Drought is the most important environmental constraint in Mediterranean-type climates, and has been associated with tree mortality episodes. This thesis investigates some of the adaptations of Quercus suber and Q. ilex trees to tolerate/avoid recurrent droughts. The study includes data on vegetative growth, xylem anatomy and vulnerability to embolism, xylem network topology, root architecture and functioning, stem and root sap flow, and water sources for transpiration. Results show that both species have similar seasonal growing patterns and vulnerability to xylem embolism. Q. suber has a dimorphic root system, with integrative xylem, whilst the xylem of the vertical axis (taproot-stem-branches) is sectored. Two modelling approaches were developed to estimate the soil and groundwater contributions to tree transpiration: one based on root sap flow and another on more commonly available environmental and physiological data. Simulations of both models converged in the quantification of soil and groundwater contributions (in summer) to tree transpiration. This study attempted to fill gaps in knowledge on above- and belowground functional behaviour of Mediterranean oaks, providing insights for the management and conservation of these ecosystems.

Doutoramento em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia