Range Forest Officer recruitment (state exams) · India · State Public Service Commissions and state forest departments (e.g. MPPSC, UKPSC, UPPSC)
Original practice questions written to the published syllabus · not past papersMeasuring single trees, logs and stands: diameter, height, form, volume, biomass and growth, with the instruments and formulas used in the field.
In the exams: IFoS Forestry Paper II Section A (forest mensuration); ICAR AICE-JRF 59 Unit 4; ICAR AIEEA-PG Group 09 (forest mensuration); PRC Forest Resource Management; SAF Certified Forester; state forester and RFO exams
How our questions for Range Forest Officer recruitment spread across the units of Forest Mensuration. Difficulty: 32 easy, 24 medium, 2 hard.
| Log volume formulas: Huber, Smalian, Newton | 7 | |
| Stand measurement: stems per hectare, basal area, top height, stand volume | 6 | |
| Growth and increment: CAI, MAI and their relationship | 6 | |
| Diameter and girth measurement: breast height conventions, calipers, tapes | 5 | |
| Height measurement: principles and hypsometers | 5 | |
| Basal area and its uses | 5 | |
| Volume of standing trees: form factor and form quotient | 5 | |
| Age determination and stem analysis | 5 | |
| Site index and site quality curves | 4 | |
| Bark thickness and crown measurements | 3 | |
| Volume tables: local, general and form-class; construction and use | 3 | |
| Angle-count (Bitterlich) sampling and relascopes | 3 | |
| Tree biomass and allometric equations | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
From a point 25 m (horizontal) from a tree, the angle to the top is 40° above horizontal and to the base 5° below. What is the height?
A. 23.2 m
H = D(tan α + tan β) = 25 × (tan 40° + tan 5°) = 25 × (0.8391 + 0.0875) = 23.2 m. Subtracting the tangents gives 18.8 m and is used only when both readings are on the same side of the horizontal; using sines in place of tangents gives 18.2 m.
Why is basal area per hectare widely used to prescribe thinnings?
C. It joins tree number and size, is quick to measure, and tracks volume and competition
Basal area integrates number and size, can be estimated in seconds with an angle gauge, and is closely related to volume (G × height × form factor) and to competition. It does change after thinning — that is the point of using it.
A 6-m log has diameters of 40 cm at the base, 34 cm at the middle and 30 cm at the top. What is its volume by Newton's formula?
A. 0.560 m³
Newton: V = (g_b + 4g_m + g_t)/6 × L = (0.12566 + 4 × 0.09079 + 0.07069)/6 × 6 = 0.560 m³. Smalian gives 0.589 m³ and Huber 0.545 m³; a plain average of the three areas (0.574 m³) omits Newton's weight of 4 on the mid-section.
Why is Smalian's formula the one most used to scale logs on a landing or in a stack?
B. It needs only the two end diameters
Log ends are accessible in a stack while mid-points are often buried, so Smalian is practical. It is not exact for butt logs — it overestimates neiloid-shaped butts most — and like all three formulas it needs the length. Those ends are visible on stacked logs.
A volume table entered with dbh alone is called a:
C. Local (one-entry) table
Local tables give volume from dbh only and are valid where the height-diameter relationship matches the construction data. General tables add height; form-class tables add form class. A yield table gives stand values by age and site.
Above-ground biomass of a stand is 100 t/ha and the root-to-shoot ratio is 0.24. What is the total (above- plus below-ground) biomass?
D. 124 t/ha
Below-ground biomass = 100 × 0.24 = 24 t/ha; total = 124 t/ha. Subtracting gives 76; dividing by the ratio gives 416.7.
For young pines that produce one branch whorl each year, a quick estimate of age is obtained by:
D. Counting the branch whorls or whorl scars along the stem
Many young pines and spruces form one whorl of branches per year, so whorl counts give age. The method fails in species with several flushes per year and in old trees where lower whorls are lost.
The main product of stem analysis used in site-quality work is:
A. A height-age curve built from the ages at which the stem reached each disc
Stem analysis gives the age at which the tree reached each sampled height; plotting heights against these ages gives the tree's height-growth history, the raw material of site-index curves.
A stand had 165 m³/ha at 30 years and 240 m³/ha at 40 years. What was its periodic annual increment between those ages?
B. 7.5 m³/ha/yr
PAI = (240 − 165) / 10 = 7.5 m³/ha/yr. 6.0 is the MAI at 40 (240 / 40) and 5.5 the MAI at 30 (165 / 30); 75 is the total periodic increment, not per year.
In Indian and British yield tables, Site Quality I denotes:
D. The best, most productive site
In these conventions quality classes run from I (best) downwards; classes are defined by ranges of top height at given ages.
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