Read this text. Can you say that you know all the things given below? What was new for you?

Something about Grasslands

Grasslands are characterized as lands dominated by grasses rather than large shrubs or trees. There are two main divisions of grasslands: (1) tropical grasslands, called savannas and (2) temperate grasslands.

Savanna

Savanna is grassland with scattered individual trees. Savannas of one sort or another cover almost half the surface of Africa and large areas of Australia, South America, and India. Climate is the most important factor in creating a savanna. Savannas are always found in warm or hot climates where the annual rainfall is from about 50.8 to 127 cm per year. It is crucial that the rainfall is concentrated in six or eight months of the year, followed by a long period of drought when fires can occur. If the rain were well distributed throughout the year, many such areas would become tropical forests. Savannas which result from climatic conditions are called climatic savannas. Savannas that are caused by soil conditions and that are not entirely maintained by fire are called edaphic savannas. These can occur on hills or ridges where the soil is shallow, or in valleys where clay soils become waterlogged in wet weather. A third type of savanna, known as derived savanna, is the result of people clearing forest land for cultivation. Farmers fall a tract of forest, burn the dead trees and plant crops in the ashes for as long as the soil remains fertile. Then, the field is abandoned and, although forest trees may recolonize, grass takes over on the bare ground (succession), becoming luxuriant enough to burn within a year or so. In Africa, a heavy concentration of elephants in protected parkland have created a savanna by eating leaves and twigs and breaking off the branches, smashing the trunks and stripping the bark of trees. Elephants can convert dense woodland into open grassland in a short period of time. Annual fires then maintain the area as a savanna.

The soil of the savanna is porous, with rapid drainage of water. The predominant vegetation consists of grasses and forbs (small broad-leaved plants that grow with grasses). Because the savanna supports such a large number of species competing for living space, usually only one or a few kinds of grass are more successful than the others in a particular area. Deciduous trees and shrubs are scattered across the open landscape. One type of savanna common in southwestern Kenya, Tanzania, and Uganda, known as grouped-tree grassland, has trees growing only on termite mounds —the intervening soil being too thin or poorly drained to support the growth of trees at all. Frequent fires and large grazing mammals kill seedlings, thus keeping the density of trees and shrubs low.

Savanna has both a dry and a rainy season. Seasonal fires play a vital role in the savanna’s biodiversity. In October, a series of violent thunderstorms, followed by a strong drying wind, signals the beginning of the dry season. Fire is prevalent around January, at the height of the dry season. Fires in savannas are often caused by poachers who want to clear away dead grass to make it easier to see their prey. The fires do not devastate the community. Most of the animals killed by the fires are insects with short life spans. A fire is a feast for some animals, such as birds that come to sites of fires to eat grasshoppers, stick insects, beetles, mice, and lizards that are killed or driven out by the fire. Underground holes and crevices provide a safe refuge for small creatures. Larger animals are usually able to run fast enough to escape the fire. Although the dry stems and leaves of grasses are consumed by fire, the grasses’ deep roots remain unharmed. These roots are ready to send up new growth when the soil becomes moister. The scattered shrubs can also subsist on food reserves in their roots while they await the time to shoot out new twigs. Unlike grasses and shrubs, trees survive a fire by keeping some moisture in all their above-ground parts throughout the dry season. Sometimes they have a corky bark or semisucculent trunk covered with smooth resinous bark, both being fire resistant. During March, violent thunderstorms occur again, this time opening the rainy season. When the rains come, savanna bunch grasses grow vigorously. Some of the larger grasses grow an inch or more in 24 hours. The savanna experiences a surge of new life at this time. For example, many antelope calves are born. With so much grass to feed on, mothers have plenty of milk. Calves die if the rains fail to come.

Other animals (which do not all occur in the same savanna) include giraffes, zebras, buffaloes, kangaroos, mice, moles, gophers, ground squirrels, snakes, worms, termites, beetles, lions, leopards, hyenas, and elephants.

There are also some environmental concerns regarding savannas such as poaching, overgrazing, and clearing of the land for crops.

Temperate Grassland

Temperate grasslands are characterized as having grasses as the dominant vegetation. Trees and large shrubs are absent. Temperatures vary more from summer to winter, and the amount of rainfall is less in temperate grasslands than in savannas. The major manifestations are the veldts of South Africa, the puszta of Hungary, the pampas of Argentina and Uruguay, the steppes of the former Soviet Union, and the plains and prairies of central North America. Temperate grasslands have hot summers and cold winters. Rainfall is moderate. The amount of annual rainfall influences the height of grassland vegetation, with taller grasses in wetter regions. As in savannas, seasonal drought and occasional fires are very important to biodiversity. However, their effects aren’t as dramatic in temperate grasslands as they are in savannas. The soil of the temperate grasslands is deep and dark, with fertile upper layers. It is nutrient-rich from the growth and decay of deep, many-branched grass roots. The rotted roots hold the soil together and provide a food source for living plants. The seasonal drought, occasional fires, and grazing by large mammals all prevent woody shrubs and trees from invading and becoming established. However, a few trees, such as oaks, and willows grow in river valleys, and some nonwoody plants, specifically a few hundred species of flowers, grow among the grasses.

Precipitation in the temperate grasslands usually occurs in the late spring and early summer. The annual average is about 50.8 to 88.9 cm (20-35 inches). The temperature range is very large over the course of the year. Summer temperatures can be well over 38° C (100 degrees Fahrenheit), while winter temperatures can be as low as -40° C (-40 degrees Fahrenheit).

