Peat cellulose isotopes as indicators of Asian monsoon variability

PAGES news • Vol 18 • No 1 • April 2010 Sc ie nc e H ig hl ig ht s: P ea tla nd s (δ13C increases) and vice versa (Williams and Flanagan, 1996). However, the effect of recycled methane on δ13C of Sphagnum biomarkers has the opposite relationship with moisture. When the peatland is wetter, more methane produced at depth is respired by methanotrophs that are symbiotic with Sphagnum, the resulting low-δ13C CO2 is assimilated by Sphagnum and recorded in lower δ13C of Sphagnum biomarkers. During drier conditions, the reverse occurs (Nichols et al., 2009; Raghoebarsing et al., 2005). These competing factors necessitate careful interpretation of Sphagnum biomarker δ13C measurements. Conclusions Isotopic and organic geochemistry analyses of peats are valuable approaches for understanding past climatic and environmental change. The complexity of peatlands requires a multi-proxy approach to fully exploit the paleoenvironmental signatures contained within peat archives. Further research is also needed into the factors controlling the isotopic composition of different plant compounds (e.g., evaporative effects in plant waxes vs cellulose) to better understand the environmental signatures contained within them. References Daley, T.J., Barber, K.E., Street-Perrott, F.A., Loader, N.J., Marshall, J.D., Crowley, S.F., Fisher, E.H., in press: Holocene climate variability revealed by oxygen isotope analysis of Sphagnum cellulose from Walton Moss, northern England, Quaternary Science Reviews, doi:10.1016/j.quascirev.2009.09.017. McClymont, E.L., Mauquoy, D., Yeloff, D., Broekens, P., van Geel, B., Charman, D.J., Pancost, R.D., Chambers, F.M. and Evershed, R.P., 2008: The disappearance of Sphagnum imbricatum from Butterburn Flow, UK, The Holocene, 18: 991-1002. Nichols, J., Booth, R.K., Jackson, S.T., Pendall, E.G. and Huang, Y., 2010: Differential hydrogen isotopic ratios of Sphagnum and vascular plant biomarkers in ombrotrophic peatlands as a quantitative proxy for precipitation--evaporation balance, Geochimica et Cosmochimica Acta, 74: 1407-1416. Pendall, E., Markgraf, V., White, J.W.C., Dreier, M. and Kenny, R., 2001: Multiproxy record of late Pleistocene-Holocene climate and vegetation changes from a peat bog in Patagonia, Quaternary Research, 55: 168-178. Skrzypek, G., Kaluzny, A., Wojtun, B. and Jedrysek, M.-O., 2007: The carbon stable isotopic composition of mosses: A record of temperature variation, Organic Geochemistry, 38: 1770-1781.