Contents

Mensuration Description Form

Field Procedure

Getting Started

Measure and Record

Selecting Stands and Sample Trees for Mensuration

Stand selection criteria will depend entirely on project objectives. If the data is being collected to determine site index, stands should have the following characteristics:

• even-aged (preferably 20-150 years of age)
• dominated by one tree species (or target species > 60% of basal area)
• moderately dense
• ecologically uniform site of at least 400 m²

When determining site index is not a primary objective, select the two or three largest diameter trees of each species for mensuration. If the data is being collected to determine site index, collect mensuration data on "top-height" trees that meet the following criteria:

• 100 largest diameter trees per hectare (largest 4 per 400 m² plot)
• dominant or co-dominant
• not wolf, open grown, or veteran
• straight-stemmed, free of disease, damage, and breakage
• free of suppression (above breast height)
• vigorous, with full crowns

Completing the Form

Numbered items below refer to circled numbers on the Mensuration form shown at the beginning of this section. A recommended sequence for completing the form is described under "Field Procedure."

1. Surveyor

Enter the first initial and last name of the person(s) collecting mensuration data.

2. Tree Number

Assign numbers sequentially to each tree sampled. Start with the tree closest to due north of plot centre and proceed clockwise. Numbers may be painted or tagged on trees.

3. Species

Identify tree species using the codes given in Appendix 4.1.

4. Diameter at Breast Height

Record DBH (diameter at breast height) to the nearest 0.1 cm. Measure at 1.3 m above the point of germination. On slopes, measure from the high side of the root collar.

5. Height Calculations

Record the following measurements: heights and distances in metres and slopes in percent. Tree height can be calculated in the field using equations and tables provided, or automatically using the data entry program "VENUS."

Slope to top of tree (TOP):
Enter the percent slope reading to the top of the tree, showing the sign (usually "+"). If a reading greater than 100% is obtained, move further from the tree, or upslope.

Slope to DBH or base of tree (BOT):
Enter the percent slope reading to DBH, or to the base of the tree, or to lowest visible point, including the sign ("+" or "-"). The maximum allowable is 100%.

Slope distance (SD):
Enter the distance (in metres, to one decimal) from the observer to the centre of the tree trunk, usually at breast height.

Slope (SL):
Enter the slope gradient between the observer and the tree at breast height (the slope of the measuring tape used to determine slope distance). This value is used in height calculations done by "VENUS."

Horizontal distance (HD):
Calculate this by multiplying slope distance (SD) by a slope distance factor from Table 4.1. The slope percent column in this table refers to the slope gradient measurement Slope (SL).

Height (HT):
Enter the height (m) of the measured part of the tree to one decimal, calculated as follows:
HT = [(TOP - BOT) ◊ HD] ~ 100

Height to DBH (HT TO DBH):
If the BOT reading was not taken at the base of the tree, record the height at which it was taken. This is usually DBH, but can be another value. Enter "0" if taken at the base of tree. 

TABLE 4.1. Slope distance factors

Total height (TOTAL HT) :
The total height of the tree = HT + HT TO DBH

Note the following example calculation:

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