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Across-Habitat Comparison of Diazotroph Activity in the Subarctic.

https://arctichealth.org/en/permalink/ahliterature258243
Source
Microb Ecol. 2014 Nov 18;
Publication Type
Article
Date
Nov-18-2014
Author
Kathrin Rousk
Pernille L Sorensen
Signe Lett
Anders Michelsen
Author Affiliation
Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark, kathrin.rousk@gmx.net.
Source
Microb Ecol. 2014 Nov 18;
Date
Nov-18-2014
Language
English
Publication Type
Article
Abstract
Nitrogen (N) fixation by N2-fixing bacteria (diazotrophs) is the primary N input to pristine ecosystems like boreal forests and subarctic and arctic tundra. However, the contribution by the various diazotrophs to habitat N2 fixation remains unclear. We present results from in situ assessments of N2 fixation of five diazotroph associations (with a legume, lichen, feather moss, Sphagnum moss and free-living) incorporating the ground cover of the associations in five typical habitats in the subarctic (wet and dry heath, polygon-heath, birch forest, mire). Further, we assessed the importance of soil and air temperature, as well as moisture conditions for N2 fixation. Across the growing season, the legume had the highest total as well as the highest fraction of N2 fixation rates at habitat level in the heaths (>85 % of habitat N2 fixation), whereas the free-living diazotrophs had the highest N2 fixation rates in the polygon heath (56 %), the lichen in the birch forest (87 %) and Sphagnum in the mire (100 %). The feather moss did not contribute more than 15 % to habitat N2 fixation in any of the habitats despite its high ground cover. Moisture content seemed to be a major driver of N2 fixation in the lichen, feather moss and free-living diazotrophs. Our results show that the range of N2 fixers found in pristine habitats contribute differently to habitat N2 fixation and that ground cover of the associates does not necessarily mirror contribution.
PubMed ID
25403111 View in PubMed
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Amplification of plant volatile defence against insect herbivory in a warming Arctic tundra.

https://arctichealth.org/en/permalink/ahliterature302856
Source
Nat Plants. 2019 06; 5(6):568-574
Publication Type
Letter
Research Support, Non-U.S. Gov't
Date
06-2019
Author
Tao Li
Thomas Holst
Anders Michelsen
Riikka Rinnan
Author Affiliation
Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark. tao.li@bio.ku.dk.
Source
Nat Plants. 2019 06; 5(6):568-574
Date
06-2019
Language
English
Publication Type
Letter
Research Support, Non-U.S. Gov't
Keywords
Animals
Betula - immunology - parasitology
Ecosystem
Global warming
Herbivory
Insecta - physiology
Tundra
Volatile Organic Compounds - metabolism
Abstract
Plant-emitted volatile organic compounds (VOCs) play fundamental roles in atmospheric chemistry and ecological processes by contributing to aerosol formation1 and mediating species interactions2. Rising temperatures and the associated shifts in vegetation composition have been shown to be the primary drivers of plant VOC emissions in Arctic ecosystems3. Although herbivorous insects also strongly alter plant VOC emissions2, no studies have addressed the impact of herbivory on plant VOC emissions in the Arctic. Here we show that warming dramatically increases the amount, and alters the blend, of VOCs released in response to herbivory. We observed that a tundra ecosystem subjected to warming, by open-top chambers, for 8 or 18 years showed a fourfold increase in leaf area eaten by insect herbivores. Herbivory by autumnal moth (Epirrita autumnata) larvae, and herbivory-mimicking methyl jasmonate application, on the widespread circumpolar dwarf birch (Betula nana) both substantially increased emissions of terpenoids. The long-term warming treatments and mimicked herbivory caused, on average, a two- and fourfold increase in monoterpene emissions, respectively. When combined, emissions increased 11-fold, revealing a strong synergy between warming and herbivory. The synergistic effect was even more pronounced for homoterpene emissions. These findings suggest that, in the rapidly warming Arctic, insect herbivory may be a primary determinant of VOC emissions during periods of active herbivore feeding.
PubMed ID
31182843 View in PubMed
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Amplification of plant volatile defence against insect herbivory in a warming Arctic tundra.

