CONICET | Buscador de Institutos y Recursos Humanos

Tree growth is one of the main variables needed for forest management planning. The use of simple models using traditional equations to describe tree growth is common. However, equations that incorporate different factors (e.g., site quality of the stands, crown classes of the trees, silvicultural treatments) may improve the accuracy of them in a wide range of stand conditions. The aim of this work was to compare the accuracy of tree diameter growth models using (i) a family of simple equations adjusted by stand site quality and crown class of trees, and (ii) a unique global equation including stand and individual tree variables. Samplings were conducted in 136 natural even-aged Nothofagus antarctica (Forster f.) Oersted stands in Southern Patagonia (Argentina) covering age (20 to 200 years), crown class and site quality gradients. The following diameter growth models were fitted: 16 simple equations using two independent variable (age and one equation for each stand site quality or crown class) based on Richards model, plus a unique global equation using three independent variables (age, stand site quality and crown class). Simple equations showed greater variability in their accuracy, explained between 54% and 92% of the data variation. The global model presented similar accuracy to the better equations of the simple growth models. The unification of the simple growth models into a unique global equation did not greatly improve the accuracy of estimations, but positively influence over the biological response of the model. Another advantage of the global equation is the simplicity use under a wide natural stand conditions. The proposed global model allows to the explanation of tree growth of N. antarctica trees along the natural studied gradients.

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