The Bugwood Network

Forest Management Options Evaluation for Oldfield Afforestation with Loblolly Pine Stands in the U.S. South Using WINYIELD© v. 1.11 and GaPPS© v. 4.20 Software Systems

acrobatdoc2

David J. Moorhead - Professor of Forestry, The University of Georgia
Coleman W. Dangerfield - Associate Professor of Forestry, The University of Georgia.

Paper prepared for presentation at the 7th International Conference on computers in Agriculture, October 26-30, 1998, Orlando, FL, USA. Sponsored by the American Society of Agricultural Engineering

Abstract

Two Windows®-based personal computer software systems are examined and compared when used to model and evaluate forest management options on stand volume growth, product class and yield, and financial transactions and profitability. WINYIELD v. 1.11 is a revised version of an older program based on growth equations developed some twenty or more years ago. GaPPS v. 4.20 is a program more recently developed and revised in 1997, with new estimating equation functions developed through current research. Simulations were made on loblolly pine stands established through oldfield afforestation on marginal cropland such as on the 2.218 million acres enrolled under the USDA Conservation Reserve Program (CRP) from 1985 to 1992 in the U.S. South. Comparisons were made between the programs in terms of projected yields based on the recent research data. Financial returns and wood flow impacts for the U.S. South were projected for short, pulpwood rotations. Results show an increase in modeled woodflow and estimated profitability of oldfield pines with GaPPS compared to WINYIELD. Converting current marginal cropland, through afforestation, to tree crops on 19 million acres of marginal crop and pasture land in the U.S. South offers opportunities to increase woodflow and subsequent landowner financial returns. The actual and potential future fiber and timber stumpage supply resulting from annual afforestation has an impact on the area's wood-using industries, as well as regional and state economies, and to non-industrial private forest (NIPF) landowners.

Keywords: Pine, loblolly, regeneration, tree planting, tree growth, Conservation Reserve Program (CRP), oldfield, afforestation, WINYIELD, GaPPS, wood flow, financial performance, computers.

Introduction

One of the world's largest and most productive forest resource is found in the United States of America. Of the U.S. total land area of 2,263,259,000 acres, 33 percent, or 736,681,000 acres, are forested (Wisdom, 1995). In the U.S. South, there are 211,838,000 forested acres, 40 percent of U.S. total forests (AF&PA, 1995). Southern timberland represent a significant resource to supply industry demands for fiber and solid wood products. Southern forests contain 23 percent of the U.S. softwood growing stock and 44 percent of the hardwood growing stock. Southern softwood removals comprise 53 percent of the U.S. total, and 60 percent of hardwoods (Cubbage et al., 1995).

In recent years, non-industrial private forest (NIPF) landowners in the U.S. South have experienced increased demand and prices for softwood stumpage (Dangerfield and Moorhead, 1994). Consultant, university, industry, and state foresters, as well as Cooperative Extension Service County Agents, and other natural resource professionals are asked by NIPF landowners for advice on forest management options. Specific questions typically include selections for rotation length, timing of thinnings, and projected volume production and financial performance (Dangerfield et al., 1995). To evaluate these options, the ability to manipulate current market prices, adjust site quality, species, rotation lengths, thinning regimes, and yields is important in order to evaluate management scenarios. Currently, two of the Windows®-based software programs using pine timber growth and yield information for the southern U.S. available for evaluating forest management options on financial profitability are WINYIELD 1.11 (Hepp, 1994) and GaPPS 4.20 (1997).

Description of the programs

WINYIELD (Timber Yield Forecasting and Planning Tool) was developed by Hepp (1994) at The Tennessee Valley Authority. The program is currently available through: Forest Resources Systems Institute (FORS), P.O. Box 1785 Clemson, SC 296331785 phone (864) 6567723 fax (864) 6561320 email fors_institute@clemson.edu. This program allows users to select from 14 different forest species/establishment simulators, Table 1. Inputs include rotation lengths, site index, log rule, establishment densities, thinning regimes and final harvest specifications, along with detailed financial inputs to reflect management costs, tax brackets, rates, and transactions. Output includes summarizations of volume yield, cash transactions, measures of profitability expressed as internal rate of return, composite rate of return, discounted benefit/cost ratio, annual equivalent value, soil expectation value, and net present worth. WINYIELD requires, at minimum, a 486DX PC or better, with 4 megabytes of hard disk space, 4 megabytes of RAM, Windows 3.1 and a monitor of 800 x 600 pixel resolution.