https://arctichealth.org/en/permalink/ahliterature300874
Source
Nat Plants. 2019 06; 5(6):568-574
Publication Type
Letter
Research Support, Non-U.S. Gov't
Date
06-2019
Author
Tao Li
Thomas Holst
Anders Michelsen
Riikka Rinnan
Author Affiliation
Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Copenhagen, Denmark. tao.li@bio.ku.dk.
Source
Nat Plants. 2019 06; 5(6):568-574
Date
06-2019
Language
English
Publication Type
Letter
Research Support, Non-U.S. Gov't
Abstract
Plant-emitted volatile organic compounds (VOCs) play fundamental roles in atmospheric chemistry and ecological processes by contributing to aerosol formation1 and mediating species interactions2. Rising temperatures and the associated shifts in vegetation composition have been shown to be the primary drivers of plant VOC emissions in Arctic ecosystems3. Although herbivorous insects also strongly alter plant VOC emissions2, no studies have addressed the impact of herbivory on plant VOC emissions in the Arctic. Here we show that warming dramatically increases the amount, and alters the blend, of VOCs released in response to herbivory. We observed that a tundra ecosystem subjected to warming, by open-top chambers, for 8 or 18 years showed a fourfold increase in leaf area eaten by insect herbivores. Herbivory by autumnal moth (Epirrita autumnata) larvae, and herbivory-mimicking methyl jasmonate application, on the widespread circumpolar dwarf birch (Betula nana) both substantially increased emissions of terpenoids. The long-term warming treatments and mimicked herbivory caused, on average, a two- and fourfold increase in monoterpene emissions, respectively. When combined, emissions increased 11-fold, revealing a strong synergy between warming and herbivory. The synergistic effect was even more pronounced for homoterpene emissions. These findings suggest that, in the rapidly warming Arctic, insect herbivory may be a primary determinant of VOC emissions during periods of active herbivore feeding.
PubMed ID
31182843 View in PubMed
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Are herbarium mosses reliable indicators of historical nitrogen deposition?

https://arctichealth.org/en/permalink/ahliterature289939
Source
Environ Pollut. 2017 Dec; 231(Pt 1):1201-1207
Publication Type
Journal Article
Date
Dec-2017
Author
Tora Finderup Nielsen
Jesper Ruf Larsen
Anders Michelsen
Hans Henrik Bruun
Author Affiliation
Department of Biology, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen Ø, Denmark. Electronic address: tora.nielsen@bio.ku.dk.
Source
Environ Pollut. 2017 Dec; 231(Pt 1):1201-1207
Date
Dec-2017
Language
English
Publication Type
Journal Article
Keywords
Bryophyta - chemistry
Carbon Isotopes - analysis
Denmark
Environmental Monitoring - methods
Environmental pollution - analysis
Lead - analysis
Magnesium - analysis
Nitrogen - analysis
Nitrogen Isotopes - analysis
Time Factors
Abstract
Mosses collected decades ago and stored in herbaria are often used to assess historical nitrogen deposition. This method is effectively based on the assumption that tissue N concentration remains constant during storage. The present study raises serious doubt about the generality of that assumption. We measured tissue N and C concentrations as well as d15N, d13C, Pb and Mg in herbarium and present day samples of seven bryophyte species from six sites across Denmark. While an increase in nitrogen deposition during the last century is well-documented for the study site, we surprisingly found foliar N concentration to be higher in historical samples than in modern samples. Based on d15N values and Pb concentration, we find nitrogen contamination of herbarium specimens during storage to be the most likely cause, possibly in combination with dilution though growth and/or decomposition during storage. We suggest ways to assess contamination and recommend caution to be taken when using herbarium specimens to assess historical pollution if exposure during storage cannot be ruled out.
PubMed ID
28420490 View in PubMed
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Biogenic volatile organic compound emissions along a high arctic soil moisture gradient.

