2016 年 26 巻 3 号 p. 95-99
Juniperus sabina L. is an evergreen shrub with prostrate life form that may effectively stabilize sand dunes and moving sand. Therefore, it serves as an important woody species for revegetation in semiarid areas of China. The main root system of J. sabina can reach deep into soil while adventitious roots mostly extend into surface soil. To evaluate water movement between different soil-layers these root systems that is associated with rainfall-induced vertical heterogeneity in soil moisture, we measured changes in sap flow and soil moisture content as well as atmospheric temperature and humidity. The patch radius of twenty-four patches was also measured for 7 years to monitor changes in growth rate. Nighttime sap flow between the main root system and adventitious roots during periods of no rainfall was measured; nighttime sap flow decreased or disappeared after rainfall. The annual growth rate of the patch radius was significantly correlated with the annual deposition rate of sand and the amount of annual precipitation. It was suggested that water movement occurs from the deeper moist soil layer to dry surface soil layer via the main root system and adventitious roots by hydraulic redistribution (HR). This movement increased with the progression of drought in the surface soil layer after a rain event. J. sabina can effectively use both subsoil water during periods of drought and rainwater in surface soil layer after an occasional rain event through the HR. This allows the plant to survive and continuously grow under water-limited conditions and in a mobile sand environment in semiarid areas.