| 1. |
- Almered Olsson, Gunilla, 1951, et al.
(författare)
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Variation in Life History Traits of Gentiana nivalis (Gentianaceae) in Alpine and Sub-alpine Habitats in the Norwegian Mountains – Implications for Biodiversity in relation to Environmental Change
- 2015
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Ingår i: Annales Botanici Fennici. - : Finnish Zoological and Botanical Publishing Board. - 0003-3847 .- 1797-2442. ; 52:3-4, s. 149-159
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Tidskriftsartikel (refereegranskat)abstract
- The alpine gentian, Gentiana nivalis, is an obligate annual. Because of its complete population turnover every year, it is likely to be more responsive to environmental shifts than are perennials, and also likely to undergo more rapid genetic change in response to selection pressure. The detected morphological differentiation between habitats was related to different proportions of spring- and autumn-germinating individuals with a larger proportion of winter annuals in the subalpine habitats. The spring-germinating annuals that have shorter time for development and have a shorter stature can still develop at the alpine sites where competition is weaker. The subalpine habitats are all semi-natural, shaped by livestock grazing and human activities related to summer farming. Declining human impact is leading to successional changes in the mountain landscape. The future of G. nivalis in the light of current trends in landscape development and climate change is discussed.
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| 2. |
- Vowles, Tage, et al.
(författare)
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The impact of shrub browsing by mountain hare and reindeer in subarctic Sweden
- 2016
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Ingår i: Plant Ecology and Diversity. - : Informa UK Limited. - 1755-0874 .- 1755-1668. ; 9:4, s. 421-428
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Tidskriftsartikel (refereegranskat)abstract
- Background: Climate warming has been causing an increase in tall shrub cover around the Arctic, however, mammalian herbivory has been shown to inhibit shrub expansion. Though the effect of reindeer (Rangifer tarandus) and many other mammals has been widely studied in this context, the role of the mountain hare (Lepus timidus) in subarctic Scandinavia remains unknown. Aims: To quantify browsing from mountain hare and reindeer on tall shrubs in different vegetation types and to investigate differences in shrub preference between the two. Methods: In the summers of 2013 and 2014, we counted signs of browsing by hare and reindeer on tall shrub species in 31 study plots at three alpine locations in the Scandes range, Sweden. Results: Hare browsing was significantly more frequent than that by reindeer in two (dry-mesic heath and dry meadow) out of seven vegetation types studied. Reindeer browsing was significantly higher in the low herb meadow and Långfjället shrub heath. Two shrub species, Betula nana and Salix hastata, were significantly more browsed by hare, while reindeer browsing was significantly higher on S. phylicifolia and S. lapponum. Conclusions: Our results show that mountain hares can cause extensive damage to tall shrubs in the subarctic and may have a stronger impact on shrub communities than previously recognised.
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| 3. |
- Abbott, Benjamin W., et al.
(författare)
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Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire : an expert assessment
- 2016
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.
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| 4. |
- Alatalo, J. M., et al.
(författare)
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Bryophyte cover and richness decline after 18 years of experimental warming in alpine Sweden
- 2020
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Ingår i: Aob Plants. - Oxford : Oxford University Press (OUP). - 2041-2851. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is expected to affect alpine and Arctic tundra communities. Most previous long-term studies have focused on impacts on vascular plants, this study examined impacts of long-term warming on bryophyte communities. Experimental warming with open-top chambers (OTCs) was applied for 18 years to a mesic meadow and a dry heath alpine plant community. Species abundance was measured in 1995, 1999, 2001 and 2013. Species composition changed significantly from original communities in the heath, but remained similar in mesic meadow. Experimental warming increased beta diversity in the heath. Bryophyte cover and species richness both declined with long-term warming, while Simpson diversity showed no significant responses. Over the 18-year period, bryophyte cover in warmed plots decreased from 43 % to 11 % in heath and from 68 % to 35 % in meadow (75 % and 48 % decline, respectively, in original cover), while richness declined by 39 % and 26 %, respectively. Importantly, the decline in cover and richness first emerged after 7 years. Warming caused significant increase in litter in both plant communities. Deciduous shrub and litter cover had negative impact on bryophyte cover. We show that bryophyte species do not respond similarly to climate change. Total bryophyte cover declined in both heath and mesic meadow under experimental long-term warming (by 1.5-3 degrees C), driven by general declines in many species. Principal response curve, cover and richness results suggested that bryophytes in alpine heath are more susceptible to warming than in meadow, supporting the suggestion that bryophytes may be less resistant in drier environments than in wetter habitats. Species loss was slower than the decline in bryophyte abundance, and diversity remained similar in both communities. Increased deciduous shrub and litter cover led to decline in bryophyte cover. The non-linear response to warming over time underlines the importance of long-term experiments and monitoring.
