1. Effects of soil and atmospheric drought on intra-annual δ13C patterns in tree ringsValentina Vitali, Jernej Jevšenak, Georg von Arx, Marina Fonti, Meisha Holloway Phillips, Rubén D. Manzanedo, Kerstin Treydte, Lorenz Walthert, Roman Zweifel, Matthias Saurer, 2025, original scientific article Abstract: None declared.Conflict of interestHigh-resolution carbon isotope ratio (δ13C) measurements of tree rings have the potential to provide seasonal environmental information. However, due to the complexity of the wood formation processes, the reliability of this method for intra-seasonal reconstruction of growing conditions remains unclear. We, therefore, investigated the intra-annual variation of δ13C in tree rings of three conifer species (Pinus sylvestris, Picea abies, Abies alba) across sites from the Swiss Alps to assess their response to seasonal variation of soil water potential (SWP) and vapour pressure deficit (VPD). Intra-annual δ13C values at a resolution of 10 points per year were assessed using laser-ablation isotope-ratio mass spectrometry. Seasonal δ13C patterns were analyzed for synchronicity across trees and species, and their correlation with on-site environmental variables was used to determine the driving factors of δ13C, to reconstruct growing season dynamics, and to estimate timings of the growth dynamics and allocation of carbon to xylem formation. The δ13C patterns showed high synchronicity between species, with characteristic maxima in wet and dry years occurring in the middle of the ring and at the end of the ring, respectively. Seasonal δ13C variations reliably reflected atmospheric dryness. Higher than normal soil dryness hindered integration of further fresh assimilates into the xylem, thus allowing the identification of species- and site-specific threshold conditions that disrupt wood formation. The δ13C of Scots pine shows the strongest correlations with VPD and SWP, making it an excellent indicator of environmental variability. Silver fir appears to integrate carbon into xylem structural material over a longer season than the other conifers, whilst Norway spruce shows more plastic site-specific responses to environmental conditions. In conclusion, we identify how atmospheric and soil drought jointly impact tree growth and intra-annual δ13C patterns across conifer species, offering valuable insights for climate reconstructions and wider applications on forest dynamics.
Keywords: water availability, annual growth, laser ablation, tree-ring isotopes, carbon isotopes
Published in DiRROS: 01.10.2025; Views: 411; Downloads: 228
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2. Stable isotope composition in tree rings of Fagus sylvatica L. saplings reflects environmental variation induced by silviculture and microsite factorsJanez Kermavnar, Tom Levanič, Lado Kutnar, 2023, original scientific article Abstract: Natural regeneration of tree species is sensitive to silvicultural interventions. This study aimed to investigate the effects of different cutting intensities and local topographic and soil conditions on the composition of stable carbon (δ13C) and oxygen (δ18O) isotopes in wood of young beech (Fagus sylvatica L.) trees. Beech saplings in the regeneration layer were sampled in summer 2018 at three study sites in Dinaric fir-beech forests in the karst area of Slovenia. Three different cutting intensities were performed in 2012: i) no cutting (control), ii) 50% cutting of the stand’s growing stock creating thinned stands, and iii) 100% cutting of the stand’s growing stock creating 0.4 ha canopy gaps. We show that δ13C increased along the gradient of cutting intensity. On average, δ13C values in the tree rings were ∼ 2‰ increased in trees from canopy gaps than from closed control stands. Furthermore, δ13C was higher on south-facing slopes characterized by higher air temperatures and lower relative humidity compared to north-facing slopes of karst sinkholes. Additionally, the results suggest a dependence of δ18O on interannual and cross-site climatic variations, particularly in the case of summer precipitation amount. δ18O also responded to soil depth, with beech individuals exhibiting lower values on deeper soils, presumably characterized by higher soil water availability compared to shallow soils. The results are discussed in the context of future climate change, as many beech-dominated forests on karst terrain in the Dinaric Mountains are particularly affected by climate warming and drying due to prolonged and reoccurring summer droughts, intensified large-scale disturbances, and often shallow soils with low water storage capacity.
Keywords: stable carbon isotopes, stable oxygen isotopes, tree cutting, microclimate, drought stress, dinaric fir-beech forests
Published in DiRROS: 05.04.2023; Views: 1897; Downloads: 966
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3. Examination of stable carbon and oxygen isotopic variability in the cellulose and wholewood of Castanea sativa Mill., Fagus sylvatica L., Pinus sylvestris L. and Quercus robur L.B. Sladden, N.J. Loader, G.H.F. Young, D. McCarroll, 2018, original scientific article Abstract: This paper presents results from a comparison of wholewood and cellulose carbon and oxygen isotope ratios for four UK tree species. These species occur within the historic buildings archive as both primary and supplementary construction materials and have been used to reconstruct the climate of the past. New advances in the application of stable isotopes have widened the scope of the isotope approach, but require the time-consuming purification of cellulose. Comparison of the oxygen and carbon isotope signals preserved in the wood and cellulose components confirms and builds upon previous research in this field and provides additional insight into the covariance of these two sample types between species, an
Keywords: stable isotopes, tree ring, dendrochronology, dendroclimatology
Published in DiRROS: 04.02.2019; Views: 6942; Downloads: 4228
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