SAF Certified Forester (CF) · USA · Society of American Foresters
Original practice questions written to the published syllabus · not past papersThe intermediate treatments between regeneration and harvest that shape a stand's growth, quality and health.
In the exams: ICAR AICE-JRF 59 Unit 2 (tending: weeding, cleaning, climber cutting, mechanical, ordinary, crown and selection thinning, improvement felling, pruning, girdling); IFoS Forestry Paper I Section A (establishment and tending)
SAF Certified Forester; North American and other professional forester examinations
Intermediate treatments: release, precommercial and commercial thinning, low, crown, selection and crop-tree thinning, stand density index and density management, pruning for clear wood, and fertilisation response and economics.
How our questions for SAF Certified Forester spread across the units of Stand Tending, Thinning & Pruning. Difficulty: 4 easy, 10 medium, 6 hard.
| Thinning: objectives and effects on growth | 3 | |
| Thinning grades and thinning schedules | 3 | |
| Release treatments and competition control | 3 | |
| Fertilisation of established stands | 3 | |
| Thinning methods: mechanical, ordinary (low), crown, selection | 2 | |
| Pruning: natural and artificial; timing and lift | 2 | |
| Weeding and cleaning | 1 | |
| Climber cutting | 1 | |
| Improvement felling and salvage cutting | 1 | |
| Girdling and other stand-improvement methods | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
In reduced-impact logging, why are climbers cut on trees to be felled, ideally six months or more before felling?
D. Dead climbers no longer bind crowns together, so felling damages fewer neighbours and is safer
Climbers tie crowns together; a felled tree drags neighbours down and endangers workers. Cutting them well ahead lets them die and weaken. The other reasons are invented.
Further reading: Smith et al., The Practice of Silviculture (9th ed., 1997); Nyland et al., Silviculture (3rd ed., 2016); Khanna, Principles and Practice of Silviculture
A plantation has 1,111 trees/ha on a square spacing and a top height of 15 m. What is its relative spacing (Hart-Becking index)?
B. 20 per cent
Spacing = √(10,000 ÷ 1,111) = 3.0 m; relative spacing = 3 ÷ 15 × 100 = 20%. 500% divides top height by spacing (15 ÷ 3 × 100); 0.2% forgets to multiply by 100; 3% is the spacing alone.
Further reading: Smith et al., The Practice of Silviculture (9th ed., 1997); Nyland et al., Silviculture (3rd ed., 2016); Khanna, Principles and Practice of Silviculture
Reineke's stand density index rests on the observation that in fully stocked stands, log trees per hectare declines with log quadratic mean diameter with a slope of about:
A. −1.605
Reineke found a slope of about −1.605 between log N and log Dq. −3/2 is Yoda's self-thinning slope for mean plant mass against density, not diameter; a positive slope would mean more trees as they grow larger.
Further reading: Smith et al., The Practice of Silviculture (9th ed., 1997); Nyland et al., Silviculture (3rd ed., 2016); Khanna, Principles and Practice of Silviculture
Why is mechanical thinning often used for first thinnings in plantations?
A. Trees are still fairly uniform, produce has little value, and machines need access racks
Uniform young stands, low-value produce and the need for racks favour simple row or spacing thinning. It does not select the best trees, is not legally required, and does not target dominants.
Further reading: Smith et al., The Practice of Silviculture (9th ed., 1997); Nyland et al., Silviculture (3rd ed., 2016); Khanna, Principles and Practice of Silviculture
Under British management tables, the marginal thinning intensity is set at 70 per cent of yield class per year. What is it for yield class 14?
A. 9.8 m³/ha/yr
MTI = 0.7 × 14 = 9.8 m³/ha/yr. 14 is the yield class itself; 4.2 is 30% of it; 20 divides 14 by 0.7.
Further reading: Smith et al., The Practice of Silviculture (9th ed., 1997); Nyland et al., Silviculture (3rd ed., 2016); Khanna, Principles and Practice of Silviculture
A stand of yield class 14 is thinned at the marginal thinning intensity (70 per cent of yield class per year) on a five-year cycle. About how much volume is removed at each thinning?
D. 49 m³/ha
MTI = 0.7 × 14 = 9.8 m³/ha/yr; over five years 9.8 × 5 = 49 m³/ha. 9.8 is the annual figure; 70 uses the yield class × 5; 98 uses a ten-year cycle.
Further reading: Smith et al., The Practice of Silviculture (9th ed., 1997); Nyland et al., Silviculture (3rd ed., 2016); Khanna, Principles and Practice of Silviculture
Which measure is commonly used outside India to express thinning intensity numerically?
A. Residual basal area, SDI or trees per hectare after thinning
Numerical targets such as residual basal area, SDI or stems per hectare are common. Crown-class grades are the Indian system; paint colour and number of thinnings do not express intensity.
Further reading: Smith et al., The Practice of Silviculture (9th ed., 1997); Nyland et al., Silviculture (3rd ed., 2016); Khanna, Principles and Practice of Silviculture
A pruned log is 50 cm in diameter and its defect (knotty) core is 20 cm in diameter. What share of the cross-section area is clear wood?
A. 84 per cent
Clear share = 1 − (20 ÷ 50)² = 1 − 0.16 = 0.84. 60% uses a linear ratio (1 − 0.4); 16% is the core share; 40% is the diameter ratio.
Further reading: Smith et al., The Practice of Silviculture (9th ed., 1997); Nyland et al., Silviculture (3rd ed., 2016); Khanna, Principles and Practice of Silviculture
In North American terminology, the three kinds of release treatment are:
C. Weeding, cleaning and liberation
Release frees a young crop from competing herbs and shrubs (weeding), same-age competitors (cleaning) and older overtopping trees (liberation).
Further reading: Smith et al., The Practice of Silviculture (9th ed., 1997); Nyland et al., Silviculture (3rd ed., 2016); Khanna, Principles and Practice of Silviculture
How much urea (46 per cent N) supplies 150 kg of nitrogen per hectare?
A. 326 kg/ha
Product = 150 ÷ 0.46 = 326 kg urea. 69 multiplies by 0.46; 150 confuses nutrient with product; 196 adds 46.
Further reading: Smith et al., The Practice of Silviculture (9th ed., 1997); Nyland et al., Silviculture (3rd ed., 2016); Khanna, Principles and Practice of Silviculture
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