The upper tier in the oak forest is formed by plants. What plants make up the top tier? Oak Ecosystem: Excursion
Introduction The layering of plants in the oak forest - the first layer - the second layer - the third layer - the fourth layer - the fifth layer Different periods of flowering Ephemeroid plants Pollination, seed dispersal The role of fungi Animals of the oak forest Forest litter Causes of stability of the oak forest
Oak forest is a typical biogeocenosis. As in any other biogeocenosis, its components can be distinguished: 1. Producers - creators of organic matter. These are plants. 2. Consumers - consumers of organic matter. These are animals and mushrooms. 3. Decomposers - destroyers of organic matter. These are bacteria, fungi, some animals. 4. Abiotic factors - climate, soil composition, etc. On the territory Smolensk region oak forests, along with pine forests and spruce forests, belong to primary forests. Primary forests are primary forests. They arose in the postglacial period, 12-15 thousand years ago. There are few primary forests left in the region. There are almost no typical oak forests that could still be found 300 years ago. But in those places where there used to be oak forests, and now a secondary forest is growing, one can see preserved oak forest plants. Sokolya Gora is such a place. Let's get acquainted with the biogeocenosis on Sokolya Gora. table of contents
Plants growing in the forest have different heights. These achieve the possibility of coexistence of light-loving, shade-loving and shade-tolerant plants. Due to layering per unit area, a large number of species can grow. The area of the leaf surface in an oak forest is 7.5 times larger than the surface of the earth on which it grows. As a mirror image of above-ground layering, underground layering exists in the soil. Trees of the first tier have the deepest roots. Consider the tiers of oak forests. table of contents
The first tier is made up of tall trees: pedunculate oak, common ash, rough elm, small-leaved linden. Plants of the first tier are photophilous. They are higher than the rest and therefore absorb maximum light. table of contents
Trees of the first tier Pedunculate oak (summer) Small-leaved linden. The leaves bloom later than the rest of the trees - at the end of May. Demanding on the composition of the soil. Height up to 50 m. Lives up to 1000 years. Height - up to 30 m. Lives up to 400 years. Blooms in July. Good honey plant. One tree at the age of 50 years gives 10-12 kg of honey.
The second tier is made up of trees below the trees of the first tier: sycamore maple, mountain ash, bird cherry, wild apple. This tier also includes the undergrowth of trees of the first tier. Plants of the second tier are photophilous or shade-tolerant. Common mountain ash Bird cherry Height up to 15 m. Lives up to 100 years. The fruit is an apple. Tree or shrub up to 10 m tall. It releases a lot of phytoncides. table of contents
The third tier This tier includes shrubs: warty euonymus, forest honeysuckle, hazel, viburnum, brittle buckthorn, cinnamon rosehip. Plants of the third tier are shade-tolerant. Rosehip cinnamon table of contents
The fourth tier is formed by herbaceous plants: ferns, May lily of the valley, kupena, crow's eye, greenfinch, spreading forest, hairy sedge. These plants are shade loving. They are perennial, have underground organs that reproduce vegetatively. There are few pollinating insects in the forest, few fruits with seeds are formed. Vegetative reproduction is also the adaptation of plants to life in the forest. table of contents
Herbs of the fourth tier
Oak plants bloom in different dates. This can be called tiering in time. Thanks to this, the best pollination of plants is achieved. Four waves of flowering can be distinguished. table of contents
The first wave of flowering Alder In late March - early April, wind-pollinated trees and shrubs bloom. There are no leaves on the trees. Pollen flies freely over long distances. Inflorescences in plants - dangling earrings. Wind-pollinated trees and shrubs include: aspen, poplar, hazel, alder, birch. table of contents
The second wave of flowering The second wave of flowering includes the flowering of snowdrops. In April - early May, the entire forest is flooded with sun. In its rays, a multi-colored carpet of flowers of blue coppice, oak anemone, ranunculus anemone, corydalis, lungwort is clearly visible. These plants are pollinated by insects, which by this time already appear in the forest. table of contents
Ephemeroid plants (second wave of flowering) Snowdrops are photophilous plants. Among them are ephemeroids - perennials with a fast development time. In late May - early June, the aerial part of the ephemeroids dies off, and the seeds have time to ripen. Oak anemone Corydalis Ranunculus anemone Goose onion table of contents
This is what the spring forest looks like when the snowdrops are in bloom. There is a lot of light in the forest. The process of photosynthesis proceeds intensively in the leaves. In underground organs - rhizomes, tubers or bulbs are stored nutrients to bloom next spring. The picture shows an anemone oak
The third wave of flowering At the end of May, the majority of insect-pollinated trees, shrubs, grasses bloom: maple, oak, bird cherry, apple tree, mountain ash, honeysuckle, euonymus, lily of the valley, kupena, raven eye, Zelenchuk. Most plants have white flowers and a strong fragrance. Bird cherry Apple tree White color in the forest twilight is the most noticeable. rowan lily of the valley table of contents
The fourth wave of flowering The fourth wave of flowering includes plants that bloom in summer. In June, the common goutweed, the spreading forest, the forest chickweed, and the amazing violet bloom. Cereals and strawberries bloom on the edges. Most plants are pollinated by insects. Small-leaved linden blooms later than all trees and shrubs - in July and is pollinated by bees. Chickweed forest Common linden
Ash fruits Part of the plants of the first tier is pollinated by the wind and the fruits are spread by the wind (birch, poplar, aspen, ash). Plants of the lower tiers are most often pollinated by insects, and the fruits are distributed with the help of animals: insects, birds, and mammals. The fruits of these plants are juicy, bright, well visible to birds. Many of the plants have fruits with small outgrowths - tidbits for ants, which distribute them. Buckthorn fruits Lily-of-the-valley May
Dependence of seed dispersal on tiers Tier I II Distribution Number of plants (in %) Wind 83 83 Ants III, IV Birds 50 Birds 16 Rodents 13
For a year, oak forest plants produce 10 t / ha of net growth (including root growth). The forest creates its own microclimate: humidity, shading, protection from the wind. That is why so many animals live here. Usually certain species of animals are confined to the plant tiers. Consider typical oak forest animals. table of contents
Animals associated with the first layer Silkworm Black woodpecker Jay This layer is inhabited by birds: chaffinch, song thrush, blue tit, pika. Many insects: leaf beetles, bark beetles, barbels. Nuthatch
Animals confined to the second layer Redstart Oriole Flycatcher In this layer there are many insects, mostly beetles. Squirrel Woodpecker table of contents
Animals confined to the third tier of Warbler Warbler Robin This tier is inhabited by many insects and molluscs. Spiders
Animals confined to the fourth tier Roe deer Elk Wolf Snake Dormouse Frog Fox In this tier there are bees, wasps, bumblebees, hare ants, butterflies and other insects, some species of birds nesting on the ground. There are many mouse-like rodents, among them - forest and yellow-throated mice.
