Fig. 4

Mean correlation coefficients calculated between tree-ring width residual chronologies and series of the SPEI drought index obtained for different monthly scales (from 1 to 48 months) in the five study sites. Correlation analyses were performed for monthly drought data of the previous year (t − 1) and the year of tree-ring formation (t). Sites are arranged from cold and wet (left) to warm and dry climatic conditions (right). Correlation values above +0.20 and below −0.20 are significant at the P = 0.05 level. Sites’ codes are as in Table 1