| 1. |
- Ryberg, Martin, 1976, et al.
(author)
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Ectomycorrhizal Diversity on Dryas octopetala and Salix reticulata in an Alpine Cliff Ecosystem
- 2009
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In: Arctic, Antarctic, and Alpine Research. - : Informa UK Limited. - 1523-0430 .- 1938-4246. ; 41:4, s. 506-514
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Journal article (peer-reviewed)abstract
- The ectomycorrhizal communities in alpine habitats have been relatively little studied. As global change is predicted to have a large impact in Arctic and alpine environments, it is important to document the fungi of these climatic regions to monitor changes and to understand upcoming successions. This study investigates the ectomycorrhizal community of Dryas octopetala and Salix reticulata on cliff ledges in a mid-alpine setting using the internal transcribed spacer region of nuclear ribosomal DNA for the identification of the fungal component of ectomycorrhizal root tips. It is shown that the community is relatively species rich, with 74 molecular operational taxonomic units (MOTUs)/species, and that it is dominated by Cenococcum geophilum, Thelephoraceae spp., Cortinarius spp., and Sebacinales spp. Furthermore, the dominating species have low specificity regarding the tested hosts and seem likely to be able to facilitate the succession of the alpine tundra to subalpine forest by serving as mycorrhizal partners for establishing pioneer trees.
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| 2. |
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| 3. |
- Olofsson, Johan
(author)
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Effects of simulated reindeer grazing, trampling and waste products on nitrogen mineralization and production in a subarctic meadow
- 2009
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In: Arctic, Antarctic and Alpine research. - : Informa UK Limited. - 1523-0430 .- 1938-4246. ; 41:3, s. 330-338
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Journal article (peer-reviewed)abstract
- An experiment was conducted in arctic tundra to evaluate the role of reindeer grazing, trampling, and feces and urine deposition in nutrient turnover and primary production. Grazing was simulated by mowing, trampling by the impact of a wooden pole, and waste product deposition by the application of fertilizer. In the first year, aboveground primary production increased with simulated grazing in the fertilized plots and decreased with simulated grazing in the unfertilized plots; this indicates a higher regrowth capacity at higher nutrient levels. However, nitrogen mineralization and primary production were mainly determined by the input or removal of nutrients and, therefore, decreased in plots that were grazed but not fertilized and increased in plots that were fertilized but not grazed. Simulated trampling decreased the depth of the moss layer and increased soil temperatures, but the higher temperatures increased N mineralization only in unmowed plots, and the increased nitrogen availability was not translated into increased primary production. Since aboveground and belowground net primary production in plots with simulated grazing was the same as in plots without simulated animal activity, this study indicates that an entire trophic level can be supported with no apparent effect on primary production.
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| 4. |
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| 5. |
- Jansson, Peter, et al.
(author)
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Spatial and Temporal Characteristics of a Long Mass Balance Record, Storglaciären, Sweden
- 2007
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In: Arctic, Antarctic and Alpine research. - 1523-0430 .- 1938-4246. ; 39:3, s. 432-437
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Journal article (peer-reviewed)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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| 6. |
- Kullman, Leif
(author)
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Thermophilic tree species reinvade subalpine Sweden - Early responses to anomalous late holocene climate warming
- 2008
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In: Arctic, Antarctic and Alpine research. - : BioOne. - 1523-0430 .- 1938-4246. ; 40:1, s. 104-110
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Journal article (peer-reviewed)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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| 7. |
- Lindgren, Åsa, et al.
(author)
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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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In: 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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Journal article (peer-reviewed)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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| 8. |
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| 9. |
- Moen, Jon, et al.
(author)
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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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In: Arctic, Antarctic and Alpine research. - Boulder, Colo. : University of Colorado. - 1523-0430 .- 1938-4246. ; 40:2, s. 382-395
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Journal article (peer-reviewed)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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| 10. |
- Sjögersten, Sofie, et al.
(author)
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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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In: Arctic, Antarctic and Alpine research. - 1523-0430 .- 1938-4246. ; 39:3, s. 477-480
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Journal article (peer-reviewed)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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| 11. |
- Beylich, A. A., et al.
(author)
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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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In: Arctic Antarctic and Alpine Research. - 1523-0430 .- 1938-4246. ; 37:1, s. 75-87
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Journal article (peer-reviewed)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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| 12. |
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| 13. |
- Klingbjer, Per, et al.
(author)
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The thinning and retreat of Pårteglaciären, northern Sweden, during the twentieth century and its relation to climate
- 2006
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In: Arctic, Antarctic and Alpine Research. - 1523-0430. ; 38:1, s. 104-112
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Journal article (peer-reviewed)abstract
- Parteglaciaren in northern Sweden has a response time of similar to 200 years, demonstrating a long response time for a continentally located glacier. Paeteglaciaren is a polythermal valley glacier presently covering an area of 10 km(2). Its size will be reduced another 60-70% if the present climate persists and will then only have similar to 30% of its Little Ice Age maximum volume left. Future global warming will of course enhance melt rates, and the relative size and volume reduction will probably be even larger. Photogrammetric studies between 1963 and 1992 show a general thinning of the entire glacier except for the center one of the three cirques in the accumulation area, which seems to have a surface elevation in balance with present climate. Balanced flow studies performed using GPS and Ground Penetrating Radar at the outlet of the cirques gave negative values for two cirques and a positive value for the center cirque. The future Parteglaciaren will split up into three small glaciers, and only the center one will extend beyond its cirque.
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| 14. |
- Sørensen, P L, et al.
(author)
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Plant and microbial uptake and allocation of organic and inorganic nitrogen related to plant growth forms and soil conditions at two subarctic tundra types
- 2008
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In: Arctic, Antarctic and Alpine Research. - 1938-4246. ; 40:1, s. 171-180
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Journal article (peer-reviewed)abstract
- In order to follow the uptake and allocation of N in different plant functional types and microbes in two tundra ecosystems differing in nutrient availability, we performed a 15N-labeling experiment with three N forms and followed the partitioning of 15N label among plants, microorganisms and soil organic matter. At both sites the deciduous dwarf shrub Betula nana and the evergreen Empetrum hermaphroditum absorbed added 15N at rates in the order: NH4+ > NO3− > glycine, in contrast to the graminoid Carex species which took up added 15N at rates in the order NO3− > NH4+ > glycine. Carex transported a high proportion of 15N to aboveground parts, whereas the dwarf shrubs allocated most 15N to underground storage. Enhanced 13C in Betula nana roots represents the first field evidence of uptake of intact glycine by this important circumpolar plant. Plant and microbial uptake of label was complementary as plants took up more inorganic than organic N, while microbes preferred organic N. Microbes initially took up a large part of the added label, but over the following four weeks microbial 15N decreased by 50% and most 15N was recovered in soil organic matter, while a smaller but slowly increasing proportion was retained in plant biomass.
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