Oak forest, as a natural community (biogeocenosis), is characterized by integrity and stability.
Oak grove is one of the most complex among terrestrial biogeocenoses. Biogeocenosis- these are complexes of interconnected species (populations of different species) living in a certain territory with more or less homogeneous living conditions. The oak forest biogeocenosis consists of more than a hundred plant species and several thousand animal species. It is clear that with such a diversity of species inhabiting the oak forest, it will be difficult to shake the stability of this biogeocenosis by exterminating one or several 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 external conditions exist for centuries.
The basis of the vast majority of biogeocenosis are green plants, which, as is known, are producers of organic matter (producers). In a 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). Plants - main source organic matter and if they disappear, then life in the biogeocenosis will practically disappear.
The circulation of substances in biogeocenosis - necessary condition existence of life. It arose in the process of the formation of life and became more complex during the evolution of living nature. On the other hand, in order for the circulation of substances to be possible in a biogeocenosis, it is necessary to have in the ecosystem organisms that create organic substances from inorganic ones and convert the energy of solar radiation, as well as organisms that use these organic substances and again convert them into inorganic substances. organic compounds. All organisms are divided into two groups according to their 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 that were synthesized by autotrophs. Therefore, heterotrophs depend on autotrophs. In any biogeocenosis, all reserves of inorganic compounds would very soon dry up if they were not renewed during the life activity of organisms. As a result of respiration, decomposition of animal corpses and plant remains, organic substances are transformed into inorganic compounds, which are returned back to natural environment and can again be used by autotrophs. Thus, in a biogeocenosis, as a result of the vital activity of organisms, there is a continuous flow of atoms from inanimate nature to living nature and back, closing in a cycle. For the circulation of substances, an influx of energy from 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 many times, while the flow of energy in this process is unidirectional. The radiation energy of the Sun in biogeocenosis is converted into various shapes: 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 a biogeocenosis is a necessary condition for the existence of life and plants (autotrophs); the most important link in it.
A characteristic feature of the oak forest is the species diversity of vegetation. As mentioned above, the oak forest biogeocenosis consists of more than a hundred plant species and several thousand animal species. There is intense competition between plants 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 accompanying less light-loving trees: maple, apple, pear, etc. Even lower is the undergrowth layer, formed by various shrubs: hazel, euonymus, buckthorn, viburnum, etc. Finally, a layer grows on the soil herbaceous plants. The lower the tier, the more shade-tolerant the plants that form it. Tiering is also expressed in the location of root systems. Trees in the upper layers have the deepest root system and can use water and minerals from the deeper layers of the soil.
Producers, or manufacturers, - these are autotrophs that, in the process of life activity, synthesize organic compounds from inorganic substances, using them as a carbon source carbon dioxide. 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 primary production of the ecosystem. Each large ecosystem or any biogeocenosis is characterized by its own specific plants that carry out photosynthesis, i.e., its own producers.
Consumers, or consumers, – these are heterotrophic organisms that use biomass synthesized by producers for their own life activities. By eating and processing plants, consumers obtain energy and form secondary products ecosystems.
Consumers are a wide 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 played by different consumers in maintaining its equilibrium state, all consumers can be divided into several subgroups, which we will do a little later, when we analyze the food connections of ecosystems.
decomposers, or decomposers, recycle dead organic matter ( detritus) to mineral compounds, which can again be used by producers. Many organisms, such as, for example, earthworms, millipedes, termites, ants, etc., feed on plant and animal debris, and some of the wood rots and decomposes during the activity of fungi and bacteria. When fungi and other decomposers die, they themselves turn into detritus and serve as food and a source of energy 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 forest ecosystem. Let's take an oak forest as an example - a very stable terrestrial ecosystem (Fig. 77). An oak grove is a typical broad-leaved forest with a layered 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 a second tree layer, represented by low-growing and less light-loving pear, maple, and apple trees.
Rice. 76. Necessary components of an ecosystem
Shrub vegetation forms under the canopy of two tiers. Hazel, euonymus, viburnum, hawthorn, blackthorn, elderberry, 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 consists of numerous shrubs and subshrubs, ferns, tree shoots and various herbs. Moreover, throughout the year, the grass cover in the oak grove changes. In the spring, when there is no foliage on the trees yet and the surface of the soil is brightly lit, light-loving primroses bloom: lungwort, corydalis, anemone. In the summer they are replaced shade-tolerant plants.
