Forest Mensuration Questions and Answers

Answer: D

The key gives all of the above.

Logs are measured by scaling, which means finding the volume or the weight of a log: log scaling by rule or tape, volume scaling and weight scaling are all used in forest produce measurement, so the three listed methods may all be said to be in use.

The printed stem is incomplete ("The most common used for measuring logs"), and no source I could reach ranks the three methods, so 'all of the above' rests on the key and on the fact that each listed method is a real scaling practice.

Answer: C

The keyed answer is Chisel.

The Swedish bark gauge measures bark thickness. A chisel-shaped end is pressed or driven through the bark until it meets the wood, and the thickness is read from a scale against a flange. That is the working part the key calls a modification of a chisel.

A hammer, a sickle and a nail do not have this form. A hammer, nail and graduated scale are listed in forestry references as a separate, simpler way of finding bark thickness, and a sickle has no part in bark measurement. A source stating the history of the instrument as a modified chisel could not be found, so the answer rests on the description of the tool and the key.

Answer: B

The keyed answer is Crown diameter.

The official key takes the dot gauge as an instrument for the crown of a tree, that is, the spread of its branches seen from above. What could not be confirmed is a reference that defines the dot gauge, so this rests on the official key.

Height is measured with instruments such as the Abney level or a clinometer, and tree girth with a tape or calipers; the depth of roots cannot be read off a standing tree.

Answer: C

Huber's method (printed Haber's) is used to measure volume.

Huber's formula estimates the volume of a log from its length and the cross-sectional area at its middle:

\[ V = A_m \times L \]

where \(A_m\) is the mid-girth sectional area. Smalian's formula, which averages the areas at the two ends, and Newton's formula are the other standard log-volume methods.

Girth and height are measured directly with a tape and a hypsometer, and weight is not what these formulae give.

Answer: B

The area needed is about 2.5 acres.

At a spacing of 2.5 m × 2.5 m, each tree occupies 6.25 m²:

\[ \begin{aligned} \text{Area} &= 1600 \times 6.25 = 10000\ \text{m}^{2} \\ &= 1\ \text{hectare} \\ &= 2.47\ \text{acres} \end{aligned} \]

since one hectare is 2.471 acres (one acre is about 4,047 m²). This rounds to 2.5 acres. The larger figures of 3.5, 4.5 and 5.5 acres would correspond to wider spacing or more trees.

Answer: C

The ratio of the mid-diameter to the DBH is the form quotient.

In forest mensuration, the form quotient compares a diameter higher up the stem (classically at half the tree's height) with the diameter at breast height (1.37 m). The closer it is to 1, the more cylindrical the bole, so it expresses stem taper.

The form factor is a different ratio: the volume of the tree divided by the volume of a cylinder with the same height and breast-height basal area. Form height is the product of form factor and height. 'Form ratio' is not the standard name of this measure.

Answer: D

The length bd is 5.50 cm.

The Christen hypsometer is held so that the top A and base B of the tree line up with its two flanges a and b. The line of sight to the top D of a staff of known length BD then cuts the scale at d. By similar triangles:

\[ \begin{aligned} \frac{bd}{ab} &= \frac{BD}{AB} \\ bd &= \frac{33 \times 4}{24} \\ &= 5.5\ \text{cm} \end{aligned} \]

The scale is graduated this way: the taller the tree, the shorter bd. 2.50, 3.50 and 4.50 cm would correspond to trees of about 53, 38 and 29 m.

Answer: C

Form class volume tables need three variables.

A form class volume table gives tree volume in terms of diameter at breast height, total or merchantable height, and form class (a measure of stem taper such as the form quotient). Adding form as a third variable makes the table usable over a wider range of tree shapes.

A local volume table uses only diameter (one variable), and a general or standard volume table uses diameter and height (two). 'All of the above' does not apply.