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Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Diurnal evolution of water flow and potential in an individual spruce: experimental and theoretical study. | 353s Ann. Sci. For. 1989 46 suppl. 353-356 Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Diurnal evolution of water flow and potential in an individual spruce experimental and theoretical study p. Cruiziat1 A. Granier2 J.p. Claustres1 and D. Lachaize1 1 Laboratoire de Bioclimatologie INRA Domaine-de-Crouelle F-63039 Clermont-Ferrand and 2 CRF de Nancy INRA Station de Sylviculture BP 35 F-54280 Seichamps France Introduction We present a model built primarily to study the water flow in a single tree within a forest. After comparing it with other available systems we develop the characteristics of our model and its usefulness. Assumptions 1 Sap moves from points of high potential to points of low potential. 2. Flow within the different parts of the system obeys the Darcy equation 3. Roots are not supposed to have a capacitance optional 4 All parameters are lumped together. 5. Neither branch twig architecture nor growth are considered optional . Materials and Methods Outline of the model The structure of the model Fig. 1 comes from our idea of how the spruce we work with is compartmented 7 compartments were distinguished leaves 1 uppercrown 2 lower crown 2 trunk 2 . Except for leaves 2 kinds of water reservoirs constitute each of the 3 preceding levels Jarvis 1975 Granier 1987 Gra-nier and Claustres 1989 a small one corresponding to the elastic tissues with a small constant of time and a larger one representing the sapwood with a large time constant. Twelve resistances must be specified. Although SPICE the circuit simulation program we used allows us to introduce variable capacitances and resistances Cruiziat and Thomas 1988 we did not think they were necessary at this stage of our experimental knowledge. Values of the parameters and input variables The data consist of hourly measurements of sap flow bottpm of the trunk leaf water potential at 2 levels and transpiration rate per tree calculated by the Penman-Monteith equation for the stand . In addition .
