Major biomes of the earth. Aquatic biome: reefs, mangroves, and much more seasonal phenomena

Question 1. How can we explain the differences in flora and fauna of different continents?
Differences in the flora and fauna of the continents are explained by:
1) geological history of the continents;
2) differences in climatic conditions;
3) isolation of continents from each other.

Question 2. What are the reasons for the identification of separate biogeographic regions on Earth?
Biome- a large biosystem consisting of several ecosystems (biogeocenoses) of one natural climatic zone and is characterized by some dominant type of vegetation or other landscape feature.
The following biomes exist on Earth: temperate forests (deciduous forests), steppes, deserts, coniferous forests (taiga), tundra, savannas, tropical rain forests.
The main factor determining the type of biome is climate, since the nature of the environment is created mainly by temperature, amount of precipitation, and the direction and strength of the winds. Taking into account the relatedness of species inhabiting certain territories, the following biogeographic areas are currently distinguished:
1. Holarctic (North America with Greenland, Eurasia without India, Iceland, Korea, Japan and North Africa).
2. Paleotropical (sub-Saharan Africa, Madagascar, India and Indochina).
3. Australian (Australia, New Guinea, New Zealand, Oceania).
4. Neotropical (South and Central America).
5. Antarctic (Antarctica).

Question 3: Describe the major land biomes of various biogeographic regions.
Tundra of the Nearctic and Palaearctic regions: low-growing vegetation - mosses, lichens, sedges, stunted shrubs. The main animals are deer, musk ox, lemming, arctic hare, arctic fox, wolf, white polar bear, white owl.
Coniferous forests of the Nearctic region: mostly dense forests of spruce, fir and other coniferous trees. The main animals are elk, deer, porcupine, vole, shrew, wolverine, lynx, woodpecker, and hazel grouse. Coniferous forests of the Palearctic region: the tree species that make up these forests are pine, fir, spruce. They belong to the same genera as the corresponding Nearctic trees, but are distinct species. The same applies to animals - elk, wolverine, lynx.
Deciduous forests of the Nearctic and Palearctic: broad-leaved forests consist of trees with a dense crown - oak, beech, maple; many colors. The main animals are mole, gopher, black squirrel, raccoon, opossum, chipmunk, red fox, black bear, songbirds.
Nearctic hardwood forests: thickets of juniper and bushes with leathery leaves. fauna representatives come from neighboring biomes. Palaearctic Hardwood Forests: The Mediterranean region is very similar to the corresponding Nearctic biome, supporting animals from a variety of neighboring communities.
Nearctic steppes: various combinations of grass and shrub vegetation. Main animals - bison, antelope, wild rabbit, American badger, fox, koi<5т, степной тетерев, большое количество гремучих змей. Палеарктические степи: травы примерно такие же, как в Неарктике. Типичные животные - сайгак и антилопа; дикие ослы, лошадь и верблюд, а также суслик, хомяк, тушканчик, куница, шакал.
Neotropical steppe (pampa): the vegetation cover is a mixture of various grasses. Fauna - rhea, pampas deer, guinea pig, tuco-tuco, pampas cat, South American fox, skunk, swallow, paired owl.
Rainforest of the eastern region: an abundance of hundreds of plant species forming impenetrable thickets; typical plants are creepers, bamboo, manila hemp, teak, banyan and ebony. Animals: primates are widely represented - gibbons, orangutans, small relatives of monkeys; Also characteristic are the Indian elephant, tapir, two kinds of rhinoceroses, tiger, sloth bear and bamboo bear, deer and antelope. Lots of pheasants, poisonous snakes and lizards.
The tropical forest of the neotropical region is unusually rich in lichens, orchids, and bromeliads. Characteristic are cabbage palm, tropical almonds, bamboo, and vines. Among the animals there are prehensile-tailed monkeys, prehensile-tailed bears, noses, sloths, pygmy deer, opossum mice, parrots, and hummingbirds.
The tropical forest of the Ethiopian region is poorer than other tropical forests. Plants - mahogany, many hews, ferns, orchids and other epiphytes. Notable animals are the pygmy antelope, pygmy hippopotamus, gorilla, chimpanzee, and green monkey.
The Australian rainforest is either a typical continuous-canopy rainforest or a sparse eucalyptus forest. The forests are home to tree kangaroo, koala, opossum, marsupial wolf, Tasmanian devil, platypus, flying dog, and lyrebird.
The Ethiopian savanna is mainly covered with grasses and shrubs, with acacias, baobab, spurge and palm trees. The fauna is represented by herbivores - zebra, eland, oryx, wildebeest, etc. Giraffe, elephant, lion, white and black two-horned rhinoceroses, warthog, cheetah, hyena dog, gopher, golden mole are also typical.
Australian savanna: mainly steppes and thickets of various shrubs and eucalyptus trees. Animals - giant red kangaroo, emu, bandicoot, marsupial rabbit, wombat, parrots.
Palaearctic deserts: scattered bushes of wormwood, finger grass, thickets of camel thorn and tamarisk. The fauna is represented by several species of herbivores, as well as hedgehogs, jerboas, bag rats and hamsters; of birds: eagles, falcons, owls.
Neotropical deserts: rare grasses, low shrubs, cacti, yucca. Among the animals - rhea, armadillo, vulture, fox, tuco-tuco.
Ethiopian deserts: the vegetation consists mainly of grasses and rare shrubs; date palms grow in oases. In the south, spurge and plants with tuberous roots are found. The most common animals are gazelle, porcupine, jerboa, eagle, and lizards.
Australian deserts: vegetation - native forms of quinoa, acacia and various eucalyptus trees. Animals include marsupial mole, kangaroo mouse, jerboa marsupial rat, parakeets.

Question 4. Find the territories mentioned in the paragraph on the geographical map; note their climatic conditions.
1. The Nearctic region includes the territory of all of North America, Newfoundland, and Greenland. In the north, snow and ice give way to tundra. Further south follows an array of coniferous and temperate forests in the east, prairies in the central part and a mixture of mountains, deserts and coniferous forests in the west.
2. The Palearctic region includes all of Eurasia. In the north there is a strip of eternal ice, tundra and coniferous forests. In the temperate zone there are broad-leaved forests, the richest in the Asian part. The central regions of Asia are arid and treeless.
3. The eastern region includes India and Indochina, as well as the islands of Ceylon, Java, Sumatra, Taiwan, Borneo. The islands are completely covered with tropical forests, most of the mainland is mountains with varied vegetation, and in the west of India there are dry steppes.
4. The Neotropical region includes South and Central America, the tropical part of Mexico, and the islands of the Caribbean archipelago. Because this area has been isolated for a long time, its flora and fauna differ sharply from those of other areas.
5. Ethiopian region. It includes almost all of Africa, about. Madagascar and the southern part of the Arabian Peninsula. In the central part1 of Africa there are savannas and steppes, West Africa and the mountainous part of the east are covered with tropical forests.
6. The Australian region includes Australia, New Zealand, New Guinea and the Pacific Islands. The central part of Australia is represented by desert, bordered by steppes, savannas with a rare patch of tropical forest. The islands have varied biomes, from tropical New Guinea to comparatively cold New Zealand.

Patterns of changes in biodiversity in latitudinal and meridional directions, zoning. Biomes.

Each type of living organism has its own optimal values ​​of temperature, humidity, light, etc. The more these conditions deviate from the optimum, the less successfully organisms survive and reproduce. Therefore, in regions with less favorable environmental conditions, fewer species are found.

This principle underlies the zonal distribution of biological diversity on the planet.

Communities characteristic of different zones of the globe are called biomes. There are several definitions of what a biome is.

According to R. Whittaker, the main type of community of any continent, distinguished by the physiognomic characteristics of vegetation, is the biome. Or another definition: biome is a natural zone or area with certain climatic conditions and a corresponding set of dominant plant and animal species that make up a geographical unity.

Biomes can be divided into:

Sushi biomes

Freshwater biomes

Marine biomes

The main environmental conditions that determine the distribution of land biomes are:

temperature(not just the annual average, but the minimum and maximum during the year, which is more important)

precipitation and evaporation rate

presence of seasonal phenomena

For each biome, there are species of organisms characteristic of it. The humid tropics zone is warm and moist all year round, so the richest terrestrial communities (tropical rainforest biome) develop here. If there is seasonality in precipitation, seasonal tropical forests develop, also extremely diverse, but poorer than the previous biome. In conditions of moderate humidity and temperature with pronounced temperature seasonality, a temperate forest biome exists (even less diversity). In the drier parts of the tropical and temperate climate zones, grass communities are found - savannas and steppes. A further decrease in precipitation rates leads to the formation of deserts. At very low temperatures, tundra communities develop.

Rice. 1. Characteristics of terrestrial biomes (Brodsky A.K. Biodiversity)

A – location on the globe, B – climatic conditions, C – species diversity of mammals, amphibians and birds in different biomes

In general, the diversity of organisms decreases from the equator to the poles.

The distribution of soil inhabitants is also subject to latitudinal patterns.

Rice. 2. Zonal distribution of soil fauna

The closer to the poles, the better for small organisms, and the closer to the equator, the more favorable the conditions for macrofauna. In general, the biomass of soil fauna decreases towards the poles, along with it the degree of litter decomposition decreases and the accumulation of organic matter increases.

The uneven distribution of biodiversity across the surface of the globe is associated not only with differences in climate. Specific areas have their own unique conditions. The English ecologist N. Myers identified the so-called “ biodiversity hotspots", requiring special attention and protection measures.

These “points” are selected according to three criteria: 1) a high level of species diversity of vascular plants and vertebrates; 2) a large proportion of endemic species; 3) the presence of a threat of destruction as a result of human activity.

