© 2004 Heron Publishing—Victoria, Canada
Laser ablation-combustion-GC-IRMS—a new method for online analysis of intra-annual variation of δ13C in tree rings
Brigit Schulze (1), Christian Wirth (1, 2), Petra Linke (1), Willi A. Brand (1), Iris Kuhlmann (1), Viviana Horna (1) and Ernst-Detlef Schulze (1)
1. Max-Planck-Institut für Biogeochemie, P.O. Box 100164, 07701 Jena, Germany / 2. Corresponding author (cwirth@bgc-jena.mpg.de or cwirth@princeton.edu) / Received November 6, 2003; accepted April 2, 2004; published online September 1, 2004
Summary
We present a new, rapid method for high-resolution online determination of δ13C in tree rings, combining laser ablation (LA), combustion (C), gas chromatography (GC) and isotope ratio mass spectrometry
(IRMS) (LA-C-GC-IRMS). Sample material was extracted every 6 min with a UV-laser from a tree core, leaving 40-µm-wide holes.
Ablated wood dust was combusted to CO2 at 700 °C, separated from other gases on a GC column and injected into an isotope ratio mass spectrometer after removal of
water vapor. The measurements were calibrated against an internal and an external standard. The tree core remained intact
and could be used for subsequent dendrochronological and dendrochemical analyses. Cores from two Scots pine trees (Pinus sylvestris spp. sibirica Lebed.) from central Siberia were sampled. Inter- and intra-annual patterns of δ13C in whole-wood and lignin-extracted cores were indistinguishable apart from a constant offset, suggesting that lignin extraction
is unnecessary for our method. Comparison with the conventional method (microtome slicing, elemental analysis and IRMS) indicated
high accuracy of the LA-C-GC-IRMS measurements. Patterns of δ13C along three parallel ablation lines on the same core showed high congruence. A conservative estimate of the precision was
± 0.24‰. Isotopic patterns of the two Scots pine trees were broadly similar, indicating a signal related to the forest stand’s
climate history. The maximum variation in δ13C over 22 years was about 5‰, ranging from –27 to –22.3‰. The most obvious pattern was a sharp decline in δ13C during latewood formation and a rapid increase with spring early growth. We conclude that the LA-C-GC-IRMS method will be
useful in elucidating short-term climate effects on the δ13C signal in tree rings.
Keywords:
carbon isotopes, cellulose, dendroclimatology, early-wood, fractionation, lignin, palaeoclimatology, Pinus sylvestris, water relations, water-use efficiency.
