Experimental study on effects of vegetation on water transport and storage in soil cover

Vegetation plays an important role in water storage and release of soil cover and in impermeable capability of soil. A large-scale loess soil cover (30 m×20 m) is built in field. The vegetation is planted in different areas and rainfall tests are carried out. The maximum water storage capacity is measured. The water transport, saturated permeability coefficient, effects of vegetation on water transport and storage capacity are analyzed and compared. The results show that: (1) The theoretical value of available water storage with vegetation is 278.32 mm, the measured one is 259.82 mm, and the latter is 18.5 mm (6.65%) smaller than the former. (2) The vegetation increases the saturated permeability coefficient of root growth area. It is 8.267×10^-5 cm/s without vegetation, and is more than 8.267×10^-5 cm/s with vegetation. Without vegetation, water is stored in shallow soil layer firstly and gradually infiltrates into deep soil, but it is stored in the whole section of soil with vegetation. (3) The fibrous root and initial vegetation have some influences on water storage capacity of soil cover. The available water storage measured in the tests is 259.82 mm with vegetation and 251.95 mm without vegetation. The former is only 7.87 mm (3.12%) larger than the latter. The total water storage measured in the tests is 381.90 mm with vegetation and 374.03 mm without vegetation. The former is only 7.87 mm (2.10%) larger than the latter. The water storage capacity of soil cover with or without vegetation is similar. It may be that, on one hand, the vegetation with fibrous root system is shallow (0~50 cm), on the other hand, the short growth period of vegetation has no significant effects on soil structure.