WINYIELD offers a graphical user interface, standardization of procedures, connectivity between programs, multi-tasking capability, and other features. It performs growth, yield, and financial analysis. The help system is context-sensitive. WINYIELD works with most spreadsheet, database, and word processing software. Most software suites interface with WINYIELD.

WINYIELD features include: stand level optimization; batch processing of multiple stands; output file exporting; on-line help system; conversion of old scenario files to WINYIELD format; growth and yield simulators for 13 major timber types; reports (Woodflow, Detailed-by dbh class, Financial Profitability, Cash-flow, Pine Beetle Hazard); optional stand table input (i.e., frequency of trees by dbh class); thinning regimes (specify percent of trees to remove by dbh class, or enter Low, Even (row), or High); optional bypass of simulators to input volumes manually; setup conversion factors, top diameter limits, and merchantability standards prior to simulation; enter financial transactions for single sums or periodic annuities tagged by federal income tax type; enter harvest expenses (e.g., commissions and marking fees) as a percent of harvest revenues; automatic handling of depletion, credits, amortization, and depreciation; and, detailed data structure for inputting stumpage market conditions; before and after tax discounted cash-flow and profitability analysis (NPW, IRR, CRR, AEV, BCR, SEV).

WINYIELD can be used to evaluate: growth and yield of major timber types in the U.S. South; rotation age; planting density; sand conversion; stand valuation; thinning (frequency, timing, intensity, method); effect of subsidy payments and income tax laws; cultural practices; re-creation of past stand conditions to estimate a timber basis; wildlife habitat and timber tradeoffs; natural regeneration methods; timber trespass damage amounts; appraisal of land which holds immature timber; and, forest-wide volume and value.

GaPPS (Georgia Pine Plantation Simulator) (GaPPS©, 1997) v. 4.20 was developed by Robert L. Bailey, Ph.D. and Bailin Zhou, Ph.D., and is currently available from: Forest Biometrics Consulting, 200 Robin Road, Athens, Georgia 30605. To run and install GaPPS 4.00 requires Windows® 95 or Windows NT 4.0 (Intel) operating system, 486DX or better PC. For optimal performance, 24 megabytes of RAM and 5 megabytes of free hard drive space are required.

GaPPS version 4.0 is a tool for modeling growth and yield of unthinned and thinned stands in site-prepared southern pine plantations, and financially evaluating the effects of various intensive management treatments on the stands, Table 1. It can provide per acre estimates with multiple management regime-based output windows for both slash pine (Pinus elliottii Engelm.) and loblolly pine (Pinus taeda L.) plantations. The growth and yield models used in GaPPS version 4.0 are up-to-date with current research on growth, yield and financial performance effects of current intensive pine management activities. New algorithms, which were tested by simulation, are used in GaPPS version 4.0.

GaPPS features include: individual tree volume and weight computed by user-defined product classes, such as pulpwood, chip-n-saw, and saw timber to optimize the value of each tree. Seven choices are provided for yield units. The yield units combine cords, cunits, and tons with inside and outside bark volume equations, and inside and outside bark green and dry weight equations. The unit conversion ratio for cords can be changed by the user according to volume or weight specifications. Current and future stand and stock tables are reported by product classes. Eight treatment models are provided for inputting different management regimes. A user is allowed to thin a stand up to five times. Other treatments can be integrated with thinning. All treatment parameters can be modified at any time during the simulation. Multiple output windows are provided for running multiple management regimes and switching from one regime to another. The before- and after-tax bare land value (BLV) or net present value (NPV), annual equivalent value (AEV), and internal rate of return (IRR) are reported for each regime. The user can specify a rotation age or get an optimal rotation age by maximizing a given economic analysis criterion value (BLV, NPV, or IRR). The simulation parameters can be saved. The saved parameters can be retrieved by GaPPS for future simulations. The simulation output can be saved. Saved output files can be imported to word processors and spread sheet applications.

