The inhabitants of the soil are called. Soil inhabitants
T.V. Lukarevskaya
When we enter the forest on a summer day, we immediately notice fluttering butterflies, singing birds, jumping frogs, we rejoice at a running hedgehog, at meeting a hare. One gets the impression that it is these clearly visible animals that form the basis of our fauna. In fact, the animals that are easy to see in the forest are only a tiny part of it.
The basis of the population of our forests, meadows, and fields are soil animals. The soil, at first glance so lifeless and unsightly, turns out upon closer examination to be literally crammed with life. If you look closely, extraordinary pictures will be revealed.
Some soil inhabitants are easy to see. These are earthworms, centipedes, insect larvae, small mites, and wingless insects. Others can be viewed using a microscope. In the thin films of water that envelop the soil particles, rotifers and flagellates scurry about, amoebas crawl, and roundworms wriggle. How many real workers are here, invisible to the naked eye, but nevertheless doing titanic work! All these invisible creatures keep our common home – the Earth – clean. Moreover, they also warn about the danger that threatens this house when people behave unreasonably in relation to nature.
In the soil of central Russia, per 1 m2 you can find up to 1 thousand species of soil inhabitants, greatly varying in number: up to 1 million mites and springtails, hundreds of centipedes, insect larvae, earthworms, about 50 million roundworms, but the number of protozoa is even difficult to estimate .
This whole world, living according to its own laws, ensures the processing of dead plant residues, cleaning the soil from them, and maintaining a water-resistant structure. Soil animals constantly plow the soil, moving particles from the lower layers upward.
In all terrestrial ecosystems, the vast majority of invertebrates (both in number of species and number of individuals) are soil dwellers or are closely associated with the soil at some point in their life cycle. According to calculations by Boucle (1923), the number of insect species associated with soil is 95–98%.
In terms of ability to adapt to living conditions, there are no animals equal to nematodes. In this respect, they can only be compared with bacteria and protozoan single-celled organisms. This universal adaptability is largely explained by the development of a dense outer cuticle in nematodes, which increases their vitality. In addition, the body shape and movement patterns of nematodes have been shown to be suitable for life in various environments.
Nematodes take part in the mechanical destruction of plant tissue: they “drill” into dead tissue and, with the help of secreted enzymes, destroy cell walls, opening paths for bacteria and fungi to enter.
In our country, harvest losses of vegetables, grains and industrial crops due to damage by roundworms sometimes reach 70%.
Nematode
Southern root-knot nematode | Beet nematode |
The formation of tumors - galls - on the roots of the host plant is caused by another pest - the southern root-knot nematode (Meloidogyne incognita). It causes the greatest harm to vegetable growing in the southern regions, where it is found in open ground. In the north, it is found only in greenhouses, damaging mainly cucumbers and tomatoes. The main damage is caused by females, while males, having completed development, go out into the soil and do not feed.
Soil nematodes have a bad reputation: they are seen primarily as pests of cultivated plants. Nematodes destroy the roots of potatoes, onions, rice, cotton, sugar cane, sugar beets, ornamental and other plants. Zoologists are developing measures to combat them in fields and greenhouses. A great contribution to the study of this group of animals was made by the famous evolutionary biologist A.A. Paramonov.
Nematodes have long attracted the attention of evolutionists. They are not only extremely diverse, but also amazingly resistant to physical and chemical factors. Wherever they begin to study these worms, new species unknown to science are discovered everywhere. In this regard, nematodes seriously claim second place in the animal world, after insects: experts believe that there are at least 500 thousand species, but there is reason to believe that the true number of nematode species is much higher.
Our planet is formed by four main shells: atmosphere, hydrosphere, biosphere and lithosphere. All of them are in close interaction with each other, since representatives of the biosphere - animals, plants, microorganisms - cannot exist without such formative substances as water and oxygen.
Just like the lithosphere, the soil cover and other deep-lying layers cannot exist in isolation. Although we cannot see it with the naked eye, the soil is very densely populated. What kind of living creatures does not live in it! Like any living organisms, they also need water and air.
What animals live in the soil? How do they influence its formation and how do they adapt to such an environment? We will try to answer these and other questions in this article.
What types of soils are there?
Soil is only the uppermost, very shallow layer that makes up the lithosphere. Its depth goes to about 1-1.5 m. Then a completely different layer begins, in which groundwater flows.
That is, the top fertile layer of soil is the very habitat of living organisms and plants of various shapes, sizes and methods of nutrition. The soil, as a habitat for animals, is very rich and diverse.
This structural part of the lithosphere is not the same. The formation of the soil layer depends on many factors, mainly environmental conditions. Therefore, the types of soil (fertile layer) also differ:
- Podzolic and sod-podzolic.
- Chernozem.
- Turf.
- Swamp.
- Podzolic-marsh.
- Solody.
- Floodplain.
- Salt marshes.
- Gray forest-steppe.
- Solonetz.
This classification is given only for the area of Russia. In other countries, continents, and parts of the world, there are other types of soils (sandy, clayey, arctic-tundra, humus, and so on).
Also, all soils are not the same in chemical composition, moisture supply and air saturation. These indicators vary and depend on a number of conditions (for example, this is influenced by animals in the soil, which will be discussed below).
and who helps them with this?
Soils date back to the appearance of life on our planet. It was with the formation of living systems that the slow, continuous and self-renewing formation of soil substrates began.
