Stand-level yield model for Scots pine (Pinus sylvestris L.) in north-east Spain

Abstract

Simultaneous stand-level growth and yield models for Pinus sylvestris in north-east Spain were developed based on 21 permanent sample plots established in 1964 by the Instituto Nacional de Investigaciones Agrarias (INIA). The plots ranged in site index from 13 to 26 m (dominant height at 100 years), and were measured an average of 5 times. The estimation data consisted of 79 growth periods of stands ranging in age from 36 to 132 years. Non-linear three-stage least squares method was used to simultaneously fit prediction and projection equations for stand basal area, volume and stand density. An existing model for dominant height growth fitted with the same estimation data was used to project dominant height. The models were evaluated both quantitatively and qualitatively. Correlation among error components of the prediction equations for basal area and volume as well as the projection equations for number of trees per hectare and volume were strong and significant. The mean biases for basal area, volume and number of trees per hectare predictions were positive. The presented system of models can serve for forest-level management planning as a simple yield prediction system that requires only stand level input data.