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Context Global change is leading to more frequent and intense tree damage and mortality events. Drought-induced tree mortality is occurring worldwide leading to broad-scale events, but the spatial patterns of tree damage and mortality, their underlying drivers and their variation over time is largely unknown. Objectives We investigated the spatial patterns of tree damage and mortality across Mediterranean forests of the Iberian Peninsula, the underlying effects of stand structure and climate, and how the spatial patterns and relationships with underlying drivers changed over time. Methods We used the Spanish Forest Inventory to analyse the autocorrelation in tree damage and mortality across forest types, hurdle-gamma models to quantify the effect of stand structure and climate on tree damage and mortality, and cross-correlograms to assess their spatial dependence and its change over time. Results We observed a greater magnitude and a stronger autocorrelation in tree damage than mortality, with positive aggregation up to 20 kms. There was a spatial dependence between tree damage and mortality with their drivers, with spatial aggregation increasing with water availability, drought intensity and stand structure. The spatial dependence of tree damage and mortality with the underlying drivers increased over time, particularly for drought intensity. Conclusions Our results suggest that the combined effect of intense competition and drought could favour more extensive die-off and tree mortality events, providing key information for identifying vulnerable areas and the planning of adaptation measures.

Increased winter and early spring temperatures due to climate change can enhance forest productivity due to earlier growth onset in temperate regions. However, drought-prone forests can be highly vulnerable to the combined effect of high summer temperatures and water stress. Understanding how water stress and rising temperatures along the growing season control tree growth in co-occurring species with contrasting drought tolerances is key to project climate change effects on forest dynamics. Here, we evaluated the interactive effect of seasonal temperature and water availability on annual radial growth and climate?growth instability over six decades (1951?2015) in three pine species with contrasting drought tolerances (Pinus pinaster, Pinus nigra, and Pinus sylvestris). For this, we retrospectively observed radial tree growth using dendroecological methods and evaluated seasonal temperature and water availability effects by using linear mixed models. Early growing season temperature and water availability had a positive effect on tree growth, but the positive effect of late season temperature was modulated by water availability. Moving time-window analyses revealed temporal instability in climate?growth relationships. Since the 1980s, pine species showed a higher growth sensitivity to both seasonal temperatures and annual water availability. Furthermore, growth reductions were more pronounced due to increased summer temperatures and reduced precipitation. Our results were similar for the three studied pine species despite their contrasting tolerance to drought. Overall, climate warming effects on pine growth are contingent upon water availability in Mediterranean continental forests. Synchronization among species, climate?growth instability, and negative growth trends suggests an increased vulnerability to drought of Mediterranean pine species in response to ongoing climate change.

• Ministerio de Economía y Competitividad. Proyectos CGL2015-69186-C2-1-R (Fundiver) (I+D+i), CGL2015-69985-R (CLIMED) (I+D+i), CGL2013-48843-C2-1-R (CoMo-ReAdapt), AGL2014-53822-C2-1-R (SATIVA) (I+D+i), XIRONO (BFU2010-21451) (I+D+i), CGL2014-52135-C03-01, PCIN-2015-220, CGL2016-81706-REDT (Red Ecometas), 1560/2015 (ECOHIPRO) • European Research Areas for Climate Services. Proyectos IMDROFLOOD (Water Works 2014, EC) e INDECIS • Xunta de Galicia. Proyectos PGIDIT06PXIB502262PR, GRC GI-1809, ROCLIGAL-10MDS291009PR • Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria. Proyecto RTA200600117 • Proyectos Interreg V-A POCTEFA (CANOPEE, fondos 2014-2020-FEDER) • Ministerio de Economía y Competitividad. Beca para Marina Peña Gallardo • Ministerio de Economía y Competitividad. Becas postdoctorales IJCI-2015-25845 y FPDI 2013-16600, para Raúl Sánchez Salguero y Antonio Gazol Burgos • Fondos FEDER