Rice. 3. Map of biodiversity hotspots.

Most hot spots are located on islands and mountainous areas of the tropical zone. Often the hot spot is a vast area extending along the edge of a continent (ecotones?). There are also tectonic faults that lead to the emergence of geysers and hot springs.

Brief description of the main biomes

1.Tundra. The biome occupies the northern part of Eurasia and North America and is located between the polar ice caps in the north and vast tracts of forests in the south. As you move away from the Arctic ice (Greenland, Alaska, Canada, Siberia), there are vast expanses of treeless tundra. Despite the very harsh conditions, there are relatively many plants and animals here. This is especially evident in the summer, when the tundra is covered with a thick carpet of plants and becomes an abode for a large number of insects, migrating birds and animals. The main vegetation is mosses, lichens and grasses, covering the ground during the short growing season. There are low-growing dwarf woody plants. The main representative of the animal world is the reindeer (the North American form is caribou). The mountain hare, vole, arctic fox and lemming also live here.

2.Taiga- biome of boreal (northern) coniferous forests. It stretches for 11 thousand km along the northern latitudes of the globe. Its area is about 11% of the land. Taiga forests grow only in the Northern Hemisphere, since the latitudes of the Southern Hemisphere where they could be located are occupied by the ocean. The conditions of the taiga biome are quite harsh. About 30-40 days a year there is enough warmth and light for normal trees to grow (unlike the tundra, where there are only a few species of dwarf trees). Huge areas are covered with thickets of spruce, pine, fir and larch. Among deciduous trees there is an admixture of alder, birch, and aspen. The number of animals in the taiga is limited by the small number of ecological niches and the severity of winters. The main large herbivores are elk and deer. There are many predators: marten, lynx, wolf, wolverine, mink, sable. Rodents are widely represented - from voles to beavers. There are many birds: woodpeckers, tits, thrushes, finches, etc. Of the amphibians, there are mainly viviparous ones, since it is impossible to warm up a clutch of eggs in a short summer.

3. Temperate Deciduous Forest Biome. In the temperate zone, where there is enough moisture (800-1500 mm per year), and hot summers give way to cold winters, forests of a certain type have developed. Trees that shed their leaves at unfavorable times of the year have adapted to exist in such conditions. Most trees in temperate latitudes are broad-leaved species. These are oak, beech, maple, ash, linden, hornbeam. Mixed with them there are conifers - pine and spruce, hemlock and sequoia. Most forest mammals - badgers, bears, red deer, moles and rodents - lead a terrestrial lifestyle. Wolves, wild cats and foxes are common predators. Lots of birds. The forests of this biome occupy fertile soils, which was the reason for their intensive clearing for agricultural needs. Modern forest vegetation was formed here under the direct influence of man. Probably only forests in Siberia and northern China can be considered untouched.

4. Temperate steppes. The main areas of this biome are represented by Asian steppes and North American prairies. A small part of it is located in the south of South America and Australia. There is not enough rainfall for trees to grow here. but it is enough to prevent the formation of deserts. Almost all steppes are plowed and occupied by grain crops and cultivated pastures. In former times, huge natural herds of herbivorous mammals grazed on the vast expanses of the steppe. Nowadays you can only find domesticated cows, horses, sheep and goats here. Indigenous inhabitants include the North American coyote, the Eurasian jackal, and the hyena dog. All these predators have adapted to the proximity of humans.

5.Mediterranean chaparral. The areas around the Mediterranean Sea are characterized by hot, dry summers and cool, wet winters, so the vegetation here consists mainly of thorny bushes and aromatic herbs. Tough-leaved vegetation with thick and glossy leaves is common. Trees rarely grow to normal size. This biome has a specific name - chaparral. Similar vegetation is characteristic of Mexico, California, South America (Chile) and Australia. Animals in this biome include rabbits, tree rats, chipmunks, some types of deer, sometimes roe deer, lynxes, wild cats and wolves. Lots of lizards and snakes. In Australia, in the chaparral zone, you can find kangaroos, in North America - hares and pumas. Fires play an important role in this biome; shrubs are adapted to periodic fires and recover very quickly after them.

6. Deserts. The desert biome is characteristic of the arid and semi-arid zones of the Earth, where less than 250 mm of precipitation falls annually. The Sahara, as well as the Taklamakan (Central Asia), Atacama (South America), La Jolla (Peru) and Aswan (Libya) deserts, are hot deserts. However, there are deserts, such as the Gobi, where in winter the temperature drops to -20 °C. A typical desert landscape is an abundance of bare rock or sand with sparse vegetation. Desert plants belong mainly to the group of succulents - these are various cacti and milkweeds. Many annuals. In cold deserts, vast areas are occupied by plants belonging to the group of saltworts (species from the goosefoot family). These plants have a long, branched root system with which they can extract water from great depths. Desert animals are small, which helps them hide under stones or in burrows during hot weather. They survive by eating water-storing plants. Of the large animals, we can mention the camel, which can go without water for a long time, but it needs water to survive. But such desert inhabitants as the jerboa and kangaroo rat can exist without water for an indefinitely long time, feeding only on dry seeds.

7. Tropical savannah biome. The biome is located on both sides of the equatorial zone between the tropics. Savannas are found in Central and Eastern Africa, although they are also found in South America and Australia. The typical savannah landscape is tall grass with sparse trees. During the dry season, fires are common, destroying dried grass. The savannas of Africa graze a number of ungulates that are not found in any other biome. The huge number of herbivores contributes to the fact that many predators live in the savanna. The peculiarity of the latter is the high speed of movement. Savannah is an open area. To catch up with the victim, you need to run fast. Therefore, the fastest animal in the land world, the cheetah, lives on the plains of East Africa. Others - lions, hyena dogs - prefer joint actions to catch prey. Still others - hyenas and vultures that feed on carrion - are always ready to grab leftovers or take possession of someone else's just caught prey. The leopard hedges its bets by dragging its prey up a tree.

Biome- this is a natural zone or area with certain climatic conditions. conditions and the corresponding set of dominant (in forest biomes - trees, in the tundra - perennial grasses) species of plants and animals that make up the geographical unity. The term "biome" is used for large combinations of ecosystems. The decisive factor in identifying biomes is the characteristics of the vegetation of a particular region. Moving from the north to the equator, we can distinguish 9 main types of land biomes.

1) Tundra(it begins where the forests end and extends north to the eternal ice. The peculiarity of this biome is low annual precipitation, low temperature, short growing season, sparse vegetation, deer, white hare, few predators (arctic fox).

2) Taiga(northern coniferous forest biome) - spruce, fir, pine, birch, aspen; moose, deer; many predators (wolves, lynxes, wolverines). The development cycle of a predator depends on the development cycle of its prey.

3) Temperate deciduous forests(there is a lot of moisture, hot summers give way to cold winters; oak, beech, maple; wild boar, wolf, bear, woodpecker, blackbird, fertile soils (plowed) - forest vegetation was formed here under human influence.

4) Temperate steppes(a sea of ​​herbaceous vegetation; little precipitation for the existence of plants; the soil of the steppes is rich in humus (organic matter), since by the end of summer the grasses die and quickly decompose; cows, horses, sheep).

5) Mediterranean type vegetation(mild rainy winter, dry summer; trees and shrubs of the eucalyptus genus; fires play an important role (favor the growth of grasses and shrubs, create a natural barrier against the invasion of desert vegetation).

6) Deserts(desert landscape - stones, sand with sparse vegetation, stones, rocks; cacti, milkweed; desert animals survive by eating water-storing plants; jerboa, camel).

7) Tropical savannas and grasslands(two seasons - dry and wet), few trees, tall grass with rare trees from the baobab genera, tree-like spurges; Features of the development of grasses are wind pollination and vegetative growth. Reproduction, resumption of growth despite damage; herds, flocks - zebras, giraffes, elephants, ostriches).

8) Tropical or thorny woodland(sparse deciduous forests, thorny bushes; baobabs; uneven distribution of precipitation.

9) Rainforests(a variety of trees and animals (warm and humid all the time); possums, hornbills, birds of paradise, lemurs; the vast majority of the animal world is insects.

Cycle of substances in the biosphere.

Biosphere- the complex outer shell of the Earth, which contains the entire totality of living organisms and that part of the planet’s substance that is in the process of continuous exchange with these organisms. Available two main cycles of substances: large - geological and small - biogeochemical. Thus, the great cycle is caused by the interaction of solar (exogenous) energy with the deep (endogenous) energy of the Earth. It redistributes substances between the biosphere and the deeper horizons of our planet. By the Great Gyre The water cycle between the hydrosphere, atmosphere and lithosphere, which is driven by the energy of the Sun, is also called.

Water cycle in the biosphere

Plants use hydrogen in water during photosynthesis to build organic compounds, releasing molecular oxygen. In the respiration processes of all living beings, during the oxidation of organic compounds, water is formed again. In the history of life, all free water in the hydrosphere has repeatedly gone through cycles of decomposition and new formation in the living matter of the planet. About 500,000 km 3 of water is involved in the water cycle on Earth every year.

Oxygen cycle in the biosphere

The Earth owes its unique atmosphere with a high content of free oxygen to the process of photosynthesis. The formation of ozone in high layers of the atmosphere is closely related to the oxygen cycle. Oxygen is released from water molecules and is essentially a byproduct of photosynthetic activity in plants. Abiotically, oxygen arises in the upper layers of the atmosphere due to the photodissociation of water vapor, but this source constitutes only thousandths of a percent of that supplied by photosynthesis.

