Caragana korshinskii of different planting years altered the soil water, carbon, and nitrogen storage in the different layers within level ditch on slope in a semi-arid area

Vegetation restoration can sequester more carbon to address global climate change and conserve biodiversity to maintain soil ecological functions. The combination of engineering measures and afforestation is a prominent strategy to restore degraded slope ecosystems. Engineering measure alters slope topography and reconstructs the microtopography which is differed completely from other positions; however, the studies about the effects of afforestation on the deep soil environment within microtopography are still unclear. In this study, the changes of the soil water in the different layers of 0–4 m and the soil carbon and total nitrogen in that of 0–1.2 m in the level ditch combined with C. korshinskii planted for 17 years (17y), 28 years (28y), and 36 years (36y) were analyzed, and naturally restored slope was used as the control (CK). The results showed that compared with CK, the soil water storage (0–4 m) under 17y, 28y, and 36y was significantly decreased by 22.9 %, 26.8 %, and 36.5 %, respectively. The soil water storage (2–3 m) under 28y and 36y was evidently decreased by 29.0 % and 41.7 % compared with 17y, and the one (3–4 m) under 36y was significantly decreased by 13.8 % and 21.5 % compared with 17y and 28y, respectively. The soil carbon/nitrogen storage (0–1.2 m) was decreased by 40.5 %/41.7 % under 17y and was increased by 20.6 %/22.4 % under 28y compared with CK, the one under 28y and 36y was significantly higher 103 %/110 % and 81.5 %/82.8 % than that under 17y. Based on stepwise regression analysis, shrub volume and slope significantly impacted water storage and carbon/nitrogen storage, respectively. The significant differences in the effects of C. korshinskii of different planting years on soil water storage were mainly found in deeper layers. Our findings provide insight into the alterations of the deep soil environment within the microtopography reconstructed by engineering measures in the context of vegetation restoration.