GaPPS input simulation parameters are classified as either stand level parameters or regime level. The initial stand characteristic parameters, such as species, soil group, stand age, stand density (trees per acre, basal area per acre), and site index or dominant height, and the basic economic parameters, such as initial cash flow, stumpage price table, tax ratio, are treated as stand level parameters. The stand level parameters are shared by all regimes. Regime level parameters are those related to specific treatments, and are unique within the regime.

Methods

A common tree-growing scenario that applies well to CRP tree crops, a 20-year unthinned pulpwood rotation, is examined for loblolly (Pinus taeda L.) pine using WINYIELD and GaPPS. A Site Index (SI) of 68 feet at a base age of 25 years, found by Moorhead and Dangerfield (1995) to be representative of CRP soils, is used for all analyses. Pine stumpage prices for pulpwood of $50.00 per cord (cd), Chip N Saw (CNS) $75.00 per cd, and sawtimber $213.00 per thousand board feet (MBF) ($106 per cord) are determined using South-wide price averages from Timber Mart-South (1996). A 4 percent, uninflated discount rate is used to represent a conservative alternative investment rate and to simplify the analysis to constant dollars. Management is charged at $2.00 per acre per year. Site preparation and planting costs total $100.00 per acre, including $50 charged for competing vegetation control. Thinning costs are charged at 10 percent of harvest value. A 2.5 percent ad valorem tax at tree harvest is imposed.

Results

Woodflow and financial performance as projected by each model are specifically examined. In Table 1, a program-features comparison of WINYIELD and GaPPS, micro-computer programs for analysis of forest enterprises is presented.

WINYIELD 1.11 total volume production for the 20-year unthinned rotations is projected at 48.56 cords, Table 2. This is comprised of 39.46 cords of pulpwood and 9.10 cords of CNS. Wood-flow stand parameters at ages 10 and 20 years are detailed in Table 3. The financial profitability analysis is presented, before tax, in Table 2. Internal rate of return (IRR), before tax, is 16.8 percent with a soil expectation value (SEV) of $1,748.45. The annual equivalent value (AEV) is $69.94. WINYIELD handles both inflation and income tax treatments and produces financial performance reports before- and after-tax, and transaction and cash-flow reports. In addition, WINYIELD presents a Southern Pine Bark Beetle Hazard Rating Report that is particularly beneficial to timber managers.

GaPPS 4.20 total volume production for the 20-year unthinned rotations was projected at 55.92 cords, Table 2. This was comprised of 44.15 cords of pulpwood and 10.77 cords of CNS. Wood-flow stand parameters at ages 10 and 20 years are detailed in Table 3. The financial profitability analysis is presented, before tax, in Table 4. Internal rate of return (IRR) before tax was 17.38 percent with a soil expectation value (SEV) of $2,062.76. The annual equivalent value is $82.51. GaPPS handles income tax treatments and produces financial performance reports before- and after-tax, and transaction and cash-flow reports.

Discussion

Based on total woodflow and overall economic performance of the modeled scenarios, both programs give good results. From the perspective of available features and usability, both programs are acceptable. Differences observed, between the two programs can be described in terms of degrees of difference.

WINYIELD estimates a total wood-flow of 48.56 cords compared to 55.92 cords for the GaPPS program. The 7.36 cord difference, 15 percent, is composed of two main elements. First, estimating equations for the WINYIELD model are based on forestry research reported between 1959 and 1984. Estimating equations for the GaPPS model are based on forestry research reported between 1973 and 1997. The relatively more recent research utilized in the GaPPS model incorporates results from studies of site preparation, competition control, fertilization, and thinning. These recent research results more closely match the growth form and patterns of oldfield plantations in existence since plantings were made under the CRP.

