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Arctic browning: extreme events and trends reversing arctic greening.

https://arctichealth.org/en/permalink/ahliterature271915
Source
Glob Chang Biol. 2016 Apr 20;
Publication Type
Article
Date
Apr-20-2016
Author
Gareth K Phoenix
Jarle W Bjerke
Source
Glob Chang Biol. 2016 Apr 20;
Date
Apr-20-2016
Language
English
Publication Type
Article
PubMed ID
27095022 View in PubMed
Less detail

Arctic browning: Impacts of extreme climatic events on heathland ecosystem CO2 fluxes.

https://arctichealth.org/en/permalink/ahliterature298902
Source
Glob Chang Biol. 2019 02; 25(2):489-503
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Date
02-2019
Author
Rachael Treharne
Jarle W Bjerke
Hans Tømmervik
Laura Stendardi
Gareth K Phoenix
Author Affiliation
Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UK.
Source
Glob Chang Biol. 2019 02; 25(2):489-503
Date
02-2019
Language
English
Publication Type
Journal Article
Research Support, Non-U.S. Gov't
Keywords
Arctic Regions
Carbon Dioxide - chemistry
Climate change
Ecosystem
Greenhouse Gases - analysis
Norway
Abstract
Extreme climatic events are among the drivers of recent declines in plant biomass and productivity observed across Arctic ecosystems, known as "Arctic browning." These events can cause landscape-scale vegetation damage and so are likely to have major impacts on ecosystem CO2 balance. However, there is little understanding of the impacts on CO2 fluxes, especially across the growing season. Furthermore, while widespread shoot mortality is commonly observed with browning events, recent observations show that shoot stress responses are also common, and manifest as high levels of persistent anthocyanin pigmentation. Whether or how this response impacts ecosystem CO2 fluxes is not known. To address these research needs, a growing season assessment of browning impacts following frost drought and extreme winter warming (both extreme climatic events) on the key ecosystem CO2 fluxes Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP), ecosystem respiration (Reco ) and soil respiration (Rsoil ) was carried out in widespread sub-Arctic dwarf shrub heathland, incorporating both mortality and stress responses. Browning (mortality and stress responses combined) caused considerable site-level reductions in GPP and NEE (of up to 44%), with greatest impacts occurring at early and late season. Furthermore, impacts on CO2 fluxes associated with stress often equalled or exceeded those resulting from vegetation mortality. This demonstrates that extreme events can have major impacts on ecosystem CO2 balance, considerably reducing the carbon sink capacity of the ecosystem, even where vegetation is not killed. Structural Equation Modelling and additional measurements, including decomposition rates and leaf respiration, provided further insight into mechanisms underlying impacts of mortality and stress on CO2 fluxes. The scale of reductions in ecosystem CO2 uptake highlights the need for a process-based understanding of Arctic browning in order to predict how vegetation and CO2 balance will respond to continuing climate change.
PubMed ID
30474169 View in PubMed
Less detail

Arctic browning: Impacts of extreme climatic events on heathland ecosystem CO2 fluxes.

