Rainfall determines the temporal stability of soil water content following the conversion of deep rooted to shallow rooted vegetation in arid regions

• The temporal stability of SWC after the conversion of deep-rooted vegetation to shallow-rooted vegetation has been studied. • Deep SWC has been effectively replenished after deep to shallow root vegetation. • With the increase of years of conversion to shallow root vegetation, the temporal stability of SWC increases. In arid regions, most of native tree species and afforested trees are deep rooted to take advantage of deep soil water content (SWC), and then deplete deep SWC and further influence groundwater recharge. And the conversion of deep-rooted vegetation to shallow-rooted vegetation is considered an effective way to alleviate deep soil drying. However, the spatiotemporal dynamic characteristics of SWC and their influencing factors after the conversion of deep-rooted to shallow-rooted vegetation remain unclear. Therefore, this study aimed to evaluate the spatiotemporal dynamic characteristics of SWC and influencing factors after the conversion from deep-rooted to shallow-rooted vegetation. Deep-rooted vegetation (Apple orchard, AO) and shallow-rooted vegetation (Croplands) converted by AO was taken as the research object, and the croplands converted by AO included those with conversion periods of 2, 4, and 6 years, which was abbreviated as CCA2, CCA4 and CCA6, respectively. In addition, cropland (CL) under continuous cultivation served as the control group. The SWC in 0–10 m soil layer was measured using a neutron probe between 2022 and 2024. Results showed the mean SWC was in the order: 18.20 % (AO) < 21.21 % (CCA2) < 22.24 % (CCA4) < 22.25 % (CCA6) < 24.11 % (CL). With increasing depth, the mean SWC of CCA2 and CCA4 first increased and then decreased, while that of CCA6 showed a continuous upward trend. With the increase in the number of years of returning to cropland, the temporal stability of SWC gradually increased. And the respective representative depths were as follows: 320 cm depth (CCA2), 340 cm depth (CCA4), and 380 cm depth (CCA6). Compared to soil particle composition and soil infiltration capacity, rainfall was the main factor affecting the temporal stability of SWC. This study enhances the understanding of soil moisture processes during the conversion from deep-rooted vegetation to shallow-rooted vegetation in arid regions.