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Interactions between a cushion plant (Azorella selago) and surface sediment transport on sub-Antarctic Marion Island
Department of Conservation Ecology and Entomology, Stellenbosch University, South Africa.
DST-NRF Centre for Invasion Biology and Cape Research Centre, South African National Parks.
Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Social and Economic Geography.
2009 (English)In: Geomorphology, ISSN 0169-555X, Vol. 107, no 3-4, 139-148 p.Article in journal (Refereed) Published
Abstract [en]

On sub-Antarctic Marion Island cushions of the dominant vascular plant species, Azorella selago, interact with the geomorphology of fellfield landscapes by affecting sediment distribution and ultimately terrace formation. Here, to understand the consequences of Azorella cushions for substrate movement and sorting, we quantified the size and shape of Azorella cushions and the grain size distribution of sediment surrounding these cushions, using a combination of image analysis approaches. Results show that as cushions become larger, they tend to become more elongated and grow more perpendicular to the slope. Mean and variance of grain size were greater upslope of Azorella cushions, while the number of particles was higher downslope of cushions, although these differences were not significant at all sites studied. Differences between upslope and downslope particle sizes were, however, not related to cushion elongation or growth angle as had been expected. The observed sediment partitioning is likely caused by a combination of frost-related sediment transport and Azorella cushions acting as sediment obstructions. Understanding these interactions between Azorella cushions and the landscape is especially important in the light of recent warming and drying on the island, as particle size affects soil properties such as water-holding capacity and frost susceptibility.

Place, publisher, year, edition, pages
2009. Vol. 107, no 3-4, 139-148 p.
Keyword [en]
Particle sorting; Azorella selago; Terrace formation; Needle ice; Sub-Antarctic
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-108838DOI: 10.1016/j.geomorph.2008.12.002OAI: oai:DiVA.org:uu-108838DiVA: diva2:240932
Available from: 2009-09-30 Created: 2009-09-30 Last updated: 2011-12-22Bibliographically approved

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Boelhouwers, Jan
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