The released oxygen is intensively consumed in the respiration processes of all aerobic organisms and in the oxidation of various mineral compounds. These processes occur in the atmosphere, soil, water, silt and rocks. It has been shown that a significant portion of the oxygen bound in sedimentary rocks is of photosynthetic origin. The exchange fund O in the atmosphere makes up no more than 5% of the total photosynthetic production. Many anaerobic bacteria also oxidize organic matter through the process of anaerobic respiration, using sulfates or nitrates.

Carbon cycle.

Carbon is an essential chemical element of organic substances of all classes. Green plants play a huge role in the carbon cycle. During the process of photosynthesis, carbon dioxide from the atmosphere and hydrosphere is assimilated by terrestrial and aquatic plants, as well as cyanobacteria, and converted into carbohydrates. In the process of respiration of all living organisms, the reverse process occurs: carbon in organic compounds is converted into carbon dioxide. As a result, many tens of billions of tons of carbon are involved in the cycle every year. Thus, two fundamental biological processes - photosynthesis and respiration - determine the circulation of carbon in the biosphere.

The carbon cycle is not completely closed. Carbon can leave it for quite a long time in the form of deposits of coal, limestone, peat, sapropels, humus, etc.

Humans disrupt the regulated carbon cycle through intensive economic activity.

Nitrogen cycle.

The supply of nitrogen (N 2) in the atmosphere is huge (78% of its volume). In this case, plants cannot absorb free nitrogen, but only in a bound form, mainly in the form of NH 4 + or NO 3 –. Free nitrogen from the atmosphere is fixed by nitrogen-fixing bacteria and converted into forms available to plants. In plants, nitrogen is fixed in organic matter (in proteins, nucleic acids, etc.) and transmitted through food chains. After the death of living organisms, decomposers mineralize organic substances and convert them into ammonium compounds, nitrates, nitrites, as well as free nitrogen, which returns to the atmosphere.

Phosphorus cycle.

The bulk of phosphorus is contained in rocks formed in past geological eras. Phosphorus is included in the biogeochemical cycle as a result of rock weathering processes. In terrestrial ecosystems, plants extract phosphorus from the soil (mainly in the form of PO 4 3–) and incorporate it into organic compounds (proteins, nucleic acids, phospholipids, etc.) or leave it in inorganic form. Phosphorus is then transferred through food chains. After living organisms die and with their excretions, phosphorus returns to the soil.

Sulfur cycle.

The main reserve fund of sulfur is in sediments and soil, but unlike phosphorus there is a reserve fund in the atmosphere. The main role in the involvement of sulfur in the biogeochemical cycle belongs to microorganisms. Some of them are reducing agents, others are oxidizing agents.

In terrestrial ecosystems, sulfur enters plants from the soil mainly in the form of sulfates. In living organisms, sulfur is contained in proteins, in the form of ions, etc. After the death of living organisms, part of the sulfur is reduced in the soil by microorganisms to H 2 S, the other part is oxidized to sulfates and is again included in the cycle. The resulting hydrogen sulfide evaporates into the atmosphere, where it is oxidized and returned to the soil with precipitation.

13. The main stages of the evolution of the biosphere.

He studies the main stages of the evolution of living things. paleontology - the science of fossil organisms. For the period from 5 billion years ago to the present, the following geological eras are known: Katarchean, Archean, Proterozoic, Paleozoic, Mesozoic and Cenozoic.

Archean era begins with the appearance of the first living cells. The first living cells were called prokaryotes, that is, cells that do not have membrane-bound nuclei. These were the simplest organisms capable of rapid reproduction. They lived without oxygen and could not synthesize organic matter from inorganic matter. They easily adapted to the environment and ate it. Next, according to scientists, the nutrient medium for these cells is depleted and they change and begin to exist at the expense of solar energy and themselves produce the substances they need for life. This process is called "Photosynthesis". It is the main factor in the evolution of the biosphere. From this moment the formation of the Earth's atmosphere begins, and oxygen becomes the main condition for the existence of living organisms. The ozone layer is gradually formed, and the oxygen content in the air reaches the usual 21% today. This is how evolution continues for about 2 billion years.

And in the Proterozoic, that is, 1.8 billion years ago, living organisms with cells appeared in which the nucleus was clearly expressed. After another 800 million years, these organisms, called eukaryotes, divided into plant and animal cells. Plants continued the function of photosynthesis, and animals began to “learn” to move.

900 million years ago the era of sexual reproduction began. This leads to species diversity and better adaptability to environmental conditions. The evolutionary process is accelerating.

About 100 million years pass and, according to scientists, the first multicellular organisms appear. I wonder how unicellular organisms differed before this? Multicellular organisms develop organs and tissues.

The Paleozoic era is coming and its first stage is the Cambrian. During the Cambrian period, almost all animals appeared, including those that exist today. These are: mollusks, crustaceans, echinoderms, sponges, archaeocyaths, brachiopods and trilobites.

500 million years ago large carnivores and small vertebrates appeared. After another 90 million years, they begin to populate the land. Living organisms that can exist on land and in water are called lungfish. From them came amphibians and land animals. These are ancient reptiles, similar to modern lizards. The first insects appear. Another 110 million years pass, and insects have learned to fly. In the Paleozoic era, especially during the Devonian and Carboniferous periods, the level of plant life significantly exceeded the existing level. The forests were thickets of tree-like lycophytes, giant horsetails and various ferns.

Fauna follows the path of improving seeds. The owners of land during this period are reptiles, which move further and further from water. Swimming, flying and moving on land appear. They are carnivores and herbivores.

Mesozoic. 230 million years ago. Evolution continues. Plants develop roots, stems, and leaves. A system is formed that provides the plant with water and nutrients. Reproduction methods are also changing. Spores and seeds become most suitable for these purposes on land. Deposition of unprocessed organic waste begins. Along with coal deposits, additional oxygen begins to be released.

195 million years ago - the first birds and mammals. These are: pteranodon, plesiosaur, mesosaur, brontosaurus, triceratops and others.

Cenozoic. 67 million years ago. The world of mammals, birds, insects and plants is vast. In the previous period, significant cold snaps occurred, which made some changes in the process of plant reproduction. Angiosperms received benefits.

8 million years ago – the period of formation of modern creatures and primates.

Although the process of evolution took almost 4 billion years, precellular living organisms still exist today. These are viruses and phages. That is, some precellular evolved into humans, while others remained as they were.

Today the fauna numbers about 1.2 million species, and the flora about 0.5 million.

In this article I will tell you about all the available biomes in Minecraft. Well, what are biomes? Biomes are natural and climatic zones into which the entire map in Minecraft is divided. Each biome is unique in its own way, and represents separate landscape zones with different topography.

So let's go in order...

A very large, open biome consisting entirely of water. At the bottom of the ocean there are often mountains and plains; the bottom itself consists of clay and gravel. The depth of the ocean can reach 30 blocks, and its length can reach several thousand blocks. Sometimes small or large islands can be generated in the ocean.

A relatively flat biome with undulating terrain and a lot of tall grass. Trees can also be generated, but very infrequently. There are a huge number of ravines and ponds; in addition, huge gorges can appear on the surface. The only one of the three biomes in which villages are generated. Horses can also spawn here.

This biome consists only of cacti, sand (sandstone), and dry bushes. Sometimes there are sand wells, temples and typical sand villages. Rarely, due to bugs, it is possible to encounter cacti up to 7 blocks in height.

Mountain biome, released not so long ago. Trees are generated, but infrequently. Here, more than other biomes, you can encounter such magnificent structures as cliffs, arches, overhangs, waterfalls, and floating islands. Here is the highest possibility of generating underground caves. Sometimes there are not very large lakes at sea level. Only in this biome is it possible to encounter emerald ore.

A biome with a huge number of oak and/or birch trees, and also with a large amount of tall grass.

Tundra with a considerable number of coniferous trees and dark blue grass. Quite often the taiga is generated lumpy. After update 1.7.2, there are 2 types of taiga: taiga without snow and the rarest cold taiga, in which snow falls and the water freezes.

Flat biome with many small lakes. Trees can grow in lakes, a huge number of mushrooms (mainly coffee mushrooms) grow under them, and vines grow on the foliage. In addition, you can find reeds. The water is grayish in color, with water lilies floating on its surface. There may be a considerable amount of clay in front of the water. The Witch's hut is also generated.

The only biome of the Nether. At elevations 1 and 128 it is limited by bedrock. The ocean of lava is located at height 31. In addition, lava flows faster and further than in the ordinary world. Only here ghasts, lava cubes, efreet, wither skeletons and zombie pigmen spawn. In this biome, hellish fortresses are generated.

The only biome of the Edge. It involves a low, limited area of ​​Endstone in the middle of nowhere with pillars of obsidian. Only Edge travelers, Edge silverfish and the only Ender dragon spawn here. A very interesting biome, the purpose of which is to kill the Dragon.

A snow-covered empty area with virtually no trees, the surface of rivers and lakes in this biome consists of ice.

Mushroom Island

A biome that is most often generated on a peninsula in the ocean. The soil in it is covered with mycelium. A very unique biome in which the Mushroom Cow will live.

A biome in which tropical trees and their giant variants grow - baobabs. They have quite a lot of foliage and vines, unlike other biomes; in addition, ferns grow in this biome. The biome is hilly and there are mountains. In addition, it is possible to find a temple in this biome. In tropical thickets, aggressive mobs rarely spawn because there is a lot of foliage here, so spawning is impossible.

Source: Collection of information and regulatory materials "Working conditions during geological survey work"

Editor and compiler Luchansky Grigory

Moscow, Federal State Unitary Enterprise "Aerogeology", 2004.

