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Báo cáo lâm nghiệp: "Sapwood as the scaling parameter defining according to xylem water content"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Sapwood as the scaling parameter defining according to xylem water content. | Ann. Sci. For. 55 1998 509-521 Inra Elsevier Paris 509 Original article Sapwood as the scaling parameter -defining according to xylem water content or radial pattern of sap flow Jan Cermak Nadezhda Nadezhdina Institute of Forest Ecology Mendel s Agricultural and Forestry University 61300 Brno Zemedelska 3 Czech Republic Received 11 April 1997 accepted 23 April 1998 Abstract - Sapwood cross-sectional area is a simple biometric parameter widely used for scaling up the transpiration data between trees and forest stands. However it is not always clear how the sapwood can be estimated and considered which may cause scaling errors. We examined the sapwood depth according to xylem water content and more precisely according to radial patterns of sap flow rate in five coniferous and four broad-leaved species of different diameter age and site conditions. Sapwood estimated by the two methods was almost equal in some species e.g. Cupressus arizonica but differed significantly in other species e.g. Olea europaea Pinus pinea . Radial pattern of sap flow rate is a more reliable indicator of sapwood then xylem water content for sap flow scaling purposes. Percentage of sapwood along radius changed with tree diameter and age. Sapwood also changes substantially under severe drought e.g. in spruce Picea abies up to 1 3 in the course of several months . Sapwood should be used for upscaling sap flow data from measuring points to the whole trees and from trees to stands only for the period when it was actually measured or the radial profile of sap flow should be measured continuously to avoid possible scaling errors. Inra Elsevier Paris woody species sapwood radial pattern sap flow xylem water content scaling Resume - Le bois d aubier paramètre de changement d echelle deflni en relation avec le contenu en eau du xylème OU avec le type radial de flux de sève La surface de la section de bois d aubier est un paramètre biométrique largement utilise pour effectuer des changements d echelle .