In the ground layer, the height of which is only a few centimeters from the soil surface, lichens, mosses, mushrooms, and low grasses grow.
Hundreds of plant species ( producers), using the energy of the sun, create green oak forest biomass. Oak groves are very productive: over the course of a 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, woodlice and centipedes, springtails, mites, nematodes. By feeding, these organisms not only transform detritus, but also form soil structure. The activity of diggers such as moles, mice and some large invertebrates prevents 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 every year 3–4 tons of dead plants fall onto 1 hectare of 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, which are found in oak forests. great amount: several hundred individuals per 1 m2.
Diverse animal world the upper tiers of the oak forest. Dozens of bird species nest in the treetops. Magpies and jackdaws, song thrushes and chaffinches, great tits and blue tits build nests. Eagle owls and tawny owls hatch chicks in hollows. Hobbies and sparrowhawks intimidate small songbirds. The bushes are home to Robins and Blackbirds, Pied Flycatchers and Nuthatch. Even lower are the nests of warblers and wrens. The gray squirrel moves along all tiers in search of food. Butterflies, bees, wasps, flies, mosquitoes, beetles - more than 1,600 species of insects are closely associated with oak! In the grass layer, grasshoppers and beetles, spiders and haymakers, mice, shrews and hedgehogs share their place in the sun. The largest consumers This ecosystem includes roe deer, fallow deer and wild boar.
The stability of this and any other ecosystem is ensured by a complex system of relationships among 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 essential components does any ecosystem include?
4. What are the relationships between the inhabitants of biocenoses? Describe these connections.
5. Describe the species composition and spatial structure of the oak forest ecosystem.
Think! Do it!
1. Name common features biogeocenoses of deciduous forest and freshwater reservoir.
2. Is it possible for a biocenosis consisting only of plants to exist? Justify your point of view.
3. Do research on the topic “My home as an example of an ecosystem.”
4. Develop a tour that demonstrates 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. Cycle 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 factors external environment, forming a stable self-regulating and self-sustaining ecosystem. 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 environment are built on the basis eating behavior.
In the oak forest ecosystem we examined, deer eat herbaceous plants and leaves of shrubs, squirrels are not averse to eating acorns and mushrooms, a hedgehog eats an earthworm, and an eagle owl catches mice and voles on its night hunt. 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 related to each other complex system food relationships.
When studying the structure of any ecosystem, it becomes obvious that its stability depends on diversity food connections, 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 only by single species, 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 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 vacated ecological niche will soon be occupied by other organisms with similar environmental requirements.
Introduction Layering of plants in an oak forest - first tier - second tier - third tier - fourth tier - fifth tier Different flowering times Ephemeral plants Pollination, seed distribution The role of fungi Animals of the oak forest Forest litter Reasons for the stability of the oak forest Cycle of substances in the oak forest Conclusions Assignments
A typical biogeocenosis is an oak forest. 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 are destroyers of organic matter. These are bacteria, fungi, and some animals. 4. Abiotic factors - climate, soil composition, etc. On the territory of the Smolensk region, oak forests, along with pine forests and spruce forests, belong to primary forests. Primary forests are indigenous forests. They arose in the post-glacial period, 12-15 thousand years ago. There are few primary forests left in the region. The typical oak forests that could still be found 300 years ago are now almost non-existent. But in those places where there used to be oak forests, and now secondary forest grows, you can see preserved oak forest plants. Sokolya Mountain is such a place. Let's get acquainted with the biogeocenosis on Sokolya Mountain. table of contents
Plants growing in the forest have different heights. This allows for the coexistence of light-loving, shade-loving and shade-tolerant plants. Thanks to the layering per unit area, it is possible to grow large quantity species. The leaf surface area in an oak forest is 7.5 times greater than the surface of the earth on which it grows. As a mirror image of the above-ground layering, there is an underground layering in the soil. Trees of the first tier have the deepest roots. Let's look at the tiers of the oak forest. table of contents
The first tier consists of tall trees: English oak, common ash, rough elm, small-leaved linden. Plants of the first tier are light-loving. They are taller than others and therefore absorb maximum light. table of contents
Trees of the first tier English oak (summer) Small-leaved linden. The leaves bloom later than other trees - at the end of May. Demanding on soil composition. Height up to 50 m. Lives up to 1000 years. Height – up to 30 m. Lives up to 400 years. Blooms in July. A good honey plant. One tree at the age of 50 years produces 10 -12 kg of honey.
