Geochemical fingerprinting of Norway spruce from the Eastern Carpathians: Sr isotopic and multi-elemental signatures

Ensuring efficient wood traceability within procurement chains is essential for establishing sustainable forest management and minimizing environmental damage in countries that produce and export timber. While some progress has been made with key legislative reforms to tackle this issue, the effectiveness of law enforcement still relies on the availability of appropriate analytical tools to determine the provenance of wood. This study documents the Sr isotopic and multi-elemental signatures of Norway spruce trees in the Eastern Carpathians, Romania - an area known for intensive forest logging. The research focused on trees from Rodna, Rarău, and Călimani, analyzing tree rings from 1970 to 2020 to assess temporal variability and develop site-specific geochemical fingerprints. In conjunction with tree samples, corresponding soil, groundwater, and river samples were analyzed, providing a comprehensive view of the bioavailable ⁸⁷Sr/⁸⁶Sr ratios in these ecosystems. The study found a strong correlation between the Sr isotope ratios in the wood and those in corresponding water and soil samples, confirming that the wood accurately mirrors local geochemical signatures. The Sr isotope ratios were consistent across most of the cores from trees within the same site but varied among sites within the same region. Principal Component Analysis of the Sr isotopic and multi-elemental data highlighted closer clustering of samples from the Călimani area, though distinguishing the samples from the Rodna and Rarău regions proved more difficult due to overlapping data points. This study broadens our understanding of geochemical variability and its implications. The insights gained provide a valuable foundation for future research aimed at enhancing wood traceability methods.