title: Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time.
abstract: Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation - and associated ecosystem consequences - have the potential to be much greater than we have observed to date.
authors.affiliation: Department of Geography, University of British Columbia, Vancouver, Canada. sarah.elmendorf@geog.ubc.ca
authors.forename: Sarah C
authors.initials: SC
authors.lastname: Elmendorf
authors.forename: Gregory H R
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authors.lastname: Henry
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authors.initials: RD
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authors.forename: Járngerður
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authors.lastname: Grétarsdóttir
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authors.lastname: Harte
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authors.forename: David S
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authors.lastname: Hofgaard
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authors.lastname: Jarrad
authors.forename: Ingibjörg Svala
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authors.lastname: Jónsdóttir
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authors.lastname: Keuper
authors.forename: Kari
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authors.lastname: Klanderud
authors.forename: Julia A
authors.initials: JA
authors.lastname: Klein
authors.forename: Saewan
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authors.lastname: Koh
authors.forename: Gaku
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authors.lastname: Kudo
authors.forename: Simone I
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authors.forename: Jeremy L
authors.initials: JL
authors.lastname: May
authors.forename: Joel
authors.initials: J
authors.lastname: Mercado
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authors.lastname: Michelsen
authors.forename: Ulf
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authors.lastname: Molau
authors.forename: Isla H
authors.initials: IH
authors.lastname: Myers-Smith
authors.forename: Steven F
authors.initials: SF
authors.lastname: Oberbauer
authors.forename: Sara
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authors.lastname: Pieper
authors.forename: Eric
authors.initials: E
authors.lastname: Post
authors.forename: Christian
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authors.lastname: Rixen
authors.forename: Clare H
authors.initials: CH
authors.lastname: Robinson
authors.forename: Niels Martin
authors.initials: NM
authors.lastname: Schmidt
authors.forename: Gaius R
authors.initials: GR
authors.lastname: Shaver
authors.forename: Anna
authors.initials: A
authors.lastname: Stenström
authors.forename: Anne
authors.initials: A
authors.lastname: Tolvanen
authors.forename: Orjan
authors.initials: O
authors.lastname: Totland
authors.forename: Tiffany
authors.initials: T
authors.lastname: Troxler
authors.forename: Carl-Henrik
authors.initials: CH
authors.lastname: Wahren
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Webber
authors.forename: Jeffery M
authors.initials: JM
authors.lastname: Welker
authors.forename: Philip A
authors.initials: PA
authors.lastname: Wookey
mesh_terms: D000220:Adaptation, Biological; D001110:Arctic Regions; D044822:Biodiversity; D017753:Ecosystem; D057232:Global Warming; D008954:Models, Biological; D063245:Plant Development