Plants in different sites used different fractions of shallow, middle, and deep soil waters during different growth periods (Figure 6). The plant water utilization of shallow soil water ranged from 19% to 52%, and the minimum value at the shrub site was on 16 July. In contrast, the maximum value was observed at the grassland site on 15 June. The proportional contributions of middle soil water and deep soil water acquired by plant were 55% and 50%, respectively, at the shrub site. At the onset of the growing season and fast-growing season from May to July, plants at shrub and grassland sites extracted water from the middle soil layer and the shallow soil layer, respectively. Water utilization from shallow, middle, and deep soil water reached equilibrium in August. The water contributions of the three layers remained unchanged during the late growing season and withering season. The plants at the shrub site had higher degree of flexible plasticity in water use compared with the plants at the grassland site.