Soil moisture ecological environment of artificial vegetation on steep slope of loess region in North Shaanxi Province, China

By means of fixed-point monitoring and comparative analysis, soil water deficient situation, soil moisture dynamic variation laws, soil aridization and soil water compensation features under condition of different artificial vegetations were studied on 35–45° steep slope of loess region in North Shaanxi Province, China. The results showed that soil water was extremely deficient under condition of perennial artificial vegetation on steep slope, soil water storage (0–10 m) was only equal to 26.2%–42.0% of the field capacity in dry years, and in rainy years it was also only equal to 27.0%–43.3% of the field capacity. The order of soil water deficit was Caragana microphylla > locust > alfalfa > Chinese arborvitae > poplar > Chinese pine > wild land > apricot > Chinese date > farm land. Annual variations of soil moisture with the same vegetation were weakened with soil depth increasing, and occurred mainly in 0–200 cm soil layers. In the same growth season, all CVs (coefficients of variation) of soil moisture under condition of different vegetations were bigger and concentrated comparatively in 0–120 cm soil layers, but difference of CVs in different vegetations was small. Below 120 cm soil layers, CVs were smaller, but difference of CVs in different vegetations was bigger. Permanent dry soil layers always occurred under condition of perennial vegetation on steep slope, but the difference of soil aridization intensity was obvious among different vegetations and growth years. Soil water compensation and recovery depths in rainy seasons were 1.0–1.4 m, but the soil water storage increment and compensation degree in different vegetations were dramatically different. Soil water compensation depth in the same vegetation in rainy years was over 60 cm more than that in dry years, while the soil water storage increment in 5 m soil layers increased over 3 times. Under natural precipitation, the soil water deficit in artificial vegetation on steep slope cannot be ameliorated, and the soil aridization also can't be relieved.