Optimizing the Spatial Configuration of Farmland Shelterbelts in Arid Oases under Hydrological Constraints: A SWAT-Based Scenario Analysis

In arid environments, farmland shelterbelts are essential for harmonizing limited water resources with ecological and agricultural expansion. These systems function as critical protective barriers that enhance environmental stability and crop productivity by curbing aeolian erosion and refining local microclimates. However, the transition in irrigation techniques has diminished lateral seepage, leading to intensified water stress and heightened risks of shelterbelt degradation. Current spatial planning often fails to sufficiently integrate hydrological equilibrium with habitat suitability. To address this research gap, this study develops a multi-objective framework for spatial afforestation. The approach couples the SWAT distributed hydrological model with a vegetation-specific water demand simulation to evaluate the establishment potential of Populus alba var. pyramidalis. Two distinct irrigation regimes—traditional border irrigation and low-pressure pipe irrigation—were simulated to compare their impacts on afforestation capacity. The results indicate that evapotranspiration represents the primary component of water consumption, followed by surface runoff and lateral flow. The findings reveal a spatial gradient in afforestation potential, which decreases progressively from the central irrigation districts toward the desert peripheries. Under traditional irrigation regimes, agricultural intensification zones can support a higher tree density, whereas the transition to low-pressure pipe irrigation necessitates an adjustment in the optimal density range. These outcomes provide a scientific foundation for coordinating water allocation between forestry and agriculture, refining shelterbelt configurations, and fostering long-term ecological sustainability in water-limited regions.