Ancient woods were very valuable properties for their owners, as a source of wood fuel, timber (estovers and loppage) and forage for pigs (pannage). Hazel was grown for coppicing, the branches being used for wattle and daub in buildings, for example. Such old coppice stumps are easily recognised for their current overgrown state, now that the practice has largely disappeared. Ancient woods were frequently Royal Parks and hunting grounds and given special protection against poachers, for example. The forest law was very strictly enforced, although various ancient rights to collect firewood are still extant. In English law, it was illegal to assart any part of a royal forest. This was the greatest trespass that could be committed in a forest, being more than a waste: for whereas waste of the forest involves felling trees, they can grow again; assarting involves completely rooting up all trees — the total removal of the forested area. Ancient woods were well-defined, often being surrounded by a bank and ditch, so that they could be easily recognised. Such indicators can still be seen in many ancient woodlands. Many ancient woods are described in the Domesday Book, as well as the Anglo-Saxon Chronicles, such was their value to early communities. Coppicing is a traditional method of woodland management which takes advantage of the fact that many trees make new growth from the stump or roots if cut down. In a coppiced wood, young tree stems are repeatedly cut down to near ground level. In subsequent growth years, many new shoots will emerge, a d, after a number of years the coppiced tree, or stool, is ready to be harvested, and the cycle begins again. (The noun "coppice" means a growth of small trees or a forest coming from shoots or suckers.) Typically a coppiced woodland is harvested in sections or coups[1] 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 (bundles of brushwood) 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 5.4 metres (18 ft) across—that they are thought to have been continuously coppiced for centuries.[2] Coppiced stems are characteristically curved at the base. This curve occurs as the competing stems grow out from the stool in the early stages of the cycle, then up towards the sky as the canopy closes. The curve may allow the identification of coppice timber in archaeological sites—timber in the Sweet Track in Somerset (built in the winter of 3807 and 3806 BC) has been identified as coppiced lime.