Radial growth of Rhizocarpon section Rhizocarpon lichen thalli over six years at snoqualmie pass in the Cascade Range, Washington State

Armstrong, Richard A. (2005). Radial growth of Rhizocarpon section Rhizocarpon lichen thalli over six years at snoqualmie pass in the Cascade Range, Washington State. Arctic Antarctic and Alpine research, 37 (4), pp. 411-415.

Abstract

This article describes a 6-yr study of the radial growth rates (RGR, mm yr-1) of Rhizocarpon section Rhizocarpon thalli on a talus slope at Snoqualmie Pass in the Cascade Range, Washington State, United States (47°27'N; 121°26'W). At the end of the growth period, 32 of a total of 39 thalli had exhibited a positive RGR, and 7 of a total of 39 thalli showed no measurable growth. Mean RGR of all thalli was 0.07 mm yr-1 (range, 0-0.19 mm, SD = 0.06). Analysis of variance suggested no significant variation in RGR in successive growth periods, but significant differences were present both within and between thalli. The slope of a boulder facet did not influence RGR, but growth was affected by aspect, the least growth being observed on north-northwest facets. A plot of RGR against thallus diameter revealed a wide scatter of data points with little evidence for a significant change in growth with thallus size. Hence, the study showed that the RGR of Rhizocarpon thalli at Snoqualmie is extremely slow and highly variable and significantly less than estimates based on lichenometry. To determine the growth curve of a yellow-green Rhizocarpon by direct measurement at such a site would require a large sample of thalli and careful standardization of the species studied, the aspect conditions under which the thalli were measured, and the initial hypothallus width of the thalli. © 2005 Regents of the University of Colorado.

Publication DOI: https://doi.org/10.1657/1523-0430(2005)037[0411:RGORSR]2.0.CO;2
Divisions: Life & Health Sciences > Optometry
Life & Health Sciences > Ophthalmic Research Group
Life & Health Sciences
Additional Information: © 2005 Regents of the University of Colorado. This is an Open Access article . Radial Growth of Rhizocarpon Section Rhizocarpon Lichen Thalli over Six Years at Snoqualmie Pass in the Cascade Range, Washington State Author: R. A. Armstrong
Uncontrolled Keywords: radial growth rates,rhizocarpon section,rhizocarpon thalli,talus slope,Environmental Science(all),Environmental Chemistry
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Related URLs: http://www.scopus.com/inward/record.url?scp=28844459347&partnerID=8YFLogxK (Scopus URL)
http://www.bioone.org/doi/abs/10.1657/1523-0430%282005%29037%5B0411%3ARGORSR%5D2.0.CO%3B2 (Publisher URL)
Published Date: 2005-11
Authors: Armstrong, Richard A. ( 0000-0002-5046-3199)

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