Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: Choosing simplified mixed models for simulations when data have a complex hierarchical organization. An example with some basic properties in Sessile oak wood (Quercus petraea Liebl.). | Ann. For. Sci. 59 2002 847-855 INRA EDP Sciences 2002 DOI forest 2002083 847 Original article Choosing simplified mixed models for simulations when data have a complex hierarchical organization. An example with some basic properties in Sessile oak wood Quercus petraea Liebl. Gilles Le Moguédec Jean-Franẹois Dhôte and Gérard Nepveu LERFOB Centre INRA de Nancy 54280 Champenoux Cedex France Received 14 February 2001 accepted 6 August 2002 Abstract - This paper focuses on the modeling of the variability of some properties in Sessile oak wood five swelling coefficients and wood density . They are modeled with linear mixed models. The data have a seven-levels hierarchical organization. The variability at each level is modeled with a variance matrix. Unfortunately a model with all variances has too many parameters to be usable so preferably only one variance other than the residual is kept. A graphical procedure based on the comparison of residual variance in the different candidate models is used to detect this main level. Result shows that the main level of variability is the tree level or the height within tree level for five properties. We cannot conclude for the last property. For other properties the residual variance in the model with a tree effect is reduced to 40 of the residual variance of the model without structuring of variability. If the applications of models deal with the variability of properties this tree level cannot be neglected. linear mixed model Sessile oak structuring of variability tree effect Résumé - Simplifier un modèle mixte destiné à effectuer des simulations lorsque les données ont une structure hiérarchique complexe. Exemple de quelques propriétés de base du bois de Chêne sessile Quercuspetraea Liebl. . Cet article traite de la modélisation de la variabi-lité de propriétés du bois de Chêne sessile cinq coefficients de gonflement et la densité du bois . Ces propriétés sont modélisées à l aide de mo-dèles linéaires mixtes. Les données
