Forestry Field Excersises

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DBH- Diameter- at- Breast- Height

Measurement- taken- at- breast- height- (4.5- feet)

Avoid- tree swellings like branch- whorls

If- forked- and- fork- begins- below- 4.5- feet,- measure- each- fork- individually

If- forked- and- fork- begins- above- 4.5- feet,- measure- the- tree- as- a- whole- at- 4.5- feet

Measuring- DBH

1. D-tape- (Specially- calibrated- tape- measure)

Two-sided: one for DBH (“inches of diameter”), the other for regular inch measurements

Stand next to the trunk

Measure 4.5 feet from the ground (be sure the tape is level)

Wrap the DBH (be sure to use the proper side) around the truck at 4.5 feet

Record the inches

2. Regular measuring tape

Measure the circumference at 4.5 feet (be sure the tape is level)

Divide the circumference by π

Record the result in inches

3. Biltmore stick (Specially calibrated measuring stick)

Find the side of the stick with “Tree Scale Stick” or “Tree Diameter”

Hold the stick 25” from your eye (about an arm’s length) and 4.5 feet from the ground

Place the left edge of the stick on the left edge of the tree

Without moving your head (turn your eyes only), read the number at the top of the stick (or off “Diameter of tree (inches)” scale) that corresponds with the right edge of the tree

Height of the Tree

“Merchantable” height (commercially valuable) of a tree = the length of a tree that is usable timber

From stump height* to a cutoff point at the top

Cutoff point variable depending on species and number of limbs

*Stump height = the distance between ground level and the top of a stump. Good logging practice dictates stumps be as low as possible (preferably less than 12 inches) to reduce waste of good wood, as well as to minimize visual impact on the logging site.

Measuring the Height

1. Biltmore stick

Find the side of the stick with “Merrit Hypsometer”

Stand 66 feet from the tree

Hold the stick 25” away from your eye (at an arm’s length) parallel to the tree trunk

Align the bottom of the stick corresponding to the point where the tree would be cut (stump height)

Read the stick upward to where the tree would be cut to yield usable timber

15

Record the number to the nearest half log (if there are two separate scales on the hypsometer, be sure to read off “Qty 16 ft. logs @ 1 Chain (66ft) distance”)

Biltmore sticks measures the height of the tree in terms of the number of 16-foot logs

To convert the height to feet, multiple number by 16

2. Clinometer

Stand a convenient distance from the tree, allowing a view of the tree’s top and the bottom (Distance does not have to be 66 feet )

Be sure to stand on level ground as the tree

Record your horizontal distance from the base of the tree

Look through the viewer and find the red horizontal line (if you don’t see anything, turn it upside down)

Keeping BOTH eyes open, align the red line with the top of the tree (this may take a few seconds for your eyes to adjust)

Read the scale on the RIGHT (% scale) and record the number.

This is you’re A (+) reading in %

Align the red line with the bottom of the tree

Read the scale again. This is your B (-) reading in %

Subtract the B from the A

Multiply the % from above by the distance from the tree

To get the number of 16-ft logs, divide the height in feet by 16

Example:

A (+) = 63%

B (-) = – 7%

Distance from tree = 66’

A – B = 63 – (-7) = 70%

70% x 66’ = 46.2’

A – B = 63 – (-7) = 70%

70% x 66’ = 46.2’

Tree volume

Board feet = unit of tree volume used to estimate available lumber from a particular tree

One board foot = a slab of wood, one foot wide x one foot long x one inch thick

Calculating volume in terms of board feet

Measure the height of the tree in feet

Measure the diameter of the tree in diameter

Calculate the radius of the tree from the diameter (radius = diameter / 2)

Convert the radius into feet (radius in inches / 12 = radius in feet)

Find the area of the tree cross-section at breast height (4.5 ft) assuming the tree is a perfect circle (Area =radius x π)

Calculate the volume of the tree (Area in feet x height in feet)

Divide the volume by 4 to account for the taper of the tree

Multiple the adjusted volume by 12 (there are 12 board feet of lumber for every on cubic foot)

The final number is the number of board feet of lumber

Example:

Height of the tree = 40 feet

Diameter of the tree = 24 inches

( ) 2 12

24 ( )

x

inches Radius feet = = 1 ft

Area of the tree cross-section = 12

x 3.14 = 3.14 ft2

Volume in ft3

= 3.14 x 40 = 125.6 ft3

Volume adjustment = 125.6 / 4 = 31.4 ft3

Volume in board feet = 31.4 x 12 = 378.6 board feet 16