Complementary water-use strategies mitigate drought impacts of mixed arbor-shrub stands in a loess gully area: A quantitative analysis

Aims The loess gully area is a key zone for large-scale revegetation programs in China; however, accurate prediction of mixed arbor-shrub stands responses to variable drought intensities remains poorly quantified. Therefore, quantitative understanding water use strategies of typical revegetation stands under drought is crucial. Methods Here, we quantitatively investigated the seasonal water use strategies of mixed Caragana korshinskii Kom. and Artemisia vulgaris Lam. in loess gully region during the growing season in 2023, basing on continuous monitoring of transpiration and 20 times sampling of δ²H and δ¹⁸O. Results The transpiration of A. vulgaris declined significantly in response to a summer drought by 19.7%, whereas that of C. korshinskii remained stable, indicating different drought resistance and resilience of these two species. Corresponding to different changes in transpiration, the two species also exhibited divergent water use strategies. In the wet spring, both species took up water predominantly from the surface layer (0–20 cm) (approximately 32.55% for C. korshinskii and 51.18% for A. vulgaris ). However, under the summer drought, C. korshinskii switched to soil water of the deep layer (60–110 cm, by 43.23%), whereas A. vulgaris mainly relied on soil water of the middle layer (20–60 cm, by 38.07%). Conclusion The ability to switch to different water sources indicated that the mixed arbor and shrub stands could reduce interspecific stress and improved drought resistance and resilience. This study enhances our understanding of species-specific water-use strategies in mixed arbor–shrub stands under summer drought, and provides hydrological insights for water resource management in water-limited areas.