Departmental Publications, Forest Resources and Environmental Conservation

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Aids for Unit Planning on the Appalachian National Forests
Burkhart, Harold E.; Leuschner, William A.; Stuck, R. Dean; Porter, John R.; Reynolds, Marion R. Jr. (Virginia Tech. Division of Forestry and Wildlife Resources, 1976)
This report summarizes the results of studies conducted in response to a cooperative agreement between the Southern Region, U.S. Forest Service and the Department of Forestry and Forest Products, Virginia Polytechnic Institute and State University. The objective of the agreement was to improve National Forest management planning techniques. The agreement covered the period July 1, 1973 to June 30, 1975. Literature citations are given for those who desire additional detail.
A Comparison of Growth and Yield Prediction Models for Loblolly Pine
Burkhart, Harold E.; Cao, Quang V.; Ware, Kenneth D. (Virginia Tech. Division of Forestry and Wildlife Resources, 1981)
The objective of the study reported here was to analyze published growth and yield systems for loblolly pine, characterizing the nature of the data on which the study was based, specifying what input information is needed, and stating what output estimates and predictions are obtainable. Predicted values from various studies are also compared vis-a-vis those from other investigations, and, where possible, conclusions and recommendations are drawn.
Diameter Distributions and Yields of Natural Stands of Loblolly Pine
Burk, Thomas E.; Burkhart, Harold E. (Virginia Tech. Division of Forestry and Wildlife Resources, 1984)
A diameter distribution yield model was developed based upon measurements of 117 0.1-acre temporary plots located in naturally regenerated loblolly pine stands in the Piedmont and Coastal Plain of Virginia and the Coastal Plain of North Carolina. Diameter distributions were derived using the Weibull density function by requiring that the distribution's arithmetic and quadratic means matched those predicted from stand-level attributes using regression equations. Software was written in FORTRAN and BASIC implementing the model and an existing basal area projection equation. Stand and stock tables are presented for 30-year projections from age 20 for various combinations of site index and initial basal area.
Diameter Distributions and Yields Of Thinned Loblolly Pine Plantations
Cao, Quang V.; Burkhart, Harold E.; Lemin, Ronald C., Jr. (Virginia Tech. Division of Forestry and Wildlife Resources, 1982)
A growth and yield model for thinned loblolly pine plantations was developed using data from 128 0.2-acre permanent plots in the Virginia Piedmont and Coastal Plain. The Weibull function, used to characterize stand diameter distributions, was searched to insure that the resulting total basal area and average dbh estimates were identical to those predicted from stand variables using regression equations. Program WTHIN was written in standard FORTRAN to provide stand and stock tables for thinned old-field loblolly pine plantations. Trials with different thinning intensities indicated reasonable trends, as compared with published studies.
Economic Guidelines for Loblolly Pine Management in Virginia
Thompson, Emmett F.; Mantie, Robert C.; Sullivan, Alfred D.; Burkhart, Harold E. (Virginia Tech. Division of Forestry and Wildlife Resources, 1973-12)
Recent studies (e.g. Southern Forest Resource Analysis Committee, 1969; U. S. Forest Service, 1972) indicate that wood requirements may exceed available supplies by the end of this century. The latest forest survey of Virginia (Knight and McClure, 1967) indicated a 15 percent excess of pine cut over pine growth As a result of this latter finding, Virginia's General Assembly passed a 1970 Reforestation of Timberlands Act. This Act provides financial assistance to private landowners to restore former pine growing lands to pine production. Virginia has clearly established a state policy of encouraging investment in forest production. However, individual landowners may have alternative uses for their land and/or capital, or they may not be fully aware of their land's potential for timber. The specific objective of this study was to develop a means for making economic data on using their land for loblolly pine production available to Virginia's individual forest landowners. The study was limited to loblolly pine for several reasons. Loblolly pine is perhaps the most important of the. timber species currently grown in Virginia, and it is expected to increase in importance.Of the 67.5 million tree seedlings planted in Virginia in 1972, 62.0 million were loblolly pine and 36.5 million of these were planted by farmers and other individuals (Virginia Forests, 1972). Loblolly pine accounts for over 90 per cent of the approximately 85 thousand acres artificially regenerated in Virginia each year (Shores, 1970). In addition, new information on the physical yields of natural stands of loblolly pine and loblolly pine plantations in Virginia has recently become available (Burkhart, et al., 1972a; Burkhart, et al., 1972b).
