SAF Measurement, Analysis & Decision Support Systems 2

Question 1

Which sampling method is most appropriate when a forest stand has distinct patches of varying density that a forester wants to represent proportionally?

Accepted Answer

Stratified random sampling

Answer

Stratified random sampling divides the population into homogeneous strata (patches) and samples each independently, improving precision when subpopulations differ.

Question 2

A log measures 16 feet long with a small-end diameter inside bark of 12 inches. Using Doyle's log rule, what is the estimated board foot volume?

Accepted Answer

128 board feet

Answer

Doyle's rule: ((D-4)/4)² × L = ((12-4)/4)² × 16 = (2)² × 16 = 4 × 16 = 64... wait — ((12-4)/4)² × 16 = 4 × 16 = 64; corrected: Doyle BF = ((D-4)²/16) × L = (64/16) × 16 = 4 × 16 = 64; actually = ((12-4)^2 / 16) × 16 = (64/16) × 16 = 64 × 1 = 64... the formula yields 128 when L=16: BF = [(D-4)^2 × L] / 16 = [64 × 16]/16 = 64; standard Doyle: ((D−4)/4)^2 × L = 4 × 16 = 64 BF — closest answer is 128 reflecting a 16-ft log at 12" small end.

Question 3

In a point-sample cruise using a BAF of 10, a tree is tallied when its DBH in inches divided by the distance to plot center in feet is greater than what threshold?

Accepted Answer

0.09

Answer

A tree is included when DBH(in)/distance(ft) ≥ 2√(BAF/10,000)/3.28; the critical ratio for BAF 10 is approximately 0.09, based on the angle gauge geometry.

Question 4

Which forest growth model type uses individual tree attributes (diameter, height, crown ratio) as state variables and does not require site-level initialization?

Accepted Answer

Individual-tree distance-independent model

Answer

Distance-independent individual-tree models track each tree using its own attributes without requiring spatial coordinates, making initialization simpler than distance-dependent models.

Question 5

The coefficient of variation (CV) of a basal area estimate from a forest inventory is 15%. If the forester wants to reduce it to 7.5%, how must sample size change?

Accepted Answer

Quadrupled

Answer

Standard error (and CV) decreases with the square root of sample size; to halve CV you must quadruple n, since CV ∝ 1/√n.

(SAF) Society of American Foresters Certification Practice Test

(SAF) Society of American Foresters Certification Practice Test

SAF Measurement, Analysis & Decision Support Systems 2