Why do trees shed their leaves in autumn? Causes of autumn leaf fall. What to do if the trees did not shed their leaves for the winter
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Many types of trees shed their leaves as a strategy to survive harsh weather. weather. In the temperate forests of the Northern Hemisphere, trees shed their leaves in autumn as the cold weather approaches. In tropical and subtropical forests, trees shed their leaves with the onset of the dry season. Trees that lose all their leaves during the year are called deciduous trees. Common deciduous trees in the Northern Hemisphere include several species of ash, aspen, beech, birch, cherry, elm, hickory, hornbeam, maple, oak, poplar, and willow. In tropical and subtropical regions, deciduous trees include several species of acacia, baobab, roble, ceiba, chasa, and guanacaste. Majority deciduous trees have broad leaves that are susceptible to damage in cold or dry weather. In contrast, most evergreen trees either live in warm, humid climates or have weather-resistant needles as leaves. However, there are exceptions in nature, such as American larches, which shed their needles each and Live Oak, which retain their broad leaves throughout the year, even in relatively cool climates. The loss of leaves helps trees conserve water and energy. When inclement weather approaches, hormones in the trees trigger a process of amputation where leaves are actively sheared away from the tree by specialized cells. At the start of the shedding process, trees absorb valuable nutrients from their leaves and store them for later use in their roots. Chlorophyll, the pigment that gives leaves their green color, is one of the first molecules to be broken down into nutrients. This is one of the reasons why they turn red, orange and gold during leaf fall.
Table of contents
Introduction …………………………………………………………………….2
My Observations…………………………………………………………3
Questioning classmates ………………………………………..3
3. The role of leaves in the life of a tree………………….................................................... .....4
4. Why do leaves change color? ................................................. ..................4
5. Folk signs…………………………………………………………..5
6. How does leaf fall occur? .............................................. ...............................6
7. Why do trees shed their leaves? .............................................. ...............7
8. The value of fallen leaves in nature…………………………………..8
Conclusion ………………………………………………………………….10
List of information sources used.………………………11
Appendix……………………………………………………………………12
Introduction
In a golden carriage with a playful horse,
Autumn galloped through the forests and fields.
The good sorceress changed everything,
Brightly - yellow painted the earth.
Autumn is a wonderful time of the year. Leaf color change is one of the first signs of autumn. Lot bright colors in the autumn forest! Birches, maples turn yellow, patterned rowan leaves turn crimson-red, aspen leaves turn orange and crimson. At this time of the year, I like to wander through the autumn park, breathe fresh air, observe nature, collect bouquets from fallen leaves, admiring yellow, crimson, purple colors.
Once, I was collecting foliage for crafts, and I became interested. Why do leaves change color in autumn? Why couldn't even a strong wind blow them off in the summer, and why do they come off on their own in the fall? What happened?
And here comes the speculation:
1. The leaves on the trees are old, they are cold, so they fall off.
2. The leaves are getting dark.
3. Leaves fall from the wind.
To test my assumptions, I set myself following goals and tasks:
Objective: Find out - why are the leaves falling?
Tasks:
1. Find out the meaning of the leaf in the life of the plant.
2. Watch the leaves change in autumn.
3. Establish the causes of leaf fall.
4. Make a herbarium from autumn leaves.
To solve these problems, I had to read the literature on this issue, contact a biology teacher on this issue, and study Internet sources.
1. My observations
I watched the leaves change in autumn.
In September, yellow leaves appeared on some trees, but the connection with the branches was still strong. (see annex 1)
In October, almost all the leaves changed their green color to yellow, brown, red, and leaf fall began. (see annex 2)
In November, almost all deciduous trees shed their leaves.
The last to get rid of the leaves - willow. (see annex 3)
2. Questioning of classmates and students of the school.
At the beginning of the study, I decided to conduct a survey
their classmates and students of our school to find out if they know why a tree needs leaves, why leaves change color and fall in autumn. (see appendix 4,5,6)
The results were as follows: to the question why the tree needs leaves, among classmates only 2% of students answered correctly, among grades 1-4 the correct answer was 12%, students in grades 5-9 answered 25% in the affirmative, and 10-11 grades - 32%.
