Ecological factors influencing frequency of Norway spruce butt rot in mature stands in Lithuania

We assess the influence of edaphic, climatic, stand structure and individual tree (stump diameter) factors on incidence of Norway spruce (Picea abies (L.) H. Karst.) butt rot. The data used in the study come from 97 stands, originated from natural regeneration, which were clear-cut. The age of the stands varied between 71 and 130 years old. The climate continentality, site fertility, hydrotop (site humidity index), part of Norway spruce in the stand, stand stocking level (density index) and stump diameter were selected as the factors related with frequency of decay. The study material revealed that selected variables explain 34% of Norway spruce butt rot incidence in Lithuanian forests. Site fertility and stand age influence on butt rot incidence was weak. Higher incidence was related with low stand density, low site humidity (dry sites) and higher part of Norway spruce in stand. More frequent damages were recorded on higher diameter stumps. Our results showed longitudinal distribution of decay incidence in Lithuania-the frequency of decay increasing from West (coast) to East (continent).