Soil δ18O Research Articles

Water uptake from different soil depths for halophytic shrubs grown in Northern area of Ningxia plain (China) in contrasted water regimes

In order to understand the contributions of groundwater and deep soil water to the growth of halophytes in salinity-affected area, water use strategies of four shrubes, i.e. 20-year-old Tamarix ramosissima Ledeb., three-year-old T. ramosissima., Lycium barbarum L., and Atriplex canescens (Pursh) Nutt. were studied under contrasted water regimes in Northwest China. The result showed that there was a vertical gradient in soil δ18O and δD profiles resulted from evaporation and irrigation. The 20-year-old T. ramosissima mainly used water from middle (40–140 cm) and deep (140–200 cm) under both water regimes indicating its phreatophytic nature. Soil water in upper profile (0–40 cm) was the dominant water source for the three-year-old T. ramosissima before irrigation. After irrigation, the three-year-old T. ramosissima and L. barbarum switched their water sources to middle soil profile. Our experiment revealed phreatophytic tendency for the three-year-old A. canescens, which was not responsive to irrigation enlighten by photosynthetic parameters and stem water potentials.