FM FM Forest Measurements & Inventory 2 — Questions and Answers
Question 1: The 'International 1/4-inch log rule' is used in timber cruising to:
- Measure the thickness of tree bark
- Estimate the board-foot volume of logs based on small-end diameter and log length (Correct answer)
- Determine the international price of timber
- Calculate the number of growth rings in a cross-section
Correct answer: Estimate the board-foot volume of logs based on small-end diameter and log length
The International 1/4-inch rule is a widely used log scale that estimates the recoverable board-foot lumber volume from a log based on its small-end diameter inside bark and length.
Question 2: In forest inventory, 'cruise intensity' refers to:
- The speed at which cruisers walk between plots
- The proportion of the total forest area sampled, expressed as a percentage (Correct answer)
- The number of cruisers assigned to a project
- The difficulty of terrain in the survey area
Correct answer: The proportion of the total forest area sampled, expressed as a percentage
Cruise intensity is the percentage of the total timber sale or stand area that is sampled, with higher intensities providing more accurate volume estimates but requiring greater field effort.
Question 3: What does 'merchantable height' mean when measuring trees for a timber sale?
- The total height of the tree from ground to tip
- The height of the usable portion of the tree stem that meets minimum size requirements for products (Correct answer)
- The height at which DBH is measured
- The height above which the tree is considered old-growth
Correct answer: The height of the usable portion of the tree stem that meets minimum size requirements for products
Merchantable height is measured from the stump to the point where the stem diameter falls below a minimum utilization standard or has significant defect, defining the recoverable portion of the tree.
Question 4: A 'Biltmore stick' is a field tool used to:
- Measure tree height using trigonometry
- Estimate tree diameter by holding the stick at arm's length against the tree (Correct answer)
- Mark trees for harvest with paint
- Assess soil depth at a given location
Correct answer: Estimate tree diameter by holding the stick at arm's length against the tree
A Biltmore stick is a graduated scale held at a fixed arm's length (25 inches from the eye) to estimate tree DBH through parallax, providing a quick but approximate diameter estimate.
Question 5: What is 'periodic annual increment' (PAI) in forest growth measurement?
- The daily growth rate of a tree during peak growing season
- The average annual volume increase over a specified measurement period (Correct answer)
- The number of new trees established per year per acre
- The annual rate of tree mortality in a stand
Correct answer: The average annual volume increase over a specified measurement period
PAI is the average annual volume, basal area, or height growth calculated by dividing total growth over a measurement period (e.g., 10 years) by the number of years in that period.
Question 6: In forest inventory, 'gross volume' differs from 'net volume' in that:
- Gross volume uses metric units while net volume uses imperial units
- Gross volume includes all wood, while net volume deducts defects, cull, and waste (Correct answer)
- Gross volume is measured before felling, net volume after
- Gross volume counts all species, net volume counts only merchantable species
Correct answer: Gross volume includes all wood, while net volume deducts defects, cull, and waste
Gross volume is the total wood volume in a tree or stand without deductions; net volume subtracts estimated losses from cull, rot, sweep, crook, and other defects to give the actually usable volume.
FM FM Forest Measurements & Inventory 2
The 'International 1/4-inch log rule' is used in timber cruising to: