Water use strategies of coexisting shrub species in the Yellow River Delta, China

In coastal ecosystems, water availability is limited because of the high soil salinity influenced by sea water intrusion, high soil noncapillary porosity, and significant seasonal fluctuation of precipitation. Therefore, water availability is a key determinant of plant growth and distribution in coastal ecosystems. Tamarix chinensis Lour. and Ziziphus jujuba var. spinosa Hu are two coexisting shrub species growing on Chenier Island in the Yellow River Delta (YRD), China. Our aim was to investigate how the water-use strategies of the two species respond to variations in soil moisture to improve understand of their adaptations to drought stress and their coexistence mechanism. During the growing season, the oxygen stable isotope signatures (δ18O) were measured for soil water in different soil depths (0–20, 20–40, 40–60, and 60–100 cm), shallow groundwater, and xylem water. The proportional contributions of potential water sources for the two species were calculated by using the IsoSource mixing model. The r...