Trees And Shrubs

USEFUL FUNCTIONS OF TREES

Today, we realize that, besides being a source of raw materials, trees are of even greater importance for their role in the regulation of climate, water management, hygiene, health, recreation; and, last but not least, in beautifying the environment. The past century has witnessed a rapid increase in world population, and the progress of science and technology has greatly changed man’s way of life. The result has been the emergence of vast industrial and suburban areas, with the majority of people living in cities, which have a specific climate and air polluted with dust, gases and other noxious substances. Industrial centres and cities are plagued by increasing noise that goes beyond bearable limits, the work pace is accelerating and man’s nervous system is being exposed to ever greater stresses and strains. The outlook for the future is one of further increase of population, further mechanization of life, higher consumption of water, increasing noise and greater loads on man’s nervous system. With such prospects in view, the role of trees, shrubs and other plants in cities will be of increasing importance, forests will have an increasingly significant role in water management, and people will seek respite from the stress of their daily lives in the country amidst the green of grass, shrubs and trees.

Investigations have shown that plants, and above all trees, reduce the dryness of the city climate. In streets, squares and parks they not only provide shade but also lower the ambient temperature as heat is taken up by the process of photosynthesis and transpiration. At night, conversely, they reduce the radiation of warmth into the atmosphere. Tree belts and expanses of turf enable better penetration of water into the soil, the water then being returned again by them to the atmosphere in the form of vapour during the process of transpiration and evaporation. That is why the ambient temperature is always lower and the relative humidity higher in parks and tree-lined streets.

Trees with a large leaf surface are similarly efficient filters of polluted city air. Their leaves, especially if they are tomemose and covered with fine hairs, entrap large quantities of dust particles, which are then washed off onto the ground by rain. The fact that trees and shrubs lower the speed of wind in city streets also promotes the settling of dust and the clearing of the air. Rows of trees and shrubs between traffic lanes or between street and pavement lower the noise of traffic by as much as 10 to 15 per cent.

The effect of tree belts or forest areas promoting the absorption of rainwater is very well known. In a forest, even after a heavy downpour, the water soaks rapidly into the ground and does not form puddles. The chief reason behind this is the soil structure: forest litter, high humus content and the small channels left in the soil by decayed roots. Tree belts also help to prevent erosion and the washing away of soil particles into brooks and rivers, thus not only holding in place the fertile topsoil so vital to good farming, but also keeping various man-made waterworks and reservoirs from being inundated with eroded material. Trees are also an effective means of strengthening the banks of water courses and keeping them from crumbling and washing away. A covering of trees and shrubs also prevents the formation and widening of gullies and ravines in danger spots on the earth’s surface.

High up in the mountains, trees and dwarf pine hold back build-ups of snow, thus preventing the formation of the avalanches, that are a common occurrence on treeless slopes when there is a thaw, leaving devastation in their wake and often taking their toll in human lives as well.

Trees in the landscape are pleasing to the eye and an important ornamental element, as one realizes only too well when travelling mile after mile through fiat countryside with only the horizon in sight. Trees brighten the landscape and give it its individual character. The broad valleys of large rivers are hard to envisage without groves of poplars amidst the spreading meadows, or without tree-shaded pools. In hill country we are accustomed to see oaks, limes and maples beside farmhouses and churches, and in mountain pastures the occasional mountain ash, juniper and spruce. Beside mountain cottages one may see spreading sycamores, ashes, elms and beeches. Avenues alongside roads and highways not only help these to blend well with the landscape but also provide welcome shade to both man and beast.

The isolated veterans scattered throughout the countryside, chiefly on hills or at crossroads, are an indication of the role they played in the lives of our ancestors and the instinct these men had for their appropriate location. Age-old trees, whose spreading branches offered welcome shade to farmers taking a rest from their toil in the fields one or two hundred years ago, today offer the same welcome respite to urban man seeking relaxation in the countryside. When we stand in awe before these giant and majestic trees, we realize that they are as much apart of a nation’s cultural heritage as are outstanding buildings, paintings and sculptures, and other artistic works; and that it is, therefore, our duty and responsibility to preserve them for posterity.

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