1. Ecophysiology of Plants, Institute of Environmental Biology, PO Box 800.84, NL–3508 TB Utrecht, The Netherlands;
2. Department of Plant Physiology, Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Kreutzwaldi 1, Tartu EE–51014, Estonia;
3. Forest Ecology and Forest Management Group and Resource Ecology Group, Centre for Ecosystem Studies, Wageningen University, PO Box 47, NL–6700 AA Wageningen, The Netherlands;
4. Department of Biological Sciences, Macquarie University, New South Wales 2109, Australia;
5. Área de Ecología, Campus de Rabanales, Universidad de Córdoba, ES–14071 Córdoba, Spain