Impacts of vegetation change on contribution of recycled moisture to precipitation on the Loess Plateau

Clarifying the impacts of vegetation change on recycled moisture and precipitation is essential for understanding the land–atmosphere feedback and managing regional water resources. The objective of this study is to investigate the effects of transitioning from shallow-rooted crops (maize) to deep-rooted apple trees (18 and 26 years old) on the moisture recycling and local precipitation in the loess-covered region. After determining the time series of the δ²H and δ¹⁸O of advection, evaporation, and transpiration moisture, we quantified the contribution of recycled moisture to precipitation for different vegetation types based on the three-component mixing model and interpreted how vegetation change influence moisture recycling. The results indicated that 21 ± 10 % of precipitation was sourced from recycled moisture, the transpiration and evaporation contributed 13 ± 6 % and 8 ± 4 % to precipitation, respectively. Compared to farmland, the recycled moisture flux in apple orchards increased by 5 % to 10 %, with the moisture flux of transpiration increased by 18 % to 27 %, while the evaporation decreased by 11 %. The seasonal variation of moisture recycling ratio could be attributed to the positive impact of temperature and the negative impact of relative humidity. We conclude that transpiration moisture was the main source of recycled moisture, and the transition from shallow- into deep-rooted plants significantly increased the contribution of recycled moisture. The findings help to deeply understand land–atmosphere hydrological cycle processes on the Loess Plateau.