A research project at the Department of Forest and Wood Science on alternative management regimes for South Africa's saw-log trees recently received a huge boost from a successful THRIP funding application to the government's Department of Trade and Industry. The project will receive R8.1 million over 3 years with industry and government each contributing about half of the cost. Three PhD and eight MSc students are supported in this project which will range from basic research activities on tree physiology to the development of decision support models for managing saw-log plantations. The main commercial partners are represented by the industry organisation Forestry South Africa (FSA) with the Hans Merensky Foundation also providing funding.
According to dr. Brand Wessels, adjustments in the management regimes of South African grown saw-log resources as well as genetic tree improvement resulted in profound changes in the wood properties of pine and eucalypt trees in South Africa. Many forestry companies growing pine saw logs decreased the plantation rotation age from close to 30 years to less than 23 years over the last two decades. One of the consequences of lower rotation ages is lower stiffness of lumber products which is problematic for structural lumber producers. It is possible to improve the stiffness of lumber of most of our pines by applying higher planting densities. In fact, wood and lumber properties could be manipulated through a number of interventions including genetic selection, rotation ages, and silvicultural management options such as planting density and thinning. Each of these interventions has cost and value influences that can be complex to analyse. For instance, increased planting density increase the stiffness and value of lumber end products, but it will also increase the planting cost, harvesting cost, and result in lower diameter trees. The primary objective of this project is to create a decision support framework, using software tools, for saw-log growers and processors which will assist them to maximize the financial returns over the full saw-log value chain. The focus will be on finding optimal solutions in terms of rotation age, planting density, and thinning ages and intensity while providing wood material with acceptable properties.