Ecological responses to hydrological connectivity in grassland riparian zones: Insights from vegetation and ground-dwelling arthropods.

Riparian wetlands have suffered from degradation due to global climate change and human activities, which can alter flora and fauna community patterns and disrupt material cycles in the riparian zones. Hydrological connectivity identified by functional and structural connectivity is an important driving force of riparian ecosystems. However, the role of hydrological connectivity in linking riparian hydrology and ecology remains unclear, especially in dryland rivers. By taking the riparian zone of the Xilin River in Eurasian steppe as an example, the functional connectivity was represented by the groundwater depth in the riparian zones. The structural connectivity was quantified by integrating the soil, and vegetation properties of the riparian zone. The structural connectivity decreased from upstream to downstream. Laterally, the highest structural connectivity was found in the riparian zone 25 m away from the river channel. The abundance of three groups of ground-dwelling arthropods (except Araneae) showed a threshold behavior in response to the functional connectivity, with the highest abundance occurring in the medium level of functional connectivity. Both vegetation biomass and ground-dwelling arthropod abundance were significantly and positively correlated to the structural connectivity strength. The results of structural equation models (SEMs) also indicated that structural connectivity was a key factor affecting vegetation and ground-dwelling arthropod abundance. The results underscore the essential function of hydrological connectivity in maintaining the biodiversity in the riparian zones. The study provides a scientific reference of riparian-zone restoration based on hydrological connectivity.