Blar i forfatter "Welker, Jeffrey"

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    • Growth rings show limited evidence for ungulates’ potential to suppress shrubs across the Arctic 

      Vuorinen, Katariina Elsa Maria; Austrheim, Gunnar; Tremblay, Jean-Pierre; Myers-Smith, Isla H.; Hortman, Hans Ivar; Frank, Peter; Barrio, Isabel C.; Dalerum, Fredrik; Björkman, Mats Peter; Björk, Robert G.; Ehrich, Dorothee; Sokolov, Aleksandr; Sokolova, Natalya; Ropars, Pascale; Boudreau, Stephane; Normand, Signe; Prendin, Angela L.; Schmidt, Niels Martin; Pacheco-Solana, Arturo; Post, Eric; John, Christian; Kerby, Jeff; Sullivan, Patrick F.; Le Moullec, Mathilde; Hansen, Brage Bremset; van der Wal, René; Pedersen, Åshild Ønvik; Sandal, Lisa; Gough, Laura; Young, Amanda; Li, Bingxi; Magnusson, Runa I.; Sass-Klaassen, Ute; Buchwal, Agata; Welker, Jeffrey; Grogan, Paul; Andruko, Rhett; Volkovitskiy, Alexander; Terekhina, Alexandra; Speed, James David Mervyn (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-22)
      Global warming has pronounced effects on tundra vegetation, and rising mean temperatures increase plant growth potential across the Arctic biome. Herbivores may counteract the warming impacts by reducing plant growth, but the strength of this effect may depend on prevailing regional climatic conditions. To study how ungulates interact with temperature to influence growth of tundra shrubs across ...

    • Large loss of CO2 in winter observed across the northern permafrost region 

      Natali, Susan M.; Watts, Jennifer D.; Rogers, Brendan M.; Potter, Stefano; Ludwig, Sarah M.; Selbmann, Anne-Katrin; Sullivan, Patrick F.; Abbott, Benjamin W.; Arndt, Kyla A.; Birch, Leah; Björkman, Mats P.; Bloom, A. Anthony; Celis, Gerardo; Christensen, Torben R.; Christiansen, Casper Tai; Commane, Roisin; Cooper, Elisabeth J.; Crill, Patrick; Czimczik, Claudia; Davydov, Sergey; Du, Jinyang; Egan, Jocelyn E.; Elberling, Bo; Euskirchen, Eugenie S.; Friborg, Thomas; Genet, Hélène; Göckede, Mathias; Goodrich, Jordan P.; Grogan, Paul; Helbig, Manuel; Jafarov, Elchin E.; Jastrow, Julie D.; Kalhori, Aram A. M.; Kim, Yongwon; Kimball, John S.; Kutzbach, Lars; Lara, Mark J.; Larsen, Klaus S.; Lee, Bang-Yong; Liu, Zhihua; Loranty, Michael M.; Lund, Magnus; Lupascu, Massimo; Madani, Nima; Malhotra, Avni; Matamala, Roser; McFarland, Jack; McGuire, A. David; Michelsen, Anders; Minions, Christina; Oechel, Walter C.; Olefeldt, David; Parmentier, Frans-Jan W.; Pirk, Norbert; Poulter, Ben; Quinton, William; Rezanezhad, Fereidoun; Risk, David; Sachs, Torsten; Schaefer, Kevin; Schmidt, Niels M.; Schuur, Edward A. G.; Semenchuk, Philipp R.; Shaver, Gaius; Sonnentag, Oliver; Starr, Gregory; Treat, Claire C.; Waldrop, Mark P.; Wang, Yihui; Welker, Jeffrey; Wille, Christian; Xu, Xiaofeng; Zhang, Zhen; Zhuang, Qianlai; Zona, Donatella (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-10-21)
      Recent warming in the Arctic, which has been amplified during the winter, greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO<sub>2</sub>). However, the amount of CO<sub>2</sub> released in winter is not known and has not been well represented by ecosystem models or empirically based estimates. Here we synthesize regional in situ observations ...

    • Shrub expansion in tundra ecosystems : dynamics, impacts and research priorities 

      Myers-Smith, Isla; Forbes, Bruce C.; Wilmking, Martin; Hallinger, Martin; Lantz, Trevor; Blok, Daan; Tape, Ken D; Ravolainen, Virve; Macias-Fauria, Marc; Sass-Klaassen, Ute; Levesque, Esther; Boudreau, Stephane; Ropars, Pascale; Hermanutz, Luise; Trant, Andrew; Collier, Laura Siegwart; Weijers, Niels Martin; Rozema, Jelte; Rayback, Shelly A; Schmidt, Niels Martin; Schaepman-Strub, Gabriela; Wipf, Sonja; Rixen, Christian; Menard, Cecile B; Venn, Susanna; Goetz, Scott; Andreu-Hayles, Laia; Elmendorf, Sarah; Welker, Jeffrey; Grogan, Paul; Epstein, Howard E.; Hik, David S. (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      Recent research using repeat photography, long-term ecological monitoring and dendrochronology has documented shrub expansion in arctic, high-latitude and alpine tundra ecosystems. Here, we (1) synthesize these findings, (2) present a conceptual framework that identifies mechanisms and constraints on shrub increase, (3) explore causes, feedbacks and implications of the increased shrub cover in tundra ...