https://arctichealth.org/en/permalink/ahliterature296157
Source
Glob Chang Biol. 2018 Nov 25; :
Publication Type
Journal Article
Date
Nov-25-2018
Author
Rachael Treharne
Jarle W Bjerke
Hans Tømmervik
Laura Stendardi
Gareth K Phoenix
Author Affiliation
Department of Animal and Plant Sciences, The University of Sheffield, Sheffield, UK.
Source
Glob Chang Biol. 2018 Nov 25; :
Date
Nov-25-2018
Language
English
Publication Type
Journal Article
Abstract
Extreme climatic events are among the drivers of recent declines in plant biomass and productivity observed across Arctic ecosystems, known as "Arctic browning." These events can cause landscape-scale vegetation damage and so are likely to have major impacts on ecosystem CO2 balance. However, there is little understanding of the impacts on CO2 fluxes, especially across the growing season. Furthermore, while widespread shoot mortality is commonly observed with browning events, recent observations show that shoot stress responses are also common, and manifest as high levels of persistent anthocyanin pigmentation. Whether or how this response impacts ecosystem CO2 fluxes is not known. To address these research needs, a growing season assessment of browning impacts following frost drought and extreme winter warming (both extreme climatic events) on the key ecosystem CO2 fluxes Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP), ecosystem respiration (Reco ) and soil respiration (Rsoil ) was carried out in widespread sub-Arctic dwarf shrub heathland, incorporating both mortality and stress responses. Browning (mortality and stress responses combined) caused considerable site-level reductions in GPP and NEE (of up to 44%), with greatest impacts occurring at early and late season. Furthermore, impacts on CO2 fluxes associated with stress often equalled or exceeded those resulting from vegetation mortality. This demonstrates that extreme events can have major impacts on ecosystem CO2 balance, considerably reducing the carbon sink capacity of the ecosystem, even where vegetation is not killed. Structural Equation Modelling and additional measurements, including decomposition rates and leaf respiration, provided further insight into mechanisms underlying impacts of mortality and stress on CO2 fluxes. The scale of reductions in ecosystem CO2 uptake highlights the need for a process-based understanding of Arctic browning in order to predict how vegetation and CO2 balance will respond to continuing climate change.
PubMed ID
30474169 View in PubMed
Less detail

Changing Arctic snow cover: A review of recent developments and assessment of future needs for observations, modelling, and impacts.

https://arctichealth.org/en/permalink/ahliterature270915
Source
Ambio. 2016 Mar 17;
Publication Type
Article
Date
Mar-17-2016
Author
Stef Bokhorst
Stine Højlund Pedersen
Ludovic Brucker
Oleg Anisimov
Jarle W Bjerke
Ross D Brown
Dorothee Ehrich
Richard L H Essery
Achim Heilig
Susanne Ingvander
Cecilia Johansson
Margareta Johansson
Ingibjörg Svala Jónsdóttir
Niila Inga
Kari Luojus
Giovanni Macelloni
Heather Mariash
Donald McLennan
Gunhild Ninis Rosqvist
Atsushi Sato
Hannele Savela
Martin Schneebeli
Aleksandr Sokolov
Sergey A Sokratov
Silvia Terzago
Dagrun Vikhamar-Schuler
Scott Williamson
Yubao Qiu
Terry V Callaghan
Source
Ambio. 2016 Mar 17;
Date
Mar-17-2016
Language
English
Publication Type
Article
Abstract
Snow is a critically important and rapidly changing feature of the Arctic. However, snow-cover and snowpack conditions change through time pose challenges for measuring and prediction of snow. Plausible scenarios of how Arctic snow cover will respond to changing Arctic climate are important for impact assessments and adaptation strategies. Although much progress has been made in understanding and predicting snow-cover changes and their multiple consequences, many uncertainties remain. In this paper, we review advances in snow monitoring and modelling, and the impact of snow changes on ecosystems and society in Arctic regions. Interdisciplinary activities are required to resolve the current limitations on measuring and modelling snow characteristics through the cold season and at different spatial scales to assure human well-being, economic stability, and improve the ability to predict manage and adapt to natural hazards in the Arctic region.
PubMed ID
26984258 View in PubMed
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Climatic and biotic extreme events moderate long-term responses of above- and belowground sub-Arctic heathland communities to climate change.