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| 5. |
- Alatalo, J. M., et al.
(författare)
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Changes in plant composition and diversity in an alpine heath and meadow after 18 years of experimental warming
- 2022
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Ingår i: Alpine Botany. - Basel : Springer Science and Business Media LLC. - 1664-2201 .- 1664-221X. ; 132, s. 181-193
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Tidskriftsartikel (refereegranskat)abstract
- Global warming is expected to have large impacts on high alpine and Arctic ecosystems in the future. Here we report effects of 18 years of experimental warming on two contrasting high alpine plant communities in subarctic Sweden. Using open-top chambers, we analysed effects of long-term passive experimental warming on a heath and a meadow. We determined the impact on species composition, species diversity (at the level of rare, common and dominant species), and phylogenetic and functional diversity. Long-term warming drove differentiation in species composition in both communities; warmed plots, but not control plots, had distinctly different species composition in 2013 compared with 1995. Beta diversity increased in the meadow, while it decreased in the heath. Long-term warming had significant negative effects on the three orders of phylogenetic Hill diversity in the meadow. There was a similar tendency in the heath, but only phylogenetic diversity of dominant species was significantly affected. Long-term warming caused reductions in forbs in the heath, while evergreen shrubs increased. In the meadow, deciduous and evergreen shrubs showed increased abundance from 2001 to 2013 in warmed plots. Responses in species and phylogenetic diversity to experimental warming varied over both time (medium (7 years) vs long-term (18 years)) and space (between two neighbouring plant communities). The meadow community was more negatively affected in terms of species and phylogenetic diversity than the heath community. A potential driver for the changes in the meadow may be decreased soil moisture caused by long-term warming.
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| 6. |
- Alatalo, Juha M., et al.
(författare)
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Climate change and climatic events: community-, functional- and species-level responses of bryophytes and lichens to constant, stepwise, and pulse experimental warming in an alpine tundra
- 2014
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Ingår i: Alpine Botany. - : Springer Science and Business Media LLC. - 1664-2201 .- 1664-221X. ; 124:2, s. 81-91
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally imposed three different kinds of warming scenarios over 3 years on an alpine meadow community to identify the differential effects of climate warming and extreme climatic events on the abundance and biomass of bryophytes and lichens. Treatments consisted of (a) a constant level of warming with open top chambers (an average temperature increase of 1.87 A degrees C), (b) a yearly stepwise increase of warming (average temperature increases of 1.0; 1.87 and 3.54 A degrees C, consecutively), and (c) a pulse warming, i.e., a single first year pulse event of warming (average temperature increase of 3.54 A degrees C only during the first year). To our knowledge, this is the first climate change study that attempts to distinguish between the effects of constant, stepwise and pulse warming on bryophyte and lichen communities. We hypothesised that pulse warming would have a significant short-term effect compared to the other warming treatments, and that stepwise warming would have a significant mid-term effect compared to the other warming treatments. Acrocarpous bryophytes as a group increased in abundance and biomass to the short-term effect of pulse warming. We found no significant effects of mid-term (third-year) stepwise warming. However, one pleurocarpous bryophyte species, Tomentypnum nitens, generally increased in abundance during the warm year 1997 but decreased in control plots and in response to the stepwise warming treatment. Three years of experimental warming (all treatments as a group) did have a significant impact at the community level, yet changes in abundance did not translate into significant changes in the dominance hierarchies at the functional level (for acrocarpous bryophytes, pleurocarpous bryophytes, Sphagnum or lichens), or in significant changes in other bryophyte or lichen species. The results suggest that bryophytes and lichens, both at the functional group and species level, to a large extent are resistant to the different climate change warming simulations that were applied.
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| 7. |
- Alatalo, Juha M., et al.
