Butt rot occurrence in plus trees of Silver fir Abies alba Mill. and Norway spruce Picea abies (L.) from the Carpathians

Due to its hidden character, butt rot occurrence is not commonly included in the assessment of plus trees’ health status. Thus, the trees’ varied susceptibility to wood decay is not a target of breeding efforts. The aim of the study was to determine the extent of butt rot in fir and spruce plus trees from Carpathian seed stands. We employed the novel and non-invasive diagnostic method of sonic tomography to determine presence and severity of decay at the base of 110 plus trees of silver fir and 42 of Norway spruce. Butt rot in various stages of development occurred in 63% of investigated fir trees and in 45% of spruce trees. The proportion of damaged wood on the tomogram ranged from 0–38% in fir and 0–47% in spruce with similar average proportions of solid wood in all forest districts. The vast majority of trees was in the range of 80–90% solid wood. Plus trees of fir and spruce were affected by butt rot to a similar extent and the degree of damage increased with age in both species. However, a large variation in susceptibility to butt rot was found between individual trees leading to the conclusion that the identification of old trees, which wood is not decayed, may be the basis for further research on the resistance to butt rot.
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