Nutrients export in Pinus taeda L. plantations based on estimated volume by using the SisPinus system.

Abstract

Pinus plantations in Brazil occur preferably in regions characterized as low cost lands, located over low fertility soils and, as a consequence, small wood productions. This condition, associated with the fact that fertilizing the plantation is not a routine practice, plus the effect of nutrients export during the thinning and the final harvest be considerable, leads to yield losses in the next plantations. In this context, this work was carried out to evaluate the applicability of mathematical models developed for forest plantations, as described by Moro (2005) to the Sispinus, in order to estimate the nutrients exported by the wood extraction. Commercial plantations of P. taeda at the ages of 8, 12, 18, e 23 years were studied, all of them located in the region of Guarapuava (PR). The amount of nutrients both in wood as in the bark was determined in several disks taken at different positions of the trunk, one meter apart, since the basis up to the limit of the commercial height of the trunk. The mathematic equations developed by Moro (2005) were inserted into the biomass estimator Sispinus, allowing the estimates of the nutrients export. The adjustment of the equations, for the studied populations considering the different ages, site quality, management practices, among others, was extremely high, indicating a high level of confidence for the nutrient export estimate expressions.