Plants in different sites used different fractions of shallow, middle, and deep soil waters with different growth periods (Figure 6). The fractions from the shallow soil layer used by plant varied from 18.6% to 52.4%, 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 54.8% and 50%, respectively, at the shrub site. At the onset of the growing season and fast-growing season from May to July, plant 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 use contributions from the three layers remained unchanged during the late growing season and withering season. The plants at the shrub site had a higher degree of flexible plasticity in water use compared with the plants at the grassland site.