Abstract:

By using auto-data collection system with thermal dissipation sap flow probe, meteorological and soil sensors, diurnal and daily sap flow velocity (SFV) and whole tree water consumption of Pinus tabulaeformis and Platycladus orientalis were measured in late autumn from Oct. 27 to Nov. 9 in the West Mountains of Beijing. Results showed that diurnal SFV started from 8:00, and ascended to the peak during 13:00～15:00, then went down to the valley after 18:00. SFV of P. orientalis was much higher than that of P. tabulaeformis at the same lower position. Diurnal fluctuation of SFV on lower and upper trunk positions of P.tabulaeformis was similar, but the starting time of SFV on upper trunk position was much earlier, and the SFV peak was higher and thinner compared with lower trunk position. Progressive daily and diurnal sap flux on lower and upper trunk positions were approximately equal during measuring period. Daily water consumption (DWC) gradually descended in November. DWC of P. tabulaeformis in Nov. 6 was only 1/5 of 5 days ago, and DWC of P. orientalis was nearly 0 at the same time. Diurnal SFV was deeply affected by environmental factors such as solar radiation, air temperature, air humidity, wind speed and soil temperature. Multiple linear models of sap flow velocity and environmental factors were developed at significant level,of which the important factors were soil temperature in depths of 5 cm and 20 cm, solar radiation, air humidity and wind speed. Models of daily whole tree water consumption of P. tabulaeformis and P. orientalis were cubic curves.

Key words: Sap flow velocity, Sap flow Probe, Single tree water consumption, Pinus tabulaeformis, Platycladus orientalis