A rising atmospheric vapour pressure deficit (VPD) increases forest transpiration and depletes soil moisture reserves, exposing trees to stress and reducing groundwater recharge. How stand water consumption varies with the species composition, is not well known, but is crucial for managing water resources. We measured stand-level transpiration of nearby pure European beech, Norway spruce and Douglas fir stands and a beech-Douglas fir mixture on deep sandy soil with sap flux systems during a wet and a dry year to compare the species' water use patterns under varying water availability and examine species mixing effects. In the wet year, pure Douglas fir consumed 123 % more water (472 mm yr