Based on this, it is clear that living organisms play a certain role in soil formation. Which one? Basically, this role comes down to processing organic substances contained in the soil and enriching it with mineral elements. It also loosens and improves aeration. M.V. Lomonosov wrote very well about this in 1763. It was he who first stated that the soil is formed due to the death of living beings.
In addition to the activities carried out by animals in the soil and plants on its surface, rocks are a very important factor in the formation of the fertile layer. The type of soil will generally depend on their variety.
- light;
- humidity;
- temperature.
As a result, rocks are processed under the influence of abiotic factors, and microorganisms living in the soil decompose animal and plant remains, turning them into mineral ones. As a result, a certain type of fertile soil layer is formed. At the same time, animals living underground (for example, worms, nematodes, moles) provide its aeration, that is, oxygen saturation. This is achieved by loosening and constantly recycling soil particles.
Animals and plants together produce Microorganisms, protozoa, unicellular fungi and algae, this substance is processed and converted into the desired form of mineral elements. Worms, nematodes and other animals again pass soil particles through themselves, thereby forming organic fertilizer - vermicompost.
Hence the conclusion: soils are formed from rocks as a result of a long historical period of time under the influence of abiotic factors and with the help provided by the animals and plants living in them.
The invisible world of soil
A huge role not only in the formation of the soil, but also in the life of all other living beings is played by the smallest creatures, forming an entire invisible soil world. Who belongs to them?
Firstly, unicellular algae and fungi. Among the fungi, one can distinguish the divisions of chytridiomycetes, deuteromycetes and some representatives of zygomycetes. Of the algae, phytoedaphones, which are green and blue-green algae, should be noted. The total mass of these creatures per 1 hectare of soil cover is approximately 3100 kg.
Secondly, these are numerous and such animals in the soil as protozoa. The total mass of these living systems per 1 hectare of soil is approximately 3100 kg. The main role of single-celled organisms is to process and decompose organic residues of plant and animal origin.
The most common of these organisms include:
- rotifers;
- mites;
- amoeba;
- centipedes symphylos;
- protury;
- springtails;
- double tails;
- blue-green algae;
- green unicellular algae.
What animals live in the soil?
Soil inhabitants include the following invertebrate animals:
- Small crustaceans (crustaceans) - about 40 kg/ha
- Insects and their larvae - 1000 kg/ha
- Nematodes and roundworms - 550 kg/ha
- Snails and slugs - 40 kg/ha
Such soil-dwelling animals are very important. Their importance is determined by their ability to pass soil lumps through themselves and saturate them with organic substances, forming vermicompost. Their role is also to loosen the soil, improve oxygen saturation and create voids that are filled with air and water, resulting in increased fertility and quality of the top layer of soil.
Let's look at what animals live in the soil. They can be divided into two types:
- permanent residents;
- temporary residents.
The permanent vertebrate mammalian inhabitants representing the fauna of the soil include mole rats, mole rats, zokors and their importance comes down to maintenance as they feed on soil insects, snails, mollusks, slugs and so on. And the second meaning is digging long and winding passages, allowing the soil to be moistened and enriched with oxygen.
Temporary inhabitants representing the fauna of the soil use it only for short-term shelter, as a rule, as a place for laying and storing larvae. Such animals include:
- jerboas;
- gophers;
- badgers;
- beetles;
- cockroaches;
- other types of rodents.
Adaptations of soil inhabitants
In order to live in such a difficult environment as soil, animals must have a number of special adaptations. Indeed, according to its physical characteristics, this medium is dense, hard and low-oxygen. In addition, there is absolutely no light in it, although there is a moderate amount of water. Naturally, you need to be able to adapt to such conditions.
Therefore, animals that live in the soil have acquired the following features over time (during evolutionary processes):
- extremely small sizes to fill the tiny spaces between soil particles and feel comfortable there (bacteria, protozoa, microorganisms, rotifers, crustaceans);
- flexible body and very strong muscles - advantages for movement in the soil (ringed and roundworms);
- the ability to absorb oxygen dissolved in water or breathe over the entire surface of the body (bacteria, nematodes);
- life cycle consisting of a larval stage, during which neither light, moisture, nor nutrition is required (larvae of insects, various beetles);
- larger animals have adaptations in the form of powerful burrowing limbs with strong claws, which make it easy to dig through long and winding passages underground (moles, shrews, badgers, and so on);
- Mammals have a well-developed sense of smell, but practically no vision (moles, zokora, mole rats, mole rats);
- the body is streamlined, dense, compressed, with short, hard, close-fitting fur.
All these devices create such comfortable conditions that animals in the soil feel no worse than those living in the ground-air environment, and perhaps even better.
The role of ecological groups of soil inhabitants in nature
The main ecological groups of soil inhabitants are considered to be:
- Geobionts. Representatives of this group are animals for which soil is a permanent habitat. Their entire life cycle takes place in it, in combination with the basic processes of life. Examples: multi-tailed, tailless, double-tailed, tailless.
- Geophiles. This group includes animals for which soil is an obligatory substrate during one of the phases of their life cycle. For example: insect pupae, locusts, many beetles, weevil mosquitoes.
- Geoxenes. An ecological group of animals for which the soil is a temporary shelter, a refuge, a place for laying and breeding offspring. Examples: many beetles, insects, all burrowing animals.
