Total tree height is the distance in feet from the ground to the top of a tree. This height measurement is used mainly in conjunction with tree age to judge site quality, which is explained later in this chapter.

Merchantable tree height is the length of the main stem from the top of the expected stump to the upper limit of utilization in the tree. Stump height normally is 6 inches for softwood species and 12 inches for hardwood species, but varies depending on the volume table you use. The upper limit of utilization is where the main stem reaches a minimum usable top diameter, a main fork, or a serious defect such as a hole or a point of decay, or where excess limbs occur. Standards for merchantability vary widely depending on local product markets. The usual minimum top diameter inside the bark (DIB) is 4 inches for pulpwood, 8 inches for sawlogs, and 10 inches for veneer logs. Merchantable tree height usually is measured in 8-foot lengths called half-logs, sticks, or bolts, but may be measured to the nearest 2 feet on high-value trees. Your forester will determine a tree?fs height using a hypsometer, clinometer or a laser height finder (Figure 2-2). Measure the height of a leaning tree from a viewpoint where the tree is leaning to the left or the right, not from where it is leaning toward or away from you.

You can make a simple hypsometer by placing marks at 4-inch intervals along a stick or lath. Each mark represents one 8-foot bolt when the stick is used as follows:
  1. Stand 50 feet from the tree center in a direction such that the tree does not lean toward or away from you.
  2. With the stick in hand, extend your arm out 25 inches from your eye. Hold the stick vertically and in line with the stem of the tree being measured.
  3. Find the upper limit of utilization. (Upper limit of utilization is different forest products. This is the minimum diameter at the small end of the log that a mill will accept to use that log for a certain product.) Remember that point.
  4. Raise or lower the stick as needed until you can sight along the bottom of the stick to stump height. Then, moving your eyes, not your head, look up and read the stick measurement that corresponds to the upper limit of utilization point. Count the number of bolts between the stump and the merchantable height and record this number.

If you are unable to get a good sight on the tree from a distance of 50 feet, stand 25 feet from the tree and divide the resulting height measurement by two.