Are Namibian "fairy circles" the consequence of self-organizing spatial vegetation patterning

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dc.contributor.authorCramer, Michael Den_ZA
dc.contributor.authorBarger, Nichole Nen_ZA
dc.date.accessioned2015-11-18T07:12:56Z
dc.date.available2015-11-18T07:12:56Z
dc.date.issued2013en_ZA
dc.description.abstractCauses of over-dispersed barren "fairy circles" that are often surrounded by ca. 0.5 m tall peripheral grasses in a matrix of shorter ( ca. 0.2 m tall) grasses in Namibian grasslands remain mysterious. It was hypothesized that the fairy circles are the consequence of self-organizing spatial vegetation patterning arising from resource competition and facilitation. We examined the edaphic properties of fairy circles and variation in fairy circle size, density and landscape occupancy (% land surface) with edaphic properties and water availability at a local scale (<50 km) and with climate and vegetation characteristics at a regional scale. Soil moisture in the barren fairy circles declines from the center towards the periphery and is inversely correlated with soil organic carbon, possibly indicating that the peripheral grass roots access soil moisture that persists into the dry season within fairy circles. Fairy circle landscape occupancy is negatively correlated with precipitation and soil [N], consistent with fairy circles being the product of resource-competition. Regional fairy circle presence/absence is highly predictable using an empirical model that includes narrow ranges of vegetation biomass, precipitation and temperature seasonality as predictor variables, indicating that fairy circles are likely a climate-dependent emergent phenomenon. This dependence of fairy circle occurrence on climate explains why fairy circles in some locations may appear and disappear over time. Fairy circles are only over-dispersed at high landscape occupancies, indicating that inter-circle competition may determine their spacing. We conclude that fairy circles are likely to be an emergent arid-grassland phenomenon that forms as a consequence of peripheral grass resource-competition and that the consequent barren circle may provide a resource-reservoir essential for the survival of the larger peripheral grasses and provides a habitat for fossicking fauna.en_ZA
dc.identifier.apacitationCramer, M. D., & Barger, N. N. (2013). Are Namibian "fairy circles" the consequence of self-organizing spatial vegetation patterning. <i>PLoS One</i>, http://hdl.handle.net/11427/15152en_ZA
dc.identifier.chicagocitationCramer, Michael D, and Nichole N Barger "Are Namibian "fairy circles" the consequence of self-organizing spatial vegetation patterning." <i>PLoS One</i> (2013) http://hdl.handle.net/11427/15152en_ZA
dc.identifier.citationCramer, M. D., & Barger, N. N. (2013). Are Namibian ‘‘fairy circles’’ the consequence of self-organizing spatial vegetation patterning. PloS one, 8(8), e70876. doi:10.1371/journal.pone.0070876en_ZA
dc.identifier.ris TY - Journal Article AU - Cramer, Michael D AU - Barger, Nichole N AB - Causes of over-dispersed barren "fairy circles" that are often surrounded by ca. 0.5 m tall peripheral grasses in a matrix of shorter ( ca. 0.2 m tall) grasses in Namibian grasslands remain mysterious. It was hypothesized that the fairy circles are the consequence of self-organizing spatial vegetation patterning arising from resource competition and facilitation. We examined the edaphic properties of fairy circles and variation in fairy circle size, density and landscape occupancy (% land surface) with edaphic properties and water availability at a local scale (<50 km) and with climate and vegetation characteristics at a regional scale. Soil moisture in the barren fairy circles declines from the center towards the periphery and is inversely correlated with soil organic carbon, possibly indicating that the peripheral grass roots access soil moisture that persists into the dry season within fairy circles. Fairy circle landscape occupancy is negatively correlated with precipitation and soil [N], consistent with fairy circles being the product of resource-competition. Regional fairy circle presence/absence is highly predictable using an empirical model that includes narrow ranges of vegetation biomass, precipitation and temperature seasonality as predictor variables, indicating that fairy circles are likely a climate-dependent emergent phenomenon. This dependence of fairy circle occurrence on climate explains why fairy circles in some locations may appear and disappear over time. Fairy circles are only over-dispersed at high landscape occupancies, indicating that inter-circle competition may determine their spacing. We conclude that fairy circles are likely to be an emergent arid-grassland phenomenon that forms as a consequence of peripheral grass resource-competition and that the consequent barren circle may provide a resource-reservoir essential for the survival of the larger peripheral grasses and provides a habitat for fossicking fauna. DA - 2013 DB - OpenUCT DO - 10.1371/journal.pone.0070876 DP - University of Cape Town J1 - PLoS One LK - https://open.uct.ac.za PB - University of Cape Town PY - 2013 T1 - Are Namibian "fairy circles" the consequence of self-organizing spatial vegetation patterning TI - Are Namibian "fairy circles" the consequence of self-organizing spatial vegetation patterning UR - http://hdl.handle.net/11427/15152 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/15152
dc.identifier.urihttp://dx.doi.org/10.1371/journal.pone.0070876
dc.identifier.vancouvercitationCramer MD, Barger NN. Are Namibian "fairy circles" the consequence of self-organizing spatial vegetation patterning. PLoS One. 2013; http://hdl.handle.net/11427/15152.en_ZA
dc.language.isoengen_ZA
dc.publisherPublic Library of Scienceen_ZA
dc.publisher.departmentDepartment of Biological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.rightsThis 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 credited.en_ZA
dc.rights.holder© 2013 Cramer, Bargeren_ZA
dc.rights.urihttp://creativecommons.org/licenses/by/4.0en_ZA
dc.sourcePLoS Oneen_ZA
dc.source.urihttp://journals.plos.org/plosoneen_ZA
dc.subject.otherGrassesen_ZA
dc.subject.otherTermitesen_ZA
dc.subject.otherWheaten_ZA
dc.subject.otherGrasslandsen_ZA
dc.subject.otherHabitatsen_ZA
dc.subject.otherPlant growth and developmenten_ZA
dc.subject.otherRainen_ZA
dc.subject.otherRoot growthen_ZA
dc.titleAre Namibian "fairy circles" the consequence of self-organizing spatial vegetation patterningen_ZA
dc.typeJournal Articleen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceArticleen_ZA
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