The second tier consists of trees lower than the trees of the first tier: sycamore maple, mountain ash, bird cherry, wild apple tree. The undergrowth of trees of the first tier also belongs to this tier. Plants of the second tier are light-loving or shade-tolerant. Rowan common bird cherry ordinary height up to 15 m. Lives up to 100 years. The fruit is an apple. Tree or shrub up to 10 m tall. Releases a lot of phytoncides. table of contents
Third tier This tier includes shrubs: warty euonymus, forest honeysuckle, hazel, viburnum, brittle buckthorn, cinnamon rose hips. Plants of the third tier are shade-tolerant. Rosehip cinnamon table of contents
The fourth tier is formed by herbaceous plants: ferns, lily of the valley, kupena, crow's eye, green grass, spreading boron, hairy sedge. These plants are shade-loving. They are perennial and have underground organs that they use to reproduce vegetatively. There are few pollinating insects in the forest, and few fruits and seeds are produced. Vegetative propagation is also an adaptation of plants to life in the forest. table of contents
Herbs of the fourth tier Lungwort indistinct Male shieldweed Blue coppice Crow's eye Kupena officinalis European hoofhoof
Oak forest plants bloom at different times. This can be called tiering in time. Thanks to this, better plant pollination is achieved. Four waves of flowering can be distinguished. table of contents
The first wave of flowering Alder At the end of March - beginning of April, wind-pollinated trees and shrubs bloom. There are no leaves on the trees. Pollen flies freely over long distances. The inflorescences of the plants are pendulous catkins. Wind-pollinated trees and shrubs include: aspen, poplar, hazel, alder, and 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, wood anemone, ranunculus anemone, corydalis, and lungwort is clearly visible. These plants are pollinated by insects, which by this time already appear in the forest. table of contents
Plants - ephemeroids (second wave of flowering) Snowdrops are light-loving plants. Among them there are ephemeroids - perennials with a rapid development period. At the end of May - beginning of June, the aboveground part of the ephemeroids dies off, and the seeds have time to ripen. Oak anemone Corydalis Anemone buttercup Goose onion table of contents
This is what a spring forest looks like when the snowdrops are blooming. There is a lot of light in the forest. The process of photosynthesis occurs intensively in the leaves. Nutrients for flowering are stored in underground organs - rhizomes, tubers or bulbs next spring. The photo shows the oak anemone
The third wave of flowering At the end of May, most insect-pollinated trees, shrubs, and herbs bloom: maple, oak, bird cherry, apple tree, rowan, honeysuckle, euonymus, lily of the valley, kupena, crow's eye, green cherry. Most plants have white flowers and strong aroma. Bird cherry Apple tree White color is the most noticeable in forest twilight. Rowan Lily of the Valley contents
The fourth wave of flowering The fourth wave of flowering includes plants blooming in summer. In June, common chickweed, spreading boron, forest chickweed, and 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
Ash fruits Some of the plants of the first tier are pollinated by the wind and the fruits are distributed 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, mammals. The fruits of these plants are juicy, bright, and easily visible to birds. Many of the plants have fruits with small outgrowths - tasty morsels for the ants, who distribute them. Buckthorn fruits May lily of the valley
Dependence of seed distribution on tiers Tier I II Distribution Number of plants (in%) seed dispersal Wind 83 83 Ants III, IV Birds 50 Birds 16 Rodents 13
Over the course of a year, oak grove plants produce 10 t/ha of net growth (including root growth). The forest creates its own microclimate: humidity, shade, protection from the wind. That is why many animals live here. Typically, certain animal species are associated with plant layers. Let's look at typical oak forest animals. table of contents
Animals associated with the first tier Silkworm Black Woodpecker Jay This tier is inhabited by birds: chaffinch, song thrush, blue tit, pika. Lots of insects: leaf beetles, bark beetles, longhorned beetles. Nuthatch
Animals associated with the second tier Redstart Oriole Flycatcher This tier contains many insects, mainly beetles. Squirrel Woodpecker contents
Animals confined to the third tier Warblers Robins Warblers This tier is home to many insects and mollusks. Spiders
Animals confined to the fourth tier Roe deer Elk Wolf Snake Dormouse Frog Fox In this tier there are bees, wasps, bumblebees, mountain hare, ants, butterflies and other insects, some species of birds nesting on the ground. There are many mouse-like rodents, among them the forest mouse and the yellow-throated mouse.
