Needs and opportunities for using a process-based productivity model as a practical tool in Eucalyptus plantations

This paper presents the application of a process-based model (PBM) to the management of 181,000 ha of Eucalyptus grandis plantations in Brazil owned by Aracruz Celulose (Arcel). The company recently adopted the process-based model 3-PG (Physiological Principles Predicting Growth) for use in research applications and as an analytical tool as part of its forest management systems. The model is being used to predict potential productivity in terms of forest volume in current production areas and on new lands, and to quantify the effects of environmental factors and management actions on forest productivity. This use allows quantification of the risks associated with production, and increases the quality of the decision-making process. The model was calibrated for an experimental catchment site, and when applied in other regions the goodness of fit between estimated and observed peak mean annual increment was high (r ²=0.93, P<0.05, S.E.=1.44 m³ ha^-1 per year). Current research is focused on questions of soil fertility ratings, the physiological characteristics and differences among various clones at several sites, and on the application of 3-PG using spatial data bases running in a geographic information system. The progress made in applying 3-PG reported here demonstrates the valuable role that process-based models can play as practical and applied tools in commercial forest management, especially in fast-growing Eucalyptus plantations with short-rotation times (5-7 years), and for testing hypotheses about the way trees function and respond to environmental changes.