Forest management changes the forest structure and affects the biodiversity. Managed forests regenerated after clear-cuts show a small variation in age and sizes of the trees. Furthermore, the amount and diversity of dead wood are small. Forests regenerated after selective logging have a structure that resembles old-growth forests.
Old-growth boreal forest displays a heterogeneous age and size structure together with a larger amount of dead wood. Such, naturally regenerated forest are often referred to as natural forests. The gradient of naturalness from old managed to old-growth is important in forest biodiversity management and the definition of natural forest are on that gradient.