| Impacts of land use change on sources of soil water recharge |
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| DOI：10.7606/j.issn.1000-7601.2023.03.21 |
| Key Words: land use change isotope tracing soil water source Loess Plateau |
| Author Name | Affiliation | | GAI Haoqi | College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China | | SHI Peijun | College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China | | LI Zhi | College of Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China |
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| Abstract: |
| To explore the deep soil water recharge sources under different vegetation, the Changwu Loess Tableland was chosen as the study area, and soil samples from the surface down to 20 m under two land use types (farmland, 18-year apple orchard and 26-year apple orchard) were collected and then the contents of soil water, stable (δ2H and δ18O) and radioactive (3H) isotopes were measured. Based on the isotopic method, the source of soil water at different depths under different land use types was traced. The results showed that (1) Soil water content under apple orchards was significantly lower than that of farmland, indicating that orchards consumed water more intensely and had a significant impact on deep soil water. (2) The precipitation offset values were -22‰, -20‰ and -6‰ under farmland, 18-year and 26-year apple orchards, respectively, indicating that soil water was affected by evaporation after the rainfall recharge. Specifically, orchards had lower evaporation effects. (3) Soil water movement in this area was predominantly via piston flow. For the possible soil water source at different depths, the isotopic composition of the recharge water below 6 m (δ2H =-83.8‰，δ18O =-12.1‰) was more depleted than that of 0~6 m (δ2H =-68.8‰，δ18O =-10.1‰), and the hydrogen and oxygen stable isotope composition of the recharge water below 6 m and the precipitation intensities ≥50 mm·d-1were very similar. Compared with farmland (δ2H =-70.6‰，δ18O =-10.4‰), the hydrogen and oxygen stable isotope composition of orchard soil water (δ2H =-76.1‰，δ18O =-11.1‰) was more depleted. These results suggested that deep and orchard soil water was recharged by higher\|intensity precipitation and had important implications for the understanding of water cycle process and water resource management in deep unsaturated zones. |
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