Is Pinus pinea growth affected by climate change in western Anatolia?

Pinus pinea L. (Stone pine) is an important tree species in the Mediterranean basin, particularly in coastal regions characterized by a subtropical Mediterranean climate with dry summers. It is widely cultivated for its pine nuts and aesthetic appearance. The recent decrease in pine nut production in the Aegean Region has prompted us to investigate whether the growth of stone pine trees is affected by climate change. We collected 60 cores from 30 trees at two sites representing lower and higher elevations. Using standard dendrochronological analysis, two site chronologies were constructed for the lower and higher altitudes. Linear and non-linear analyses were performed to determine the climate-growth relationship of sampled trees. Furthermore, we calculated growth resilience to drought, including resistance and recovery components. We also examined the climatic trends in the study area to enhance our understanding of the climate-growth relationship. The air temperature time series analyzed in this study has shown a recent shift towards higher average temperatures, observed around the late 1980s and early 1990s. We observed a positive correlation between residual chronologies and total precipitation from December to July. Adequate precipitation in early autumn is essential for latewood formation. The positive correlation between tree-ring growth and winter temperatures indicates that milder winters extend the vegetation period and affects the radial growth of pines. Moreover, moving correlation analysis revealed a notable shift, with the limiting effect of drought significantly increasing and the limiting impact of winter cold diminishing in the early 1990s. Generalized additive mixed model (GAMM) analysis described thresholds for additional increment based on the non-linear relationship with precipitation and weakly non-linear relationship with temperature. Stone pine trees showed relatively low resistance, high recovery, and a general low resilience to drought.