Table 1 Summary of soil and plant water pools and associated extraction methods
From: Demystifying stable hydrogen isotope offsets between plants and source waters
Water worlds/pools | Water extraction method | Specific conditions | Number of sites | Proportions of all sites (%) | |
|---|---|---|---|---|---|
Soil | Gravitational soil water | Suction lysimeters | With a max tension of 50–70 kPa | 14 | 6.6 |
Passive-wick soil water samples | – | 1 | 0.47 | ||
Bulk soil water | Cryogenic vacuum distillation | Gravitational soil water is available | 144 | 67.92 | |
Azeotropic distillation | 11 | 5.19 | |||
Direct liquid-vapor equilibrium method | 4 | 1.89 | |||
Plant-available + hygroscopic soil water | Cryogenic vacuum distillation | Gravitational soil water is not available | 34 | 16.04 | |
Azeotropic distillation | 2 | 0.94 | |||
Plant-available soil water | Cryogenic vacuum distillation | Well-mixing and homogenous soil water in soil-potted experiments | 2 | 0.94 | |
Centrifuge set with a certain range of soil potential | Suitable for both field and potted conditions | None | – | ||
CO₂/H₂ equilibration method | Gravitational soil water is not available | – | – | ||
Plant | Bulk xylem water | Cryogenic vacuum distillation | – | 207 | 97.64 |
Azeotropic distillation | – | 2 | 0.94 | ||
Sap flow water | A high-speed centrifuge equipped with a cavitation flow rotor and custom-made sap flow water collectors | The empirical threshold between sap flow water and non-conducted tissue waters (−2 MPa for F.sylvatica branches) is provided | 1 | 0.47 | |
A flow-through whole-plant chamber coupled with a water vapor isotope ratio infrared | – | 1 | 0.47 | ||
Scholander pressure chamber | The sap flow water with a total of 0.5 ml is collected | 1 | 0.47 |
