Why Like Lichens

The term lichenometry refers to a calibrated-age dating technique attempting to provide minimum dating of rock surfaces using measurements of lichen thallus size or other indices of lichen growth. The use of lichens in the dating of archaeological remains was initially proposed by Renaud in Spain. Developed by Austrian Roland Beschel half a century ago, and first applied in the European Alps Beschel , , this dating technique has been widely used in estimating the ages of recent geomorphic exposures, particularly glacial moraines Worsley Its use in archaeology has rarely been explored Benedict , ; Bettinger and Oglesby ; Broadbent ; Broadbent and Bergqvist ; Follmann a, b; Laundon ; Winchester , and aside from myself, no rock art researcher has sought to apply lichenometry to rock art. I investigated its use in the age estimation of relatively recent Austrian Alpine petroglyphs in , but later neglected to develop my experience further. The extensive literature of geomorphic applications of the technique conveys the impression that the applicability of this method is limited to subpolar or alpine conditions, i. This is not the case. Although in favourable cases the method has been suggested to be effective to years BP and possibly even beyond Miller and Andrews , it is commonly only precise up to or so years Innes In geomorphological terms this makes it particularly useful for recent glacial deposits.

Lichen colonization of recent moraines on Livingston Island (South Shetland I., Antarctica)

Abstract Certain species of crustose lichens have concentrically zoned margins which probably represent yearly growth rings. These marginal growth rings offer an alternative method of studying annual growth fluctuations, establishing growth rate—size curves, and determining the age of thalli for certain crustose species. Hence, marginal growth rings represent a potentially valuable, unexploited, tool in lichenometry.

Deficiencies of earthquake-lichenometry studies include inability to measure amounts of coseismic slip, possible lack of suitable slow growing crustose lichens in a.

A major limitation in rock art studies is that rock art can be difficult to date. The dating techniques currently in use fall into two broad categories: relative dating and absolute dating. Relative dating techniques include observations of patterns of chemical and physical weathering , evidence that art has been painted over, stylistic patterns, and variations in the spatial patterns of rock art indicating chronological sequences of site occupation. Absolute dating methods include analyses based on subjects depicted e.

Occasionally, it has been possible to date rock art directly by chemically analyzing the organic materials that were used to draw it, for example, charcoal, plant fibers, and protein binders. A major problem with this approach, however, is that the sampling procedure damages the rock art to a certain extent. Dating technologies include standard radiocarbon dating, cation ratio analysis based on separate rates of leaching for the chemical constituents of desert varnishes , amino acid racemisation based on the decomposition rates of amino acids , optically stimulated luminescence based on the length of time that quartz grains have been removed from sunlight , lichenometry based on lichen growth rates , and micro-erosion analyses based on weathering patterns.

Lichenometry – a natural dating device

This paper proposes a review of the use of lichenometry in Iceland since , using different techniques to solve the chronology of geomorphic processes. Based on the results of over 35 published studies, lichenometry has been widely applied in Iceland, proposing numerical ages absolute dating and relative ages relative dating of different surfaces. Increasing awareness of methodological limitations of the technique, together with more sophisticated data processing, has led some authors to claim that lichenometric ‘ages’ are robust and reliable.

However, the different measurement techniques used make it difficult to compare regions or studies in the same area. These problems are exacerbated in Iceland by rapid environmental changes across short distances and more generally by lichen species mis-identification in the field. Moreover, the reliability of lichenometric dates is discredited by their lack of correspondence with tephrochronologic data, whatever the lichenometric method used.

Determination of colonization time, great-growth phase, and especially uniform phase rates of lichen growth are essential for dating regional landslide events.

There is no need to fear these organisms as they very seldom to never cause any detriment to the trees they inhabit. Often living on the north side of trees and other surfaces avoiding heat and thriving on the more moist locations , lichens are naturally occurring and can be quite attractive. An excellent way to tell direction if you are lost in the woods!

Biologically speaking, lichens are a symbiotic, specifically mutualistic, relationship between a member of sac or club fungi and either green algae, cyanobacterium or sometimes brown algae. The mutualism they share begins with the fungi creating an environment for the algae to live, including moisture retention and a substrate to grow. The algae, in return, produce carbohydrates from photosynthesis which the fungi can consume. What you see on a tree, rock or fence are most often the vegetative structures called thalli plural of thallus and look like a scaly mat.

Sometimes the reproductive structures called apothecia are noticeable. Lichens can be flat, but are usually three-dimensional and layered, sometimes having structures looking like balloons or like fingers. One can identify specific lichens based on their growth patterns. Lichens have inhabited every corner of the earth.

So long as they have a surface on which to form, time to grow and very, very clean air, they do well. Interestingly, lichens are a bellwether for air pollution. If you see lichens growing on trees, it usually means that your air quality is high.

