Site index curves and growth model for Mediterranean maritime pine (Pinus pinaster Ait.) in Spain

A stand growth model for Mediterranean maritime pine in the Iberian Peninsula (Pinus pinaster Ait.) is presented. The model consist of a site index submodel developed from 281 stem analysis and validated with the data from 92 permanent sample plots. Three height growth equations in difference form are tested and the Bailey and Clutter (1974) function is considered appropriate due to its good performance with both fitting and validation data. A compatible growth and yield submodel is then elaborated with the data from the Forest Research Centre (CIFOR-INIA) permanent sample plots network. The future state of the stand is determined by the current state, characterized by basal area, age and density. The model is completed with a control function that predicts the diameter after thinning and a mortality rate for non-thinned intervals. The global model was validated with data of 13 independent permanent thinning plots from two experimental sites. The simulation of the long-term projection of volume, basal area and DBH after thinning shows certain overestimation in diameter after thinning and in volume. However, the results show errors lower than 5% and little bias.