Wind and seed : a conceptual model of shape-formation in the cushion plant Azorella Selago

dc.contributor.authorCombrinck, Madeleine L.
dc.contributor.authorHarms, Thomas M.
dc.contributor.authorMcGeoch, Melodie A.
dc.contributor.authorSchoombie, Janine
dc.contributor.authorLe Roux, Peter Christiaan
dc.date.accessioned2021-04-20T12:36:39Z
dc.date.available2021-04-20T12:36:39Z
dc.date.issued2020-08
dc.description.abstractAIMS : The sub-Antarctic cushion plant, Azorella selago, is usually hemispherical when small but frequently crescent-shaped when larger. Spatial variation in wind speed and in air-borne seed and sediment deposition is examined to determine if wind scouring and deposition patterns could contribute to the development of nonhemispherical shapes in cushion plants. METHODS : Computational fluid dynamic analyses were conducted for hemispherical and crescent-shaped cushion plants parameterizing models with data from A. selago habitats on Marion Island. Numerical data were contextualized with field observations to arrive at a conceptual model for shape development. RESULTS : Airflow modelling showed that both wind scouring and seed deposition of the commonly cooccurring grass Agrostis magellanica are greater on the windward side of the plant. By contrast, heavier sediment particles are predominantly deposited on the leeward side of plants, leading to burial of lee-side A. selago stems. This sediment accumulation may initiate the development of the crescent-shape in hemispherical plants by increasing stem mortality on the plant’s leeward edge. Once developed, the crescent-shape is probably self-reinforcing because it generates greater air recirculation (and lower air velocities) which enhances further deposition and establishment of A. magellanica grasses in the lee of the crescent. The conceptual model consists therefore of three stages namely, (1) negligible air recirculation, (2) sediment deposition and grass establishment, and (3) differential cushion growth. CONCLUSION : This conceptual model of plant shape development may explain the occurrence and orientation of crescent-shaped cushion plants and highlights how predicted changes in wind patterns may affect vegetation patterns.en_ZA
dc.description.departmentPlant Production and Soil Scienceen_ZA
dc.description.librarianam2021en_ZA
dc.description.sponsorshipThe South African National Research Foundation (NRF), the South African National Antarctic Program and the DST-NRF Center of Excellence for Invasion Biology.en_ZA
dc.description.urihttp://link.springer.com/journal/11104en_ZA
dc.identifier.citationCombrinck, M.L., Harms, T.M., McGeoch, M.A. et al. Wind and seed: a conceptual model of shape-formation in the cushion plant Azorella Selago. Plant and Soil 455, 339–366 (2020). https://doi.org/10.1007/s11104-020-04665-3.en_ZA
dc.identifier.issn0032-079X (print)
dc.identifier.issn1573-5036 (online)
dc.identifier.other10.1007/s11104-020-04665-3
dc.identifier.urihttp://hdl.handle.net/2263/79523
dc.language.isoenen_ZA
dc.publisherSpringeren_ZA
dc.rights© The Author(s) 2020 This article is licensed under a Creative Commons Attribution 4.0 International License.en_ZA
dc.subjectAeolian processesen_ZA
dc.subjectAirflow modellingen_ZA
dc.subjectBurialen_ZA
dc.subjectComputational fluid dynamicsen_ZA
dc.subjectPositive feedbacken_ZA
dc.subjectShadingen_ZA
dc.subjectSub-Antarcticen_ZA
dc.subjectVegetation patterningen_ZA
dc.titleWind and seed : a conceptual model of shape-formation in the cushion plant Azorella Selagoen_ZA
dc.typeArticleen_ZA

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