Techniques in Lichenometry: Identifying the Yellow Rhizocarpons

Benedict, James B.

doi:10.2307/1551260

Cited by 40 publications

(36 citation statements)

References 13 publications

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“…Specific age of the test sites (Table 1) was determined based on following sources of information: (i) lichenometric dating of test sites 1-6 (in AD 2011), based on: (a) measurements of enveloping circles of two hundred sixty relatively circular thalli of the Rhizocarpon subgenus (Benedict 1988), (b) a method of mean of five largest thalli (5LL), (c) a changing growth rate of 0.725 mm year −1 for lichens youn− ger than fifty five years and a rate of 0.585 mm year −1 for older thalli (Thompson and Jones 1986), and (d) a colonisation lag time of ten years; (ii) lichenometric dates pro− vided by Gordon and Sharp (1983) and Evans et al (1999); (iii) historical data pub− lished by Ahlman and Thorarinsson (1937) and Thorarinsson (1943); (iv) glacio− logical measurements of glacier recession along the profile J158 available in the da− tabase of the Icelandic Glaciological Society (Sigurđsson 1998) and performed an− nually in years AD 1930-1995; the measurements were correlated with the position of the glacier snout as shown on aerial photographs taken in AD 1954 and1969; author's own assessment of the most recent position of the glacier snout, based on analysis of aerial photographs, Google Earth imagery and field inspection. Collected data regarding micro−roughness, Schmidt hammer and weathering rind thickness were subject to statistical tests using Statistica 10.0 software.…”

Section: Methodsmentioning

confidence: 99%

Rock surface micro−roughness, Schmidt hammer rebound and weathering rind thickness within LIA Skálafellsjökull foreland, SE Iceland

Dąbski¹

2014

Polish Polar Research

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Glacially abraded basaltic rock surfaces found within a Little Ice Age (LIA) fore− land of Skálafellsjökull (SE Iceland) were studied at eight sites of different age applying different weathering indices. They include surface micro−roughness parameters measured with the Handysurf E35−B electronic profilometer -a new tool in geomorphology, Schmidt hammer rebound (R−values) and weathering rind thickness. Values of these indices ob− tained from study sites exposed to subaerial weathering for more than ca. 80 years are sig− nificantly different than those from younger moraines closer to the glacier snout. Despite a wide scatter of readings within each study site, there is a significant correlation between the ages and the values of the indices. It is concluded that the micro−roughness parameters pro− vided by the Handysurf E35−B profilometer, Schmidt hammer R−values and weathering rind thickness are robust indices of rock surface deterioration rate in short time−scales. There is mounting evidence that rock surface undergoes relatively rapid weathering during first decades since deglaciation.

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Section: Methodsmentioning

confidence: 99%

Rock surface micro−roughness, Schmidt hammer rebound and weathering rind thickness within LIA Skálafellsjökull foreland, SE Iceland

Dąbski¹

2014

Polish Polar Research

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“…This subgenus is subdivided into four sections, viz., Superficiale, Alpicola, Viridiatrum and Rhizocarpon (Poelt, 1988). Thalli can be identified to section level fairly easily using the identification criteria suggested by Benedict (1988). Hence, all thalli included in the study were identified as Rhizocarpon section Rhizocarpon (L.) DC., i.e., spores were greater than two-celled, the epihymenium was not black, and the medulla was intense blue/violet when treated with a 1% solution of iodine (Benedict, 1988).…”

Section: Taxonomy Of Rhizocarponmentioning

confidence: 99%

Carbohydrates in the hypothallus and areolae of the crustose lichen Rhizocarpon geographicum (L.) DC.

Armstrong

Smith

2009

Symbiosis

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Carbohydrates in the hypothallus and areolae of the crustose lichen Rhizocarpon geographicum (L.) DC. AbstractCarbohydrate concentrations in the marginal hypothallus and areolae of the crustose lichen Rhizocarpon geographicum (L.) DC. were measured in north Wales, U.K. using gas chromatography. Ribitol, arabitol, and mannitol were the most abundant carbohydrates while α-glucose β-glucose, fructose, sucrose, and trehalose were present in smaller amounts. The concentrations of arabitol, ribitol, mannitol, fructose, and α-glucose were greater in the areolae while the concentration of trehalose was greater in the hypothallus. Concentrations of carbohydrates varied little between sample days. Concentrations of polyols in the hypothallus were not correlated with those in the areolae. These results suggest: 1) the hypothallus has a lower demand for carbohydrates than the areolae or there is limited transport from areolae to hypothallus, 2) increased trehalose in the non-lichenised hypothallus may be an adaptation to withstand stress and desiccation, and 3) polyols are partitioned differently in the hypothallus and areolae.

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“…Furthermore, each thalli was examined to ensure that it did not comprise two or more intergrown individuals. Identification marks were made with white oil-based paint and Rotring pen, several millimetres away from the edge of the thallus margin (as done by Benedict, 1988;McCarthy, 2003). Each lichen was numbered -GIG01 to GIG41.…”

Section: Non-competing Approximately Circular Rhizocarpon Section Rmentioning

confidence: 99%

Growth rates of Rhizocarpon geographicum lichens: a review with new data from Iceland

Bradwell

Armstrong

2006

J Quaternary Science

100

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This article reviews evidence from previous growth-rate studies on lichens of the yellowgreen species of Subgenus Rhizocarpon -the family most commonly used in lichenometric growth-rate curve is parabolic and is best described by a third-order polynomial function.The striking similarity between these findings in Iceland and those of Armstrong (1983) in Wales implies that the shape of the growth-rate curve may be characteristic of Rhizocarpon geographicum lichens. The difference between the absolute growth rate in southern Iceland and Wales (c. 66% faster) is probably a function of climate and micro-environment between the two sites. These findings have implications for previous lichenometric-dating studies;namely, that those studies which assume constant lichen growth rates over many decades are probably unreliable.

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Techniques in Lichenometry: Identifying the Yellow Rhizocarpons

Cited by 40 publications

References 13 publications

Rock surface micro−roughness, Schmidt hammer rebound and weathering rind thickness within LIA Skálafellsjökull foreland, SE Iceland

Rock surface micro−roughness, Schmidt hammer rebound and weathering rind thickness within LIA Skálafellsjökull foreland, SE Iceland

Carbohydrates in the hypothallus and areolae of the crustose lichen Rhizocarpon geographicum (L.) DC.

Growth rates of Rhizocarpon geographicum lichens: a review with new data from Iceland

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