Modelling commercial biomass of native yerba mate in the South-Center region of Paraná

Abstract

The cultivation of the yerba mate species is of great importance, as in addition to helping to preserve forest remnants, it is also a source of income for rural producers. However, incorrect management can result in low productivity in yerba mate cultivation. Therefore, it is of great importance to evaluate the production of this species, using appropriate techniques. Thus, the present study aimed to evaluate the commercial biomass (BC) of a native yerba mate cultivation system, as well as adjust equations to estimate commercial biomass individually and per hectare for yerba mate in similar conditions. The study area is located on a private property in the municipality of Inácio Martins, where permanent sampling units were installed with a total area of 1.25 ha, in which data were collected from all yerba mate individuals that were pruned to obtain commercial biomass, and some dendometric variables were then measured. Based on the collected variables, commercial biomass estimates were made by applying the Stepwise Forward procedure. In addition to individual BC estimates for yerba mate, equations were also adjusted for estimates per unit area (ha). To evaluate the fit of the equations, the following criteria were used: the adjusted Coefficient of Determination (R²aj), the Standard Error of the Estimate in percentage (Syx%) and the graphical distribution of the residuals. The Stepwise procedure adjusted the best equations, with values for the coefficient of determination above 0.8 for individual estimates and above 0.9 for estimates per hectare and errors between 20 and 30% for both situations. Estimates of commercial yerba mate biomass using a single, easily obtainable variable showed errors of around 40% and heterogeneity in the graphic dispersion of residues. The use of the Stpewise tool can enable a better economic assessment of yerba mate managed areas.