tailieunhanh - Báo cáo khoa học: "Measurement and modelling of the photosynthetically active radiation transmitted in a canopy of maritime pine P Hassika"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "Measurement and modelling of the photosynthetically active radiation transmitted in a canopy of maritime pine P Hassika. | Ann Sei For 1997 54 715-730 Elsevier Inra 715 Original article Measurement and modelling of the photosynthetically active radiation transmitted in a canopy of maritime pine p Hassika p Berbigier JM Bonnefond Laboratoìre de bioclimatologie Inra domaine de la Grande-Ferrade BP 81 33883 Villenave-d Ornon cedex France Received 20 May 1996 accepted 20 May 1997 Summary - Modelling the photosynthesis of a forest requires the evaluation of the quantity of photosynthetically active radiation PAR absorbed by the crowns and the understorey. In this article a semi-empirical model based on Beer s law is used to study PAR absorption and its seasonal variation. Our purpose was to confirm that the PAR and the solar radiation follow the same interception laws for both the direct and diffuse part using correct values of needle transmission and reflection coefficients. The model developed took into account the direct and the diffuse radiation. The radiation rescattered by the crowns was neglected following an estimation using the Kubelka-Munk equations which indicated that the term was small. The model was calibrated and tested from the measurements taken in a maritime pine forest during the summer and autumn of 1995. The comparison between the results of the model and the measurements was satisfactory for the direct radiation as well as for the diffuse radiation. In conclusion although the measurement wavebands are different the penetration of the PAR can be estimated using the same simple semi-empirical model already established for solar radiation. model solar radiation photosynthetically active radiation penetration maritime pine Resume Mesure et modélisation du rayonnement utile à la photosynthèse transmis dans un couvert de pin maritime. Pour la modélisation de la photosynthèse d un couvert vegetal il est important de connaĩtre la quantité de rayonnement utile à la photosynthèse PAR absorbé par les cou-ronnes et le sous-bois. Dans cet article un modèle semi-empirique exploitant

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