Organisms living in the soil. Underground animals - who live underground
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.
All around us: on the ground, in the grass, in the trees, in the air - life is in full swing everywhere. Even a resident of a big city who has never gone deep into the forest often sees birds, dragonflies, butterflies, flies, spiders and many other animals around him. The inhabitants of reservoirs are also well known to everyone. Everyone, at least occasionally, has seen schools of fish near the shore, water beetles or snails.
But there is a world hidden from us, inaccessible to direct observation - a peculiar world of soil animals.
There is eternal darkness there; you cannot penetrate there without destroying the natural structure of the soil. And only isolated, accidentally noticed signs show that beneath the surface of the soil among the roots of plants there is a rich and diverse world of animals. This is sometimes evidenced by mounds above mole holes, holes in gopher holes in the steppe or sand swallow holes in a cliff above the river, piles of earth on the path thrown out by earthworms, and the earthworms themselves crawling out after the rain, as well as masses unexpectedly appearing literally from underground winged ants or fat larvae of cockchafers that are caught when digging up the ground.
Soil is usually the surface layer of the earth's crust on land, formed during the weathering of bedrock under the influence of water, wind, temperature fluctuations and the activity of plants, animals and humans. The most important property of soil, which distinguishes it from infertile parent rock, is fertility, i.e., the ability to produce a crop of plants.
As a habitat for animals, soil is very different from water and air. Try waving your hand in the air - you will notice almost no resistance. Do the same in water - you will feel significant resistance from the environment. And if you put your hand in a hole and cover it with earth, it will be difficult to pull it back out. It is clear that animals can move relatively quickly in the soil only in natural voids, cracks or previously dug passages. If there is nothing of this in the way, then the animal can advance only by breaking through a passage and raking the earth back or swallowing the earth and passing it through the intestines. The speed of movement will, of course, be insignificant.
Every animal needs to breathe to live. The conditions for breathing in soil are different than in water or air. Soil consists of solid particles, water and air. Solid particles in the form of small lumps occupy slightly more than half of its volume; the rest falls on the gaps - pores, which can be filled with air (in dry soil) or water (in soil saturated with moisture). As a rule, water covers all soil particles with a thin film; the rest of the space between them is occupied by air saturated with water vapor.
Thanks to this structure of the soil, numerous animals live in it and breathe through their skin. If you take them out of the ground, they quickly die from drying out. Moreover, hundreds of species of real freshwater animals live in the soil, inhabiting rivers, ponds and swamps. True, these are all microscopic creatures - lower worms and single-celled protozoa. They move and float in a film of water covering soil particles. If the soil dries out, these animals secrete a protective shell and seem to fall asleep.
Soil air receives oxygen from the atmosphere: its amount in the soil is 1-2% less than in atmospheric air. Oxygen is consumed in the soil by animals, microorganisms, and plant roots. They all emit carbon dioxide. There is 10-15 times more of it in soil air than in the atmosphere. Free gas exchange between soil and atmospheric air occurs only if the pores between solid particles are not completely filled with water. After heavy rains or in the spring, after the snow melts, the soil is saturated with water. There is not enough air in the soil, and under the threat of death, many animals leave it. This explains the appearance of earthworms on the surface after heavy rains.
Among soil animals there are also predators and those that feed on parts of living plants, mainly roots. There are also consumers of decomposing plant and animal residues in the soil - perhaps bacteria also play a significant role in their nutrition.
Soil animals find their food either in the soil itself or on its surface.
The life activity of many of them is very useful. The activity of earthworms is especially useful. They drag a huge amount of plant debris into their burrows, which contributes to the formation of humus and returns substances extracted from it by plant roots to the soil.
In forest soils, invertebrates, especially earthworms, process more than half of all leaf litter. Over the course of a year, on each hectare, they throw out to the surface up to 25-30 tons of land they have processed, turned into good, structural soil. If you distribute this soil evenly over the entire surface of a hectare, you will get a layer of 0.5-0.8 cm. Therefore, it is not for nothing that earthworms are considered the most important soil builders. Not only earthworms “work” in the soil, but also their closest relatives - smaller whitish annelids (enchytraeids, or pot worms), as well as some types of microscopic roundworms (nematodes), small mites, various insects, especially their larvae, and finally woodlice, millipedes and even snails.
