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