3-PG fertility modifier as a function of soil nutrient content

Abstract

The 3-PG is a physiologically based model that has been extensively used and tested to predict the primary productivity of forest stands around the world. Soil fertility is considered by means of a fertility index, so-called fertility rating, a value that varies between 0 and 1. This fertility parameter has been inserted by the model user based on his intuition or experience. Attempts to develop a mathematical model to obtain the fertility rating value from soil characteristics have had contradictory results. The present study seeks to propose a fertility modifier (fN) for 3-PG, considering the limiting values of nutrients in soil in Eucalyptus globulus follow-up trials. Preliminary results seem to indicate a good relationship between the wood volume of the studied stands and the carbon and boron contents of the soil in the different plots. Before proposing a generalizable modifier for Portugal, it will be necessary to expand the number of settlements, as well as their regional distribution.