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The Life Cycle and Life Span of Namibian Fairy Circles

In Namibia of southwestern Africa, the sparse grasslands that develop on deep sandy soils under rainfall between 50 and 100 mm per annum are punctuated by thousands of quasi-circular bare spots, usually surrounded by a ring of taller grass. The causes of these so-called “fairy circles” are unknown,...

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Autor principal: Tschinkel, Walter R.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2012
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3384657/
https://www.ncbi.nlm.nih.gov/pubmed/22761663
http://dx.doi.org/10.1371/journal.pone.0038056
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author Tschinkel, Walter R.
author_facet Tschinkel, Walter R.
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description In Namibia of southwestern Africa, the sparse grasslands that develop on deep sandy soils under rainfall between 50 and 100 mm per annum are punctuated by thousands of quasi-circular bare spots, usually surrounded by a ring of taller grass. The causes of these so-called “fairy circles” are unknown, although a number of hypotheses have been proposed. This paper provides a more complete description of the variation in size, density and attributes of fairy circles in a range of soil types and situations. Circles are not permanent; their vegetative and physical attributes allow them to be arranged into a life history sequence in which circles appear (birth), develop (mature) and become revegetated (die). Occasionally, they also enlarge. The appearance and disappearance of circles was confirmed from satellite images taken 4 years apart (2004, 2008). The frequency of births and deaths as a fraction of the total population of circles allowed the calculation of an approximate turnover rate, and from this, an estimate of circle lifespan. Lifespan appeared to vary with circle size, with small circles averaging about 24 years, and larger ones 43–75 years. Overall lifespan averaged about 41 yr. A second, independent estimate of lifespan was made by revisiting circles 2 to 9 years after their clear status had been confirmed. This resulted in a lifespan estimate of about 60 years. Any causal explanation of fairy circles must include their birth, development and death, their mean lifespan and the variation of their features under different conditions.
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spelling pubmed-33846572012-07-03 The Life Cycle and Life Span of Namibian Fairy Circles Tschinkel, Walter R. PLoS One Research Article In Namibia of southwestern Africa, the sparse grasslands that develop on deep sandy soils under rainfall between 50 and 100 mm per annum are punctuated by thousands of quasi-circular bare spots, usually surrounded by a ring of taller grass. The causes of these so-called “fairy circles” are unknown, although a number of hypotheses have been proposed. This paper provides a more complete description of the variation in size, density and attributes of fairy circles in a range of soil types and situations. Circles are not permanent; their vegetative and physical attributes allow them to be arranged into a life history sequence in which circles appear (birth), develop (mature) and become revegetated (die). Occasionally, they also enlarge. The appearance and disappearance of circles was confirmed from satellite images taken 4 years apart (2004, 2008). The frequency of births and deaths as a fraction of the total population of circles allowed the calculation of an approximate turnover rate, and from this, an estimate of circle lifespan. Lifespan appeared to vary with circle size, with small circles averaging about 24 years, and larger ones 43–75 years. Overall lifespan averaged about 41 yr. A second, independent estimate of lifespan was made by revisiting circles 2 to 9 years after their clear status had been confirmed. This resulted in a lifespan estimate of about 60 years. Any causal explanation of fairy circles must include their birth, development and death, their mean lifespan and the variation of their features under different conditions. Public Library of Science 2012-06-27 /pmc/articles/PMC3384657/ /pubmed/22761663 http://dx.doi.org/10.1371/journal.pone.0038056 Text en Walter R. Tschinkel. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Tschinkel, Walter R.
The Life Cycle and Life Span of Namibian Fairy Circles
title The Life Cycle and Life Span of Namibian Fairy Circles
title_full The Life Cycle and Life Span of Namibian Fairy Circles
title_fullStr The Life Cycle and Life Span of Namibian Fairy Circles
title_full_unstemmed The Life Cycle and Life Span of Namibian Fairy Circles
title_short The Life Cycle and Life Span of Namibian Fairy Circles
title_sort life cycle and life span of namibian fairy circles
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3384657/
https://www.ncbi.nlm.nih.gov/pubmed/22761663
http://dx.doi.org/10.1371/journal.pone.0038056
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