Plant water use strategies indicated by isotopic signatures of leaf water: Observations in southern and northern China

Plants act as an important component in the terrestrial hydrosphere. To determine the relationship between vegetation and hydrosphere under different climate conditions of China, large-scale investigations and sampling campaigns were conducted in typical humid lake areas of southern China and in semiarid–arid regions of northern China. Hydrogen and oxygen isotopic signatures were used to reveal the water utilization characteristics of plants in these areas. The results suggest that isotopic signatures of plant leaf water can effectively indicate the water source used by plants. Vegetation in humid lake areas relies mainly on water supplement from surface water, whereas groundwater constitutes the primary water source for plant survival in semiarid–arid areas. The differences in the water utilization strategies of plants suggest considerable differences in the local hydrological processes between southern and northern China. Unlike the humid areas of southern China, the dependence of plants on groundwater in semiarid–arid northern China implies the difficulty for the sparse rainfall to infiltrate and recharge the groundwater system. This study demonstrated that the analysis of plant leaf isotopic signatures could constitute a useful method for further study of the controversial groundwater origin in northern China, which is important for maintaining ecological balance and alleviating the effects of serious water shortages.