| Soil salinization is one of the ecological issues of great concern around the world.The Tarim River Basin is located in the arid region of the northwestern China,where soil salinization is widely developed.The mutual feedback mechanism between typical suitable vegetation and the transport of water and salt in groundwater and the vadose zone is one of the urgent problems to be solved for the ecological restoration and sustainable development of salinized regions.In this paper,taking the Qiala Reservoir to Daxihaizi Reservoir section in the lower reaches of the Tarim River as the research subject,by means of combination regional eco-hdrogeological survey with indoor analysis,in-situ monitoring and numerical simulation,and the succession law of vegetation in arid regions with groundwater tabel burial depth and TDS of groundwater was discussed.Based on the monitoring data of the vadose zone and groundwater obtained from the field site in-situ,the conceptual model and mathematical model of the influence of Tamarix chinensis Lour.Shrubs on water and salt transport of groundwater were established by means of Hydrus-1D software,and the influence of Tamarix chinensis Lour.Shrubs on water and salt transport of groundwater and the vadose was simulated.The following results were achieved:1.Succession law of natural vegetation in the lower reaches of the Tarim River was discussed.Through regional eco-hydrogeological survey,a successional map of the natural vegetation with buried depth of groundwater table and TDS of groundwater in the lower reaches of the Tarim River was constructed.2.Characteristics of moisture and salt transport in the vadose zone and groundwater under Tamarix chinensis Lour.Shrubs.The analysis of field monitoring data based on the soil and groundwater in-situ showed that moisture of the vadose zone showed a gradual increase with the increase of buried depth.Fine content at 60 cm depth below the surface was higher,and its moisture was higher than that of adjacent soil layers.Salinity of shallow soils is in the conrtary to moisture content in soils.That is the lower moisture content,the higher salinity.3.Influence model of Tamarix chinensis Lour.Shrubs on the moisture,heat and salt transport in the vadose zone and groundwater was constructed.Based on the monitoring data of the vadose zone and groundwater in-situ,a conceptual model and a mathematical model of the influence of Tamarix chinensis Lour.Shrubs on the moisture,heat and salt transport in the vadose zone and groundwater were established,and the relevant hydraulical and thermodynamic parameters,and solute dispersion were obtained after identification and verification.4.Numerical simulation of the influence of Tamarix chinensis Lour.Shrubs on moisture,heat and salt transport in the vadose zone and groundwater.Using the optimized model parameters,three scenarios of different burial depths of groundwater table,TDS of groundwater and presence or absence of vegetation from May to September,2021 were simulated.The simulation results show that: With the increase of the burial depth of groundwater tabel and certain TDS,the evaporation and transpiration on the surface decrease,but the proportion of root water absorption increases;The salt limit on the surface is gradually decreased.With the increase of TDS of groundwater and certain buried depth of groundwater tabel,the amount of surface evaporation and the amount of salt on the surface are almost unaffected,and the amount of transpiration has only a slight impact.With certain TDS,evaporation and salt of bare soil on the surface when the shallow buried depth of groundwater tabel increase linearly and rapidly,and vegetation helps to inhibit evaporation and salt on the surface,and to alleviate salt on the surface.The research results above have important theoretical significance and practical value for the ecological restoration of salinized regions located in arid climate zones,the sustainable development of watersheds and the safety of the Tarim River Green Corridor. |
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