Abstract:

Sap flow density (SFD) of 6 tress of Pinus elliottii in a plantation was continuously measured with Granier's thermal dissipation probe. In the meantime, several meteorological and soil factors were monitored and measured. In early growth stage, the whole xylem could be taken as sapwood. A significant correlation between sapwood area (SWA) and diameter at breast height (DBH) was found and was well fitted with quadratic model. SFD was well correlated with DBH (r²>0.99). Patterns of diurnal variation of the sap flow in sunny days were similar during rapid growth season, except that there was difference in the timing of initiating and reaching peaks as well as the intervals of ascending and descending. The daily average SFD tended to decline with time and it was highest in June, followed by July and then by August. SFD was linearly correlated with canopy temperature (CT), canopy relative humidity (CRH) and photosynthetically active radiation (PAR) in the stand. The strength of correlation with SFD was as follows: CRH＞PAR＞CT. Multivariant linear model between SFD and the integrated three factors was also established. All equations and correlation parameters were significant at the level of 001.

Key words: Pinus elliottii, thermal dissipation probe (TDP), sap flow, affecting factors