Calibration of heat ratio method by direct measurements of transpiration with weighing root-ball method : A study with Acer palmatum Thunb

The weighing root-ball method to calibrate sap flow measurements was developed. This method detects the amount of transpiration as the changes in the weight of tree body and compared with heat ratio method applied on Acer palmatum Thunb. for two years. There is a high correlation between transpiration rate and the heat pulse velocity by HR method. In low velocity, linear regression was obtained, while in high velocity, a quadratic regression was obtained. Estimated sap flow rate increased in two years. The weighing root-ball method is suitable for calibration of sap flow techniques, in cases that nondestructive procedures are required.