of water applied to 606 mm. During this season there were
many rainy days, which contributed to the decrease in VPD values.
Air temperature (T) and vapour pressure deficit (VPD) presented
the same behaviour during the three seasons studied, with absolute
maximum values in summer of 43.8 ◦C, 42.4 ◦C and 38.3 ◦C in 2009,
2010 and 2011, respectively. The minimum values were reached in
winter, as is typical in a Mediterranean climate. Interestingly, ET0
showed the maximum values one month earlier than VPD and T
(Fig. 1A).
According to the soil water content and the evaporative
demand, stem water potential (stem) values oscillated around
−0.71,
−0.65 and
−0.64 MPa in spring, with VPD values of less
than 2 kPa, and
−1.06,
−1.03 and
−1.02 MPa in summer, with
VPD values more than 4 kPa, for the three seasons, respectively
(Fig. 1D)