tailieunhanh - Báo cáo khoa học: Evaluation of heat balance and heat dissipation methods for sapflow measurements in pine and spruce

Abstract – The tissue heat-balance method (Cÿermák) and the heat-dissipation method (Granier) were compared in three Scots pines and two Norway spruces in a forest in central Sweden. The Granier system measured up to 50% lower sapflow than the Cÿermák system at high flow rates. | Ann. For. Sci. 58 2001 625-638 INRA EDP Sciences 2001 625 Original article Evaluation of heat balance and heat dissipation methods for sapflow measurements in pine and spruce Mattias Lundblada Fredrik Lagergrena and Anders Lindrothb aDept for Production Ecology Swedish University of Agricultural Sciences Box 7042 SE-750 07 Uppsala Sweden bDepartment of Physical Geography Lund University Box 118 SE-221 00 Lund Sweden Received 21 December 2000 accepted 11 April 2001 Abstract - The tissue heat-balance method Cermák and the heat-dissipation method Granier were compared in three Scots pines and two Norway spruces in a forest in central Sweden. The Granier system measured up to 50 lower sapflow than the Cermák system at high flow rates. New coefficients for the Granier system were estimated based on sapflow density from the Cermák measurements. Without compensation natural temperature gradients may cause large errors in measurements made by the Granier system. By using a horizontal reference sensor no compensation was necessary. It was also shown that radial flow patterns must be considered when calculating total tree sapflow. Transpiration of two adjacent stands one measured by the Granier method and the other by the Cermák method showed good agreement internally and with total evaporation measured by the eddy-correlation method. THB HD sap-flow transpiration Picea abies Pinus sylvestris Résumé - Evaluation des méthodes des équilibres thermiques et de dissipation thermique concernant la mesure de flux de sève pour le pin et l épicéa. La méthode des équilibres thermiques Cermák et la méthode de dissipation thermique Granier ont été com-parées pour trois Pins sylvestres et deux épicéas dans une forêt du centre de la Suède. Le système Granier a donné des valeurs de flux de sèvejusqu a 50 plus faible que le système Cermák pour les flux élevés. De nouveaux coefficients basés sur les mesures de densité de flux obtenues avec le système Cermák ont été estimés pour le système .