Fallen leaves protect the soil from freezing and rapid evaporation of moisture. Many insects and other animals hibernate in the forest floor. Animals that form detrital food chains feed on forest litter. Bacteria, fungi, protozoa, mites, worms, insects or their larvae contribute to the decomposition of the litter. The bulk of the animals are distributed to a depth of 50 cm. Under 1 square. m of soil inhabited by up to 20,000,000 protozoa, nematode worms, there are up to 50,000.
Causes of Oak Forest Sustainability An enormous number of species of plants, animals, fungi, microorganisms live in an oak forest (according to estimates, more than 10,000 species without microorganisms). The species in the oak forest are linked in a food chain. Food chains are intertwined into a highly complex food web. The disappearance of a species usually does not disrupt the entire system. Self-regulation is well developed in the oak forest. All the diverse population of the forest exists together, without completely destroying each other, but only limiting the number of individuals of each species. In the oak forest, the circulation of substances and the movement of energy are clearly traced. The oak forest is an open system, i.e. it receives energy from outside in the form of solar energy. Organic substances formed during photosynthesis pass through food chains and give the energy stored in them to the vital activity of organisms. Ultimately, the mineralization of substances by decomposers occurs. table of contents
The cycle of substances in the oak forest The energy of the sun Trees, shrubs, herbaceous green plants Rodents (squirrel, wood mouse) Snakes Grain-eating birds (bullfinch, chaffinch, hazel grouse) Birds of prey (hawks, owls) Herbivorous insects (butterfly caterpillars, bark beetles, barbels, leaf beetles Insect-eating birds (chiffchaff, cuckoo, flycatcher) Amphibians (common frog, toad) Ungulates (elk, roe deer, deer, wild boar) Predatory mammals(wolf, fox, weasel, lynx) Consumers of the remains of dead plant and animal organisms (decay bacteria, earthworms, gravedigger beetles, soil protozoa, fungi) (Inorganic substances (mineral salts, etc.)
Conclusions Vadim Shefner You, a man, loving nature, Although sometimes feel sorry for her. In pleasure campaigns Do not trample its fields. In the station bustle of the century You hurry to evaluate it. She is your old, kind doctor, She is an ally of the soul. Do not burn it recklessly And do not exhaust it to the bottom. And remember the simple truth - We are many, but she is one. The adaptation of living organisms to life together is the result of a long evolution. Any species occupies a certain place in the biogeocenosis. The existence of other species depends on it. To preserve all species means to preserve stable biogeocenoses, it means to preserve the biosphere. table of contents
tasks Find answers to the questions (orally): 1. What is the significance of the tiered arrangement of plants in an oak forest? 2. What is the significance of the different flowering periods of oak forest plants? 3. How do the methods of seed dispersal depend on the layer? 4. What role do mushrooms play in an oak forest? 5. Why do many animals live in the oak forest? 6. What is the importance of forest litter in the life of an oak forest? Written assignments 1. Complete the table. Tier Environmental group plants Animal examples 2. Write down two food chains in an oak forest. 3. List the adaptations of plants for living together in an oak forest. 4. Why is the oak forest a sustainable biogeocenosis? 5. Write down the definitions of the terms: epiphytes, ephemeroids. table of contents
Literature 1. 2. 3. 4. 5. 6. M. A. Gulenkova, A. A. Krasnikova Summer field practice in botany. - M., Enlightenment. 1976. Kriksunov E. A., V. V. Pasechnik. Ecology 10 (11) class. - M., Bustard. 2004. A. V. Kulev General biology grade 10. Lesson planning. - Saint Petersburg. Parity. 2001. General biology. Textbook for 9-10 grades. Ed. Yu. I. Polyansky. - M., Enlightenment. 1987. O. V. Petunin Biology lessons in the 11th grade. - Yaroslavl. Development Academy. holding academy. 2003. Lessons in General Biology. Ed. V. M. Korsunskaya. - M., Enlightenment. 1977. Photographs by Yushkova Anastasia, Perlina N. B.
Producers, or manufacturers, are autotrophs, which in the process of life are synthesized from inorganic substances organic compounds using carbon dioxide as a source of carbon. Biomass formed in an ecosystem by autotrophic organisms is called primary products. It serves as food and a source of energy for the rest of the organisms in the community.
The main producers are green plants, although photosynthetic and chemosynthetic bacteria also contribute to the formation of the primary production of the ecosystem. Each large ecosystem or any biogeocenosis is characterized by its own specific plants that carry out photosynthesis, i.e., their producers.
consumers, or consumers, - These are heterotrophic organisms that use the biomass synthesized by producers for their own vital activity. By eating and processing plants, consumers receive energy and form secondary products ecosystems.
