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Drivers of intra‐seasonal δ 13 C signal in tree‐rings of Pinus sylvestris as indicated by compound‐specific and laser ablation isotope analysis

2023; Wiley; Volume: 46; Issue: 9 Linguagem: Inglês

10.1111/pce.14636

1365-3040

Katja T. Rinne‐Garmston, Yu Tang, Elina Sahlstedt, Bartosz Adamczyk, Matthias Saurer, Yann Salmon, María del Rosario Domínguez Carrasco, Teemu Hölttä, Marco M. Lehmann, Lan Mo, Giles Young,

Lichen and fungal ecology

Abstract Carbon isotope composition of tree‐ring (δ 13 C Ring ) is a commonly used proxy for environmental change and ecophysiology. δ 13 C Ring reconstructions are based on a solid knowledge of isotope fractionations during formation of primary photosynthates (δ 13 C P ), such as sucrose. However, δ 13 C Ring is not merely a record of δ 13 C P . Isotope fractionation processes, which are not yet fully understood, modify δ 13 C P during sucrose transport. We traced, how the environmental intra‐seasonal δ 13 C P signal changes from leaves to phloem, tree‐ring and roots, for 7 year old Pinus sylvestris , using δ 13 C analysis of individual carbohydrates, δ 13 C Ring laser ablation, leaf gas exchange and enzyme activity measurements. The intra‐seasonal δ 13 C P dynamics was clearly reflected by δ 13 C Ring , suggesting negligible impact of reserve use on δ 13 C Ring . However, δ 13 C P became increasingly 13 C‐enriched during down‐stem transport, probably due to post‐photosynthetic fractionations such as sink organ catabolism. In contrast, δ 13 C of water‐soluble carbohydrates, analysed for the same extracts, did not reflect the same isotope dynamics and fractionations as δ 13 C P , but recorded intra‐seasonal δ 13 C P variability. The impact of environmental signals on δ 13 C Ring , and the 0.5 and 1.7‰ depletion in photosynthates compared ring organic matter and tree‐ring cellulose, respectively, are useful pieces of information for studies exploiting δ 13 C Ring .