Jaana Laine and Jussi Leppänen for the valuable advice and many discussions that helped to improve this work. I would also like to thank the pre-examiners of this dissertation, professors Martin Moog and Jorma Sappinen for their valuable comments and suggestions, and professor Moog for also sharing his findings. The Finnish Forest Research Institute, or the Natural Resources Institute Finland from 2015 onwards, provided an inspiring intellectual environment and excellent facilities to pursue and complete this work. I wish to express my sincere thanks to all my colleagues in these two research institutions who by thought, time and labour have made the preparation and publication of this dissertation possible. The library personnel of the Finnish Forest Research Institute deserve special thanks for their help and advice. The wonderful libraries of the University of Helsinki, furnished with remarkable literature collections and retreat facilities for reading, thinking and learning, provided a special atmosphere and inspiration even on the hardest of days. A special thanks also to Stella Thompson, University of Helsinki, for revising the language of this dissertation. Above all, I owe an enormous debt to my family, Hannamari, Seliina and Helinä, who have encouraged me during the long process of writing this dissertation and patiently put up with my spending many evenings and weekends alone with books, articles and a computer. The most precious support for this work has originated from their sparkling minds and vivid curiosity that have been constant reminders of what intergenerational perspective, science and life are really about.