Characteristics of the main land biomes

The temperature regime on land changes in two directions: average annual air temperatures decrease from the tropics to the polar latitudes, the amplitudes of daily and annual temperatures increase from the outskirts to the interior of the continents. Any point on the globe is characterized by certain average daily, monthly and annual temperature amplitudes, a certain duration and temperature regime of various seasons. These features of the temperature regime limit the possibilities for the existence of organisms in a particular place.

The botanist G. Walter cited in his work “Vegetation of the Globe” a diagram of the so-called ideal continent proposed by K. Troll. Such schemes were built by many scientists, but the scheme adopted by G. Walter is one of the most substantiated. On an ideal continent, the following pattern of vegetation cover with its animal population is presented, what it would be like if the land surface did not have mountain rises, the boundaries between land and sea would be meridional, and the extent of land from west to east at different latitudes would correspond to a certain extent. the scale of its actual extent. We see that the zones generally extend from west to east and are confined to certain latitudes: they are asymmetrical, i.e. can occupy either only the western, or only the eastern, or only the central part of the continent. This scheme facilitates understanding of the geographical patterns of the location of zonal communities on the earth's surface.

Cold (polar) deserts

The vegetation does not form a continuous cover. Often up to 70% of the surface or more is occupied by gravelly, rocky soil devoid of higher plants, sometimes cracked into polygonal sections. The snow, which is already shallow here, is blown away by strong winds, often of a hurricane nature. Often only isolated tufts or cushions of plants huddle among rocky and gravelly placers, and only in low areas are patches of denser plant cover green. Plants develop especially well where birds (for example, in nesting areas, so-called bird colonies) fertilize the soil with excrement. Within the polar deserts there are few birds not associated with the sea (bunny bunting, Lapland plantain, etc.). Colonial species predominate, forming bird colonies, which in the northern hemisphere include auks (lik, puffin), gulls (glaucous gull, kittiwake, silverback, small polar, etc.), eider, and in the polar deserts of the southern hemisphere - penguins, glaucous gulls, white plovers from waders, etc. Bird colonies are confined either to cliffs or to areas of soft ground in which birds dig holes; penguins breed their young on polar ice and snow. Among mammals, some species of lemmings (Ob, ungulates) penetrate into the polar deserts, but their numbers are small. The predominant plants are lichens and mosses; there are also flowering plants (for example, blueberry, polar poppy, etc.). Insects, primarily bumblebees, as well as dipterans, take part in the pollination of these plants. Food chains are short.

In the Arctic desert (according to Bazilevich and Rodin, 1967), the phytomass reserve is 2.53 - 50 c/ha, and its annual production is less than 10 c/ha.

Tundra

Tundras are characterized by harsh growing conditions. The growing season is short – 2–2.5 months. At this time, the summer sun does not descend or only briefly dips below the horizon. There is little precipitation - 200–300 mm per year. Strong winds, especially severe in winter, blow the already shallow snow cover into depressions. Even in summer, night temperatures often drop below 0°. Frosts are possible on almost any summer day. The average July temperature does not exceed 10°. Permafrost is located at shallow depths. Under peaty soils, the level of permafrost does not fall deeper than 40–50 cm. In the more northern regions of the tundra, it merges with the seasonal permafrost of the soil, forming a continuous layer. Soils of light mechanical composition thaw in summer to a depth of about 1 m or more. In depressions where a lot of snow accumulates, permafrost may be very deep or absent altogether.

The relief of the tundra is not flat or level. Here one can distinguish elevated flat areas, usually called blocks, and interblock depressions with a diameter of tens of meters; in some areas of the tundra these low areas are called alas. The surface of the blocks and interblock depressions is also uneven.

There are hilly tundras, which are characterized by hillocks 1–1.5 m high and 1–3 m wide or ridges 3–10 m long, alternating with flat hollows. In large-hilly tundra, the height of the hillocks is 3–4 m, the diameter is 10–15 m, the distance between the hillocks ranges from 5 to 20–30 m. Large-hilly tundras are developed in the southernmost subzones of the tundra. The formation of mounds should apparently be associated with the freezing of water in the upper layers of peat, which increases the volume of these layers. Since the increase in volume is uneven, protrusion of the upper layers of peat occurs, which leads to the gradual formation and further growth of mounds.

In the more northern tundras, with a sharp decrease in the thickness of the active soil layer (which freezes in winter and thaws in summer), in winter the soil that freezes from the surface ruptures, quicksand flows onto the surface and bare spots form, between which rare plants huddle. This is spotted tundra. Some researchers believe that it can be formed under the influence of strong winds and frosts without the outpouring of quicksand: the soil from the surface cracks into polygonal units, and soil particles fall into the cracks between them, on which plants settle.

Tundra vegetation is characterized by the absence of trees and the predominance of lichens and mosses in many types of tundra. Of the lichens, bushy ones are abundant, but they give a small annual increase. According to V.N. Andreev, the annual growth of forest cladonia is from 3.7 to 4.7 mm, slender cladonia - 4.8–5.2, cetraria capulata - 5.0 - 6.3, snow cetraria - 2, 4–5.2, Easter stereo caulon – 4.8 mm. Therefore, reindeer cannot graze in the same place for a long time and can use the pastures they visit only after many years, when their main food plants, lichens, have grown. Equally characteristic of the tundra are green and, to a lesser extent, sphagnum mosses (only in more southern areas).

The vegetation cover of the tundra is very poor. There are few annuals because the growing season is short and its temperatures are low. Only where the vegetation cover is disturbed under the influence of human influences, or due to emissions from the burrows of animals that inhabit the tundra, annuals can develop in significant quantities. Of the perennials, there are many winter-green forms, which is also due to the need to make full use of the short growing season. There are many shrubs with low woody stems and branches creeping along the soil surface, pressed to the surface, as well as herbaceous turf plants. Cushion-shaped forms with closely spaced short stems are common. All of these forms of plant growth conserve heat by hugging the ground. Often plants have a trellis, elongated shape; the trellises are also pressed to the ground. Among the winter-green shrubs we mention partridge grass, cassiopeia, lingonberry, crowberry; Among the shrubs with leaves that fall in winter are blueberries, dwarf birch, and dwarf willow. Some dwarf willows have only a few leaves on squat stems. Plants with underground storage organs (tubers, bulbs, succulent rhizomes) are almost absent in the tundra, since freezing of the soil prevents this. There is an opinion that there are physically dry areas in the tundra (drying out in the summer). The reason for the treelessness of the tundra is apparently that a contradiction arises between the possibility of water entering the roots of trees and its evaporation by branches raised high above the snow surface. This contradiction is especially strong in the spring, when the roots cannot yet absorb moisture from the frozen soil, and evaporation by the branches is already intense. This is confirmed by the fact that along river valleys, where permafrost runs deep and the winds that increase evaporation are not so strong, trees penetrate quite far into the tundra.

The most correct division of the tundra by vegetation cover into three subzones: arctic, where spotted tundra is widespread, there are no closed shrub communities, and there are no sphagnum mosses; typical, where shrub communities dominate, lichen communities are widespread, especially on soils of light texture, there are sphagnum peat bogs, but not abundant; the southern one, in which sphagnum peat bogs are well developed, forest communities penetrate along river valleys.

The tundra is characterized by contrasts between the vegetation of watersheds, the changes of which from north to south were characterized by us, and depressions (between blocks, banks of rivers and lakes). Sedge and cotton grass communities predominate. Plants that have the form of squat shrubs and shrubs on watersheds reach significant sizes (1 - 1.5 m or more). The tundra soil has obvious signs of waterlogging.

In the tundra, winter and summer seasons are distinguished more clearly than in any other zone. Therefore, the differences between winter and summer animal populations are especially sharp. A significant number of bird species, which make up the majority of the vertebrate population in summer, leave the tundra for the winter. In summer, many species and numerous individuals of waterfowl nest in the tundra - ducks, geese, swans, and waders. The world of tundra passerine birds is also becoming more vibrant. The number of species and individuals remaining in the tundra for the winter is very small. Mammals include wild reindeer, species of lemmings, voles, and arctic fox; among birds - tundra partridge, polar owl and a few other species. Most tundra vertebrates are characterized by seasonal migrations. Thus, for the summer, reindeer move to the sea coasts, to the more northern regions of the tundra, where the winds to some extent reduce the intensity of the attack of midges (horseflies, mosquitoes, midges), tormenting the animals with constant bites. In winter, deer go to more southern regions of the tundra, where the snow is not so dense and it is easier for them to “hoof” it to get food. The tundra partridge, accompanying reindeer herds during winter migrations, gets the opportunity to use areas dug up by deer to search for food. Naturally, in such areas the vegetation is eaten very intensively.

As mentioned above, the nomadic lifestyle of deer is largely due to the fact that their main food plants (lichens) grow slowly and a second visit to places already used for grazing is possible only after a decade or later, so the routes of the deer herd are very long.

Rodents in winter concentrate in the areas most suitable for them (for example, on the slopes of interblock depressions, river valleys, etc.), where the snow is deeper, protecting them from the cold. As a result, the vegetation in such areas is severely grazed, and the remaining uneaten parts of the plants are washed away by water to the bottoms of relief depressions, forming peculiar mounds (10–15 m long, 20–40 cm wide), which subsequently become peaty and give rise to a finely mounded zoogenic microrelief (according to B A. Tikhomirov). Unwashed shreds of rags on the bottoms of depressions, preserved in the feeding areas of lemmings, slow down the development of plants. In the summer, lemmings move from lower areas to higher ones, using frost-breaking cracks for their passages, the moss cover at the bottom of which, under the influence of the constant running of the animals, becomes compacted, which affects the slowdown of the thawing of permafrost and the deterioration of the thermal regime of the soil.

