Quercus ilex forests are influenced by annual variations in water table, soil water deficit and fine root loss caused by Phytophthora cinnamomi

► Advances clarify the role of water in the decline of Quercus ilex forests. ► Provides data on soil water content and soil water table fluctuations in forests. ► Reports combined effects of root pathogens, water stress and waterlogging on trees. ► Small-scale differences in soil water-holding capacities explain symptoms. ► The combination of root damage and water stress determines tree survival.