Second, the GaPPS model incorporates treatment scenarios to model the effects of site preparation, competing vegetation control, and fertilization on subsequent tree growth. This additional modeling capability allows GaPPS to project tree growth and yield in a format more consistent with research-backed intensive forest management techniques in practice today. WINYIELD, on the other hand, has no internal mechanisms to model automatically the effects on growth, yield and financial performance of current intensive pine management activities.

The modeled scenarios were initiated with the same stand parameters of site index and trees per acre at age 10 years to allow differences to 20 years to be better observed. As observed in Table 3, the stand diameter distribution from WINYIELD centers nearly on a DBH of six inches, with a range from two to nine inches, while the GaPPS distribution centers on five inches, with a range from one to nine inches, with a height for both at 34 feet. Notably, at age 10 years the WINYIELD wood-flow is higher at 19.53 cords than is GaPPS at 11.99 cords, a 7.54 cord or 63 percent difference. However, by age 20 years the average DBH from WINYIELD is eight inches, with a range from three to eleven inches, while the GaPPS distribution centers on 8.5 inches, with a range from five to 13 inches, with a height of 57 feet for WINYIELD and approximately 66 feet for GaPPS. In addition, at age 20 years the GaPPS total wood-flow is higher at 55.92 cords than is WINYIELD at 48.56 cords, a 7.36 cord or 15 percent difference. GaPPS produces 4.69 more cords of pulpwood (12 percent) and 1.67 more cords of CNS (18 percent) than WINYIELD. Thus, at age 20 years, GaPPS projects both a higher total wood-flow and a larger average diameter classes.

With respect to wood-flow growth and yield modeling, WINYIELD is more simple and straight-forward to use than is GaPPS. However, external model adjustments with WINYIELD to increase wood-flow to match that experienced with more intensive management practices are limited mainly to adjustments in stocking density and SI. These external adjustments to model parameters may not match current research and field results as closely as do the internal model adjustments in GaPPS.

Financial performance calculated by the two programs, as represented by SEV, IRR and AEV, and reported in Table 2, differ for two main reasons. First is because of the greater proportion of more valuable CNS in the GaPPS projection, with the same adjustments of no inflation, a four percent discount rate, and tax treatments. Second is that the GaPPS scenario produces more total wood-flow in the 20-year rotation chosen.

The financial reports sections of the two models are fairly comparable with WINYIELD offering additional reports of composite rate of return and discounted benefit/cost ratio. Also, WINYIELD allows for different levels of cost and price inflation, a feature not available with GaPPS. GaPPS allows an easier and more direct computation of optimal rotations within the selected regime than does WINYIELD.

Conclusions

The features of both programs are presented in Table 1. WINYIELD offers a larger number of timber type simulators (14) than does GaPPS (4). Both are well documented, with a comprehensive manual, and are fairly easy to use. Forestry training with an understanding of economic effects is essential for use of either program.

Improvements in WINYIELD, in recent years have been directed toward making the program more user friendly, produce more flexible and detailed reports, and enhancing the interface with other software programs. In these respects, WINYIELD has made many improvements in recent years. However, major changes have not been made for WINYIELD with respect to updating its research base for underlying estimating equations to include internal adjustments for modeling the effects of intensive management activities currently in use.

GaPPS has undergone major improvements in recent years. As with WINYIELD, GaPPS has become much more user friendly, produces more flexible and detailed reports, and has enhanced interface with other software programs. In these respects, GaPPS is making more improvements, faster than is WINYIELD in recent years. However, the major change made for GaPPS has been with respect to updating its research base for underlying estimating equations to include internal adjustments for modeling the effects of intensive management activities currently in use.

References

AF&PA. 1995. U.S. forests: Facts and figures, 1995. American Forest & Paper Asso., Washington, D.C. 32 p.

Cubbage, F.W., T.G. Harris Jr., D.N. Wear, R.C. Abt, and G. Pacheco. 1995. Timber supply in the South. Journal of Forestry. 93(7):16-20.