The totality of all animals of each group is an important link in the overall food chain. In addition, their vital activity determines the quality of soils, their self-renewal and fertility. Therefore, their role is extremely important, especially in the modern world, in which agriculture forces soils to become poor, leached and salted out under the influence of chemical fertilizers, pesticides and herbicides. Animal soils contribute to a faster and more natural restoration of the fertile layer after severe mechanical and chemical attacks from humans.
The connection between plants, animals and soils
Not only animal soils are interconnected, forming a common biocenosis with its own food chains and ecological niches. In fact, all existing plants, animals and microorganisms are involved in a single circle of life. Just like all of them are connected with all habitats. Let's give a simple example to illustrate this relationship.
The grasses of meadows and fields provide food for terrestrial animals. These, in turn, serve as a source of food for predators. The remains of grass and organic matter, which are excreted with the waste products of all animals, end up in the soil. Here microorganisms and insects, which are detritivores, get to work. They decompose all residues and convert them into minerals that are convenient for absorption by plants. Thus, plants receive the components they need for growth and development.
In the soil itself, microorganisms and insects, rotifers, beetles, larvae, worms, and so on become food for each other, and therefore a common part of the entire food network.
Thus, it turns out that animals living in the soil and plants living on its surface have common points of intersection and interact with each other, forming a single general harmony and force of nature.
Poor soils and their inhabitants
Soils that have been repeatedly exposed to human influence are called poor. Construction, cultivation of agricultural plants, drainage, land reclamation - all this leads to soil depletion over time. What inhabitants can survive in such conditions? Unfortunately, not many. The hardiest underground inhabitants are bacteria, some protozoa, insects, and their larvae. Mammals, worms, nematodes, locusts, spiders, and crustaceans cannot survive in such soils, so they die or leave them.
Poor soils also include soils that have a low content of organic and mineral substances. For example, quick sand. This is a special environment in which certain organisms live with their own adaptations. Or, for example, saline and highly acidic soils also contain only specific inhabitants.
Studying soil animals at school
The school zoology course does not provide for the study of soil animals in a separate lesson. Most often, this is just a brief overview in the context of a topic.
However, in primary school there is such a subject as “The World Around You”. Animals in the soil are studied in great detail as part of the program of this subject. Information is presented according to the age of the children. Kids are told about the diversity, role in nature and human economic activity that animals play in the soil. 3rd grade is the most suitable age for this. Children are already educated enough to learn some terminology, and at the same time they have a great thirst for knowledge, for understanding everything around them, studying nature and its inhabitants.
The main thing is to make the lessons interesting, non-standard, and also informative, and then children will absorb knowledge like sponges, including about the inhabitants of the soil environment.
Examples of animals living in soil environments
You can give a short list reflecting the main soil inhabitants. Naturally, it won’t be possible to make it complete, because there are so many of them! However, we will try to name the main representatives.
Soil animals - list:
- rotifers, mites, bacteria, protozoa, crustaceans;
- spiders, locusts, insects, beetles, millipedes, wood lice, slugs, snails;
- nematodes and other roundworms;
- moles, mole rats, mole rats, zokors;
- jerboas, gophers, badgers, mice, chipmunks.
Many animals and insects live under the surface of the earth, we present to your attention the rating of the Top 10 creatures that live underground
A small burrowing rodent of the mole rat family. It is distinguished by a unique social structure for mammals, cold-bloodedness, insensitivity to acids, insensitivity to pain, and tolerance to CO2 concentrations. It is the longest-living of rodents, up to 28 years. Look at him - he's terrible.
2.
The largest representative of the mole rat subfamily: its body length is 25-35 cm, weight reaches 1 kg. The color of the upper body is light, gray-fawn or ocher-brown. Leads a strictly underground, sedentary lifestyle, building multi-tiered systems of passages. It digs the ground mainly with its incisors. Underground feeding passages (11-16 cm in diameter) are laid at a depth of 20-50 cm, often in layers of sand. On the surface of the earth they are indicated by soil emissions in the form of truncated cones 30-50 cm high, weighing 10 kg or more. The total length of the feed tunnels reaches 500 meters. Nesting chambers and storerooms are located at a depth of 0.9 to 3 m. I have come across such a comrade, he has terrible teeth, don’t even try to pick him up, with his teeth he is able to bend the bayonet of a shovel.
class mammals order insectivores. Widely distributed in Eurasia and North America. These are small and medium-sized insectivores: body length from 5 to 21 cm; weight from 9 to 170 g. Moles are adapted to an underground, burrowing lifestyle. Their body is elongated, round, covered with thick, smooth, velvety fur. The mole coat has a unique property - its pile grows straight, and is not oriented in a certain direction. This allows the mole to easily move underground in any direction.
Small rodents whose weight reaches 700 g. Body length 17-25 cm, tail 6-8 cm. Morphological characteristics show a high degree of adaptability to the underground lifestyle. They lead an underground lifestyle, building complex branched systems of passages with nesting chambers, storerooms and latrines. For construction, tuco-tucos prefer loose or sandy soils.
The body length of gophers is from 9 to 35 cm, the tail is from 4 to 14 cm. The weight of some Central American species can reach a kilogram. Gophers spend most of their lives in complex underground passages laid in different soil horizons. The length of such tunnels reaches 100 meters.
Snake of the cylindrical family. It is small in size and has a dense constitution. The body is black in color with two rows of large brown ones. Leads an underground lifestyle, feeding on earthworms.
