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 Post subject: Desert Varnish and Lichen
PostPosted: Fri Jan 16, 2009 1:45 am 
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Joshia,
Wayne P. Armstrong, Professor has a good article at:
http://www.desertusa.com/magdec97/varni ... rnish.html
I have lots of lichen and desert varnish images but it's late and if you are interested I can post another day.

For those that don't want to read the whole article I think it important to be aware of this part at least.
"Through the remarkable marriage between algae and fungi, lichens have etched out an existence in places where no other life forms could possibly live. Although they have survived millions of years of evolution, many lichen species are now endangered by atmospheric pollution. This same fate may also affect some of the desert varnish microbes. Since lichens absorb most of their mineral nutrients from the air and rain water, they are especially vulnerable to toxic air-borne pollutants.

Because they have no way to excrete the elements they absorb into their tissue, toxic compounds become even more concentrated. The toxins cause the photosynthetic algal cells to deteriorate and the subsequent death of the fungal spouse. Extensive off-road vehicle activity in some desert areas stirs up vast quantities of alkaline dust. This increased atmospheric alkalinity may affect manganese oxidation by varnish bacteria, thus slowing or inhibiting the development of desert varnish.

Like the proverbial canary used to detect invisible but deadly methane fumes in a coal mine, lichens are sensitive barometers of atmospheric pollution. In fact, their vulnerability has made them very effective air pollution monitoring stations for the U.S. Forest Service and National Park Service. Lichens and desert varnish are fascinating and complex living organisms. We still have a lot to learn from them. In addition, they coat our desert mountains with a myriad of beautiful colors."
Think about it,
Ed

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PostPosted: Fri Jan 16, 2009 11:29 am 
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Us humans have made a mess of things. I haven't read the whole article yet, just what you posted. I don't think there are enough people who care enough to help things out yet, but at least there are probably more due to the green movement.


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PostPosted: Fri Jan 16, 2009 11:31 am 
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I sincerely appreciate you taking the time to post this article for me. Very, very interesting. I have of course known about lichens, but until now, didn't know that desert varnish is actually an organic process! I would enjoy seeing some photos, but don't knock yourself out! ;)

Here are some tidbits from the article I found most fascinating:

Quote:
Desert varnish is a thin coating (patina) of manganese, iron and clays on the surface of sun-baked boulders. According to Ronald I. Dorn and Theodore M. Oberlander (Science Volume 213, 1981), desert varnish is formed by colonies of microscopic bacteria living on the rock surface for thousands of years.


Quote:
However, in varnish bacteria the electrons come from the oxidation of manganese and iron rather than glucose. Herein lies the marvelous adaptive advantage for producing a layer of black and red varnish on desert boulders.


Quote:
Varnish bacteria thrive on smooth rock surfaces in arid climates. According to Ronald Dorn, perhaps 10,000 years are required for a complete varnish coating to form in the deserts of the southwestern United States. In fact, dating of varnished surfaces is of enormous importance to the study of desert landforms and to the study of early humans in America, since many artifacts lying on the ground become coated with desert varnish.


Thanks again for posting Ed!


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PostPosted: Fri Jan 16, 2009 1:04 pm 
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Josiah,
You might be interested in the USGP site on Biological soil crusts that are being destroyed en mass by irresponsible ATV and 4X4 drivers. These are the life colonies that most likely were the first terrestrial life on Earth!!!!!
http://www.soilcrust.org/
Enjoy,
Ed

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"Look deep into nature, and then you will understand everything better."
Albert Einstein (1879-1955)
ArizonaEd--Tucson Cactus and Succulent Society-- www.tucsoncactus.org


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PostPosted: Fri Oct 29, 2010 12:43 am 
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In the natural environment, plants are constantly invading and colonizing new habitats--a phenomenon known as succession. Since lichens are among the first plants to colonize bare rock, they play an important role in primary succession.


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PostPosted: Fri Oct 29, 2010 10:26 am 
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G'Day MathewWilliams,
not meant to scare you away--and Welcome to the Forums. :D
I'm not exactly sure why you replied to this post and would be interested in your concern. That said, with tounge in cheek, there is a bit of misinformation IMHO that your plagerized portion of a paragraph states.
""In the natural environment, plants are constantly invading and colonizing new habitats--a phenomenon known as succession. Since lichens are among the first plants to colonize bare rock, they play an important role in primary succession."After lichens have etched and crumbled the rock surface for centuries, mineral soil and organic matter begins to accumulate. Then other plants such as mosses and grasses begin to grow, followed by herbs, hardy shrubs, and finally trees."
excerpt from DesertUSA
http://www.desertusa.com/magdec97/varnish/lichen.html

IMO DesertUSA is a fine site but not as accurate as it could be. There have been several times the information stated was in error.

In this instance, after an interesting explaination of lichen, the went on to say "Since lichens are among the first plants". Lichen are not plants!!! Lichen are a symbiotic relationship twixt a fungi and a photosynthetic partner either a green alga or cyanobacterium (usually). They do play a part in breaking down bare rock but modern thought is the amount of rock broken down is much less than had previosly been taught. The dead licken organism probably adds more humis for plants to "take root" than the acidic decompotition of rock per any given unit of lichen.

FYI:
An inertesting and understandable site for normal folk is:
http://www.lichen.com/biology.html
(pretty pictures too)


FOR a quick explaination of bare rock plant succession:
A brief except from:
Wardle, D. A., et al., Science, 23 July 2004

Primary Plant Succession
The process of plant succession begins just as soon as a land area capable of supporting plant life is formed. Some examples:
• accumulation of sand dunes at the edge of the ocean or a lake
• exposure of rock by a retreating glacier
• cooling of a lava flow
Bare rock succession in the temperate deciduous forest biome
• The first colonizers are lichens and certain mosses. Acids secreted by the lichens attack the rock and provide bits of soil. Additional soil particles may be formed by weathering or be blown in from elsewhere. Damage and decay to the lichens supplies some humus, and eventually enough soil is formed to support other mosses
• The growth, death, and decay of mosses produces more humus, and soon there is enough to support the growth of
• grasses and
• shrubby growth such as blueberries. These, in turn, provide the conditions for such sun-loving, fast-growing species as
• gray birch trees and poplars (quaking aspens).
• In time, white pines replace these. In the dense shade of mature white pines, only shade-tolerant maples and beech seedlings thrive.
When these large trees finally take over, the succession comes to an end. Maple and beech seedlings are able to develop under the conditions imposed by their parents, and the population becomes self-sustaining. It is known as a climax forest.

_________________
"Look deep into nature, and then you will understand everything better."
Albert Einstein (1879-1955)
ArizonaEd--Tucson Cactus and Succulent Society-- www.tucsoncactus.org


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PostPosted: Mon Sep 09, 2013 1:43 am 
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The body of most lichens is different from those of either the fungus or alga growing separately. The fungus surrounds the algal cells, often enclosing them within complex fungal tissues unique to lichen associations.


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