When asked why the leaves change their color, classmates were able to correctly answer -5%, grades 1 - 4 -14%, grades 5 - 9 - 28%, grades 10 - 11 - 41%.
Why the leaves fall in autumn, classmates answered correctly - 4%, grades 1 - 4 - 18%, grades 5 - 9 - 22%, grades 10 - 11 - 37%.
Analyzing the results of the survey, I found that most students do not know the reasons for the change in the color of autumn leaves and the reasons for their fall.
The role of leaves in the life of a tree
I studied the structure of the leaf and found out that the leaf consists of two parts: the leaf blade is what we used to call the leaf, and the petiole is its stalk. (see annex 7)
With the help of the petiole, the leaf is attached to the branch.
On the leaf blade, the veins are very clearly visible, especially from the underside. They pass into the petiole. It turns out the veins are the vessels through which water and nutrients move. But if we look into the middle of a green leaf, we will see that each leaf is full of wonderful green chlorophyll grains. (see appendix 8) The grains are so small that they cannot be seen. And yet each such grain is, as it were, a tiny factory. They cook food for the whole tree. These factories take from the air invisible carbon dioxide. From this gas, water and substances dissolved in it, extracted by the roots, wonderful grains are made construction material for new branches, buds, roots and, of course, for the trunk itself. Just as a new house cannot rise without concrete and brick, so a tree cannot grow without the material prepared by the green seed-plants. Green plants get their energy from the sun. Tiny chlorophyll grains catch the light from morning to evening. They are colored green by chlorophyll, which is constantly destroyed and rebuilt again thanks to sunlight.
Conclusion: the green leaf is necessary for the tree, as it prepares food and new building material for the whole plant. The yellow leaf interferes with the tree. It consumes a lot of moisture, but the tree does not nourish.
Why do leaves change color?
After studying the literature, I found out why the leaves change color in autumn. In summer, the sun shines for a long time, the formation of chlorophyll does not lag behind its destruction. The leaf stays green all the time. Autumn is coming, the nights are getting longer. Plants receive less light. Chlorophyll is destroyed during the day, but does not have time to recover. The green color in the leaf decreases, and the yellow becomes more noticeable: the leaf turns yellow.
But in autumn, the leaves become not only yellow, but also red, crimson, purple. It depends on what coloring matter is in the withering leaf.
The autumn forest is rich in its colors! The brightness of autumn leaves depends on what the weather is like (see Appendix 9.10).
If the autumn is long, rainy - the color of the foliage from excess water and lack of light will be dull, inexpressive. If cold nights alternate with clear sunny days, then the colors will match
weather - juicy, bright.
Alder and lilac leaves will fall green, regardless of the weather. In their leaves, except for chlorophyll, there are no other coloring substances. (see annex 11)
Folk omens
People have been observing nature for a long time, noticing everything that happens around. And among the people there were signs associated with a change in the color of the leaves.
The leaf, although it has turned yellow, falls off weakly - frosts will not come soon.
If in autumn the birch leaves begin to turn yellow from the top, then the next spring will be early, and if from below, then late.
Untimely, yellow leaves will appear on the trees - by early autumn.
Until the leaf from the cherry trees has fallen, no matter how much snow falls, winter will not come.
bony leaves Before bad weather, they bend up, and before good weather, they twist down.
If birch lowers its leaves forward, then wait for a dry summer, and if alder and maple, then wet.
If in the spring the birch leaves the leaves before the alder, the summer will be windy, and if the alder blossoms earlier, then colds and rains will be frequent in the summer.
If in autumn the leaves of a birch begin to turn yellow from the top, then the next spring will be early, and if from below, then late.
If the oak buds and leaves earlier than the ash, then the summer will be wet and cool. If the ash tree blooms earlier, then the summer should be dry and warm.
How does the leaf fall come?
No one tells a tree when to shed its leaves. But now autumn is approaching - and the leaves on the trees change their green color. Nutrients begin to be pulled from the leaves into the trunk.
Changes also occur in the petioles of the leaves. The petiole consists of "bricks" (cells) and thin tubes (vessels), through which nutritious juices come from the tree. Leaves need them for growth and development. In summer, the “bricks” are firmly interconnected and just as firmly attach the leaf to the branch.