Fallen leaves protect the soil from freezing and rapid evaporation of moisture. Many insects and other animals overwinter on the forest floor. Animals that form detrital food chains feed on the forest floor. Bacteria, fungi, protozoa, mites, worms, insects or their larvae contribute to the decomposition of litter. The bulk of animals are distributed to a depth of 50 cm. Under 1 square. m of soil are inhabited by up to 20,000,000 protozoa, nematode worms number up to 50,000. table of contents
Reasons for the stability of the oak forest The oak forest is home to a huge number of species of plants, animals, fungi, and microorganisms (according to estimates, more than 10,000 species without microorganisms). Species in the oak forest are connected in a food chain. Food chains are intertwined into a very complex food web. The extinction of a species does not usually disrupt the entire system. Self-regulation is well developed in the oak forest. The entire diverse population of the forest exists together, without completely destroying each other, but only limiting the number of individuals of each species. The circulation of substances and the movement of energy are clearly visible in the oak grove. Dubrava – 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 release the energy stored in them for the life of organisms. Ultimately, mineralization of substances by decomposers occurs. table of contents
Cycle of substances in an oak forest Energy from the sun Trees, shrubs, herbaceous green plants Rodents (squirrel, wood mouse) Snakes Granivorous birds (finch, chaffinch, hazel grouse) Birds of prey (hawks, owls) Herbivorous insects (butterfly caterpillars, bark beetles, longhorned beetles, leaf beetles Insectivorous birds (warblers, cuckoos, flycatchers) Amphibians (grass 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, beetles) gravediggers, soil protozoa, fungi) ( Inorganic substances(mineral salts, etc.)
conclusions Vadim Shefner You, man, loving nature, at least sometimes feel sorry for it. On pleasure trips, do not trample its fields. In the bustle of the century at the station, you are in a hurry to appreciate it. She is your long-time, kind healer, She is an ally of the soul. Don’t burn it recklessly and don’t exhaust it to the bottom. And remember the simple truth - There are many of us, but she is one. The adaptability of living organisms to life together- the result of long evolution. Any species occupies a certain place in the biogeocenosis. The existence of other species depends on it. Preserving all species means preserving stable biogeocenoses, means preserving 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 times of oak grove plants? 3. How do the methods of seed dispersal depend on the layer? 4. What role do mushrooms play in the 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 grove? Written assignments 1. Complete the table. Tier Environmental group plants Examples of animals 2. Write down two food chains in an oak forest. 3. List the adaptations of plants to living together in an oak forest. 4. Why is an oak forest a stable 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) grade. - M., Bustard. 2004. A. V. Kulev General biology 10th grade. Lesson planning. - Saint Petersburg. Parity. 2001. General biology. Textbook for grades 9-10. Ed. Yu. I. Polyansky. - M., Enlightenment. 1987. O. V. Petunin Biology lessons in 11th grade. - Yaroslavl. Development Academy. Academy Holding. 2003. Lessons in general biology. Ed. V. M. Korsunskaya. - M., Enlightenment. 1977. Photos by Anastasia Yushkova, N. B. Perlina.
In Figures 198, 200-202, get acquainted with groups of organisms living together in biocenoses. What connections exist between them?
Various types of established relationships between organisms in biocenoses contribute to the preservation of their species composition and the maintenance of the optimal number of species populations that make up the biocenosis.
The structure of a biocenosis is expressed in the species composition of its population and the quantitative ratio of organisms by species (species structure), in the regular distribution of organisms of different species relative to each other in the occupied space (spatial structure), in food (trophic) and other relationships between organisms.
Species structure of the biocenosis. Any biocenosis is formed by its characteristic species of organisms with a certain number of each of them. The total number of species in one biocenosis can reach several tens of thousands. Coral reefs and tropical forests are especially rich in species of organisms (Fig. 197, 1, 2). Biocenoses that have developed in harsh living conditions for organisms, for example in the Arctic, are characterized by a much smaller number of species (Fig. 197, 3).
