- knolik

british planted woodlands

Значение термина british planted woodlands в knolik

british planted woodlands - British Planted Woodlands
british planted woodlands - Nearly all the British woods have at one time been planted or replanted by man, or have been so far modified by controlled fellings that their original natural character has been lost. Before detailing the prevailing types, a word may be said about the objects of management which have governed their planting and tending. The aims which the owners and foresters had in view may have altered from time to time, but a forest cannot be uprooted and replanted whenever it is thought desirable to manage it in another way. The farmer may plough up a field one year and put it down to grass the next, but an oakwood remains an oakwood from the day it is planted till the day it is felled 150 years later. Changes in woodland can only be worked slowly, and many of our woods reflect the needs and aims of a past age, being ill-adapted to present- day requirements. One would expect that the most valuable and useful types of forest, and species of tree, would be the most widely grown, but forest are a law unto themselves in such matters. Unless a constructive policy is continuously pursued, the most valuable woods, species and individual trees, tend to disappear in felling and thinnings, since it pays the timber merchant best to buy and convert these, and the owner, unless he is far-sighted, and of a conservative turn of mind, will prefer present cash-in-hand to the hope of future profit. Thus, if die trade in ash is good, the woodlands soon become denuded of that species, whilst less valuable species remain. A wise owner would replant with ash, but it may be that he has only sold the trees because he was in need of funds and has none to spare for re-planting; or he may find that other species can be planted more cheaply. Our woodlands, then, reflect the changing ideas of several past generations, besides the aims of the present-day foresters to establish new woods for various purposes.

objects of management. Most, but not all, woodlands are managed with a view to securing an economic return on the capital invested, representing a steady annual percentage, plus a small bonus to be regarded as profit after all the expenses of planting, tending, and management have been met. Similarly, most woods are managed with a view to meeting local demands for their produce, in particular fencing material for estate use, timber for' estate repairs, or the needs of a local industry such as a colliery needing pitprops or a turnery taking small poles in the round. Sporting plays a great part in British forestry, and where the rents paid for shooting are high, it may appear more immediately profitable to retain an unsaleable thicket crop, such as hazel coppice, rather than replant it with a useful and more profitable species. Occasionally, an owner with a keen interest in scientific forestry may establish sample plots with no other end in view but to ascertain the performance of new species in the British climate.

Over-riding all other objects, is the aim of most British tree- planters to enhance the scenic attractions of the area in their charge. This may be openly admitted under the name of "amenity planting or it may be concealed in such phrases as " a fine stand of timber indicating trees not only readily saleable but also attractive to the eye, by virtue of their clean straight stems. No matter what other purpose the trees may serve, owners and onlookers alike demand that woodlands shall be pleasing to the eye, a feature which most thriving woodlands ultimately assume, although in their early stages the conifers may appear monotonous to some. It is usually the duty of the forester to strike the right balance between varied objects of management, for most woods are run with more than one end in view.

Forest systems. Woodlands are classified by the ages of the trees within them and, according as to whether the crop is grown from seed or from the stumps of old trees, in the form of coppice shoots. Four systems are commonly met with in Britain.

coppice woods. Here the crop is grown from the stumps of trees planted an indefinite number of years ago. It consists of small poles which are cut at varying intervals, usually about 10 years. In such a wood, covering 100 acres, 10 acres only should be cut each year, to secure a steady return year after year for an indefinite period. Examples of coppice woods are willow on 1- to 3-year rotations for basket making; hazel, 7 to 10 years for hurdle making; chestnut, about 14 years for cleft pole fencing; ash, 7 to 10 years for tool handles; alder, about 15 years for turnery or clog-sole wood. Oak coppice, formerly important for fuel and tanning bark, is no longer an economic crop. Fig. 1.

Coppice-with-Standards. Amongst an underwood of coppice, a number of selected trees are allowed to grow up and form a second storey of timber. In theory, these standard trees are felled after so many coppice rotations; in practice, they are more often felled whenever timber or cash is required, and the poorer specimens are either not bought by the timber merchant or, if bought, not felled by him. Under this system, it is impossible to grow long clean sticks of timber; the standards must be widely spaced to allow the coppice to grow, and consequently cannot draw one another up. This system was the prevailing one over southern England for hundreds of years, and still covers big areas. The underwood is nearly always hazel, and the standards (which must be light-demanding trees) oak or ash. This system met local demands for hazel fence-material, besides the needs of the country carpenter. It is no longer economic, as the present demand for hazel is small and is not compensated by the poor return from the short-boled standard timber. Fig. 2.

