Measured sap flow and simulated transpiration from a poplar stand in Flanders (Belgium)

This study reports on the transpiration by a hybrid poplar (Populus trichocarpa x P. deltoides) plantation in East Flanders during 1997. Transpiration was measured by sap flow techniques on individual trees and scaled to the stand level, and was simulated by the WAVE water balance model. Relatively high transpiration values by the poplar stand were found during the growing season, with maximum and mean daily transpiration of 5 and 1.9 mm per day, respectively. The seasonal (1 April-31 October) total transpiration amounted to 320 mm, representing roughly 70% of the potential evapotranspiration over this period. However, this transpiration represented only about three-fourths of the incoming precipitation. Reasonable agreement was found between measured and simulated stand transpiration. The difference between cumulated precipitation and cumulated actual transpiration closely mimicked the course of the water table. Suggestions for further improvements to the WAVE model have been made and discussed. (C) 1999 Published by Elsevier Science B.V. All rights reserved.