Hearts of oak

One of the magic moments in the 2012 Olympics opening ceremony was the point when the giant oak tree standing on top of a grassy knoll soared high into the air. As its long roots dangled, a stream of workers emerged from the gaping hole it left behind and set about creating the belching chimneys of the industrial revolution that transformed the pastoral economy of Britain into the workshop of the world.

Oaks are symbolic of old England, just as they are of France and Germany in ages past. Our language is rich in references to their strength and endurance, longevity and steadfastness, summed up by the saying, ‘Mighty oaks from little acorns grow’. Oaks are the most royal of trees. In 1533 Queen Elizabeth I is reported to have been reading a book under an oak tree in Hatfield Park when a messenger arrived with the news that her sister Mary had died and she was now Queen. In 1651 King Charles II is said to have sheltered in the branches of an oak as he fled from the final battle of the Civil War.

The slow-growing oak can live for many centuries – perhaps as much as 1,200 years in the case of the famous oak of Pontfadog in north Wales. On the edge of Hayley Wood on the borders of Cambridgeshire and Bedfordshire is an oak tree dating back 400 years to the beginning of the Stuart age, a time of change and tumult that saw powerful political and religious factions pitted against each other.

This year Hayley Wood, one of the most important habitats for oxlips (a member of the Primula genus) in the country, celebrates its 50^th year as woodland owned by the Wildlife Trust for Bedfordshire, Cambridgeshire and Northamptonshire. The year 2012 also marks the 48^th anniversary of the connection between Hayley Wood and the Cambridge University ecologist and landscape historian, Professor Oliver Rackham.

Now a widely-acclaimed authority on woodlands, their history and habitats, Professor Rackham was just starting out on his academic career when he was approached to lend his support to the campaign that led to the purchase of the 120 acres of Hayley Wood for the sum of £5000. Underlying this purchase was the recognition of the special status of Hayley Wood (a designated Site of Special Scientific Interest) as ancient woodland and an important habitat for many species.

One of Professor Rackham’s research interests lies in the interplay of man and environment over the passing of time. Today we venerate oaks for their majesty and splendour – and for the delicate ecosystems they support – and tend to regard woodlands as areas that escape the pressure of agriculture and offer protection to wildlife. In the past woodlands were tied into the rural economy and often provided greater revenue for their owners than did arable land. Oaks, for example, provided a range of resources: timber for construction and ship-building, bark for tanning, acorns for fattening pigs, as well as firewood and wood for charcoal-making.

When back in the 1960s Professor Rackham began to research the history of Hayley Wood he discovered that it dates back at least 700 years; indeed the bank and ditches that surround it suggest that it may date back 1,000 years. One of many assets belonging to the Bishopric of Ely, it is listed in the Ely Coucher Book of 1251, a set of records commissioned by Bishop Hugo de Northwold, whose tomb stands near the high altar in Ely Cathedral. There is evidence within the wood of a hay field, a ridge and furrow system, and what might be farm buildings.

Contrary to public perception, the country has not lost substantial areas of woodland over the centuries. Moreover, the loss of ancient woodland has not been to the building of towns and roads, as we might think, but to the expansion of farmland and forestry. The threat to woodland today comes from deer and the globalisation of plant diseases. The effects of the ingression of deer (primarily muntjac, a species native to China) into Hayley Wood, and the consequent destruction of habitats, were so drastic that seven-eighths of the wood is now enclosed by fences with underpasses for badgers.

Professor Rackham’s work has developed an understanding of what has been dubbed the wood-wide-web of the mycorrhizal fungi that live on, and interconnect, the roots of trees and other plants. When he began his career it was thought that the tiny roots hairs of oaks supplied the tree with water and minerals. It’s now known that most of the job of the root-hairs is done by fungi that form the mycorrhiza. “Trees are dual organisms and it’s possible that this relationship goes back to the beginning of land plants. Humans too are dual organisms, of course, as we rely on bacteria in our gut to break down food,” he said. “Another feature of oaks that may go back many millions of years is the two flushes of growth they display over the summer – including the reddish-green Lammas leaves that appear around the start of August - which may date from a time when the climate was less seasonal and there was no winter.”

By visiting and revisiting Hayley Wood over decades, Professor Rackham has been able to track the ways in which the wood responds to subtle environmental changes through the passing of the seasons and shifts in weather patterns. In 1964 coppicing (the cutting of young stems back to near ground level) was reintroduced to the wood in order to encourage diversity. This system of cutting areas of the wood according on a rotation has enabled ecologists to study the ways in which the wood regenerates and observe the impact of changing levels of light on a range of species. During this time, Professor Rackham has led many visits to the wood to share his knowledge of its ecology both with other experts and members of the public. In a recent tour of wood with members of Cambridge Philosophical Society, he discussed how it had responded to a warm spring followed by an unusually wet summer.

In terms of recognition in the public arena, Professor Rackham’s The History of the Countryside (1986) helped raised the profile of indigenous woodlands, thus making a priceless contribution to the future preservation and management of green spaces. In it he shatters many of the unspoken assumptions that skew the way in which we see the countryside. He writes for example that “people regard trees anthropomorphically as ‘senile’ or ‘dying of old age’, as if they had a fixed life-span, and do not realise that hollow trunks and dead boughs are a normal part of a tree’s development”.