Long-term trends in dominant-height growth of black pine using dynamic models

Black pine (Pinus nigra Arn.) is a pan-Mediterranean species of high ecological importance and one of the most important timber species in the area. We compare several site dependent height-age models for the species in three regions along its natural distribution area in Spain. The best model was a generalized algebraic difference approach (GADA) polymorphic model with variable asymptotes (Cieszewski, CJ., Bailey, R.L., 2000. Generalized algebraic difference approach: theory based derivation of dynamic site equations with polymorphism and variable asymptotes. For. Sci. 46, 116-126). There was no significant increase in error when a reduced model common to the three regions was tested instead of a full model with region-specific parameters. To study possible biases of the proposed model along the trees' lifespan we carried out a LOWESS analysis of residuals in time. We detected deviations in the model residuals. and a patent growth reduction in the 1960s and 1970s, which might be related to climate and/or changing stand characteristics. Departures from estimated mean past growth should be monitored in the future to adapt models to a changing environment. (C) 2008 Elsevier B.V. All rights reserved.