Figure S1. Long-term climatic trends recorded in the study area. Above: mean annual temperatures (T): thin line, CRU dataset; bold line, data from Teruel meteorological station corrected for the altitude of Alcalá de la Selva (−0.65 °C every 100 m gained in elevation). Below: total annual precipitation (P): thin line, CRU dataset; bold line, data from Alcalá de la Selva meteorological station. CRU trends were smoothed by LOESS fitting (span = 0.5). Temperature trends from Teruel were fitted to a linear regression (slope = 0.025 °C yr−1). The grey bars highlight climatic conditions after the 2001–2002 dieback episode.

Figure S2. Trees affected by winter-drought induced dieback in the study area showing brown needles (the photograph was taken in February 2002).

Figure S3. Estimated rates of radial increment for declining (D) and non-declining (ND) trees based on manual band dendrometers recorded in 2008 (means ± SE) and related climatic conditions (T, mean monthly temperature; P, total monthly precipitation).

Figure S4. Frequencies of earlywood (EW) tracheids as a function of their transversal lumen diameter for declining (D, filled bars) and non-declining (ND, hatched bars) Scots pines. The frequencies between both types of trees were computed considering years of high (wide rings: 1976, 1984 and 1992) and low radial growth (small rings: 1974, 1987, 1998). Frequencies were compared among decline classes to test the null hypothesis that the lumen distributions of the two groups of trees did not differ using an adjusted G test (Gadj).

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