1. Department of Biometris; Wageningen University and Research Centre; Box 100 6700 AC Wageningen The Netherlands
2. Department of Mathematics; COMSATS Institute of Information Technology; Park Road Islamabad Pakistan
3. Alterra; Wageningen University and Research Centre; Box 47 6700 AA Wageningen The Netherlands
4. Experimental Plant Ecology; Radboud University Nijmegen; Toernooiveld 1 NL-6525 ED Nijmegen The Netherlands
5. Landscape Ecology Group; University of Oldenburg; Oldenburg 26111 Germany