Abstract
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 Tapajos National Forest, Para. 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.
Highlights
The extraction of timber from native forests has become one of the principal economic activities in all the States that make up the Legal Amazon at the beginning of the XXI century (Homma, 2011)
This region is a large generator of residuals that come from the process of conversion of logs into lumber and this principally occurs due to lack of knowledge of the characteristics of the raw material, which complicates the pre-selection process (Melo et al, 2012)
Computational simulations of log cutting have been tested for specific variables and scenarios, as well as for different species, and the results have shown the importance of this technique for the optimization of the industrial process of log sawing methods and maximization of yield (Buehlmann and Thomas, 2001; Ikonen et al, 2003; Moberg and Nordmark, 2006; Pinto et al, 2006; Knapic et al, 2011; Berglund et al, 2013; Fredriksson et al, 2015; Stängle et al, 2015; Wery et al, 2018)
Summary
The extraction of timber from native forests has become one of the principal economic activities in all the States that make up the Legal Amazon at the beginning of the XXI century (Homma, 2011) This region is a large generator of residuals that come from the process of conversion of logs into lumber and this principally occurs due to lack of knowledge of the characteristics of the raw material, which complicates the pre-selection process (Melo et al, 2012). In Amazonian sawmills low lumber yield is a common occurrence and is estimated at approximately 41% in a report presented by Hummel (Hummel et al, 2010) This creates economic and environmental problems because a greater volume of raw material must be consumed in order to compensate for the volume of wood lost (Braz et al, 2014). The Conama resolution No 474/2016 reduced to 35% the coefficient of volumetric yield for sawn wood with the goal of being more in sync with the realities faced by the sawmill industry in the region (BRASIL, 2016), sanctioning the low yield of lumber from raw material.
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