Cork extraction as a key factor determining post-fire cork oak survival in a mountain region of southern Portugal

Bark thickness, a key variable determining post-fire tree survival, usually increases with tree diameter. The cork oak (Quercus suber) is an exception to this, as it is the only European tree where the commercial exploitation of bark (cork) occurs. Human management thus becomes the most influential factor determining bark thickness. In this paper, we describe the survival rates and variables affecting cork oak survival 1.5 years after a large wildfire in southern Portugal, with a focus on the management of bark exploitation. The status of 1151 cork oaks was assessed in 40 sampling plots, and logistic regression used to explore the variables affecting survival likelihood, collected at the tree and plot levels. Survival rate was 84%. The most important factors affecting survival were those related to the management of cork extraction: stripped trees, trees with thinner bark and trees with larger diameter, correlated to the number of stripping operations, showed lower survival. Survival also decreased with increasing charring height, an indicator of fire damage. Stripped trees in unfavourable aspects (South to East) also showed lower survival. A survival model was built that can be used to identify areas vulnerable to future fires, if spatially explicit data on stand structure and cork management status are available.