Laser ablation-combustion-GC-IRMS--a new method for online analysis of intra-annual variation of  13C in tree rings

Abstract

We present a new, rapid method for high-resolution online determination of delta13C 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-microm-wide holes. Ablated wood dust was combusted to CO2 at 700 degrees 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 delta13C 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 delta13C along three parallel ablation lines on the same core showed high congruence. A conservative estimate of the precision was +/- 0.24 per thousand. 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 delta13C over 22 years was about 5 per thousand, ranging from -27 to -22.3 per thousand. The most obvious pattern was a sharp decline in delta13C 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 delta13C signal in tree rings.

Continuous isotopic composition measurements of tropospheric CO<sub>2</sub> at Jungfraujoch (3580 m a.s.l.), Switzerland: real-time observation of regional pollution events

“…The low δ 13 C s values during all events are, however, consistent with combustion sources. δ 13 C values reported for different combustion sources are on the order of −24‰, for coal, −30‰, to −26‰, for oil, −44‰, for natural gas and −27‰, to −22‰, for combustion of wood (Ciais et al, 1995;Andres et al, 1999;Schulze et al, 2004). The low values of events II, III and IV thus suggest a major contribution from oil combustion while the higher value of event I would again (see Fig.…”

“…A mean value for the 18 O isotope distribution in soil water can be provided by the correlation between the seasonal evolution of δ 18 O in precipitation and air temperature. In fact, the δ 18 O value in VSMOW (Vienna Standard Mean Ocean Water) can be estimated from a linear regression (Rozanski et al, 1982(Rozanski et al, , 1992Schürch et al, 2003) …”

Reconstructing terrestrial nutrient cycling using stable nitrogen isotopes in wood

“…Consequently, pooling rings for N analysis may obscure shortterm fluctuations in ecosystem N dynamics. As analytical capabilities continue to improve, annual and even subannual resolution of wood  15 N patterns through separating earlywood and latewood could occur, perhaps by using very large samples and laser ablation techniques, as has been done for  13 C (Schulze et al 2004) Finally, there is huge variation in reporting wood  15 N data in published manuscripts that must be addressed and standardized (Wolkovich et al 2012). The most important point is that reporting the exact chronology used for the wood  15 N measurements is essential.…”

Age-Effect on Intra-Annual δ13C-Variability within Scots Pine Tree-Rings from Central Siberia

“…Since the offset between cellulose and natural wood is constant (1.5 in conifers) and independent of season [45,46], cellulose extraction was unnecessary.…”