A fish that spends most of its time in the bottom mule, and when the reservoir dries up, crucian carp burrows into the silt to a depth of 1 to 10 meters and can live in this state for several years.
a large insect, body length (without antennae and cerci) up to 5 centimeters. The abdomen is approximately 3 times larger than the cephalothorax, soft, fusiform, with a diameter in adults of about 1 cm. At the end of the abdomen, paired thread-like appendages are noticeable - cerci, up to 1 cm long. The insect leads a predominantly underground lifestyle, but flies well and runs on the ground and floats. It rarely comes to the surface, mainly at night.
The length of adult individuals (imago) of the eastern species is 25-28 mm, of the western species 26-32 mm. The body is black, with red-brown elytra. In the adult stage (imago), the beetles appear on the surface of the earth at the end of April or May and live for about 5-7 weeks. After approximately 2 weeks, mating occurs, after which the female begins to lay eggs, placing them underground at a depth of 10-20 cm. This process can occur in several stages, and a complete clutch is 60-80 eggs. Having finished laying, the female cockchafer immediately dies.
The body of earthworms is up to 2 m long and consists of many ring-shaped segments 80 - 300. When moving, earthworms rely on short bristles located on each segment except the front one. The number of bristles varies from 8 to several dozen. Earthworms live on all continents except Antarctica, but only some species originally had a wide geographic range, the rest were introduced by humans.
4.3.2. Soil inhabitants
The heterogeneity of the soil leads to the fact that for organisms of different sizes it acts as a different environment. For microorganisms, the huge total surface of soil particles is of particular importance, since the overwhelming majority of the microbial population is adsorbed on them. The complexity of the soil environment creates a wide variety of conditions for a wide variety of functional groups: aerobes and anaerobes, consumers of organic and mineral compounds. The distribution of microorganisms in the soil is characterized by fine focality, since even within a few millimeters different ecological zones can change.
For small soil animals (Fig. 52, 53), which are combined under the name microfauna (protozoa, rotifers, tardigrades, nematodes, etc.), soil is a system of micro-reservoirs. Essentially, these are aquatic organisms. They live in soil pores filled with gravitational or capillary water, and part of life can, like microorganisms, be in an adsorbed state on the surface of particles in thin layers of film moisture. Many of these species also live in ordinary bodies of water. However, soil forms are much smaller than freshwater ones and, in addition, are distinguished by their ability to remain in an encysted state for a long time, waiting out unfavorable periods. While freshwater amoebas are 50-100 microns in size, soil amoebas are only 10-15. Representatives of flagellates are especially small, often only 2–5 microns. Soil ciliates also have dwarf sizes and, moreover, can greatly change their body shape.
Rice. 52. Testate amoebas feeding on bacteria on decaying leaves of the forest floor
Rice. 53. Soil microfauna (according to W. Dunger, 1974):
1–4 – flagella; 5–8 – naked amoebas; 9-10 – testate amoebas; 11–13 – ciliates; 14–16 – roundworms; 17–18 – rotifers; 19–20 – tardigrades
To slightly larger air-breathing animals, the soil appears as a system of small caves. Such animals are grouped under the name mesofauna (Fig. 54). The sizes of soil mesofauna representatives range from tenths to 2–3 mm. This group includes mainly arthropods: numerous groups of mites, primary wingless insects (collembolas, proturus, two-tailed insects), small species of winged insects, symphila centipedes, etc. They do not have special adaptations for digging. They crawl along the walls of soil cavities using their limbs or wriggling like a worm. Soil air saturated with water vapor allows breathing through the covers. Many species do not have a tracheal system. Such animals are very sensitive to drying out. The main means of escape from fluctuations in air humidity is to move deeper. But the possibility of deep migration through soil cavities is limited by a rapid decrease in pore diameter, so movement through soil holes is accessible only to the smallest species. Larger representatives of the mesofauna have some adaptations that allow them to tolerate a temporary decrease in soil air humidity: protective scales on the body, partial impermeability of the integument, a solid thick-walled shell with an epicuticle in combination with a primitive tracheal system that ensures respiration.
Rice. 54. Soil mesofauna (no W. Danger, 1974):
1 – false scorion; 2 – gama new bell-bottom; 3–4 oribatid mites; 5 – centipede pauroioda; 6 – chironomid mosquito larva; 7 - beetle from this family. Ptiliidae; 8–9 springtails
Representatives of the mesofauna survive periods of soil flooding in air bubbles. Air is retained around the body of animals due to their non-wettable integument, which is also equipped with hairs, scales, etc. The air bubble serves as a kind of “physical gill” for a small animal. Respiration is carried out due to oxygen diffusing into the air layer from the surrounding water.
Representatives of micro- and mesofauna are able to tolerate winter freezing of the soil, since most species cannot move down from layers exposed to negative temperatures.
Larger soil animals, with body sizes from 2 to 20 mm, are called representatives macrofauna (Fig. 55). These are insect larvae, centipedes, enchytraeids, earthworms, etc. For them, the soil is a dense medium that provides significant mechanical resistance when moving. These relatively large forms move in the soil either by expanding natural wells by pushing apart soil particles, or by digging new tunnels. Both methods of movement leave an imprint on the external structure of animals.
