04 January, 2009

17. Not Seeing the Wood or the Trees

Prehistoric material culture was mostly made of wood, yet most archaeologists largely have studied the inorganic aspects of culture, since timber so rarely survives. However, it is still important to consider where the wood that we didn't find came from.

Woods can be beautiful and magical places, but in the past they produced most of the fuel and raw materials for material culture.

Archaeologists are concerned with evidence, so it is natural to think about and study what survives, and not to be too concerned about what does not. However, every posthole must have had a post that at some stage started out as a tree that grew somewhere; a posthole is evidence of a tree.
Visualising the past; A: The box rampart at Springfield Lyons, Essex, two lines of postholes curving from the right hand corner to towards the centre, with a partially excavated ditch to left [1]. B: The double thickness box rampart at Biskupin, Poland. [2].

The consistency with which stone and some metal artifacts are preserved has made them central to archaeological scholarship. Early archaeologists developed a framework for the past based on the development of tools, from stone to bronze, and then to iron.[3] It is easy to lose sight of the fact that most ‘cutting edge’ technology not used to kill things was used to process organic material, particularly wood. For the user, tools are a means to an end, and what is important is what is made with them.

The problem is that wooden items like buildings, fixtures and fittings, furniture, sculpture, basketry, the shafts of tools and weapons, bows, clogs, buttons and costume accessories, combs, toys, musical instruments, looms, ploughs, sledges, carts, wagons, boats, ships, and coffins are some of the rarest finds in archaeology. When you add in other rare organic survivors such as leather, fabrics, bone, horn, and items made from plant fibres and stems, it does not leave a great deal of material culture for archaeologists to study.

Wood is preserved in those environments where it is too wet, dry, cold, or salty for fungi and insects, and these are not necessarily typical places for human culture. The problem is not just that archaeologists do not find much wood, but that they usually do not think of the past in terms of timber. Most archaeological sites are fairly bleak areas of soil with holes in, and although many of the holes were dug to accommodate a piece of timber, this is often difficult to visualise.

Sites like Biskupin in Poland [2] are exceptional, not just for the preservation of timber, but for the survival of some clear sense of structural order. When you compare the massive wooden defences at Biskupin to the lines of postholes typically found on most archaeological sites, you can see why it is hard to relate the two images, and why the timber aspects of the past are a difficult image to paint on a canvas of postholes and pits.
Visualising the past; A: An area of the defences at Biskupin, Poland [2], all timber. B: The equivalent-sized area inside the defences at the hill-fort of Danebury, Hampshire, during excavation [3] , all pits and postholes
In a world of plastics and medium density fibreboard, wood is becoming increasingly remote from people's lives, and apart from a few hours of at school, most people no longer work with it. As it is so rarely found, understanding the nature of wood, and where it comes from, is not normally part of the archaeology syllabus, and it has remained the preserve of specialists and those few lucky enough to find it on a regular basis.

Prehistoric societies required large amounts of timber, in specific types, sizes, and quantities, and this largely had to be grown to order. If you need something on regular basis, especially something as heavy and bulky timber, it makes sense to grow it close to hand, from where it can be easily transported.

The evidence from waterlogged wood indicates that trees were being grown to order from the Neolithic period [5], and tree farming, or ‘silviculture’, must have been an essential part of the rural economy from then onwards.

A mature 0ak coppice with multiple trunks from a single 'stool'. (Sessile oak - quercus petraea)
Silviculture is essentially fairly simple, with a few basic methods like coppicing, a method of timber production utilising the natural processes of regeneration. When certain species of trees are cut down, they produce shoots from the stump that go on to become trunks, resulting in multiplicity of stems from one root system. This is a very efficient method of producing timber of a relatively small diameter in large quantities.

Consider the traditional method of growing willow for basket weaving [6]: In year 1, an area of ground is prepared, by digging over or ploughing, into which are planted 12-15 inch (0.3-0.4m) lengths of willow stem called ‘sets’, which will grow to become willow saplings. Since the new tree will be a clone of its parent, the sets are made from the best the willow stems or ‘withies’ available. They are planted about 0.4m apart in rows 0.60m apart, averaging 52,000 per hectare. The sets develop roots and grow in the spring, and some weeding is required.

Cutting withies from coppice stools [7]

In autumn and winter the stems are carefully cut with a hook-shaped tool, leaving a stump that will re-grow several stems in the following year. The initial yield of withies is poor, but the harvest improves with successive seasons. By the third year, the coppice stumps or ‘stools’ are well enough established to produce a crop of perhaps 6 tonnes of withies per hectare, and may continue to do this for many tens of years.