Consumers are a variety of living organisms - from microscopic bacteria to large mammals, from protozoa to humans. From the point of view of the structure of the ecosystem and the role that different consumers play in maintaining its equilibrium state, all consumers can be divided into several subgroups, which we will do a little later when we analyze the nutritional relationships of ecosystems.
decomposers, or decomposers, recycle dead organic matter detritus) to mineral compounds that can again be used by producers. Many organisms, such as, for example, earthworms, centipedes, termites, ants, etc., feed on plant and animal remains, and part of the wood rots and decomposes during the life of fungi and bacteria. When fungi and other decomposers die, they themselves turn into detritus and serve as food and energy source for other decomposers.
Thus, despite the diversity of ecosystems, they all have structural similarity. Each ecosystem capable of independent existence has its own producers, different kinds consumers and decomposers (Fig. 76).
Oak ecosystem. Consider, as an example, an oak forest, a very stable terrestrial ecosystem (Fig. 77). The oak grove is a typical broad-leaved forest with a longline structure, in which many hundreds of plant species and several thousand species of animals, microorganisms and fungi coexist.
The upper tree layer is formed by large (up to 20 m) perennial oaks and lindens. These light-loving plants, growing quite freely, create favorable conditions for the formation of the second tree layer, represented by undersized and less light-loving pear, maple, and apple trees.
Rice. 76. Necessary components of an ecosystem
Shrub vegetation is formed under the canopy of two tiers. Hazel, euonymus, viburnum, hawthorn, blackthorn, elder, buckthorn - this is not a complete list of plants that form the third tier up to a height of 2–4 m.
The next, herbaceous layer is made up of numerous shrubs and semi-shrubs, ferns, seedlings of trees and various herbs. Moreover, during the year in the oak forest there is a change in the grass cover. In the spring, when there is still no foliage on the trees and the soil surface is brightly lit, light-loving primroses bloom: lungwort, corydalis, anemone. In the summer they are replaced by shade-tolerant plants.
In the ground layer, which is only a few centimeters high from the soil surface, lichens, mosses, mushrooms, and low grasses grow.
Hundreds of plant species ( producers), using the energy of the sun, create a green biomass of oak forests. Oak forests are very productive: during the year, on an area of 1 hectare, they create up to 10 tons of plant mass growth.
Dead roots and fallen leaves form a litter in which numerous decomposers: earthworms, larvae of flies and butterflies, dung beetles and carnivores, wood lice and centipedes, springtails, mites, nematodes. Feeding, these organisms not only transform detritus, but also form the soil structure. The activity of diggers such as moles, mice and some large invertebrates keeps the soil from caking. Numerous soil protozoa live in drops of water between soil particles, and fungi form a symbiosis with plant roots and participate in the decomposition of detritus.
Rice. 77. Oak forest ecosystem
Despite the fact that annually 3–4 tons of dead plants enter 1 hectare of the soil surface in an oak forest, almost all of this mass is destroyed as a result of the activity of decomposers. A special role in this processing belongs to earthworms, of which there are a huge number in oak forests: several hundred individuals per 1 m2.
The fauna of the upper tiers of the oak forest is diverse. Dozens of species of birds nest in the crowns of trees. Nests are built by magpie and jackdaw, song thrush and chaffinch, great tit and blue tit. In the hollows, the eagle owl and the common owl hatch their chicks. Hobbies and sparrowhawks intimidate small songbirds. The bushes are inhabited by robin and blackbird, pied flycatcher and nuthatch. Even lower are the nests of warbler and wren. A gray squirrel moves along all tiers in search of food. Butterflies, bees, wasps, flies, mosquitoes, beetles - more than 1600 species of insects are closely related to oak! Grasshoppers and beetles, spiders and haymakers, mice, shrews and hedgehogs share their place under the sun in the grass layer. The largest consumers of this ecosystem are roe deer, fallow deer and wild boar.
The stability of this and any other ecosystem is ensured by a complex system of relationships between all the organisms that make up it.
Review questions and assignments
1. What is biogeocenosis?
2. Tell us about the spatial structure of the ecosystem.
3. What are the required components of any ecosystem?
4. In what relationship are the inhabitants of biocenoses with each other? Describe these connections.
5. Describe the species composition and spatial structure of the oak forest ecosystem.
Think! Execute!
1. What are the common features of the biogeocenoses of a deciduous forest and a freshwater reservoir.
2. Is the existence of a biocenosis consisting only of plants possible? Justify your point of view.
3. Do research on the topic "My home as an example of an ecosystem."
4. Develop a tour route that allows you to demonstrate the species, spatial and ecological structures of a typical ecosystem in your region (group project).
Work with computer
Refer to the electronic application. Study the material and complete the assignments.
25. Food connections. Circulation of matter and energy in ecosystems
Remember!
What are the essential components of any ecosystem?
Living organisms are in constant interaction with each other and with environmental factors, forming a stable self-regulating and self-sustaining ecosystem. The features of the species composition of this system are determined by historical and climatic conditions, and the relationships of organisms with each other and with the environment are built on the basis of eating behavior.
In the ecosystem of the oak forest we have considered, deer eat herbaceous plants and leaves of shrubs, squirrels are not averse to eating acorns and mushrooms, and the hedgehog eats earthworm, and the eagle owl on a night hunt catches mice and voles. Numerous insects, oak acorns, wild apple and pear fruits, seeds and berries are excellent food for birds. Dead organic remains fall to the ground. Bacteria develop on them, which are consumed by protozoa, which, in turn, serve as food for numerous small soil invertebrates. All types of organisms are connected with each other by a complex system. food relationships.
