Authors: F Stuart Chapin; Amy L Lovecraft; Erika S Zavaleta; Joanna Nelson; Martin D Robards; Gary P Kofinas; Sarah F Trainor; Garry D Peterson; Henry P Huntington; Rosamond L Naylor Journal: Proc Natl Acad Sci U S A Date: 2006-09-28 Impact factor: 11.205