https://arctichealth.org/en/permalink/ahliterature290127
Source
Sci Total Environ. 2016 Dec 15; 573:131-138
Publication Type
Journal Article
Date
Dec-15-2016
Author
Sarah Hagel Svendsen
Frida Lindwall
Anders Michelsen
Riikka Rinnan
Author Affiliation
Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Universitetsparken 15, DK -2100 Copenhagen E, Denmark; Center for Permafrost (CENPERM), Department of Geoscience and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK -1350 Copenhagen K, Denmark.
Source
Sci Total Environ. 2016 Dec 15; 573:131-138
Date
Dec-15-2016
Language
English
Publication Type
Journal Article
Keywords
Air Pollutants - analysis
Arctic Regions
Climate change
Ecosystem
Environmental Monitoring - methods
Ericaceae - growth & development
Greenland
Rosaceae - growth & development
Salix - growth & development
Soil - chemistry
Volatile Organic Compounds - analysis
Water - analysis
Abstract
Emissions of biogenic volatile organic compounds (BVOCs) from terrestrial ecosystems are important for the atmospheric chemistry and the formation of secondary organic aerosols, and may therefore influence the climate. Global warming is predicted to change patterns in precipitation and plant species compositions, especially in arctic regions where the temperature increase will be most pronounced. These changes are potentially highly important for the BVOC emissions but studies investigating the effects are lacking. The aim of this study was to investigate the quality and quantity of BVOC emissions from a high arctic soil moisture gradient extending from dry tundra to a wet fen. Ecosystem BVOC emissions were sampled five times in the July-August period using a push-pull enclosure technique, and BVOCs trapped in absorbent cartridges were analyzed using gas chromatography-mass spectrometry. Plant species compositions were estimated using the point intercept method. In order to take into account important underlying ecosystem processes, gross ecosystem production, ecosystem respiration and net ecosystem production were measured in connection with chamber-based BVOC measurements. Highest emissions of BVOCs were found from vegetation communities dominated by Salix arctica and Cassiope tetragona, which had emission profiles dominated by isoprene and monoterpenes, respectively. These results show that emissions of BVOCs are highly dependent on the plant cover supported by the varying soil moisture, suggesting that high arctic BVOC emissions may affect the climate differently if soil water content and plant cover change.
PubMed ID
27552736 View in PubMed
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Biogenic volatile organic compound emissions along a high arctic soil moisture gradient.

https://arctichealth.org/en/permalink/ahliterature275488
Source
Sci Total Environ. 2016 Aug 20;573:131-138
Publication Type
Article
Date
Aug-20-2016
Author
Sarah Hagel Svendsen
Frida Lindwall
Anders Michelsen
Riikka Rinnan
Source
Sci Total Environ. 2016 Aug 20;573:131-138
Date
Aug-20-2016
Language
English
Publication Type
Article
Abstract
Emissions of biogenic volatile organic compounds (BVOCs) from terrestrial ecosystems are important for the atmospheric chemistry and the formation of secondary organic aerosols, and may therefore influence the climate. Global warming is predicted to change patterns in precipitation and plant species compositions, especially in arctic regions where the temperature increase will be most pronounced. These changes are potentially highly important for the BVOC emissions but studies investigating the effects are lacking. The aim of this study was to investigate the quality and quantity of BVOC emissions from a high arctic soil moisture gradient extending from dry tundra to a wet fen. Ecosystem BVOC emissions were sampled five times in the July-August period using a push-pull enclosure technique, and BVOCs trapped in absorbent cartridges were analyzed using gas chromatography-mass spectrometry. Plant species compositions were estimated using the point intercept method. In order to take into account important underlying ecosystem processes, gross ecosystem production, ecosystem respiration and net ecosystem production were measured in connection with chamber-based BVOC measurements. Highest emissions of BVOCs were found from vegetation communities dominated by Salix arctica and Cassiope tetragona, which had emission profiles dominated by isoprene and monoterpenes, respectively. These results show that emissions of BVOCs are highly dependent on the plant cover supported by the varying soil moisture, suggesting that high arctic BVOC emissions may affect the climate differently if soil water content and plant cover change.
PubMed ID
27552736 View in PubMed
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Climate change-induced vegetation change as a driver of increased subarctic biogenic volatile organic compound emissions.

