Bog oaks

Anyone venturing off the main roads around Bourne and into the narrow fenland lanes will encounter many roadside piles of wooden logs, distorted in shape and discoloured grey-black with age because they are indeed relics from the dim and distant past.

These ancient timbers that have been preserved in wetlands such as the fens around Bourne for several millenia have become known as bog oaks, although they can also be yew or pine. Many massive specimens have been turned up by the plough, some up to 40 feet long, and discarded at a safe distance in order not to hamper future farming operations.

They are the remains of the forest that existed here after the Ice Ages, the trees rotting and eventually falling into the peat soil and their recovery provides a snapshot of ancient natural history.

The British Isles were once part of the continental land mass and the rivers of eastern England tributaries of the River Rhine. Around 12,000 years ago, during the Ice Ages, the Arctic caps spread southwards as far as the Thames valley and 2,000 years later, as the ice began to melt, low lying areas of land flooded and created freshwater lakes and swamps.

For the next four thousand or so years, these Neolithic wetlands teemed with plant life. Great oak forests evolved between the lakes and over time fallen trees and vegetation composted down to form nutrient rich soils. Some of the trees and branches fell into the lakes and ponds and sank to the bottom and in these dark, airless conditions the timbers were preserved from decay by the acidic and anaerobic bog for hundreds and even thousands of years. The wood is usually stained brown by tannins dissolved in the acidic water and bog wood represents the early stages in the fossilisation of wood, eventually forming lignite and coal over a period of many millions of years.

From time to time, the preserved timbers reach the earth's surface like spirits from the past to remind us of what was once here. Although these fossilised trees are known by the local name of bog oaks they can be any species growing naturally near or in bogs including yew, pine and swamp cypress. They are the legacy of this wet low lying land frequently revealed as farmers plough deeper each year and throwing up huge sections of preserved tree trunks in these fertile acres, so large that in past times a special device was attached to the plough to release the horse whenever the blade struck one and some were so large that several horses were needed to pull them from the ground.

Many can still be seen in fen areas where they have been hauled clear of the field and abandoned on the grass verge at the roadside and during the 19th century, these finds were no numerous that farmers cut them up and used the wood to build fences and even today, many people collect sections to decorate their rockeries and as garden ornaments.

The ancient forests that could be found in these parts were home to many species of wild animals whose remains have also been found such as bones, horns and antlers and particularly the teeth of mammoths, one so large being recovered from the gravel pits around Deeping St James, near Bourne, that it was used for many years by a family as a door stop.

REVISED JUNE 2013

MORE BOG OAKS
Bog oaks abandoned by the roadside after being turned up by the plough in the North Fen at Bourne in 1992 (above) and more piles near Dyke village (below).
More bog oaks can be found at the roadside in the South Fen at Bourne (above and below).