Managing a Woodland
Good management of specially preserved areas of woodland (such as Wyre Forest), marsh and heath can provide valuable havens for many of Britain’s wildlife species.
Places set aside specially for the study of wild-life are known as nature reserves and may take several forms. Some are looked after by County Councils and are known as local nature reserves, while others are in the care of the County Naturalists’ Trusts and are bought with the help of members’ subscriptions, as are the reserves run by the RSPB. The government agencies responsible for conservation are English Nature. Scottish Natural Heritage. And the Countryside Council for Wales, which. As well as managing reserves, also commission research into various aspects of conservation. While some reserves are acquired in order to protect rare plants or animals, most have a comprehensive range of species which typify a particular habitat.
Managing a forest
The Wyre Forest National Nature Reserve in the West Midlands is a large area of oak woodland and coniferous plantations, among which are numerous old meadows and orchards. A trout stream runs through the valley into the River Severn nearby, and a disused railway track also runs through the forest.
Most of the oak woodland is of an even-age structure. The coppice areas where charcoal burning and bark peeling once thrived are long since abandoned. To introduce a more mixed woodland age structure, the oak is thinned to let in more light and allow other species of trees, such as birch and wild service, to regenerate. This may be standard forestry thinning, or an experimental type where various techniques are tried in order to favour trees which will be growing on well when the final crop of larger or more mature trees is felled. These techniques require heavy tree handling and are carried out by skilled contractors. The felled trees are usually converted into fence stakes or planking timber. If large enough; this will often pay for the work and provide a financial return for the owner. It helps if. In certain areas, an extra tree or two is removed to create a glade. Where regeneration of oak. Birch and heather will be much quicker, because of the extra light admitted. If possible, a few trees are ring-barked, causing them to die and thus provide a valuable dead wood habitat. They may also be simply felled and left to die and rot where they fall.
Certain species of birds can be attracted if nest sites are provided. If there are few natural nest holes, interesting species such as the redstart and the pied flycatcher readily use the nest boxes erected in the woodlands and orchards. In areas where oak coppice growth is favoured, the younger stems may be cut and sold locally for use as bean sticks or for making rustic furniture, leaving a stem or two on each stump as possible future trees. These older poles may be sold as firewood.
Many of the thicker and even-aged oak woods are relatively devoid of interest deep inside; they often have a ground flora consisting mainly of bracken. A much more diverse range of insects and plants occurs, however, on the edges – here such species as bramble, hawthorn and rose form thickets in a dense border. A wide ride cut through a wood will create two such new edges, and this can give a great boost to the variety of species within the forest, provided not too much timber is removed in the process. Butterflies especially welcome these sheltered flyways, and such plants as bugle thrive.
The woodland edge is really a scrub habitat and scrub is also found in other parts of the reserve. It is important for different groups of plants and animals at varying stages of its development. For example, warblers may need small blackthorn bushes of five years old or so in which to breed, whereas hairstreak butterflies need much older bushes on which to lay their eggs. While silver-washed fritillary butterflies prefer to obtain nectar from bramble blossoms. Good management must therefore ensure that such areas remain – but only so long as other species needing an open habitat do not surfer in the process. In a large area such as Wyre Forest, however, it is possible to maintain some of each habitat.
The best example of a scrub habitat within the forest is that growing on the banks of the old railway track: being in linear form it is easy to split up into sections and manage on rotation. By cutting at different times, a complete range of age structures can be achieved. So that at any one time there is at least one area of each scrubland age group, up to a maximum of about 20 years old. Being of no commercial value, the work of cutting out the bushes must usually be done by volunteers.
Other scrub may be managed in a way that keeps the particular area in a static age class. This is done by removing all bushes except those in the age or size group required. Hedgerows in the reserve, which belong to the scrub group, are managed by being ‘laid’ in the traditional way; this too is done on a rotational basis. It is a skilled and time-consuming job but produces a worthwhile result, areas of heather or gorse. If they need to be cut or removed, are treated with a tractor and rear mounted ‘swipe’. This, a circular-motion mower using either blades or chains as the cutting edge, handles quite large stems.
It is difficult to imagine the small scattered meadows of Wyre Forest as part of the forest habitat, but after existing for hundreds of years they are an extremely valuable part of the woodland mosaic. Many species of butterfly need the woodland violet on which to lay their eggs, and thewhich grow in the old meadows also provide a source of nectar for the adults. The large mounds or ‘tumps’ of the meadow ant. Too, are a common feature of these small fields. And provide a valuable part of the diet of such birds as the green woodpecker. Combined with the meadows there are orchards, now becoming derelict, with old, gnarled or fallen trees, usually full of holes and crannies which are useful for wildlife. These fruit trees are usually the now rare old varieties of cider apple or perry pear, which are replaced wherever possible.