The other extreme of the woodland crop cycle is the production of timbers for building, which may be harvested every 50 – 100 years. These trees have to be planted or coppiced by previous generations for harvest by their decendants. The traditional building timber is English oak (Quercus robur), which can be coppiced or grown as a single tree or ‘standard’, depending on the size and shape of timber required.

A tall straight single oak or 'standard', about 50 years old , and ideal for prehistoric building, [Sessile oak - quercus petraea]
Professor Oliver Rackham, an expert on ancient woodland, has studied the close nature of the relationship between woodland, timber production and medieval buildings [8]. By a carefully cataloguing timbers in surviving medieval buildings it is possible to demonstrate how many and what type of trees were used in construction.
For example, Southchurch Hall in Southend on Sea, Essex, built around 1300 and now a museum [9], was once a not untypical medieval manor house with an open hall. It is estimated to contain 561 timber components representing 278 trees. Professor Rackham calculated that a wood of 18 hectares could produce the timber for such a building every 5 years [10]. This is an important point about medieval woods, that they contained trees of a variety of ages and sizes, and produced timber on a constant basis, and were not routinely clear felled as is happening in woods today.

Woods were an important economic asset, and were managed to produce a continuous supply of timber products. In the Domesday survey, drafted in 1086, about 15% of the land recorded was woodland. [11]

Woodlands take on an added economic significance as the principal source of fuel for heating, cooking, and industrial processes, especially in prehistory. To be fit for its purpose, firewood has to be cut and stored, usually for at least a year, to reduce its moisture content to the point where it burns efficiently. Gathering winter fuel on an ad hoc basis by picking up fallen dead wood is not an ideal strategy. What should be gathered in winter is the next year’s fuel, which you had the foresight to start growing several winters previously.

Mixed oak standards and coppice producing tall straight trees [Sessile oak - quercus petraea]
In addition to timber and fuel, woodlands provide places for hunting, for gathering foods, and foraging for stock. Woodland makes a significant contribution to any individual landholding, and in many respects, what is not produced in an estate’s fields, gardens, and orchards comes from its woods.
Although woodland and timber are largely invisible from the typical archaeological perspective, their vital and significant contribution to the prehistoric cultures we study should not be overlooked. The consideration of the nature and limitations of trees as a building material is important to understanding timber architecture, and is one of the central concerns in the methodology of theoretical structural archaeology.

More articles on trees and Woodland:

Vitruvius on Trees

Trees and Woodland:

References and Sources:
[1] Buckley D G, and Hedges J D, 1987. The Bronze Age and Saxon settlements at Springfield Lyons, Essex. Essex County Council, Occasional Paper No.5.
[2] http://www.muzarp.poznan.pl/muzeum/muz_pol/Arena/Biskupin/index_eng.html
[3] Cunliffe B, 1974 Iron Age Communities in Britain plate 6 Also:
Cunliffe B, 1994 Danebury Hampshire. In Fitzpatrick, A. and Morris, E. eds.. The Iron Age in Wessex: Recent Work. Salisbury: Trust for Wessex Archaeology. Pp 94-98 fig. fig 27.2 (Cunliffe, B. 1984 Danebury: an Iron Age Hillfort in HampshireVolume 1 The excavations, 1969 –1978: the site. CBA Research report 52)
[4] Christian Jürgensen Thomsen (1788–1865) , head of the National Museum in Denmark, developed the ‘three age system’ for classifying the collection of antiquities, it was later refined by Swedish archaeologist Oscar Montelius (1843 –1931).
[5] Coles, J.M and Orme, B.J 1977 "Neolithic Hurdles from Walton Heath, Somerset. Somerset Levels Project vol 3, 6-29
[6] Jenkins J G, 1978, Traditional country craftsmen, Routledge & Kegan Paul (pp 42 –52)
[7] Arnold J, 1968. The Shell book of country crafts. Baker, London. Plate 14
[8] Rackham, O, 1986. The ancient woodland of England: the woods of south-east Essex. Chapter 6 pp 40 –46
[9], Brown N, 2006: A Medieval Moated Manor by the Thames Estuary: Excavations at Southchurch Hall, Southend, Essex, , Essex. East Anglian Archaeology Report No.43.
Building & Museum at: http://www.southendmuseums.co.uk/southchurch/southchurch.htm
[10] Rackham, O, 1986. The ancient woodland of England: the woods of south-east Essex. table 3 p.44
[11] http://www.domesdaybook.co.uk/