Calibration of the heat ratio method by direct measurements of transpiration with the weighing root-ball method for Michelia figo
We have developed the weighing root-ball method to calibrate sap flow measurements. This method directly measures the amount of transpiration as the changes in the weight of the root-ball. In this paper, the suitability of a large root-ball of Michelia figo was investigated by observing the changes in sap flow and transpiration rate during and after transplantation and root pruning. The heat pulse velocity decreased by 33% compared to the previous value in response to root cutting and transplanting. However, there were no large differences in the annual maximum value of heat pulse velocity for three years. Three years after transplantation, the same tree was transplanted again with a large root-ball and the transpiration rate measured by weighing was almost equal to that of the first large root-ball. Furthermore, after downsizing the root-ball, the transpiration rate decreased by 45%. Especially, the inner heat pulse velocity clearly decreased after root cutting. The sap flux profile in the trunk may have changed in response to the reduction in root volume and the cutting of major roots. We found the clear relationship between actual transpiration rate and heat pulse velocity. Thus, the weighing root-ball method is suitable to calibrate the heat ratio method.
Takeuchi, S., Shinozaki, K., Matsushima, D. and Iida, S. (2020). Calibration of the heat ratio method by direct measurements of transpiration with the weighing root-ball method for Michelia figo. Acta Hortic. 1300, 21-28
calibration, weighing root-ball method, tree transplantation, downsizing root system, heat pulse velocity