title: Carbon isotope discrimination in leaves of the broad-leaved paperbark tree, Melaleuca quinquenervia, as a tool for quantifying past tropical and subtropical rainfall.
abstract: Quantitative reconstructions of terrestrial climate are highly sought after but rare, particularly in Australia. Carbon isotope discrimination in plant leaves (Δleaf ) is an established indicator of past hydroclimate because the fractionation of carbon isotopes during photosynthesis is strongly influenced by water stress. Leaves of the evergreen tree Melaleuca quinquenervia have been recovered from the sediments of some perched lakes on North Stradbroke and Fraser Islands, south-east Queensland, eastern Australia. Here, we examine the potential for using M. quinquenervia ∆leaf as a tracer of past rainfall by analysing carbon isotope ratios (δ(13) C) of modern leaves. We firstly assess Δleaf variation at the leaf and stand scale and find no systematic pattern within leaves or between leaves due to their position on the tree. We then examine the relationships between climate and Δleaf for a 11-year time series of leaves collected in a litter tray. M. quinquenervia retains its leaves for 1-4 years; thus, cumulative average climate data are used. There is a significant relationship between annual mean ∆leaf and mean annual rainfall of the hydrological year for 1-4 years (i.e. 365-1460 days) prior to leaf fall (r(2)  = 0.64, P = 0.003, n = 11). This relationship is marginally improved by accounting for the effect of pCO2 on discrimination (r(2)  = 0.67, P = 0.002, n = 11). The correlation between rainfall and Δleaf , and the natural distribution of Melaleuca quinquenervia around wetlands of eastern Australia, Papua New Guinea and New Caledonia offers significant potential to infer past rainfall on a wide range of spatial and temporal scales.
authors.affiliation: Geography, Environment and Population, University of Adelaide, Adelaide, SA, Australia.|Sprigg Geobiology Centre, University of Adelaide, Adelaide, SA, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Tibby
authors.affiliation: Geography, Environment and Population, University of Adelaide, Adelaide, SA, Australia.|Sprigg Geobiology Centre, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Cameron
authors.initials: C
authors.lastname: Barr
authors.affiliation: Sprigg Geobiology Centre, University of Adelaide, Adelaide, SA, Australia.|Department of Earth Sciences, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Francesca A
authors.initials: FA
authors.lastname: McInerney
authors.affiliation: School of Geography, Politics & Sociology, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
authors.forename: Andrew C G
authors.initials: AC
authors.lastname: Henderson
authors.affiliation: NERC Isotope Geosciences Facilities, British Geological Survey, Keyworth Nottingham, NG12 5GG, UK.|Centre for Environmental Geochemistry, University of Nottingham, Nottingham, NG7 2RD, UK.
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Leng
authors.affiliation: Griffith School of Engineering, Environmental Engineering, Griffith University, Brisbane, QLD, Australia.
authors.forename: Margaret
authors.initials: M
authors.lastname: Greenway
authors.affiliation: Queensland Department of Science, Information Technology and Innovation, Brisbane, QLD, Australia.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Marshall
authors.affiliation: Queensland Department of Science, Information Technology and Innovation, Brisbane, QLD, Australia.
authors.forename: Glenn B
authors.initials: GB
authors.lastname: McGregor
authors.affiliation: Sprigg Geobiology Centre, University of Adelaide, Adelaide, SA, Australia.|Department of Earth Sciences, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Tyler
authors.affiliation: Queensland Department of Science, Information Technology and Innovation, Brisbane, QLD, Australia.
authors.forename: Vivienne
authors.initials: V
authors.lastname: McNeil
mesh_terms: D001315:Australia; D002244:Carbon; D002247:Carbon Isotopes; D031650:Melaleuca; D010219:Papua New Guinea; D018515:Plant Leaves; D011891:Rain
chemical_list: D002247:Carbon Isotopes; D002244:Carbon
keywords: CO
  2; Holocene; carbon isotope ratios; climate reconstruction; discrimination; palaeoclimate; wetlands