https://arctichealth.org/en/permalink/ahliterature263921
Source
Glob Chang Biol. 2015 Jun 25;
Publication Type
Article
Date
Jun-25-2015
Author
Stef Bokhorst
Gareth K Phoenix
Matty P Berg
Terry V Callaghan
Christopher Kirby-Lambert
Jarle W Bjerke
Source
Glob Chang Biol. 2015 Jun 25;
Date
Jun-25-2015
Language
English
Publication Type
Article
Abstract
Climate change impacts are not uniform across the Arctic region because interacting factors causes large variations in local ecosystem change. Extreme climatic events and population cycles of herbivores occur simultaneously against a background of gradual climate warming trends and can redirect ecosystem change along routes that are difficult to predict. Here, we present the results from sub-Arctic heath vegetation and its belowground micro-arthropod community in response to the two main drivers of vegetation damage in this region: extreme winter warming events and subsequent outbreaks of the defoliating autumnal moth caterpillar (Epirrita autumnata). Evergreen dwarf shrub biomass decreased (30%) following extreme winter warming events and again by moth caterpillar grazing. Deciduous shrubs that were previously exposed to an extreme winter warming event were not affected by the moth caterpillar grazing while those that were not exposed to warming events (control plots) showed reduced (23%) biomass from grazing. Cryptogam cover increased irrespective of grazing or winter warming events. Micro-arthropods declined (46%) following winter warming but did not respond to changes in plant community. Extreme winter warming and caterpillar grazing suppressed the CO2 fluxes of the ecosystem. This article is protected by copyright. All rights reserved.
PubMed ID
26111101 View in PubMed
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Combining modelling tools to evaluate a goose management scheme.

https://arctichealth.org/en/permalink/ahliterature280772
Source
Ambio. 2017 Mar;46(Suppl 2):210-223
Publication Type
Article
Date
Mar-2017
Author
Johannes M Baveco
Anne-Kari Bergjord
Jarle W Bjerke
Magda E Chudzinska
Loïc Pellissier
Caroline E Simonsen
Jesper Madsen
Ingunn M Tombre
Bart A Nolet
Source
Ambio. 2017 Mar;46(Suppl 2):210-223
Date
Mar-2017
Language
English
Publication Type
Article
Keywords
Agriculture - methods
Animals
Conservation of Natural Resources
Geese - physiology
Models, Biological
Norway
Population Density
Seasons
Weather
Abstract
Many goose species feed on agricultural land, and with growing goose numbers, conflicts with agriculture are increasing. One possible solution is to designate refuge areas where farmers are paid to leave geese undisturbed. Here, we present a generic modelling tool that can be used to designate the best locations for refuges and to gauge the area needed to accommodate the geese. With a species distribution model, locations are ranked according to goose suitability. The size of the area to be designated as refuge can be chosen by including more or less suitable locations. A resource depletion model is then used to estimate whether enough resources are available within the designated refuge to accommodate all geese, taking into account the dynamics of food resources, including depletion by geese. We illustrate this with the management scheme for pink-footed goose Anser brachyrhynchus implemented in Norway. Here, all geese can be accommodated, but damage levels appear to depend on weather, land use and refuge size.
Notes
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PubMed ID
28215007 View in PubMed
Less detail

Contrasting survival and physiological responses of sub-Arctic plant types to extreme winter warming and nitrogen.

https://arctichealth.org/en/permalink/ahliterature287137
Source
Planta. 2017 Nov 21;
Publication Type
Article
Date
Nov-21-2017
Author
Stef Bokhorst
Laura Jaakola
Katja Karppinen
Guro K Edvinsen
Hanne K Mæhre
Jarle W Bjerke
Source
Planta. 2017 Nov 21;
Date
Nov-21-2017
Language
English
Publication Type
Article
Abstract
Evergreen plants are more vulnerable than grasses and birch to snow and temperature variability in the sub-Arctic. Most Arctic climate impact studies focus on single factors, such as summer warming, while ecosystems are exposed to changes in all seasons. Through a combination of field and laboratory manipulations, we compared physiological and growth responses of dominant sub-Arctic plant types to midwinter warming events (6??C for 7?days) in combination with freezing, simulated snow thaw and nitrogen additions. We aimed to identify if different plant types showed consistent physiological, cellular, growth and mortality responses to these abiotic stressors. Evergreen dwarf shrubs and tree seedlings showed higher mortality (40-100%) following extreme winter warming events than Betula pubescens tree seedlings and grasses (0-27%). All species had growth reductions following exposure to -?20??C, but not all species suffered from -?10??C irrespective of other treatments. Winter warming followed by -?20??C resulted in the greatest mortality and was strongest among evergreen plants. Snow removal reduced the biomass for most species and this was exacerbated by subsequent freezing. Nitrogen increased the growth of B. pubescens and grasses, but not the evergreens, and interaction effects with the warming, freezing and snow treatments were minor and few. Physiological activity during the winter warming and freezing treatments was inconsistent with growth and mortality rates across the plants types. However, changes in the membrane fatty acids were associated with reduced mortality of grasses. Sub-Arctic plant communities may become dominated by grasses and deciduous plants if winter snowpack diminishes and plants are exposed to greater temperature variability in the near future.
PubMed ID
29164366 View in PubMed
Less detail