(författare)
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Dominance hierarchies, diversity and species richness of vascular plants in an alpine meadow: Contrasting short and medium termresponses to simulated global change
- 2014
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Ingår i: PeerJ. - : PeerJ Inc.. - 2167-8359. ; 2014:1
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Tidskriftsartikel (refereegranskat)abstract
- We studied the impact of simulated global change on a high alpine meadow plant community. Specifically, we examined whether short-term (5 years) responses are good predictors for medium-term (7 years) changes in the system by applying a factorial warming and nutrient manipulation to 20 plots in Latnjajaure, subarctic Sweden. Seven years of experimental warming and nutrient enhancement caused dramatic shifts in dominance hierarchies in response to the nutrient and the combined warming and nutrient enhancement treatments. Dominance hierarchies in the meadow moved from a community being dominated by cushion plants, deciduous, and evergreen shrubs to a community being dominated by grasses, sedges, and forbs. Short-termresponses were shown to be inconsistent in their ability to predict medium-term responses for most functional groups, however, grasses showed a consistent and very substantial increase in response to nutrient addition over the seven years. The non-linear responses over time point out the importance of longer-term studies with repeated measurements to be able to better predict future changes. Forecasted changes to temperature and nutrient availability have implications for trophic interactions, and may ultimately influence the access to and palatability of the forage for grazers. Depending on what anthropogenic change will be most pronounced in the future (increase in nutrient deposits, warming, or a combination of them both), different shifts in community dominance hierarchies may occur. Generally, this study supports the productivity-diversity relationship found across arctic habitats, with community diversity peaking in mid-productivity systems and degrading as nutrient availability increases further. This is likely due the increasing competition in plant-plant interactions and the shifting dominance structure with grasses taking over the experimental plots, suggesting that global change could have high costs to biodiversity in the Arctic. © 2014 Alatalo et al.
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| 8. |
- Alatalo, J. M., et al.
(författare)
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Effects of ambient climate and three warming treatments on fruit production in an alpine, subarctic meadow community
- 2021
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Ingår i: American Journal of Botany. - Oxford : Wiley. - 0002-9122 .- 1537-2197. ; 108:3, s. 411-422
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Tidskriftsartikel (refereegranskat)abstract
- Premise Climate change is having major impacts on alpine and arctic regions, and inter-annual variations in temperature are likely to increase. How increased climate variability will impact plant reproduction is unclear. Methods In a 4-year study on fruit production by an alpine plant community in northern Sweden, we applied three warming regimes: (1) a static level of warming with open-top chambers (OTC), (2) press warming, a yearly stepwise increase in warming, and (3) pulse warming, a single-year pulse event of higher warming. We analyzed the relationship between fruit production and monthly temperatures during the budding period, fruiting period, and whole fruit production period and the effect of winter and summer precipitation on fruit production. Results Year and treatment had a significant effect on total fruit production by evergreen shrubs, Cassiope tetragona, and Dryas octopetala, with large variations between treatments and years. Year, but not treatment, had a significant effect on deciduous shrubs and graminoids, both of which increased fruit production over the 4 years, while forbs were negatively affected by the press warming, but not by year. Fruit production was influenced by ambient temperature during the previous-year budding period, current-year fruiting period, and whole fruit production period. Minimum and average temperatures were more important than maximum temperature. In general, fruit production was negatively correlated with increased precipitation. Conclusions These results indicate that predicted increased climate variability and increased precipitation due to climate change may affect plant reproductive output and long-term community dynamics in alpine meadow communities.
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| 9. |
- Alatalo, J. M., et al.
(författare)
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Impact of ambient temperature, precipitation and seven years of experimental warming and nutrient addition on fruit production in an alpine heath and meadow community
- 2022
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Ingår i: Science of the Total Environment. - Amsterdam : Elsevier BV. - 0048-9697 .- 1879-1026. ; 836
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Tidskriftsartikel (refereegranskat)abstract
- Alpine and polar regions are predicted to be among the most vulnerable to changes in temperature, precipitation, and nutrient availability. We carried out a seven-year factorial experiment with warming and nutrient addition in two alpine vegetation communities. We analyzed the relationship between fruit production and monthly mean, maximum, and min temperatures during the fall of the pre-fruiting year, the fruiting summer, and the whole fruit production period, and measured the effects of precipitation and growing and thawing degree days (GDD & TDD) on fruit production. Nutrient addition (heath: 27.88 +/- 3.19 fold change at the end of the experiment; meadow: 18.02 +/- 4.07) and combined nutrient addition and warming (heath: 20.63 +/- 29.34 fold change at the end of the experiment; meadow: 18.21 +/- 16.28) increased total fruit production and fruit production of graminoids. Fruit production of evergreen and deciduous shrubs fluctuated among the treatments and years in both the heath and meadow. Pre-maximum temperatures had a negative effect on fruit production in both communities, while current year maximum temperatures had a positive impact on fruit production in the meadow. Pre-minimum, pre-mean, current mean, total minimum, and total mean temperatures were all positively correlated with fruit production in the meadow. The current year and total precipitation had a negative effect on the fruit production of deciduous shrubs in the heath. GDD had a positive effect on fruit production in both communities, while TDD only impacted fruit production in the meadow. Increased nutrient availability increased fruit production over time in the high alpine plant communities, while experimental warming had either no effect or a negative effect. Deciduous shrubs were the most sensitive to climate parameters in both communities, and the meadow was more sensitive than the heath. The difference in importance of TDD for fruit production may be due to differences in snow cover in the two communities.