Rice. 55. Soil macrofauna (no W. Danger, 1974):
1 - earthworm; 2 – woodlice; 3 – centipede; 4 – two-legged centipede; 5 – ground beetle larva; 6 – click beetle larva; 7 – mole cricket; 8 - Khrushchev larva
The ability to move through thin holes, almost without resorting to digging, is inherent only in species that have a body with a small cross-section, capable of bending strongly in winding passages (centipedes - drupes and geophiles). Moving apart soil particles due to the pressure of the body walls, earthworms, larvae of long-legged mosquitoes, etc. move. Having fixed the rear end, they thin and lengthen the front, penetrating into narrow soil crevices, then secure the front part of the body and increase its diameter. In this case, in the expanded area, due to the work of the muscles, a strong hydraulic pressure of the non-compressible intracavitary fluid is created: in worms - the contents of the coelomic sacs, and in tipulids - the hemolymph. Pressure is transmitted through the body walls to the soil, and thus the animal expands the well. At the same time, the rear passage remains open, which threatens to increase evaporation and persecution of predators. Many species have developed adaptations to an ecologically more advantageous type of movement in the soil - digging and blocking the passage behind them. Digging is carried out by loosening and raking away soil particles. The larvae of various insects use for this the anterior end of the head, mandibles and forelimbs, expanded and strengthened by a thick layer of chitin, spines and outgrowths. At the rear end of the body, devices for strong fixation develop - retractable supports, teeth, hooks. To close the passage on the last segments, a number of species have a special depressed platform framed by chitinous sides or teeth, a kind of wheelbarrow. Similar areas are formed on the back of the elytra and in bark beetles, which also use them to clog the passages with drill flour. Closing the passage behind them, the animals that inhabit the soil are constantly in a closed chamber, saturated with the vapors of their own bodies.
Gas exchange of most species of this ecological group is carried out with the help of specialized respiratory organs, but at the same time it is supplemented by gas exchange through the integument. It is even possible that exclusively cutaneous respiration is possible, for example in earthworms and enchytraeids.
Burrowing animals can move away from layers where an unfavorable environment occurs. During drought and winter, they concentrate in deeper layers, usually several tens of centimeters from the surface.
Megafauna soils are large shrews, mainly mammals. A number of species spend their entire lives in the soil (mole rats, mole rats, zokora, Eurasian moles, golden moles
Africa, marsupial moles of Australia, etc.). They create entire systems of passages and burrows in the soil. The appearance and anatomical features of these animals reflect their adaptability to a burrowing underground lifestyle. They have underdeveloped eyes, a compact, ridged body with a short neck, short thick fur, strong digging limbs with strong claws. Mole rats and mole rats loosen the ground with their incisors. Soil megafauna also includes large oligochaetes, especially representatives of the family Megascolecidae, living in the tropics and the Southern Hemisphere. The largest of them, the Australian Megascolides australis, reaches a length of 2.5 and even 3 m.
In addition to the permanent inhabitants of the soil, a large ecological group can be distinguished among large animals burrow inhabitants (gophers, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but reproduce, hibernate, rest, and escape danger in the soil. A number of other animals use their burrows, finding in them a favorable microclimate and shelter from enemies. Burrowers have structural features characteristic of terrestrial animals, but have a number of adaptations associated with the burrowing lifestyle. For example, badgers have long claws and strong muscles on the forelimbs, a narrow head, and small ears. Compared to hares that do not dig holes, rabbits have noticeably shortened ears and hind legs, a more durable skull, more developed bones and muscles of the forearms, etc.
For a number of ecological features, soil is a medium intermediate between aquatic and terrestrial. The soil is similar to the aquatic environment due to its temperature regime, low oxygen content in the soil air, its saturation with water vapor and the presence of water in other forms, the presence of salts and organic substances in soil solutions, and the ability to move in three dimensions.
The soil is brought closer to the air environment by the presence of soil air, the threat of drying out in the upper horizons, and rather sharp changes in the temperature regime of the surface layers.
The intermediate ecological properties of soil as a habitat for animals suggest that soil played a special role in the evolution of the animal world. For many groups, in particular arthropods, soil served as a medium through which initially aquatic inhabitants were able to transition to a terrestrial lifestyle and conquer land. This path of arthropod evolution was proven by the works of M. S. Gilyarov (1912–1985).
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From the author's bookSoils and biogeocenosis We observe the closest interaction and complete community of the organic world and the inorganic world.V. V. Dokuchaev Complete community of the organic and inorganic world Dokuchaev’s definition of soil as a natural body formed
From the author's bookChernozem, humus and soil fertility The rye is ripening under the hot cornfield, And from cornfield to cornfield the whimsical wind drives away the golden shimmers of A. A. Fet Rye is ripening under a hot cornfield Junior editor of the statistical department of the Ministry of State Property V. I. Chaslavsky in 1875 accepted
From the author's bookThe dust of centuries on the surface of the soil And earth fell from the sky onto the blinded fields. Yu. Kuznetsov Earth fell from the sky onto the blinded fields. The air contains a lot of dust - solid particles, fragments of minerals, salts - several hundredths of a millimeter in size. It is estimated that
Ecological groups of soil organisms. The number of organisms in the soil is enormous (Fig. 5.41).
