Incidence of butt rot in Norway spruce seed stands in Poland’s mountain regions assessed with sonic tomography

The incidence and severity of butt rot were assessed in 12 selected Norway spruce seed stands in the Beskidy Mountains, Poland. A semi-invasive technique of sonic tomography was used for the assessment of rot damage. Stands of different age classes (100-120, 130-150, 160-170 years old) and distinct regions of provenance (Istebna and Orawa) were investigated. Hierarchical analysis of variance was used to determine effects of stand age and stand provenance on butt rot occurrence at a stand level. High incidence of butt rot was noted in all of the studied seed stands (47% to 87% of diagnosed tree samples). Stand age had a significant effect on percentage share of ‘damaged wood’ on the tomogram. The extent of rot damage was rising with stand age, and the largest was observed in the age category 160-170 years. Spruce stands of Istebna provenance were generally more damaged by butt rot than those of Orawa provenance, however, the latter have been growing in forest sites more suitable for spruce in terms of fertility and altitude. Hierarchical analysis of variance did not show a statistically significant relationship between the region of provenance and average share of ‘damaged wood’ on the tomogram. Presented results indicate that for stands growing in similar conditions vulnerability to butt rot is determined by stand age. Further research is needed to separate impact of stand provenance identified with specific genetic constitution of a population from the effect of environmental conditions typical of a given region of provenance.