Circumferential and Longitudinal δ13C Variability in a Larix decidua Trunk from the Swiss Alps

Abstract

Tree-ring stable isotopes are insightful proxies providing information on pre-instrumental climate fluctuations, yet the variability of these data within a tree trunk has not been fully explored. Here, we analyze longitudinal and circumferential changes in tree-ring δ 13 C values from 1991-2010, considering seven height levels from 1 to 13 m above ground and six sampling directions (radii) separated by 60 • around the stem. The disk samples were taken from a 360-year old European larch (Larix decidua Mill.) that grew at 1675 m above sea level in the Simplon Valley, Switzerland. Results show that the circumferential δ 13 C variability, defined as the difference between the minimum and maximum isotope values within a single ring at a certain height, ranges from 0.5 to 2.8% . These differences appear substantial as they match the range of year-to-year variations retained in long tree-ring δ 13 C time series used for climate reconstruction. The assessment of longitudinal variability demonstrated a systematic change of~0.1% m −1 towards isotopically heavier (less negative) δ 13 C values with increasing tree height, likely reflecting a vertical gradient towards isotopically heavier needle tissue due to changing microclimatic conditions and CO 2 stratification within the canopy. Calibration against regional climate data indicates no substantial signal changes in δ 13 C values within the trunk. We conclude that the longitudinal isotope gradient adds uncertainty to long δ 13 C chronologies derived from subfossil material of unknown (and changing) sampling heights. The large circumferential variability recorded in the sub-alpine larch suggests that more than two cores are needed to analyze absolute δ 13 C values representative for each tree.

An overview on isotopic divergences – causes for instability of tree-ring isotopes and climate correlations

“…After going through the above options for limiting the climate-change-induced isotopic divergences, the confrontation of reconstructions from tree-ring isotopic series with independent archival systems, is a relevant approach for validating the reconstructions produced. The other archives potentially useable for such a purpose include geopotential height, ice cores, speleothems, lake sediments and historical data (Miller et al, 2006;Etien et al, 2008;Xu et al, 2016;Andreu-Hayles et al, 2017;Dinis et al, 2019;Muangsong et al, 2019;Yang et al, 2019).…”

Caracterização tecnológica de painéis engenheirados produzidos com madeira de paricá

“…Como não se tem o controle da idade da madeira no processo de produção, há probabilidade de existir diferentes proporções de madeira jovem e adulta nos painéis. Esper et al (2020) ressaltam que além da idade das árvores, a densidade dos painéis pode ser influenciada pela posição de retirada das lâminas da tora (próximo à medula, porção intermediária ou próximo a casca, e ainda ao longo do fuste).…”

The effect of provenance of historical timber on tree-ring based temperature reconstructions in the Western Central Alps

“…does not have the strongest response to summer temperature, as contained in the SUB chronology, but a weaker signal in the range of r ≈ 0.4 with JJA temperatures considering the RCS detrended chronology. However, the climate growth response of the historical timber could also be biased, due to the unknown position of the measured series in the tree trunk (Esper et al 2020b).…”