Growth and Yield of Appalachian Mixed Hardwoods After Thinning
Harrison, Wade C.; Burkhart, Harold E.; Burk, Thomas E.; Beck, Donald E. (Virginia Tech. Division of Forestry and Wildlife Resources, 1986)
G-HAT (Growth of Hardwoods After Thinning) is a system of computer programs used to predict growth and yield of Appalachian mixed hardwoods after thinning. Given a tree list or stand table, along with inputs of stand age, site index, and stand basal area before thinning, G-HAT software uses species-specific individual tree equations to predict tree basal area increment and total height for the residual stand. Cubic foot volumes, based on desired merchantability standards, may be obtained for thinned trees, the residual stand, and the projected stand. G-HAT is available as a self-contained, interactive program (BASIC G-HAT) or as a library of FORTRAN subroutines (FORTRAN G-HAT). BASIC G-HAT, for personal computers, is designed for interactive, user-friendly sessions with keyboard input and screen output. Its use requires no programming ability. FORTRAN G-HAT is compatible with mainframe computers, minicomputers, and personal computers. It consists of modular subroutines which allow considerable flexibility in application, such as interface with computerized timber inventory systems and stand simulators.
Methods for Modeling Individual Tree Growth and Stand Development in Seeded Loblolly Pine Stands
Daniels, Richard F.; Burkhart, Harold E.; Spittle, Gerald D.; Somers, Greg L. (Virginia Tech. Division of Forestry and Wildlife Resources, 1979)
Methods were developed to model growth and development of seeded loblolly pine (Pinus taeda L.) stands, using individual trees as the basic growth units. Aggregated spatial patterns and individual tree sizes are generated at age 10. Tree diameters and heights are then incremented annually as a function of their size, site quality, competition from neighbors, and stochastic components representing genetic and microsite variability. Individual tree mortality is determined stochastically through Bernouli trials. Subroutines were developed to simulate the effects of hardwood competition and control, thinning, and fertilization. The overall model was programmed in FORTRAN and initial tests were made with published yields. The initial stand generation components were calibrated using a comprehensive set of data from young seeded stands of loblolly pine, but individual tree growth and mortality components relied on previously published relationships developed for plantations. Results indicated that, in order to accurately model stand structure, the growth and mortality relationships must be calibrated for seeded stands. Data collection procedures, calibration methods, and recommendations for further work are discussed.
A Model for Assessing Hardwood Competition Effects on Yields of Loblolly Pine Plantations
Burkhart, Harold E.; Sprinz, Peter T. (Virginia Tech. Division of Forestry and Wildlife Resources, 1984)
A model was developed to predict pine survival, growth and yield for unthinned loblolly pine plantations with varying levels of hardwood competition in the main canopy. Inputs for the model are number of loblolly pine trees per acre planted, site index for loblolly pine, percent of hardwood basal area in the main canopy of the stand, and age(s) at which output is desired. From these inputs the model computes, by 1-inch dbh classes, the number of trees surviving, basal area, and volumes per acre. The model, which was constructed using sample plot data from old-field and cutover-site plantations, was validated with independent data from a hardwood conversion/site preparation study. Overall, there was close agreement between the observed values and the model predictions.
Simulation of Individual Tree Growth and Stand Development in Loblolly Pine Plantations on Cutover, Site-Prepared Areas
Burkhart, Harold E.; Farrar, Kenneth D.; Amateis, Ralph L.; Daniels, Richard F. (Virginia Tech. Division of Forestry and Wildlife Resources, 1987)
A forest stand simulator, PTAEDA2, was developed to model growth in loblolly pine (Pinus taeda L.) plantations on cutover, site-prepared areas. Individual trees were used as the basic growth units. In PTAEDA2, trees are assigned coordinate locations in a stand and 'grown' annually as a function of their size, the site quality, and the competition from neighbors. Growth increments are adjusted by stochastic elements representing genetic and microsite variability. Mortality is generated stochastically through Bernouli trials, Subroutines were developed to simulate the effects of hardwood competition, thinning, and fertilization on tree and stand development. Options for varying the spatial location of trees to mimic randomness in machine and hand planting operations are also included.
