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Pine and larch tracheids capture seasonal variations of climatic signal at moisture-limited sites

Belokopytova, Liliana V., Babushkina, Elena A., Zhirnova, Dina F., Panyushkina, Irina P., Vaganov, Eugene A.
Trees 2019 v.33 no.1 pp. 227-242
Larix sibirica, Pinus sylvestris, cell walls, climate, conifers, dry environmental conditions, growth rings, seasonal variation, tracheids, Siberia
KEY MESSAGE: Although the radial diameter and wall thickness of conifer tracheids from dry environments are climatic-sensitive across the full ring area, each cell parameter has a specific zone in a ring where its climatic response reaches the maximum. Seasonal dynamics of the timing and rate in cell production and differentiation imprint climate signals into intra-ring variations of anatomical wood structure (e.g. intra-annual density fluctuations). Despite recent methodological advances in quantitative wood anatomy, our understanding of xylem response to climate at the finest scale of intra-ring resolution is incomplete. The goal of this study is to investigate intra-ring changes of tracheid dimensions (cell radial diameter and wall thickness) controlled by moisture stress. Anatomical wood parameters of Pinus sylvestris and Larix sibirica from two drought-susceptible locations in Khakassia, South Siberia, were analysed. We found that inter-annual variation of tracheid parameters regularly exceeds the variation between radial tracheid files. This suggests that the climatic signal is recorded throughout the entire ring. However, each cell parameter has a specific zone in the ring where its climatic response reaches the maximum. The climatic response of the radial cell diameter has a temporal shift across the ring, which is particularly apparent in pine rings. The climatic response of cell wall thickness at the intra-ring scale has a more complex pattern. Our results facilitate investigation of the climate impact on tree rings at the finest intra-ring scale by quantifying the timing of climatic impact on ring structure and identifying specifically when climate impacts the formation of a particular cell.