We used tree ring analysis to assess the response of Pinus pinea to climate change in South Iberia. Climate–growth relationships changed over time, with greater sensitivity in recent years due to increasing aridity. A common dendroclimatic signal among sites was found, suggesting that climate change is the main responsible for the observed variation in tree growth. Understanding the response of Mediterranean forests to climate change is required to assess their vulnerability and to develop measures that may limit the impact of future climate change. We analyzed the sensitivity of several populations of Pinus pinea (Stone pine) in Southern and Central Spain and Portugal to climate and identified some responses to climate change. We constructed tree ring chronologies and studied the dendroclimatic signal over the last century. There were similarities in tree ring growth and response to climate among sites. Growth was enhanced after precipitation during the previous autumn and the current spring and was limited by water shortage. In recent decades, aridity increased in the study region and the sensitivity of tree ring growth to water availability increased at all study sites. We also observed an enhanced growth synchrony among chronologies as well as an increase in ring width variability during the last decades. The radial growth of P. pinea indicated strong effects of climate change. The climatic signal in tree ring chronologies suggested a plastic growth response to climate of this species, although the enhanced growth synchrony and variability in recent years suggest the presence of conditions that are limiting for growth. This study provides the first assessment of the responses of Iberian populations of P. pinea to changes in climate.

There were trade-offs between acorn production and stem growth in individuals of Quercus ilex , and these occurred with annual and intra-annual periods. The costs of reproduction differed significantly between two study sites. Reproduction in trees often requires significant resources, and previous studies have documented trade-offs between reproduction and growth in numerous tree species. In the present study, we assessed the relationships of acorn production with annual and intra-annual stem growth of Quercus ilex L. (holm oak) at the level of the individual tree over 6 years (2006–2011) at two study sites in southwestern Spain. There were negative correlations between acorn production and annual and late summer–autumn stem growth during masting years. In other words, the growth rates were lower in trees that had greater acorn production. These results suggest the existence of trade-offs between growth and reproduction in Q. ilex. However, there was no relationship between acorn production and winter–spring growth. Moreover, the costs of reproduction varied between the two study sites. There were negative correlations between acorn production and late summer–autumn growth in both study sites, but there were only negative correlations between acorn production and annual growth in one study site. Trade-offs appear to be greater in smaller trees living under more stressful conditions. These results show the importance of making intra-annual measurements of tree growth for appropriate interpretation of potential trade-offs.