Heart Shake in South African-Grown Pinus Elliottii

William Kevin Darrow

Abstract


Heart shake, internal cracks in the radial and longitudinal planes of standing trees, is the most common and serious defect of South African-grown Pinus elliottii.

A series of experiments sampled immature and mature trees throughout the Eastern Transvaal region of South Africa. The objectives of these studies were to determine the distribution of heart shake within and among trees, whether the physical characteristics of the trees or any environmental factors were associated with heart shake, the age at which heart shake begins, and the factors that initiate heart shake.

Heart shake was found in all locations sampled. No physical characteristics of the trees or environmental factors could be associated with the incidence of heart shake, although the rate of growth and exposure to strong winds did influence the severity of heart shake in a tree. Within trees most of the heart shakes were located in the butt, extending downward into the stump. Heart shake is initiated in a tree by various types of wounding, particularly by mechanical damage during nursery and field planting stages. Damage to the root collar zone causes a point of weakness that enlarges longitudinally and radially into a heart shake as the tree grows. There is a possibility that there are genetic differences in the incidence of heart shake among families of Pinus elliottii. There are very large differences among trees in the severity of heart shake and the degree of resinosis associated with heart shake that cannot be presently explained.


Keywords


Heart shake;Pinus elliottii

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