[1] Univ British Columbia, Dept Geog, Vancouver, BC V6T 1Z2, Canada
[2] Univ Alaska Fairbanks, Boreal Ecol Cooperat Res Unit, US Dept Agr Forest Serv Pacific NW Res Stn, Fairbanks, AK 99775 USA
[3] La Trobe Univ, Dept Agr Sci, Bundoora, Vic 3086, Australia
[4] Grand Valley State Univ, Dept Biol, Allendale, MI 49401 USA
[5] Florida Int Univ, Dept Biol Sci, Miami, FL 33199 USA
[6] Univ Gothenburg, Inst Bot, SE-40530 Gothenburg, Sweden
[7] Univ Alaska Fairbanks, Inst Arctic Biol, Fairbanks, AK 99775 USA
[8] Univ Virginia, Dept Environm Sci, Charlottesville, VA 22904 USA
[9] Abisko Sci Res Stn, S-98107 Abisko, Sweden
[10] Colorado State Univ, Nat Resource Ecol Lab, Ft Collins, CO 80523 USA
[11] Iceland Inst Nat Hist, Reykjavik, Iceland
[12] Michigan State Univ, Dept Forestry, E Lansing, MI 48824 USA
[13] Kings Coll London, Dept Life Sci, London SE1 9NN, England
[14] Marine Biol Lab, Ctr Ecosyst, Woods Hole, MA 02543 USA
[15] Univ Calif Irvine, Dept Ecol & Evolutionary Biol, Irvine, CA 92697 USA
[16] Finnish Forest Res Inst, Muhos 91500, Finland
[17] Norwegian Univ Life Sci, Dept Ecol & Nat Resource Management, N-1432 As, Norway
[18] Univ Colorado, Inst Arct & Alpine Res, Boulder, CO 80309 USA
[19] Univ Texas, Dept Biol, El Paso, TX 79968 USA
[20] Univ Texas, Environm Sci & Engn Program, El Paso, TX 79968 USA
[21] Michigan State Univ, Dept Plant Biol, E Lansing, MI 48824 USA
[22] Univ Stirling, Sch Biol & Environm Sci, Stirling FK9 4LA, Scotland