Water sources of the typical desert vegetation in Ebinur Lake basin

In arid and semi-arid environments, desert vegetation plays an important role in preventing soil erosion by wind and maintaining the stability of the desert and oasis ecosystem. Four types of typical desert vegetation, namely, Populus euphratica, Haloxylon ammodendron, Nitraria sibirica and Halostachs caspica, in different habitats (i.e., banks, sand dunes, desert, and salt marshes) were chosen as the model vegetation in this research. The δ2H and δ18O of rain water, soil water and plant water were applied to identify the water sources and quantify the proportions of water used during the whole growth period (from March to October). The results showed that the precipitation δ2H and δ18O in the Ebinur Lake basin varied from -142.5‰ to -0.6‰ and from -20.16‰ to 1.20‰, respectively. The largest values of δ2H and δ18O were found in summer and the smallest ones in winter. The soil water δ2H and δ18O of the four habitats decreased gradually with the increase of the depth. The δ2H and δ18O values of water extracted from the four plant stems had similar variation trend, i.e., the maximum was observed in spring, and the minimum was in summer. Among the four plants, Halostachs caspica had the highest stable isotopic values in the stem water, followed by Nitraria sibirica, Haloxylon ammodendron and Populus euphratica. The water sources and utilization ratios of desert vegetation varied in different growth stages. In the whole growing period, Haloxylon ammodendron mainly used groundwater. The proportion of water used by Nitraria sibirica varied greatly throughout the growing season. In spring, plants mainly relied on surface soil water, with a contribution rate of 80%-94%; in summer, the proportion of deep soil water use was 31%-36%; and in autumn, the proportion of middle soil water use was 33%-36%. Halostachs caspica mainly relied on topsoil water in spring and autumn, and the proportion of soil water in the middle layer slightly increased in summer, which was 20%-36%. Populus euphratica mainly used the intermediate soil water in spring, with a utilization rate of 53%-54%; in summer, groundwater was the main source, with a utilization rate of 72%-88%, and only 2%-5% from river water; in autumn, the utilization rate of river water rose to 11%-21%. The results indicated that there were significant differences in water use sources during the growing season of desert vegetation in arid areas. This research provides a theoretical basis for understanding the water use mechanism, water adaptation strategies, and vegetation restoration and management of desert vegetation in arid areas. © 2021, Science Press. All right reserved.