An optimized method for stable isotope analysis of tree rings by extracting cellulose directly from cross-sectional laths

Abstract

a b s t r a c tStable isotopes in tree-ring α-cellulose are valued as environmental proxies and their use is steadily increasing; however, preparation of α-cellulose is a bottleneck in isotope analysis. Recent methodological breakthrough for extracting tree-ring α-cellulose directly from tree-ring cross-sectional laths drastically increased the throughput of tree-ring isotope data. In this paper, we evaluate our recently designed "cross-section" method. This method employs polytetrafluoroethylene (PTFE) cases, enabling direct extraction of α-cellulose from 1-mm thick tree-ring laths, in combination with fixation sheets to prevent disintegration of freeze-dried α-cellulose laths. Perforated PTFE cases are easily producible at an affordable cost. They are made of commonly available lab consumables in catalogs and do not require specially made PTFE parts. Freeze-dried α-cellulose laths preserved distinct anatomical structure, enabling precise separation at the tree-ring boundaries. Once separated from a lath, tree-ring α-cellulose can be weighed directly into silver or tin capsules for analysis. We checked chemical purity of α-cellulose prepared by the cross-section method from five tree species (larch, pine, spruce, beech, and oak). Residual lignin and hemicellulose contents were quantitatively assessed by Fourier transform infrared spectrometry and gas chromatography. The average chemical purity of α-cellulose laths from the five species was 94.5%, similar to the chemical purity of α-cellulose prepared with the standard Jayme-Wise method. Both oxygen and carbon isotope values of α-cellulose prepared by the cross-section method also closely matched those prepared by the standard method. We conclude that, by overhauling the method of α-cellulose preparation for tree-ring isotope analysis, we increased throughput of tree-ring oxygen and carbon isotope data without sacrificing sample purity.

Increased water‐use efficiency translates into contrasting growth patterns of Scots pine and sessile oak at their southern distribution limits

“…All sampled trees were older than 70 years to avoid the effect of juvenile wood on the carbon isotope ratios (Leavitt, ). The holocellulose extraction followed the procedures described by Schollaen, Baschek, Heinrich, and Helle () applying a novel cross‐section extraction method, which is a re‐design of the technique proposed by Kagawa, Sano, Nakatsuka, Ikeda, and Kubo (). The main advantage of this technique is the time reduction invested in each sample since it allows the cellulose extraction of different rings at the same time.…”

Seasonal variations in the stable oxygen isotope ratio of wood cellulose reveal annual rings of trees in a Central Amazon terra firme forest

“…Although using whole wood (bulk wood) for isotopic analyses is reportedly acceptable, uncertainties regarding the analysis of whole wood remain (Loader et al 2003;Ferrio and Voltas 2005;Verheyden et al 2005b), especially for analysis at intra-annual scales. In addition, a recent advance has allowed the extraction of α-cellulose directly from cross-sectional laths before the subdivision of tree rings (Li et al 2011;Xu et al 2011;Kagawa et al 2015). Therefore, we used α-cellulose for isotope analysis and applied the cross-section method proposed by Kagawa et al (2015) for the extraction.…”

“…In addition, a recent advance has allowed the extraction of α-cellulose directly from cross-sectional laths before the subdivision of tree rings (Li et al 2011;Xu et al 2011;Kagawa et al 2015). Therefore, we used α-cellulose for isotope analysis and applied the cross-section method proposed by Kagawa et al (2015) for the extraction. The chemical protocol was based on the Jayme and Wise method (Green 1963) modified for α-cellulose extraction (Mullane et al 1988;Loader et al 1997;Xu et al 2011).…”

Analysis of the interdecadal variability of summer precipitation in central Japan using a reconstructed 106 year long oxygen isotope record from tree ring cellulose

“…The analytical precision of a laboratory working standard (Merck cellulose; Darmstadt, Germany) measurement was about 0.15‰ (1 σ ). The oxygen isotopic analyses for the other two wood disks (167 and 179 years old) were conducted at RIHN, using a “cross‐section” method for α ‐cellulose extraction [ Kagawa et al , ]. This method extracts α ‐cellulose not from individual rings but directly from a 1 mm thick tree ring plate.…”

“…The tree ring cellulose samples were then cut from the α ‐cellulose plate, weighted, and wrapped into silver foil. Kagawa et al [] found no significant difference between the δ 18 O values determined by the cross‐section method and those determined by the conventional method. This method has already been applied to several species [e.g., Xu et al , , ; Sano et al , ; Xu et al , ].…”