1. a Department of Environmental and Renewable Resources , Mediterranean Agronomic Institute of Chania , Chania, Alsyllio Agrokepion, PO Box 85, GR-73 100, Greece
2. b Department of Forestry and Natural Environment, Laboratory of Forest Management and Remote Sensing , Aristotle University of Thessaloniki , Box 248, Thessaloniki, 540 06, Greece E-mail: