Agroforestry buffers drought stress by enhancing hydrological redistribution in dryland apple orchards

Water scarcity driven by intensifying drought poses a growing threat to agricultural productivity and ecosystem stability in drylands. Agroforestry systems, recognized as climate-resilient strategies, mitigate water stress through mechanisms like reduced runoff, suppressed soil evaporation, and optimized water partitioning. However, the persistence of these benefits under sustained drought remains poorly quantified. To address this gap, we conducted a four-year rainfall exclusion experiment coupled with process-based MAESPA modeling, evaluating the impacts of prolonged moderate (15 % reduction) and severe (25 % reduction) drought on the water balance of an apple tree–oil crop (ATOC) intercropping system (planted in 2017) on China’s Loess Plateau. Our key findings reveal that the hydrological benefits of agroforestry are highly dependent on drought severity. Under natural precipitation, the ATOC system increased the soil water content ( SWC ) by 3.5 %, increased transpiration by 39 %, boosted deep percolation by 11 %, and reduced soil evaporation by 10 % compared to apple monoculture. Under moderate drought, despite declines in SWC (-10 %), transpiration (-26 %), and deep percolation (-17 %) relative to the non-drought agroforestry system, transpiration remained 11 % and 15 % higher than in monoculture during normal and wet year due to a shift in water uptake to deeper soil layers. Under severe drought, this buffering capacity was overwhelmed. The ATOC system experienced substantial reductions in all water balance components—including SWC , transpiration, and deep percolation, highlighting its vulnerability to extreme water stress. These findings elucidate the conditional mechanisms through which agroforestry systems buffer drought stress and provide crucial insights for designing climate-resilient water management strategies in dryland landscapes. • Field–model integration quantifies water partitioning in apple-oil agroforestry under multi-year drought. • Agroforestry buffer drought by boosting soil water, transpiration, and deep percolation while reducing evaporation. • Under moderate drought, agroforestry keeps higher transpiration than monoculture by shifting uptake to deeper soil layers. • Severe drought exceeds buffering capacity, sharply reducing transpiration and soil water across the water balance.