Jul 14, 2020
When the toilet paper shortage hit Australia in March, few people would have thought of the timber industry’s role in maintaining supply amid the panic-buying. As the ultimate renewable, timber has been a versatile natural material for shelter, heating, working and comfort for thousands of years. The simple recipe for success is regeneration – when trees are harvested, seedlings are planted and the life cycle starts afresh.
In turn, the forests in which they grow deliver environmental benefits, which includes helping protect water and soil quality (by stabilising soils and rehabilitating saline landscapes) and combating carbon emissions and air pollution through the process of photosynthesis, sequestering carbon dioxide from the air and the storage of carbon in trees and wood products. How that sapling transforms into the sheet of paper you’re writing on, the pencil you’re using, or the enduring piece of furniture on which you sit is a process that takes place over decades.
Australia has 134 million hectares of forest – about 17 per cent of the total land mass – all of which are subject to the pressures of land clearing, urban development, drought, fire, climate change and invasive weeds, pests and diseases.
About 8.9 million hectares of our native forest – encompassing acacia, callitris, casuarina, eucalypt, mangrove, melaleuca and rainforest – and commercial plantations are covered by a code of practice and standards developed under the Responsible Wood Certification Scheme or the Forest Stewardship Council.
Plantations cover an area of about two million hectares (about 1.5 per cent of the total forest area) and account for more than 85 per cent of the 32.9 million cubic metres of logs (61 per cent softwood and 39 per cent hardwood) harvested each year. Minimising wastage, the $23 billion industry is enhanced by efficient sawmills, cutting-edge reconstituted and engineered wood facilities, and best-practice pulp mills.
But perhaps most importantly, the Department of Agriculture’s National Forest Industries Plan aims to plant a billion plantation trees over the next decade so the precious life cycle can continue long beyond the next generation.
Much thought goes into creating a plantation, ensuring biodiversity values are maintained to allow the maximum rate of tree survival and growth throughout its estimated 40-year growth cycle.
This plan, as detailed by Forestry SA, meticulously examines every variable expected to affect the plantation during its lifetime, such as erosion prevention and location of forest tracks to weed infestation, soil type and its nutrient content. A nursery cultivates young plants from seed or cuttings sourced from genetically superior plants. They are planted when about 25cm high or around nine months old, with no more than 1600 trees per hectare – providing competition for the available moisture, sunlight and nutrients.
In a classic example of survival of the fittest, between 30 to 50 per cent of trees are removed as trees are “thinned” at 10-year intervals to allow the remaining trees to establish the optimum rate of growth.
The removed low-grade trees are usually used for fence posts and other pulp products, and those remaining take advantage of the reduced competition until the forests near maturity, usually between 37 and 40 years. Once mature, the trees are clear-felled, which allows the site to be rejuvenated and regenerated and the process to be repeated.
When felling, trees are specifically cut at the lowest possible point of the trunk to extract the maximum amount of timber. When it is newly felled, a tree contains about 50 per cent of its dry weight as water, including sap and moisture.
After harvesting, logs are stored in a clearing or in the forest, where they are cut into smaller lengths and transported to a processing site, such as a paper mill or sawmill depending on its quality and suitability for future use as furniture, framing timber for housing construction, or pallets and crates.
Wood is a hygroscopic material, which means it has capacity to absorb water vapour from the air, so it is necessary for some of that moisture to be removed to reduce its weight and prepare it for its next stage of life.
The drying process, otherwise known as seasoning, helps the wood avoid cracking, warping, swelling and shrinking. Natural seasoning or drying is carried out by atmospheric airflow, or artificial methods include various forms of heating to dry the wood more rapidly.
The seasoned timber is cut and sawn to specific sizes. Some of it is then treated with preservatives to increase its life, durability and provide protection from fungal and insect attack.
Only then, after turning trees into timber, can the material be refined by man or machine into the wondrous, practical and cherished keepsakes they ultimately become.