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Fine scale variability in soil frost dynamics surrounding cushions of the dominant vascular plant species (Azorella selago) on sub-Antarctic Marion island
Department of Conservation Ecology and Entomology, Stellenbosch University, South Africa.
Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Social and Economic Geography.
DST-NRF Centre for Invasion Biology and Cape Research Centre, South African National Parks, Steenberg, South Africa.
2009 (English)In: Geografiska Annaler, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 91, no 4, 257-268 p.Article in journal (Refereed) Published
Abstract [en]

Through changing soil thermal regimes, soil moisture and affecting weathering and erosion processes plants can have an important effect on the physical properties and structure of soils. Such physical soil changes can in turn lead to biological facilitation, such as vegetation-banked terrace formation or differential seedling establishment. We studied the fine scale variability in soil temperature and moisture parameters, specifically focusing on frost cycle characteristics around cushions of the dominant, vascular plant species, Azorella selago, on sub-Antarctic Marion Island. The frost season was characterised by numerous low intensity and very shallow frost cycles. Soils on eastern cushion sides were found to have lower mean and maximum temperatures in winterthan soils on western cushion sides. In addition, lower variability in temperature was found on eastern cushion sides in winterthan on western cushion sides, probably as a result of higher wind speeds on western cushion sides and/or eastern, lee-side snow accumulation. Despite the mild frost climate, extensive frost heave occurred in the study area, indicating that needle ice forms at temperatures above −2°C. Our results demonstrate the effectiveness of frost pull as a heave mechanism under shallow frost conditions. The results highlight the importance of Azorella cushions in modifying site microclimates and of understanding the consequences of these modifications, such as potentially providing microhabitats. Such potential microhabitats are particularly important in light of current climate change trends on the island, as continued warming and drying will undoubtedly increase the need for thermal and moisture refugia.

Place, publisher, year, edition, pages
2009. Vol. 91, no 4, 257-268 p.
Keyword [en]
Cushion plant, Frost heave, Microclimate, Sub-Antartic
National Category
Biological Sciences
URN: urn:nbn:se:uu:diva-109265DOI: 10.1111/j.1468-0459.2009.00368.xISI: 000272836700003OAI: oai:DiVA.org:uu-109265DiVA: diva2:271784
Available from: 2009-10-13 Created: 2009-10-13 Last updated: 2011-12-20Bibliographically approved

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Boelhouwers, Jan
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