VARDAMAN VIRTUAL FORESTRY COMPANY

The Most Direct Link to Knowledge Workers in the Southeast Forest Economy

TIMBER ESTIMATES TO SELL YOUR TRACT OR TO APPRAISE OTHERS

PTAEDA2.1V, which will soon be available in Windows version on www.vardaman.com, is primarily useful for predicting growth of loblolly-pine plantations, but one of the steps in doing this reveals important truths about timber estimates. You can see that this common term covers a multitude of sins.At the time of the first thinning, the model reports the number, volume, and quality of trees by one-inch DBH classes and allows you to show on the screen a map of them plotted to scale.

These data for a SI-70, 14-year-old plantation with the original trees planted seven feet apart in horizontal rows nine feet apart appear in the background of both maps below. Pulpwood-quality trees are crosshatched and appear darker; sawtimber-quality trees are lighter with vertical stripes only. The plantation in both maps is 180 feet up-and-down and 140 feet side-to-side and contains 25,200 square feet or or 0.579 acre.There are 148 pulpwood-quality + 175 sawtimber-quality = 323 trees total, a typical stand in present-day CRP plantations.

The four circles on this map depict the borders of 1/10-acre plots typically used by timber estimators. Many estimators measure samples of 10% or 20% of the area. A single one of these plots contains more than 17% of total area; the four combined contain 69.1%. The only way you could get closer to the true volume would be to measure 100% of the trees, which is what we do on all sawtimber sales.

>Acting as foresters in the stand, we counted the trees on each plot to be as follows:

These are the trees on 0.4 acre; therefore, the estimated numbers on the entire 0.579-acre plot are 149 pulp-quality + 162 saw-quality = 311. If we had been satisfied with a 15% estimate and had used only a single plot, you can see that the error would have been much larger.

The sixteen circles on this map contain 1/40-acre each, another typical size.

Acting as foresters again, we counted the trees on each plot to be as follows:

Once again these are the trees on 0.4 acre; therefore, the total numbers estimated by this sampling method are 139 pulp-quality + 153 saw-quality = 292.

The cause of the estimator's problem in arriving at the correct number is the irregular distribution of the trees by DBH and quality between different parts of even this small area. This typical situation in CRP plantations of this age surprises those to whom the plantations seem so uniform. After all, the trees are the same species and age, came from the same nursery, and were probably planted on the same day by the same man.Just imagine how much more variable is the typical natural stand of sawtimber with 30-50-year old pines and four hardwood species groups.

Finally, if you want to see how tricky it is to count trees on a plot, ask a friend to count the trees on these plots, and see how her numbers compare with yours. You will then not be surprised how easy it is for a forester to miss a tree on a plot in the woods. If these were trees to be offered in your sale, would you now require measurement of a 100% sample? If you don't, you will never know what you sold.

You can understand why professional buyers or investors disregard such meaningless statements as "estimated by a registered forester to contain ??? MBF of sawtimber." They insist on knowing who made the estimate and what method he used.