2 research outputs found

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

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    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 (R¬≤: 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 (R¬≤: 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.Existem grandes incertezas nas estimativas do estoque e da capacidade de sequestro de carbono em florestas tropicais. A densidade da madeira tem sido utilizada como vari√°vel em modelos de estimativa de biomassa florestal, por√©m a inser√ß√£o de uma m√©dia para cada esp√©cie negligencia as varia√ß√Ķes na densidade para a esp√©cie em diferentes s√≠tios. Al√©m disso, o m√©todo de amostragem para estimar a densidade m√©dia de cada √°rvore deveria considerar as varia√ß√Ķes radiais e axiais na densidade b√°sica da madeira. Esta pesquisa teve por objetivo, evidenciar as varia√ß√Ķes da densidade b√°sica da madeira de Eschweilera coriacea (DC.) S. A Mori), dentro da √°rvore e entre diferentes s√≠tios no estado do Amazonas, para inferir sobre as consequ√™ncias da utiliza√ß√£o da m√©dia da densidade da madeira em estimativas de biomassa florestal. Foram coletadas destrutivamente amostras de 28 √°rvores com DAP entre 18 e 38 cm, distribu√≠das em seis munic√≠pios do estado do Amazonas, as √°rvores foram seccionadas em discos de 10 cm de di√Ęmetro nas posi√ß√Ķes do fuste Base, DAP, Meio e Topo, com base na altura comercial, para a confec√ß√£o dos corpos de prova. A densidade b√°sica da madeira foi determinada seguindo a norma ASTM (2007). A densidade b√°sica da madeira de E. coriacea variou dentro dos indiv√≠duos no sentido radial (p= 0.00079), axial (p= 2 x 10-16) e entre s√≠tios (p= 0.000324), comprovando que h√° varia√ß√Ķes na densidade b√°sica da madeira para a mesma esp√©cie dentro da √°rvore e entre s√≠tios. Utilizar dados de densidade b√°sica coletados em um s√≠tio para estimar a biomassa em outro s√≠tio, pode gerar erro de at√© 24%. Foi desenvolvido um m√©todo de amostragem para estimar a densidade b√°sica em fun√ß√£o da posi√ß√£o axial e radial a partir de um ponto de amostragem. A densidade m√©dia na posi√ß√£o axial DAP estima uma densidade representativa da densidade m√©dia da √°rvore (R¬≤: 0.98; p < 0.0001 ). A propor√ß√£o de 20% do raio da √°rvore representa a densidade b√°sica m√©dia da √°rvore para o E. coriacea (R¬≤: 0.94; p < 0.0001 ), indicando que √© poss√≠vel adequar a coleta da amostra para estimar a densidade corretamente. Os resultados demonstram que utilizar amostragem incompleta e negligenciar a varia√ß√£o entre s√≠tios, ocasiona erros nas estimativas de biomassa florestal. O m√©todo de estimativa da densidade da √°rvore a partir de uma percentagem do raio mostrou-se promissor para padronizar a amostragem da √°rvore de forma representativa

    Soil fertility and drought interact to determine large variations in wood production for a hyperdominant Amazonian tree species

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    Introduction: The productivity of the Amazon Rainforest is related to climate and soil fertility. However, the degrees to which these interactions influence multiannual to decadal variations in tree diameter growth are still poorly explored. Methods: To fill this gap, we used radiocarbon measurements to evaluate the variation in tree growth rates over the past decades in an important hyperdominant species, Eschweilera coriacea (Lecythidaceae), from six sites in the Brazilian Amazon that span a range of soil properties and climate. Results: Using linear mixed-effects models, we show that temporal variations in mean annual diameter increment evaluated over a specific time period reflect interactions between soil fertility and the drought index (SPEI-Standardized Precipitation and Evapotranspiration Index). Discussion: Our results indicate that the growth response of trees to drought is strongly dependent on soil conditions, a facet of forest productivity that is still underexplored, and which has great potential for improving predictions of future tropical tree growth in the face of projected climate change
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