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| 10. |
- Alatalo, J. M., et al.
(författare)
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Impacts of different climate change regimes and extreme climatic events on an alpine meadow community
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Climate variability is expected to increase in future but there exist very few experimental studies that apply different warming regimes on plant communities over several years. We studied an alpine meadow community under three warming regimes over three years. Treatments consisted of (a) a constant level of warming with open-top chambers (ca. 1.9 degrees C above ambient), (b) yearly stepwise increases in warming (increases of ca. 1.0, 1.9 and 3.5 degrees C), and (c) pulse warming, a single first-year pulse event of warming (increase of ca. 3.5 degrees C). Pulse warming and stepwise warming was hypothesised to cause distinct first-year and third-year effects, respectively. We found support for both hypotheses; however, the responses varied among measurement levels (whole community, canopy, bottom layer, and plant functional groups), treatments, and time. Our study revealed complex responses of the alpine plant community to the different experimentally imposed climate warming regimes. Plant cover, height and biomass frequently responded distinctly to the constant level of warming, the stepwise increase in warming and the extreme pulse-warming event. Notably, we found that stepwise warming had an accumulating effect on biomass, the responses to the different warming regimes varied among functional groups, and the short-term perturbations had negative effect on species richness and diversity
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| 11. |
- Alatalo, J. M., et al.
(författare)
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Responses of lichen communities to 18 years of natural and experimental warming
- 2017
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Ingår i: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 120:1, s. 159-170
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Tidskriftsartikel (refereegranskat)abstract
- Background and Aims Climate change is expected to have major impacts on high alpine and arctic ecosystems in the future, but empirical data on the impact of long-term warming on lichen diversity and richness are sparse. This study report the effects of 18 years of ambient and experimental warming on lichens and vascular plant cover in two alpine plant communities, a dry heath with sparse canopy cover (54 %) and a mesic meadow with a more developed (67 %) canopy cover, in sub-arctic Sweden. Methods The effects of long-term passive experimental warming using open top chambers (OTCs) on lichens and total vascular plant cover, and the impact of plant cover on lichen community parameters, were analysed. Key Results Between 1993 and 2013, mean annual temperature increased about 2 degrees C. Both site and experimental warming had a significant effect on cover, species richness, effective number of species evenness of lichens, and total plant canopy cover. Lichen cover increased in the heath under ambient conditions, and remained more stable under experimental warming. The negative effect on species richness and effective number of species was driven by a decrease in lichens under experimental warming in the meadow. Lichen cover, species richness, effective number of species evenness were negatively correlated with plant canopy cover. There was a significant negative impact on one species and a non-significant tendency of lower abundance of the most common species in response to experimental warming. Conclusions The results from the long-term warming study imply that arctic and high alpine lichen communities are likely to be negatively affected by climate change and an increase in plant canopy cover. Both biotic and abiotic factors are thus important for future impacts of climate change on lichens.
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| 12. |
- Alatalo, Juha M, 1966-, et al.
