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Báo cáo lâm nghiệp: "Modelling canopy conductance and stand transpiration of an oak forest from sap flow measurements "

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế, đề tài: "Modelling canopy conductance and stand transpiration of an oak forest from sap flow measurements . | Ann Sci For 1996 53 537-546 Elsevier INRA 537 Original article Modelling canopy conductance and stand transpiration of an oak forest from sap flow measurements A Granier N Bréda Équipe bioclimatologie et écophysiologie unite d ecophysiologie forestiere Centre de Nancy tnra 54280 Champenoux France Received 13 January 1994 accepted 31 October 1995 Summary In this study transpiration was estimated from half-hourly sap flow measurements in a 35-year-old sessile oak stand Quercus petraea from 1990 until 1993 under various soil water conditions. The canopy conductance calculated from the Penman-Monteith equation was first analysed in relation to climatic variables global radiation Rg and vapour pressure deficit VPD . The maximum canopy conductance gcmax was modelled with a nonlinear multiple regression over a period of nonlimiting soil water content and of maximal leaf area index LAI with a fi - 0.80. Limitations of gc due to soil water deficit relative extractable water REW and canopy development LAI were then taken into account in the model by using multiplicative limiting functions of REW and LAI. A general canopy conductance model was then proposed. Finally this relationship was re-introduced in the Pen-man-Monteith equation to predict dry canopy transpiration. Simulated transpiration was in good agreement with sap flow measurements during the year following the calibration fi 0.92 in the control plot 0.86 in the dry plot . The omega decoupling coefficient was close to 0.1 on a seasonal basis indicating that transpiration was highly dependent on VPD. canopy conductance I transpiration sap flow I oak stand model Resume Modélisation de la conductance du couvert et de la transpiration du peuplement d une foret de chênes à partir de mesures de flux de sève. Dans ce travail la transpiration a été estimée à partir de mesures semi-horaires de flux de sève dans un peuplement de chênes sessiles Quercus petraea âgé de 35 ans entre 1990 et 1993. Differentes conditions hydríques