Can see the wood for the trees

Being able to identify trees will soon be made a lot easier thanks to one of the county's leading nature sites. Different varieties of the same species growing in close proximity is a feature of the Oxfordshire Collection of Native Trees and Shrubs which is being established as an arboretum.

The woodland is being nurtured by the Oxfordshire Woodland Project and the Northmoor Trust, on whose Hill Farm site at Little Wittenham, close to Wittenham Clumps, it has been planted.

Its originator was the Woodland Project's first project officer, Ken Broad. His successor, David Rees, and Ben Philipps, forester at the Northmoor Trust, are sharing in the work.

Ken Broad worked on the design with the Northmoor Trust and took part in the planting in 1998. He retired the following year and died before he could see it come to full growth. His contribution will be marked at the site.

"Ken Broad recognised the need for landowners, ecologists, tree lovers and students of all ages to be able to study all the major native trees and shrubs of Oxfordshire in one location," said David.

"At eight years of age, the trees have occupied the design laid out for them, with great promise for glories to come."

The woodland project is a partnership of Oxfordshire County Council, and Cherwell, South Oxfordshire, Vale of White Horse and West Oxfordshire district councils and the Oxfordshire Woodland Group. Its aim is to foster a secure future for Oxfordshire's broadleaved woodland.

The woodland group has a membership of landowners, farmers and people in the forestry industry and is open to anybody with an interest in Oxfordshire's trees.

The project partners, with private benefactors, have contributed towards funding the arboretum. The group's annual meeting in September was held at Little Wittenham and members were able to visit the arboretum to see its progress.

The group met at the Project Timescape Education and Visitor Centre, another new venture of the Northmoor Trust, which is due to open in the spring. It is hoped that the opening of the arboretum will follow shortly afterwards.

The trust and the woodland group are fundraising to cover the cost of improving access to and around the arboretum, to install signs and produce educational materials.

Both David and Ben greatly appreciate Ken Broad's design, which David describes as having serpentine pathways that as a result have a very large frontage, just what is required in an arboretum.

Ben shares his enthusiasm. "The patterns make two hectares seem like ten hectares," he said. "It is excellent."

Along these routes, visitors will be able to see 43 different species of native trees and shrubs. Among them are the most familiar, such as oak, ash and beech, and shrubs of hazel and Guelder rose, with those less often noticed, such as the wild service tree, wayfaring tree, juniper, which is often seen in gardens but not so often in the countryside, and wild privet.

There are several species of willow, including the white, crack, bay and almond varieties. This less-known almond willow has proved the most difficult to establish. The willows, however, have been planted in one of the damper areas of the site, their favoured situation, and near the pond that is being created.

Black poplars, now quite rare in this country, were another planting not so easily established. But they now seem to be doing well, said Ben.

Each of the trees has been given plenty of space in which to thrive, Ben added, so that the more robust species do not crowd out others. Each species is represented by about 15 trees, which may in time have to be thinned out if the group becomes too dense.

The chosen site is suitable for most of these Oxfordshire species, with what is regarded as a fairly high-quality soil, and the sloping aspect that is preferable to one that is completely flat.

"It is allowing us to grow pretty well what we need," said David.

It has been considered important to include all the native species, where long-established introductions such as the sweet chestnut and sycamore, and the more recent arrivals in this country such as the walnut, are included. However, the sweet chestnut and the sycamore have been here for more than 2,000 years.

The seedstock for each has been found from local sources and nurseries have helped in this search.

"It took quite a bit of planning to gather suitable seed in the first instance and to track down suppliers," said David.

Now, eight years later, the trees are reaching heights of 10-12ft.

"They have grown to the stage where you can feel that you are walking beneath them," he is able to say.

One of the aims of Ken Broad was to show the range of native species and to help people to appreciate their woodland heritage. By seeing so many close together, they can make their own comparative studies of species.

Two which Ben Philipps points out are the oak, with its pendunculate and sessile species, and the white and downy versions of the birch.

"Even to some professionals the two varieties of birch are difficult to tell apart," he admitted.

There are also the contrasts between rapidity of growth and relative longevity. Examples to which he draws attention are the yew, slow-growing and able to live for a good many centuries, and the birch, which quickly reaches a good height but may live for only about 150 years.

The woodland has received a bonus in the springing up of ash seedlings from a nearby hedge and these are offering another educational opportunity. These seedlings are being welcomed, rather than being treated as intruders, for they will provide the means to introduce coppicing and illustrate this woodland practice.

It is likely that some will, as in the traditional way, be cut as rods for use as stakes and binders for hedgelaying, for which there is a good demand, and for gardening purposes, while others will be allowed to grow to their natural height.

An important benefit that the arboretum will bring is as a means of monitoring the effects of climate change on native species, and bringing them into focus.

Already, says Ben, there are concerns that the beech, so much a tree of South-East England, is becoming affected by the long periods of dry summer weather.

Climate change may also mean that some trees we have come to regard as typically at home in the British climate may not longer be suited to it, while others normally growing in countries further south will start to find our changing conditions to their liking.

This leads David to ask: "If English woodland habitats are being transformed by climate change, can we maintain our original confidence in the notion of native species?"

When the arboretum is formally launched, it will be open to both the general public and school groups.

"Visitors may simply come for the beauty of the trees, or maybe to sit and enjoy the extensive views of the Thames flood pain. Others might consider the relationship and tensions between 'nativeness' and impending climate change," said David.

Everybody who visits should be sure to find something of value to learn about our county's trees.

The Northmoor Trust is based at Hill Farm, Little Wittenham. Call 01865 407792 or visit the www.northmoortrust.co.uk website for details.