Add to ORKGThis study was funded by my parents, Jane and Pip Harwood without whom it would not have been possible. I would like to thank them, both for the opportunity and for their limitless encouragement. This thesis is dedicated to their continuing happiness. I would also like to thank my supervisors Robert Muetzelfeldt and Graham Russell for their patience, motivation, joviality and invaluable critisism; Colin Legg for his heathland expertise and open door; John Grace for his ever relevant investigations; Alex Fiennes for his work on a visual interface for the model; my dearest love Amanda Edwards for her endless support and optimism; and all my colleagues at the Institute of Ecology and Resource Management for inspiration and advice. iii Growing ...