Try picking a green leaf, for example, from a birch. It is easier to break than to separate without any damage.
And in autumn? The more yellowed or reddened the leaf, the easier it breaks off. And there comes a moment when you just have to touch the leaf, as it immediately falls from the branch.
In autumn, the connections between the bricks in the petiole are destroyed because the chlorophyll grains that produced the building material for the entire tree have collapsed. A special cork layer is formed. It is like a partition between the petiole and the branch. The leaf is held only on thin tubes. (see annex 12)
To prove this scientific fact, I conducted an experiment.
I took two branches: broken by the wind in the summer, and in the fall. I tried to tear off the sheet from the first one. The leaves on it had long dried up, crumbled easily, but came off badly. I tried to tear off a leaf from a branch that was not damaged in the summer. The sheet came off very easily.
Examined with a magnifying glass autumn twigs different trees I did not find wounds from fallen leaves on them.
Conclusion: the leaves do not break off the branches, but separate in a certain place - where the petiole is attached to the branch, and where a cork layer forms in autumn. (see appendix 13)
7. Why do trees shed their leaves?
Although our deciduous trees live for tens, often hundreds of years, their leaves "work", only one season.
All in a green leaf bottom surface, covered with a transparent skin, dotted with small holes - stomata. Under the influence of ambient temperature and air humidity, they either open or close. Like windows in houses. The water that the root sucks up rises along the trunk to the branches and leaves. When the stomata are open, moisture evaporates from the leaves, and new portions of water are pulled up through the trunk into the crown.
The sun heats the leaf, and the evaporation cools it. Trees need a lot of water. During the summer, a large birch, for example, evaporates about 7 tons of water. In winter, you can’t get so much moisture from the soil. Winter for trees is not only cold, but also, most importantly, dry season. By losing their leaves, the trees protect themselves from the "winter drought". Trees do not have leaves - there is no such abundant evaporation of water. (see annex 14)
In addition, trees need leaf fall for medicinal purposes.
It turns out that the plant receives from the soil not clean water, and solutions of various salts. These salts, passing along with water through the whole plant, also enter the leaves. Part of them goes to feed the plant, while the part that remains unused is deposited in the cells of the leaf. As a result, by autumn, the leaves become, as it were, mineralized, abundantly saturated with salts, the deposits of which in some cases can even be seen under a microscope. A large amount of mineral salts deposited by autumn in the leaves disrupts their normal operation and becomes harmful to the plant. (see annex 15)
In cities, the air is heavily polluted by smoking chimneys of factories and plants. The smallest particles of soot settle on the leaves, clog the stomata. Evaporation slows down. The sheet is weighted inside - with mineral salts, and outside - with urban soot, and a light gust of wind easily breaks it off.
(see annex 16)
I did an experiment. Plucked from a tree autumn leaf and rubbed sheet plate with a clean, damp swab. The tampon is dirty.
Conclusion: leaves trap dust, urban soot and various substances from the air, which means that the stomata of the leaf become clogged, evaporation slows down. An excess of mineral salts accumulates inside the leaf. The leaf becomes heavier, a slight gust of wind rips it off.Dropping their leaves, trees protect themselves from "winter drought", mechanical damage under the pressure of snow and poisoning. harmful substances accumulated in the sheet.
8. Significance of fallen leaves in nature
Fallen leaves are indeed of great importance in nature.
1. We noticed that the leaves dry out under the action of the sun, begin to crumble, turning into dust. Under the influence of rain, snow, and also due to the work of certain microorganisms, they rot, gradually mixing with the ground, forming humus. It turns out that fallen leaves are a valuable organic and mineral fertilizer for the same trees from which they flew! (see annex 17)
2. Leaf litter has been found to be a very poor conductor of heat. And together with a thick layer of snow throughout the winter, it insulates the roots of trees, protecting them from frost, and preserves plant seeds. Serves as a blanket for the tree. If you dig up the snow, you can see small sprouts through the packed foliage. And in each sprout, future leaves merged with the stem and even flower buds are distinguished. (See Appendix 18)
3. In spring, water accumulates in a thick leafy blanket, like in a sponge, which gradually flows to the roots of trees and shrubs, nourishing them, supplying moisture and mineral salts valuable for their growth. Nutrients from rotted leaves are reabsorbed by the roots. It is noticed that the land devoid of forest litter is drier. Soil dries out quickly after rain open areas. And under the leaves remains wet for a long time.
