CELLULOSE ISOTOPE RATIOS AS A PROXY TO ECOPHYSIOLOGICAL AND PALEOCLIMATE RECORD

It's well known that the hydrogen and oxygen isotope ratios of precipitation correlate with climate and global circulation patterns. In general the pattern is that the higher the ambient temperature the higher the oxygen-18 and deuterium abundance of the precipitation. The oxygen and hydrogen isotope ratios of tree ring cellulose are ultimately derived from the oxygen and hydrogen isotope ratios of plant available water which is closely correlated with that of precipitation. If cellulose is well preserved, then it holds great potential as a proxy for paleoclimate. Dr. Hope Jahren's ( John Hopkins University ) laboratory and mine have analyzed tree ring cellulose from samples in an arctic island approximately 50 million years old with some interesting results. The isotopic signal of cellulose, however, is a mixed signal and the challenge is to disentangle these signals. Dr. William Anderson's ( Florida International University ) laboratory and mine have developed a new technique towards this end. Once it is refined, we plan to use it in determining water sources of the paleo samples as well as in coastal plants.

Sample Publications

Jahren , H. and Sternberg, L. da S.L. Eocene Meridional Weather Patterns Reflected in the Oxygen Isotopes of Arctic Fossil Wood. GSA Today 12: 4-9. 2002.

Jahren, A. H. and Sternberg L. da S. L. Humidity estimate for the middle Eocene Arctic rainf forest. Geology 31: 463-466. 2003.

Sternberg L. da S. L., Anderson W. and Morrison K. Separating soil and leaf water 18O isotopic signals in plant stem cellulose. Geochimica Cosmochimica Acta 67: 2561-2566. 2003

Sternberg L. da S. L., Pinzon M. C., Anderson W. T. & Jahren A.H. Variation in oxygen isotope fractionation during cellulose synthesis: intramolecular and biosynthetic effects. Plant Cell and Environment 29: 1881-1889. 2006.

Sternberg L. da S. L., Pinzon M. C., Vendramini P. F., Anderson W. T., Jahren A. H., Beuning C. Oxygen isotope ratios of cellulose-derived Phenylglucosazone: an improved paleoclimate indicator of environmental water and relative humidity. Geochimica Cosmochimica Acta 71: 2463-2473(2007).

Jahren A. H., Sternberg L. da S.L. Annual patterns within tree rings of the Arctic Middle Eocene (ca 45Ma): Isotopic signatures of precipitation, relative humidity and deciduousness. Geology 36: 99 -102 (2008).

Heterotrophically synthesized cellulose from wheat seeds. Seeds are germinated in the dark making endosperm starch as the only substrate for its synthesis.

Chemical process whereby the oxygens attached to carbon 1 and 2 on the glucose moieties are eliminated. In this way we can measure the oxygen isotope ratios of the oxygen attached to the second carbon of the glucose moieties in cellulose.

Final product of cellulose hydrolysis and derivatization. The cellulose is the white powder on the right and the glucose phenylosazone is the yellow product on the left.