Measuring Height and DBH Flashcards
(20 cards)
Where do you measure a tree
At breast height 4.5’
Where do you measure a tree on a slope?
4.5’ above the high-ground side
Where do you measure a leaning tree
DBH is measured perpendicular to the axis of the tree.
Where do you measure forked trees?
When a fork is below 4.5’ it is considered two trees, measure each fork at 4.5’
When a fork is above 4.5’ it is considered a single tree and DBH is measured at the smallest diameter at or below 4.5’
Where do you measure a tree growing on an object?
DBH is measured 4.5’ above the root crown instead of 4.5’ above the forest floor
How do you measure a tree with a catface?
If the abnormality is a fairly small catface, a tape may be wrapped so that it is extended out to the normally rounded shape of the tree would have had without the catface.
The tape should not be stretched tight across the catface.
How do you measure short abnormalities?
If the abnormality is confined to a small enough area that a representative diameter can be measured above and below the abnormality, then use the averaging method.
Averaging Method
Take two diameter measurements spaced equally above and below 4.5’ and average the two measurements
Use for abnormalities on trees that prevent DBH being taken at 4.5’
(limb, catface, burl)
How do you measure long abnormalities?
If the abnormality is long enough that measurements cannot be made above and below it, or if it extends down far enough that it enters the swelling near the stump then use the half tree diameter method.
Half tree diameter method
Mark two points opposite each other on the stem and to the sides of the abnormality and then double the measurement to get DBH
How do you measure trees grown together?
Two separate trees that have grown together over time are always considered separate trees and a DBH must be measured for each.
If there is no way to get a tape between them, use the half tree diameter method or a tree caliper.
How do you measure a down tree?
Measure a down tree in the same place it would have been measured if the tree were still standing.
Merchantable height
Height to a point on the stem where merchantability is limited by size, excessive branching, defect, deformity, or log grade
Ex. Sawtimber vs Pulpwood
Sawtimber height
This is the height to the top of the sawtimber portion of a tree, limiting factor can be stem diameter but often branching or defect
4 - inch height
Height is measured to the point above which the main stem drops below 4 inches in diameter
Total height
Measure to the very tip of the tree, only for species with a will-defined tip
Slope Correction Formula
Example:
Desired horizontal distance (66ft)
Slope to the tree (35%)
Slope correction factor (1.06)
Calculated Slope Distance 66ft * 1.06 = 70ft
In order to be a horizontal distance of 66ft from the tree, the taped distance along the slope would be 70 ft.
Slope Correction
Anytime the slope is 10% (5 degrees) or greater a slope correction is required.
Height Calculation
Most accurate to measure tree height from a point either uphill from the tree or on the same contour as the tree, avoid measuring from the downhill side of the tree whenever possible
