No abstract

No abstract

Water resource shortage in arid areas is the main cause of ecological problems. Understanding plant water use patterns is essential for understanding soil–plant interactions and assessing the adaptability of plants in ecosystems with limited water resources. Riparian wetlands are functional transition areas connecting aquatic ecosystems and terrestrial ecosystems. Wetland vegetation restoration is of great significance to water conservation and ecological balance. Using isotope tracing method, our study clarified the water use patterns of dominant plants in typical riparian wetlands in arid areas. The results showed that the dominant herbal species of Salsola affinis mainly used 0–60 cm soil water (48.96%). Salsola affinis, which continuously obtains water from shallow soil, may be difficult to survive in extreme drought conditions. If it withered significantly aged in the dry season, it would have a negative ecological impact. The dominant tree species of Salix matsudana Koidz mainly used 20–100 cm soil water (43.99%) and groundwater (23.16%). With increasing water stress, S. matsudana Koidz had a greater degree of ecological plasticity and can use water from deeper soils. However, S. matsudana Koidz can continuously obtained water from deep soil and groundwater, which may weaken the water and soil conservation capacity of the wetland. In addition, the lc‐excess value of soil water showed that the soil evaporation intensity of grassland was higher than that of forest land, and the surface evaporation depth reached 60 cm. Our findings will help better understand the impact of vegetation restoration plan (artificial forest land and natural grassland) on the hydrological process of riparian wetland in arid areas, and provide reference for plant species selection and water resources management.

The dissolved organic carbon(DOC) content of rivers is the most active part of the carbon cycle migration in the basin under consideration, and it is the basis for a comprehensive understanding of the regional carbon cycle. In this study, we periodically took samples from four monitoring stations in the Xiying River Basin of the Qilian Mountains in the northern Qinghai-Tibet Plateau. We calculated the fluxes of organic carbon in the rivers within the study area and will discuss the influencing factors of Dissolved Organic Carbon concentration in these rivers in this paper. Our results showed that: (1) The DOC concentration and output flux in the inland river runoff area are basically the same as those in the Heihe River Basin, but far lower than those in the low-latitude monsoon climate zone and most of the basins in the Eurasian Arctic region. This is mainly due to the small river runoff and low DOC concentration in the area. (2) The Dissolved Organic Carbon concentration and transport flux of the rivers show significant seasonal changes, with the Dissolved Organic Carbon content in summer and autumn being higher than in winter and spring. (3) The larger runoff causes higher concentrations of dissolved organic carbon in rivers. Runoff is the primary means of carbon migration in the Inland River Basin. There are significant carbon migrations from the upstream to the middle and downstream sections of the Inland River Basin.

As the largest tributary of the Shiyang River, with the average annual inflow of total runoff accounting for 23%, the Xiying River has representative of mountain runoff of inland rivers in the Northwest of China. Using samples collected in this basin from September 2016 to October 2017, the water chemical composition and ion source characteristics of river were studied. The results show that the river is weakly alkaline, the average pH is 8.0 and the TDS is 179.29 mg·L-1. With the elevation decreasing along the river, the TDS of main stream tend to increase firstly and then decrease, but those of TDS of each tributary decrease, and latter is lower than the former. Affected significantly by the flow, the lowest value of ion concentration in river occurs in summer, and the highest occurs in autumn and winter. The hydrochemical type of river is CaMg-HCO3. In the river, the order of cation mass concentration is NH4+<K+<Na+<Mg2+<Ca2+, and that of anion is F-<NO3-<Cl-<SO42-<HCO3-. The sources of ions in river are mainly from the weathering of Silicates and Carbonates. With the elevation decreasing along the river, the influence of Silicates on the inflowing tributaries is gradually strengthened.