| 1. |
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| 2. |
- Graae, Bente J., et al.
(författare)
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An experimental evaluation of the arctic fox (Alopex lagopus) as a seed disperser
- 2004
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Ingår i: Arctic, Antarctic and Alpine Research. - 1938-4246 .- 1523-0430. ; 36:4, s. 468-473
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Tidskriftsartikel (refereegranskat)abstract
- Arctic foxes are evaluated as seed dispersal vectors for Greenlandic plant species through a feeding experiment with subsequent scat analysis and germination test. Seeds of 22 common species with different morphology were tested. Passage time ranged between 4 and 48 hours. No significant differences was detected in passage time for seeds with different morphology. Cerastium alpinum and Stellaria longipes had higher germination after passage through the fox’ digestive tract as compared to controls. Sibbaldia procumbens, Oxyria digyna and Silene acaulis were favoured by passage when shorter than 10 hours. Salix glauca ssp. callicarpaea, Veronica alpina, Gnaphalium norvegicum, Papaver radicatum, Ranunculus hyperboreus, Chamaenerion latifolium, Luzula parviflora and bulbils of Polygonum viviparum and Saxifraga cernua were inhibited by passage, whereas the remaining species had too low germination percentage to allow for evaluation. Species with adaptations to wind dispersal seemed particularly vulnerable to gut pasage. Arctic foxes are able to provide long-distances dispersal of seeds lacking morphological adaptations to dispersal, but for most species seeds need to be defecated within 12 hours to remain viable.
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| 3. |
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| 4. |
- Jansson, Peter, et al.
(författare)
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Spatial and Temporal Characteristics of a Long Mass Balance Record, Storglaciären, Sweden
- 2007
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Ingår i: Arctic, Antarctic and Alpine research. - 1523-0430 .- 1938-4246. ; 39:3, s. 432-437
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Tidskriftsartikel (refereegranskat)abstract
- Glacier fluctuations constitute an important indicator for climate change, both current and past. Glacier mass balance measurements are made to correctly reflect the state of the glacier. Very few studies have been made to study the representability of each point measurement to the average mass balance of a particular glacier, an exercise that requires a large number of measurements. Such studies are rare due to the practical constraints and costs involved in collecting data. On Storglaciären, Sweden, a very dense system of measurements of both distributed winter (~100 points km-2) and summer (~15 points km-2) balance allows a spatial analysis of the mass balance components. The results show that local summer balance values are strongly correlated to the average summer balance value of the glacier. Local winter balance values are also generally well correlated to the average winter balance value, but small areas on the glacier exhibit no correlation. These areas correspond to wind-eroded areas of low accumulation on the glacier. The local net balance values are also well correlated to the average net balance value, indicating that the effect of the summer balance is strong and, at least partly, counter-balancing the spatial inhomogeneities in the local spatial winter balance values. These results show that detailed knowledge of both mass balance components and their spatial variability may be necessary to safely use a sparse system of measurements points. On Storglaciären, this is especially true for winter balance measurements since the spatial snow distribution is highly variable and not necessarily representative of the glacier average at each measurement point. The results strictly apply to Storglaciären but similar effects should be present on most glaciers in a similar setting; the results thus serve as an example of conditions that can be expected on a typical mid-latitude to subarctic glacier.
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| 5. |
- Kullman, Leif
(författare)
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Thermophilic tree species reinvade subalpine Sweden - Early responses to anomalous late holocene climate warming
- 2008
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Ingår i: Arctic, Antarctic and Alpine research. - : BioOne. - 1523-0430 .- 1938-4246. ; 40:1, s. 104-110
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Tidskriftsartikel (refereegranskat)abstract
- Consistent with general predictions and earlier empirical studies, it appears that recent climate warming has started to affect large-scale biogeographical patterns in northern Sweden. Long-term, systematic monitoring in permanent altitudinal belt transects reveals spread of broadleaved thermophilic tree species with quite different life histories into the subalpine forest belt. Saplings of Quercus robur, Ulmus glabra, Acer platanoides, Alnus glutinosa, and Betula pendula have responded to altered climatic conditions by jump-dispersal in the order of 50-300 km northwards and 500-800 m upwards. Thereby, they have reinvaded elevations where they grew during the warmest phase of the Holocene, 9500-8000 years ago, but were subsequently extirpated by Neoglacial cooling. Confined to the past 15 years or so, these unique observations are consistent with background climatic data, i.e. warming of all seasons. The results contribute to more realistic vegetation models by stressing that at least certain plant species are able to track climate warming without substantial migration lag.