Rice. 5.41. Soil organisms (no E. A. Kriksunov et al., 1995)
Plants, animals and microorganisms living in the soil are in constant interaction with each other and with their environment. These relationships are complex and diverse. Animals and bacteria consume plant carbohydrates, fats and proteins. Thanks to these relationships and as a result of fundamental changes in the physical, chemical and biochemical properties of rock, soil-forming processes constantly occur in nature. On average, the soil contains 2 - 3 kg/m2 of living plants and animals, or 20 - 30 t/ha. Moreover, in a temperate climate zone, plant roots account for 15 tons (per 1 ha), insects - 1 t, earthworms - 500 kg, nematodes - 50 kg, crustaceans - 40 kg, snails, slugs - 20 kg, snakes, rodents - 20 kg, bacteria - 3t, mushrooms - 3t, actinomycetes - 1.5 t, protozoa - 100 kg, algae - 100 kg.
Despite the heterogeneity of environmental conditions in the soil, it acts as a fairly stable environment, especially for mobile organisms. A large gradient of temperature and humidity in the soil profile allows soil animals to provide themselves with a suitable ecological environment through minor movements.
The heterogeneity of the soil leads to the fact that for organisms of different sizes it acts as a different environment. For microorganisms, the huge total surface of soil particles is of particular importance, because the overwhelming majority of microorganisms are adsorbed on them. The complexity of the soil environment creates great diversity for a wide variety of functional groups: aerobes, anaerobes, consumers of organic and mineral compounds. The distribution of microorganisms in the soil is characterized by fine focality, since different ecological zones can change over the course of several millimeters.
Based on the degree of connection with the soil as a habitat, animals are divided into three ecological groups: geobionts, geophiles and geoxenes.
Geobionts - animals that constantly live in the soil. The entire cycle of their development takes place in the soil environment. These are such as earthworms (Lymbricidae), many primary wingless insects (Apterydota).
Geophiles - animals, part of the development cycle of which (usually one of the phases) necessarily takes place in the soil. Most insects belong to this group: locusts (Acridoidea), a number of beetles (Staphylinidae, Carabidae, Elateridae), long-legged mosquitoes (Tipulidae). Their larvae develop in the soil. As adults, these are typical terrestrial inhabitants. Geophiles also include insects that are in the pupal phase in the soil.
Geoxenes - animals that sometimes visit soil for temporary shelter or shelter. Insect geoxenes include cockroaches (Blattodea), many hemiptera (Hemiptera), and some beetles that develop outside the soil. This also includes rodents and other mammals that live in burrows.
At the same time, the above classification does not reflect the role of animals in soil-forming processes, since in each group there are organisms that actively move and feed in the soil and passive ones that remain in the soil during certain phases of development (insect larvae, pupae or eggs). Soil inhabitants, depending on their size and degree of mobility, can be divided into several groups.
Microbiotype, microbiota - These are soil microorganisms that make up the main link in the detrital food chain and represent, as it were, an intermediate link between plant residues and soil animals. These include primarily green (Chlorophyta) and blue-green (Cyanophyta) algae, bacteria (Bacteria), fungi (Fungi) and protozoa (Protozoa). Essentially, we can say that these are aquatic organisms, and the soil for them is a system of micro-reservoirs. They live in soil pores filled with gravitational or capillary water, like microorganisms; part of their life can be in an adsorbed state on the surface of particles in thin layers of film moisture. Many of them also live in ordinary bodies of water. At the same time, soil forms are usually smaller than freshwater ones and are distinguished by their ability to remain in an encysted state for a significant time, waiting out unfavorable periods. Thus, freshwater amoebas have sizes of 50-100 microns, soil ones - 10-15 microns. Flagellates do not exceed 2-5 microns. Soil ciliates are also small in size and can significantly change their body shape.
For this group of animals, the soil appears as a system of small caves. They do not have special adaptations for digging. They crawl along the walls of soil cavities using their limbs or wriggling like a worm. Soil air saturated with water vapor allows them to breathe through the integument of the body. Often species of animals in this group do not have a tracheal system and are very sensitive to desiccation. Their means of escape from fluctuations in air humidity is to move deeper. Larger animals have some adaptations that allow them to tolerate a decrease in soil air humidity for some time: protective scales on the body, partial impermeability of the integument, etc.
Animals usually experience periods of soil flooding with water in air bubbles. Air is retained around their body due to the non-wetting of the integument, which in most of them is equipped with hairs, scales, etc. The air bubble plays a unique role for the animal as a “physical gill.” Breathing is carried out due to oxygen diffusing into the air layer from the environment. Animals of meso- and microbiotypes are able to tolerate winter freezing of the soil, which is especially important, since most of them cannot move down from layers exposed to negative temperatures.
Macrobiotype, macrobiota - These are large soil animals: with body sizes from 2 to 20 mm. This group includes insect larvae, centipedes, enchytraeids, earthworms, etc. The soil for them is a dense medium that provides significant mechanical resistance when moving. They move in the soil, expanding natural wells by moving apart soil particles, digging new passages. Both methods of movement leave an imprint on the external structure of animals. Many species have developed adaptations to an ecologically more advantageous type of movement in the soil - digging and blocking the passage behind them. Gas exchange of most species of this group is carried out with the help of specialized respiratory organs, but at the same time it is supplemented by gas exchange through the integument. In earthworms and enchytraeids, exclusively cutaneous respiration is noted. Burrowing animals can move away from layers where an unfavorable environment occurs. By winter and during drought, they concentrate in deeper layers, mostly a few tens of centimeters from the surface.
Megabiotype, megabiota - these are large shrews, mainly mammals (Fig. 5.42).
