Changes in soil water content in the rhizosphere of Artemisia ordosica: Evidence for hydraulic lift

Hydraulic lift by Artemisia ordosica was investigated in a greenhouse study. The root system was grown in two soil compartments: a drier, upper soil and a wetter, deep soil. Diurnal soil water content (Øv) at 10, 25, and 35 cm in the top pots was measured at 4-h intervals with time domain reflectometry. There was an increase in Øv at all three depths from 22:00 to 05:00 h during the three experiment days. The average amplitudes of fluctuations at 10, 25, and 35 cm were 0.0108, 0.0159, and 0.0314 m3 m−3, respectively. Root distributions in the upper pots were also investigated. At 0–10 cm, weight density and volume of primary roots were significantly greater than the fine roots, but at 25–35 cm, weight density and volume of fine roots were significantly greater than primary roots. At 10–25 cm, weight density of primary roots was greater than that of fine roots. Changes in values of soil water content (0.01 m3 m−3) and root length density, weight density, and volume at 10, 25, and 35 cm in the upper pots indicated a clear linear relationship between the magnitude of hydraulic lift and length density of fine roots (r=0.999***).