Medvedka
The purely mechanical work of many animals living in it also affects the soil. They make passages, mix and loosen the soil, and dig holes. All this increases the number of voids in the soil and facilitates the penetration of air and water into its depth.
This “work” involves not only relatively small invertebrate animals, but also many mammals - moles, shrews, marmots, gophers, jerboas, field and forest mice, hamsters, voles, and mole rats. The relatively large passages of some of these animals go deep from 1 to 4 m.
The passages of large earthworms go even deeper: in most of them they reach 1.5-2 m, and in one southern worm even 8 m. These passages, especially in denser soils, are constantly used by plant roots penetrating into the depths. In some places, for example in the steppe zone, a large number of passages and holes are dug in the soil by dung beetles, mole crickets, crickets, tarantula spiders, ants, and in the tropics - termites.
Many soil animals feed on roots, tubers, and plant bulbs. Those that attack cultivated plants or forest plantations are considered pests, for example the cockchafer. Its larva lives in the soil for about four years and pupates there. In the first year of life, it feeds mainly on the roots of herbaceous plants. But, as it grows, the larva begins to feed on the roots of trees, especially young pines, and causes great harm to the forest or forest plantations.
Mole paws are well adapted for life in the soil.
The larvae of click beetles, darkling beetles, weevils, pollen eaters, caterpillars of some butterflies, such as cutworms, the larvae of many flies, cicadas and, finally, root aphids, such as phylloxera, also feed on the roots of various plants, greatly harming them.
A large number of insects that damage the above-ground parts of plants - stems, leaves, flowers, fruits, lay eggs in the soil; Here, the larvae that emerge from the eggs hide during drought, overwinter, and pupate. Soil pests include some species of mites and centipedes, naked slugs and extremely numerous microscopic roundworms - nematodes. Nematodes penetrate from the soil into the roots of plants and disrupt their normal functioning. There are many predators living in the soil. “Peaceful” moles and shrews eat huge amounts of earthworms, snails and insect larvae; they even attack frogs, lizards and mice. These animals eat almost continuously. For example, a shrew eats an amount of living creatures per day equal to its own weight!
There are predators among almost all groups of invertebrates living in the soil. Large ciliates feed not only on bacteria, but also on protozoa, such as flagellates. The ciliates themselves serve as prey for some roundworms. Predatory mites attack other mites and small insects. Thin, long, pale-colored geophilic centipedes that live in soil cracks, as well as larger dark-colored drupes and centipedes that stay under stones and in stumps, are also predators. They feed on insects and their larvae, worms and other small animals. Predators include spiders and related haymakers (“mow-mow-leg”). Many of them live on the soil surface, in the litter, or under objects lying on the ground.
Antlion larva.
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.
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 leave layers where unfavorable conditions arise. 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), sarsazan (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.
How animal habitat soil very different from water and air. The soil is a loose thin surface layer of land in contact with the air. Despite its insignificant thickness, this shell of the Earth plays a vital role in the spread of life. The soil is not just a solid body, like most rocks of the lithosphere, but a complex three-phase system in which solid particles are surrounded by air and water. It is permeated with cavities filled with a mixture of gases and aqueous solutions, and therefore extremely diverse conditions develop in it, favorable for the life of many micro- and macroorganisms. In the soil, temperature fluctuations are smoothed out compared to the surface layer of air, and the presence of groundwater and the penetration of precipitation create moisture reserves and provide a humidity regime intermediate between the aquatic and terrestrial environments. The soil concentrates reserves of organic and mineral substances supplied by dying vegetation and animal corpses. All this determines greater saturation of the soil with life.
Every animal needs to live need to breathe. The conditions for breathing in soil are different than in water or air. Soil consists of solid particles, water and air. Solid particles in the form of small lumps occupy slightly more than half the volume of the soil; the rest of the volume accounts for the gaps - pores, which can be filled with air (in dry soil) or water (in soil saturated with moisture).
