The changing quality of the world wood supply

SummaryThe reasons for changes in wood quality and utilization are related to the trends toward harvesting smaller, younger and lower-quality timber, wider use of formerly waste wood, unconventional uses of wood, and improved forest management and new wood manufacturing techniques.1.An unequal distribution of timber along with increasing costs of forest ownership and management is forcing short-rotation forestry, which results in small-sized timber, low-quality wood, and a high proportion of juvenile wood and knots. This is true for almost all forest regions although it has been most evident in tropical plantations. The economic pressures for short-rotation ages will become increasingly great, especially in those areas where a timber imbalance in age class distribution occurs.2.Especially in the Tropics, many forestry organizations are planting exotic species on a massive scale and are producing a large volume of “different” wood. The trend toward using exotics is very strong. The trees attain a merchantable size at young ages, with thinning being standard; this produces a large proportion of juvenile wood. Such wood is not desirable for some products, based on current quality criteria, and may be distinctly different from the wood that the same species produces in its indigenous environment. Huge amounts of it are now becoming available, requiring a reassessment of both manufacturing techniques and product type and quality.3.Better utilization in forest harvesting operations results in the use of mill residues of bark and sawdust and forest residues of bark, limbs, leaves, stumps and roots that formerly were considered to be waste. There is also greater utilization of previously unwanted species, including some which were once considered to be of limited value and often were destroyed during regeneration programs. Of great importance are the technological developments that are enabling a greater utilization of the grossly differing woods found growing together in tropical forests, rather than using only a few species and destroying the rest.4.Wood quality is very responsive to both silvicultural and genetic manipulation. The improvements possible in wood will partially offset some quality declines caused by young wood and lower quality trees. The quickest and easiest method of changing wood quality is to control age of harvest.5.New industries are developing which use wood as a source of energy and organic chemicals. In some areas, wood for energy is primarily obtained from large forests being planted solely for energy needs and is secondarily obtained as a salvage product from the forest. From 20 to 50% of the wood harvested in the world is for firewood, which often results in a marked reduction of the quality of the wood used for industrial purposes. Currently some research is focused to grow trees which will yield improved energy and chemicals.6.New manufacturing techniques, such as oriented strand-board and the endgluing of short, clear wood segments from low-quality logs, are enabling the production of high-quality products from low-quality timber. These manufacturing techniques result in products that differ markedly from those previously available but they are stable and of excellent quality. However, a strong sales program will be needed to assure acceptance of the different products.