https://arctichealth.org/en/permalink/ahliterature274131
Source
Glob Chang Biol. 2015 Sep;21(9):3478-88
Publication Type
Article
Date
Sep-2015
Author
Hanna Valolahti
Minna Kivimäenpää
Patrick Faubert
Anders Michelsen
Riikka Rinnan
Source
Glob Chang Biol. 2015 Sep;21(9):3478-88
Date
Sep-2015
Language
English
Publication Type
Article
Keywords
Betula - chemistry
Climate change
Ecosystem
Gas Chromatography-Mass Spectrometry
Global warming
Plant Leaves - chemistry
Seasons
Sweden
Volatile Organic Compounds - analysis
Abstract
Emissions of biogenic volatile organic compounds (BVOCs) have been earlier shown to be highly temperature sensitive in subarctic ecosystems. As these ecosystems experience rapidly advancing pronounced climate warming, we aimed to investigate how warming affects the BVOC emissions in the long term (up to 13 treatment years). We also aimed to assess whether the increased litterfall resulting from the vegetation changes in the warming subarctic would affect the emissions. The study was conducted in a field experiment with factorial open-top chamber warming and annual litter addition treatments on subarctic heath in Abisko, northern Sweden. After 11 and 13 treatment years, BVOCs were sampled from plant communities in the experimental plots using a push-pull enclosure technique and collection into adsorbent cartridges during the growing season and analyzed with gas chromatography-mass spectrometry. Plant species coverage in the plots was analyzed by the point intercept method. Warming by 2??C caused a 2-fold increase in monoterpene and 5-fold increase in sesquiterpene emissions, averaged over all measurements. When the momentary effect of temperature was diminished by standardization of emissions to a fixed temperature, warming still had a significant effect suggesting that emissions were also indirectly increased. This indirect increase appeared to result from increased plant coverage and changes in vegetation composition. The litter addition treatment also caused significant increases in the emission rates of some BVOC groups, especially when combined with warming. The combined treatment had both the largest vegetation changes and the highest BVOC emissions. The increased emissions under litter addition were probably a result of a changed vegetation composition due to alleviated nutrient limitation and stimulated microbial production of BVOCs. We suggest that the changes in the subarctic vegetation composition induced by climate warming will be the major factor indirectly affecting the BVOC emission potentials and composition.
Notes
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PubMed ID
25994223 View in PubMed
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Contrasting above- and belowground organic matter decomposition and carbon and nitrogen dynamics in response to warming in High Arctic tundra.

https://arctichealth.org/en/permalink/ahliterature287587
Source
Glob Chang Biol. 2017 Dec 13;
Publication Type
Article
Date
Dec-13-2017
Author
Daan Blok
Samuel Faucherre
Imre Banyasz
Riikka Rinnan
Anders Michelsen
Bo Elberling
Source
Glob Chang Biol. 2017 Dec 13;
Date
Dec-13-2017
Language
English
Publication Type
Article
Abstract
Tundra regions are projected to warm rapidly during the coming decades. The tundra biome holds the largest terrestrial carbon pool, largely contained in frozen permafrost soils. With warming, these permafrost soils may thaw and become available for microbial decomposition, potentially providing a positive feedback to global warming. Warming may directly stimulate microbial metabolism but may also indirectly stimulate organic matter turnover through increased plant productivity by soil priming from root exudates and accelerated litter turnover rates. Here, we assess the impacts of experimental warming on turnover rates of leaf litter, active layer soil, and thawed permafrost sediment in two high-arctic tundra heath sites in NE-Greenland, either dominated by evergreen or deciduous shrubs. We incubated shrub leaf litter on the surface of control and warmed plots for one and two years. Active layer soil was collected from the plots to assess the effects of eight years of field warming on soil carbon stocks. Finally, we incubated open cores filled with newly thawed permafrost soil for two years in the active layer of the same plots. After field incubation, we measured basal respiration rates of recovered thawed permafrost cores in the lab. Warming significantly reduced litter mass loss by 26% after one year incubation, but differences in litter mass loss among treatments disappeared after two years incubation. Warming also reduced litter nitrogen mineralization and decreased the litter carbon to nitrogen ratio. Active layer soil carbon stocks were 15% reduced by warming, while soil dissolved nitrogen was reduced by half in warmed plots. Warming had a positive legacy effect on carbon turnover rates in thawed permafrost cores, with 10% higher respiration rates measured in cores from warmed plots. These results demonstrate that warming may have contrasting effects on above- and belowground tundra carbon turnover, possibly governed by microbial resource availability. This article is protected by copyright. All rights reserved.
PubMed ID
29235209 View in PubMed
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Contrasting above- and belowground organic matter decomposition and carbon and nitrogen dynamics in response to warming in High Arctic tundra.

