I love this stuff. From the wiki:
Alder a year later (trunk stool)
Typically a coppiced woodland is harvested in sections or coups on a rotation. In this way, a crop is available each year somewhere in the woodland. Coppicing has the effect of providing a rich variety of habitats, as the woodland always has a range of different-aged coppice growing in it, which is beneficial for biodiversity. The cycle length depends upon the species cut, the local custom, and the use to which the product is put. Birch can be coppiced for faggots on a three- or four-year cycle, whereas oak can be coppiced over a fifty-year cycle for poles or firewood.
Coppicing maintains trees at a juvenile stage, and a regularly coppiced tree will never die of old age—some coppice stools may therefore reach immense ages. The age of a stool may be estimated from its diameter, and some are so large—perhaps as much as 9 metres (30 ft) across—that they are thought to have been continuously coppiced for centuries.