3.2. Isotopic compositions in precipitation, plant water, soil water, and groundwater
The δ18O and δ2H values in the two sites varied greatly between water sources and months (Figure 3). The average values of δ2H were -53.86‰, -52.25‰, -45.95‰, and -38.48‰ for groundwater, precipitation, soil water, and plant water, respectively. The respective average values of δ18O were -8.83‰, -8.65‰, -6.93‰, and -2.96‰. Considering precipitation, soil water, and plant water, a progressive increase in δ18O or δ2H existed from precipitation to soil water to plant water for each month (Figure 3). Moreover, the δ18O and δ2H in precipitation water increased initially and then decreased significantly from May to October (p < 0.05). The δ18O and δ2H of plant water responded well to the trends of precipitation from May to July, but not well from August to October. The δ18O and δ2H of soil water and groundwater showed no significant differences across months for the two sites (p>0.05). Groundwater isotopes were consistent with the deeper soil, remained relatively stable.
Precipitation Plant water Ground water Soil water