Variação geográfica e intraespecífica da densidade básica da madeira do gênero Eschweilera (E. coriacea e E. truncata) no estado do Amazonas.

Abstract

Many uncertainties exist in the estimates of carbon stocks and the capacity of sequestration of carbon in tropical forests. Wood specific gravity (WSG) has been used as a variable in models to estimate forest biomass. However the average values used for wood density for each species neglects the variation in wood density of a particular species in different areas. Also, the sampling method used to evaluate the average density of each tree should consider the radial and axial variations in the WSG. The objective of this research was to determine the variations in the WSG of Eschweilera coriacea (DC.) S. A Mori, inside of the tree and among spatially different locations within the State of Amazon, to determine the results of using the average WSG in the estimation of forest biomass. Destructive sampling was used in the collection of 28 trees with a diameter at breast height of between 18 and 38 cm. The sample locations were distributed in six municipal districts of Amazons State. The trees were sawn into sections of 10 cm in thickness in the locations at the base of the bole, DAP, half way up the bole and top of the bole. The basic density of the wood was determined following the norm ASTM (2007). The basic density of the wood of E. coriacea varied within the individuals in the radial direction (p: 0.00079), in the axial direction (p: 7.27e -09) and among sites (p = 0.000324), demonstrating that variation exists in the basic density of the wood for the same species and among sites. Data of basic density collected at one site to evaluate the biomass in another site generated errors of up to 24%. The sampling method was developed to evaluate the basic density of the function of the axial and radial position at a given sampling point. The average density in the axial position of the DAP was found to be a representative density of the medium density of the tree (R²: 0.98; p < 0.0001). The proportion of 20% of the ray of the tree represents the density basic average of the tree for the E. coriacea (R²: 0.94; p < 0.0001), indicating that is possible to adapt the collection of the sample correctly to esteem the density. These results demonstrate that not taking into account variation among sites can cause significant error in the estimation of forest biomass. The method employed here to estimate the density of the tree based on a percentage of the ray was shown promising in standardization of the sampling of the tree in a representative way.