Local- and global-scale hydrological and sediment connectivity over grassland and shrubland hillslopes

• Network theory quantifies water and sediment connectivity across hillslopes. • Shrublands show a tenfold increase in local connectivity metrics over grasslands. • Global network properties remain stable despite local connectivity changes. • Sediment connectivity is more tightly linked to structure than hydrological. • Connectivity is primarily shaped by rainfall events, unaffected by soil moisture. Quantifying connectivity patterns in dryland ecosystems enables us to understand how changes in the vegetation structure influence the runoff and erosion processes. This knowledge is crucial for mitigating the impacts of climate change and land use modifications. We quantify the multi-scale water-mediated connectivity within grassland and shrubland hillslopes using a weighted, directed network model. By integrating high-resolution elevation data, vegetation information, and modeled event-based hydrologic and sediment transport, we assess both structural connectivity (physical landscape layout) and functional connectivity (dynamic water and sediment movement) under varying rainfall and soil moisture conditions. Our findings reveal a marked increase in local (patch-scale) connectivity metrics in shrublands compared to grasslands. Metrics like betweenness centrality—which measures the importance of nodes in connecting different parts of the network—and the weighted length of connected pathways increase up to tenfold in shrublands. Despite substantial local changes, global (plot-scale) properties like efficiency of water and sediment transfer show less variation, suggesting a robust network topology that sustains geomorphic functionality across different vegetation states. We also find that the functional connectivity is more strongly correlated with structural connectivity for sediment than for water. This difference is particularly pronounced under high rainfall conditions and shows little sensitivity to variations in antecedent soil moisture, highlighting the critical role of rainfall-driven processes in shaping connectivity patterns. The study offers a comprehensive framework for analyzing connectivity at multiple scales, which can inform targeted management strategies aimed at enhancing ecosystem resilience, such as interventions to control erosion or restore vegetation patterns.