Intra- and Intertree Variability of the ⁸⁷Sr/⁸⁶Sr Ratio in Apple Orchards and Its Correlation with the Soil ⁸⁷Sr/⁸⁶Sr...

The ⁸⁷Sr/⁸⁶Sr ratio of horticultural products mostly derives from that of the bioavailable Sr fraction of the soil where they grow and, therefore, varies according to the local geolithological features. This study investigated the intra- and intertree variability of the ⁸⁷Sr/⁸⁶Sr ratio in two apple orchards in South Tyrol and its relation with the soil ⁸⁷Sr/⁸⁶Sr ratio. In both orchards, a moderate homogeneity of the ⁸⁷Sr/⁸⁶Sr ratio was observed among subsamples of the same tree part (shoot axes, leaves, apple peels, and pulps). Moreover, the ⁸⁷Sr/⁸⁶Sr ratio homogeneity among tree parts was high intratree and low intertree. The variability of the ⁸⁷Sr/⁸⁶Sr ratio within the tree and within the orchard is explained in light of the ⁸⁷Sr/⁸⁶Sr ratios of the soil. This ⁸⁷Sr/⁸⁶Sr variability within orchards does not preclude its use as a geographical tracer; however, this aspect should be evaluated to correctly design a sampling campaign or to generalize the results.