First of all I would like to thank my supervisor Karl-Olof Bergman for rewarding discussions and all his help and encouragement during this study. I would also like to thank Anna Ringvall for her indispensable help with the statistics of power analyses, Christer and Jeanethe Alexis for allowing me to perform this study on their land, Ingemar Carlsson for showing me around the study area, and of course my family and friends.