Growth rates and Huber values
Decreasing DGW significantly influenced the seasonal patterns of assimilation area per branch, especially during the EGS (Fig. 7). The average assimilation area accumulation per branch at each trial day was greater in the shallow DGW sites than the deeper DGW sites during the EGS (Fig. 7a). The growth rate of the branch assimilation area was greater in the shallow DGW sites than the deeper DGW sites in the same trial phase during the EGS (Fig. 7a and b). The branch assimilation areas and growth rates were not significantly different among sites on the same trial day during the LGS (Fig. 7a and b); growth rate slowed and even became negative during the LGS as a result of summer droughts (Fig. 7a and b). The mixed models revealed that growth stage had a significant influence on the relationship between DGW and growth rate & Huber values (F =5.07, P <0.01; F =6.23,P <0.01, respectively). We saw growth rates in assimilation branches decrease as DGW increased during EGS (Fig. 8a) but not LGS (Fig. 8b). Huber values increased as DGW increased during the EGS (Fig. 8c) but not during the LGS (Fig. 8d).