When studying the structure of any ecosystem, it becomes obvious that its stability depends on the diversity food links, existing between different species of this community. Moreover, the greater the species diversity, the more stable the structure. Imagine a system in which predator and prey are represented by only single species, let's say "fox - hare". The disappearance of hares will inevitably lead to the death of predators, and the ecosystem, having lost two of its components, will begin to collapse. If, however, a fox can use rodents, frogs, and small birds as food in a given ecosystem, then the loss of one food source will not lead to the destruction of the entire structure, and the vacant ecological niche will soon be occupied by other organisms with similar environmental requirements.
Biogeocenosis is a homogeneous area earth's surface with a certain composition of living organisms and certain living conditions, which are combined by the metabolism and energy into a single natural complex.
In each biogeocenosis, there are species that prevail in number or occupy a large area. They are called dominant species. However, not all dominant species have the same effect on biogeocenosis. Those that determine the composition, structure and properties of an ecosystem by creating an environment for the entire community are called edificators. And now consider the biogeocenosis of the oak forest.
Among the terrestrial biogeocenoses, one of the most complex is a broad-leaved forest, for example, an oak forest. Oak grove is a perfect and stable ecological system capable of existing for centuries under constant external conditions. The biogeocenosis of oak forests consists of more than a hundred species of plants and several thousand species of animals.
Oak plants. In terrestrial biogeocenoses, the main biological products are created by higher plants. In the forest, these are predominantly perennial tree species.
Between plants there is an increased competition for the basic living conditions: space, light, water with minerals dissolved in it. As a result of long natural selection oak forest plants have developed adaptations that allow different types exist together. This is clearly manifested in the layering characteristic of oak forests.
The upper tier is formed by the most light-loving tree species: oak, ash, linden. Below are the less light-loving trees accompanying them: maple, apple, pear, etc. Even lower is the layer of undergrowth formed by various shrubs: hazel, buckthorn, viburnum, etc. Finally, a layer grows on the soil herbaceous plants. The lower the tier, the more shade-tolerant the plants forming it.
Due to the complex layering, the total area of plant leaves growing on each hectare reaches 4–6 hectares. Net production in the form of an increase in organic matter is almost 10 t/ha per year.
Food chains in oak forests. The richness and diversity of plants becomes the reason for the development of consumers from the animal world in oak forests, from the simplest to higher vertebrates - birds and mammals.
Food chains in the forest are intertwined in a very complex food web, so the loss of any one species of animal usually does not significantly disrupt the entire system. The disappearance, for example, in most of our oak forests of all large herbivorous ungulates: bison, deer, roe deer, elk would have little effect on the overall ecosystem, since their biomass has never been large and has not played a significant role in the general circulation of substances. But if herbivorous insects disappeared, the consequences would be very serious, since insects perform an important function of pollinators in biogeocenosis, participate in the destruction of litter and serve as the basis for the existence of many subsequent links in food chains.
Ecological systems
- Biogeocenosis
- Reservoir and oak forest as examples of biogeocenoses
- Changes in biogeocenoses
- Biogeocenoses created by man
- Nutritional connections
- Energy losses in power circuits
Biogeocenosis.
Biogeocenosis is a stable community of plants, animals and microorganisms that are in constant interaction with the components of the atmosphere, hydrosphere and lithosphere. The energy of the Sun, mineral substances of the soil and gases of the atmosphere, water enter this community, and heat, oxygen, carbon dioxide, and waste products of organisms are released from it. The main functions of biogeocenosis are the accumulation and redistribution of energy and the circulation of substances. Biogeocenosis is an integral self-regulating and self-sustaining system. It includes the following mandatory components: inorganic (carbon, nitrogen, carbon dioxide, water, mineral salts) and organic substances (proteins, carbohydrates, lipids, etc.); autotrophic organisms - producers of organic substances; heterotrophic organisms - consumers of ready-made organic substances of plant - consumers (consumers of the first order) and animal (consumers of the second and subsequent orders) origin. Heterotrophic organisms include decomposers - reducers, or destructors, which decompose the remains of dead plants and animals, turning them into simple mineral compounds.
Speaking of biocenoses, only interconnected living organisms that live in a given area are considered. Biocenoses are characterized by species diversity, i.e. the number of species of living organisms that form it; population density, i.e. the number of individuals of a given species, per unit area or per unit volume (for aquatic and soil organisms); biomass - the total amount of animal organic matter, expressed in units of mass.
Biomass is formed as a result of the binding of solar energy. The efficiency with which plants assimilate solar energy varies in different biocenoses. The total production of photosynthesis is called primary production. Plant biomass is used by first-order consumers - herbivorous animals - as a source of energy and material for creating biomass; moreover, it is used extremely selectively (Fig. 17.7), which reduces the intensity of the interspecific struggle for existence and contributes to the conservation of natural resources. Herbivorous animals, in turn, serve as a source of energy and material for consumers of the second order - predators, etc. Figure 17.8 shows comparative data on the productivity of various biogeocenoses. The greatest amount of biomass is formed in the tropics and in the temperate zone, very little - in the tundra and the ocean.
Organisms that are part of biogeocenoses are influenced by inanimate nature - abiotic factors, as well as from wildlife - biotic influences.
Biocenoses are integral, self-regulating biological systems, which include living organisms living in the same territory.
Energy sunlight assimilated by plants, which are subsequently used by animals as food.
Nutritional connections .
Energy losses in power circuits
All species that make up the food chain subsist on the organic matter created by green plants. In this case, there is an important regularity associated with the efficiency of the use and conversion of energy in the process of nutrition. Its essence is as follows.