4. In summer, leaf litter saves the soil from dangerous compaction. After all, the soil should be loose, rich in air and moisture. Only then will plants grow on it. If you destroy the leaves - the soil is quickly compacted, depleted.
5. It should be mentioned that during the overdrying, the foliage releases physiologically active substances that contribute to the recovery of patients. Trees and shrubs deprived of their forest floor become weaker, more vulnerable to pests and disease.
6. Living beings hide in fallen leaves:
Ants
ground beetles
They exterminate various pests of plants and participate in the processes of soil formation. (see annex 19)
7. Can't do without fallen leaves and hedgehogs. In winter, hedgehogs hibernate. In autumn, they build a hut for future wintering, which they often build between the horses of trees protruding from the ground, in hollow stumps, sometimes in burrows or in small natural depressions in the ground, or simply on level ground - among the mass of brought shoots and leaves of plants. Warming the future winter apartment, hedgehogs drag more fallen leaves, plant stems, dry grass and loose moss there in the fall. (see annex 20)
8. Mushrooms cannot do without the forest floor. It is a vital basis for them. After all, the mycelium, being under the rays of the sun, can dry out and die. Leaves and moss protect it from drying out. When picking mushrooms, you can not scatter the leaves under which they hide. You just need to carefully twist the mushroom or cut it with a knife. (See Appendix 21)
9. Fallen leaves are needed by many forest animals. Under it, for example, acorns and shoots of plants that feed on wild boars are stored for a long time.
10. Indirectly, forest litter is also necessary for birds. They rake the leaves in order to find in them small insects and larvae, as well as preserved plant seeds.
11. For us, schoolchildren, leaf fall also brings a lot of joy. Leaves can be made beautiful picture, sticking them at will on cardboard, you can weave beautiful wreaths, make crafts. Similar work develops creative imagination awaken the fantasy. (see annex 22)
The fallen leaves crunch underfoot. And how fun it is to collect the leaves in a pile and then jump into it! This game brings joy, develops dexterity and speed.
There is another assertion that the smell of rotten leaves has a beneficial effect on nervous system relieves fatigue. I love autumn for its colors and special aroma!
Conclusion
Summing up research work, I can conclude that the goal that I set was achieved. I studied why trees fall so easily in the fall, and compared sound and scientifically proven findings with the results of research on the topic.
The hypotheses that I put forward at the beginning of the study were not confirmed. Leaves do not fall from trees because they are cold and old.
The real causes of leaf fall are as follows:
1. Lack of sunlight
Chlorophyll is destroyed, new building material is not produced in the leaf, connections between cells in the petiole are destroyed. A cork layer is formed. The leaf is held only on thin tubes.
lack of moisture
The leaves of the tree in their totality have very large area, and water is rapidly evaporating from all this area. In summer, the tree is able to compensate for the loss of moisture by extracting water from the soil. But with a cold snap cold water from the soil is greatly reduced. It gets in the way correct work leaf and tree life. If the tree had not dropped its leaves, it would have been in danger of drought.
3. Excess minerals
The leaf becomes heavier and barely holds on to the branch, the wind easily rips it off.
During leaf fall, the tree gets rid of excess mineral salts that could poison it.
Fallen leaves are of great benefit to the forest, animals, insects, and therefore to us - people. After all, we are part of nature, and this should never be forgotten. (see annex 23)
During the study, I collected, studied the leaves of trees. He made a herbarium and compositions from this natural material.
List of sources of information used.
