Climatic signal in annual growth variation in damaged and healthy stands of Norway spruce [Picea abies (L.) Karst.] in southern Finland

Annual radial increment variation and its dependence on temperature and precipitation were studied in 13 severely damaged and 12 healthy stands of Norway spruce [Picea abies (L.) Karst.] on mineral soil and peatlands in southern Finland. An intervention analysis revealed that the presently dead trees had experienced severe growth reductions since the late 1980s. Even though annual growth variation between the stands was fairly similar, differences in the relationship between radial growth and weather variation were found between sites. High temperature in May increased radial growth in the healthy stands. This was not observed in the damaged stands, where summer temperature was negatively correlated with growth. In addition, high temperature during the previous summer decreased tree growth in next summer. Tree-ring indices showed a strong positive correlation with June precipitation in the damaged stands. Correlation of June precipitation and growth was much weaker in the healthy stands. This result suggests that the damage is connected to drought and is likely to occur at drought-sensitive sites. The finding also fits in well with the fact that many of the damaged sites were rocky or stony.