Generic and specific volumetric equations for individual trees in the Tapajos National Forest, Eastern Amazon

Abstract

The objective of this study was to evaluate the use of volumetric models, through the application of identity tests, in seven Annual Production Units (APUs) of the Tapajos National Forest (TNF), as well as to verify the precision of equations adjusted by APU volume data from the previous year for use in the following year. A total sample size of 2 100 stems were used for the adjustment of six models, and then the selected model was adjusted for the APU stratified data. The identity test, which compares adjusted equations using different datasets to verify whether or not a single equation could be used for all cases, was used to compare equations on various combinations of APUs, and a t-test was employed for validation of equations adjusted by APU data from the previous year. The identity test was significant for most comparisons, including the combinations of all the APUs, indicating that the use of one generic equation is not recommended for the entire management area. The t-test showed that there was a difference, for the majority of cases, between the observed and estimated volumes using the equation adjusted for the previous APU data. Therefore, the use of one general equation as well as equations adjusted based on data from APUs managed in the previous year is not recommended for volume estimation in TNF.