Moisture in the soil present in various states:
- bound (hygroscopic and film) is firmly held by the surface of soil particles;
- capillary occupies small pores and can move along them in different directions;
- gravitational fills larger voids and slowly seeps down under the influence of gravity;
- vaporous is contained in the soil air.
Compound soil air changeable. With depth, the oxygen content in it decreases greatly and the concentration of carbon dioxide increases. Due to the presence of decomposing organic substances in the soil, the soil air may contain a high concentration of toxic gases such as ammonia, hydrogen sulfide, methane, etc. When the soil is flooded or intensive rotting of plant residues, completely anaerobic conditions may occur in some places.
Temperature fluctuations cutting only on the soil surface. Here they can be even stronger than in the surface layer of air. However, with every centimeter deeper, daily and seasonal temperature changes become less and less and at a depth of 1-1.5 m they are practically no longer traceable.
All these features lead to the fact that, despite the great heterogeneity of environmental conditions in the soil, it acts as fairly stable environment, especially for mobile organisms. It is clear that animals can move relatively quickly in the soil only in natural voids, cracks or previously dug passages. If there is nothing of this in the way, then the animal can advance only by breaking through a passage and raking the earth back or swallowing the earth and passing it through the intestines.
Inhabitants of the soil. 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. Thanks to this soil structure, numerous species live in it. animals that breathe through their skin. Moreover, hundreds of species of real plants live in the soil. freshwater animals, inhabiting rivers, ponds and swamps. True, these are all microscopic creatures - lower worms and single-celled protozoa. They move and float in a film of water covering soil particles. If the soil dries out, these animals secrete a protective shell and, as it were, fall asleep, falling into a state of suspended animation.
Among soil animals there are also predators and those that feed on parts of living plants, mainly roots. There are also consumers of decomposing plant and animal residues in the soil; Perhaps bacteria also play a significant role in their nutrition. “Peaceful” moles eat huge amounts of earthworms, snails and insect larvae; they even attack frogs, lizards and mice. There are predators among almost all groups of invertebrates living in the soil. Large ciliates feed not only on bacteria, but also on protozoa, such as flagellates. Predators include spiders and related harvestmen
Soil animals find their food either in the soil itself or on its surface. The life activity of many of them is very useful. Earthworms are especially useful. They drag a huge amount of plant debris into their burrows, which contributes to the formation of humus and returns substances extracted from it by plant roots to the soil.
Not only earthworms “work” in the soil, but also their closest relatives:
- whitish annelids (enchytraeids, or pot worms),
- some types of microscopic roundworms (nematodes),
- small mites,
- various insects,
- woodlice,
- centipedes,
- snails
The purely mechanical work of many animals living in it also affects the soil. They make passages, mix and loosen the soil, and dig holes. These are moles, marmots, gophers, jerboas, field and forest mice, hamsters, voles, and mole rats. The relatively large passages of some of these animals go 1-4 m deep. In some places, for example in the steppe zone, a large number of passages and holes are dug in the soil by dung beetles, mole crickets, crickets, tarantulas, ants, and in the tropics - termites.
In addition to the permanent inhabitants of the soil, among large animals one can distinguish a large ecological group of 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.
In the process of evolution, the inhabitants of the soil developed adaptation to appropriate living conditions:
- features of the shape and structure of the body,
- physiological processes,
- reproduction and development,
- ability to endure unfavorable conditions and behavior.
Earthworms, nematodes, most millipedes, and the larvae of many beetles and flies have a highly elongated flexible body that allows them to easily move through winding narrow passages and cracks in the soil. Bristles in earthworms and other annelids, hairs and claws in arthropods allow them to significantly accelerate their movements in the soil and stay firmly in burrows, clinging to the walls of passages. How slowly a worm crawls across the surface of the earth and at what speed, essentially instantly, it hides in its hole. When making new passages, some soil animals, such as worms, alternately extend and contract their bodies. In this case, cavity fluid is periodically pumped into the front end of the animal. It swells strongly and pushes away soil particles. Other animals, such as moles, clear their way by digging the ground with their front paws, which have turned into special digging organs.
The color of animals that constantly live in the soil is usually pale - grayish, yellowish, whitish. Their eyes, as a rule, are poorly developed or completely absent. But the organs of smell and touch have developed very subtly.