'Precision Forestry' detailed at field day

By LYNN MONTGOMERY | East Texas Edition

One of the foresters with the Texas Forest Service answers questions posed by one of the East Texas Forestery Field Day attendees. Several exhibitors were available with information at the annual event. -Staff photo by Montgomery

July 10, 2003 -- People attending the 2003 Annual East Texas Forestry Field Day in Overton June 19 were treated to topics concerning Precision Forestry.

Precision Forestry uses the latest technology sensing and analytical tools to collect highly accurate, repeatable measurements, actions, and processes of forested landscapes.

Forest inventories: New tools for old techniques was one topic presented by Dean Coble, Stephen F. Austin State University assistant professor of Biometrics.

Coble began his speech by giving a forest inventory background.

The purpose of a forest inventory background, Coble explained, is to produce precise estimates of volume.

"There are variables that affect precision: tally, diameter, height and taper.

"Tally (counting the trees) is the most important," the biometrician said. "Correct tree tallies are the most important consideration in a good inventory.

"If you are going to measure something, the most important (thing to measure) is rather the tree is or is not in the plot," Coble continued. Using an example, Coble pointed out missing a 12-inch, four-log pine tree, could result in loosing $2,763.

The common reasons for missing trees, according to the professor, include it is easy to miss large trees far away from point center, easy to miss trees in heavy brush, easy to miss trees behind other trees, failure to correct for slope, prisms/angle gauges do not work well with out-of-round trees (for example: hardwoods), and pushing (not holding the point sampling instrument correctly) the point.

Coble said, "Never count every other tree or guess. You should always measure the limiting distances to borderline tally trees to determine if they are 'in' or 'out.'"

An incorrect diameter estimate is more costly than an incorrect height estimate.

"The difference is volume for tallying a 12-inch tree in the 14-inch class (assuming a three-log height) would be board-feet for a 12-3 tree is 57. Board-feet for a 14-3 is 104. The percent difference is 45 percent. On the other hand, if you know the diameter is 14 inches; but you guess on the height, your percentage would not be as bad. Say you guess the tree to be three-log high and it is four-log high, then board-feet for 14-3 tree is 104; board-feet for 14-4 is 114. Percent difference is 9 percent."

The professor stated diameter tapes and biltmore sticks assume a tree is round. "Thus, they will always over-estimate the diameter, and therefore basal area and volume, for out-of-round trees."

He suggested using a caliper and taking the arithmetic or geometric means when cruising a tract of out-of-round trees, such as bottomland hardwoods.

A new instrument the biometrician uses when cruising is an Impulse Laser which "has tripled his production" in tree inventory.

"The Impulse Laser is extremely fast and accurate. It measures heights, slopes and horizontal distances. You can use it for closed traverses and it only requires one unit. This unit will bounce the laser beam from tree to tree. The disadvantage is it doesn't give accurate readings in heavy brush," Coble said.

The Impulse Laser cost around $2,500.

Coble concluded with new tools, such as Haglof Vertex III Hypsometer, data recorder, GPS unit. are improving precision and efficiency.

"Future trends will improve technology and inventory will become even faster."