1. Department of Civil and Environmental Engineering, Duke University, Box 90287, Durham, NC 27708‐0287, USA
2. Nicholas School of the Environment, Duke University, Box 90328, Durham, NC 27708, USA
3. Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, USA
4. Department of Terrestrial Ecosystem Research, University of Vienna, Althanstrasse 14, 1090 Austria
5. Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden