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Key message: Resin production and growth in Pinus pinaster and Pinus pinea show a trade-off under varying environmental conditions, impacting future resin yields under climate change. Resin production in pines constitutes an important defense mechanism against biotic and abiotic factors, and it is also an important forestry product. In Portugal, resin is mainly extracted from Pinus pinaster and to a lesser extent from Pinus pinea, the two most widespread pine species in the country. The resin tapping season coincides with the growing season, from spring to autumn. Thus, growth and resin production may compete for carbon, although their response to environmental conditions can differ. This study investigates how the daily growth and biweekly resin production of P. pinaster and P. pinea in a mixed stand respond to environment over the 2021 growing season. During the resin tapping period, growth of both species showed a positive correlation with temperature, soil moisture, air relative humidity and radiation. Resin yield of both species showed a positive relation with soil temperature, and a negative relation with growth, suggesting a trade-off between growth and resin yield. Our results indicate that both growth and resin yield increase with temperature, with growth being more sensitive to soil moisture and relative humidity. Under a scenario of rising temperatures and precipitation reduction, both functions (growth and resin yield) are expected to be affected positively. However, resin production depends on carbon assimilation and allocation, both of which are reduced or altered during periods of extreme drought. This can lead to increasing competition for carbon allocation between growth, storage and resin yield, making resin yield responses to climate change scenarios uncertain. [ABSTRACT FROM AUTHOR]

Tree-ring width chronologies of Pinus sibirica Du Tour from near the upper treeline in the Western Sayan, Southern Siberia are found to have an exceptional (below mean–3SD) multi-year drop near 1700 CE, highlighted by the seven narrowest-ring years in a 1524–2022 regional chronology occurring in the short span of one decade. Tree rings are sometimes applied to reconstruct seasonal air temperatures; therefore, it is important to identify other factors that may have contributed to the growth suppression. The spatiotemporal scope of the "nosedive" in tree growth is investigated with a large network of P. sibirica (14 sites) and Larix sibirica Ledeb. (61 sites) chronologies, as well as with existing climatic reconstructions, natural archives, documentary evidence (e.g., earthquake records), and climate maps based on 20th-century reanalysis data. We conclude that stress from low summer temperatures in the Little Ice Age was likely exacerbated by tree damage associated with weather extremes, including infamous Mongolian "dzuds", over 1695–1704. A tropical volcanic eruption in 1695 is proposed as the root cause of these disturbances through atmospheric circulation changes, possibly an amplified Scandinavia Northern Hemisphere teleconnection pattern. Conifer tree rings and forest productivity recorded this event across all of Altai–Sayan region. [ABSTRACT FROM AUTHOR]

Tree-ring width chronologies of Pinus sibirica Du Tour from near the upper treeline in the Western Sayan, Southern Siberia are found to have an exceptional (below mean–3SD) multi-year drop near 1700 CE, highlighted by the seven narrowest-ring years in a 1524–2022 regional chronology occurring in the short span of one decade. Tree rings are sometimes applied to reconstruct seasonal air temperatures; therefore, it is important to identify other factors that may have contributed to the growth suppression. The spatiotemporal scope of the “nosedive” in tree growth is investigated with a large network of P. sibirica (14 sites) and Larix sibirica Ledeb. (61 sites) chronologies, as well as with existing climatic reconstructions, natural archives, documentary evidence (e.g., earthquake records), and climate maps based on 20th-century reanalysis data. We conclude that stress from low summer temperatures in the Little Ice Age was likely exacerbated by tree damage associated with weather extremes, including infamous Mongolian “dzuds”, over 1695–1704. A tropical volcanic eruption in 1695 is proposed as the root cause of these disturbances through atmospheric circulation changes, possibly an amplified Scandinavia Northern Hemisphere teleconnection pattern. Conifer tree rings and forest productivity recorded this event across all of Altai–Sayan region.

Oxygen (δ 18 O) and hydrogen (δ 2 H) stable isotope ratios are tightly coupled in precipitation and, albeit damped, in leaf water, but are often decoupled in tree-ring cellulose. The environmental and physiological conditions in which this decoupling occurs are not yet well understood. We investigated the relationships between δ 18 O and δ 2 H and tree-ring width (TRW), tree crown volume, tree age and climate in silver fir and Douglas-fir and found substantial differences between δ 18 O and δ 2 H. Overall, δ 18 O-δ 2 H correlations were weak to absent but became significantly negative under high summer vapour pressure deficit (VPD). δ 18 O and δ 2 H had positive and negative nonlinear relationships with TRW, respectively, with clear relationships at the site and tree levels for silver fir and, to a lesser extent, for Douglas-fir. Age trends for silver fir were weakly negative in δ 18 O but positive in δ 2 H. Tree crown volume and δ 18 O or δ 2 H had no significant relationships. Most strikingly, δ 18 O strongly depended on spring climate (precipitation and VPD), whereas δ 2 H depended on summer climate (temperature and VPD) for both species. Our study shows that the δ 18 O-δ 2 H decoupling in tree-ring cellulose in two temperate conifer species could be highlighted by their contrasting relationships to climate and tree intrinsic variables (TRW, age)., (© 2024 The Author(s). Plant, Cell & Environment published by John Wiley & Sons Ltd.)