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| 6. |
- Lindgren, Åsa, et al.
(författare)
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The impact of disturbance and seed availability on germination in alpine vegetation in the Scandinavian mountains
- 2007
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Ingår i: Arctic, Antarctic and Alpine research. - Colorado : Institute of Arctic and Alpine Research, University of Colorado. - 1523-0430 .- 1938-4246. ; 39:3, s. 449-454
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Tidskriftsartikel (refereegranskat)abstract
- The availability of seeds and microsites are limiting factors for many plant species of different vegetation types. We have investigated the existence of such limitations in two habitats, an alpine heath and a subalpine birch forest, where abiotic factors are hypothesized to be the main determining factor of plant species distributions. Both habitats are characterized by a short growing season and cold temperatures, and the alpine heath is also constrained by low productivity. A seed addition experiment including six vascular plants, selected by different functional traits and occurrence, showed that seed limitation was an important factor in these habitats. Removal of the aboveground biomass (controlled disturbance) increased germination only for some species. The effect of reindeer presence was found to be of less importance, probably due to low and varying densities of reindeer. To conclude, we found that seed limitation was the most important factor limiting the distribution of our studied species in the two alpine environments.
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| 7. |
- Moen, Jon, et al.
(författare)
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High species turnover and decreasing plant species richness on mountain summits in Sweden : reindeer grazing overrides climate change?
- 2008
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Ingår i: Arctic, Antarctic and Alpine research. - Boulder, Colo. : University of Colorado. - 1523-0430 .- 1938-4246. ; 40:2, s. 382-395
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Tidskriftsartikel (refereegranskat)abstract
- We investigated changes in vascular plant species richness in nine summit floras in the central part of the Fennoscandian mountain range compared to historical data from 1950. We revisited the summits (defined as the top 50 altitudinal meters of each mountain) in 2002, and recorded all species. The changes in species richness were tested against both species and mountain characteristics. Species richness had declined on eight of the nine summits. Five of the species were new since the 1950s, while 17 species were lost from the summits. However, species turnover was even higher: 57 of our recorded species occurrences had established on at least one mountain since the 1950s, while we could not find 132 of the recorded occurrences in 1950 on one or more mountains. Temperature had increased since 1950 by about 1 oC and precipitation by 12%. The reindeer population has more than doubled. No correlations between plant responses, plant characteristics, and mountain characteristics were found, suggesting individualistic and mountain-specific responses. We conclude that climate changes may be responsible for an increased establishment and reindeer trampling for increased mortality of established individuals. However, the net result is a decline in species richness.
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| 8. |
- Sjögersten, Sofie, et al.
(författare)
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Depth distribution of net methanotrophic activity at a mountain birch forest-tundra heath ecotone, northern Sweden
- 2007
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Ingår i: Arctic, Antarctic and Alpine research. - 1523-0430 .- 1938-4246. ; 39:3, s. 477-480
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Tidskriftsartikel (refereegranskat)abstract
- Methanotrophy (the bacterial oxidation of CH4) in soils is the major biological sink for atmospheric CH4. Here we present results from a study designed to quantify the role of the physical diffusion barrier to CH4, through surface soils, as a factor affecting methanotrophy. We used the mountain birch forest-tundra heath ecotone in subarctic northern Sweden as our study system. Our results show that, although CH4 fluxes were generally low (around -20 mu mol m(-2) h(-1); a net flux from atmosphere to soil), the two adjacent communities responded in contrasting ways to in situ experimental reduction of the diffusion barrier (removal of the top 50 mm of soil): Uptake increased by 40% in forest soil in association with the removal, whereas it decreased marginally (by 10%) in tundra heath. Investigations of the depth-distribution of CH4 oxidation in vitro revealed maximum rates at the top of the mineral soil for the forest site, whereas at the tundra heath this was more evenly spread throughout the organic horizon. The contrasting physicochemical properties and methanotroph activity in the organic horizons together explain the contrasting responses to the removal treatment. They also illustrate the potential role of vegetation for methane oxidation around this ecotone, exerted through its influence on the depth and properties of the organic horizons in these subarctic soils.
