Large-scale climatic variability and radial increment variation of Picea abies (L.) Karst. in central and northern Europe

High-frequency variation of Norway spruce radial increment [Picea abies (L.) Karst.] and its dependence on various climatic variables was compared in stands across latitudinal and altitudinal transects in southwestern and eastern Germany, Norway, and Finland. The tested variables included local temperature and precipitation, northern hemisphere temperature anomalies, and the climatic teleconnection patterns (North Atlantic Oscillation, East Atlantic, East Atlantic Jet, East Atlantic/West Russia, and Scandinavian patterns). Climatic impact on radial increment increased towards minimum and maximum values of the long-term temperature and precipitation regimes, i.e. trees growing under average conditions respond less strongly to climatic variation. Increment variation was clearly correlated with temperature. Warm Mays promoted radial increments in all regions. If the long-term average temperature sum at a stand was below 1,200–1,300 degree days, above average summer temperature increased radial increment. In regions with more temperate climate, water availability was also a growth-limiting factor. However, in those cases where absolute precipitation sum was clearly related to radial increment variation, its effect was dependent on temperature-induced water stress. The estimated dates of initiation and cessation of growing season and growing season length were not clearly related to annual radial increment. Significant correlations were found between radial increment and climatic teleconnection indices, especially with the winter, May and August North Atlantic Oscillation indices, but it is not easy to find a physiological interpretation for these findings.