In areas with winter burrows, lemmings fertilize the tundra soils with their excrement. The amount of food consumed by a lemming is 40–50 kg of plant mass per year (a day a lemming eats one and a half times more than it weighs). The burrowing activity of lemmings also affects the life of the tundra, although less significant than their consumption of plant food. B.A. Tikhomirov points out that the number of lemming burrows ranges from 400 to 10,000 per 1 hectare. Every year, lemmings dig up about 10% of this amount, which corresponds to mass reproduction of lemmings throwing away from 6 to 250 kg of soil per 1 hectare per year. Mass reproductions of lemmings occur on average once every 3 years. As a result, the number of animals increases so much that they undertake mass migrations, during which they overcome significant spaces, drown in rivers and are eaten by a wide variety of animals - feathered predators, arctic foxes, wolves, even reindeer and salmon fish. The discharges from lemming burrows, devoid of associated plant cover, are usually inhabited by the same plant species that live on the bare patches of spotted tundra (heart daisy, types of krutka, short-leaved fescue, arctic fireweed, double-scaled rush, etc.). The lush vegetation on these outbursts creates the impression of miniature oases in the tundra.

The long-tailed ground squirrel in the East Asian tundras, including Chukotka, where it digs deep burrows, contributes to the creation of forb-meadow communities on well-drained ejection soils.

Geese and other waterfowl also contribute to the occurrence of changes in vegetation in the tundra: after plucking the grass, the moss tundra replaces the cotton grass-moss tundra, and patches of bare soil form. Subsequently, increased aeration leads to the development of sedge-cotton grass spotted tundras, and then sedge-moss spotted tundras with blue-green nostok algae growing in the spots.

In the tundra, self-pollination of plants and pollination by wind are widespread; entomophily is poorly developed, insects rarely visit flowers. Bumblebees are the only pollinators of plants with irregular flowers - astragalus, astragalus, mytaria, and pennywort. Plants with unspecialized flowers, which have open, regular corollas with short tubes, are pollinated by dipterans mainly from the fly family. In tundra plants, especially those that self-pollinate with difficulty, vegetative reproduction is highly developed. It ensures the survival of species if insect pollination is difficult and promotes group growth, which later attracts pollinating insects. Many plants, which in other zones are pollinated by insects, in the tundra tend to self-pollinate, which is accompanied by a decrease in the size of the flowers and a cessation of their nectar secretion. The Swedish scientist O. Hagerup pointed out that on the Faroe Islands, plants pollinated by insects stay close to bird colonies or human habitation, i.e. where there are massive accumulations of rotting substances. In these clusters live the larvae of flies, which are the main pollinators of plants under these conditions.

Many flowers of tundra plants have a very short lifespan. Thus, in cloudberries, which cover vast areas of the tundra, the individual life of a flower does not exceed two days. If we take into account that during this time there are frosts, rains, and hurricane winds that prevent insects from flying, then the chances of pollination with the help of insects decrease. Many insects huddle in flowers not in search of nectar, but seek refuge here from unfavorable weather conditions. This means that they can sit in one flower for a long time, and then they will not necessarily fly to a flower of the same species, which further reduces the chances of pollination.

Gadflies accompanying herds of ungulates, although they do not bite them, lay eggs on the animals’ fur (skin botfly, gastric botfly) or spray larvae into the eyes of animals (eye botfly). Therefore, animals are very afraid of them.

Soil inhabitants in the tundra are few in number and concentrated in the upper soil horizons, mainly in peat. With depth, their number quickly decreases, since the soil is saturated with moisture or is frozen.

For many northern birds, large clutch sizes and correspondingly larger broods are noted compared to individuals of the same species living in more southern zones. This can be associated with the abundance of insects that serve as food for the chicks. The growth of young animals here is faster than in the south. Many people believe that when daylight hours are long, birds feed their young for longer periods of time. However, it should be noted that where the day is around the clock, birds sleep for a significant part of the astronomical night.

Inhabitants of northern latitudes are characterized by larger sizes than southern individuals of the same species (in accordance with the so-called Bergmann rule). This is explained not only by a more favorable ratio of body surface to body volume with increasing size in terms of heat production, but also by the fact that animals in the north reach sexual maturity more slowly, and therefore have time to grow larger. In northern animals, in comparison with their more southern individuals of the same species, relatively smaller sizes of parts protruding from the fur are observed - ears, paws (Allen's rule). The coat is relatively thicker. These rules, of course, apply only to homothermic (warm-blooded) animals.

The relatively small amount of seed food leads to a decrease in the number of granivorous birds and representatives of the most seed-eating rodents in the tundra - species of the family. mouse. There are few reptiles and amphibians in the tundra due to permafrost soils.

The phytomass in the Arctic tundra is very small - about 50 c/ha, of which 35 c/ha is the share of underground organs, and 15 c/ha is the share of above-ground organs, including 10 c/ha of photosynthetic organs.

In shrub tundras, the total phytomass does not exceed 280–500 c/ha, and the annual primary production is 25–50 c/ha, including underground parts – 23, perennial above-ground parts – 17, green parts – 32 c/ha.

In the Subantarctic of the Southern Hemisphere, phytomass reserves under optimal conditions also do not exceed 500 c/ha, but annual production is 2 times higher compared to shrub tundras, since the growing season there is more extended.

Forest-tundra

Typically, botanical geographers consider the forest-tundra to be a transitional zone and often classify it as a tundra as a special, southernmost subzone. However, if we approach the forest-tundra from a biogeographical point of view, then this is a special zone, the biocenoses of which differ from both tundra and forest ones.

Forest-tundra is characterized by light forests. Birds nesting among bushes – bluethroats, etc. – appear in significant numbers. The amount of seed food increases, which leads to an increase in the number and diversity of the mouse population. Permafrost goes deeper, and the active layer of soil, which thaws annually, no longer closes with it. Nests of corvids and small birds of prey are confined to rare trees. Forest-tundra has a special set of living conditions both in comparison with the tundra and in comparison with the forest. It is characterized by different types of trees: birch, dark coniferous trees - spruce, light coniferous trees - most often larch.

Temperate coniferous forests

These communities are characteristic only of the temperate zone of the northern hemisphere. They are formed by dark conifers - spruce, fir, Siberian cedar pine (Siberian cedar) and light conifers - larch, as well as pine (mainly on soils of light mechanical composition).

Within this zone, the warmest month has temperatures of +10 – +19°, and the coldest month – 9 – 52°. The pole of cold lies within this zone. The duration of the period with average monthly temperatures above 10° is short. There are 1–4 such months. The growing season is quite short.

Let us characterize the features of dark coniferous forest communities. They are quite simple in structure: the number of tiers is usually two or three. In addition to the tree layer, grass or herb-shrub and moss layers can be developed in cases where the forest is not dead cover. Sometimes the herbaceous layer is also absent. The shrubs are sporadic and do not form a distinct layer. The shading is significant. In this regard, herbs and shrubs reproduce more often by vegetative means than by seed, forming clumps and groups. Forest litter decomposes slowly, so some herbaceous plants do not form chlorophyll and feed saprophytically (podelnik, ladyan, etc.). There are, as in the tundra, winter green plants (lingonberry, wintergreen). Lighting, in contrast to deciduous forests, is the same throughout the entire growing season, so there are practically no plants that time the development of flowers to the early spring months. The corollas of the flowers of the plants of the lower tier are white or pale colored (pale pink, pale blue), because these are the colors that are clearly visible against the dark green background of the moss and in the twilight of the dark coniferous forest.

In an untouched dark coniferous forest, air currents are weak and there are no winds. Therefore, the seeds of a number of plants of the lower tier have negligible weight, which allows them to be transported from place to place by weak air currents. These are, for example, wintergreens (the seed weight of the single-flowered wintergreen is only 0.000004 g) and orchids (the seed weight of the creeping goodyera orchid is 0.000002 g). However, how can an embryo develop from seeds of such insignificant weight, in which the number of cells is determined by a few tens, feed itself? It turns out that for plants with such seeds, the development of embryos requires the participation of fungi, i.e. development of mycorrhiza. The hyphae of the fungus, abundant in dark coniferous forests, as in many other communities, grow together with the embryos developing from such seeds and supply them with the necessary nutrients, and then, when the embryo grows and becomes stronger, it in turn provides the fungus with photosynthetic products - carbohydrates. The phenomenon of mycorrhiza is very widely developed in forests in general, and in dark coniferous forests in particular. Many trees also form mycorrhizae. The fruiting bodies of many fungi that form mycorrhizae are edible for humans and animals. These are porcini mushrooms, russula, boletus, growing under pine and larch, boletus and aspen, associated with small-leaved trees developing in the place of cleared dark coniferous forests, etc.

Many seeds are transferred by animals that eat the juicy pulp of the fruit. Although many plants that produce juicy fruits also live in the tundra, their massive development is observed in forests (lingonberries, blueberries, bearberries), less often in the forest-tundra and southern tundra, so these food chains are characteristic of forests. It should be noted that the consumption of such juicy fruits by animals is a condition for the germination of their seeds for a number of plant species: in blueberries and lingonberries, the high acidity of the berry juice prevents the development of seeds in the untouched berry. If the berry is crushed (usually by the paws of an animal) or digested in its stomach, then the surviving seeds germinate well. The high germination and good development of these seeds are also facilitated by the excrement released from the intestines with the seeds, which serves as fertilizer for the developing seedlings. I have seen in the taiga groups of rowan, viburnum, and currant seedlings developing where excrement was left by a bear. Blackbirds successfully spread the seeds of rowan and many other forest species.

