2. Definition of valuable hardwood species

According to the Merriam Webster English Dictionary, the definitions of “valuable” are either of the following: “having monetary value; worth a good price; having desirable or esteemed characteristics or qualities; of great use or service”.

Cooper (FAO 1991) has attempted a definition close to “valuable hardwoods” by defining “high value end uses” for these timbers. They are “uses ranging from those in which tropical timber (sawnwood, plywood or veneer) is virtually irreplaceable to those uses where it is strongly preferred to alternative materials (wood or non-wood) for technical, aesthetic or commercial reasons”. The term “valuable” or “high value” was considered to be too imprecise and open to interpretation.

Valuable hardwoods[1] can therefore be considered as those hardwood species or group of hardwood species with special technical properties (e.g. strength, natural durability and good machining properties) and appearance[2] (i.e. grain, figure, texture and colour or aesthetic qualities) that makes them suitable for “high value end uses”. These high-grade hardwoods contrast to lesser quality woods used only for woodfuel or pulpwood. The special characteristics of valuable hardwoods lend them particularly well to the speciality markets, which are usually also the highest value markets. Species such as teak (Tectona grandis), mahogany and rosewood (especially the genus Dalbergia) obtain considerably higher prices than commodity timbers. Teak is one of the most valuable multi-purpose tropical hardwood timbers of the world. It is well known for its beauty, strength and durability, versatility of its applications, dimensional stability under a wide range array of environmental conditions, natural resistance to weathering and biological attacks, and its ability to grow well in plantations (Centeno 1996).

The highest value hardwood application is veneer, which normally requires larger diameter (more than 46 cm) and defect-free wood. However, veneer lathes can convert relatively small dimension material into veneer.

Even though the forests in Africa and Latin America are dominated by the family Leguminaceae, their leading commercial timbers belong to less common families, such as the Meliaceae. The Meliaceae or the 'mahogany family' are good examples of valuable tropical hardwoods. It includes the species of such genera as of Khaya, Entandrophragma, Lovoa in Africa and Swietenia, Carapa, Cedrela in Latin America. Commercially, some of the various woods resembling or substituted for Mahogany includes some species of the genera Shorea, Tabebuia, Trichilia, Eucalyptus, and Aucoumea.

The highest quality decorative veneers and sawnwood are made from Mahogany, Sapele, Teak, Kokrodua, Utile and selected logs of other species (Table 1 - see Appendix 1 for common names). Woods converted into plywood and veneers include Okoume, Obeche, Limba, and Makore from Africa; Lauan, Meranti and Seraya from Asia. Together with Abura, Iroko (African teak), Kokrodua and Niangon from Africa; Ramin and Keruing from Asia, they are also made into sawnwood for use in construction (Grainger 1993).

Ekki from Africa, Greenheart from Latin America and Keruing from Asia are heavier and very durable woods used for key structural purposes in the construction industry (e.g. for railway sleepers/ties and marine construction) - see Table 1.

Table 1: Characteristics of valuable hardwood species used in the tropics

Use Categories

Desirable Wood Properties

Main End Uses

Examples of Matching Valuable Hardwood Species

Comments

Decorative Timbers

Appearance, consistent quality, dimensional stability, durability, good machining, staining and finishing properties

Quality furniture and interior joinery

Teak, Khaya spp., Swietenia spp., Dalbergia spp., Aningeria spp., Makore, Sapele, Bete, Walnut, Iroko, Utile, Okoume, Afromosia.

Highest value. Competition from temperate hardwoods & MDF.

High to Very High-Density Timbers

Appearance, Strength, high natural durability, availability in large sizes

Principally in construction

Keruing, Greenheart, Ekki, Iroko.

Small share of total tropical timber use

Low to Medium-Density Utility Timbers

Appearance, clear grain, natural durability, good machining properties

External joinery, shop fitting, medium priced furniture.

Shorea spp, Limba, Niangon. Rubberwood

Largest end-uses, prone to competition from substitutes materials.

Source: Based on FAO 1991

The valuable hardwood species in the temperate climates include Oak, Ash, Cherry, Walnut, Tulipwood and Hard Maple. These are mainly used for furniture, joinery and interior decoration.

[1] Hardwoods can be described as the wood of non-coniferous tree species. They can be either deciduous or evergreen. The natural characteristics of most hardwood species make them differ from softwoods with respect to the finished products derived from the trees.
[2] The "Appearance" of wood used in this sense may be defined its decorative appearance due to its colour, texture and figure, either in isolation or combination. "Figure" may also be defined as the appearance of the wood due to anatomical features of wood grain, growth rings, rays and knots.

Use Categories	Desirable Wood Properties	Main End Uses	Examples of Matching Valuable Hardwood Species	Comments
Decorative Timbers	Appearance, consistent quality, dimensional stability, durability, good machining, staining and finishing properties	Quality furniture and interior joinery	Teak, Khaya spp., Swietenia spp., Dalbergia spp., Aningeria spp., Makore, Sapele, Bete, Walnut, Iroko, Utile, Okoume, Afromosia.	Highest value. Competition from temperate hardwoods & MDF.
High to Very High-Density Timbers	Appearance, Strength, high natural durability, availability in large sizes	Principally in construction	Keruing, Greenheart, Ekki, Iroko.	Small share of total tropical timber use
Low to Medium-Density Utility Timbers	Appearance, clear grain, natural durability, good machining properties	External joinery, shop fitting, medium priced furniture.	Shorea spp, Limba, Niangon. Rubberwood	Largest end-uses, prone to competition from substitutes materials.