What is Wood?

Wood is an organic material that forms the major part of every plant and tree. Wood forms the supportive organ of many woody plants that gives them a firm structure. Wood is characterized by its hard porous fibrous substance, that forms the outer surface of the stem. Wood forms the part of the secondary xylem of the vascular tissues of the plants and trees. This xylem contains cellulose, lignin, and hemicellulose.

Wood can be called a natural composite material that has fibrous material in the form of cellulose. The cellulose binds with the lignin in the form of a matrix. The presence of this composite arrangement makes the wood strong in tension and compression.

Recently wood has been the choice of many civil engineers as an aesthetic building material, as it plays a major role in many structural engineering applications. Moreover, with the growth of wood polymer composites (WPC), engineers and builders have made a major shift from the use of natural wood to laboratory-engineered wood. WPC is primarily made of used wood products such as sawdust, wood left-outs after processing and mixed with many binding materials and polymers to develop an eco-friendly building material. This step also reduces the process of de-forestation.

Sources of wood

According to estimates, wood is produced by approximately 25,000 to 30,000 species of plants, including woody plants and herbaceous plants. Out of which, forest trees and woody plants form the major source. Speaking in the botanical sense, the gymnosperms and angiosperms are the two wood-producing plant species. Gymnosperms are also known as cone-bearing trees, they provide mainly softwoods such as pine and spruce. Whereas angiosperms produce hardwoods such as oak, beech, teak, and balsa.

The wood industry is also known as the lumber industry or timber industry. Forestry, logging, timber trade are the main focus of the lumber industry. Apart from these, the lumber industry is concerned with the production of primary forest products and secondary products such as wood pulp, which are extensively used by the paper industry. The wood industry saw a steep downfall due to the onset of coronavirus disease 2019 (COVID-19) because the construction industry went to a complete halt. With the halt in the construction industry, the supply of wood eventually stopped, as wood forms a major building material. Impacting the environment positively, COVID-19 equally reduced the number of people cutting down trees for construction as well for small privately-owned businesses.

Types of wood

Softwood

The evergreen trees are the major sources of softwood, these trees are characterized by their greenish leaves, that do not fall until new leaves grow. They have less density and are light in color. These trees are also called coniferous trees and usually grow in areas having a cold climate. They grow faster, so they are less expensive. Pine, fir, spruce, larch, and cedar are some common examples of softwood. It is used for interior moldings at home.

Pinewood

These woods are characterized by straight grains and are light yellowish in appearance. Pinewoods grow majorly in the northern hemisphere. Western Himalayas, Assam, and Nagpur are the major sources of pine wood in India. Shaping and staining are easy with pine, and it resists swelling, shrinkage, and wrapping. It is a common type of domestic wood.

Sapwood

Sapwood is also known as the alburnum. Alburnum is the outer secondary layer of tress whose major role is for water and nutrient transportation. Sapwood is characterized by its light color and moisture content. All the woods generally start as sapwood which forms just below the bark of the trees. As these woods are light and soft, they form a small portion of furniture such as decorations and linings.

Heartwood

Moving deep inside the centralized portion of the steam, lies the heartwood. Heartwood is also known as duramen and is characterized by its dark color. It usually forms the inner dead part of the tree. Heartwood strengthens the entire tree, so it has more density than sapwood. It is majorly used for making furniture, floors, and roofs.

Plywood

Plywood is made from wood veneer piled and stacked up in layers. A wood veneer is the thin layer of wood or bark, whose thickness is lower than 3 mm. These layers are glued together to form a single wood mass. The grains of these woods are rotated at an angle of 90-degrees. Plywood falls under the family of medium density fiberboards (MDF) and is used for numerous woodworking and do-it-yourself (DIY) applications. People go LIVE with their DIY at different social media sites such as Twitter, Linkedin, and YouTube.

Uses of wood in different areas

Construction and fencing

This was the major area where wood found its major use in the early days. Wood has been a major building material for house and fencing constructions. Wood is commonly used for flooring, building foundations, building walls, and barriers.

Household uses

Wood is the prime material for making various household utensils. Black walnut forms the major wood source. Various working tools such as hammers are made out of wood. Handles of many working tools are crafted out of wood which provides good grip and also protects the user from electrical shocks.

Commercial uses

There are numerous uses of wood in the commercial domains, they are:

• Shipbuilding: Teak, sal, redwood, Arjun, and white oak are the major wood variants used for making ships as these woods are light in weight and are water-resistant. The decks of the ship are made up of red cedar, teak, mahogany, and ipê along with metal such as aluminum.
• Fuel: Since the olden days, wood has been a primary source of fuel. Even after the discovery of petroleum, wood and its products are still used as major fuel sources in some of the applications. Many fireplaces, including modern fireplaces, make use of wood as their primary fuel.
• Furniture: Wood such as Teak, Jackfruit, Mango, Sundari, Mahogany, and Shimul are extensively used for making furniture. These woods have the right strength, which allows them to bear the load of people and objects.
• Home construction: Deodar, walnut, pine are common woods used for flooring, frames of doors, and windows as these woods are strong.
• Wood products: Various wood products like toys, decorative items, fancy light shades to be used in Patios, restaurants, and so on are extensively used in households.

Context and Applications

This topic finds its existence in many undergraduate and postgraduate degree courses of:

• Bachelors of Technology (Civil engineering)
• Masters of Technology (Civil engineering)
• Masters of Science in Wood technology

Practice Problems

Q1. What is meant by timber?

1. The hard inner portion of stem
2. Mass timber
3. Trees cut into planks and beams
4. Sclerenchyma of plants and trees

Answer: Option c

Explanation: When woods are cut into planks and beams by the lumber industry, they are known as timber.

Q2. Which of the following is also known as lumber?

1. Forest trees
2. Rapids
3. Timber
4. Mass timber

Answer: Option c

Explanation: A timber is also known as lumber.

Q3. Which of the following is true for a veneer?

1. They are sliced portions of the bark of the trees.
2. They have thickness lower than 3 mm.
3. They are stacked together and glued.
4. Both a and b

Answer: Option d

Explanation: A wood veneer is the sliced portion of the bark of a tree. It usually has a thickness lower than 3 mm.

Q4. Which of the following is true for heartwood?

1. They form the inner core of a tree.
2. They have low density.
3. They are used as a part of the furniture for making decorations and linings.
4. All of these.

Answer: Option a

Explanation: Heartwood forms the inner core of a tree whose density is higher than sapwood.

Q5. What are the types of wood that can be obtained from gymnosperms?

1. Rapids
2. White oak
3. Pine
4. Hardwood

Answer: Option c

Explanation: Pine is the wood product from gymnosperms.

Related Concepts

• Types of wood
• Furniture
• Plywood
• Timber