Parameterisation of 3-PG for plantation grown Eucalyptus globulus

A set of parameter values for the forest growth model 3-PG was determined. These pen-nit the modelling of the time-course of growth and development of even-aged, intensively-managed, fertilised stands of Eucalyptus globulus. The parameters were determined by fitting output from 3-PG to observed stem biomass data (i.e. total above-ground woody biomass) and canopy leaf area index (LAI). To fit these data, it was necessary to modify 3-PG by making specific leaf area and the fraction of stem biomass in branch and bark explicitly age-dependent, and to include effects of temperature on canopy quantum efficiency. With these parameter values, 3-PG gave a good description of growth at seven of nine disparate sites in Tasmania and Western Australia. A partial explanation for its failure at one site in Western Australia is that this site was subject to a prolonged drought not reflected in the long-term mean climatic data used in this study. At the other, a high altitude site in Tasmania, 3-PG predicted significant growth although extensive frost damage had prevented establishment of a viable canopy. The model was also applied to non-fertilised stands in northern Tasmania for which only basic growth and site data were available. 3-PG adequately predicted the observed peak MAI of the better sites, but over-estimated peak MAI at poor or high-altitude sites. The following conclusions are drawn: 3-PG can provide a good simulation of future growth of intensively-managed, fertilised stands of E. globulus if the model is initialised with observed biomass data at some age around or following canopy closure. If the model is initialised with typical seedling biomass at planting, 3-PG adequately predicts stem growth rate but not canopy LAI. Further development of 3-PG should take into account possible environmental effects on litterfall, the effects of partial canopy closure during early canopy development, and the prediction of mortality prior to the onset of self-thinning. (C) 2002 Elsevier Science B.V. All rights reserved.