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| 9. |
- Beylich, A. A., et al.
(författare)
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Rates of chemical and mechanical fluvial denudation in an arctic oceanic periglacial environment, latnjavagge drainage basin, northernmost Swedish Lapland
- 2005
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Ingår i: Arctic Antarctic and Alpine Research. - 1523-0430 .- 1938-4246. ; 37:1, s. 75-87
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Tidskriftsartikel (refereegranskat)abstract
- A process geomorphological investigation was started in 1999 to study present denudation rates and the mutual relationship of chemical and mechanical fluvial denudation in periglacial environments. Latnjavagge (9 km(2); 950-1440 in a.s.l.; 68° 20'N, 18° 30'E) was chosen as a representative drainage basin of the arctic-oceanic mountain area in northernmost Swedish Lapland. Atmospheric solute inputs, chemical denudation, and mechanical fluvial denudation were analyzed. During the arctic summer field seasons of 2000, 2001, and 2002 measurements of daily precipitation, solute concentrations in precipitation, and in melted snow cores, taken before snowmelt, were recorded. In addition, solute and suspended sediment concentrations in creeks were analyzed, and bedload tracer movements were registered during the entire summer seasons (end of May until beginning of September). Results show a mean annual chemical denudation net rate of 5.4 t km(-2) yr(-1) in the entire catchment. Chemical denudation in Latnjavagge is less than one third of chemical denudation rates reported for Karkevagge (Swedish Lapland) but seems to be at a similar level as in a number of other subarctic, arctic, and alpine environments. Mechanical fluvial denudation is lower than chemical denudation. Most sediment transport in channels occurs in the early summer season during a few days with snowmelt generated runoff peaks. The main sediment sources in the drainage basin are mobilized channel bed pavements exposing fines, ice patches/fields, and material mobilized by slush flows. The calculated mean mechanical fluvial denudation rate is 2.3 t km(-2) yr(-1) at the inlet of lake Latnjajaure, situated in Latnjavagge close to the outlet of the valley. A very stable vegetation cover and rhyzosphere in this environment mainly explain the low value. The mean mechanical fluvial denudation rate at the outlet of the entire Latnjavagge drainage basin, below lake Latnjajaure, is only 0.8 t km(-2) yr(-1). Both chemical and mechanical fluvial denudation show low intensity. The results from Latnjavagge support the contention that chemical denudation is a somewhat important denudational process in periglacial environments.
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| 10. |
- Olofsson, Johan
(författare)
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Positive and negative plant-plant interactions in two contrasting arctic-alpine plant communities
- 2004
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Ingår i: Arctic, Antarctic and Alpine research. - 1523-0430 .- 1938-4246. ; 36:4, s. 464-467
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Tidskriftsartikel (refereegranskat)abstract
- Positive interactions in alpine plant communities have been reported to increase in importance with increasing altitude and exposure. Positive and negative interactions between plants might occur simultaneously, so the net plant-plant interaction is determined by the balance between positive and negative effects. I investigated the relative effect of facilitation and resource competition by surrounding dwarf shrubs on Carex bigelowii in two contrasting arctic-alpine tundra heathlands. Carex bigelowii was positively associated with dwarf shrubs on an exposed mountain ridge but negatively associated with dwarf shrubs on a protected heath. A removal experiment indicated that positive associations at the exposed site are the result of facilitation of C. bigelowii by the dwarf shrub canopy. Our understanding of arctic and alpine plant communities can be enhanced by regarding plant interactions as combinations of positive and negative components.
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