CF Forest Resource Measurement and Inventory 2 — Questions and Answers
Question 1: In a variable-radius plot using a 10-factor prism, a tree is counted if its DBH in inches is at least how many times the horizontal distance in feet from plot center?
- DBH ≥ distance / 10 (Correct answer)
- DBH ≥ distance × 10
- DBH ≥ distance / BAF
- DBH ≥ distance × BAF
Correct answer: DBH ≥ distance / 10
With a 10-BAF prism, a tree is tallied when DBH (inches) divided by horizontal distance (feet) equals or exceeds 1/10 (i.e., DBH ≥ distance/10 using the limiting distance formula).
Question 2: Which timber cruise method distributes sample points in a systematic grid pattern across the entire stand?
- Random sampling
- Stratified random sampling
- Systematic sampling (Correct answer)
- Cluster sampling
Correct answer: Systematic sampling
Systematic sampling places sample points at uniform intervals across a grid, ensuring even spatial coverage of the stand.
Question 3: The term 'merchantable height' in timber measurement refers to the length of the bole measured to:
- The absolute tree top
- The point where diameter inside bark reaches a minimum utilization standard (Correct answer)
- 4 feet above the stump
- The base of the live crown
Correct answer: The point where diameter inside bark reaches a minimum utilization standard
Merchantable height is the usable stem length up to the minimum top diameter inside bark acceptable for a given product standard.
Question 4: A stand has 80 trees per acre with an average basal area of 0.9 sq ft per tree. What is the stand basal area per acre?
- 52 sq ft
- 62 sq ft
- 72 sq ft (Correct answer)
- 82 sq ft
Correct answer: 72 sq ft
Stand basal area = trees per acre × average BA per tree = 80 × 0.9 = 72 sq ft per acre.
Question 5: Which of the following is the primary purpose of stratification in a forest inventory?
- To reduce total sampling cost by eliminating plots
- To reduce variance within groups and improve precision for a given sampling effort (Correct answer)
- To ensure all species are equally represented
- To avoid measuring small-diameter trees
Correct answer: To reduce variance within groups and improve precision for a given sampling effort
Stratification groups similar units together, reducing within-stratum variance and increasing overall inventory precision without adding plots.
Question 6: A Biltmore stick is primarily used in the field to estimate:
- Tree height using trigonometry
- DBH by holding the stick at arm's length against the tree (Correct answer)
- Basal area factor for prism selection
- Merchantable log volume directly
Correct answer: DBH by holding the stick at arm's length against the tree
A Biltmore stick is a graduated stick held at a fixed arm's length to optically estimate DBH based on parallax principles.
Question 7: In forest mensuration, the 'form factor' of a tree corrects volume estimates by accounting for:
- Species-specific wood density differences
- Deviation of the actual stem shape from a perfect cylinder (Correct answer)
- Crown ratio and live crown length
- Stump height relative to total height
Correct answer: Deviation of the actual stem shape from a perfect cylinder
Form factor expresses the ratio of actual stem volume to that of a cylinder with the same basal area and height, correcting for taper.
CF Forest Resource Measurement and Inventory 2
In a variable-radius plot using a 10-factor prism, a tree is counted if its DBH in inches is at least how many times the horizontal distance in feet from plot center?