A review of groundwater-soil water-vegetation responses to ecological water replenishment in the riparian zone

Ecological water replenishment is an artificial intervention measure for restoring degraded riparian vegetation ecosystems. The hydro-ecological coupling effect can drive the vegetation response by regulating the groundwater level and soil moisture content, and this process has become an active area of research. This paper systematically reviewed the research progress on the impacts of ecological water replenishment on riparian groundwater level, soil moisture content and vegetation restoration, and summarized the future research priorities. Under ecological water replenishment conditions, groundwater level changes exhibit temporal accumulation and response lag effects. These changes also show distinct divisions both in the transverse and longitudinal directions of the river. This process is primarily controlled by hydraulic gradient and riverbed permeability. Groundwater can supply soil water under the influence of soil water potential gradients. The increase in soil moisture content effectively improves water availability for plants, alleviates drought stress, and consequently alters plant community structure and species diversity. Furthermore, the magnitude of this vegetation response is modulated by the amount, timing, and sustainability of water replenishment. Future research should focus on: revealing the mechanisms of groundwater level change driven by the coupling of multiple factors and processes; understanding soil water movement patterns under soil heterogeneity. Furthermore, it is essential to elucidate long-term vegetation succession patterns and to identify key environmental thresholds that trigger successional shifts under sustained ecological water replenishment; Building upon such mechanistic understanding, a coupled "water replenishment-groundwater-soil moisture content-vegetation response" model should be developed to ultimately guide the design of adaptive, multi-objective ecological water replenishment strategies.