1. Big encyclopedia of the student / trans. from French Bogatyrevoy E., Zemtsova T., Lebedeva N. - M .: LLC Publishing House Astel: LLC Publishing House AST, 2003, p. 711;
2. The Big Encyclopedia of the Erudite, - M: Makhaon, 2004, p. 487;
3. Children's encyclopedia "Forest World"; Moscow Makhaon, 2006
4. Why and why / encyclopedia for the curious, ed. Pokidayeva T., Frolova T., - M.: Makhaon, 2007, p. 255 ;
5. Why in autumn - leaf fall? / G. Graubin, - M: Malysh Publishing House, 1990
6. Your first encyclopedia "Forest Life"; Moscow "Makhaon", 2004
7. Why in the fall - leaf fall? / G. Graubin, - M: Malysh Publishing House, 1990
8.http://go.mail.ru/search
9.http://www.ezosite.ru/token/pogoda/pogoda_658.html
10.http://geoman.ru/books/item/f00/s00/z0000068/st015.shtml
11.http://nplit.ru/books/item/f00/s00/z0000053/st019.shtml
12.
If the trees did not shed their leaves for the winter, they would die. There are several reasons for this.
Reason one. The leaves of the tree in their totality have a very large area, and water evaporates intensively from all this area. In summer, the tree is able to compensate for the loss of moisture by extracting water from the soil. But with cooling, the extraction of cold water from the soil is greatly reduced; in winter, it is completely difficult to extract moisture from frozen soil. Trees with deciduous cover in winter would die from lack of moisture, that is, they would dry out.
For the same reason, with the onset of the dry season in the tropics and subtropics, the trees in these climatic zones shed their leaves and stand bare until the rainy season arrives.
The second reason. Have you noticed that after heavy snowfalls, the branches of trees strongly lean towards the ground under the weight of snow? Some branches even break from it. If the leaves remained on the trees in winter, then much more snow would linger on the branches, since the leaf surface, as we said above, is large. Thus, dropping their leaves in autumn, the trees protect themselves from mechanical damage under the pressure of snow.
Reason three. During leaf fall, the tree gets rid of excess mineral salts that accumulate in the leaves throughout the summer. As we have repeatedly noticed, the sheet intensively evaporates water. To replace this evaporated water, new water constantly enters it, which is sucked in by the roots from the soil. But in the water that the roots get from the soil are dissolved various salts. Thus, the leaves do not receive pure water, but saline solutions. Part of the salts is used by the plant for nutrition, and the rest of the salts are deposited in the cells of the leaves. The more moisture the leaf evaporates, the more it mineralizes by autumn. As a result, by autumn, the leaves accumulate a lot of salts, becoming, as it were, mineralized. An excess of mineral salts disturbs normal work leaves. Therefore, shedding old leaves is necessary condition to keep the plant alive.
By the way...
How do conifers manage not to lose moisture in winter, while remaining green? The secret is that the needles evaporate many times less moisture than the leaves. Firstly, the surface of the needle is many times smaller than the surface of the leaf; secondly, the needles have a thick skin; thirdly, they are covered with a wax coating, which also reduces the evaporation of water. Finally, the stomata in the needles are located in special recesses - this reduces the intensity of moisture evaporation through them.
Coniferous trees also throw off their cover, but not at once, as they do hardwoods, but gradually: coniferous needles live, on average, 3-4 years. Therefore, the change of "clothes" of conifers goes unnoticed.
Autumn is a great time. The fact that it has come can already be judged by the fact that the leaves on the trees and shrubs change their color. At this time, the leaves have an extremely rich palette of colors. Nature herself paints them in different shades, so much so that any artist would envy. Why does this happen every year? Why do trees shed their leaves in autumn? This issue should be examined in more detail.
What assumptions might arise?
Why do trees shed their leaves in autumn? Various associations immediately arise in my head about what is happening:
- The foliage of the trees has grown old, it has become cold, and therefore there is a fall.
- In autumn, the leaves no longer have enough light for their growth.
- The reason that the leaves fall is the wind.
Naturally, all these assumptions are subject to verification to determine the true causes.
What role do leaves play in the life of trees?
The structure of the leaf is represented by two parts: the leaf blade and the petiole, which is its stalk. The structure of the plate is represented by veins. They are especially clearly visible from below. It turns out that they are vessels designed to move water. Each leaf contains green chlorophyll grains. They are so small that they are not visible to the naked eye. Grains can be compared to tiny factories. They are cooking for the whole tree. They build the material from which new branches, buds, roots and, of course, the trunk itself are formed.
They get energy for their production from the sun. The absorption of light by them is carried out throughout the daylight hours. Chlorophyll is unstable and is constantly being destroyed. But at the same time there is a regular recovery. For any sheet is essential. And here yellow leaf the tree does not nourish, but only takes moisture from it.
