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- Antonsson, Henrik, 1976, et al.
(författare)
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Nurse plant effect of the cushion plant Silene acaulis (L.) Jacq. in an alpine environment in the subarctic Scandes, Sweden
- 2009
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Ingår i: Plant Ecology & Diversity. - : Informa UK Limited. - 1755-0874 .- 1755-1668. ; 2:1, s. 17-25
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Tidskriftsartikel (refereegranskat)abstract
- Background: Facilitation plays important roles in the structuring of plant communities and several studies have found that it tends to increase with environmental severity in alpine plant communities. In addition, cushion plants have been shown to act as nurse plants, moderating extreme environmental conditions, and providing resources for other species, with substantial effects on local plant diversity. Aims: This study addresses the nurse plant effects of Silene acaulis – a common, circumpolar alpine plant species with a compact cushion-forming growth form – along an altitude transect in the mid- to high-alpine zones in northern Sweden. Methods: The numbers of species in paired S. acaulis cushions and identical-sized control plots along an altitude transect between 1150 m and 1450 m above sea level were compared, and differences in species composition were analysed. Results: At altitudes above c. 1280 m, but not at lower altitudes, more species were found inside the cushions than in their paired control plots. Species composition was similar inside cushions and in control plots. Conclusions: Our results suggest that S. acaulis acts as a nurse plant at altitudes higher than a certain threshold (c. 1280 m at the investigated site). It appears to play an important role in creating focal points for local vascular plant diversity in highalpine environments, where vegetation is open and occurs in small patches. Keywords: facilitation; plant-to-plant interactions; Silene acaulis; species richness; stress
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| 4. |
- Beylich, A. A., et al.
(författare)
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Intensity and spatio-temporal variability of fluvial sediment transfers in an Arctic-oceanic periglacial environment in northernmost Swedish Lapland (Latnjavagge catchment)
- 2006
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Ingår i: Geomorphology. - : Elsevier BV. - 0169-555X. ; 80:1-2, s. 114-130
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Tidskriftsartikel (refereegranskat)abstract
- Intensity and spatio-temporal variability of fluvial sediment transfers and mechanical fluvial denudation were analyzed in the periglacial Latnjavagge catchment (9 km(2); 950-1440 m a.s.l.; 68.20N, 18.30E) in Arctic-oceanic northernmost Swedish Lapland. The present-day rates of fluvial sediment transfer are low. The mean annual mechanical fluvial denudation rate at the inlet of lake Latnjajaure, as calculated after five years of process monitoring (2000-2004), and excluding a "rare rainfall event" which caused 3.2 times higher suspended sediment transport during one day as compared to the total mean annual suspended sediment transport, is 2.3 t km(-2) yr(-1). In years without "rare rainfall events", most of the total annual sediment load is transported in a. few days during annual snowmelt runoff. In the calculation of longer-term sediment budgets, rare rainfall events like the July 20th-21 st, 2004 event have to be considered as essential components. Reliable estimation of the recurrence intervals of such events is problematic. The pattern of ice patches and snow fields within the valley, the steepness of streams and channels and the location of areas showing slushflow activity are the major factors,controlling spatial variability of mechanical fluvial denudation in the drainage basin. The five lakes in Latnjavagge, especially lake Latnjajaure, are significant sediment traps and ground below 1300 m a.s.l. is protected by a very stable and closed vegetation cover and rhizosphere across the entire lower catchment. (c) 2006 Elsevier B.V. All rights reserved.
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| 5. |
- 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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| 7. |
- Björk, Robert G., 1974, et al.
