Abstract:

Transpiration of 21-year-old Populus bolleana was measured by thermal dissipation sap flow velocity probe (TDP) and the meteorological data were automatically collected in a meteorological station in Maowusu sandy area from April to September in 2004. Relationships between transpiration variation and meteorological factors, soil water, water surface evaporation (EV₀) or leaf area index (LAI) were analyzed. The aim of the study was to provide essential scientific basis for the water management of shelter belts in the area. The results were exhibited as follows: total transpiration (ToTR) per tree was 5 300.96 L during the growth season (from April to September), and the maximum monthly transpiration occurred in June with 1 073.82 L, which accounted for 20.26% to ToTR,. The linear regression analysis showed that transpiration rate had a good correlation with the canopy solar radiation, air temperature, relative humidity and wind speed. Solar radiation was the dominant meteorological factor to affect the transpiration (α=0.01). Transpiration was found to lag solar radiation due to water capacity and light induction to stomatal aperture. Correlation analysis indicated that soil water variation had no significant effect on daily transpiration due to the high groundwater level of the experimental site. The relationship between daily transpiration and LAI×EV0 obeyed a power function significantly with the correlation coefficient of 0.83.

Key words: Maowusu sandy area, Populus bolleana, transpiration rate, TDP, meteorological factors, soil water