Abstract: Field measurements of transpiration rate (T_r), leaf area index (LAI), and related environmental factors were conducted for two typical woody plant communities (Eucalyptus grandis × E. urophylla and Pinus massoniana) in the watershed of the Gongjing Reservoir in Guangxi, China. Results showed that the seasonal change of T_r of Pinus massoniana was 0.14-0.69 μmol·m^-2·s^-1, and that of <2year-old and >4year-old Eucalyptus was 1.65-3.76 μmol·m^-2·s^-1 and 1.05-2.04 μmol·m-2·s-1, respectively. The Tr of <2yearold and >4yearold Eucalyptus was 6 times and 3.4 times that of P. massoniana, respectively. The T_r was highest in summer and lowest in winter for all plants, and T_r in summer was nearly twice as high as in winter. Significant positive correlations were found between T_r and LAI, soil water content and air temperature (P<0.01); all factors influencing transpiration were not independent. Path analysis results showed that air temperature and soil water content were the key variables for transpiration in P. massoniana. LAI had the greatest effect on transpiration of younger Eucalyptus, while soil water content was the key variable for older Eucalyptus.

Key words: coastal wetland, soil dissolved organic matter, spatial distribution, three dimensional fluorescent characteristics