Contrasting survival and physiological responses of sub-Arctic plant types to extreme winter warming and nitrogen.

https://arctichealth.org/en/permalink/ahliterature293466
Source
Planta. 2018 Mar; 247(3):635-648
Publication Type
Journal Article
Date
Mar-2018
Author
Stef Bokhorst
Laura Jaakola
Katja Karppinen
Guro K Edvinsen
Hanne K Mæhre
Jarle W Bjerke
Author Affiliation
Norwegian Institute for Nature Research (NINA), FRAM - High North Research Centre for Climate and the Environment, Langnes, PO Box 6606, 9296, Tromsø, Norway. s.f.bokhorst@vu.nl.
Source
Planta. 2018 Mar; 247(3):635-648
Date
Mar-2018
Language
English
Publication Type
Journal Article
Keywords
Arctic Regions
Betula - metabolism - physiology
Festuca - metabolism - physiology
Freezing
Hot Temperature
Nitrogen - metabolism
Plant Physiological Phenomena
Poa - metabolism - physiology
Seasons
Temperature
Abstract
Evergreen plants are more vulnerable than grasses and birch to snow and temperature variability in the sub-Arctic. Most Arctic climate impact studies focus on single factors, such as summer warming, while ecosystems are exposed to changes in all seasons. Through a combination of field and laboratory manipulations, we compared physiological and growth responses of dominant sub-Arctic plant types to midwinter warming events (6 °C for 7 days) in combination with freezing, simulated snow thaw and nitrogen additions. We aimed to identify if different plant types showed consistent physiological, cellular, growth and mortality responses to these abiotic stressors. Evergreen dwarf shrubs and tree seedlings showed higher mortality (40-100%) following extreme winter warming events than Betula pubescens tree seedlings and grasses (0-27%). All species had growth reductions following exposure to - 20 °C, but not all species suffered from - 10 °C irrespective of other treatments. Winter warming followed by - 20 °C resulted in the greatest mortality and was strongest among evergreen plants. Snow removal reduced the biomass for most species and this was exacerbated by subsequent freezing. Nitrogen increased the growth of B. pubescens and grasses, but not the evergreens, and interaction effects with the warming, freezing and snow treatments were minor and few. Physiological activity during the winter warming and freezing treatments was inconsistent with growth and mortality rates across the plants types. However, changes in the membrane fatty acids were associated with reduced mortality of grasses. Sub-Arctic plant communities may become dominated by grasses and deciduous plants if winter snowpack diminishes and plants are exposed to greater temperature variability in the near future.
Notes
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PubMed ID
29164366 View in PubMed
Less detail

Impact of Multiple Ecological Stressors on a Sub-Arctic Ecosystem: No Interaction Between Extreme Winter Warming Events, Nitrogen Addition and Grazing.

