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

Abstract

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 elanelia fuliginosa ssp. fuliginosa (Fr. ex uby) ssl. and the slow‐growing crustose lichen hizocarpon geographicum (L.) DC. were studied on two ‐facing slate rock surfaces in north ales, using digital photography and an image analysis system (Image‐). of . fuliginosa ssp. fuliginosa varied from 0.44 to 2.63 mm yr^–1 and . geographicum from 0.10 to 1.50 mm yr^–1.5. Analysis of variance suggested no significant variation in 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 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.

Key words:

• direct lichenometry
• radial growth rate (RaGR)
• growth variation
• Melanelia fuliginosa ssp. fuliginosa (Fr. ex Duby) Essl.
• Rhizocarpon geographicum (L.) DC.
• normal distribution

Additional information

Notes on contributors

Richard A. Armstrong

Richard A. Armstrong, Vision Sciences, Aston University, Birmingham, B4 7ET, UK

Email: [email protected]