1. Institute of Grassland Science Key Laboratory of Vegetation Ecology of the Ministry of Education Jilin Songnen Grassland Ecosystem National Observation and Research Station Northeast Normal University Changchun China
2. Institute of Ecology College of Urban and Environmental Science, and Key Laboratory for Earth Surface Processes of the Ministry of Education Peking University Beijing China
3. Division of Biology Kansas State University Manhattan KS USA
4. Department of Botany University of Wyoming Laramie WY USA
5. Department of Biology University of New Mexico Albuquerque NM USA