In total, only about 1% of the radiant energy of the Sun falling on the plant is converted into potential energy. chemical bonds synthesized organic substances and can be further used by heterotrophic organisms for nutrition. When an animal eats a plant, most of the energy contained in the food is spent on various processes life activity, while turning into heat and dissipating. Only 5-20% of food energy passes into the newly built substance of the animal's body. If a predator eats a herbivore, then again most of the energy contained in the food is lost. Due to such large losses of useful energy, food chains cannot be very long: they usually consist of no more than 3-5 links (food levels).
The amount of plant matter that serves as the basis of the food chain is always several times greater than the total mass of herbivorous animals, and the mass of each of the subsequent links in the food chain also decreases HH o This very important pattern is called the rule of the ecological pyramid.
Reservoir and oak forest as examples of biogeocenoses
1. Biogeocenosis of fresh water.
Any natural body of water, such as a lake or a pond, with its plant and animal population is a separate biogeocenosis. This natural system, like other biogeocenoses, has the ability for self-regulation and continuous self-renewal.
Plants and animals inhabiting the reservoir are unevenly distributed in it. Each species lives in the conditions to which it is adapted. The most diverse and favorable conditions for life are created in the coastal zone. Here the water is warmer, as it warms up with the sun's rays. It is sufficiently oxygenated. The abundance of light penetrating to the bottom ensures the development of many higher plants. Small algae are also numerous. Most of the animals live in the coastal zone. Some are adapted to life on aquatic plants, others actively swim in the water column (fish, predatory swimming beetles and water bugs). Many are found at the bottom (barley, toothless, larvae of some insects - caddisflies, dragonflies, mayflies, a number of worms, etc.). Even the surface film of water serves as a habitat for species specially adapted to it. In quiet backwaters, you can see predatory water strider bugs running on the surface of the water and swirling beetles swimming quickly in circles. The abundance of food and other favorable conditions attract fish to the coastal zone.
In the deep near-bottom parts of the reservoir, where sunlight weakly penetrates, life is poorer and more monotonous. Photosynthetic plants cannot exist here. The lower layers of water remain cold due to weak mixing. Here the water contains little oxygen.
Special conditions are also created in the thickness of the water in open areas of the reservoir. It is inhabited by a mass of the smallest plant and animal organisms, which are concentrated in the upper, warmer and well-lit layers of water. Various microscopic algae develop here; algae and bacteria feed on numerous protozoa - ciliates, as well as rotifers and crustaceans. This whole complex of small organisms suspended in water is called plankton. In the circulation of substances and in the life of a reservoir, plankton plays a very important role.
2. Food connections and stability of pond biogeocenosis.
Consider, due to what the system of inhabitants of the reservoir exists and how it is maintained. Food chains consist of several consecutive links. For example, plant residues and bacteria developing on them are fed by protozoa, which are eaten by small crustaceans. The crustaceans, in turn, serve as food for fish, and the latter can be eaten by predatory fish. Almost all species do not feed on one type of food, but use different food objects. Food chains are intricately intertwined. An important general conclusion follows from this: if any member of the biogeocenosis falls out, then the system is not disturbed, since other food sources are used. The greater the species diversity, the more stable the system.
The primary source of energy in aquatic biogeocenosis, as in most ecological systems, is sunlight, thanks to which plants synthesize organic matter. Obviously, the biomass of all animals existing in a reservoir completely depends on the biological productivity of plants.
Often the reason for the low productivity of natural water bodies is the lack of minerals (especially nitrogen and phosphorus) necessary for the growth of autotrophic plants, or the unfavorable acidity of the water. Application mineral fertilizers, and in the case of an acidic environment, liming of water bodies contributes to the reproduction of plant plankton, which feed on animals that serve as food for fish. In this way, the productivity of fishery ponds is increased.
3. Biogeocenosis of broad-leaved forest.
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Among the terrestrial biogeocenoses, one of the most complex is a broad-leaved forest, such as an oak forest. oak brava - a perfect and stable ecological system capable of existing for centuries under constant external conditions. The biogeocenosis of oak forests consists of more than a hundred species of plants and several thousand species of animals.
oak forest plants
In terrestrial biogeocenoses, higher plants create the main biological products. In the forest, these are predominantly perennial tree species (Figure 39).
Figure 39. Biogeocenosis of a broad-leaved forest.Characteristic deciduous forest lies in the species diversity of vegetation. Between plants there is an increased competition for the basic living conditions: space, light, water with minerals dissolved in it. As a result of long-term natural selection, oak forest plants have developed adaptations that allow different species to exist together. This is clearly manifested in the layering characteristic of oak forests.
The upper tier is formed by the most light-loving tree species: oak, ash, linden. Below are the less light-loving trees accompanying them: maple, apple, pear, etc. Even lower is the undergrowth layer formed by various shrubs: hazel, euonymus, buckthorn, viburnum, etc.
Finally, a layer of herbaceous plants grows on the soil. The lower the tier, the more shade-tolerant the plants forming it.
Layering is also expressed in the location of root systems. The trees of the upper tiers have the deepest root system and can use water and minerals from the deep layers of the soil.
The oak forest is characterized by high biological productivity. Due to its complex multilayered, the total area of leaves of plants growing on each hectare reaches 4-6 hectares. Such a powerful photosynthetic apparatus captures and transforms about 1% of the annual influx of solar radiation into potential energy of organic matter. The latter in the middle latitudes is about 3.8 10 7 kJ/ha. Almost half of the synthesized substance is consumed by the plants themselves in the process of respiration. Net production in the form of an increase in organic matter in the aboveground parts of plants is 5-6 t/ha per year. To this should be added 3-4 t/ha of annual growth of underground parts. Thus, the production of oak forests reaches almost 10 t/ha per year.
