Fig. 5

Impact of relative extractable soil water (REW) and VPD on the transpiration ratio (T* = T / T ₀) at noon observed on sites A and D. R ² was computed for dry conditions (i.e., REW < 15 %) for the T* vs. REW relationships (graphs on the left). For the T* vs. VPD relationships, lines correspond to the upper envelop of data (double exponential curve fitted on the highest values for each VPD of both sites). Unfilled points and the gray line correspond to wet soil (REW > 15 %), while filled points and the black line to dry soil REW < 15 %. Only data corresponding to high climatic demand (T ₀ > 0.15 mm h⁻¹ and R _n > 400 W m⁻²) are represented