Within-site variation in lichen growth rates and its implications for direct lichenometry

Armstrong, Richard A. Within-site variation in lichen growth rates and its implications for direct lichenometry. Geografiska Annaler: Series A, 96 (2), pp. 217-226.


Variation in lichen growth rates poses a significant challenge for the application of direct lichenometry, i.e. the construction of lichen dating curves from direct measurement of growth rates. To examine the magnitude and possible causes of within-site growth variation, radial growth rates (RaGRs) of thalli of the fast-growing foliose lichen Melanelia fuliginosa ssp. fuliginosa (Fr. ex Duby) Essl. and the slow-growing crustose lichen Rhizocarpon geographicum (L.) DC. were studied on two S-facing slate rock surfaces in north Wales, UK using digital photography and an image analysis system (Image-J). RaGRs of M. fuliginosa ssp. fuliginosa varied from 0.44 to 2.63 mmyr-1 and R. geographicum from 0.10 to 1.50 mmyr-1.5. Analysis of variance suggested no significant variation in RaGRs with vertical or horizontal location on the rock, thallus diameter, aspect, slope, light intensity, rock porosity, rock surface texture, distance to nearest lichen neighbour or distance to vegetation on the rock surface. The frequency distribution of RaGR did not deviate from a normal distribution. It was concluded that despite considerable growth rate variation in both species studied, growth curves could be constructed with sufficient precision to be useful for direct lichenometry.

Publication DOI: https://doi.org/10.1111/geoa.12043
Divisions: Life & Health Sciences > Optometry
Life & Health Sciences > Ophthalmic Research Group
Life & Health Sciences > Health Sciences
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Uncontrolled Keywords: direct lichenometry,growth variation,melanelia fuliginosa ssp. fuliginosa (Fr. ex Duby) Essl.,normal distribution,radial growth rate (RaGR),rhizocarpon geographicum (L.) DC.,Geology,Geography, Planning and Development


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