GLOSSARY FOR TIMBERLAND MANAGEMENT SIMULATOR

 Stand Parameters

 Growth and  Yield Models:  The first growth and yield model for loblolly pine plantations with site preparation for cutover land is based on the following publication:

 Harrison, W. M. and Bruce E. Borders. 1996. Yield prediction and growth projection for site-prepared loblolly pine plantations in the Carolinas, Georgia, Alabama and Florida. PMRC technical report, University of Georgia, 1996-1.

The second growth and yield model for loblolly pine plantations for cutover land is based on the following publication:

 Lenhart, J. D., 1996, Total and partial stand-level yield prediction for loblolly and slash pine plantations in East Texas. SJAF 20(1) 1996.

Note: The first model is recommended to use for stands with site preparation and the second model is recommended to use for stands without site preparation. Also, the original Lenhart paper does not include thinning models. Therefore, do not use this model when thinning is involved in stand management. 

Site Index:  tree height in feet at a certain age.  The default site index is based on age 25, but it can be  changed to age 50 on the simulator by checking the radio button for “Age 50”.

Initial Stand Age:  the starting age for a simulation. If the initial stand age is different from 1, the calculated bare land value is not a meaningful number because the concept of bare land value is based on constant series of rotations but the scenario does not describe a full rotation.

Initial Density (Trees/Acre):  trees per acre at the initial stand age. It should represent the number of surviving trees at the time. For example, if the stand is planted with 800 trees but we know that only 550 trees will survive by the end of the year, then the initial density should be 550 trees not 800 trees.

Financial Parameters

 Discount Rate:  in this case, the interest rate at which the costs and revenues are discounted.  The real discount rate, which does not include inflation, should be used.  For a discussion about the relationship between the two, click here.

Wood Price by Type:  prices of the three most common commercial wood types (pulpwood, chip-n-saw, or sawlog) may be entered.  On the simulator, sizes of the three types can be defined by changing the minimum top diameter and the minimum DBH (diameter at breast height).

Green tons outside of bark:  the default unit for wood volumes in this simulator.  $/green tons outside of bark is the default unit for wood prices in this simulator. Prices in other units should be converted to the default unit before used in the model. Conversion factors can be found in some publications such as Texas Timber Price Trends,  Timber Mart-South, or Service Forester's Handbook by Southern Region, USFS (Miscellaneous Report R8-MR 11.  The first two publications are also sources for current and historical price information.

What are the stumpage prices that should be used in the model? Theoretically, it should be the real prices of the stumpage at the time of harvest. When simulating management plans, such information is not available. In this case, appropriate prices to be used  are prices representing future price trends from some theoretical, or empirical evidences or some sort of recent historical averages, such as last three or five years average prices. Since timber prices are very seasonal and cyclical, the most recent prices, such as last month's timber prices, may not be the best indicators of future price  trends. Since real discount rate is used for the simulation, real prices, not nominal prices, should also be used.

Regeneration Costs:  costs for site preparation, seedlings and planting, or any other non-recursive costs that are incurred in the first year of the stand.

Annual Costs:  costs of the same amount that are incurred every year (periodic constant payments); for example, property taxes, management overhead costs, or land rent etc.

Other Costs:  non-recursive costs other than regeneration costs and regular annual costs.  Specify the stand age at which the cost occurs, the type of the cost and the amount of the cost.  Unlike the timberland investment calculator, all costs should be entered as positive numbers in the timberland management simulator. Costs for harvesting the trees , (i.e., consulting forester fees) should not be included as Other Costs because they will be specified as a percentage of the harvest revenues later.  A maximum of five cost items can be entered. 

Costs for intensive management treatments such as fertilization should not usually be used since the growth and yield model currently does not have the growth response to such intensive treatments explicitly included in it. However, the costs for incorporate intensive management treatments can be incorporated into the analysis if you already know the growth response of the treatments in terms of increased site index and enter both costs for intensive management treatments and the changed site index accordingly.

Other Revenue:  non-recursive revenues other than those generated from the stumpage value of the trees.  Examples are hunting lease fees and non-timber products like mushrooms.  A maximum of five revenue items can be entered.

Harvest Regime:  a maximum of three thinnings and one final harvest can be specified in a harvest regime.  Thinnings are optional in the model.

Stand Age:  age of the stand at which a thinning or final harvest occurs.  Stand ages for thinnings and final harvest must be in ascending order:  First Thinning, Second Thinning, then Third Thinning.  Do not enter a value in the Third Thinning category or the Second Thinning one if they do not apply.  For example, there should not be a positive value for the stand age for the third or second thinning if the stand age for the first thinning is left empty.  If the stand age for the final harvest is left empty, an optimal age will be chosen by the program by maximizing the bare land value.

Harvest Intensity (% of Trees Cut):  the percentage of total trees being cut at each thinning and the final harvest.  All thinnings are assumed to cut trees evenly, so that the basal area and volume being harvested is proportional to the percentage of trees being cut.  There are two reasons for doing this.  First, for pine plantations, diameter distributions are more regular than natural stands.  An even cut assumption will not introduce a high bias.  Second, it simplifies the task for the users of this program by eliminating the need for specifying the often arbitrary selected cut.

Expense As % of Harvest Value: This item records the expenses for planning the thinning or final harvest by consulting foresters based on the percentage of the harvest value. The expenses as the percentage of the harvest value usually decrease with the increase of tree sizes of the stand because the value of the trees cut per acre increase with the increase of tree sizes.  

Other Harvest Information:  These columns show basal area, volume, and values being cut and left for each thinning and the final harvest.  The volume may be higher than the summation of the volumes for the three wood types.  This can occur because the total includes volumes that do not meet the minimum merchantability standard in terms of minimum top diameter and DBH, which can be specified by the user.