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To independently validate this initial ring age-assignment, between one and three trees from each site were selected for bomb-peak ).
All measurements were performed on α-cellulose or holocellulose extracts rather than whole wood, as these wood fractions are immobile and will thus produce more precise radiocarbon dates than if whole wood were used (Leavitt and Bannister ). Keck Carbon Cycle Accelerator Mass Spectrometer (KCCAMS Facility) located at the Earth System Science Department at the University of California in Irvine, USA.
Therefore, tree-ring studies undertaken at new locations in the tropics require independent validation of the annual nature of tree rings, irrespective of how the studied species behaves in other locations.
Tropical dendrochronology is a steadily growing field, and the number of species known to be suitable for tree-ring analysis is also rising.
at the onset of the thermonuclear tests), these signatures are mostly well distributed across the hemispheres (Hua et al.
C dating to test the annual character of tree rings from four sites across the Amazon basin that vary in their precipitation and insolation seasonality.
Stem discs were collected in 2011 (Bolivia), 2013 (Ecuador) and 2014 (Suriname) from trees felled for timber or during the installation of overhead power lines.
It is important to understand the factors controlling ring formation, since regional variation in these factors could cause trees in different regions to form tree rings at different times.
For each sample, 2–4 rings putatively dated from 1955 to 1985 were selected for analysis, and the wood cut from each individual ring using a scalpel (in total 25 samples from 8 different trees). At KCCAMS holocellulose was isolated following a method adapted from Leavitt and Danzer () with Ankom TM F57 Dacron filter bags (25 µm effective pore size) used as sample pouches.
Cellulose extraction for the Suriname samples was conducted in Leeds, following the batch method of Wieloch et al. Wood samples loaded in pouches were lined up in a Soxhlet apparatus and initially treated with a 2:1 mixture of 99.5% toluene and high-performance liquid chromatography (HPLC) grade ethanol for 24 h, and later by pure HPLC ethanol for another 24 h.
Subsequent processing used hot Milli-Q water to remove solvent residues, followed by bleaching at 70 °C with a sodium chlorite solution acidified with 2 ml of 100% glacial acetic acid.
Once samples turned white, they were washed with Milli-Q water and gently dried at 50 °C in a conventional drying oven.
Finally, although radii within each tree were crossdated, a conventional inter-tree crossdating analysis was not conducted for this study.