Forestry Basics

The following three lessons will help you generally understand the "architecture" of the forest, how to measure a tree like a forester, and finally how to estimate the value of what is in your woodlot.  Please keep in mind that this brief introduction will not make you an expert. 

PLEASE consult a forestry professional before making any commitment to harvest.  

Page 25A tree may be thought of as a collection of logs and pulpwood. Small trees with dbh's ranging from 5 to 11 inches are only suitable for pulpwood. Trees greater than 11 inches dbh are suitable for sawlogs, from which lumber is cut. Typically, pulpwood is measured in 8 foot lengths and sawlogs are measured in 16 foot lengths. Because tree stems taper, the diameter decreases as you move up the stem. Once the upper stem diameter outside of the bark decreases to about 8 inches, the rest of the tree above that point is considered pulpwood. Measuring logs in a standing tree requires some practice. There are several instruments you can either buy or make for measuring the length of logs in a standing tree.

page 20Pulpwood is often measured by weight at the point of delivery. A truck containing a load of pulpwood is weighed and the weight of wood is determined by subtracting the truck weight from the total weight. Saw logs are the most valuable parts of the tree and accurate volume estimates are critical to receiving a fair price for your timber. Saw log volumes are estimated in units of board feet. Simply, a board foot is the amount of wood in a piece measuring 12 inches square and 1 inch thick.

By using stem diameters and log lengths, three different "log rules" or mathematical equations, have been developed for estimating the number of board feet in a log. The three log rules are called "Doyle," "Scribner," and "International." The landowner selling timber is advised to estimate the volume of their trees using Scribner or International. Because the Doyle log rule underestimates board feet volumes, most timber buyers prefer to use the Doyle log rule. To get a better understanding click the link (http://trace.tennessee.edu/utk_agexfores/33/)  referenced by “Understanding Log Scales and Log Rules” published by The University of Tennessee Agricultural Extension Service.

If you, as a seller, are not aware of this difference, you may settle for much less money than your timber is worth. Try to negotiate a volume estimate using either the International or Scribner rules, otherwise, make sure you negotiate a selling price that is about 40% higher per thousand board feet. Note: All of the tree value estimates in this module are based on volumes determined using the International Log Rule.


Defects cause a reduction in the amount of lumber that can be obtained from a given log at the sawmill.  Typical mills are most concerned about defects on a tree stem, such as rot, splits, cracks, and curvy forms.
 
In addition to volume loss, the value of lumber that can be sawn from a given log depends on factors such as the presence or absence of knots (caused by branches). Trees can be graded according to a system that takes into account the amount of volume and the quality of the lumber that will be lost from the log when it is sawn. Logs given "Grades" where:
  • Grade 1 logs are the straightest logs with little or no defects.
  • Grade 2 logs have some defects.
  • Grade 3 logs have the most defects and can also have somewhat curvy stems.

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