Assessment of climate change impacts on cork oak in western Mediterranean regions : a comparative analysis of extreme indices

Sammanfattning: Mediterranean regions have a growing number of extreme weather events due to rapid change of climate. Cork oak, which is located in the western Mediterranean area, has become a very valuable resource within the western Mediterranean forests. Therefore, assessment of the impacts of climate extremes upon cork oak can help us produce better forest management practices for coping with future climate change, and to achieve the purpose of sustainable development of the ecosystems and societies within the Mediterranean area in the future. In order to have a comprehensive understanding of how climate affects cork oak, climate extremes are investigated for western Mediterranean regions, especially Portugal and Northwest Africa. 15 indices of frequency and intensity indicators were derived from daily maximum temperature and daily precipitation data of the period from 1979 to 2009, and used in this investigation. Overview maps of the annual maximum temperature and annual precipitation sum distribution were plotted. Exploratory Factor analysis (EFA) was applied to find out the underlying temporal variance for those indices. And on this basis, 15 indices were simplified into several variables. Correlation analysis is adopted to identify the relationship between those climate variables that generated by EFA and cork production. Burned area was also involved in this analysis as a special case in Portugal. A Regression model was developed to make a prediction of cork production by viewing those climate factors as dependent variables. The results of those analyses show that as annual rainfall and maximum temperature changes, distribution of cork oak stands may have a potential of moving to the northwest. Northwest Africa is the recipient of climate extremes, especially hot and dry extremes, with higher frequency and intensity compared to Portugal. Summer dry extremes rather than rainfall extremes, can have considerable effect upon cork production, while burned area shows no correlation with cork production.