchantable basal areas of ?2.5 m2 ha-1, maximum diameters of ca. 40 cm, and q-ratios of 1.2-1.25 for 2.5 cm DBH (diameter at breast height) classes are likely to provide high economic returns on good sites when combined with hardwood control. Increasing this maximum diameter would enhance tree-size diversity, but reduce sawtimber production and profits. Retaining a hardwood component with 1.15-2.3 m2 ha-1 of basal area could enhance tree-species diversity, but this too would result in moderate reductions in income. Insisting on maximizing tree-size diversity or tree-species diversity among softwoods, soft hardwoods, and hard hardwoods would be quite costly in terms of lost income and production. Results also illustrate how short-term economic incentives can lead to high-grading practices, despite substantial reductions in stand productivity and net returns in the long term.