Abstract：This study was designed to analyze the seasonal variation characteristics of the sap flow of Quercus acutissima, based on the 12-month continuous located observation of the sap flow rate and environmental factors by using sap flow meter and mini weather station in Nanjing Dongshanqiao Forest from May 2012 to April 2013. The results indicated that: 1) the sap flow rate of Q. acutissima showed distinct diurnal change rhythms both in sunny and cloudy days in spring, summer and autumn. Sap flow rates in daytime were higher than those during the night, and sap flow rates in sunny days were higher than those in cloudy days. The fluctuation of the daily sap flow rates was relatively violent in winter. 2) The average peak of sap flow rate in spring was about 5.69kg/h; the average peaks of sap flow rate in summer, autumn and winter were 1.58, 1.08 and 0.012 times as high as that in spring. 3) The lag effect existed between the peaks of sap flow rate and the peaks of solar radiation, and the lag time was about 1-2h. The peaks of sap flow rate were about 1 hour ahead of those of air temperature, vapor pressure deficiency and soil temperature. 4) The correlation coefficients between environmental factors and sap flow rate and daily sap flow in spring, summer, autumn were higher than in winter. 5) The determination coefficients of multiple linear regression models in spring, summer and autumn were around 0.8, and the determination coefficient was lower in winter.
2013, Vol. 11 
