Why are there no trees in the tundra or are they very small? Why is there no solid woody vegetation in the tundra? Three reasons for the absence of tree vegetation in the tundra

There are many interesting areas in the world. One of these zones is the tundra, a special climatic zone with low vegetation and a special bio-community.

117. What plant cannot grow in the tundra? Circle the drawing

In the picture, there is one extra tree (what does not grow in the tundra). This tree species is typical for taiga and pine forest, for other latitudes. But this conifer does not grow in the tundra for sure. The second picture should be circled, this is a spruce.

Explain your choice

The tundra is a zone where they grow low plants and very small trees. Dwarf birch can be considered the largest tree in this zone, and its height rarely reaches one and a half meters. The main reason why tall spruces cannot grow here is the lack of a fertile soil layer of the required volume. In permafrost conditions, where the soil is 50-70 centimeters, not a single tall tree will be held by its roots. The second reason, no less important, is soil freezing in winter. Extremely low temperatures can destroy the developed root system of tall trees.

Tundra and man

119. What human economic activity led to the emergence of cities in the tundra?

If we remember that the tundra is almost a desert, with sparse vegetation, then the question of forestry is immediately excluded. But under the permafrost there are huge treasures of our country: coal and ores of various metals, diamonds, gas, oil. It was this type of activity, as the development of the earth's interior, that became the reason for the emergence of cities in the tundra. It should be added that to this day, vast areas in the tundra have not been developed or inhabited by humans, and a railway connection to many tundra cities is still only planned.

120. How do the natural conditions of the tundra affect the occupations of the population? Give an example

The inhabitants of the tundra were mainly engaged in animal husbandry and hunting. Because of the scarce vegetation in the tundra, they have long tried to manage on the farm with animals that are adapted to these conditions. Taking as an example reindeer, then a small grass is enough for him in the warm season, and in winter he gets by with reindeer lichen, which he gets from under the snow. Cattle or small animals will not survive here, as there is nowhere to take hay to feed the sheep or goats in the winter. In addition, due to low temperatures, many pets will not survive here. There is a rare exception, this is the Yakut breed of horses, most likely from the Mongolian breed. These horses are able to tolerate being outdoors at minus 40-50.

In the warm season, part of the local population roams with herds of deer, others are engaged in fishing and hunting. Several types of berries grow in the tundra, which are harvested in summer. It is impossible to grow cultivated vegetable plants here because of the rapid end of the warm season and low temperatures.

121. Give examples of tundra animals listed in the Red Book of Russia

The musk ox is considered to be the rarest large animal of the tundra, which is listed in the Red Book of Russia. This animal is found in the North of Yakutia, in the Taimyr region, Wrangel Island, and today there are no more than two hundred of them left. Large and beautiful, this animal vaguely resembles a buffalo, but has thick and long hair.

Another animal from the Red Book is called the black-capped marmot. He does not wear a headdress, of course - this is often used in zoology to designate a black spot on the parietal part of the head of a mammal or bird. Black-capped marmots have suffered as a result of the development of their usual habitat by humans, and their economic activities.

122. a) An adult lichen plant reaches 15 cm in height (sometimes 20 cm). It grows only 5 mm per year. Together with a friend, calculate how many years it takes reindeer lichen to grow in full growth

If you do not take into account natural factors (droughts, fires), then for full growth reindeer moss will take the next number of years. Dividing 15 centimeters by 5 millimeters, we get the result 30. This is the number of years it will take for the lichen to reach its maximum growth. For a height of 20 cm, it will take 40 years, respectively.

b) Discuss which ecological problem may be due to excessive grazing of deer and why

Any human intervention, including grazing, is terrible for the vulnerable vegetation of the tundra. After all, the deer not only feeds on reindeer moss, it tramples young bushes and grasses, and damages lichens more than eats. Over time, this will lead to exposure of the soil in large areas, and the vegetation of the tundra will not have time to recover. But the vegetation in the tundra is important not only as an addition to the landscape, it is a food base for many insects, birds, and small animals. And when the lichen and grasses, shrubs and trees disappear, several species of birds and animals in the tundra will disappear along the chain.

The word "tundra" is of Finnish origin and means treeless territory. I wondered what it was in local conditions that determined the almost complete absence of continuous thickets of this kind of vegetation.

Flora of the tundra

Although trees do not unite into groups, forming forests, individual representatives still grow here:

Frankly speaking, maybe the words "willow", "alder" and "birch" draw full-fledged trees in the head, but the listed species are more likely to pass for shrubs creeping along the ground. Yet this zone is the kingdom of mosses and lichens. The most common species are mosses (green, peat and deer (aka lichen)), kladonia lichen.

The grasses in the tundra are perennial and frost-resistant. Representatives: buttercup, sedge, cotton grass, poppy, dandelion. The following shrubs are found: lingonberry, black crowberry, blueberry, princess, blueberry, cloudberry.

