B.S.F. or B.Sc.F. Bachelor of Science in Forestry Wood Science and Timber Technology 1 — Questions and Answers
Question 1: Which anatomical feature distinguishes hardwoods (angiosperms) from softwoods (gymnosperms) in wood structure?
- Presence of resin canals
- Presence of vessels (pores) for water conduction (Correct answer)
- Absence of annual rings
- Presence of bordered pit pairs in tracheids
Correct answer: Presence of vessels (pores) for water conduction
Hardwoods contain specialized vessel elements for water conduction, visible as pores in cross-section, which are absent in softwoods.
Question 2: What is 'wood specific gravity' (relative density) and why does it matter to forest products?
- The ratio of wood density to the density of water, indicating strength and stiffness properties (Correct answer)
- The weight of a cubic foot of green wood
- The ratio of heartwood to sapwood in a stem
- The moisture content at which wood begins to shrink
Correct answer: The ratio of wood density to the density of water, indicating strength and stiffness properties
Specific gravity compares wood density to water; higher specific gravity generally correlates with greater mechanical strength, stiffness, and hardness of the wood.
Question 3: The fiber saturation point (FSP) in wood is significant because:
- Above it, wood continues to gain strength as moisture increases
- Below it, wood begins to shrink, swell, and change mechanical properties as moisture changes (Correct answer)
- It marks the point at which wood becomes combustible
- It is the moisture content at which wood is sold commercially
Correct answer: Below it, wood begins to shrink, swell, and change mechanical properties as moisture changes
Below the FSP (~28–30% moisture content), free water is gone and changes in bound water cause shrinkage, swelling, and changes in strength.
Question 4: In US lumber grading, 'green lumber' refers to wood that:
- Has been kiln-dried to below 15% moisture content
- Has a moisture content above 19% (not yet seasoned) (Correct answer)
- Has been pressure-treated with preservatives
- Is cut from young second-growth forests
Correct answer: Has a moisture content above 19% (not yet seasoned)
Green lumber retains high moisture content (above 19%) from the living tree and will shrink and potentially warp as it dries to equilibrium moisture content.
Question 5: Lignin in wood cell walls serves primarily to:
- Store carbohydrate energy for the tree
- Provide tensile strength along the grain
- Bind and stiffen the cellulose framework, providing compressive strength and decay resistance (Correct answer)
- Transport water through the sapwood
Correct answer: Bind and stiffen the cellulose framework, providing compressive strength and decay resistance
Lignin is a complex polymer that cements cellulose microfibrils together, giving wood its compressive strength and resistance to biological degradation.
Question 6: The difference between 'heartwood' and 'sapwood' in a tree stem is best described as:
- Heartwood conducts water; sapwood is dead and non-functional
- Sapwood is the outer, physiologically active zone that conducts water; heartwood is the inner dead zone often darker in color (Correct answer)
- Heartwood is always softer than sapwood
- Sapwood contains more resin than heartwood in all species
Correct answer: Sapwood is the outer, physiologically active zone that conducts water; heartwood is the inner dead zone often darker in color
Sapwood is the living outer wood that conducts water from roots to leaves; heartwood is the inner core of dead cells that often accumulates extractives and is usually darker and more durable.
B.S.F. or B.Sc.F. Bachelor of Science in Forestry Wood Science and Timber Technology 1
Which anatomical feature distinguishes hardwoods (angiosperms) from softwoods (gymnosperms) in wood structure?