Vegetation

The present vegetation of Great Britain owes much of its character to the influence of man. Only in the more remote parts of Ireland and the Scottish Highlands do remnants of the natural vegetation still exist. The 'natural vegetation' in the true sense of the term has practically disappeared from Britain, and most of the present cover is loosely known as semi-natural in the unfenced rough grazing and in the woodland.

With its mild climate, a wide variety of relief and soils Britain once had a diverse pattern of vegetation. The original natural vegetation consisted of forest, fen and marsh in the wet lowlands, especially where the drainage was poor, and shrub, heath and moorland on the uplands where soils were thin. In the lowland areas the oak forest must have been the natural vegetation.

Over the centuries, however, the forests have had to make way for agriculture and settlement. But a systematic destruction of the forests took place in the 16th — 18th centuries with the construction of factories and roads, the development of mineral resources, the production of charcoal for iron-smelting, as well as to provide timber for shipbuilding and constructional purposes generally.

Apart from oak other trees of the wooded lowlands were ash, maple, elm and hazel. Today only a few scattered areas of extensive woodland remain, such as the New Forest in Hampshire and Sherwood Forest in Nottinghamshire, which owe their survival largely to the fact that in the Middle Ages they were set aside as 'Royal Forests' for hunting. The greatest density of woodland occurs in the north and the east of Scotland, in some parts of south-east England and on the Welsh border. Throughout most of England and parts of Wales and Scotland, where temperatures are high enough to permit trees to complete their annual cycle of growth between spring and autumn, deciduous varieties (such as oak, birch, beech and ash) are more numerous. In the north and on higher ground in the west these are replaced by coniferous species, pine, fir and spruce.

By the beginning of the twentieth century Britain's timber reserves had been so seriously depleted that in 1919 the Government set up a permanent Forestry Commission charged with the task of improving the position. It carries out a programme of planting in places which are not now forested, and of improving existing woodland, mainly on the acquired land in Scotland, Wales, the English Lake District and East Anglia. Today forest and woodland occupy only about 9 per cent of the surface of the country (out of the total 43 per cent in England, 43 in Scotland, 11 per cent in Wales and the remainder in Northern Ireland). Fifty-six per cent of forest and woodland belong to private landowners. Over 90 per cent of the timber used in the United Kingdom is imported.

Most of Britain is agricultural land of which about one-third is arable, and the rest pasture and meadow. Areas of permanent grassland are widespread in practically all parts of Britain except East Anglia, where arable farming is predominant, and in the highest parts of Scotland and Wales. These pastures form the chief grazing lands on which cattle and sheep are reared and fattened.

In certain areas of the country, particularly parts of the Highlands of Scotland, relief and climatic condititons are not conducive to arable farming, and such areas are therefore characterized by extensive moorland. Moorlands are found in the upland areas of north and west England, where soils are thin, drainage is poor and rainfall heavy. Large areas are commonly covered with peat and contain numerous bogs.

The hilly moorlands provide several types of wild vegetation, such as heather, fern, other hill grasses and these are to be found in the Highlands of Scotland, the Pennines, the Lake District, the mountains of Wales and elsewhere with a surface of thin poor soils.

The soils of the British Isles vary from the thin poor podzolic ones of highland regions to the rich fertile brown forest soils of low-lying areas like the fenlands of eastern England, southern England and the western Midlands.

Дата добавления: 2015-08-21