Elevation and local climate variation control changes in Aleppo pine growth responses to hydroclimate and drought in semi-arid Spain

Abstract

In the Mediterranean region, inner rural and mountain areas suffered abandonment and land marginalization. Extensive conifer afforestations were established in these areas, which are particularly vulnerable to climate change and its associated risks. To identify critical areas where climate change could negatively impact forest vitality, we need to understand how the temporal variability of tree growth and its vulnerability to climate and drought have arisen and what their possible causes are. We used dendrochronological techniques to examine the effects of stand structure, physiography, and local climate variations in determining the growth dynamics of Aleppo pine plantations and temporal shifts in their susceptibility to hydroclimate and drought in semi-arid northeastern Spain. We found that structural traits strongly modulated growth dynamics and forest productivity. Young and small trees showed more synchronized growth and greater inter-annual ring width variability, and widely spaced trees in better quality stands had higher productivity. In contrast, temporal shifts in growth susceptibility to hydroclimate and drought were dependent on local physiography and climatic variability. Trees in low-elevation eastern stands with less continental conditions and milder winters showed decreasing dependence on water availability and increasing growth resistance and resilience to severe droughts. However, in high-elevation sites with wetter climates and cold winters, increasing growth response to water availability and decreasing resistance and resilience to drought were found. Our results highlight that adaptation to local physiographic and climatic conditions is a better strategy to mitigate the impacts of climate warming on Aleppo pine plantations in the semi-arid Mediterranean region.