Dating Landslides with Lichen

Lichens are important as indicators of pollution because they readily absorb heavy metals into their tissues, mopping up elements like lead and cadmium. Lead was formerly present in appreciable quantities in gasoline. In Britain, it was practical to assay the damage done to the environment by mapping lichen species; most are unable to tolerate lead pollution for long, but those that can proliferate at the expense of others.

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Different coloured lichens on a rock surface. WE often read about Carbon 14 dating of human remains in archaeological sites, which are uncovered when excavating to lay the foundations for high rise buildings in inner city areas abroad. This method of dating is based upon the rate of decay of radioactive isotopes. World War 2 intervened and so it took until until an Austrian, Roland Beschel, published a paper on the dating of rocks since glacial times in the Austrian Alps.

This method of dating is known as lichenometry, using the rate of lichen growth on bare rock or stone surfaces to determine the length of time they have been exposed to the elements. This dating is based on a measured calibrated rate of specific lichen growth, taking the average radial measurement from the centre of the lichen to its extremities. The speed at which lichens grow is dependent on the climate, the rock type to which the lichen may anchor itself, and to the amount of atmospheric pollution.

Thus, lichens are reliable indicators of climate change and air pollution levels. Preserved on rock faces for 11, years, lichen growth is now considered a very accurate of climate changes over the last 1, years.

Lichen as a Dating Tool

Margot Brunn, Museum Conservator at the Provincial Museum of Alberta has asked me to reply to a question about the removal of lichens on lithic artifacts. As the museum’s curator of Botany I have worked with the Archaeological Survey of Alberta in using lichens to date stone features and as a cryptogamic plant specialist have developed some familiarity with lichens. There are a number of issues to consider here including lichen biology, the nature of the lithic feature, microclimates and the reasons one would want to remove the lichens.

Relevant Lichen biology Lichens are composed of algae and fungi. The fungi give the lichens their shape and the lichens attach themselves to the stone surface by the fungal hyphae.

Post date: Oct 9, Lichen on wooden bench. It’s true. The blue-gray and green growth, often seen on the sides of trees and other places like rocks and If you see lichens growing on trees, it usually means that your air quality is high.

Recent moraines constitute a worthwhile opportunity for studies concerning plant colonization, especially when the date of origin of the moraine is known. The moraine studied, roughly 34 years old, was in an early stage of plant succession. Plant communities were observed only on the boulders at the top of the moraine. They were always composed of a relatively small number of lichen species and with a low coverage of the rock surface. It is noteworthy that all lichen species observed lack asexual propagula and most of them are considered as being nitrophilous or ornithocoprophilous.

In many cases, a close relation between the boulder size and the measured variables specimen diameter, coverage, and number of species has been noted, with maximum values for the biggest boulders. The hypothetical biological implications of the boulder size and the causes of the interspecific differences observed in the average diameter of lichens are discussed. This is a preview of subscription content, log in to check access.

Rent this article via DeepDyve. Armstrong RA Studies on the growth rates of lichens. Academic Press London, pp —

Date with a Lichen

Lichens are an extremely successful partnership between a fungus and an alga. Lichens present a very intriguing problem for people whose job is to name different kinds of organisms. This is because a lichen is not a separate organism in the sense of being one type of individual. It is actually a close partnership between a fungus and an alga. Algae are very simple plants. The two types of organisms in the partnership are so closely interwoven that they appear as a single individual.

Because of low radial growth rates and considerable longev. Lichenometric dating (lichenometry) involves the use of lichen measurements to.

Two Canadian biologists are proposing a better way to assess the conservation value of old-growth forests in North America — using lichens, sensitive bioindicators of environmental change. Yolanda Wiersma, landscape ecologist at Memorial University of Newfoundland, propose their lichen-focussed system in a paper published today in the Ecological Society of America journal, Frontiers in Ecology and the Environment. How do we decide what to protect and what to cut? Lichens are part of the answer.

Old-growth forests, especially those in North America, are perceived to be rich in biodiversity, in addition to capturing aesthetic and spiritual values. These forests are usually defined by the age of the trees, with conservation and management practices developed accordingly. McMullin and Wiersma say this is an over-simplification, as it overlooks the importance of biodiversity in those habitats.

The approach of the researchers lets them look at the presence of forests in the context of the broader landscape. Our approach lets us identify which patch has been a forest for the longest period of time, even if it’s not the one with the oldest trees. McMullin and Wiersma argue that old trees are only a proxy for biodiversity in old-forest ecosystems and that biodiversity should be measured directly — with lichens as the ideal candidates.

Many old-growth forests have high sustained moisture and a high number of microhabitats suitable for certain species, which can’t disperse easily. Having these forests in the landscape provides a refuge for the seeds and spores that helps with the continued preservation of this biodiversity. In their paper, McMullin and Wiersma propose that suites of lichens associated with known old-growth areas can be used to develop “an index of ecological continuity” for forests of interest.

Lichen, BSc Botanty by Dr. Ruby Singh Parmar, Assistant Professor, Biyani girls College


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