B.F. Bachelor of Forestry Bachelor of Forestry Forest Mensuration 4 — Questions and Answers
Question 1: The 'site index' of a forest stand is most commonly defined using which reference age?
- 10 years
- 25 years
- 50 years (Correct answer)
- 100 years
Correct answer: 50 years
Site index is most commonly expressed as the expected height of dominant and codominant trees at a base age of 50 years for many species.
Question 2: What does the term 'merchantable height' refer to in timber measurement?
- The total height from ground to tree tip
- The height of the tree above the root collar
- The height of the usable stem from the stump to a minimum top diameter (Correct answer)
- The height of the live crown base
Correct answer: The height of the usable stem from the stump to a minimum top diameter
Merchantable height is the length of trunk from the stump to a specified minimum top diameter (e.g., 4 inches) that yields usable timber.
Question 3: Which of the following is a major advantage of using point sampling (variable plot) over fixed-area plot sampling?
- It requires less mathematical calculation
- Larger trees are sampled with higher probability, reducing variance in volume estimates (Correct answer)
- It eliminates the need for measuring tree diameters
- It works only in even-aged stands
Correct answer: Larger trees are sampled with higher probability, reducing variance in volume estimates
Point sampling gives larger trees a higher probability of selection, which reduces estimation variance for volume since large trees contribute most to stand volume.
Question 4: The 'quadratic mean diameter' (QMD) of a stand is calculated as:
- The arithmetic average of all tree diameters
- The square root of the average of squared diameters (Correct answer)
- The median diameter of the diameter distribution
- The diameter of the largest tree divided by two
Correct answer: The square root of the average of squared diameters
QMD is the diameter of a tree of average basal area, computed as the square root of the mean of all individual tree diameters squared.
Question 5: Which log rule is considered the most accurate and is often used as a standard for comparison?
- Doyle rule
- Scribner rule
- International ¼-inch rule (Correct answer)
- Hoppus rule
Correct answer: International ¼-inch rule
The International ¼-inch rule is widely regarded as the most accurate log rule because it accounts for saw kerf and taper using a formula derived from actual milling studies.
Question 6: In a taper equation model, what is the dependent variable being predicted?
- Total tree height
- Diameter at any given height along the stem (Correct answer)
- Volume of individual logs
- Number of logs per tree
Correct answer: Diameter at any given height along the stem
A taper equation predicts the inside-bark or outside-bark diameter at any specified height along the stem from known DBH and total height.
Question 7: A 'cruise intensity' of 10% in a timber sale area of 200 acres means the cruiser will measure trees on:
- 10 acres
- 20 acres (Correct answer)
- 50 acres
- 100 acres
Correct answer: 20 acres
A 10% cruise intensity means 10% of the total area is sampled, so 10% of 200 acres = 20 acres worth of plots are established.
B.F. Bachelor of Forestry Bachelor of Forestry Forest Mensuration 4
The 'site index' of a forest stand is most commonly defined using which reference age?