Abnormal compression wood inPinus taeda: A review of current knowledge and proposed future strategy

Abstract

Synopsis Abnormal compression wood in P. taeda stands was first discovered in the early 1980s. Since then several research projects and surveys have been carried out in order to develop a better understanding of the problem and to try to find a solution. Currently a large proportion of the sawmill intake of logs in the Mpumalanga and Northern Province forest regions consists of this species, of which a reasonable proportion is affected by abnormal compression wood to varying degrees. This paper summarises the existing knowledge on the problem and current ways of dealing with it. Conclusions are that, since on average about 95% of the trees are either free from abnormal compression wood or manifest only a very slight presence of the phenomenon, the impact of the problem may not be as severe as generally thought, provided that a number of precautions are adhered to. Procedures such as leaving the worst affected logs in the plantations or labelling such logs as unsuitable for the production of veneer or boards for value-adding applications, may help considerably in reducing the impact of the problem. Graders at sawmills should be trained to assess the severity of abnormal compression wood present in sawn boards by inspecting the cross-cut ends of the boards where the phenomenon is usually best observed. Such boards should be labelled as not suitable for value-adding purposes or for further processing, except for cross-cutting them into particular lengths, should that be required. P. taeda has proved to be one of the best pine species with respect to growth and wood quality and should not be rejected outright. Further research on the phenomenon in order to extend the existing knowledge on the effects of genetics and silviculture is, therefore, strongly recommended. Tree breeding, in particular, appears to be the most promising approach to return this species to its former prominent position.