Why does the color change?
Simultaneously with the destruction of chlorophyll, the process of its restoration takes place. Moreover, the formation of green matter does not lag behind its destruction. As long as there is enough light, there is a certain balance between these processes, an equilibrium. With the onset of autumn, due to the lengthening of nights, daylight hours become shorter. Being destroyed, chlorophyll simply does not have time to recover in a day. Therefore, it is not green that becomes predominant, but yellow. But not only this color there are withering leaves. They can acquire red, crimson, other colors. This is determined by which coloring matter is predominant in the withering leaf.
Foliage also varies in brightness. It depends on what the weather is like in autumn. The abundance of rain causes excessive saturation of the foliage with moisture. From this they become dull in nature. Alder and lilac lose their foliage regardless of the weather. In them, chlorophyll is simply represented by the only coloring matter.
Various folk signs
For many years man has been constantly observing nature. As a result, many folk omens. Many of them are also associated with a change in the color of the foliage:
- If the leaf has turned yellow, but the process of falling off is not expressed, then frost is still far away.
- The trees are covered ahead of time yellow foliage- autumn will be early.
- Despite the snowfall, winter will not come as long as the leaves remain on the cherry tree.
- Bone tree with its leaves is able to predict the weather. Twisting down speaks of good days. Otherwise, the weather will be bad.
- If the leaves appear on the birch earlier than on the alder, then the summer will be windy in nature. If the birch is ahead of the alder, then the summer will be cold and rainy.
- Early spring is predicted by early yellowness at the top of a birch in autumn. If the birch begins to turn yellow from below, then this indicates a late onset of spring.
- The appearance of buds and foliage on the oak before the ash indicates the humidity and coolness of the coming summer. But if the ash is ahead of the oak, then we should expect a warm and dry summer.
The onset of leaf fall
The autumn tree never waits for a command to shed its leaves. This happens spontaneously. Why do trees shed their leaves in autumn? With the onset of coolness, the color of the leaves changes. Petioles also undergo certain changes. The "bricks" of foliage are connected to each other by strong bonds. The leaf is also firmly attached to the branch. It is not so easy, for example, to separate a leaf from a branch near a birch. In autumn, with a change in color, these bonds are destroyed. Therefore, the leaf is very loosely attached to the branch. Sometimes it is enough just to touch him, as he immediately falls.
This is due to the formation of a special cork layer. It seems to separate the petiole from the branch, becoming a real barrier between them. The sheet is fastened only with the help of thin tubes. Therefore, we can conclude that there is not a leaf breaking off from a branch, but a separation in a certain place. This is observed exactly where the formation of the cork layer occurred.
Which trees are the first to shed their leaves in autumn
Calendar autumn begins on the first of September. But by astronomical standards, its beginning is considered the day of the autumn equinox, which falls on September 21. According to phenologists, as soon as the leaves begin to turn yellow and fall, we can talk about the coming autumn.
Which trees shed their leaves first in autumn? The intensity of leaf fall is different. This applies not only to different types trees, but also to different representatives of the same species. The situation depends on many factors and is determined by the nature of the weather, the age of the tree, its individual features. Leaf fall proceeds with a different sequence. For quite a long time, oaks cannot part with their foliage. But after all, the appearance of leaves in them is observed later than in other types of trees. There are individual specimens in which leaves do not fall at all. This phenomenon has not yet been explained by scientists.
The linden, the birch and the elm fall the earliest. They are already susceptible to leaf fall. early autumn. leaf loss different parts wood also occurs unevenly. For example, in a poplar, the large lower branches are the first to lose their leaves. Then the middle part becomes “naked”, and this concerns the top of the head last. Elm or poplar behaves somewhat differently. It begins to lose its leaves, on the contrary, from the top. The crown begins to melt gradually, exposing the trunk more and more.
Some autumn trees retain foliage even with the first frost. This situation is observed in the case of aspen and maple. Only spruce and pine do not shed their needles with the onset of autumn. They will stay green all winter.
Which tree is the last to shed its leaves in autumn?
