Abstract:

During the period of September 12, 1999 to September 24, 2000, we measured sap flow of eucalyptus (Eucalyptus urophylla S.T. Blake) plantations using heat pulse technique, and the relevant environmental vaiables, such as soil evaporation and canopy interception, etc, at Hetou and Jijia sites, Leizhou Peninsula, Guangdong Province. Based on the measurements of sap flow and estimates of evapotranspiration, the following can be concluded: (1) the maximum of diurnal xylem sap flux density (SFD) at Hetou, where covered with coarse-textured soils formed on Quaternary sediments, was almost twice of that at Jijia, where located on clay-rich soils derived from basalt; (2) SFD was highly correlated to water vapor pressure deficit (VPD) of ambient air near the canopy layer; (3) the correlation between SFD and air temperature also depends on soil properties and soil water potential; (4) the relative differences between measured and modeled evapotranspiration were small, being 5.26% at Hetou and 6.14% at Jijia; (5) the plantation transpiration accounted for 62.2% and 51.3% of the evapotranspiration at Hetou and Jijia, respectively; and (6) the averaged SFD per unit leaf area (ASPULA) was a good index to estimate the amount of water consumption of tree species.

Key words: Eucalyptus urophylla plantation, water consumption, sap flux density (SFD), vapor pressure deficit (VPD), transpiration, evapotranspiration