Reasons for the absence of solid woody vegetation

To answer this question, it is enough to remember climatic conditions terrain and nature of soils. The zone is notable for permafrost, which is supported by low temperatures and is the cause of waterlogging of the territory. The fact is that 50 cm of soil thaws in the summer, but the moisture that has formed does not disappear, since the ground is still frozen below, and there is so little heat that evaporation is very scarce. All these moments complicate the course of biological and chemical processes in the soil. This explains the small amount of humus and the accumulation of iron. As a result, tundra-gley soils are formed, which few people are suitable for growing.

Now, back to woody vegetation. The mentioned type of soil, due to poor aeration, is not conducive to tree growth. The root system is usually extensive, but how can it grow if the soil is like stone? Right, no way. In dwarf forms, the roots are small and spread along the upper layer.

Question 1. The topic of what discussion can be the dialogue between Antoshka and the biologist? Compare your version with the author's one (p. 141).

What are the features of tundra plant communities?

Question 2. How do plants protect themselves from the cold? (§ 25)

An annual plant dies off entirely, only seeds survive until next spring. Herbaceous perennials hibernate with tubers, rhizomes or bulbs. There are plants whose hibernating stems are covered with snow in winter, either because they are short, or because they are pressed to the ground by snow. In trees, the perennial stem survives the cold: the cambium is covered from frost by bark, and the buds are protected from drying out in the frost by kidney scales.

How can a short cold summer affect the life of a plant?

Annual plants, with a short summer duration, will not be able to complete their life cycle or such a summer makes it difficult for fruits and seeds to ripen. Biennials may not have enough time to store nutrients, which will negatively affect the plant next year. The plant itself will not grow at full strength, since life processes are slightly inhibited at lower temperature indicators.

Question 3. Formulate how the tundra communities differ from other communities you have studied.

Tundra is not one community, but a whole natural area... It combines various moss, meadow and shrub communities. Tundra plants live on cold, infertile, waterlogged soils. For growth and reproduction - two months of a short summer. AT winter months they are threatened by freezing and drying in the frost. Therefore, tundra plants are usually undersized.

The same mosses and lichens grow in the tundra communities as in the communities of the lower tiers of the northern forests. In the tundra, there are thickets of grasses and dicotyledonous grasses; in waterlogged areas, there are real swamps.

Output. The tundra is a treeless landscape in which plant development is limited by a lack of heat.

Question 4. How does the lack of heat affect the life of the tundra plants?

Tundra plants develop very slowly. They are small. Use any heat and light. Some begin to grow already under the snow, in caves thawed around them.

Question 5. Why is the tundra very vulnerable?

Because it's cold and windy there. And tundra plants develop very slowly, water stagnates in damaged areas of the soil, interfering with the dispersal of plants, empty areas do not overgrow for decades.

Question 6. Find a way to restore a piece of forest in the tundra. What problems will you face?

It is very problematic to restore a piece of forest in the tundra. First, the cold, frosty wind will prevent them from growing and developing. Secondly, the tundra has a short summer, and trees, such as taiga, are not ready for this. Thirdly, multilevel soil thawing in the taiga will have a detrimental effect on the growth of trees. Fourth, the water in the tundra stagnates, which leads to a lack of oxygen for the plant roots. There are other reasons as well. But you can try.

1. Grow plants. Moreover, you can periodically expose them to the conditions in which they will grow.

2. Simultaneously with the first point, you need to choose the most suitable area of \u200b\u200bthe tundra. You need to watch him for one year. When the time comes to plant trees, prepare it a little.

3. Place wind barriers around this area, which will save the trees from the wind until the latter adapt.

4. Subsequently, we can observe the trees and see that they survive.

Question 7. Plan an experiment to measure soil temperature in the tundra throughout the year. What can affect measurement accuracy?

The temperature of the topsoil is measured with Savinov TM-5 elbow thermometers. The set consists of four thermometers intended for installation at depths of 5, 10, 15 and 20 cm. Crank thermometers are used for observations only in the warm season at the same site where the soil surface temperature is measured.

At great depths, the temperature of the soil is measured by soil-deep (exhaust) mercury thermometers TPV-50. The complete set includes eight exhaust thermometers installed at depths of 20, 40, 60, 80, 120, 160, 240 and 320 cm. The installation of thermometers is stationary, designed for many years. Natural vegetation and snow cover is preserved at the installation site.

Experience (indicative list of items).

1. Prepare the site. The natural vegetation cover is preserved, and the site needs to be fenced off.

2. Install thermometers at different depths according to installation requirements.

3. Record thermometer readings every day throughout the year.

The accuracy of measurements can be affected by errors of thermometers, depending on their type.