Análise dos isótopos estáveis na caracterização e rastreabilidade da madeira de Eucalyptus grandis
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Data
2021-04-08
Autores
Silva, Jessica Alexandra da
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Universidade Estadual Paulista (Unesp)
Resumo
O gênero Eucalyptus destaca-se no meio comercial de reflorestamento devido ao alto rendimento madeira e facilidade de adaptação de suas espécies a diferentes climas e regiões. Contudo, pesquisas relacionadas à análise de isotópica aplicadas em madeira de reflorestamento são raras para espécies plantadas no Brasil. Dentre elas, o Eucalyptus grandis é uma das espécies mais cultivadas e possui elevada importância econômica, podendo ser encontrada nas formas seminal e clone. As análises de isótopos estáveis (AIE) são amplamente utilizadas na identificação da origem geográfica e também na detecção de adulterações em diversos produtos agrícolas. De modo similar, as relações isotópicas estáveis de δ13C, δ18O e δ2H em madeira - principalmente em espécies nativas - são vastamente empregadas em estudos climáticos e cronológicos. Entretanto, um dos maiores problemas encontrados na AIE em madeira está na dificuldade de se realizar a amostragem de forma que represente a variação isotópica na árvore inteira, sem a necessidade de cortá-la. Assim, este trabalho avaliou a variação dos valores isotópicos δ13C, δ18O e δ2H na madeira de clones de árvores de E. grandis com intuito de otimizar a amostragem e a análise isotópica. Nesse sentido, os valores de δ13C foram determinados por duas técnicas de obtenção da fase gasosa da amostra, combustão e conversão em alta temperatura, a fim de comparar-se os resultados obtidos entre elas. Conjuntamente, foi demonstrada a variação isotópica dentro de cada árvore e entre árvores, bem como a variação dos isótopos no sentido radial dos discos amostrados. Por fim, os resultados de δ13C realizadas nas duas técnicas demonstraram alta concordância entre os valores. Enquanto que, a variação radial de δ13C e δ2H demonstraram moderadas oscilações entre os pontos, principalmente nos discos a 12,5%, 37,5% e 62,5% em relação à altura das árvores. Esse comportamento não foi observado para o δ18O que não demonstrou tendência padrão dos pontos no sentido radial conforme notado nos resultados de δ13C e δ2H. Ainda assim, conforme demonstrado neste trabalho as amostragens em espécies de E. grandis podem ser realizadas extraindo-se amostras sem a derrubada das árvores.
The genus Eucalyptus stands out in the commercial medium of reforestation due to the high wood yield and the ease of adaptation of its species to different climates and regions. However, research related to the analysis of isotope applied to reforestation wood is rare for species planted in Brazil. Among them, Eucalyptus grandis is one of the most cultivated species and has high economic importance, and can be found in seminal and clone forms. The stable isotope analyzes (SIA) are widely used in the identification of geographical origin and also in the detection of adulterations in several agricultural products. Similarly, the stable isotopic relationships of δ13C, δ18O and δ2H in wood - mainly in native species - are widely used in climatic and chronological studies. However, one of the biggest problems found in the SIA in wood is the difficulty of carrying out a sampling in a way that represents the isotopic variation in the entire tree, without the need to cut it. Thus, this work evaluated the isotopic variation of values δ 13C, δ18O and δ2H in the wood of E. grandis tree clones in order to optimize the sampling and isotopic analysis. In this sense, the δ 13C values were determined by two techniques for obtaining the gas phase of the sample, combustion and conversion at high temperature, in order to compare the results obtained between them. Together, the isotopic variation within each tree and between trees was demonstrated, as well as the variation of the isotopes in the radial direction of the sampled discs. Finally, the results of δ13C performed in the two techniques demonstrated high agreement between the values. Whereas, the radial variation of δ13C and δ2H showed moderate oscillations between the points, mainly in the discs at 12.5%, 37.5% and 62.5% in relation to the height of the trees. This behavior was not observed for δ18O which is not a standard pattern of points not radial sense as noted in the results for δ13C and δ2H. Even so, as determined in this work, sampling in E. grandis species can be performed by extracting not the felling of the trees.
The genus Eucalyptus stands out in the commercial medium of reforestation due to the high wood yield and the ease of adaptation of its species to different climates and regions. However, research related to the analysis of isotope applied to reforestation wood is rare for species planted in Brazil. Among them, Eucalyptus grandis is one of the most cultivated species and has high economic importance, and can be found in seminal and clone forms. The stable isotope analyzes (SIA) are widely used in the identification of geographical origin and also in the detection of adulterations in several agricultural products. Similarly, the stable isotopic relationships of δ13C, δ18O and δ2H in wood - mainly in native species - are widely used in climatic and chronological studies. However, one of the biggest problems found in the SIA in wood is the difficulty of carrying out a sampling in a way that represents the isotopic variation in the entire tree, without the need to cut it. Thus, this work evaluated the isotopic variation of values δ 13C, δ18O and δ2H in the wood of E. grandis tree clones in order to optimize the sampling and isotopic analysis. In this sense, the δ 13C values were determined by two techniques for obtaining the gas phase of the sample, combustion and conversion at high temperature, in order to compare the results obtained between them. Together, the isotopic variation within each tree and between trees was demonstrated, as well as the variation of the isotopes in the radial direction of the sampled discs. Finally, the results of δ13C performed in the two techniques demonstrated high agreement between the values. Whereas, the radial variation of δ13C and δ2H showed moderate oscillations between the points, mainly in the discs at 12.5%, 37.5% and 62.5% in relation to the height of the trees. This behavior was not observed for δ18O which is not a standard pattern of points not radial sense as noted in the results for δ13C and δ2H. Even so, as determined in this work, sampling in E. grandis species can be performed by extracting not the felling of the trees.
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Palavras-chave
Eucalyptus grandis, Isótopos estáveis, Madeira, Stables isotopes, Cellulose