An Individual-Tree Growth and Yield Prediction System for Uneven-Aged Shortleaf Pine Stands

A system of equations modeling the growth and development of uneven-aged short leaf pine ’ (Pinus echinata Mill.) stands is described. The prediction system consists of two main components: (1) a . dis tanceindependent , individualtree s imulator containing equat ions that forecast ingrowth, basal-area growth, probabi l i ty of survival , total and merchantable heights , and total and merchantable volumes and weights of short leaf pine trees; and (2) s tand-level equat ions that predict hardwood ingrowth, basal-area growth, and mortal i ty . These equat ions were combined into a computer s imulat ion program that forecasts fu ture s ta tes of uneven-aged short leaf pine s tands. Based on comparisons of observed and predicted stand conditions in shortleaf pine permanent forest inventory plots and examination of the growth patterns of hypothetical stands, the simulator makes acceptable forecasts of stand attributes. South. J. Appl. For. 24(2):112-120. i F orecasting the growth and yield of uneven-aged stands is becoming increasingly important as more public agencies and private forest owners incorporate these techniques into their land-management strategies. This is part icularly true of uneven-aged shortleaf pine (Pinus echinata Mill.) stands, given the species’ wide geographic distribution, economic significance, and general lack of published research. Despite that silvicultural system’s lower total merchantable volume output, uneven-aged management of shortleaf and lobloliy (P. taeda L.) pines in the West-Gulf region has tradit ionally been carried out by forest industries producing dimension lumber (Guldin and Baker 1988). Apparently, the combination of low-cost regeneraiion and comparatively high sawtimber volumes has made intensive uneven-aged management an attractive alternative, especially on lower quality sites (Guldin and Baker 1988, Shelton and Murphy 1994). In today’s ever-more-competit ive environment, managers need NOTE: Michael M. Huebschmann is the corresponding author, and he can be reachedat(405) 744-55 15: Fax: (405) 744-9693; E-mail: [email protected]. Approved for publication by the Director, Oklahoma Agricultural Experiment Station. The authors wish to acknowledge the cooperation of Deltic Farm and Timber in providing the data used in this study. Partial funding for this research was provided through a cooperative agreement with the USDA Forest Service, Southern Research Station at Monticello, AR. Manuscript received March 25, 1999, accepted November 22, 1999. to be able to quantify tradeoffs of various management scenarios. To that end, this art icle reports the development of a growth and yield simulator for uneven-aged shortleaf pine s tands . Much of the existing growth and yield information for naturally occurring shortleaf pine is based on data collected from even-aged stands. Yield tables have been developed from temporary plot data (USDA Forest Service 1929, Schumacher and Coile 1960, Murphy and Beltz 1981, Murphy 1982). Individual-tree growth and yield equations have been published for even-aged shortleaf pine stands (Miner et al. 1989, Bolton and Meldahl 1990, Huebschmann et al. 1998, Lynch et al. 1999). Researchers have also proposed a wide variety of quantitative methods for managing uneven-aged stands (Baker et al. 1996). For example, Murphy et al. (1991) applied Marquis’ (1978) BDq method [controlling residual basal area (BA), maximum tree diameter, and the ratio of the number of trees in a given diameter class to its adjacent class(es)]to managing shortleaf pine. Moser and Hall (1969) pioneered a methodology for deriving time-dependent BA and volume prediction functions for uneven-aged forest stands by integrating growthrate equations which do not have time or stand age as an