Large‐scale atmospheric variability entails differential modes of seasonal tree growth in the Mediterranean Basin

Abstract

Synoptic scale changes in atmospheric circulation govern the climate that affects wood formation over wide geographical extents. Intra‐annual tree growth exhibits disparate climatic responses across seasons, and its reliance on teleconnections may ultimately result in the development of contrasting growth modes over large spatial extents. Teleconnections' impact on seasonal tree growth in Mediterranean species is poorly understood; yet it is crucial for the global carbon cycle. We collected wood samples on 335 Pinus nigra trees, a circum‐Mediterranean species, encompassing a 2000 km wide gradient of the Mediterranean Basin. Our statistical framework included four teleconnections and served to address separately and for each season: (1) the spatial differences of the teleconnection–climate links, (2) the response of late‐ and early‐wood growth to the interactive effect of precipitation and temperature and (3) the direct link between teleconnections and late‐ and early‐wood. We report a strong, uniform and positive link between the East Atlantic Pattern and temperature over all analysed sites and seasons. However, the impact of teleconnections on precipitation was predominantly negative, with spatial heterogeneity observed in all seasons for all teleconnections except one. Winter and spring temperatures positively influenced earlywood and spring latewood, respectively, while precipitation effects were always modulated by temperature for both intra‐annual growths. Teleconnections controlled more intensively latewood than earlywood and confirmed that climatic patterns related to precipitation showed the biggest differences in intra‐annual growth in size and sign, like the Western Mediterranean Oscillation. Synthesis. In this work, we demonstrate the control of teleconnections on seasonal tree growth through local climate across the Mediterranean basin. Despite the constant link between the East Atlantic Pattern and temperature, synergies among teleconnections pointed to an east–west dipole in tree seasonal growth, driven by precipitation variability. The Iberian Peninsula and the North and South Balkans presented significant differences with respect to the entire Mediterranean basin, particularly during the summer and coinciding with the formation of latewood. This highlights how teleconnections promote differential tree growth modes at large geographical scales, which is of particular importance for the carbon cycle, given the substantial amount of carbon stored in latewood.