Modeling the 3-PG fertility rating as a function of soil physical and chemical characteristics

Abstract

Process based models are useful scientific tools, but they have not been used frequently in forest management, as they require detailed input data with scarce results for management. The 3-PG (Physiological Principles in Predicting Growth) is a process-based model developed with the intention of bridging the gap between the empirical models and the more complex physiologically based models. Soil fertility is considered through a fertility index, the so-called FR (fertility rating), a value that varies between 0 and 1, empirically attributed according to the characteristics of the place. Although there is limited knowledge of the relationship that exists between FR and soil properties, some efforts have been made to develop functions relating FR and soil characteristics. The present study seeks to develop a general model to predict FR from soil characteristics and to test the possibility of making the 3-PG model sensitive to fertilization. Preliminary results resulted in models with good performance at the plot level, but the first attempt at a generalized model did not achieve good predictive capacity. Tests continue to take place to improve the predictive capacity of the different models.