Fig. 2. (a) Linear relationship between Gs at VPD = 1 kPa (Gs-ref) and b) tree
hydraulic conductance (Ktree) and between the sensitivity of canopy conductance to
vapor pressure deficit (dGs/dlnVPD) and Gs-ref. Circles represent natural forests
and triangles loblolly pine plantations. Red and white symbols represent coastal
and Piedmont regions, respectively. In (b), the dashed line (slope = 0.6) indicates the
theoretical slope between stomatal conductance at VPD = 1 kPa and stomatal
sensitivity to VPD that is consistent with the role of stomata in regulating minimum
leaf water potential (Oren et al., 1999). (For interpretation of the references to color
in this figure legend, the reader is referred to the web version of this article.)