ABSTRACT The objective of this study was to analyze the performance of species-specific equations (SSEs) concerning generic ones in Annual Production Units (GEAPUs) and in a Forest Management Area (GEFMA) in the Brazilian Amazon. A total of 29,119 trees from 43 species were inventoried, harvested, and volumetric measurements were taken in ten APUs, with 10% of this total being separated for validation and comparison of the selected equations. After selection and validation of the equations (GEFMA, GEAPUs and SSEs) they were compared using precision statistics, by contrasting estimated and observed volumes and by residual analysis. Precision statistics were clearly lower for the SSEs. Trend lines near the average observed volume were shown for the SSEs when the estimates were contrasted with the observations. The residuals generated by the SSEs were smaller and statistically different than those of GEFMA and GEAPUs for the majority of cases. The most important commercial species (M. huberi) had its volume overestimated by 10.6, 9.3 and 3.0% when the GEFMA, the GEAPUs, and the SSEs were applied, respectively. Among the species that generally had very large trees, H. petraeum had its volume underestimated by 15.7, 16.6 and 4.4% by the GEFMA, GEAPUs and SSEs, respectively. The greater precision of the SSEs is reflected in better forest management planning decisions with respect to operational and economic aspects. These results show that besides being statistically valid, the SSEs are recommended for obtaining more precise estimates of commercial volume, especially since there is a great demand for reliable estimates for each individual species in forest management areas in the Amazon.

ABSTRACT Stem conicity and the sawing pattern, besides the presence of hollows and sapwood, are among the principal factors that are responsible for the low yield of lumber from harvested wood in the Amazon. Therefore, the objective of this study was to analyze of logs and stem conicity, and its effect on yield of sawn wood from the species Handroanthus impetiginosus (Mart. ex DC.) Mattos, Lecythis lurida (Miers) S. A. Mori, Manilkara huberi (Ducke) Chevalier, Astronium lecointei Ducke and Couratari sp., which are currently the most important commercial species in the study area. The data used were obtained from six production units in the Tapajós National Forest, Pará. The variables analyzed were conicity (obtained as a function of the difference between diameters at the base and top) between logs, DBH classes (diameter at breast height) and species, as well as yield (estimated using the Software MaxiTora) between logs and species. The majority of the species showed differences in conicity between logs, with the first log being the most conic, which was directly reflected by the lower yield for this log. There was a tendency of increase in conicity in the larger DBH classes, and differences in conicity and yield between species. The estimated yields were superior to the percent yields observed for Amazonian species in studies done using samples with similar characteristics. Therefore, it was concluded that conicity can vary between species, logs, and DBH classes, and is a characteristic that directly effects the yield of lumber. Furthermore, the incorporation of cutting templates represents an alternative for maximizing lumber yield.