https://arctichealth.org/en/permalink/ahliterature296783
Source
Front Plant Sci. 2018; 9:1787
Publication Type
Journal Article
Date
2018
Author
Stef Bokhorst
Matty P Berg
Guro K Edvinsen
Jacintha Ellers
Amber Heitman
Laura Jaakola
Hanne K Mæhre
Gareth K Phoenix
Hans Tømmervik
Jarle W Bjerke
Author Affiliation
Norwegian Institute for Nature Research, FRAM - High North Research Centre for Climate and the Environment, Tromsø, Norway.
Source
Front Plant Sci. 2018; 9:1787
Date
2018
Language
English
Publication Type
Journal Article
Abstract
Climate change is one of many ongoing human-induced environmental changes, but few studies consider interactive effects between multiple anthropogenic disturbances. In coastal sub-arctic heathland, we quantified the impact of a factorial design simulating extreme winter warming (WW) events (7 days at 6-7°C) combined with episodic summer nitrogen (+N) depositions (5 kg N ha-1) on plant winter physiology, plant community composition and ecosystem CO2 fluxes of an Empetrum nigrum dominated heathland during 3 consecutive years in northern Norway. We expected that the +N would exacerbate any stress effects caused by the WW treatment. During WW events, ecosystem respiration doubled, leaf respiration declined (-58%), efficiency of Photosystem II (Fv/Fm) increased (between 26 and 88%), while cell membrane fatty acids showed strong compositional changes as a result of the warming and freezing. In particular, longer fatty acid chains increased as a result of WW events, and eicosadienoic acid (C20:2) was lower when plants were exposed to the combination of WW and +N. A larval outbreak of geometrid moths (Epirrita autumnata and Operophtera brumata) following the first WW led to a near-complete leaf defoliation of the dominant dwarf shrubs E. nigrum (-87%) and Vaccinium myrtillus (-81%) across all experimental plots. Leaf emergence timing, plant biomass or composition, NDVI and growing season ecosystem CO2 fluxes were unresponsive to the WW and +N treatments. The limited plant community response reflected the relative mild winter freezing temperatures (-6.6°C to -11.8°C) recorded after the WW events, and that the grazing pressure probably overshadowed any potential treatment effects. The grazing pressure and WW both induce damage to the evergreen shrubs and their combination should therefore be even stronger. In addition, +N could have exacerbated the impact of both extreme events, but the ecosystem responses did not support this. Therefore, our results indicate that these sub-arctic Empetrum-dominated ecosystems are highly resilient and that their responses may be limited to the event with the strongest impact.
PubMed ID
30559757 View in PubMed
Less detail

Impacts of extreme winter warming events on plant physiology in a sub-Arctic heath community.

https://arctichealth.org/en/permalink/ahliterature96855
Source
Physiol Plant. 2010 May 21;
Publication Type
Article
Date
May-21-2010
Author
Stef Bokhorst
Jarle W Bjerke
Matthew P Davey
Kari Taulavuori
Erja Taulavuori
Kari Laine
Terry V Callaghan
Gareth K Phoenix
Author Affiliation
Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK.
Source
Physiol Plant. 2010 May 21;
Date
May-21-2010
Language
English
Publication Type
Article
Abstract
Insulation provided by snow cover and tolerance of freezing by physiological acclimation allows Arctic plants to survive cold winter temperatures. However, both the protection mechanisms may be lost with winter climate change, especially during extreme winter warming events where loss of snow cover from snow melt results in exposure of plants to warm temperatures and then returning extreme cold in the absence of insulating snow. These events cause considerable damage to Arctic plants, but physiological responses behind such damage remain unknown. Here, we report simulations of extreme winter warming events using infrared heating lamps and soil warming cables in a sub-Arctic heathland. During these events, we measured maximum quantum yield of photosystem II (PSII), photosynthesis, respiration, bud swelling and associated bud carbohydrate changes and lipid peroxidation to identify physiological responses during and after the winter warming events in three dwarf shrub species: Empetrum hermaphroditum, Vaccinium vitis-idaea and Vaccinium myrtillus. Winter warming increased maximum quantum yield of PSII, and photosynthesis was initiated for E. hermaphroditum and V. vitis-idaea. Bud swelling, bud carbohydrate decreases and lipid peroxidation were largest for E. hermaphroditum, whereas V. myrtillus and V. vitis-idaea showed no or less strong responses. Increased physiological activity and bud swelling suggest that sub-Arctic plants can initiate spring-like development in response to a short winter warming event. Lipid peroxidation suggests that plants experience increased winter stress. The observed differences between species in physiological responses are broadly consistent with interspecific differences in damage seen in previous studies, with E. hermaphroditum and V. myrtillus tending to be most sensitive. This suggests that initiation of spring-like development may be a major driver in the damage caused by winter warming events that are predicted to become more frequent in some regions of the Arctic and that may ultimately drive plant community shifts.
PubMed ID
20497369 View in PubMed
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11 records – page 1 of 2.