Parameterisation of 3-PG model for fast-growing Eucalyptus grandis plantations

The 3-PG model [J.J. Landsberg, R.H. Waring, A generalised model of forest productivity using simplified concepts of radiation-use efficiency, carbon balance and partitioning, For. Ecol. Manage. 95 (1997) 209] was parameterised for Eucalyptus grandis hybrid plantations based on data collected in an experimental catchment. Model performance was compared with data collected monthly in 12 plots over 3.5 years from five genotypes in the catchment and in growth plots measured annually in two other regions. Application of the model using the parameter values determined in the study allowed us to describe accurately the growth patterns of stands in terms of mean annual increment, total stand volume, basal area, diameter at breast height, leaf area index and available soil water. The observed differences in production between genotypes (clones) could be attributed primarily to differences in biomass partitioning and secondarily to differences in stomatal conductance. There were differences between clones in parameters affecting the allometric relationship between stem mass and diameter at breast height, biomass allocation to roots, the ratio of foliage to stem allocation and maximum stomatal conductance. The model can be used to simulate growth and yield in areas for which it has not been calibrated, and parameters obtained in the calibration process described are being applied to estimate growth in 181 000 ha of E. grandis hybrid plantations in Brazil.