Dangerfield, C.W. Jr., D.J. Moorhead, and D.H. Newman. 1995. Landowner opportunities for trees after the Conservation Reserve Program (CRP) ends in Georgia. The University of Georgia Cooperative Extension Service Forest Re-sources Bulletin 95-010. 23 p.

Dangerfield, C.W. Jr., and D.J. Moorhead. 1994. Loblolly pine plantation profitability: Successive pulpwood vs. multiple-product rotations. In Proceedings Eight Biennial Southern Silvicultural Research Conference. USDA Forest Service General Technical Report. SRS-1. pp. 203-208.

GaPPS©. 1997. Forest Biometrics Consulting, 200 Robin Road, Athens, Georgia 30605.

Hepp, T.E. 1994. WINYIELD 1.0, A Windows-based forest growth, yield, and financial analysis tool for southern forests. Tennessee Valley Authority, Norris, TN.

Moorhead, D.J., and C.W. Dangerfield, Jr. 1995. Evaluating the impact of tree planting under the Conservation Reserve Program in Laurens County, Georgia. In Proceedings of the 25th Southern Forest Economics Workshop. April 1995. New Orleans, LA. pp. 418-429.

Timber MartSouth. 1996. The Frank W. Norris Foundation, Warnell School of Forest Resources, University of GA, Athens, GA. Vol (#) No. (#).

Wisdom, H.W. 1995. NAFTA and GATT: What do they mean for forestry? Journal of Forestry. 93(7):11-15.

Table 1. Program features comparison of WINYIELD© v. 1.11 and GaPPS© v. 4.20, micro-computer programs for analysis of forest enterprises, 1998.

Program Features WINYIELD© v. 1.11 GaPPS©, v.4.20
I. Base scenario parameter
1. Growth simulators 1. 14 growth simulators 1. 4 growth simulators
2. Planting density 2. Variable, user specified 2. Variable, user specified
3. Site Index 3. User specified or self
    calculate
3. User specified or self
    calculate
4. Log rule 4. Scribner, Doyle, or
    International
4. Scribner
5. Stand age/stocking at start 5. Yes, both 5. Yes, both
6. Rotation age 6. User specified, or optimized
    (BLV, NPW, IRR, AEV, or
    woodflow)
6. User specified, or optimized
    (BLV, NPW, IRR, or AEV)
7. Narrative/notes 7. Yes 7. Yes
8. Regions

8. South-wide, Piedmont,
    Coastal Plain, Gulf Coast

8. Piedmont, Upper and Lower
    Coastal Plain

II. Growth and yield analysis
1. Diameter class/whole stand 1. Yes, both 1. Yes, both
2. Number of harvests 2. Up to 4 harvests 2. Up to 5 harvests
3. Harvest flexibility 3. Timing, residual density,
    method, units of measure
3. Timing, residual density,
    method, units of measure
4. Risk reduction

4. Beetle hazard rating

4. Weed competition, site prep,
    fertilization

III. Financial analysis
1. Discount rate 1. Yes 1. Yes
2. Cost/price inflation 2. Yes 2. No
3. Income taxes 3. Yes 3. Yes
4. Transactions 4. Annual and periodic 4. Annual and periodic
5. Harvest taxes and costs 5. As % of harvest value 5. No, calculate indirectly
6. Product classes 6. Up to 8 6. Up to 4
7. Profitability measures 7. NPW, IRR, CRR, AEV,
    Discounted benefit/cost ratio,
    Soil expectation value, Cash-
    flow
7. Net present value, Internal
    rate of return, Bare land
    value, Annual equivalent
    value, Cash-flow
8. Sensitivity analysis

8. Manually re-run scenarios
    with changes in input value

8. Manually re-run scenarios
    with changes in input value

IV. Report generation
1. Wood-flow 1. Summary by harvest, year,
    age, height, PAI cords,
    harvest method, residual,
    number stems, basal area,
    and product class; and,
    detailed by harvest, age,
    year, product class; diameter
    distribution, number stems,
    basal area, height, value, and
    % cut
1. Summary by harvest, year,
    age, height, MAI cords,
    harvest method, residual,
    number stems, basal area,
    and product class; and,
    detailed by harvest, age,
    year, product class, diameter
    distribution, number stems,
    basal area, height, value,
    treatment, and % cut
2. Financial profitability

