[1] NMSU, USDA ARS Jornada Expt Range, Las Cruces, NM 88003 USA
[2] US Geol Survey, Moab, UT 84532 USA
[3] CSIRO Ecosyst Sci, Atherton, Qld 4883, Australia
[4] Univ New Mexico, Dept Biol, Albuquerque, NM 87131 USA
[5] Univ Buenos Aires, IFEVA Fac Agron, RA-1417 Buenos Aires, DF, Argentina
[6] Univ Cape Town, Dept Bot, ZA-7701 Rondebosch, South Africa