RT info:eu-repo/semantics/article T1 Additivity on nonlinear stem taper functions: A case for Corsican pine in northern Spain A1 Rodríguez Puerta, Francisco A1 Lizarralde Torre, Íñigo A1 Bravo Oviedo, Felipe K1 Bosques y silvicultura - España K1 Pinos - España K1 Pinos - Crecimiento K1 Bosques - Gestión - España K1 3106 Ciencia Forestal AB A system of additive equations was developed to predict whole-tree volume and the differentcomponents of Corsican pine. In this work, the nonlinear seemingly unrelated regression (NSUR) approach, which guarantees additivity in nonlinear equations, was evaluated. The effect of bark thickness on the accuracy of the results for all tree components was also assessed. Data for 351 trees, ranging in age from 10 to 72 years, were collected from 65 public and private sites. The volume estimates show average biases that range in absolute values from 2.19 to 31.02 dm3 for whole-tree, from 1.41 to 27.31 dm3 for wood, and from 1.05 to 16.52 dm3 for bark volume components. Errors in volume predictions were relatively small, representing less than 3% of the average observed wood volume and less than 6% of the average observed bark volume. This research showed that satisfactory predictions can be obtained from forcing additivity using NSUR approach with a minimal number of easily measurable tree variables, such as dbh and total height. FOR. SCI. 59(4):464–471. PB Society of American Foresters SN 0015-749X YR 2013 FD 2013 LK https://uvadoc.uva.es/handle/10324/50524 UL https://uvadoc.uva.es/handle/10324/50524 LA eng NO Forest Science, 2013, vol. 59, n. 4, p. 464-471 NO Producción Científica DS UVaDOC RD 27-abr-2024