Abstract:

Soil water content is crucial to vegetation rehabilitation on the hilly loess plateau. Dynamics of soil water under three types of water and soil conservation forests was monitored in this study with an EnviroSMART monitoring system. Soil water content was recorded at 20 cm intervals over a 0～150 cm soil profile every 30 minutes during the whole growing period. Results showed that the soil profile in the secondary forest had similar soil water storage to that in Pinus tabulaeformis plantation on terrace, and the storage in both forests was 1.4 times of that in Robinia pseudoacacia plantation. Secondary forests mainly used precipitation and soil water in upper layer, while plantation consumed water from deep layer.of the soil. Soil water content in the secondary forest increased from top to lower layer; in contrast, it decreased downward along the soil profile in P. tabulaeformis plantation. For the three types of forests, variation coefficients of soil water content decreased downward over the soil profile and soil water storage reached to the lowest level in August. Relatively, water storage in deeper layer delayed to deplete. Soil water in the 90～150 cm soil layer decreased from May to October in all tested forests. During the whole growing season, R. pseudoacacia plantation consumed 249.73 mm of soil water from the 0～150 cm layer with the largest daily consumption 4.70 mm, P. tabulaeformis plantation consumed 248.09 mm with the largest daily consumption 4.77 mm, and secondary forest consumed 129.40 mm with the largest daily consumption 2.28 mm. Results demonstrated that plantation consumes significantly more water than secondary forest; therefore, soil and water conservation forests should be established by imitating secondary forests.

Key words: secondary forest, plantation, soil water content, water consumption, the Loess Plateau