Preface

• Pasi Puttonen,
• Sauli Valkonen

Affiliations

Pasi Puttonen

University of Helsinki, Department of Forest Sciences, P.O. Box 27, FI-00014 University of Helsinki, Finland

Sauli Valkonen

Finnish Forest Research Institute, Vantaa Unit, P.O. Box 18, FI-01301 Vantaa, Finland