Growth trends and sensitivity to climate of declining Mediterranean open woodlands exhibiting widespread mortality in Southern Spain

Abstract

We present two chronologies of dead and weakened Quercus ilex trees from declining open woodlands of Southern Andalusia and discuss climate's implication in the current widespread mortality in these ecosystems. Basal area increments were used to find out periods of growth decline preceding death. Absent rings became frequent since the 1970s, coinciding with increasing drought. Negative pointer years matched dry years and became more pronounced in the last decades. Growth was correlated with the annual Palmer Drought Severity Index and precipitations from previous October to May. Mean sensitivity increased recently, ranging between high values (0.35-0.5). Correlations with spring temperatures turned from positive to negative, positive correlations with current autumn precipitation arose whereas significant positive correlations with summer precipitations were no longer observed. These changes could suggest modifications on tree phenology. Intensively-used Mediterranean open woodlands of Southern Andalusia are vulnerable and the current dying process suggests that they are unlikely to overcome increasing stress climatic conditions.