Even though most of the biomass of the planet is in forests, we live in a world where wood as a raw material and its products are increasingly scarce. This is particularly so in important areas such as the European Community, which is far from self-sufficient in terms of wood. In recent years the need to intensify forest production and, in some cases, to uti lize abandoned agricultural land for forestry has focussed world-wide attention on the economic importance of fast-growing tree plantations. These are usually managed as short "rotations" (growing cycles) of less than 15 years, often for...