Food chains in oak forests.
The richness and diversity of plants that produce a huge amount of organic matter that can be used as food, become the reason for the development in oak forests of numerous consumers from the animal world, from protozoa to higher vertebrates - birds and mammals.
Food chains in the forest are intertwined in a very complex food web, so the loss of any one species of animal usually does not significantly disrupt the entire system. The value of different groups of animals in the biogeocenosis is not the same. The disappearance, for example, in most of our oak forests of all large herbivorous ungulates; bison, deer, roe deer, elk - would have little effect on the overall ecosystem, since their numbers, and therefore biomass, have never been large and have not played a significant role in the general circulation of substances. But if herbivorous insects disappeared, the consequences would be very serious, since insects perform an important function of pollinators in biogeocenosis, participate in the destruction of litter and serve as the basis for the existence of many subsequent links in food chains.
Self-regulation in forest biogeocenosis.
The process of self-regulation in the oak forest is manifested in the fact that the entire diverse population of the forest exists together, without completely destroying each other, but only limiting the number of individuals of each species to a certain level. The importance of such population regulation in the life of a forest can be seen from the following example. Several hundred species of insects feed on oak leaves, but under normal conditions, each species is represented by such a small number of individuals that even their common activity does not cause significant harm to the tree and forest. Meanwhile, all insects are highly prolific. The number of eggs laid by one female is rarely less than 100. Many species are capable of producing 2-3 generations per summer. Consequently, in the absence of limiting factors, the number of any kind of insect would increase very quickly and would lead to the destruction of the ecological system.
Mineralization of organic residues.
Of great importance in the life of the forest are the processes of decomposition and mineralization of the mass of dying leaves, wood, animal remains and their metabolic products. Of the total annual increase in the biomass of aboveground parts of plants, about 3-4 tons per 1 ha naturally die off and fall off, forming the so-called forest litter. A significant mass is also made up of dead underground parts of plants. With the litter, most of the minerals and nitrogen consumed by plants return to the soil.
Animal remains are very quickly destroyed by dead beetles, skin beetles, larvae of carrion flies and other insects, as well as putrefactive bacteria. It is more difficult to decompose cellulose and other durable substances that make up a significant part of plant litter. But they also serve as food for a number of organisms, such as fungi and bacteria, which have special enzymes that break down fiber and other substances into easily digestible sugars.
Figure 40. Comparison of the general structure of terrestrial and aquatic biogeocenoses:
I - plants producing organic matter: a - higher plants; b - algae;
II - animals - consumers of organic matter: a - herbivorous, b - carnivorous, c - eating mixed food.
As soon as the plants die, their substance is completely used by the destroyers. A significant part of the biomass is made up of earthworms, which do a great job of decomposing and moving organic matter in the soil. The total number of insects, shell mites, worms and other invertebrates reaches many tens and even hundreds of millions per hectare. The role of bacteria and lower, saprophytic fungi is especially great in the decomposition of litter.
OAK ECOSYSTEM: EXCURSION
1. Oak forest as a natural community (biogeocenosis), is one of the most complex among terrestrial biogeocenoses. Well, firstly, what is biogeocenosis? Biogeocenosis is a complex of interconnected species (populations of different species) living in a certain area with more or less uniform conditions of existence. This definition will be needed for later use. Oak forest is a perfect and stable ecological system capable of existing for centuries under constant external conditions. The biogeocenosis of oak forests consists of more than a hundred species of plants and several thousand species of animals. It is clear that with such a variety of species inhabiting the oak forest, it will be difficult to shake the stability of this biogeocenosis by exterminating one or more species of plants or animals. It is difficult, because as a result of the long coexistence of plant and animal species from disparate species, they became a single and perfect biogeocenosis - an oak forest, which, as mentioned above, is capable of existing for centuries under unchanged external conditions.
2. The main components of biogeocenosis and the relationship between them; Plants are the main link in an ecosystem. The vast majority of biogeocenosis is based on green plants, which, as you know, are the producer of organic matter (producers). And since in the biogeocenosis there are necessarily herbivorous and carnivorous animals - consumers of living organic matter (consumers) and, finally, destroyers of organic residues - mainly microorganisms that bring the breakdown of organic substances to simple mineral compounds (decomposers), it is not difficult to guess why plants are the main link in the ecosystem. But because in the biogeocenosis everyone consumes organic substances, or compounds formed after the decay of organic substances, and it is clear that if plants - the main source of organic matter disappear, then life in the biogeocenosis will practically disappear.
3. Circulation of substances in biogeocenosis. Significance in the cycle of plants using solar energy The cycle of substances in biogeocenosis - necessary condition the existence of life. It arose in the process of the formation of life and became more complicated in the course of the evolution of living nature. On the other hand, in order for the circulation of substances to be possible in the biogeocenosis, it is necessary to have organisms in the ecosystem that create organic substances from inorganic substances and convert the energy of the sun's radiation, as well as organisms that use these organic substances and again turn them into inorganic compounds. All organisms are divided into two groups according to the method of nutrition - autotrophs and heterotrophs. Autotrophs (mainly plants) use inorganic compounds to synthesize organic substances. environment. Heterotrophs (animals, humans, fungi, bacteria) feed on ready-made organic substances synthesized by autotrophs. Therefore, heterotrophs depend on autotrophs. In any biogeocenosis, all reserves of inorganic compounds would very soon run out if they were not renewed in the course of the life of organisms. As a result of respiration, decomposition of animal corpses and plant residues, organic substances turn into inorganic compounds, which return back to the natural environment and can again be used by autotrophs. Thus, in the biogeocenosis, as a result of the vital activity of organisms, there is a continuous flow of atoms from inanimate nature to living nature and vice versa, closing in a cycle. For the circulation of substances, an influx of energy from the outside is necessary. The source of energy is the sun. The movement of matter caused by the activity of organisms occurs cyclically, it can be used repeatedly, while the flow of energy in this process is unidirectional. The radiation energy of the Sun in the biogeocenosis is converted into various forms: into the energy of chemical bonds, into mechanical and, finally, into internal. From all that has been said, it is clear that the circulation of substances in biogeocenosis is a necessary condition for the existence of life and plants (autotrophs) in it the most important link.