A typical way for dark coniferous forests to disperse seeds is by taking them away by ants. Some species have seeds equipped with special fleshy appendages (caruncles) that make them attractive to these forest inhabitants.

The moss cover is moisture-absorbing and, when wet, becomes heat-conducting, so the soils of dark coniferous forests can freeze very much in winter. The species composition of the tree stand, as well as the grass and shrub cover, is especially poor in the taiga of Europe and Western Siberia, richer in Eastern Siberia and the Far East, much richer in North America, where there are several species of the same genera of dark coniferous species as in Eurasia , - spruce, fir, in addition, species of the genus hemlock, pseudohemlock, etc. are represented. In the herbaceous-shrub layer there are many forms close to the Eurasian ones - shrubs, as well as other species from the genera characteristic of the Eurasian taiga - hemlock, wood sorrel, etc.

Dark coniferous taiga, like other types of forest, has a number of common features that determine the nature of the animal population. In the taiga, as in other forests, there are few herd land animals. There are wild boars, reindeer and wolves in winter. This is due to the fact that the presence of trees makes it difficult for animals to visually alert each other to impending danger. The main methods of hunting are stalking and hiding, since stealth hunting is difficult. Among birds of prey, hawks are especially characteristic with relatively short wings and a long tail, which facilitates their rapid maneuvering among tree branches and sudden attacks on victims. There are relatively few diggers in the forest, since the presence of shelters in the form of hollows, fallen trunks and depressions between superficial roots eliminates the need to dig complex burrow systems. The differences in the winter and summer composition of the animal population are less sharp than in the tundra and forest-tundra. Many herbivorous species in winter feed not on herbaceous plants and shrubs, but on twig food; such, for example, are the elk and the hare. The animal population is poor both qualitatively and quantitatively. A number of tree-dwelling species feed on the ground. Such are the forest pipit, thrushes and a number of other birds. Others, on the contrary, nest on the soil surface and feed mainly in the crowns - grouse, including hazel grouse, capercaillie, and black grouse.

In coniferous forests, seed feeds, in particular coniferous seeds, become of great importance. They do not have high yields every year; The peak harvest occurs every third to fifth year. Therefore, the number of consumers of these feeds (squirrels, chipmunks, mouse-like rodents) does not remain at the same level every year, but has peaks associated with productive years (usually occurring the next year after a high seed harvest). During years of starvation, residents of the Siberian taiga, such as squirrels, migrate to the west, during which they swim across the Yenisei, Ob, and Kama, die during the crossings, but the individuals that successfully crossed do not return, taking root in more western regions. In addition to seed feeds, as already mentioned, berry feeds in forests and swamp areas among forests, as well as pine needles, tree wood, and twig feeds are of great importance. Of the insects that eat needles, some, such as the gypsy moth, cause devastation of forests over large areas. There are numerous primary (attacking healthy trees) and secondary (attacking weakened trees) wood pests - longhorned beetles and their larvae, bark beetles, etc. Many birds eat various plant foods, some of them, for example chicken feed, are coarse, others, especially representatives passerines - seed-bearing. Often food specialization is significant. Thus, crossbills that feed on coniferous seeds have a curved beak, the upper beak of which intersects with the lower beak, which makes it easier to bend the scales of the cones. At the same time, the pine crossbill, which deals with more durable pine cones, has a more powerful beak than the spruce crossbill, which feeds mainly on the seeds of dark coniferous species - spruce and fir. The nutcracker feeds on the nuts of the sibtext-align:justify;text-indent:1.0cm pine pine and plays a large role in the spread of this tree, burying the collected seeds in the ground. Often nutcrackers “seed” burnt areas, clearings and “silkworms”, i.e. areas where the forest has been destroyed by the gypsy moth, leaving behind dead tree trunks devoid of needles.

Many species of mammals and birds whose food is associated with trees are well adapted to climbing and often live in trees. Such are the squirrels and chipmunks of mammals; nuthatches, pikas, woodpeckers among birds. Insects that feed on seeds and tree wood also play a role in the diet of birds and other animals that climb trees and nest in hollows. The predatory mammal, the lynx, climbs trees well, but the brown bear is worse.

Of the terrestrial mammals of the taiga, the most characteristic are: elk - among the ungulates, bank voles - among the rodents, and shrews - among the insectivores. A number of forest inhabitants connect tree communities with herbaceous ones. Thus, herons nest in trees in the forest, and feed along the banks of rivers and in meadows. Consumers of meadow grasses, for example, gray voles, often settle in better sheltered habitats on forest edges, near which the damage they cause to meadow vegetation or cultural communities increases sharply.

The amplitude of fluctuations in the number of rodents in forests, including the taiga, is not as significant as in the tundra, which is obviously due to the less severe climate and the protective role of taiga areas, in which the direct impact of climate on animals is mitigated.

Light coniferous forests, confined in Europe mainly to soils of light mechanical composition or replacing dark coniferous taiga after fires, are formed mainly by common pine. In Siberia and North America, primary light-coniferous forests can also be associated with soils of a heavier texture. Here, various species of larches, and in North America, pine trees, play a large role in them.

Light coniferous forests are characterized by a thinner tree stand, which is associated with the light-loving nature of larches and pines. Therefore, lichens play a significant role in their ground cover, and in some places there is a highly developed shrub layer formed by rhododendrons, brooms, viburnums, rosehips, currants, etc. In North America, these forests often contain an admixture of white fir, Douglas fir (pseudo hemlock) and a number of other species . Due to the development of the shrub layer in such forests, in addition to animals nesting in the crowns, hollows and on the soil surface, numerous species nesting on shrubs appear.

After coniferous forests are cut down, the vegetation cover and animal population change. Similar shifts are observed in fires.

The taiga is divided into the northern taiga, where communities of lichen spruce forests are widely developed; the central one, where green moss plants predominate, and the southern one, where broad-leaved species begin to appear in the forest stand, and the herbage composition contains many types of grasses characteristic of broad-leaved forests.

Biomass within the taiga varies noticeably depending on the type of forest, increasing from the forests of the northern taiga to the forests of the southern one. In the pine and spruce forests of the northern taiga, it is respectively 800 - 1000 c/ha, in the middle - 2600, in the southern - from 2800 (in pine forests) to 3300 (in spruce forests) c/ha. Aboveground biomass is significantly higher than underground. The latter is 1/3 - 1/4 of the above-ground one. The share of assimilating tissues accounts for 60 – 165 c/ha. Primary production ranges from 30 to 50 c/ha, and secondary production is 100 times less and is 90% formed by consumers of dead organic matter - saprophages (bacteria, fungi, earthworms).

Temperate broadleaf forests

They grow in milder climates than coniferous forests. Although the living conditions in them are somewhat similar to the living conditions in the taiga and light coniferous forests, there are also significant differences. First of all, unlike conifers (with the exception of larch), broad-leaved trees shed their leaves for the winter. Therefore, in early spring in these forests the trees are not covered with foliage and there is light under their canopy. In this regard, many trees (oak, beech, etc.) bloom simultaneously with the leaves blooming; shrubs (for example, hazel, wolf's bast) - before the leaves bloom. Abundant fallen leaves cover the soil surface with a thick, loose layer. Under such litter, the moss cover develops poorly, mainly at the base of tree trunks. Loose litter protects the soil from a sharp drop in temperature, and winter freezing is either completely absent or very slight. In this regard, a number of species of herbaceous plants begin to develop in winter, as soon as the thickness of the snow cover decreases enough that the sun's rays can penetrate to the soil surface. Thus, grasses also have the opportunity to use the short spring period for the development of flowers. In these forests, a group of spring ephemeroids appears, which, having finished flowering in early spring, then either vegetate or lose their above-ground organs, such as oak anemone, goose onion, etc. The buds of these plants often develop in the fall, with the buds the plants go under the snow, and in early spring, still under the snow, flowers begin to develop.

Thick litter allows a variety of invertebrates to overwinter. Therefore, the soil fauna of deciduous forests is much richer than that of coniferous forests. Animals such as moles are common there and feed on soil-dwelling earthworms, insect larvae and other invertebrates.

The layered structure of broad-leaved forests is much more complex than the structure of temperate coniferous forests. They usually contain from one (bush) to three (oak) tiers of forest stand, two tiers of shrubs and two or three tiers of herbs. Shrubs in these forests are found in less abundance than in coniferous forests, or are absent. As for the moss cover, as was indicated, due to the thick litter, it is, as a rule, poorly developed.

The fruits of the trees provide nutritious and varied food for many inhabitants. Years with high fruit yields recur more often than coniferous seed years due to more favorable conditions. The very structure of the tree trunks of a broad-leaved forest is different from that of coniferous trees: spreading powerful branches and significantly larger hollowness make these trees attractive for numerous mammals and birds to settle on them.

Among the herbaceous plants of the broad-leaved forest, most belong to the so-called oak broad-grass. Plants of this group have wide and delicate leaf blades and are shade-loving.

The layering, which is much better expressed than in coniferous forests, allows birds that are very diverse in their nesting methods to exist here. In addition to species that nest in the crowns of trees, there are many that make nests in high and low bushes.

