Size of tree and type of forest
Small trees have average heights up to 10 m, medium 10 to 30 m, and tall trees over 30 m. Vegetational complexes include forest (with more than 80 per cent canopy cover) and woodland (with scattered trees).

Diameter breast height (dbh) is stem diameter at 1.3 m above ground, which is a standard forestry measure.

Wood description
This description can include heartwood and sapwood colour, grain, figure.

Wood density
Green density is the density of wood in the living tree, defined as green mass divided by green volume, and useful for estimating transport costs. It varies with season and growing conditions.

Air-dry density is the average mass divided by volume at 12 per cent moisture content (this is the average environmental condition in the coastal capital cities around Australia).

Basic density is oven-dry mass divided by green volume. This measure has the advantage that moisture content variations in the tree during the year are avoided.

Drying and shrinkage
As wood dries, it shrinks more in the tangential direction (i.e. parallel to the growth rings) than it does in the radial direction (i.e. at right angles to the growth rings). The figures given are shrinkage from green to 12 per cent moisture content, before steam reconditioning treatment, and with some species after stream reconditioning. Reconditioning is essential for recovering collapse which may have occurred during the drying process, and is essential for species such as the ash-type eucalypts of eastern Australia.

Workability
With south-west and plantation-grown trees, comments are made on the comparative ease or difficulty of turning, nailing and bending, on susceptibility to splitting and other working properties.

With semi-arid, arid and desert species, a more complex survey was made and reported in Siemon and Kealley (1999). The properties assessed were turning, machinability, boring, screwholding, stability, sanding, gluing and finishing. A semi-quantitative score was used: very poor = 1, poor = 2, average = 3, good = 4, and excellent = 5. This book uses the descriptive terms rather than numbers.

Durability
The CSIRO Durability Classes are based on the performance in ground of outer heartwood when exposed to fungal and termite attack.

The ratings are not relevant to above-ground use. In late 1996, CSIRO published revised ratings, which include termite susceptibility. Ratings are now available for about seventy species for decay, and for decay plus termites.

Lyctus-susceptibility
The powderpost borer (generally Lyctus brunneus) attacks dry sapwood of certain hardwoods, but never softwoods. Susceptible species contain starch and have pores large enough for the female insect to insert her ovipositor and lay eggs. Sapwood of susceptible species should be treated with an approved preservative to minimise the risk of attack.

Strength grouping
Minimum values (MPa) for strength groups for green and seasoned timber come from Australian Standard AS2878-1986 'Timber - Classification of strength groups'. In grading structural timber, each species is allocated a ranking for green timber of S1 (strongest) to S7, and for seasoned timber SD1 (strongest) to SD8.

MOR is modulus of rupture or bending strength, MOE is modulus of elasticity or 'stiffness', and MCS is maximum crushing strength or compression strength. Hardness refers to the Janka hardness test and is a measure of resistance to indentation.

Minimum values (Mpa) for green timber

Minimum values (Mpa) for green timber

Strength Properties
Where test data were available, they are shown in bold print. Most values are from Bootle (1983), Wood in Australia. Types, properties and uses. (McGraw-Hill), or Julius (1906), 'Western Australian timber tests 1906: The physical characteristics of the woods of Western Australia'.

Where no strength data were available, air-dry density was used in accordance with the Australian Standard AS2878-1986 Timber - Classification of strength groups to predict the strength group. Consequently, the strength values quoted are from the above two tables.

Uses
Various past and potential uses are given as a general guide, but the list is obviously not conclusive. In particular, there is increasing interest in specialty timbers, and the semi-arid, arid and desert area species have considerable potential for this use.

Availability
Timber from many species is available only in limited quantities, from near the areas where the trees grow naturally (or in plantations). There are other species such as red tingle and yellow tingle whose timber is rarely commercially available because the areas of occurrence are predominantly in conservation areas. Other species such as Goldfields timbers are only available in limited quantities because of their scattered occurrence and the fact that the industry is in the early stages of development.

References

• Boland, D.J., Brooker,.M.I.H., Chippendale, G.M., Hall, N., Hyland, B.P.M., Johnson, R.D., Kleinig, D.A. and Turner, J.D. (1984). Forest trees of Australia. Nelson, CSIRO. Melbourne.
• Bolza, N. and Kloot, N.H. (1961). The mechanical properties of 174 Australian timbers. CSIRO Division of Forest Products. Technological Paper No. 25.
• Bootle, K.R. (1983). Wood in Australia. Types, properties and uses. McGraw-Hill Book Company, Sydney.
• Julius, G.A. (1906). Western Australian timber tests 1906: The physical characteristics of the hardwoods of Western Australia. Published by the Government of Western Australia.
• Kingston, R.S.T. and Risdon, C.J.E. (1961). Shrinkage and density of Australian and other South-west Pacific woods. CSIRO Division of Forest Products. Technological Paper No. 13.
• Melotte, D. (1997). Unpublished thesis. Curtin University of Technology.
• Siemon, G.R. and Kealley, I.G. (1999). Goldfields Timber Research Report. Report by the Research Project Steering Committee. Department of Commerce and Trade and others.
• Standards Association of Australia (1986). Timber - Classification into strength groups. AS2878-1986.