tailieunhanh - Báo cáo lâm nghiệp: "A tree crown ratio prediction equation for eucalypt plantations"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: A tree crown ratio prediction equation for eucalypt plantations. | 193 Ann. For. Sci. 58 2001 193-202 INRA EDP Sciences 2001 Original article A tree crown ratio prediction equation for eucalypt plantations Paula Soares and Margarida Tomé Department of Forestry Tapada da Ajuda 1349 017 Lisboa Portugal Received 3 January 2000 accepted 5 October 2000 Abstract - Based on a data set from spacing trials and permanent plots of Eucalyptus globulus Labill. several nonlinear equations for crown ratio prediction based on exponential logistic Richards and Weibull functions were tested. The total data set was used to fit and select the equations. The equations were evaluated in terms of measures of fit and prediction ability adjusted-R1 2 residual mean square sum of PRESS residuals and sum of absolute PRESS residuals. The normality of the studentized residuals was analyzed using normal QQ plots. The presence of heteroscedasticity associated with the error term was checked by plotting the studentized residuals against the predicted values. The significance of the estimated parameters was verified. Model error was characterized in terms of bias and precision. The Richards function was selected. This equation is age and density dependent reflecting the importance of intertree competition an initial tree dimension and a measure of stand productivity were also required as explanatory variables. crown ratio tree model plantations Eucalyptus globulus Labill. Résumé - Equation de prediction du rapport entre longueur du houppier et hauteur totale de l arbre pour des plantations d eucalyptus. A partir d un ensemble de données d essais d espacement et de parcelles permanentes d Eucalyptus globulus Labill différentes équations de prediction du rapport entre longueur du houppier et hauteur totale de l arbre basées sur les fonctions expo-nentielle logistique Richards et Weibull sont testées. Les données sont utilisées pour l estimation et la sélection des équations de prediction. L évaluation des équations est basée sur des mesures d ajustement et de .