After clear cutting, tops and branches from felled trees are traditionally left on site together with small trees (Fig. 8). On nutrient-limited sites this slash should not be removed because that would reduce the nutrients present on site. The amount of biomass present in tops and branches is estimated to amount to 20-30 % of the total harvest. The supply of biomass from tops and branches is the main source of bioenergy production in Sweden.

2. Fast-growing species

Besides conventional forestry management, there is increasing interest in management of so — called fast-growing species. Depending on geographical location, different species can be considered fast-growing. There are at least three types of tree suitable and frequently used for management in Europe, the USA and Canada: Salix clones, poplar and hybrid aspen. In areas with higher temperatures than northern Europe, species of Eucalyptus are also planted.