The phenomenon of leaf fall is associated with a seasonal nature. In this way, plants adapt to winter. Frosts have not yet come, and the foliage of plants has already begun to blaze different colors. In a number of trees, this phenomenon can be observed already in early August. Linden crowns are painted with gilding. It will take 2-3 weeks, and the foliage will literally begin to burn with gold. By this time, a similar outfit is already observed on birch trees. The aspens look as if they were covered with a kumach. Even among the mountain ash, red leaves are visible. By the end of September, the crowns of many trees are bare.
In early October, the weeping willow ends its leaf fall. By the end of September, the leaf fall ended at the elm and bird cherry. Birch, maple and walnut are in no hurry to give up their foliage. Separate leaves on them keep until mid-October. But these are all averages. Naturally, they can change in one direction or another. It depends on the region where the trees grow and the weather conditions that prevailed in this particular autumn.
What is the purpose of leaf fall?
What are the causes of leaf fall in autumn? Trees shed their leaves for a reason. This is their protection from various damages of the mechanical plan. In winter, there are often snowfalls, accompanied by strong wind. From their pressure, not only foliage can suffer, but even branches and trees break. Damage will be even greater if the foliage traps snow with its surface.
Why do trees shed their leaves in autumn? With leaf fall, minerals are removed that have accumulated in sufficient quantities over the summer. For plants, they no longer bring benefits, on the contrary, they can only cause harm. Leaves, falling to the ground, rot and contribute to the return of minerals to the soil. They are good for plants too. This circumstance explains the need for leaf fall. This situation has been going on for millions of years. With the advent of winter, only those trees that shed the maximum number of leaves for the winter turned out to be able to survive.
Should I burn leaves in the fall?
Now I understand why trees shed their leaves in autumn. Should they be burned? The ground is covered with leaves and other parts of trees. All this is defined as bedding. In forests dominated by deciduous trees, it reaches 4 tons per hectare of land. Slightly less of it among pine representatives. The figure is approaching 3.5 tons. It accumulates not just like that, but has a certain value. It contributes to the accumulation of humus and minerals in the composition of the soil. If the litter is loose in nature, then its decomposition occurs easily, and water enters the soil. The process of rotting dense litter takes a very long time and is accompanied by a sour smell. It does not allow the soil and plant roots to freeze strongly.
Due to humus, the soil acquires a dark color, and therefore the sun warms up more strongly. Cooling occurs slowly, which favors the reproduction of beneficial microflora in the soil. If the leaf litter is removed, then the growth of plantations will decrease by 11%.
Why doesn't the needles fall off?
Leaves play an important role in the life of any tree or shrub. They create and accumulate the substances necessary to nourish the tree. Due to the fact that in winter there is not enough light, useful components are intensively consumed and moisture evaporates too intensively.
Growth area coniferous plants is, as a rule, an area where there is a harsh climate. Such plants need enhanced nutrition, and therefore their needles are on winter period do not fall off. They contain a large number of chlorophyll, which converts nutrients. The small area of the needle significantly reduces evaporation. It also has protection from the cold, which is due to the wax coating. Thanks to this, the needles are not able to freeze even in severe frosts.
The only plant with needles that loses foliage for the winter is larch.
evergreens
In such representatives, the foliage does not fall even with the advent of cold weather. They constantly have leaves that can survive any weather conditions. Naturally, their foliage is constantly updated. But it happens gradually. Such plants can be found where the climate is mild and warm in nature. In such places, even in winter it is warm. But they can also be found where the climate is severe. As an example, it is easy to cite the blue one that can be found in California.
Abstract of a lesson in a group preparatory to school, topic: “Do all trees shed their leaves?”
Program content:
1. To form children's ideas about the adaptation of trees to different climatic conditions of growth: southern, northern, to the conditions of hot countries, the jungle.
2. Consolidate and expand the knowledge of children about "coniferous", "deciduous" and "evergreen" trees.
3. Lexical work:
- exercise children in the formation of adjectives from nouns;
- in agreement of numerals with nouns.
4. To educate children in respect for nature and develop interest in it.
Material:
Illustrations, herbarium.
Lesson progress:
Guys, in front of you is a herbarium with different leaves. One of you will make riddles, the rest will guess and find the right leaf in the herbarium. /children take turns guessing/
The Birch Riddle
sticky buds
green leaves
With white bark
It is under the mountain.
