ABSTRACT
In order to apply isotope methods towards enhancing our understanding of water movement through the soil-plant-atmospheric continuum, thye authors first determine what controls water movement through each separate compartment. Water movement in soils and into plant root systems will be a complex function of soil properties, root anatomy and morphology and the stability of water sources which plants may use at different times or from different depths. Root water uptake will also be determined by ‘demand’ by the plant canopy and patterns by which stomata regulate water loss from leaves. The use of stable hydrogen and oxygen isotopes in studies of plant water relations has dramatically improved our ability to link plants to their source water through nondestructive means. Isotopes have also allowed researchers to examine temporal shifts in water use that cannot be determined from documenting the location of roots in the soil profile.
