Browsing by Author "Wang, Ninglian"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Contribution of recycled moisture to local precipitation in the inland Heihe River Basin
    (Elsevier, 2019-06) Zhao, Liangju; Liu, Xiaohong; Wang, Ninglian; Kong, Yanlong; Song, Yaoxuan; He, Zhibin; Liu, Quanyu; Wang, Lixin; Earth Sciences, School of Science
    Recycled moisture contributed by continental evaporation and transpiration plays an important role in regulating the hydrological processes and atmospheric humidity budget in arid inland river basins. However, knowledge of moisture recycling within many large inland basins and the factors that control moisture recycling is generally lacking. Based on a three-component isotopic mixing model, we assessed the characteristics of moisture recycling in China’s semi-arid Heihe River Basin. During the active growing season, almost half of the precipitation in the upper reaches was provided by local moisture recycling, and the main contribution came from transpiration. In the middle reaches, almost half of the precipitation in the artificial oasis and the desert-oasis ecotone was also provided by local moisture recycling, and the transpiration fraction (fTr) and evaporation fraction (fEv) of the artificial oasis differed from those of the desert-oasis ecotone. In the lower reaches, less than 25% of the precipitation was provided by local moisture recycling. Mean fTr values were relatively low in the Gobi (15.0%) in the middle reaches and in the riparian forest at Ejina (25.6%) in the lower reaches. The positive correlations between fTr and both precipitation and relative humidity suggest that higher precipitation and relative humidity promote transpiration fraction, whereas higher vapor pressure deficit reduces transpiration fraction. The positive correlation between fEv and temperature and vapor pressure deficit, and the negative correlation between fEv and relative humidity indicate that higher temperature and vapor pressure deficit promotes evaporation fraction, whereas higher relative humidity reduces the evaporation fraction. Our results show that contributions of recycled moisture (especially transpiration) to local precipitation play an important role in regional water resource redistribution in the arid and semi-arid region of northwestern China.
  • Thumbnail Image
    Item
    The determining factors of hydrogen isotope offsets between plants and their source waters
    (Wiley, 2024-03) Zhao, Liangju; Liu, Xiaohong; Wang, Ninglian; Barbeta, Adrià; Zhang, Yu; Cernusak, Lucas A.; Wang, Lixin; Earth and Environmental Sciences, School of Science
    A fundamental assumption when using hydrogen and oxygen stable isotopes to understand ecohydrological processes is that no isotope fractionation occurs during plant water uptake/transport/redistribution. A growing body of evidence has indicated that hydrogen isotope fractionation occurs in certain environments or for certain plant species. However, whether the plant water source hydrogen isotope offset (δ2H offset) is a common phenomenon and how it varies among different climates and plant functional types remains unclear. Here, we demonstrated the presence of positive, negative, and zero offsets based on extensive observations of 12 plant species of 635 paired stable isotopic compositions along a strong climate gradient within an inland river basin. Both temperature and relative humidity affected δ2H offsets. In cool and moist environments, temperature mainly affected δ2H offsets negatively due to its role in physiological activity. In warm and dry environments, relative humidity mainly affected δ2H offsets, likely by impacting plant leaf stomatal conductance. These δ2H offsets also showed substantial linkages with leaf water 18O enrichment, an indicator of transpiration and evaporative demand. Further studies focusing on the ecophysiological and biochemical understanding of plant δ2H dynamics under specific environments are essential for understanding regional ecohydrological processes and for conducting paleoclimate reconstructions.
  • Thumbnail Image
    Item
    Water sources of major plant species along a strong climatic gradient in the inland Heihe River Basin
    (Springer, 2020-10) Zhao, Liangju; Xie, Cong; Liu, Xiaohong; Wang, Ninglian; Yu, Zhang; Dong, Xiying; Wang, Lixin; Earth Sciences, School of Science
    Aim Knowledge on vegetation water sources is crucial to understand the ecohydrological processes and ecological management of arid and semi-arid ecosystems. The identification and quantification of plant water uptake from precipitation, soil and groundwater remain challenging along large climatic gradient. Methods Stable oxygen isotope compositions of xylem water, soil water and groundwater were analyzed to assess seasonal and spatial patterns of water uptake of 11 major plant species along the Heihe River Basin. Conclusions In the upper reaches, soil water recharged by precipitation was the main plant water source, and plants extracted water from the shallow soil water in wet season while used more deep soil water in dry season. In the middle reaches of desert-oasis ecotone, the water sources of shrubs shifted between soil moisture and groundwater depending on variations of precipitation and groundwater level, while shrubs at Gobi relied on deep soil water and shallow soil water after rainfall. In the lower reaches, the driest part of the region, groundwater and deep soil water were main water sources for the riparian plants. Groundwater was stable water source for shrubs growing on the planted shrubland, and soil water was stable water sources for shrubs growing at Gobi. Our results also revealed that water use strategies of the same species were plastic under different groundwater level and precipitation. This study identified water use patterns of different plant species along a climatic gradient and provided scientific implication for water management of different ecosystems of the arid and semi-arid ecosystems.