Abstract
The study of decay and decay relationships of white pine was undertaken to provide forest authorities in Ontario with information essential to the management of even-aged stands. Of 1012 white pine trees examined in 10 1-acre plots, located in even-aged white pine stands, 52% contained decay. A well-defined relationship existed between age and decay. The proportion of trees with decay increased gradually with age from 40% in the 60-year age class to 100% in the 220-year age class. The loss in merchantable volume increased from 4% at 60 years to 40% at 200 years. No consistent relationship between percentage of decay and diameter was found. The incidence of decay in vigorous and non-vigorous trees was about the same but the percentage of volume lost through decay was considerably higher in slow-growing, less vigorous trees. The pathological rotation, as indicated by the maximum periodic increment, was 160 to 170 years. A number of methods of estimating the volume of decay in logs are compared. Regression lines, which define the percentage of cull allowances at all ages, are presented. Thirteen wood-destroying fungi were found to be associated with the decay of living white pine in Ontario. Fomes pini (Thore) Lloyd was responsible for 90% of all loss in trunks and butts of living trees. External signs of decay were rare, except in cases of advanced white pocket rot caused by F. pini.

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