Rice. 5.42. Burrowing activity of burrowing animals in the steppe
Many of them spend their entire lives in the soil (golden moles in Africa, moles in Eurasia, marsupial moles in Australia, mole rats, mole moles, moles, etc.). They create entire systems of passages and burrows in the soil. Adaptation to a burrowing underground lifestyle is reflected in the appearance and anatomical features of these animals: underdeveloped eyes, a compact ridged body with a short neck, short thick fur, strong compact limbs with strong claws.
In addition to the permanent inhabitants of the soil, among the group of animals they are often classified as a separate ecological group burrow inhabitants This group of animals includes badgers, marmots, gophers, jerboas, etc. They feed on the surface, but reproduce, hibernate, rest, and escape from danger in the soil. A number of other animals use their burrows, finding in them a favorable microclimate and shelter from enemies. The inhabitants of burrows, or burrowers, have structural features characteristic of terrestrial animals, but at the same time they have a number of adaptations that indicate a burrowing lifestyle. Thus, badgers are characterized by long claws and strong muscles on the forelimbs, a narrow head, and small ears.
To a special group psammophiles include animals that inhabit loose shifting sands. In vertebrate psammophiles, the limbs are often arranged in the form of a kind of “sand skis”, facilitating movement on loose soil. For example, the thin-toed ground squirrel and the comb-toed jerboa have fingers covered with long hair and horny outgrowths. Birds and mammals of sandy deserts are able to travel long distances in search of water (runners, hazel grouses) or do without it for a long time (camels). A number of animals receive water with food or store it during the rainy season, accumulating it in the bladder, subcutaneous tissues, and abdominal cavity. Other animals hide in holes during drought, bury themselves in the sand, or hibernate during the summer. Many arthropods also live in shifting sands. Typical psammophiles include marbled beetles from the genus Polyphylla, larvae of antlions (Myrmeleonida) and racing horses (Cicindelinae), and a large number of hymenoptera (Hymenoptera). Soil animals that live in shifting sands have specific adaptations that enable them to move in loose soil. As a rule, these are “mining” animals that move sand particles apart. Quick sands are inhabited only by typical psammophiles.
As noted above, 25% of all soils on our planet Earth are saline. Animals that have adapted to life on saline soils are called halophiles. Usually, in saline soils, the fauna is greatly depleted in quantitative and qualitative terms. For example, the larvae of click beetles (Elateridae) and beetles (Melolonthinae) disappear, and at the same time specific halophiles appear that are not found in soils of normal salinity. Among them are the larvae of some desert darkling beetles (Tenebrionidae).
The relationship of plants to soil. We noted earlier that the most important property of the soil is its fertility, which is determined primarily by the content of humus, macro- and microelements, such as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, copper, boron, zinc, molybdenum etc. Each of these elements plays its own role in the structure and metabolism of the plant and cannot be completely replaced by another. Plants are distinguished: distributed mainly on fertile soils - eutrophic or eutrophic; content with a small amount of nutrients - oligotrophic. Between them there is an intermediate group mesotrophic species.
Different types of plants have different attitudes towards the content of available nitrogen in the soil. Plants that are especially demanding of high nitrogen content in the soil are called nitrophils(Fig. 5.43).
Rice. 5.43. Plants that live in nitrogen-rich soils
They usually settle where there are additional sources of organic waste, and therefore nitrogen nutrition. These are clearing plants (raspberry - Rubusidaeus, climbing hop - Humuluslupulus), garbage, or species that are companions of human habitation (nettle - Urticadioica, amaranthus - Amaranthus retroflexus, etc.). Nitrophils include many umbelliferae that settle on the edges of forests. Nitrophils settle en masse where the soil is constantly enriched with nitrogen and through animal excrement. For example, on pastures, in places where manure accumulates, nitrophilic grasses (nettle, acorn grass, etc.) grow in patches.
Calcium - The most important element is not only among those necessary for the mineral nutrition of plants, but is also an important component of the soil. Plants in carbonate soils containing more than 3% carbonates and effervescent from the surface are called calcium-sulfides(lady's slipper - Cypripedium calceolus). Among the trees are Siberian larch - Larixsibiria, beech, ash. Plants that avoid soils rich in lime are called calciumphobes. These are sphagnum mosses and bog heathers. Tree species include warty birch and chestnut.
Plants react differently to soil acidity. Thus, with different environmental reactions in soil horizons, it can cause uneven development of the root system in clover (Fig. 5.44).
Rice. 5.44. Development of clover roots in soil horizons at
different environmental reactions
Plants that prefer acidic soils, with a low pH value, i.e. 3.5-4.5, called acidophiles(heather, white grass, small sorrel, etc.), plants of alkaline soils with a pH of 7.0-7.5 (coltsfoot, field mustard, etc.) are classified as Basiphilam(basophils), and plants in soils with a neutral reaction - neutrophils(meadow foxtail, meadow fescue, etc.).
Excess salts in the soil solution have a negative effect on plants. Numerous experiments have established a particularly strong effect on plants from chloride salinization of the soil, while sulfate salinization is less harmful. The lower toxicity of sulfate soil salinization is, in particular, due to the fact that, unlike the Cl ion, the SO - 4 ion in small quantities is necessary for normal mineral nutrition of plants, and only its excess is harmful. Plants that have adapted to growing in soils with high salt content are called halophytes. Unlike halophytes, plants that do not grow on saline soils are called glycophytes. Halophytes have high osmotic pressure, which allows them to use soil solutions, since the sucking force of the roots exceeds the sucking force of the soil solution. Some halophytes secrete excess salts through their leaves or accumulate them in their bodies. Therefore, they are sometimes used to produce soda and potash. Typical halophytes are European saltwort (Salicomiaherbaceae), sarcassum (Halocnemumstrobilaceum), etc.
