Norway spruce in Estonia reflects the early summer weather in its tree ring width

From Norway spruce (Picea abies (L.) H. Karst) trees all over Estonia increment cores were collected to study the relationship between tree-ring width and climate; particular emphasis was given to pointer years. Between 1871 and 2009, 34 negative and 31 positive pointer years were identified. As a limiting factor for the growth of spruce, June precipitation/temperature turned out to be most obvious, especially in pointer years. This dependence lost previous importance during the last decades while the amount of rainfall slightly increased.