4. Diversity of species in the biogeocenosis, their adaptability to living together. A characteristic feature of the oak forest is the species diversity of vegetation. As mentioned above, the biogeocenosis of oak forests consists of more than a hundred plant species and several thousand animal species. Between plants there is an increased competition for the basic living conditions: space, light, water with minerals dissolved in it. As a result of long-term natural selection, oak forest plants have developed adaptations that allow different species to exist together. This is clearly manifested in the layering characteristic of oak forests. The upper tier forms the most light-loving tree species: oak, ash, linden. Below are the less light-loving trees accompanying them: maple, apple, pear, etc. Even lower is the undergrowth layer formed by various shrubs: hazel, euonymus, buckthorn, viburnum, etc. Finally, a layer of herbaceous plants grows on the soil. The lower the tier, the more shade-tolerant the plants forming it. Layering is also expressed in the location of root systems. The trees of the upper tiers have the deepest root system and can use water and minerals from the deep layers of the soil.
7. Changes in biogeocenosis in spring: in the life of plants and animals.
Spring changes in plant life.
Some willows, alders, and hazels are blooming before their leaves have opened; on thawed patches, even through the snow, sprouts of the first spring plants. By mid-spring, almost all trees have leaves. The flowering period of plants and flowers. In general, plants come alive from winter calm.
Spring changes in the life of animals.
Migratory birds arrive, overwintered insects appear, some animals wake up from hibernation. The period of formation of pairs and the marriage period.
8. Possible directions of biogeocenosis change. Any biogeocenosis develops and evolves. The leading role in the process of changing terrestrial biogeocenoses belongs to plants, but their activity is inseparable from the activity of the other components of the system, and the biogeocenosis always lives and changes as a whole. The change goes in certain directions, and the duration of the existence of various biogeocenoses is very different. An example of a change in an insufficiently balanced system is the overgrowth of a reservoir. Due to the lack of oxygen in the bottom water layers, part of the organic matter remains unoxidized and is not used in the further circulation. In the coastal zone, the remains of aquatic vegetation accumulate, forming peaty deposits. The pond is shrinking. Coastal aquatic vegetation spreads to the center of the reservoir, peat deposits are formed. The lake gradually turns into a swamp. The surrounding terrestrial vegetation is gradually advancing on the site of the former reservoir. Depending on local conditions, a sedge meadow, a forest, or another type of biogeocenosis may appear here. Oak forest can also turn into a different type of biogeocenosis. For example, after cutting down trees, it can turn into a meadow, a field (agrocenosis) or something else.
9. Influence of human activity on biogeocenosis; measures to be taken to protect it. Man has recently become very active in influencing the life of biogeocenosis. The economic activity of people is a powerful factor in the transformation of nature. As a result of this activity, peculiar biogeocenoses are formed. These include, for example, agrocenoses, which are artificial biogeocenoses resulting from human agricultural activities. Examples are artificially created meadows, fields, pastures. Artificial biogeocenoses created by man require tireless attention and active intervention in their life. Of course, there are many similarities and differences in artificial and natural biogeocenoses, but we will not dwell on this. A person also influences the life of natural biogeocenoses, but, of course, not as much as on agrocenoses. Forest areas created for planting young trees, as well as for limiting hunting, can serve as an example. Reserves and national parks created to protect certain species of plants and animals can also serve as an example. Mass societies are also being created that promote the preservation and protection of the environment, such as the "green" society, etc.
10. Conclusion. Using the example of an excursion walk through a natural biogeocenosis - an oak forest, they found out and disassembled why the oak forest is integral and stable, what are the main components of a biogeocenosis, what is their role and what connections exist between them, they also disassembled why the circulation of substances in a biogeocenosis is a necessary condition for the existence of life, they also found out how the whole variety of species living in an oak forest does not conflict with each other, allowing each other to develop normally, we sorted out what food connections exist in an oak forest and sorted out such a concept as an ecological pyramid, substantiated the factors causing a change in numbers and such a phenomenon as self-regulation, found out which changes occur in the biogeocenosis in the spring and sorted out the possible directions of evolution of the biogeocenosis, as well as how a person affects life in biogeocenoses. In general, on the example of oak forests, the life of biogeocenoses was completely dismantled.
The life of forest plants has its own characteristics. The trees that form the forest grow more or less close together, influencing each other and the rest of the forest vegetation. Plants in the forest are arranged in tiers, which can be compared to floors. The upper, first tier is represented by the main trees of the first degree of significance (spruce, pine, oak). The second tier is formed by trees of the second size (bird cherry, mountain ash, apple tree). The third tier consists of shrubs, for example, wild rose, hazel, viburnum, euonymus. The fourth tier is a herbaceous cover, and the fifth is mosses and lichens. The access of light to plants of different tiers is not the same. The crowns of the trees of the first tier are better lit. From the upper to the lower tiers, the illumination decreases, as the plants of the upper tiers delay the proportion sun rays. Mosses and lichens occupying the fifth tier receive a very small amount of light. These are the most shade-tolerant plants in the forest.
