Forest Mensuration and Inventory
What this domain tests
Inventory design, point and plot sampling, volume and weight estimation, growth and yield, and error propagation. Expect arithmetic, not just definitions.
Core rules
- Point sampling: basal area per acre = number of in trees times BAF. Limiting distance in feet = 2.75 times DBH in inches for a 10 BAF prism (factor = 8.696 divided by the square root of BAF).
- Trees per acre represented by one in tree = BAF divided by (0.005454 times DBH squared).
- Fixed-radius plots require a plot size that lets borderline trees be decided consistently; check borderline trees by slope-corrected distance from plot center.
- Volume equations are local or standard; merchantability depends on top diameter, stump height, and minimum log length. Board-foot rules (Doyle, Scribner, International quarter-inch) disagree most on small logs: Doyle under-runs small timber, International is closest to cubic recovery.
- Sampling error varies with one over the square root of n: quadrupling plots halves the standard error. Yield tables are not substitutes for a cruise when the sale is valuable.
Worked example
A 20 BAF prism cruise counts 12 trees in a plot; basal area = 12 times 20 = 240 square feet per acre. One counted 14-inch tree represents 20 divided by (0.005454 times 196) = 20 divided by 1.069 = 18.7 trees per acre. If the 12 counted trees average near 15 trees per acre each, the implied stand is roughly 180 trees per acre - a useful sanity check on the tally.
Traps
Mixing point and fixed plots in one summary; entering DBH in centimeters into an imperial formula; using inside-bark diameters for outside-bark volume; confusing board feet with cubic feet; forgetting to check borderline trees with a wedge and tape.