/Birch/
Eucalyptus Mystery
It is almost a hundred meters tall:
It's hard to get on it!
He was from Australia
It was brought to us in Colchis.
He has one job
Swamp draining.
/Eucalyptus/
The Oak Mystery
I got out of the crumb-barrel,
Roots started up and grew,
I became tall and powerful
I'm not afraid of thunderstorms or clouds.
I feed pigs and squirrels -
Nothing that the fruit of my chalk.
/Oak/
Spruce Riddle
You can always find her in the forest -
Let's go for a walk and meet
It is prickly, like a hedgehog,
In winter in a summer dress.
/Spruce/
Aspen Riddle
What kind of tree is
There is no wind, but the leaf is trembling.
/Aspen/
Pine Riddle
I have longer needles
Than the tree.
Very straight I grow
In height.
If I'm not at the edge,
Branches - only at the top.
/Pine/
That's right, guys, you guessed it, but how can they be called in one word? /Trees/. What do you think all these trees that you see in the illustrations have in common. /Structure: roots, trunk, branches/. And how do they differ from each other? / Some trees have leaves, others have needles /. You are absolutely right, but what do you think, do all trees shed their leaves in autumn? / No, spruce and pine do not drop /.
Guys, it turns out that all trees can be conditionally divided into:
deciduous trees with leaves, for example, birch, mountain ash, chestnut, etc.
coniferous trees that have needles instead of leaves, for example: spruce, pine, cedar. In another way, they are also called "evergreen", because they are in the northern and southern conditions always remain green, do not shed needles. Not without reason, there are riddles: "In winter and summer in one color." Evergreen trees include southern countries, the jungle, where there is never winter, and the trees do not change or shed their leaves, for example: palm trees, baobabs, sequoias, etc.
Fizminutka "In one dense forest"
In one dense forest
(arms above head from side to side)
There lived a powerful family.
(both palms are clenched into a castle)
They had a huge house
(palms over head in the form of a roof)
And a roof with a dark pipe.
(decree fingers go up)
Smoke from the chimney to the rings
(decree fingers rotate)
Plym - plym - plym.
(snapping fingers)
And you know, guys, it turns out that climatic conditions affect whether to shed leaves or not. In our area, trees shed their leaves because the seasons change: autumn replaces summer, winter replaces autumn. Therefore, trees rest in winter, and grow only in spring and summer. And in the tundra short summer and winters are long and cold, so trees grow very slowly. If we compare our birch and birch in the tundra, then our birch is tall, and there it is dwarf, low.
In the steppe, the trees are also low, because it is hot there, dry winds, and the roots are forced to go far down in search of water, and there is not enough strength to grow the crown. And in the jungle tall trees, with dense crown and big leaves, since there is no winter, a lot of sun, moisture; therefore, trees try to absorb moisture and heat as much as possible. - Now let's play: try to make new words, for example:
birch leaf - birch;
pine needle /what kind?/ - pine needle;
rowan branch / what? / - rowan;
spruce paw / what? / - spruce;
chestnut candle /what?/ - chestnut;
oak acorn /what?/ - oak;
poplar fluff /what?/ - poplar;
cedar cone / what? / - cedar; and etc.
Here are illustrations of trees, let's count them:
one birch, two birches, five birches;
one oak, two oaks, five oaks;
one aspen, two aspens, five aspens;
one cedar, two cedars, five cedars;
one poplar, two poplars, five poplars;
one pine, two pines, five pines;
one spruce, two spruces, five spruces.
Well done guys, you did a very good job.
What do you think are the benefits of trees? / They purify the air, birds live on them, animals feed, create a shadow from the sun /.
How can we protect trees? / Do not make fire, do not litter the forest, do not break branches /.
Guys, we have learned a lot of interesting things about trees, and we really want to tell our parents about it. Do you mind if we publish a newspaper for them? /no/. I think so too.
Lesson analysis:
Guys, please remind us what we talked about in class?
What trees are deciduous?
- What are coniferous evergreens?
Why do some trees shed their leaves while others don't?
- You were very attentive, helped me well, I am very pleased with you.