The digging activity of animals contributes to the development of the turf process. In addition to vertebrates, ants play a significant role in soil changes. Many animal species exhibit specialization in nutrition. An example of a bird with a pronounced specialization is the grosbeak, which feeds almost exclusively on the seeds of stone fruit trees and shrubs. In the broad-leaved forests of Eurasia there are many seed-eaters: mice (forest, yellow-throated, Asian), as well as dormouse, which climb trees well (mainly in European forests). In North American forests, mice are replaced by hamsters that have the appearance of mice, as well as representatives of primitive jerboas from the genera Zapus and Napeosapus of the mouse family, which climb trees well and, like all mice, feed not only on plant food (mainly seeds), but also on animal food (small invertebrates that are successfully hunted).

Due to the strong weakening of the wind, there are many insects with slow fluttering flight in the forests. There are many forest pests, including leaf-eating insects - leaf rollers, leaf beetles, codling moths, etc. Although some species (for example, oak leaf roller) often completely clear oak trees of leaves, in the process of long evolution the plants have developed adaptations to the mass reproduction of these pests: they Leaves from dormant buds develop to replace those eaten, and soon after eating, the trees are clothed with new foliage.

Broad-leaved forests do not form a continuous strip spanning the Northern Hemisphere. They are widespread in Europe, form an island of linden forests in the foothills of the Kuznetsk Alatau, occupy a vast territory in the Far East, and also grow in the east of North America.

Of the subzones of broad-leaved forests, the northern subzone of mixed forests is transitional to coniferous forests, but the participation of broad-leaved species in the tree stand leaves a significant imprint on the living conditions in these forests, so it is advisable to classify them specifically as broad-leaved forests.

In western Europe, in the areas of the mildest Atlantic climate and adjacent to them, there are broad-leaved forests with a predominance of real chestnut and an admixture of forest beech. Further to the east, very shady beech forests with a single layer of tree stand dominate, then, without crossing the Urals, to the east, there are oak forests.

Northeastern North America has forests dominated by American beech and sugar maple, somewhat less shady than European beech forests. In autumn, the foliage of these forests turns various shades of red and yellow. In these forests there are several species of lianas - ampelopsis quinquefolia, bred in our cities under the name “wild grapes”, and several types of grapes.

Oak forests in North America occupy the more continental areas of the Atlantic states. They contain several types of oak, many types of maple, lapina (hickory), tulip tree from the magnolia family, and lianas are abundant.

The broad-leaved forests of the Far East are rich in species. There are many species of broad-leaved tree species: oak, walnut, maple, as well as representatives of genera not found in European broad-leaved forests (maakia, eleutherococcus, aralia, etc.). The rich undergrowth includes honeysuckle, lilac, rhododendron, privet, mock orange, etc. Lianas (actinidia, etc.) and epiphytes are abundant, especially in more southern regions.

In the Southern Hemisphere, in Patagonia and Tierra del Fuego, broad-leaved forests are formed by southern beech; the undergrowth contains evergreen forms, such as barberry species.

The biomass of broad-leaved forests is close to the biomass of southern double communities, equaling, according to L. E. Rodin and N. I. Bazilevich, 3700 - 4000 c/ha, and according to P. P. Vtorov and N. N. Drozdov, - 4000 - 5000 c/ha. Primary production is equal to 90–100 c/ha, according to L. E. Rodin and N. I. Bazilevich, and 100–200 c/ha, according to P. P. Vtorov and N. N. Drozdov.

Forest-steppe zone

Just like forest-tundra, forest-steppe is often considered by botanical geographers as a transition zone between forest and steppe. However, from a general biogeographical point of view, it is quite unique. Thus, the combination of small forests (kolki), in the European part mainly aspen (referred to as “aspen bushes”), and in Western Siberia – birch, with steppe grassy and shrubby areas favors the existence of a number of species that are not typical for both steppe and forest . These include rooks, for which the groves serve as nesting places, and the steppe areas serve as feeding places, numerous falcons (primarily the falcon, merlin), as well as cuckoos and other species, although widespread in forests, have optimal living conditions in forest-steppe.

Steppe zone

The steppe zone is represented in Eurasia by steppes, in Northern. America - the prairies, in South America - the pampas, in New Zealand - the Tussok communities. These are temperate zone spaces occupied by more or less xerophilic vegetation. From the point of view of the living conditions of the animal population, the steppes are characterized by the following features: good visibility, an abundance of plant food, a relatively dry summer period, the existence of a summer period of rest or, as it is now called, semi-rest. In this respect, steppe communities differ sharply from forest ones. Among the predominant life forms of steppe plants are grasses, the stems of which are crowded into turfs - turf grasses. In the Southern Hemisphere, such turfs are called tussocks. Tussoks can be very tall and their leaves are less rigid than those of tufted steppe grasses of the Northern Hemisphere, since the climate of communities close to the steppes of the Southern Hemisphere is milder.

Rhizome grasses that do not form turf, with single stems on creeping underground rhizomes, are more widespread in the northern steppes, in contrast to turf grasses, whose role in. Northern Hemisphere increases to the south.

Among dicotyledonous herbaceous plants, two groups are distinguished: northern colorful forbs and southern colorless forbs. Colorful forbs are characterized by a mesophilic appearance and large bright flowers or inflorescences, while southern, colorless forbs have a more xerophilic appearance - pubescent stems and leaves, often the leaves are narrow or finely dissected, the flowers are inconspicuous, dim.

Typical for the steppes are annual ephemerals, which bloom in the spring and die after flowering, and perennial ephemeroids, in which tubers, bulbs, and underground rhizomes remain after the above-ground parts die off. Colchicum is a peculiar species, which develops foliage in the spring, when there is still a lot of moisture in the steppe soils, retains only underground organs for the summer, and in the fall, when the entire steppe looks lifeless and yellowed, produces bright lilac flowers (hence its name).

The steppe is characterized by shrubs, often growing in groups, sometimes solitary. These include spirea, caragana, steppe cherries, steppe almonds, and sometimes some types of juniper. The fruits of many shrubs are eaten by animals.

On the soil surface grow xerophilic mosses, fruticose and crustose lichens, and sometimes blue-green algae of the genus Nostoc. During the dry summer period they dry out, after the rains they come to life and assimilate.

The steppes are characterized by a sharp multiple change of aspects, i.e. a change in the external appearance of the steppes due to the fact that flowering plants, usually developing in masses, replace each other. Less commonly, aspects are created by mass species of animals - ungulates and some rodents from mammals, larks from birds. Unlike the aspects created by plants, the aspect that owes its existence to animals is ephemeral in nature, it can appear and disappear several times a day.

The burrowing lifestyle, widespread in the steppe, is the result of the lack of natural shelters. There are many diggers in the steppe. Some of them (mole voles and mole rats) dig complex systems of burrows in search of the main food (underground parts of plants) and block the exits from them, others (gophers and marmots) dig deep burrows in which they fall into summer hibernation, which turns into a long winter, still others (mainly voles and hamsters) dig relatively shallow (~30 cm) burrows, representing a system of branched passages. Other animals that do not dig holes themselves willingly settle in other people's holes. These include invertebrates, including darkling beetles, ground beetles and many others, lizards and snakes, and even some birds, such as the grebe and the ruddy duck. These birds hatch their chicks in burrows and then transfer them to the nearest body of water. Thus, burrows can serve as shelters, as places where animals hibernate, and in some cases as feeding passages. Many burrow-building animals lead a colonial lifestyle. For colonial animals, auditory and visual warning signals are essential. When, for example, you cross colonies of gophers, you are always in the center of a circle devoid of them, on the periphery of which the animals stand at the exits of their burrows. This circle, devoid of gophers, moves with you: in front the animals hide in holes, and in the back they jump out of the holes and become living columns. At the same time, the animals whistle all the time, letting their comrades know about a possible enemy coming.

Steppe fires occurred before man entered the steppe (from lightning strikes), and with the advent of man they became commonplace. The dry grass catches fire, and the fire that has started quickly expands the front of the attack and spreads in a strip several tens of kilometers wide at the speed of a car. In this case, many animals die that did not have time to hide in holes or escape from the fire. The width of the fire strip, with its height of 2 - 3 m, is no more than a meter to one and a half, and immediately after the passing fire there remains a strip of black earth, on which only here and there tufts of steppe plants burn out and smolder. In depressions, in wheatgrass meadows among the steppe, such a fire lasts for hours.

As a result of fires, all rags and many seeds lying on the surface of the soil burn out. First of all, during fires, small-turf grasses suffer, and large-turf grasses, the growth buds of which are more reliably protected from fire by the bases of the leaves, are better able to withstand burning; Young trees also die, so steppe fires stop the advance of forests onto the steppe. After fires, the feeding qualities of steppe vegetation sharply deteriorate until fresh leaves grow; then the quality of feed becomes higher than it was before the fire.

The burrowing activity of steppe animals plays a large role in changing the nature of soil and vegetation cover. Marmots and gophers, throwing out soil from a depth of up to 2–3 m, build mounds, the soils of which can be different. If the layers of subsoil thrown by animals to the surface are rich in easily soluble salts, then the saline surface of the mounds is covered with salt-tolerant, halophilic vegetation, and if animals throw to the surface subsoil rich in carbonates or gypsum, then the soils of the mounds are settled and steppe plants settle on them. In both cases, complexity arises in the steppes. The creation of complexity is also facilitated by the fact that the very existence of the mounds causes the redistribution of snow and rainwater and the washing of low areas located between them. The complexity of the vegetation cover contributes to the diversity of the animal population.

Among the inhabitants of the steppes, as indicated, there are animals that consume underground parts of plants. In addition to the mentioned mole rats and mole rats, these are zokors in the Siberian steppes, gophers in the prairies of North America, and tuco-tucos in the pampas of South America.

