Sensitivity of cork growth to drought events: insights from a 24-year chronology

Abstract

Increasing drought frequency and severity are expected in the Mediterranean regions that will increase their vulnerability and affect forest production and product quality. The sensitivity of cork growth to extreme drought events is analyzed using a 24-year chronology (1986–2009), including several drought occurrences, and is built using extensive sampling (1128 cork samples). The chronology is analyzed in relation to several climate variables e.g. precipitation, temperature and the standard precipitation evapotranspiration index (SPEI) at different time scales (1–24 months). The significant time scale at which drought affected most the cork growth is determined and a response function is built. The cork-ring chronology showed significant response to climatic variables with a relevant growth decrease in 1995, 1999 and 2005 matching the severe drought events of 1994–1995, 1998–1999 and 2004–2006. When drought conditions ended cork oaks recovered the cork growth revealing high resilience. High responsiveness and sensitivity to later spring precipitation is found with a cork growth increment in response to the increase of water availability. Cork growth is extremely hindered by drought conditions in short time scales (from 2 to 11 months). A scenario of decreased cork growth is expected as a result of climate adverse conditions, with implications in the raw-material industrial adequacy and therefore a strong impact on the overall economy of the sector.