The meadows would soon form into scrub if they were not managed. Management is done in two of the oldest and most traditional ways known – grazing with cattle and cutting for hay. The cattle could be a problem because of the remoteness of some of the small fields. But fortunately there is a farmer quite near who is willing to drive his animals through the forest. They are removed in the spring when some of the meadow blooms appear – cowslips and green-winged orchids in particular. The adder’s-tongue fern can also be found in spring, while the meadow saffron blooms in the autumn. After the hay has been cut in the summer, the cattle return. The hay cutting prevents the build-up of dead litter just above ground level and encourages the meadow flora, as does the fact that no chemical fertilisers are used.
Some of the more remote fields, however. Are inaccessible and so cannot be treated in this way. They are cut with a mower and then raked. Horse grazing, when carried out sporadically, can provide an alternative to the better methods, but if too heavy or prolonged may cause damage. One or two areas in the forest display a wealth of blooms – betony, meadowsweet, knapweed, trefoils, marsh thistle and many others – as a result of light grazing by one or two horses.
One feature not met with often in the forest is ponds or areas of static water. A number of streams run through the steep-sided valleys, however, and most of the few ponds in Wyre Forest have been made by erecting a dam across such a valley. One pool created in this way holds a number of fishes, including roach, perch and carp.
The streams themselves require little looking after, but the trees that grow alongside are managed. One of the most common stream-side trees is the alder, which provides a home for such tree-boring insects as the rare alder wood wasp. This insect requires quite thin stems of alder in which to lay its eggs – coppicing of the trees provides a flush of new growth that meets this requirement.
This does not mean that long stretches of alder are removed: instead only a few odd trees are cut. If too many trees were removed more light would fall on the water and could upset the ecology of the streams, especially the larger ones. As it bubbles over rocks and stones through its mainly sheltered tunnel of trees. The temperature is kept low, and much oxygen is thus dissolved. This provides just the right conditions for many aquatic species – mayflies and caddis flies and their larvae, and fishes such as trout, bullhead, loach and lamprey. Crayfish are common and provide food for a pest species which has moved into the area recently, the mink. This mammal is kept down to an acceptable level by trapping. This procedure is necessary since the mink’s numbers could rise to pest proportions, to the detriment of other wildlife in the forest.
Timber and Its Products
Timber is the most valuable of all our natural resources. From fuel and building materials to tools, furniture and paper, we use timber for so many different purposes that it is almost impossible to imagine life without it.
Although all parts of a tree have their uses. Commercially its most important part by far is its wood. Of all the timber felled in the world, about half is used for fuel in the form of logs or charcoal, much of it in the tropics and the Third World countries. The rest is used as timber or processed wood – plywood, chipboard and pulp.
A quick look at the wooden items found in a house soon shows that wood is not a uniform material but extremely variable, differing in pattern, colour and hardness. The most basic difference is between the wood of conifers. Such as pines and cedars, which is called ‘softwood’. And that of the flowering trees (beech. Oak and so forth), which is called ‘hardwood’. However, these terms are confusing since they refer only in the most general way to the strength and durability of the two groups. For example, the softest, lightest wood is the ‘hardwood’ balsa, along with certain true ‘softwoods’, such as spruce.
When looked at in cross-section, a tree trunk contains several different layers. On the outside is the protective bark: inside is the food-conducting phloem: inside that is a thin layer of cambium where the trunk forms new cells: then comes the water-conducting wood, the xylem. And in the centre is dead xylem, the heartwood.
For timber, the most important parts of a tree are the xylem and the heartwood. The xylem contains several types of cell, occurring in varying amounts in different species of tree. The differences between hardwoods and softwoods are due to the fact that they contain different types of cells. In hardwoods, the most important component is the vessels, which consist of tubular cells placed end to end to act as a passage for minerals and water. Surrounding these in most hardwoods are fibre cells – long, thin, tapered cells with extremely thick walls, which provide the vessels with a supporting matrix. The variation in hardness between the different hardwoods is due mainly to the properties of these two groups of cells. In balsa, for example, the fibre cells have thin walls and the vessels are large and closely spaced. On the other hand, ebony, which is one of the hardest and heaviest woods, has thick-walled fibre cells with small, widely spaced vessels, which are often made harder by extremely tough deposits of gum in the middle of the cells.
Most species of hardwood trees have a third component called wood parenchyma. These are thin-walled cells that store food materials. They are arranged in vertical stacks that radiate from the centre of the wood outwards in lines known as medullary rays. These are responsible for the characteristic grain patterns of certain polished woods.
Softwoods have a quite different structure. They lack separate vessels and fibres, instead having tracheid cells that perform a combined conducting and supporting role. They also have parenchyma. Both sets of cells have channels to allow resin to flow.
Heart of the matter
The cells in the xylem have a limited life span. Over a period of years their walls become impregnated with a substance called lignin. Which makes them become gradually harder and rigid. Eventually, the cells become blocked with lignin, die and become a part of the tree’s heartwood. Since the cells retain the same shape after they have died as they had when still living, the structure of the heartwood is the same as that of the xylem.
There are considerable differences in colour and hardiness between the heart wood and the xylem due to the presence, in varying degrees. Of gums and resins produced in the cells. In the most prized timbers, such as ebony, the heartwood is almost black from the presence of hard resins and gums, which also make this wood extremely hardy.