'Growth rings' in crustose lichens: comparison with directly measured growth rates and implications for lichenometry

R.A. Armstrong*, T. Bradwell

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Some species of crustose lichens, such as Ochrolechia parella (L.) Massal., exhibit concentric marginal rings, which may represent an alternative technique of measuring growth rates and potentially, a new lichenometric dating method. To examine this hypothesis, the agreement and correlation between ring widths and directly measured annual radial growth rates (RaGR, mm a<sup>-1</sup>) were studied in 24 thalli of O. parella in north Wales, UK, using digital photography and image analysis. Variation in ring width was observed at different locations around a thallus, between thalli, and from year to year. The best agreement and correlation between ring width and lichen growth rates was between mean width of the outer two rings (measured in 2011) and mean RaGR (in 2009/10). The O. parella data suggest that mean width of the youngest two growth rings, averaged over a sample of thalli, is a predictor of recent growth rates and therefore could be used in lichenometry. Potential applications include as a convenient method of comparing lichen growth rates on surfaces in different environmental settings; and as an alternative method of constructing lichen growth-rate curves, without having to revisit the same lichen thalli over many years. However, care is needed when using growth rings to estimate growth rates as: growth ring widths may not be stable; ring widths exhibit spatial and temporal variation; rings may not represent 1-year's growth in all thalli; and adjacent rings may not always represent successive year's growth.

Original languageEnglish
Pages (from-to)88-95
Number of pages8
JournalQuaternary Geochronology
Volume28
Early online date18 Apr 2015
DOIs
Publication statusPublished - Jun 2015

Fingerprint

lichenometry
lichen
dating method
photography
comparison
image analysis
temporal variation
spatial variation

Bibliographical note

© 2015, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/

Keywords

  • annual variation
  • lichenometry
  • marginal growth ring
  • ochrolechia parella (L.) massal
  • radial growth rate
  • RaGR

Cite this

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title = "'Growth rings' in crustose lichens: comparison with directly measured growth rates and implications for lichenometry",
abstract = "Some species of crustose lichens, such as Ochrolechia parella (L.) Massal., exhibit concentric marginal rings, which may represent an alternative technique of measuring growth rates and potentially, a new lichenometric dating method. To examine this hypothesis, the agreement and correlation between ring widths and directly measured annual radial growth rates (RaGR, mm a-1) were studied in 24 thalli of O. parella in north Wales, UK, using digital photography and image analysis. Variation in ring width was observed at different locations around a thallus, between thalli, and from year to year. The best agreement and correlation between ring width and lichen growth rates was between mean width of the outer two rings (measured in 2011) and mean RaGR (in 2009/10). The O. parella data suggest that mean width of the youngest two growth rings, averaged over a sample of thalli, is a predictor of recent growth rates and therefore could be used in lichenometry. Potential applications include as a convenient method of comparing lichen growth rates on surfaces in different environmental settings; and as an alternative method of constructing lichen growth-rate curves, without having to revisit the same lichen thalli over many years. However, care is needed when using growth rings to estimate growth rates as: growth ring widths may not be stable; ring widths exhibit spatial and temporal variation; rings may not represent 1-year's growth in all thalli; and adjacent rings may not always represent successive year's growth.",
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'Growth rings' in crustose lichens : comparison with directly measured growth rates and implications for lichenometry. / Armstrong, R.A.; Bradwell, T.

In: Quaternary Geochronology, Vol. 28, 06.2015, p. 88-95.

Research output: Contribution to journalArticle

TY - JOUR

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T2 - comparison with directly measured growth rates and implications for lichenometry

AU - Armstrong, R.A.

AU - Bradwell, T.

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