https://arctichealth.org/en/permalink/ahliterature296993
Source
Glob Chang Biol. 2018 06; 24(6):2660-2672
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Date
06-2018
Author
Daan Blok
Samuel Faucherre
Imre Banyasz
Riikka Rinnan
Anders Michelsen
Bo Elberling
Author Affiliation
Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark.
Source
Glob Chang Biol. 2018 06; 24(6):2660-2672
Date
06-2018
Language
English
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Keywords
Arctic Regions
Biomass
Carbon Cycle
Global warming
Greenland
Nitrogen Cycle
Permafrost
Soil - chemistry
Tundra
Abstract
Tundra regions are projected to warm rapidly during the coming decades. The tundra biome holds the largest terrestrial carbon pool, largely contained in frozen permafrost soils. With warming, these permafrost soils may thaw and become available for microbial decomposition, potentially providing a positive feedback to global warming. Warming may directly stimulate microbial metabolism but may also indirectly stimulate organic matter turnover through increased plant productivity by soil priming from root exudates and accelerated litter turnover rates. Here, we assess the impacts of experimental warming on turnover rates of leaf litter, active layer soil and thawed permafrost sediment in two high-arctic tundra heath sites in NE-Greenland, either dominated by evergreen or deciduous shrubs. We incubated shrub leaf litter on the surface of control and warmed plots for 1 and 2 years. Active layer soil was collected from the plots to assess the effects of 8 years of field warming on soil carbon stocks. Finally, we incubated open cores filled with newly thawed permafrost soil for 2 years in the active layer of the same plots. After field incubation, we measured basal respiration rates of recovered thawed permafrost cores in the lab. Warming significantly reduced litter mass loss by 26% after 1 year incubation, but differences in litter mass loss among treatments disappeared after 2 years incubation. Warming also reduced litter nitrogen mineralization and decreased the litter carbon to nitrogen ratio. Active layer soil carbon stocks were reduced 15% by warming, while soil dissolved nitrogen was reduced by half in warmed plots. Warming had a positive legacy effect on carbon turnover rates in thawed permafrost cores, with 10% higher respiration rates measured in cores from warmed plots. These results demonstrate that warming may have contrasting effects on above- and belowground tundra carbon turnover, possibly governed by microbial resource availability.
PubMed ID
29235209 View in PubMed
Less detail

Doubled volatile organic compound emissions from subarctic tundra under simulated climate warming.

https://arctichealth.org/en/permalink/ahliterature97032
Source
New Phytol. 2010 Jul;187(1):199-208
Publication Type
Article
Date
Jul-2010
Author
Patrick Faubert
Päivi Tiiva
Asmund Rinnan
Anders Michelsen
Jarmo K Holopainen
Riikka Rinnan
Author Affiliation
Department of Environmental Science, University of Eastern Finland, PO Box 1627, FI-70211 Kuopio, Finland. patrick.faubert@uef.fi
Source
New Phytol. 2010 Jul;187(1):199-208
Date
Jul-2010
Language
English
Publication Type
Article
Abstract
*Biogenic volatile organic compound (BVOC) emissions from arctic ecosystems are important in view of their role in global atmospheric chemistry and unknown feedbacks to global warming. These cold ecosystems are hotspots of climate warming, which will be more severe here than averaged over the globe. We assess the effects of climatic warming on non-methane BVOC emissions from a subarctic heath. *We performed ecosystem-based chamber measurements and gas chromatography-mass spectrometry (GC-MS) analyses of the BVOCs collected on adsorbent over two growing seasons at a wet subarctic tundra heath hosting a long-term warming and mountain birch (Betula pubescens ssp. czerepanovii) litter addition experiment. *The relatively low emissions of monoterpenes and sesquiterpenes were doubled in response to an air temperature increment of only 1.9-2.5 degrees C, while litter addition had a minor influence. BVOC emissions were seasonal, and warming combined with litter addition triggered emissions of specific compounds. *The unexpectedly high rate of release of BVOCs measured in this conservative warming scenario is far above the estimates produced by the current models, which underlines the importance of a focus on BVOC emissions during climate change. The observed changes have implications for ecological interactions and feedback effects on climate change via impacts on aerosol formation and indirect greenhouse effects.
PubMed ID
20456056 View in PubMed
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22 records – page 1 of 3.