(författare)
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Testing reliability of short-term responses to predict longer-term responses of bryophytes and lichens to environmental change
- 2015
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Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X .- 1872-7034. ; 58, s. 77-85
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Tidskriftsartikel (refereegranskat)abstract
- Environmental changes are predicted to have severe and rapid impacts on polar and alpine regions. At high latitudes/altitudes, cryptogams such as bryophytes and lichens are of great importance in terms of biomass, carbon/nutrient cycling, cover and ecosystem functioning. This seven-year factorial experiment examined the effects of fertilizing and experimental warming on bryophyte and lichen abundance in an alpine meadow and a heath community in subarctic Sweden. The aim was to determine whether shortterm responses (five years) are good predictors of longer-term responses (seven years). Fertilizing and warming had significant negative effects on total and relative abundance of bryophytes and lichens, with the largest and most rapid decline caused by fertilizing and combined fertilizing and warming. Bryophytes decreased most in the alpine meadow community, which was bryophyte-dominated, and lichens decreased most in the heath community, which was lichen-dominated. This was surprising, as the most diverse group in each community was expected to be most resistant to perturbation. Warming alone had a delayed negative impact. Of the 16 species included in statistical analyses, seven were significantly negatively affected. Overall, the impacts of simulated warming on bryophytes and lichens as a whole and on individual species differed in time and magnitude between treatments and plant communities (meadow and heath). This will likely cause changes in the dominance structures over time. These results underscore the importance of longer-term studies to improve the quality of data used in climate change models, as models based on short-term data are poor predictors of long-term responses of bryophytes and lichens. (C) 2015 Elsevier Ltd. All rights reserved.
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| 13. |
- Alatalo, Juha M., et al.
(författare)
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Vascular plant abundance and diversity in an alpine heath under observed and simulated global change
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Global change is predicted to cause shifts in species distributions and biodiversity in arctic tundra. We applied factorial warming and nutrient manipulation to a nutrient and species poor alpine/arctic heath community for seven years. Vascular plant abundance in control plots increased by 31%. There were also notable changes in cover in the nutrient and combined nutrient and warming treatments, with deciduous and evergreen shrubs declining, grasses overgrowing these plots. Sedge abundance initially increased significantly with nutrient amendment and then declined, going below initial values in the combined nutrient and warming treatment. Nutrient addition resulted in a change in dominance hierarchy from deciduous shrubs to grasses. We found significant declines in vascular plant diversity and evenness in the warming treatment and a decline in diversity in the combined warming and nutrient addition treatment, while nutrient addition caused a decline in species richness. The results give some experimental support that species poor plant communities with low diversity may be more vulnerable to loss of species diversity than communities with higher initial diversity. The projected increase in nutrient deposition and warming may therefore have negative impacts on ecosystem processes, functioning and services due to loss of species diversity in an already impoverished environment.
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| 14. |
- Ali, A., et al.
(författare)
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Diversity-productivity dependent resistance of an alpine plant community to different climate change scenarios
- 2016
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Ingår i: Ecological Research. - : Wiley. - 0912-3814 .- 1440-1703. ; 31:6, s. 935-945
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Tidskriftsartikel (refereegranskat)abstract
- Here we report from a experiment imposing different warming scenarios [control with ambient temperature, constant level of moderate warming for 3 years, stepwise increase in warming for 3 years, and one season of high level warming (pulse) simulating an extreme summer event] on an alpine ecosystem to study the impact on species diversity-biomass relationship, and community resistance in terms of biomass production. Multiple linear mixed models indicate that experimental years had stronger influence on biomass than warming scenarios and species diversity. Species diversity and biomass had almost humpback relationships under different warming scenarios over different experimental years. There was generally a negative diversity-biomass relationship, implying that a positive diversity-biomass relationship was not the case. The application of different warming scenarios did not change this tendency. The change in community resistance to all warming scenarios was generally negatively correlated with increasing species diversity, the strength of the correlation varying both between treatments and between years within treatments. The strong effect of experimental years was consistent with the notion that niche complementarity effects increase over time, and hence, higher biomass productivity over experimental years. The strongest negative relationship was found in the first year of the pulse treatment, indicating that the community had weak resistance to an extreme event of one season of abnormally warm climate. Biomass production started recovering during the two subsequent years. Contrasting biomass-related resistance emerged in the different treatments, indicating that micro sites within the same plant community may differ in their resistance to different warming scenarios.
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| 15. |
- 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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| 16. |
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| 17. |
- Baruah, G., et al.
(författare)
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Community and species-specific responses of plant traits to 23 years of experimental warming across subarctic tundra plant communities
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- To improve understanding of how global warming may affect competitive interactions among plants, information on the responses of plant functional traits across species to long-term warming is needed. Here we report the effect of 23 years of experimental warming on plant traits across four different alpine subarctic plant communities: tussock tundra, Dryas heath, dry heath and wet meadow. Open-top chambers (OTCs) were used to passively warm the vegetation by 1.5-3 degrees C. Changes in leaf width, leaf length and plant height of 22 vascular plant species were measured. Long-term warming significantly affected all plant traits. Overall, plant species were taller, with longer and wider leaves, compared with control plots, indicating an increase in biomass in warmed plots, with 13 species having significant increases in at least one trait and only three species having negative responses. The response varied among species and plant community in which the species was sampled, indicating community-warming interactions. Thus, plant trait responses are both species- and community-specific. Importantly, we show that there is likely to be great variation between plant species in their ability to maintain positive growth responses over the longer term, which might cause shifts in their relative competitive ability.
