Evaluation of transpiration in a Douglas-fir stand by means of sap flow measurements

Transpiration of a Douglas-fir (Pseudorsuga menziesii (Mirb.) France) stand was evaluated by sap flow measurements during a 4-month period. Between-tree variation in sap flow depended on crown class. On a sunny day, total transpiration was 1.6, 8.0 and 22.0 liters day- ’ for suppressed, codomi-nant and dominant trees, respectively. Transpiration estimated by sap How fell below potential evapotranspiration when available soil water decreased below 30 % of its maximum value. Sap How measurements gave transpiration values similar to those obtained by the water balance method