Selection woodlands. In these, all the trees are grown from seedlings, usually self-sown or " self-comers ". Trees of all ages are found growing together in harmony, the right balance between the age groups being maintained by skilful felling and thinning. Selection woods are usually formed by modifying natural Woodlands, more rarely by effecting changes in the composition of maturing plantations. Once established they are seldom clear- felled, but persist indefinitely. They are much rarer in Britain than they are abroad, the best known example being the beech woods of the Chilterns. Selection woods may be pure or mixed, and usually contain a high proportion of shade-bearers. Fig. 2.

Even-aged high forest is the usual system adopted in modern British forestry. In this, all the trees on a given area are of the same age, or nearly so, and all grow from seed. On the continent of Europe, it is usual for such even-aged areas to arise from the natural seeding of the previous crop, known as Natural Regeneration. In Britain, they are more usually established by planting out young trees raised from seed in the nurseries. Even-aged woods may be pure or mixed; if one species of a mixture is only planted to aid up the other, as larch with ash, it is termed a " nurse ". It is usual to plant a large number of trees a few feet apart, perhaps 2,000 to the acre, and to reduce the numbers by frequent thinnings until only a fraction, perhaps 200 to the acre, remains. By that time the stand is mature, ripe for felling and replanting. To secure continuous yields, an equal area should be felled and replanted each year. Thus, in a 1,000-acre wood growing trees on a 100-year rotation, 10 acres should be felled and replanted each year. There will then be 10 acres of trees of every age from 1 to 100, forming the so-called " normal " forest, but such regularity is very rare in practice. Even-aged high forest, if of a light-demanding species, is sometimes under-planted with a shade-bearer to preserve soil fertility, e.g. beech beneath oak; sometimes the under-plant is allowed to grow on to timber size, after the upper storey is felled.

A wide range of species is grown as even-aged high forest. Scots pine, larch, and other conifers predominate in Scotland; oak, beech, and ash in England and Wales. All the important recent 20

importations from abroad are adapted to the system, either as main crop or as under-plants, such as Tsuga and Abies grandis. Rotations vary from 20 years for conifer pitprops to 200 years for the biggest oak. Figs. 4, 5, 6, 7, 8, 9.

Amenity woodlands. These are planted to improve the surroundings of country houses and farms, and take the form of belts, screens, clumps, park trees and groves, roadside fringes and avenues. They are usually planted at one time, often with a hard edge of conifers to shelter a softer core of broad-leaved trees from the wind. Selected fellings and replantings at Various times gradually render them uneven-aged; breaking up their regularity and improving their appearance. The broad-leaved trees take longer to mature and usually outlast the conifers. Figs. 10, 11.

Arboreta. These are collections of the rarer trees planted partly for amenity, partly for scientific interest. Collections of broad-leaved trees, either native or foreign, are rare in Britain; but on the other hand, the conifer collections are the finest in the world. Such arboreta are not only of the greatest interest to the botanist, but they also provide invaluable information to the forester. Many of the imported conifers are being planted in great numbers on the strength of their growth in garden and parkland collections. Excellent collections of the rarer trees, particularly conifers, may also be seen in commercial nurseries. Fig. 12.

Town and garden planting is especially important in a country with a highly urban population, with great cities sprawling into extensive suburbs which isolate many town-dwellers from the open countryside. The semblance of the country is demanded in the towns, and can only be obtained by the widespread planting of trees, in gardens, parks, and along the roadways. Their tending is the concern of the gardener and park-keeper, but their growth and well-being is perhaps as important to the welfare of mankind as that of the timber trees which most concern the forester. They do not feed the mill or the fire, but some say that they feed the soul.

Fig. 13 shows planes, willows, limes, and poplars, with lesser flowering trees of the rose tribe, thriving together in the heart of London.

Рядом со словом british planted woodlands в knolik

park conifers

В начало
буква ""
буквосочетание ""

study of trees

Статья про british planted woodlands была прочитана 93 раз

Our friends, knolik encyclopaedia knolik.com