(författare)
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A Climate Change aspect on root dynamics and nitrogen partitioning in a tundra landscape
- 2005
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Ingår i: Sediment budgets and rates of sediment transfer across cold environments in Europe. 3rd Workshop of the ESF Network SEDIFLUX, Durham, UK, 15 – 19 December 2005..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Arctic Climate Impact Assessment (ACIA) recently reported that Arctic is rapidly changing due to Climate Change. Likewise, the mountains of Europe are going to experience large shifts in plant composition and 41-56% of the alpine species might be on the edge of extinction according to the 1st synthesis of the Global Observation Research Initiative in Alpine Environments (GLORIA). Although the tundra ecosystems are subjected to dramatical changes as a result of Climate Change, there is little knowledge of the effect on root dynamics and its implication on the nitrifying and denitrifying microbial community. Here, we compare nitrification enzyme activity (NEA) and denitrification enzyme activity (DEA) rates along an altitudinal gradient with the effects of climatic warming using Open Top Chambers (OTCs) in consideration with root dynamics and architecture. This study was conducted at Latnjajaure Field Station (LFS) located in the midalpine region in northern Sweden. LFS is the Swedish field site for the International Tundra Experiment (ITEX), established in 1993. This gives an opportunity to investigate long-term effects of climatic warming by OTCs and an altitudinal gradient (1000m to 1365m), both within a very small geographical range. The OTCs used at LFS increases the soil surface temperature by approximately 1.5ºC whereas air temperatures normally falls with 0.6ºC with every hundred meter of increased altitude. To analyse the NEA and DEA we used an anaerobic incubation technique, based on acetylene inhibition technique, resulting in N2O as the only end product, which then were analysed by gas chromatography. Soil cores were additionally sampled in the OTCs to study the effects of climatic warming on the root system. The specific root length, root length density and root biomass were determined for the different root fractions. The results from NEA and DEA contradict each other. The gradient study show decreased NEA and DEA rates with falling altitude, whereas the warming experiment show a slight non significant increase due to the temperature enhancement by OTCs. The preliminary results from the root sampling indicate that there is a plant community specific response in root architecture, which has an output on root biomass and particularly in the fraction of fine roots, although, climatic warming did not have any significant affect on the root biomass. The fact that altitudinal temperature decline did not reduce NEA and DEA rates might in part be explained of the variables measured here, although they are not conclusive.
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| 8. |
- Björk, Robert G., 1974, et al.
(författare)
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Can present melt-out patterns identify snowbed plant species vulnerable to climate change?
- 2005
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Ingår i: Second International Conference on Arctic Research Planning – ICARP II, Copenhagen, Denmark, 10 – 12 November 2005..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Snowbeds form in topographic depressions which accumulate high amounts of snow during the winter months and the final snowmelt does not occur until late in the growing season. Many species preferentially grow in snowbed habitats and some of these are even limited to habitats in which winter snow accumulates. In connection with the Global Warming forecast, snowbed ecosystems of alpine Europe are regarded as particularly vulnerable in IPCC’s 2001 assessment report. This study is running at Latnjajaure Field Station, in northern Swedish Lapland, where four snowbed plant communi¬ties are studied. The snowbeds are of the “moderate type”, which means that they are melting out before the end of July, and they are situated in both heath and meadow sites. In this study we try to identify vulnerable plant species by the use of snow dynamics and plant community structure. Snowbed plant communi¬ties have high abundances of bryophytes along with high bryophyte diversity, 55 identified bryophytes within the snowbeds. The dominant bryophytes (e.g. Kiaeria stakei, Polytrichastrum sexangulare, Sanionia nivalis, Anthelia juratzkana, Scapania obcordata) are also snowbed specialist. The preliminary results show that earlier melt-out day will increase the vascular plant cover by 0.8 percent per day as well as increase in lichen cover by 0.5 percent per day. Bryophytes will suffer the most by decreasing in abundance by 1.7 percent per day of earlier melt-out day. Although, the response among bryophyte species is not uniform with Kiaeria stakei having the large decrease followed by Anthelia juratzkana, whereas Polytrichastrum sexangulare does not respond at all. There is also interaction among bryophyte species.
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| 9. |
- Björk, Robert G., 1974, et al.
(författare)
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Ecology of Alpine Snowbeds and the Impact of Global Change
- 2007
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Ingår i: Arctic, Antarctic, and Alpine Research. ; 39:1
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Recension (övrigt vetenskapligt/konstnärligt)abstract
- The ecosystems of alpine snowbed habitats are reviewed with emphasis on ecosystem functioning and capability to adapt to current and predicted global change. Snowbeds form in topographic depressions that accumulate large amounts of snow during the winter months, and the final snowmelt does not occur until late in the growing season. Many species preferentially grow in snowbed habitats and some of these are even restricted to these habitats. In this review we identify several ecosystem services which snowbeds provide to the alpine landscape. For instance, snowbeds provide a steady water and nutrient supply to adjacent plant communities and offer newly emerged high-quality food for herbivores late in the growing season. We also propose that alpine snowbeds are much more productive than earlier thought, especially when the very short growing season and often high grazing pressure are taken fully into account. Furthermore, we propose that bryophytes and graminoids (grasses, sedges, and rushes) probably will be most negatively impacted by global change, and the snowbed plant communities will be invaded by species from adjacent plant communities, especially by shrubs and boreal species. As snowbed plants have special growth conditions, their sensitivity and ability to respond rapidly to changes in annual snowfall patterns make snowbed communities particularly vulnerable in a warmer climate, and thereby sensitive indicators of global change
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| 10. |
- Björk, Robert G., 1974, et al.