Rice. 197. Biocenoses rich and poor in species: 1 - coral reef; 2 - a tropical forest; 3 - polar tundra
The number of organisms of each species in the biocenosis is different. Species with the greatest numbers, or dominant (dominant), constitute its “species core”. In some spruce forests, for example, in spruce oxalis forests, spruce dominates among trees, among herbaceous plants - wood sorrel, among birds - wren, robin, chaffinch, and among mammals - bank and red-gray voles (Fig. 198).
Rice. 198. Numerous species of organisms in the spruce forest: 1 - common spruce; 2 - common wood sorrel; 3 - finch; 4 - red-gray vole
The number of small species in biocenoses is always greater than numerous ones. Small species create the species richness of biocenoses and increase the diversity of its connections. These same species serve as a reserve for replacing dominant species when environmental conditions change. The richer the species composition of a biocenosis, the better its stability in relation to changing environmental conditions is ensured.
Spatial structure of the biocenosis. The distribution of organisms in terrestrial biocenoses is mainly related to the layering, or vertical arrangement of vegetation.
The tiered, or vertical, composition of biocenoses is most clearly expressed in forests, where there can be up to 5-6 tiers of plants (Fig. 199). Thus, in broad-leaved forests, or oak groves, oak, linden and other tall deciduous trees with large leaves form the first (upper) tier. Less light-loving trees, for example, Norway maple, elm and other oak companion trees, are the second tier. Hazel (hazel), honeysuckle, euonymus, rose hips, viburnum, buckthorn and other shrubs - the third tier (undergrowth). Perennial herbaceous plants (corydalis, anemone, goose onion, lungwort, May lily of the valley, green green grass, European hooffoot, raven's eye) form the fourth tier. Mosses, lichens and mushrooms grow in the lower (fifth) layer of broad-leaved forest and are rare, not forming a continuous cover.
Rice. 199. Tiered distribution of plants in the biocenosis of a broad-leaved forest - oak grove
The layered structure of the forest allows plants to use sunlight more efficiently: light-loving plants form the upper tier, and plants of other tiers have adapted to life in low-light conditions or develop and bloom in early spring before the leaves bloom on the trees (blues, anemones, corydalis, goose onions).
The vertical distribution of animals and other organisms is associated with the tiers of biocenoses (Fig. 200). Thus, in the crowns of trees of the first and second tiers of the forest live various leaf-eating insects, insectivorous birds (thrushes, orioles, cuckoos), and small animals (squirrels, dormice). There are also predator birds, such as a sparrowhawk. The population of animals in the lower layer of the forest is especially diverse. Moose, hares, wild boars, hedgehogs, wood mice, wolves, foxes and other animals live here.
Rice. 200. Tiered distribution of animals in the biocenosis of a mixed forest
Many animals, due to their mobility, live in several tiers. For example, the common squirrel builds nests and feeds its young in trees, and collects its food both in trees, bushes, and on the ground. Black grouse, wood grouse, and hazel grouse feed mainly in the lower tier of the forest, spend the night in trees, and breed their offspring on the ground.
The distribution of animals into tiers in the biocenosis reduces competition between them in feeding and choosing places to build nests. Thus, the pied flycatcher hunts insects in the crowns of trees, and the garden redstart hunts in bushes and above the soil. Great spotted woodpeckers and nuthatch feed on insects and their larvae, usually in the middle layer of the forest. However, they do not compete with each other: the woodpecker gets insects, their larvae and pupae from under the bark of trees, and the nuthatch collects insects from the surface of the bark.
Tiering, like floors, is also observed in the location of the roots. The roots of trees in the upper tiers go deepest into the soil. In each tier of soil there are bacteria and fungi, thanks to which the transformation of organic residues into humus (humus) and its mineralization occur. Many insects, ticks, worms and other animals live here permanently or temporarily. The number of species and individuals of animals associated with soil exceeds the number of land animals. Soil populations are most numerous in places where the soil is rich in organic matter and have a major influence on soil formation.
Food (trophic) structure of biocenosis. All organisms of biocenoses are interconnected by the “food-consumer” relationship and each of them is included in one or another link of the food chain - a sequential series of organisms that feed on each other. There are two main types of food chains: grazing (grazing chains) and detrital (decomposition chains).
The basis of pasture food chains is made up of plants (autotrophic organisms) and animals (heterotrophic organisms). Herbivorous animals, such as locusts, leaf beetles, crossbills, waxwings, voles, hares, deer, are first-order consumers; carnivores (frogs, toads, lizards, snakes, insectivorous birds, many birds of prey and animals) are second-order consumers; and predatory animals feeding on second-order consumers are third-order consumers (Fig. 201).