A special group is represented by plants adapted to loose moving sands - psammophytes. Plants of shifting sands in all climatic zones have common features of morphology and biology; they have historically developed unique adaptations. Thus, tree and shrub psammophytes, when covered with sand, form adventitious roots. Adventitious buds and shoots develop on the roots if the plants are exposed when sand is blown out (white saxaul, kandym, sand acacia and other typical desert plants). Some psammophytes are saved from sand drift by rapid growth of shoots, reduction of leaves, and often increased volatility and springiness of fruits. The fruits move along with the moving sand and are not covered by it. Psammophytes easily tolerate drought thanks to various adaptations: sheaths on the roots, suberization of roots, strong development of lateral roots. Most psammophytes are leafless or have distinct xeromorphic foliage. This significantly reduces the transpiration surface.
Flowing sands are also found in humid climates, for example, sand dunes along the shores of the northern seas, sands of a drying river bed along the banks of large rivers, etc. Typical psammophytes grow here, such as sandy hair, sandy fescue, and willow-shelyuga.
Plants such as coltsfoot, horsetail, and field mint live on moist, predominantly clay soils.
The ecological conditions for plants growing on peat (peat bogs) are extremely unique - a special type of soil substrate formed as a result of incomplete decomposition of plant residues under conditions of high humidity and difficult air access. Plants that grow in peat bogs are called oxylophytes. This term refers to the ability of plants to tolerate high acidity with strong moisture and anaerobiosis. Oxylophytes include wild rosemary (Ledumpalustre), sundew (Droserarotundifolia), etc.
Plants that live on stones, cliffs, scree, in whose life the physical properties of the substrate play a predominant role, belong to lithophytes. This group includes, first of all, the first settlers after microorganisms on rocky surfaces and collapsing rocks: autotrophic algae (Nostos, Chlorella, etc.), then crustose lichens, tightly growing to the substrate and painting rocks in different colors (black, yellow, red and etc.), and finally, leaf lichens. By releasing metabolic products, they contribute to the destruction of rocks and thereby play a significant role in the long process of soil formation. Over time, organic residues accumulate in the form of a layer on the surface and especially in the cracks of stones, on which mosses settle. Under the moss cover, a primitive layer of soil is formed, on which lithophytes from higher plants settle. They are called crevice plants, or Chasmophytes. Among them are species of the genus Saxifraga, shrubs and tree species (juniper, pine, etc.), fig. 5.45.
Rice. 5.45. Rock shape of pine tree growth on granite rocks
on the coast of Lake Ladoga (according to A. A. Nitsenko, 1951)
They have a peculiar growth form (curved, creeping, dwarf, etc.), associated both with harsh water and thermal regimes and with a lack of nutrient substrate on the rocks.
The role of edaphic factors in the distribution of plants and animals. Specific plant associations, as already noted, are formed in connection with the diversity of habitat conditions, including soil conditions, and also in connection with the selectivity of plants in relation to them in a certain landscape-geographical zone. It should be taken into account that even in one zone, depending on its topography, groundwater level, slope exposure and a number of other factors, unequal soil conditions are created, which are reflected in the type of vegetation. Thus, in the feather grass-fescue steppe you can always find areas where feather grass or fescue dominates. The conclusion is that soil types are a powerful factor in plant distribution. Edaphic factors have less influence on terrestrial animals. At the same time, animals are closely related to vegetation, and it plays a decisive role in their distribution. However, even among large vertebrates it is easy to detect forms that are adapted to specific soils. This is especially true for the fauna of clayey soils with a hard surface, loose sand, marshy soils and peat bogs. Burrowing forms of animals are closely related to soil conditions. Some of them are adapted to denser soils, while others can only tear up light sandy soils. Typical soil animals are also adapted to different types of soil. For example, in central Europe, up to 20 genera of beetles are recorded, which are common only on saline or solonetzic soils. And at the same time, soil animals often have very wide ranges and are found in different soils. The earthworm (Eisenianordenskioldi) reaches high numbers in tundra and taiga soils, in the soils of mixed forests and meadows, and even in the mountains. This is due to the fact that in the distribution of soil inhabitants, in addition to the properties of the soil, their evolutionary level and the size of their body are of great importance. The tendency towards cosmopolitanism is clearly expressed in small forms. These are bacteria, fungi, protozoa, microarthropods (mites, springtails), soil nematodes.
In general, in terms of a number of ecological features, soil is an intermediate medium between terrestrial and aquatic. The presence of soil air, the threat of drying out in the upper horizons, and relatively sharp changes in the temperature regime of the surface layers bring the soil closer to the air environment. The soil is similar to the aquatic environment due to its temperature regime, low oxygen content in the soil air, its saturation with water vapor and the presence of water in other forms, the presence of salts and organic substances in soil solutions, and the ability to move in three dimensions. As in water, chemical interdependencies and mutual influence of organisms are highly developed in soil.
The intermediate ecological properties of soil as a habitat for animals make it possible to conclude that soil played a special role in the evolution of the animal world. For example, many groups of arthropods in the process of historical development have gone through a complex path from typically aquatic organisms through soil inhabitants to typically terrestrial forms.