(författare)
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ITEX at Latnjajaure
- 2007
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Ingår i: The 14th ITEX workshop, Falls Creek, Victoria, Australia, 2–6 February 2007..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- ITEX and ITEX-related research at Latnjajaure in northern Swedish Lapland has been quite diverse during the past few years, with most emphasis at the ecosystem and landscape scales. The basic warming experiment with open-top chambers and control plots is still running in a variety of ecosystems since 1993. During 2006, a re-inventory of OTCs and controls in Eriophorum vaginatum (cottongrass) dominated tussock tundra at the outlet of the lake showed significant changes since the last point-framing in 1995, not only in the OTCs but also in the control plots. No species were lost but dominance relationships among species had changed dramatically. The underlying permafrost had degraded substantially; it was continuous here in the early 1990ies but could not be detected in 2006. Already in 2003, a geo-radar transect showed no indication of remaining permafrost at the site (Else Kohlstrup et al., Uppsala University). The ecosystem had undergone a clear desiccation, and formerly water-filled boulder pits were now invaded by moss-dominated pioneer vegetation. The cottongrass tussocks had become less dense and more "fluffy" and had gradually been invaded by lingonberry (Vaccinium vitis-idaea), the most expansive species in the community. The effect size was about twice as high in OTCs as in controls. The cottongrass tussock tundra is one of a handful of vegetation types pointed out as particularly sensitive to Climate Change, based on the listing in IPCC's Third Assessment Report 2001. Our team is undertaking a longer-term project including four of these systems, i.e., snowbeds, tussock tundra, high alpine fellfields, and mesic alpine heath (being invaded by mountain birch). A helicopter inventory of possible sites for tussock tundra in the region in August 2005 revealed a total stock of ca 2 km2 in Sweden (compared with the circum-arctic total of 336,000 km2). As a further outcome of the project on indicator ecosystems, new project, Alpine Cliff Ecology (ACE) was initiated at Latnjajaure in 2006 (see separate presentation). In the snowbed project, initiated in 2002, four snowbed plant communi¬ties are studied. The snowbeds are of the “moderate" class (melting out before the end of July), and they are situated in both heath and meadow sites. Our current studies encompass plant community scale to landscape scale, and include, e.g., monitoring of snow dynamics, microbial and plant community structure in fertilized and control plots, lemming population dynamics, nitrogen and debris deposition, and soil processes (for microbial studies see separate abstract/presentation). Interestingly, our preliminary data suggests that the plant community structure does not change due to fertilization. In 2004 we sampled the OTCs, established in 1993, in dry meadow and dry heath for root morphology characteristics, root biomass distribution, and microbial activity. This study shows that tundra plants may respond to climate change by increasing their specific root length (SRL; m gDM-1) and specific root area (SRA; m2 kgDM -1), whilst the microbial activity may remain unaffected. Furthermore, this study suggests that there might be incorporation of C in tundra soils partly as a result of increased turnover of the finer roots produced within the OTCs. However, the response across plant communities is not consistent. The "Meeting of Litters" experiment headed by Hans Cornelissen, Vrije Universiteit Amsterdam (Holland) was finalized in 2004, with a multi-authored paper in review at present. The project focused on comparative decomposition studies on litter samples from a large number of ITEX sites gathered at two experimental outdoor facilities in Sweden: Latnjajaure (mid alpine) and Abisko (sub-alpine). Other international within-ITEX activities at Latnja include a field research campaign by Catharine Copass Thompson and Carrie McCalley from the Marine Biological Laboratory, Woods Hole, and Robert Bell and Kerry Dinsmore from the University of Edinburgh. They visited the Latnjajaure Field Station between August 2 and August 9, 2004. Their research in the Abisko area entailed linking measurements of carbon fluxes to the Normalized Difference Vegetation Index (NDVI), an index of greenness which can be measured on multiple scales, including from satellites. The goal for the 2004 summer was to cover as many different kinds of vegetation types in the region as possible, given the constraints of their sampling protocol. The up-scaling to the landscape level was manifested by the final publication of the GIS-based vegetation map over the Latnjajaure catchment (12 km2, 1 m2 pixel resolution) by Lindblad et al. (Pirineos 161: 3-32, 2006). This work is part of Karin Lindblad's Ph.D. thesis for her dissertation 26 January 2007.
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