| 1. |
- Haussmann, Natalie, et al.
(författare)
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10Be application to soil development on Marion Island, southern Indian Ocean
- 2010
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 268:7-8, s. 1058-1061
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Tidskriftsartikel (refereegranskat)abstract
- Marion Island, located in the southern Indian Ocean, constitutes the summit of an active shield volcano. It is a small terrestrial environment where glacially abraded bedrock became exposed c × 10 kyr ago. These conditions provide an interesting possibility for the assessment of 10Be accumulation rates and their application to soil erosion studies on the island. 10Be concentrations were measured in precipitation, soil profiles and an Azorella selago cushion plant. The data reveal a 10Be precipitation flux several times higher than model prediction. Estimation of the 10Be accumulation based on the soil inventory suggests a span between 2000 and 7000 yr. This time span is not in accordance with the accepted notion that the island was covered with ice about 10,000 yr ago and suggests either removal of 10Be from the soil profile, an overestimated Holocene 10Be-flux or a delayed soil development history. Our results provide new data on 10Be concentrations from the sub-Antarctic islands and contribute towards enlarging the southern-hemisphere 10Be database.
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| 2. |
- Haussmann, Natalie, et al.
(författare)
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Contrasting nurse plants and nurse rocks The spatial distribution of seedlings of two sub-Antarctic species : The spatial distribution of seedlings of two sub-Antarctic species
- 2010
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Ingår i: Acta Oecologica. - : Elsevier BV. - 1146-609X .- 1873-6238. ; 36:3, s. 299-305
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Tidskriftsartikel (refereegranskat)abstract
- Positive plant interactions, such as those associated with nurse plants, have been suggested to dominate over negative interactions in environments with high abiotic stress. Here we demonstrate that the sub-Antarctic cushion plant species, Azorella selago (Apiaceae), positively affects the distribution of both its own seedlings and those of the perennial grass, Agrostis magellanica (Poaceae). As a result of the light weight and small size of seeds of both species, coupled with strong winds experienced in the study area, we consider it unlikely that these patterns are the result of very localized seed dispersal from the study cushions themselves. Instead, we suggest that both cushions and rocks act as seed traps, trapping seeds dispersed by wind, runoff and/or downslope sediment transport through frost creep. In addition, increased A. selago seedling numbers around cushions, but not around rocks, suggest that cushions provide a biological nurse effect, such as improving soil nutrient status or providing mychorrizae, to seedlings of their own kind.
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| 3. |
- Haussmann, Natalie, et al.
(författare)
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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
- 2009
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Ingår i: Geografiska Annaler. Series A, Physical Geography. - : Informa UK Limited. - 0435-3676 .- 1468-0459. ; 91:4, s. 257-268
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Haussmann, Natalie, et al.
(författare)
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Interactions between a cushion plant (Azorella selago) and surface sediment transport on sub-Antarctic Marion Island
- 2009
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Ingår i: Geomorphology. - : Elsevier BV. - 0169-555X .- 1872-695X. ; 107:3-4, s. 139-148
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- le Roux, Peter C., et al.
(författare)
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Spatial Association of Lemming Burrows with Landforms in the Swedish Subarctic Mountains : Implications for Periglacial Feature Stability
- 2011
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Ingår i: Arctic, Antarctic and Alpine research. - : Swedish Society for Anthropology and Geography. - 1523-0430 .- 1938-4246. ; 43:2, s. 223-228
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Tidskriftsartikel (refereegranskat)abstract
- Burrowing mammals often have considerable geomorphological impacts, and their tunneling activities may decrease the stability of landforms. We document the spatial distribution of Norwegian lemming burrows in a subarctic alpine meadow to determine the preferred locations for burrow entrances and to examine the potential for burrowing to decrease the stability of periglacial landforms at the site. Burrow entrances were disproportionately common into the base and sides of landforms (>68% of burrows), probably reflecting the lower energetic cost of moving soil horizontally, rather than vertically, out of burrows. Most burrow entrances (>60%) were also located under large rocks, which probably improve burrow stability by providing a firm ceiling to the entrance. Field observations show that these burrows are relatively stable, as only 3% were associated with any signs of increased erosion or landform instability. Therefore, in contrast to some previous studies, and despite burrowing being concentrated on landforms, we suggest that these rodents have little direct impact on landform integrity at this site.
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| 6. |
- Nel, Werner, et al.
(författare)
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Earth science research on Marion Island (1996-2020) : a synthesis and new findings
- 2021
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Ingår i: The South African Geographical Journal. - : Informa UK Limited. - 0373-6245 .- 2151-2418. ; 103:1, s. 22-42
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Tidskriftsartikel (refereegranskat)abstract
- Marion Island is a peak of a shield volcano located in the southern Indian Ocean. The island is strategically important for the collection of climatological data and marine and terrestrial research in a vast, oceanic region of the globe. This paper reviews the series of earth science programmes on Marion Island over the last 25 years, provides a synthesis of the research outcomes and demonstrates how field and laboratory methods have developed over time. Marion Island has, globally, one of the most active soil frost environments in a distinctive periglacial setting and understanding this contemporary periglacial environment has been a key objective of the research programmes. Geomorphological processes have important implications for local ecosystem functioning and define the regional and global significance for diurnal soil frost environments and climate change. Keeping abreast with the advancements of appropriate methodologies and technologies and the continued employment of a mix of new and established methods has driven the earth science research in this unique island environment. A series of short vignettes present the most recent advancements on old key questions and indicate that new techniques continuously challenge us to re-evaluate the most basic of assumptions that exist within our research.
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