Letter abstract


Nature Geoscience 1, 592 - 596 (2008)
Published online: 31 August 2008 | doi:10.1038/ngeo278

Subject Categories: Atmospheric science | Biogeochemistry | Climate science | Palaeoclimate and palaeoceanography

Plant spore walls as a record of long-term changes in ultraviolet-B radiation

Barry H. Lomax1,7, Wesley T. Fraser2, Mark A. Sephton3, Terry V. Callaghan1,4, Stephen Self2, Michael Harfoot5, John A. Pyle5,6, Charles H. Wellman1 & David J. Beerling1

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Stratospheric ozone screens the Earth's surface from harmful ultraviolet-B radiation. Concentrations of stratospheric ozone are governed by a variety of natural and anthropogenic factors, including solar cycles1, volcanic aerosols2, ozone-depleting substances3 and climate change4. However, assessing this variability before instrumental records has proved difficult owing to the lack of a well-constrained proxy5. Here, we use microspectroscopy to analyse the chemical composition of herbarium samples of clubmoss (Lycophyta) spores originating from high- and low-latitude localities, where they were exposed to different ultraviolet-B histories. We show that the concentration of two ultraviolet-B-absorbing compounds in the walls of high-northern- and southern-latitude spores is strongly regulated by historical variations in ultraviolet-B radiation. Conversely, we find little change in the concentration of these compounds in spores originating from tropical Ecuador, where ultraviolet levels have remained relatively stable. Using spores from Greenland, we reconstruct past (1907–1993) changes in ozone concentration and ultraviolet-B flux; we reveal strong similarities between spore-wall reconstructions, and independent instrumental records6 and model results7. Our findings suggest that ultraviolet-B-absorbing compounds in plant spore walls have the potential to act as a proxy for past changes in terrestrial ultraviolet-B radiation and stratospheric ozone. The chemical signature of plant spore walls in herbaria, and possibly also in sedimentary and ice-core archives, may therefore prove valuable for reconstructing past variations in stratospheric ozone and their connections with changes in solar radiation and climate.

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  1. Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
  2. Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
  3. Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
  4. Abisko Scientific Research Station, SE-981 07 Abisko, Sweden
  5. Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge CB1 1EW, UK
  6. National Centre for Atmospheric Science, Global Composition, University of Cambridge, Cambridge CB2 1EW, UK
  7. Present address: The School of Biosciences, Division of Agricultural and Environmental Sciences, The University of Nottingham, Nottingham NG72RD, UK

Correspondence to: Barry H. Lomax1,7 e-mail: b.lomax@sheffield.ac.uk, e-mail: barry.lomax@nottingham.ac.uk



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