The importance of forests

1. The significance of forests is not restricted to timber use. They are an important geographical and ecological factor. They pro­tect the soil and water resources better than the most excellent artificial measures. Forests prevent soil erosion, retain surface waters, making them clean and still, and contribute to an increase in ground waters. In this respect, watershed forests are a kind of reservoir for useful moisture. Just the fact that forests regu­late the flow of rivers, prevent their pollution and their being clogged by silt, prevent floods or reduce them in size, makes them extremely valuable.

2. The forest is a powerful accumulator of the solar energy, it has a considerable influence on the formation of the climate, gas exchange in the atmosphere, and therefore it creates the living conditions for the people. Photosynthesis is the start of this circulation.

3. The forest, being the greatest biological composition in the world, assisting in air purification against dust and enriching it with oxygen, is an important regulator of the gas balance in nature. It is necessary to provide people with optimal oxygen rate in the amount of 400 kg per capita annually. For this purpose it is necessary to have 0.1-0.3 ha of forest per capita. It is known that one big tree while consuming carbon dioxide, is pro­ducing as much oxygen as one person needs a day for respira­tion. Under the conditions of the industrial city the energy of. photosynthesis is ten times decreased being affected by air pol­lution. It means that one person needs 10 trees instead of one.

4. The ability of the forest to clean the atmosphere from different mechanical substances, the majority of which is dust, involving insoluble and soluble components, is getting higher and higher importance nowadays. Forests are preserving their dust protec­tive ability even when they are leafless. Therefore forests and plantations of trees in cities are extremely necessary, and they are irreplaceable from the social and hygienic points of view.

5. The sanitary and hygienic importance of forest is manifested by their antimicrobe, sterilizing effect on the environment. The first and the most important property of forests is the ability to enrich the atmosphere with ionizing oxygen and phytoncidal sub­stances. Five-seven hour stay in the forest leads to the increase of the tone, improvement of the functions of the higher nervous activity, 10—30% increase of the minute respiration volume. Thus, the forest is a powerful air filter of antimicrobic, sterilizing properties, ionizing effect on the air and the total sanitary ef­fect on environment.

II Прочтите 3-ий абзац текста и письменно ответьте на следующий вопрос:

Why does one person need 10 trees instead of one in the industrial city?

Контрольная работа № 5

(для специальностей ММ, САТ)

Вариант 1

Дата добавления: 2015-10-16