3.3. Effects of soil drying on tree transpiration and tree resistance to
soil drying
The hydraulic model yielded reasonable estimates of
canopy-scale transpiration (Fig. A1). Reflecting substantial embolism
of roots under drought, Ktree decreased with decreasing soil
water potential (Fig. 5). The largest modeled change of Ktree
occurred in L. styraciflua and in T. distichum at the Piedmont and
coastal sites, respectively (data not shown). The decrease in daily
E was mainly explained by the change in Ktree, which followed a
non-linear response. However, in both natural forests, Ktree
remained at its maximum value for soil water potentials above
0.3 MPa, corresponding to a REW ranging from 1 to less than
0.2 (filled arrows in Figs. 5 and 6).