Biogeocenosis Is a homogeneous area the 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 are predominant in number or occupy large area... They are called species - dominants. However, not all dominant species have the same effect on the biogeocenosis. Those that determine the composition, structure and properties of an ecosystem by creating an environment for the entire community are called edifiers... Now let's consider the biogeocenosis of the oak forest.
Among terrestrial biogeocenoses, one of the most difficult is broadleaf forest, for example, oak grove. Dubrava - perfect and stable ecological system capable of unchanged external conditions exist for centuries. The biogeocenosis of oak forests is made up of more than a hundred species of plants and several thousand species of animals.
Plants of oak groves. In terrestrial biogeocenoses, the main biological products are created by higher plants... In the forest, these are mainly perennial tree species.
There is intense competition between plants for basic living conditions: space, light, water with minerals dissolved in it. As a result of the long natural selection oak forest plants have developed adaptations that allow different types coexist. This is clearly manifested in the layering characteristic of the oak forest.
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 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 that form it.
Due to the complex multi-tiered total area leaves of plants 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 groves. The richness and diversity of plants is the reason for the development in oak forests of consumers from the animal world, from the simplest to the highest 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 animals 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 was never large and did not play 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 pollinator function in biogeocenosis, participate in the destruction of litter and serve as the basis for the existence of many subsequent links in the food chain.
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Biology. General biology... Grade 11. Basic level Sivoglazov Vladislav Ivanovich
24. The structure of ecosystems
24. The structure of ecosystems
Remember!
What levels of wildlife organization do you know?
What is an ecosystem?
Influence abiotic factors on living organisms and interactions between separate types are at the heart of the life of any community. Community, or biocenosis, Is a collection of coexisting populations of different species. Together with the factors of inanimate nature (abiotic factors), the community forms ecosystem.
An ecosystem is a very broad concept. Rain a tropical forest and a swamp, a rotting stump and an anthill, a puddle in the middle of a country road and lonely standing tree with its inhabitants are different natural ecosystems. There are artificial ecosystems such as farmland, aquarium, farm. Ecosystem, the boundaries of which are defined plant community, for example oak grove, meadow, spruce forest, Birch Grove are called biogeocenosis. The whole set of biogeocenoses the globe forms a global ecosystem, or biosphere.
Any ecosystem has a spatial, species and ecological structure.
Spatial structure of the ecosystem... The spatial structure of most biogeocenoses and, consequently, ecosystems is determined by the layered arrangement of vegetation (Fig. 75). For example, in a typical deciduous forest it is possible to distinguish the sloping (arboreal), shrub, herbaceous and above-ground (ground) layers. Going deeper into the soil, you can also find certain "floors" that are formed by the roots of certain plants and where different types of underground animals live. Such a spatial organization of the ecosystem allows plants to effectively use sunlight and soil resources, and numerous animals and microorganisms coexist together, occupying a variety of ecological niches.
Rice. 75. An example of the layering of an ecosystem. Tiered structure deciduous forest
As part of any ecosystem, two main ones can be distinguished structural components: a complex of factors of inanimate nature, the so-called abiotic environment, or biotope, and the totality of all living organisms - biocenosis. In turn, the biocenosis can be subdivided into zoocenosis(animal community), phytocenosis(plant community), microbocenosis(community of microorganisms). A biotope is also a heterogeneous system, it consists of a variety of abiotic factors, which together form certain climatic, geographical, soil and other parameters of the ecosystem.
Species structure ecosystems. The biocenosis of any ecosystem is characterized by a certain species diversity, that is, the number of species that form it, and the quantitative ratio of individuals of these species. Species diversity ensures the stability of ecosystems. The high number of populations that make up the ecosystem indicates that these species are optimally adapted to specific conditions and are important for the stable existence of this ecosystem. Usually, it is rather difficult to calculate the total number of individuals in populations, therefore, when characterizing ecosystems, the concept is used "Population density"(§ 6).
The ecological structure of the ecosystem. Despite the enormous diversity of ecosystems, they all have approximately the same ecological structure. The ecological structure is the ratio of groups of species that occupy certain ecological niches and perform certain functions in the community. The presence of these groups is a prerequisite for the stable existence of any ecosystem, because thanks to their interaction, the main property of ecosystems is ensured - the ability to self-sustain. These indispensable components of any ecosystem are producers, consumers and decomposers.
Producers, or manufacturers, - these are autotrophs, which in the process of vital activity synthesize from not organic matter organic compounds using as a carbon source carbon dioxide... The biomass formed in the ecosystem by autotrophic organisms is called primary products. It serves as food and energy source 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 products of the ecosystem. Each large ecosystem or any biogeocenosis has its own specific plants that carry out photosynthesis, i.e., their producers.
Consumptions, or consumers, Are heterotrophic organisms that use biomass synthesized by producers for their own life. By eating and processing plants, consumers receive energy and form secondary products ecosystems.
Consumables are a wide variety of living organisms - from microscopic bacteria to large mammals, from protozoa to humans. In terms of the structure of the ecosystem and the role that different consumers play in maintaining it equilibrium state, all consumers can be divided into several subgroups, which we will do a little later, when we analyze food ties ecosystems.
Reducers, or decomposers, recycle dead organic matter ( detritus) to mineral compounds, which can again be used by producers. Many organisms, such as, for example, earthworms, centipedes, termites, ants, etc., feed on plant and animal debris, and part of the wood rots and decomposes during the life of fungi and bacteria. When fungi and other decomposers die off, 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 reducers (fig. 76).