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| 18. |
- Baruah, Gaurav, et al.
(författare)
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Impacts of seven years of experimental warming and nutrient addition on neighbourhood species interactions and community structure in two contrasting alpine plant communities
- 2018
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Ingår i: Ecological Complexity. - : Elsevier. - 1476-945X .- 1476-9840. ; 33:Supplement C, s. 31-40
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Global change is predicted to have major impacts on alpine and arctic ecosystems. Plant fitness and growth will be determined by how plants interact with each other at smaller scales. Local-scale neighbourhood interactions may be altered by environmental pertubations, which could fundamentally affect community structure. This study examined the effects of seven years of experimental warming and nutrient addition on overall changes in the community structure and patterns of interspecific interaction between neighbouring plant species in two contrasting alpine plant communities, mesic meadow and poor heath, in subarctic Sweden. We used a network approach to quantify the dissimilarity of plant interaction networks and the average number of interspecific neighbourhood interactions over time in response to different environmental perturbations. The results revealed that combined warming and nutrient addition had significant negative effects on how dissimilar plant interaction networks were over time compared with the control. Moreover, plant–plant neighbourhood interaction networks were more dissimilar over time in nutrient-poor heath than in nutrient-rich mesic meadow. In addition, nutrient addition alone and combined nutrient addition and warming significantly affected neighbourhood species interactions in both plant communities. Surprisingly, changes in interspecific neighbourhood interactions over time in both communities were very similar, suggesting that the nutrient-poor heath is as robust to experimental environmental perturbation as the mesic meadow. Comparisons of changes in neighbouring species interactions with changes in evenness and richness at the same scale, in order to determine whether diversity drove such changes in local-scale interaction patterns, provided moderate evidence that diversity was behind the changes in local-scale interspecific neighbourhood interactions. This implied that species might interact at smaller scales than those at which community measures were made. Overall, these results demonstrated that global change involving increased nutrient deposition and warming is likely to affect species interactions and alter community structure in plant communities, whether rich or poor in nutrients and species.
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| 19. |
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| 20. |
- 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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| 21. |
- 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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| 22. |
- 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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| 23. |
- 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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| 24. |
- Björk, Robert G., 1974, et al.
(författare)
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Climate-related soil changes in tundra ecosystems at Latnjajaure, northern Sweden – an ITEX-IPY project
- 2010
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Ingår i: International Polar Year Oslo Science Conference.
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Konferensbidrag (refereegranskat)abstract
- During the 90'ies, the International Tundra Experiment (ITEX) was established as a leading project in arctic and alpine ecology, and has become a model for many later network establishments. The present study capitalizes on the early efforts of ITEX and aims at assessing ecosystem changes in the alpine areas of northern Sweden above timberline, i.e. the tundra, in relation to global change. By using the "old" ITEX plots established during the early years of the program we have measured ecosystem respiration (ER), the Normalized Difference Vegetation Index, and nitrogen (N) mineralization over the growing season. In addition, have soil samples been taken to quantify changes in the carbon (C) and N pool, including 13C and 15N. After 12 to 15 years of open top chamber (OTC) treatment no statistical effect was found on the soil temperature (10 cm soil depth), although the was an overall increase in all OTC by +0.2°C. However, the soil moisture decreased significantly by 3-14%, depending on plant community, in the OTCs compared to ambient conditions. Preliminary, there was a 20-37% non-significant higher mean ER in the OTC compared to the ambient plots over the growing season. Furthermore, the OTC treatment did not affect the growing season mineralization of inorganic N, or total C and N content of the soil. The stable isotope data showed both enrichment and depletion as a consequence of the OTC treatment, but no general pattern was discerned. Thus, this non-significant higher ER is most likely of plant origin than soil, as the plant standing biomass has increased in the OTCs. This study does not support the current consensus that tundra soils will alter their C and N dynamics in response to climate change.
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| 25. |
- 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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