黄河东岸沙地不同配置防护林土壤水同位素特征及对土壤水分运移的指示OA

[Objective]Soil water movement is a key process in the water cycle.Investigating the soil water movement processes and their driving factors in different forest stand configurations can provide a scientif-ic basis for vegetation construction and stand structure adjustment on the Loess Plateau.[Method]This study focused on the shelter-forest of Caragana korshinskii,Robinia pseudoacacia and the mixed forest of Caragana korshinskii × Robinia pseudoacacia in the eastern sandy land of Yellow River in Ningxia.Stable hydrogen and oxygen isotope techniques,together with the lc-excess equilibrium equation,were used to analyze soil water transport processes and the factors influencing soil water movement in pure and mixed stands.[Result](1)Soil hydrogen and oxygen isotopes in all stand types gradually became depleted and stabilized with increasing the soil depth.Compared with the pure forests,the mixed forest of Caragana kor-shinskii and Robinia pseudoacacia showed a higher coefficient of variation and relatively greater enrich-ment in soil water isotope variations,indicating less mixing between new and old water during infiltration.From May to October,the average soil water storage of each forest stand followed the order:the pure stand of Caragana korshinskii(158.53 mm)＜the pure stand of Robinia pseudoacacia(169.13 mm)＜mixed forest of Caragana korshinskii × Robinia pseudoacacia(Mixed)(194.78 mm).In contrast,the de-gree of soil water deficit followed the order:the pure stand of Caragana korshinskii(28.7％)＞the pure stand of Robinia pseudoacacia(24.7％)＞mixed forest of arbor and shrub(21.1％).(2)The lc-excess equi-librium equation showed that the relative contribution of preferential flow followed the order:mixed forest of arbor and shrub(23.5％)＞the pure stand of Robinia pseudoacacia(17.7％)＞the pure stand of Caragana korshinskii(15.9％).Preferential flow in the pure stand of Caragana korshinskii occurred in the mid-deep layer soil,the pure stand of Robinia pseudoacacia stands in middle layer soil,and mixed forest of arbor and shrub stands in the middle layer soil.(3)Total porosity was the primary factor influencing soil water movement in pure stands.However,its influence weakened in the mixed stand,where fine root biomass played a more important role.Preferential flow in the mixed stand mainly occurred during the middle of the growing season when rainfall was relatively high,whereas in pure stands of Caragana korshinskii and Robinia pseudoacacia,it mainly occurred during the early and late growing season.[Conclusion]Com-pared with pure forests,the mixed stands enhanced soil water storage capacity,reduced the degree of soil water deficit,and improved soil water retention.Additionally,the mixed stands enhanced the relative contri-bution proportion of preferential flow in soil water.However,during periods of low rainfall,preferential flow was insufficient to replenish the rhizosphere soil water.Astranspiration demand increased,soil water defi-cit in forest land became more severe,which may ultimately lead to soil desiccation.