Rainfall partitioning dynamics in xerophytic shrubs: Interplays between self-organization and meteorological drivers

Rainfall partitioning is a critical process shaping local hydrological cycles by governing canopy interception and subsequent soil water recharge. While canopy structure and meteorology are fundamental regulators, the role of plant self-organization and its interaction with meteorological drivers (non-precipitation variables in particular) remains underexplored. Here, this study investigated rainfall partitioning components, including the amount, intensity, efficiency, and temporal dynamics of throughfall and stemflow, in clumped versus scattered Vitex negundo shrubs in the Yangjuangou catchment of the Chinese Loess Plateau during the 2021–2022 rainy seasons. Despite comparable net precipitation (clumped: 83.5% vs. scattered: 84.2% of incident rains), divergent rainfall partitioning strategies emerged. Clumped V. negundo produced significantly higher stemflow (8.6% vs. 5.2%) with greater intensity, efficiency and favorable temporal dynamics, whereas scattered shrubs favored throughfall generation (79.0% vs. 74.9%). While rainfall amount remains the primary control, an integrated machine learning and variance decomposition analysis revealed that antecedent canopy wetness and wind speed thresholds (e.g., low wind vs. gusts) critically regulate partitioning efficiency and temporal dynamics. These findings advance the mechanistic understanding of the interplay between plant self-organization and hydrological processes, demonstrating how morphological adaptations in V. negundo optimize water harvesting in semi-arid ecosystems. Our results underscore the necessity of incorporating the dynamic interplay between plant structure (specifically, self-organized patterns) and meteorological factors (particularly non-precipitation variables) into ecohydrological models to improve predictions in water-limited regions.