Different forests have a different number of tiers. For example, in a dark spruce forest, only two or three tiers are distinguishable. On the first tier are the main trees (spruces), on the second - a small number of herbaceous plants, and the third is formed by mosses. Other woody and shrubby plants do not grow in the second tier of the spruce forest, as they cannot stand strong shading. Also, grass cover is not observed in the spruce forest.
The tiered arrangement is characteristic not only for the aboveground parts of plants, but also for their underground organs - the roots. Tall trees have roots that penetrate deep into the ground, while the root system of trees of the second tier is shorter and forms a conditionally second tier of roots. The roots of other forest plants are even shorter and are located in the upper layers of the soil. Thus, plants in the forest absorb nutrients from different soil layers.
Trees of the first magnitude (oak, pine, spruce) close with their crowns and form a forest canopy, under which a small fraction of sunlight penetrates. Therefore, the herbaceous plants of the forest, as a rule, are shade-tolerant and have wide leaf blades. Many of them do not withstand exposure to direct sunlight and may die in open space. A feature of grasses of a broad-leaved forest is flowering in early spring when there are no leaves on the trees yet. With the help of broad leaves, forest plants accumulate organic matter in low light and deposit them in underground organs, for example, lungwort in rhizomes. In gloomy spruce thickets, flowers of herbaceous plants have corollas white color so that they can be seen from afar by pollinating insects. For example, such flowers are found in lily of the valley, wintergreen, septenary, gout, minik. But, despite these adaptations, the flowers of forest grasses often do not pollinate and do not form seeds. Therefore, the reproduction of many herbaceous plants is carried out by dividing the rhizomes, for example, in oxalis, lily of the valley, kupena, sedmichnik, minnik. This explains the placement of these herbs in groups in the forest.
Forest litter covering the soil consists of fallen leaves or needles, respectively, in deciduous or coniferous forests, as well as bark and branches of trees, dead grass patches, mosses. Loose forest litter is moist, which is favorable for the development of molds and hat fungi. Myceliums of various fungi densely permeate the litter, gradually converting organic matter into humus and mineral salts to feed the green plants of the forest.
Oak grove, as a natural community (biogeocenosis), is characterized by integrity and stability.
Oak forest is one of the most complex among terrestrial biogeocenoses. Biogeocenosis- these are complexes of interconnected species (populations of different species) living on certain territory with more or less uniform conditions of existence. The biogeocenosis of oak forests consists of more than a hundred species of plants and several thousand species of animals. It is clear that with such a variety of species inhabiting the oak forest, it will be difficult to shake the stability of this biogeocenosis by exterminating one or more species of plants or animals. It is difficult, because as a result of the long coexistence of plant and animal species from disparate species, they became a single and perfect biogeocenosis - an oak forest, which, as mentioned above, is capable of existing for centuries under unchanged external conditions.
The vast majority of biogeocenosis is based on green plants, which, as you know, are producers of organic matter (producers). In the biogeocenosis, herbivorous and carnivorous animals are necessarily present - consumers of living organic matter (consumers) and, finally, destroyers of organic residues - mainly microorganisms that reduce the breakdown of organic substances to simple mineral compounds (reducers). Plants are the main source of organic matter, and if they disappear, then life in the biogeocenosis will practically disappear.
The circulation of substances in biogeocenosis is a necessary condition for the existence of life. It arose in the process of the formation of life and became more complicated in the course of the evolution of living nature. On the other hand, in order for the circulation of substances to be possible in the biogeocenosis, it is necessary to have organisms in the ecosystem that create organic substances from inorganic substances and convert the energy of the sun's radiation, as well as organisms that use these organic substances and again turn them into inorganic compounds. All organisms are divided into two groups according to the method of nutrition - autotrophs and heterotrophs. Autotrophs (mainly plants) use inorganic compounds from the environment to synthesize organic substances. Heterotrophs (animals, humans, fungi, bacteria) feed on ready-made organic substances synthesized by autotrophs. Therefore, heterotrophs depend on autotrophs. In any biogeocenosis, all reserves of inorganic compounds would very soon run out if they were not renewed in the course of the life of organisms. As a result of respiration, decomposition of animal corpses and plant residues, organic substances turn into inorganic compounds, which return back to the natural environment and can again be used by autotrophs. Thus, in the biogeocenosis, as a result of the vital activity of organisms, there is a continuous flow of atoms from inanimate nature to living nature and vice versa, closing in a cycle. For the circulation of substances, an influx of energy from the outside is necessary. The source of energy is the sun. The movement of matter caused by the activity of organisms occurs cyclically, it can be used repeatedly, while the flow of energy in this process is unidirectional. The radiation energy of the Sun in the biogeocenosis is converted into various forms: into the energy of chemical bonds, into mechanical and, finally, into internal. From all that has been said, it is clear that the circulation of substances in biogeocenosis is a necessary condition for the existence of life and plants (autotrophs) in it the most important link.
A characteristic feature of the oak forest is the species diversity of vegetation. As mentioned above, the biogeocenosis of oak forests consists of more than a hundred plant species and several thousand animal species. Between plants there is an increased competition for the basic living conditions: space, light, water with minerals dissolved in it. As a result of long-term natural selection, oak forest plants have developed adaptations that allow different species to exist together. This is clearly manifested in the layering characteristic of oak forests. The upper tier is formed by the most light-loving tree species: oak, ash, linden. Below are the less light-loving trees accompanying them: maple, apple, pear, etc. Even lower is the undergrowth layer formed by various shrubs: hazel, euonymus, buckthorn, viburnum, etc. Finally, a layer of herbaceous plants grows on the soil. The lower the tier, the more shade-tolerant the plants forming it. Layering is also expressed in the location of root systems. The trees of the upper tiers have the deepest root system and can use water and minerals from the deep layers of the soil.