The fauna (which do not all occur in the same temperate grassland) include gazelles, zebras, rhinoceroses, wild horses, lions, wolves, prairie dogs, jack rabbits, deer, mice, coyotes, foxes, skunks, badgers, blackbirds, grouses, meadowlarks, quails, sparrows, hawks, owls, snakes, grasshoppers, leafhoppers, and spiders.

There are also environmental concerns regarding the temperate grasslands. Few natural prairie regions remain because most have been turned into farms or grazing land. This is because they are flat, treeless, covered with grass, and have rich soil.

Temperate grasslands can be further subdivided. Prairies are grasslands with tall grasses while steppes are grasslands with short grasses. Prairie and steppes are somewhat similar but the information given above pertains specifically to prairies—the following is a specific description of steppes.

Steppes are dry areas of grassland with hot summers and cold winters. They receive 25.4-50.8 cm of rainfall a year. Steppes occur in the interiors of North America and Europe. Plants growing in steppes are usually greater than 1 foot tall. They include blue grama and buffalo grass, sagebrush, spear grass, and small relatives of the sunflower. Steppe fauna includes badgers, hawks, owls, and snakes. Today, people use steppes to graze livestock and to grow wheat and other crops. Overgrazing, plowing, and excess salts left behind by irrigation waters have harmed some steppes. Strong winds blow loose soil from the ground after plowing, especially during droughts. This causes the dust storms of the Great Plains of the U.S.

 

A) Find in the text the following words and word combinations.

Разбрасывать; годовой уровень осадков; быть равномерно распределенным; саженцы; глинистая почва; разрушать; трещина; убежище; пробковая кора; огнеупорный; преобладающая растительность; разветвленные корни травы; разница температур; внутренние районы.

B) Translate into Russian the following English words and word combinations.

Crucial; termite mounds; poorly drained; poachers: prey; short life spans; to shoot out new twigs;semisucculent trunk; smooth resinous bark; overgrazing; nutrient-rich soil; decay; seasonal drought; occasional fires; grazing land; to graze livestock; loose soil.

C) In what connection are these words and word combinations used?

Tundra occupies a rather large part of our country. And as there are huge deposits of gas, oil, nickel and other natural resources we must know as much as possible about it. Read this text and retell it.

Something about Tundra

Tundra is the coldest of all the biomes. Tundra comes from the Finnish word tunturia, meaning treeless plain. It is noted for its frost-molded landscapes, extremely low temperatures, little precipitation, poor nutrients, and short growing seasons. Dead organic material functions as a nutrient pool. The two major nutrients are nitrogen and phosphorus. Nitrogen is created by biological fixation, and phosphorus is created by precipitation. Tundra is separated into two types: arctic tundra and alpine tundra.

Characteristics of Tundra

1. Extremely cold climate

2. Low biotic diversity

3. Simple vegetation structure

4. Limitation of drainage

5. Short season of growth and reproduction

6. Energy and nutrients in the form of dead organic material

7. Large population oscillations

Arctic
   Arctic tundra is located in the northern hemisphere, encircling the North Pole and extending south to the coniferous forests of the taiga. The arctic is known for its cold, desert-like conditions. The growing season ranges from 50 to 60 days. The average winter temperature is -34° C (-30° F), but the average summer temperature is 3-12° C which enables to sustain life. Rainfall may vary in different regions of the arctic. Yearly precipitation, including melting snow, is 15 to 25 cm. Soil is formed slowly. A layer of permanently frozen subsoil called permafrost exists, consisting mostly of gravel and finer material. When water saturates the upper surface, bogs and ponds may form, providing moisture for plants. There are no deep root systems in the vegetation of the arctic tundra; however, there are still a wide variety of plants that are able to resist the cold climate. There are about 1,700 kinds of plants in the arctic and subarctic, and these include:

· low shrubs, sedges, reindeer mosses, liverworts, and grasses;

· 400 varieties of flowers;

· crustose and foliose lichen.

All of the plants are adapted to sweeping winds and disturbances of the soil. Plants are short and group together to resist the cold temperatures and are protected by the snow during the winter. They can carry out photosynthesis at low temperatures and low light intensities. The growing seasons are short and most plants reproduce by budding and division rather than sexually by flowering. The fauna in the arctic is also diverse:

· Herbivorous mammals: lemmings, voles, caribou, arctic hares and squirrels;

· Carnivorous mammals: arctic foxes, wolves, and polar bears;

· Migratory birds: ravens, snow buntings, falcons, loons, ravens, sandpipers, terns, snow birds, and various species of gulls;

· Insects: mosquitoes, flies, moths, grasshoppers, blackflies and arctic bumble bees;

· Fish: cod, flatfish, salmon, and trout.

Animals are adapted to handle long, cold winters and to breed and raise young quickly in the summer. Animals such as mammals and birds also have additional insulation from fat. Many animals hibernate during the winter because food is not abundant. Another alternative is to migrate south in the winter, like birds do. Reptiles and amphibians are few or absent because of the extremely cold temperatures. Because of constant immigration and emigration, the population continually oscillates.

Alpine
  Alpine tundra is located on mountains throughout the world at high altitude where trees cannot grow. The growing season is approximately 180 days. The nighttime temperature is usually below freezing. Unlike the arctic tundra, the soil in the alpine is well drained. The plants are very similar to those of the arctic ones and include:

· tussock grasses, dwarf trees, small-leafed shrubs, and heaths

Animals living in the alpine tundra are also well adapted:

· Mammals: pikas, marmots, mountain goats, sheep, elk;

· Birds: grouselike birds;

· Insects: springtails, beetles, grasshoppers, butterflies.

Text II.