tailieunhanh - Báo cáo khoa học: "Measurement and transmission within modelling a of radiation stand of maritime pine"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài:"Measurement and transmission within modelling a of radiation stand of maritime pine. | Ann Sci For 1995 52 23-42 Elsevier INRA 23 Original article Measurement and modelling of radiation transmission within a stand of maritime pine Pinus pinaster Ait p Berbigier JM Bonnefond INRA Laboratoire de Bioclimatologie Domaine de la Grande-Ferrade BP 81 33883 Villenave-d Ornon cedex France Received 18 October 1993 accepted 13 June 1994 Summary A semi-empirical model of radiation penetration in a maritime pine canopy was developed so that mean solar and net radiation absorption by crowns and understorey could be estimated from above-canopy measurements only. Beam radiation Rb was assumed to penetrate the canopy according to Beer s law with an extinction coefficient of this figure was found using non-linear regression techniques. For diffuse sky radiation Beer s law was integrated over the sky vault assuming a soc standard overcast sky luminance model the upward and downward scattered radiative fluxes were obtained using the Kubelka-Munk equations and measurements of needle transmittance and reflectance. The penetration of net radiation within the canopy was also modelled. The model predicts the measured albedo of the stand very well. The estimation of solar radiation transmitted by the canopy was also satisfactory with the maximum difference between this and the mean output of mobile sensors at ground level being only 18 w ITT2. Due to the poor precision of net radiometers the net radiation model could not be tested critically. However as the modelled longwave radiation balance under the canopy is always between -10 and -20 WtTT2 the below-canopy net radiation must be very close to the solar radiation balance. model solar radiation net radiation penetration maritime pine Resume Mesure et modélisation de la transmission du rayonnement à rintérieur d une parcels de pins maritimes Pinus pinaster Ait . Un modèle semi-empirique de penetration du rayon-nement dans un convert de pins maritimes a été établi dans le but d estimer absorption moyenne du rayonnement .

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