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

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

What are the features of tundra plant communities?

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

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

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

Annual plants with a short duration of summer 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 time to store nutrients, which will negatively affect the plant next year. The plant itself will not grow at full strength, as the vital processes slow down a little at lower temperatures.

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

The tundra is not one community, but a whole natural area. It combines different moss, meadow and shrub communities. Tundra plants live on cold, infertile, waterlogged soils. For growth and reproduction - two months of a short summer. During the winter months, they are threatened by freezing and desiccation in the cold. Therefore, tundra plants tend to be stunted.

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

Conclusion. 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 tundra plants?

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

Question 5. Why is the tundra very vulnerable?

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

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

Restoring a piece of forest in the tundra is very problematic. First, a cold, frosty wind will not allow them to grow and develop. Secondly, summer is short in the tundra, and trees, such as taiga, are not ready for this. Thirdly, multi-level thawing of the soil in the taiga will adversely affect the growth of trees. Fourthly, the water in the tundra stagnates, which leads to a lack of oxygen for the roots of the plant. There are other reasons as well. But you can try.

1. Grow plants. At the same time, they can be periodically subjected to the conditions in which they will grow.

2. Simultaneously with the first point, you need to select the most suitable tundra site. One year for him to watch. When the time comes to plant trees, prepare it a little.

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

4. Later we can watch the trees and see if they survive.

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

The temperature of the arable layer of the soil is measured with cranked thermometers Savinov TM-5. The set consists of four thermometers designed for installation at depths of 5, 10, 15 and 20 cm. Observations are made using crank thermometers only in the warm season on the same site where the soil surface temperature is measured.

At great depths, soil temperature 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. Installation of thermometers is stationary, designed for many years. At the installation site, natural vegetation and snow cover is preserved.

Experience (approximate list of items).

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

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

3. Every day, record the readings of thermometers throughout the year.

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

Flora - features of the tundra

The typical tundra is a treeless expanse with rather low and often incomplete vegetation cover. It is based on mosses and lichens, and small flowering plants grow against their background - grasses, shrubs, shrubs. In the real tundra there are no trees due to too harsh living conditions. During a cold and short summer, a protective layer of cover, which is necessary for a successful wintering, does not have time to fully form on young shoots of trees (without this layer, young branches die in winter from loss of water).

Why are there no trees in the tundra?

The reasons for the lack of trees in the tundra are as follows.

The conditions themselves for overwintering young trees are extremely unfavorable: hurricane winds, as well as snow corrosion, which systematically “cuts” young trees, so that they cannot rise above the snow.
Another circumstance plays an important role - the low temperature of the tundra soil during the summer, which does not allow the roots to make up for the substantial loss of water by the upper part of the trees during the so-called evaporation.
Only in the very south of the tundra, in more favorable climatic conditions, can individual trees be seen. They grow against the background of the existing tundra vegetation and are located quite far from each other, creating the so-called forest tundra.
What plants are found in the tundra
Lichens and mosses play an important role in the flora of the tundra. They consist of a large number of species and often create a solid carpet over large spaces. Both lichens and mosses perfectly tolerate the adverse conditions of the tundra.
A short list of plants growing in the tundra:
. Yagel (deer moss);
. Kukushkin flax;
. Highlander viviparous;
. Voronika (crowberry);
. Birch dwarf;
. Cloudberry;
. boletus;
. Blueberry;
. sedges;
. Willow Shaggy;
. Dryad (partridge grass);
. Poppy polar;
. Heather;
. Rosemary.

The word "tundra" is of Finnish origin and means a treeless area. It became interesting to me what exactly in local conditions determined the almost complete absence of continuous thickets of this kind of vegetation.

tundra flora

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

Frankly, maybe the words “willow”, “alder” and “birch” draw full-fledged trees in my head, but the listed species are more likely to pass for shrubs creeping along the ground. Yet this zone is the realm of mosses and lichens. The most common species can be called mosses (green, peat and deer (aka reindeer moss)), cladonia lichen.

Herbs in the tundra are perennial, frost-resistant. Representatives: buttercup, sedge, cotton grass, poppy, dandelion. The following shrubs are found: lingonberries, black crowberries, blueberries, princesses, blueberries, cloudberries.

Reasons for the lack of solid woody vegetation

To answer this question, it is enough to recall the climatic conditions of the area and the nature of the soil. The zone is notable for permafrost, which is maintained by low temperatures and is the cause of waterlogging of the territory. The fact is that 50 cm of soil thaws in summer, but the moisture that has formed does not go away, because the ground is still frozen below, and there is so little heat that evaporation is very scarce. All these points impede the flow 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 are not suitable for growing.

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