2. Planning horizon, tax
    bracket,capital gains rate,
    discount rate, product prices,
    NPW, IRR, CRR, AEV,
    DB/CR, SEV, financial
    transactions, before- and
    after-tax, cash-flow by year

2. Planning horizon, tax
    bracket,capital gains rate,
    discount rate, product prices,
    NPW, BLV, IRR, AEV,
    financial transactions, before-
    and after-tax, cash-flow by
    year

V. Scenario file management
1. Save/retrieve input scenarios 1. Yes 1. Yes
2. Export data files 2. Yes 2. Yes
3. Peripheral programs 3. Loan amortization repayment
    program, Compartment
    description file builder, Text
    to DIF format conversion, and
    File display utility
3. None
4. Instruction manual 4. Detailed 4. Detailed
5. Documentation 5. Comprehensive 5.Comprehensive

Table 2. Performance comparison of WINYIELD© v. 1.0 and GaPPS© v. 4.20 for Oldfield Loblolly Pine Plantation 20-year rotation scenarios, upper coastal plain, U.S. South, 1998a

Program Wood-flow (cords)
20 yr. MAIe SEVb $/A IRRc % AEVd $/A/yr.
WINYIELD 48.56 2.4 1748.45 16.8 69.94
GaPPS 55.92 2.8 2062.76 17.38 82.51

a Uninflated, 4% discount rate. 650 trees per acre surviving after planting, SI = 68. Unthinned. Before tax. Prices: PW- 50,
   C-N-S-75; ST = 213/mbf (106/cd); big ST = 240/mbf (120/cd)
b SEV = Soil Expectation Value, calculated from perpetual rotations
c IRR = Internal Rate of Return of the investment scenario
d AEV = Annual Equivalent Value, net present worth expressed as an annual annuity
e MAI = Mean Annual Increment of wood growth, cord equivalents per acre per year

Table 3. Detailed wood-flow performance comparison of WINYIELD© v. 1.0 and GaPPS© v. 4.20 for Oldfield Loblolly Pine Plantation 20-year rotation scenarios, upper coastal plain, U.S. South, 1998.

WINYIELD - Age 10 years
DBH Stems/A. Av. Hgt. Cords
1 0
2 5 21
3 28 26
4 81 30 0.62
5 150 32 3.76
6 176 34 6.46
7 119 35 5.94
8 40 36 2.57
9 5 37 0.43
Av. 6 Tot. 603   Tot. 19.53
GaPPS - Age 10 years
DBH Stems/A. Av. Hgt. Cords
1 2 15
2 17 22
3 60 27 0.15
4 130 30 1.14
5 181 34 3.13
6 146 36 4.27
7 60 37 2.62
8 10 38 0.60
9 1 39 0.08
Av. 5 Tot. 607   Tot 11.99
 
WINYIELD - Age 20 years
DBH Stems/A. Av. Hgt. Cords
3 1 36
4 6 43 0.07
5 26 48 0.97
6 65 52 3.61
7 112 55 8.57
8 133 57 13.36
9 102 59 12.97
10 45 61 7.10
11 10 62 1.91
12
13
Av. 8 Tot. 501   Tot. 48.56
GaPPS - Age 20 years
DBH Stems/A. Av. Hgt. Cords
3
4
5 15 53 0.43
6 43 58 2.05
7 84 61 6.16
8 112 65 11.52
9 113 68 15.62
10 70 70 12.56
11 25 72 5.62
12 6 73 1.64
13 1 75 0.33
Av. 8.5 Tot. 469   Tot. 55.92

line
University of GeorgiaThe Bugwood Network Forestry Images The Bugwood Network and Forestry Images Image Archive and Database Systems
The University of Georgia - Warnell School of Forestry and Natural Resources and
College of Agricultural and Environmental Sciences - Dept. of Entomology
Last updated on Thursday, May 09, 2002 at 12:32 PM
Questions and/or comments to the