1. Department of Agroecology; Aarhus University; Slagelse Denmark
2. Department of Agronomy; Iowa State University; Ames Iowa USA
3. Global Change and Photosynthesis Research Unit; US Department of Agriculture-Agricultural Research Service; Urbana Illinois USA
4. School of Food and Agriculture; University of Maine; Orono Maine USA
5. Institute of Life Sciences; Scuola Superiore Sant'Anna; Pisa Italy
6. Department of Plant and Environmental Sciences; University of Copenhagen; Taastrup Denmark
7. Department of Applied Plant Research; Wageningen University and Research Centre; Lelystad The Netherlands
8. Department of Agriculture, Forest and Food Sciences; University of Torino; Grugliasco Italy