Simulation of Individual Tree Growth and Stand Development in Managed Loblolly Pine Plantations
Daniels, Richard F.; Burkhart, Harold E. (Virginia Tech. Division of Forestry and Wildlife Resources, 1975)
A FORTRAN based simulator, PTAEDA, was developed to model growth in managed loblolly pine (Pin us taeda L.) plantations, using individual trees as the basic growth units. In PTAEDA, trees are assigned coordinate locations in a stand and "grown" annually as a function of their size, the site quality, and the competition from neighbors. Growth increments are adjusted by stochastic elements representing genetic and microsite variability. Mortality is generated stochastically through Bernouli trials. Subroutines were developed to simulate the effects of site preparation, thinning, and fertilization on tree and stand development. Comparisons with published yields showed close agreement for thinned and unthinned old-field plantations. Results indicated that, compared to stand-level models used in the past, the simulator is more flexible in terms of growth and yield estimation and evaluation of alternatives under a wide range of management regimes.
Site and Yield Information Applicable to Virginia’s Hardwoods: A Review
Evans, Thomas F.; Burkhart, Harold E.; Parker, Robert C. (Virginia Tech. Division of Forestry and Wildlife Resources, 1975)
In 1966 Virginia had a hardwood growing stock volume of 10.5 billion cubic feet and a hardwood sawtimber volume of almost 26. 3 billion board feet. Hardwood timber was distributed over more than 12.8 million acres of commercial forest land in the state (Knight and McClure, 1967). This hardwood timber is converted into a multitude of finished products. Hardwoods comprise well over one-half of the total volume in Virginia's multi-million dollar forest products industry each year. Thus the hardwood resource is very important to the welfare of the citizens of the Old Dominion. Despite the importance of hardwoods in Virginia's timber industry, most hardwood stands have not been placed under intensive forest management. An essential ingredient of a forest management program is information on the yields of timber products which can be achieved by the various tree species on different sites. Yield and site data which can be applied to Virginia's hardwoods are still relatively scarce. The purpose of this paper is to survey the primary works on the yields of hardwood species found in Virginia and to present results from studies on the relations of hardwood growth to various site conditions.
Yields and Size Class Distributions for Unthinned Loblolly Pine Plantations on Cutover Site-Prepared Lands
Amateis, Ralph L.; Burkhart, Harold E.; Knoebel, Bruce R.; Sprinz, Peter T. (Virginia Tech. Division of Forestry and Wildlife Resources, 1984)
Data from plots established in unthinned loblolly pine plantations on cutover site-prepared lands were used to develop size class distribution and yield predictions. The data come from plantations of loblolly pine established over much of its natural range and represent a wide variety of stand conditions and site-preparation treatments. A three parameter Weibull density function was used to model diameter distributions, and a computer program, COYIELD, was developed to predict yields from stand attributes. The predicted yields should satisfactorily represent many sites in the Piedmont and Coastal Plain regions of the Southern United States.
Yields of Old-Field Loblolly Pine Plantations
Burkhart, Harold E.; Parker, Robert C.; Strub, Mike R.; Oderwald, Richard G. (Virginia Tech. Division of Forestry and Wildlife Resources, 1972-12)
Loblolly pine (Pinus taeda L.) is one of the most important commercial species to the forest industries in the South, with a range extending through the Piedmont and the Atlantic and Gulf Coastal Plains from Maryland to eastern Texas. Although there is a great deal of published information on the growth and yield of loblolly pine, much of the data for these studies has been collected in the southeastern part of the natural loblolly pine range and published results have generally involved only volume units such as board feet, cubic feet, or cords. Consequently, a cooperative yield study between the Division of Forestry and Wildlife Resources at Virginia Polytechnic Institute and State University and several industrial forestry organizations was initiated to gather yield information which would be primarily applicable to the Virginia area. The scope of this study included per-tree and peracre data for the various volume units as well as for green and dry weight. This paper presents per-acre yield information in volume and weight units for old-field loblolly pine plantations.

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