宁南黄土高原退耕还林(草)区包气带土壤水分运移特征及对降水的响应OA

[Objective]The loess hilly region in southern Ningxia is ecologically fragile and naturalising farmland is a way to restore its ecological functions.While soil water is a key factor regulating ecosystem functions and stability,its response to rainfall in naturalised farmlands is not well understood.This paper investigates the spatiotemporal soil water dynamics and its response to rainfall in such ecosystems.[Method]Based on rainfall and soil moisture data measured from April to October 2023 in the vadose zone of a typical grassland(CD)and farmland(NT)in the southern Ningxia,we analysed the characteristics of soil water movement and their response to rainfall in the two ecosystems.[Result]① Light rainfall events only replenished the top 10 cm soil layer,while moderate rainfall events replenished the 0-30 cm soil layer.Under moderate rainfalls,noticeable soil moisture changes were observed mainly in the 10 cm and 30 cm layers in both ecosystems.② There were significant differences in the response time and magnitude of soil moisture change to rainfall events between the two ecosystems.The maximum average soil moisture content in NT and CD was in the 30 cm layer and the 10 cm layer,respectively.The effect of rainfall on soil moisture content dwindled as soil depth increased.③ Soil water balance analysis showed that the evapotranspiration of NT was significantly lower than that of CD,while its water percolation into deep soil was higher than that in CD.It was found that NT enhanced water infiltration into deep soil,thereby increasing groundwater recharge.[Conclusion]Our results unveiled the fundamental mechanisms underlying soil water movement in farmland and naturalised farmland in loess hilly region of southern Ningxia;they provide guidances for restoring the ecological functions of ecologically fragile areas in this region.