Distribuição química elementar em anéis de crescimento de Rhizophora mangle L. através de análise dendroquímica

Abstract

The present study evaluates the dendrochemical potential of the Rhizophora mangle species through the non-destructive technique of X-ray micro-fluorescence. For this purpose, eight transverse samples of R. mangle trees were collected, corresponding to the physiographic type of fringe in the mangrove forest adjacent to the Piracão River in the State Biological Reserve of Guaratiba, Rio de Janeiro. Later, dendrochronological and dendrochemical analysis were performed. The elements S, Cl, K, Ca, Ti, Mn, Fe and Sr were detected. However, calcium (Ca) and potassium (K) were the elements chosen for the dendrochemical analysis, due to the concentrations found in the samples, the presence of temporal variation tendencies and their ecophysiological function. The results corroborated the occurrence of annual growth rings for the species. However, the low sample size hampered the dendrochronological characterization. According to the elemental analysis, trends of decrease in concentration over time were observed for Ca and tendencies of increase in the elementary concentration of K were verified. Ca presented a significant difference between the elemental concentrations of Heardwood and Sapwood, being higher in the former. This is due to physiological processes related to elemental translocation and heartwood - sapwood differentiation. It is concluded that R. mangle presents potential for dendrochemical research. The X-ray micro fluorescence technique is an appropriate tool for this type of studies applied to mangrove species. However, sample collection and detection limits may influence the full identification of the elements in the samples