HelbigChasmerDesaiEtAl2017

Référence

Helbig, M., Chasmer, L.E., Desai, A.R., Kljun, N., Quinton, W.L. and Sonnentag, O. (2017) Direct and indirect climate change effects on carbon dioxide fluxes in a thawing boreal forest–wetland landscape. Global Change Biology, 23(8):3231-3248. (Scopus )

Résumé

In the sporadic permafrost zone of northwestern Canada, boreal forest carbon dioxide (CO2) fluxes will be altered directly by climate change through changing meteorological forcing and indirectly through changes in landscape functioning associated with thaw-induced collapse-scar bog (‘wetland’) expansion. However, their combined effect on landscape-scale net ecosystem CO2 exchange (NEELAND), resulting from changing gross primary productivity (GPP) and ecosystem respiration (ER), remains unknown. Here, we quantify indirect land cover change impacts on NEELAND and direct climate change impacts on modeled temperature- and light-limited NEELAND of a boreal forest–wetland landscape. Using nested eddy covariance flux towers, we find both GPP and ER to be larger at the landscape compared to the wetland level. However, annual NEELAND (−20 g C m−2) and wetland NEE (−24 g C m−2) were similar, suggesting negligible wetland expansion effects on NEELAND. In contrast, we find non-negligible direct climate change impacts when modeling NEELAND using projected air temperature and incoming shortwave radiation. At the end of the 21st century, modeled GPP mainly increases in spring and fall due to reduced temperature limitation, but becomes more frequently light-limited in fall. In a warmer climate, ER increases year-round in the absence of moisture stress resulting in net CO2 uptake increases in the shoulder seasons and decreases during the summer. Annually, landscape net CO2 uptake is projected to decline by 25 ± 14 g C m−2 for a moderate and 103 ± 38 g C m−2 for a high warming scenario, potentially reversing recently observed positive net CO2 uptake trends across the boreal biome. Thus, even without moisture stress, net CO2 uptake of boreal forest–wetland landscapes may decline, and ultimately, these landscapes may turn into net CO2 sources under continued anthropogenic CO2 emissions. We conclude that NEELAND changes are more likely to be driven by direct climate change rather than by indirect land cover change impacts. © 2017 John Wiley & Sons Ltd

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@ARTICLE { HelbigChasmerDesaiEtAl2017,
    AUTHOR = { Helbig, M. and Chasmer, L.E. and Desai, A.R. and Kljun, N. and Quinton, W.L. and Sonnentag, O. },
    TITLE = { Direct and indirect climate change effects on carbon dioxide fluxes in a thawing boreal forest–wetland landscape },
    JOURNAL = { Global Change Biology },
    YEAR = { 2017 },
    VOLUME = { 23 },
    NUMBER = { 8 },
    PAGES = { 3231-3248 },
    NOTE = { cited By 3 },
    ABSTRACT = { In the sporadic permafrost zone of northwestern Canada, boreal forest carbon dioxide (CO2) fluxes will be altered directly by climate change through changing meteorological forcing and indirectly through changes in landscape functioning associated with thaw-induced collapse-scar bog (‘wetland’) expansion. However, their combined effect on landscape-scale net ecosystem CO2 exchange (NEELAND), resulting from changing gross primary productivity (GPP) and ecosystem respiration (ER), remains unknown. Here, we quantify indirect land cover change impacts on NEELAND and direct climate change impacts on modeled temperature- and light-limited NEELAND of a boreal forest–wetland landscape. Using nested eddy covariance flux towers, we find both GPP and ER to be larger at the landscape compared to the wetland level. However, annual NEELAND (−20 g C m−2) and wetland NEE (−24 g C m−2) were similar, suggesting negligible wetland expansion effects on NEELAND. In contrast, we find non-negligible direct climate change impacts when modeling NEELAND using projected air temperature and incoming shortwave radiation. At the end of the 21st century, modeled GPP mainly increases in spring and fall due to reduced temperature limitation, but becomes more frequently light-limited in fall. In a warmer climate, ER increases year-round in the absence of moisture stress resulting in net CO2 uptake increases in the shoulder seasons and decreases during the summer. Annually, landscape net CO2 uptake is projected to decline by 25 ± 14 g C m−2 for a moderate and 103 ± 38 g C m−2 for a high warming scenario, potentially reversing recently observed positive net CO2 uptake trends across the boreal biome. Thus, even without moisture stress, net CO2 uptake of boreal forest–wetland landscapes may decline, and ultimately, these landscapes may turn into net CO2 sources under continued anthropogenic CO2 emissions. We conclude that NEELAND changes are more likely to be driven by direct climate change rather than by indirect land cover change impacts. © 2017 John Wiley & Sons Ltd },
    AFFILIATION = { Département de géographie & Centre d’études nordiques, Université de Montréal, 520 Chemin de la Côte Sainte-Catherine, Montréal, QC, Canada; Department of Geography, University of Lethbridge, Lethbridge, AB, Canada; Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, WI, United States; Department of Geography, Swansea University, Singleton Park, Swansea, United Kingdom; Cold Regions Research Centre, Wilfrid Laurier University, Waterloo, ON, Canada },
    AUTHOR_KEYWORDS = { boreal forest; carbon dioxide; climate change; ecosystem respiration; eddy covariance; gross primary productivity; permafrost; wetlands },
    DOCUMENT_TYPE = { Article },
    DOI = { 10.1111/gcb.13638 },
    SOURCE = { Scopus },
    URL = { https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013997063&doi=10.1111%2fgcb.13638&partnerID=40&md5=fadcc4937f30f9e68779ed1716fde970 },
}

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