Rice. 201. Pasture food chain of oak forest
In detrital food chains (from the Latin detritus - worn out, small organic particles), the source of food for first-order consumer organisms is the remains of decomposed animals, plants, fungi, along with the bacteria they contain. Detrital food chains are most common in forests (Fig. 202). Thus, a significant part of plant production (leaf litter) is not consumed directly by herbivorous animals, but dies and undergoes decomposition and mineralization by saprotrophs (from the Greek sapros - rotten) - rotting bacteria. Earthworms, millipedes, mites, and insect larvae that feed on detritus serve as food for consumers of the next link.
Rice. 202. Detritus food chain of deciduous forest
So, the species, spatial and food (trophic) structures of the biocenosis form the basis for maintaining its integrity. The species composition of organisms is formed in accordance with the environmental conditions in which a particular natural community exists. The species that make up the biocenosis, distributed among tiers and connected to each other by food chains, ensure the long-term existence of a variety of natural communities on our planet.
Exercises based on the material covered
- What is the structure of the biocenosis expressed in?
- How does the species structure of a biocenosis differ from the spatial and food (trophic) structure?
- What types of organisms in the biocenosis are considered dominant?
- What is the role of small species in the biocenosis?
- What is the reason for the vertical distribution of organisms in biocenoses?
- What are food chains? How do grassland food chains differ from detritus food chains?
Compose several pasture and detrital food chains from the listed organisms and their metabolic products: herbaceous plants, leaves of trees and shrubs, plant litter, earthworms, butterfly caterpillars, slugs, blowfly larvae, frogs, grass snakes, dead crows, tits, hawks, hedgehogs .
The life of forest plants has its own characteristics. The trees that form a 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 importance (spruce, pine, oak). The second tier is formed by trees of the second size (bird cherry, rowan, apple tree). The third tier consists of shrubs, for example, rose hips, hazel, viburnum, and euonymus. The fourth tier is herbaceous cover, and the fifth is mosses and lichens. Access of light to plants of different tiers is not the same. The crowns of the trees of the first tier are better illuminated. From the upper to the lower tiers, the illumination decreases, since the plants of the upper tiers retain their share sun rays. Mosses and lichens occupying the fifth tier receive very little light. These are the most shade-tolerant plants in the forest.
Different forests have different quantity tiers. For example, in a dark spruce forest, only two or three tiers are visible. The first tier contains the main trees (spruces), the second contains a small number of herbaceous plants, and the third is formed by mosses. Other wood and shrubby plants do not grow in the second tier of spruce forests, as they do not tolerate strong shading. Also, grass cover is not observed in the spruce forest.
The tiered arrangement is characteristic not only of the above-ground parts of plants, but also of their underground organs - roots. Tall trees have roots that penetrate deep into the ground, whereas root system trees of the second tier are shorter and form 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 layers soil.
Trees of the first size (oak, pine, spruce) close their crowns and form a forest canopy, under which a small proportion of sunlight penetrates. Therefore, herbaceous plants of the forest, as a rule, are shade-tolerant and have wide leaf blades. Many of them cannot withstand exposure to direct sunlight and may die in open space. A feature of broad-leaved forest grasses is that they bloom in early spring, when there is no foliage on the trees. With the help of wide leaves, forest plants accumulate organic substances in low light and deposit them in underground organs, for example, lungwort - in rhizomes. In the gloomy spruce thickets, the flowers of herbaceous plants have corollas white so that they are visible to pollinating insects from afar. For example, such flowers are found in lily of the valley, wintergreen, sedmichnik, snyti, and mynika flowers. But despite these adaptations, the flowers of forest grasses are often not pollinated and do not form seeds. Therefore, the propagation of many herbaceous plants is carried out by dividing the rhizomes, for example, wood sorrel, lily of the valley, kupena, sedmichnik, and mynika. This explains the placement of these herbs in groups in the forest.
The forest litter covering the soil consists of fallen leaves or needles, respectively, in deciduous or coniferous forests, as well as from the bark and branches of trees, dead areas of grass, and mosses. Loose forest litter is moist, which is favorable for the development of mold and cap mushrooms. Myceliums of various mushrooms densely penetrate the litter, gradually transforming organic matter into humus and mineral salts to feed the green plants of the forest.