Oak forest ecosystem. Consider, as an example, an oak grove, a very resilient terrestrial ecosystem (Figure 77). Dubrava is typical broadleaf forest a tiered 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. Required Ecosystem Components
Shrub vegetation is formed under the canopy of two tiers. Hazel, euonymus, viburnum, hawthorn, blackthorn, elderberry, buckthorn - this is far from complete list 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, tree shoots and various grasses. Moreover, during the year in the oak forest there is a change in the herbaceous 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, 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 a green biomass of the oak forest. Oak groves are very productive: within a year, on an area of 1 hectare, they create up to 10 tons of an increase in plant mass.
Dead roots and fallen leaves form a litter in which numerous reducers: earthworms, larvae of flies and butterflies, dung beetles and dead-eating beetles, woodlice and millipedes, springtails, ticks, nematodes. While feeding, these organisms not only transform detritus, but also form the soil structure. The activity of such diggers as moles, mice and some large invertebrates prevents the soil from caking. Numerous soil protozoa live in water droplets between soil particles, and fungi form a symbiosis with plant roots and participate in the decomposition of detritus.
Rice. 77. Oak grove ecosystem
Despite the fact that every year 3-4 tons of dead plants are supplied to 1 hectare of soil surface in the 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 great amount: several hundred individuals per 1 m 2.
The fauna of the upper tiers of the oak forest is diverse. Dozens of bird species nest in the tree crowns. Magpies and jackdaws, songbird and chaffinch, great tit and blue tit are building nests. Eagle owl and tawny owl hatch chicks in hollows. Hobby and Sparrowhawk scare small songbirds. The bushes are inhabited by the robin and the blackbird, the pied flycatcher and the nuthatch. Even lower are the nests of the warbler and wren. The gray squirrel moves along all the tiers in search of food. Butterflies, bees, wasps, flies, mosquitoes, beetles - more than 1600 species of insects are closely related to the oak! Grasshoppers and beetles, spiders and haymakers, mice, shrews and hedgehogs share a place under the sun in the grass layer. The largest consumers of this ecosystem are roe deer, fallow deer and wild boars.
The sustainability of this and any other ecosystem ensures a complex system the relationship of all 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 essential components of any ecosystem?
4. In what relations are the inhabitants of biocenoses with each other? Describe these connections.
5. Describe species composition and the spatial structure of the oak forest ecosystem.
Think! Execute!
1. Name common features biogeocenoses of deciduous forest and freshwater reservoir.
2. Is it possible for the existence of a biocenosis consisting only of plants? Substantiate your point of view.
3. Conduct research on "My home as an example of an ecosystem."
4. Design an excursion route to demonstrate the species, spatial and ecological structures of a typical ecosystem in your region (group project).
Work with computer
Talk to electronic application... Study the material and complete the assignments.
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Among terrestrial biogeocenoses, one of the most complex is a broad-leaved forest, for example, an oak grove. Dubrava - a perfect and stable ecological system, capable of existing for centuries under unchanged external conditions. The biogeocenosis of oak forests is made up of more than a hundred species of plants and several thousand species of animals.
Plants of oak groves
In terrestrial biogeocenoses, the main biological products are created by higher plants. In the forest, these are mainly perennial tree species (Figure 39).
Figure 39. Biogeocenosis of deciduous forest.Feature deciduous forest lies in species diversity vegetation. There is intense competition between plants for 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 coexist. This is clearly manifested in the layering characteristic of the oak forest.
The upper tier is formed by the most light-loving tree species: oak, ash, linden. Below there are 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 that form it.
Tiering is also expressed in the location of root systems. Trees in the upper tiers have the deepest root systems and can use water and minerals from the deeper layers of the soil.
Dubrava is characterized by high biological productivity. Due to its complex layering, the total area of leaves of plants growing on each hectare reaches 4-6 hectares. Such a powerful photosynthesizing apparatus captures and transforms about 1% of the annual inflow into potential energy of organic matter. solar radiation... The latter in 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 groves.
The richness and diversity of plants that produce an enormous 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.
The food chains in the forest are intertwined in a very complex food web, so the loss of any one species of animals usually does not significantly disrupt the entire system. Meaning different groups animals in the biogeocenosis are 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 number, and therefore, biomass, was never large and did not play 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 pollinator function in biogeocenosis, participate in the destruction of litter and serve as the basis for the existence of many subsequent links in the food chain.
Self-regulation in the 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, not completely destroying each other, but only limiting the number of individuals of each species to a certain level. How great is the importance of such regulation of the number 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 general activity does not cause significant damage to the tree and forest. Meanwhile, all insects are highly fertile. The number of eggs laid by one female is rarely less than 100. Many species are capable of giving 2-3 generations per summer. Therefore, in the absence of limiting factors, the number of any species of insects would increase very quickly and would lead to the destruction of the ecological system.
Mineralization of organic residues.
Great value In the life of the forest, there are processes of decomposition and mineralization of the mass of dying leaves, wood, animal remains and products of their vital activity. Of the total annual increase in the biomass of aboveground parts of plants, about 3-4 tons per hectare naturally dies and falls off, forming the so-called forest litter. Dead underground parts of plants also make up a significant mass. Returns to the soil with litter most of minerals and nitrogen consumed by plants.
Animal remains are very quickly destroyed by dead-eating beetles, skin-eating beetles, larvae of carrion flies and other insects, as well as putrefactive bacteria. Fiber and other durable substances that make up a significant part of plant litter are more difficult to decompose. 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 up by the destroyers. A significant part of the biomass is made up of earthworms, which do a huge job of decomposing and moving organic matter in the soil. Total number individuals of insects, mites, worms and other invertebrates reaches many tens and even hundreds of millions per hectare. In the decomposition of litter, the role of bacteria and lower, saprophytic fungi is especially great.
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