Predominantly green-eating forms include a variety of voles, ground squirrels, marmots, prairie dogs and mountain hare. More omnivorous species are mice and other representatives of jerboas, hamsters, which consume seed food, vegetative above-ground and underground parts of plants and animal food. Of the birds, bustards, little bustards and many other species are euryphages. Euryphagy may be associated with drying out of green plants in midsummer and the need to switch to other foods during this period.

A number of species, as indicated, hibernate in the summer, which then turns into winter. Thus, having accumulated a significant amount of fat, gophers and marmots go into the hole - the males are the first, then, after finishing feeding the young, the females, and in the fall - the young. Gophers and marmots emerge from their burrows to the surface in early spring, just during the period of mass development of ephemerals and ephemeroids, and quickly gorge themselves; By the time the bulk of the vegetation has dried out, male animals accumulate fat and are ready to hibernate.

Mass reproduction occurs in small rodents (voles) and some insects. During these periods, the main types of food plants are destroyed and animals are forced to undertake migrations, after which the vegetation they grazed is quickly restored.

Tumbleweeds are a unique life form of steppe plants. This life form includes plants that break off at the root collar as a result of drying out, less often rotting, and are carried by the wind across the steppe; at the same time, either rising into the air or hitting the ground, they scatter the seeds. In general, wind plays a significant role in the transfer of seeds of steppe plants. There are a lot of plants with flowers here. The role of wind in the pollination of plants is also great, but the number of species in which insects take part in pollination is less here than in forests.

Temperate xerophilous herbaceous communities vary zonally and regionally. Thus, Hungarian Pashts are northern, mixed-grass or meadow variants of the steppes. In the forest-steppe zone of the European part of the Russian Federation, mixed-grass or meadow steppe communities are developed. To the south, in the steppe zone, there are two types of steppes - the more northern colorful-forb steppes and the more southern feather grass.

The steppes of Western Siberia are characterized by waterlogging processes, which lead to the participation of a significant number of marsh forms in the composition of the grass stand; salinization processes are also developed, causing the introduction of halophilic species into the grass stand. In the steppes of Western Siberia there are fewer cereals than in the steppes of the European part of Russia. These steppes are also divided into northern and southern. To the south of the mixed-grass steppes and here, as in the European part of Russia, feather-grass steppes are developed, subdivided into the more northern - colorful-feather-grass and the more southern - colorless-feather-grass. Special steppes are found on islands in Eastern Siberia. There are chalk, serpentine and four-grass steppes here.

The prairies of North America can be divided from east to west into tall grass (with a significant participation of species of the genera bearded vulture, feather grass, etc.) and short grass, where the main role is played by bison grass and grama grass. Species richness and the participation of forbs decrease from east to west. The pampas of South America represent steppe-like communities with a predominance of grasses from the genera pearl barley, feather grass, millet, paspalum, etc., and from forbs - nightshades, eryngium, verbena, purslane, oxalis, etc.

In New Zealand, there are tussock grass communities with a predominance of turf species of bluegrass, fescue, etc.

The biomass of steppe vegetation is, according to L. E. Rodin and N. I. Bazilevich, in the meadow steppes of Russia 2500 c/ha (of which the share of underground organs is about 1700 c/ha), in moderately arid steppes - 2500 c/ha (of which underground parts - 2050 c/ha), in dry steppes - 1000 c/ha (of which underground parts - 850 c/ha). According to P.P. Vtorov and N.N. Drozdov, the biomass of tall grass steppes is up to 1500 c/ha; as aridity increases, phytomass reserves drop to 100–200 c/ha.

Information on the production of xerophilic herbaceous communities: according to L. E. Rodin and N. I. Bazilevich - from 137 c/ha in meadows to 42 in dry steppes; according to P.P. Vtorov and N.N. Drozdov - in tall herbaceous communities 100 - 200 c/ha; as aridity increases, production drops to 50 - 100 c/ha.

The plowing of open spaces or areas that arose in place of destroyed forests led to a sharp change in the composition of the animal population of the steppe zone. Vast areas of crops are characterized by a sharp change in living conditions throughout the year. On vast expanses of fields there is a uniform grass cover, with which at first (from spring) mainly consumers of green plant mass are associated, which by the time the grain ripens is replaced by granivorous forms of mammals and birds; then, when the grain is harvested and the fields are plowed, massive annual migrations of the inhabitants of the fields to forest edges, boundaries and other shelters occur. When plowing, a huge number of burrows and nests of animals are destroyed. As the level of agricultural technology increases and the associated decrease in the number of weeds, the food supply of the inhabitants of the fields becomes more and more homogeneous. Migrations of animals: spring - to the fields, summer-autumn - from the fields, associated with their mass death, become regular; During migration, the death of animals increases. After harvesting, additional shelters are created for the animals; stacks, worts, etc. Living conditions in legume crops are more favorable for animals because, firstly, they are not plowed annually, and secondly, they provide complete, high-quality feed.

As forest areas are plowed, inhabitants of the steppes and partly meadows penetrate here.

Semi-deserts

If among botanical geographers there are different opinions about the correctness of identifying a semi-desert as an independent zone, then for zoogeographers a positive solution to this issue is beyond doubt for the following reasons. It is characterized by a complex vegetation cover, which is not typical for steppes, which allows the existence of animal species with different ecological characteristics. Among the cereal communities, cenoses with the dominance of Sarepta feather grass are typical. The semi-desert provides optimal conditions for the existence of many species of animals, for example, the small gopher and the black lark, which, although found in neighboring zones, find optimal conditions in the semi-desert, and some of them (the small gopher) contribute to the creation of complexity with their burrowing activity.

Deserts

Deserts can vary in temperature. Some of them (temperate deserts) are characterized by hot summers and often frosty winters, while others (tropical deserts) are characterized by year-round high temperatures. Annual precipitation usually does not exceed 200 mm. The nature of the precipitation regime is different. In Mediterranean-type deserts, winter precipitation predominates; in continental-type deserts, a significant proportion of precipitation occurs in summer. In any case, potential evaporation (from the free water surface) is many times higher than the annual amount of precipitation and amounts to 900–1500 mm per year.

The main soils of deserts are gray soils and light brown soils, as a rule, rich in easily soluble salts. Due to the fact that the vegetation cover of deserts is very sparse, the nature of the soil becomes of great importance even when visually characterizing deserts. Therefore, deserts, unlike other communities, are usually divided not according to the nature of the vegetation cover with its animal population, but according to the dominant soils. Typically, four types of deserts are distinguished: clayey, salty (often called saline), sandy and rocky, of which only the first can be considered zonal.

Desert plants are characterized by significant xeromorphism. Subshrubs predominate, often dormant in summer, sometimes with autumn vegetation. The ways of adaptation to living in arid conditions are diverse. Among the inhabitants of deserts, especially tropical deserts, there are many succulents. In temperate deserts, only organs that fall during the cold season are succulent, since they cannot overwinter at low temperatures. Succulent trees, such as saxauls with scaly succulent leaves, and shrubs devoid or almost devoid of foliage (eremospartons, calligonums and a number of others) are not uncommon. There are plants that dry out during rainless periods and then come to life again. Many pubescent plants; plants with lignified lower parts of the stems. Ephemerals use periods when deserts are more humid: in continental-type deserts with little winter precipitation, ephemerals develop after rare heavy summer rains. In Mediterranean-type deserts, where some snow accumulates by spring, ephemerals (and ephemeroids) develop primarily in early spring. The vegetation cover is far from being closed by the above-ground parts. Usually only its underground parts are closed.

Sandy deserts are also characterized by the following features of the vegetation cover: the ability to produce adventitious roots when the bases of trunks are covered with sand, as well as the ability of root systems not to die off when they are exposed as a result of sand blowing; leaflessness in plants with perennial stems; the presence of plants with long (sometimes up to 18 m) roots reaching the groundwater level. The latter, for example camel thorn, are always bright green and do not give the impression of xerophytes. The fruits of sandy desert plants are enclosed in membranous vesicles or have a system of branched hairs that increase their volatility and prevent them from being buried in the sand. Among the inhabitants of sandy deserts there are more grasses and sedges than in other types of deserts.

The burrowing lifestyle is a characteristic feature of desert inhabitants. Not only their builders are associated with burrows, but also numerous species that seek refuge in them. Beetles, tarantulas, scorpions, woodlice, lizards, snakes and many other animals climb into the holes during the hot part of the day, when life on the soil surface practically freezes. The insignificant protective role of vegetation and its low nutritional value as a result of thinning of the vegetation cover are essential features of the living conditions of animals in deserts. Only fast-moving forms, such as antelopes from mammals and hazel grouse from birds, overcome unfavorable conditions for obtaining food due to the ability to move quickly and live in large herds or flocks. The remaining species either form small groups, or live in pairs and alone.

The conditions for the existence of animals in sandy deserts are unique. The looseness of the substrate necessitates an increase in the relative surface of the paws of animals, which is achieved both in mammals and in some insects running on the substrate by the development of hairs and bristles on the paws. True, many authors believe that the development of these formations in mammals is important not so much when running on sand, but when digging holes, since it prevents the rapid shedding of sand particles and the collapse of the walls of the dug hole. Animals usually start digging burrows in more compacted areas at the base of plant stems.

The species composition of plants and animals in deserts is poor. Among the most widespread groups of animals in deserts, herbivorous termites deserve mention; they usually do not build adobe buildings here, but live underground. Ants in deserts are represented by seed-eating and predatory species. A number of herbivorous desert inhabitants have peculiar fat depots, often localized in their tails (fat-tailed jerboas, fat-tailed gerbils, etc.). The ability to go without food for a long time is also a characteristic feature of many desert inhabitants, both herbivores and carnivores.

In terms of the size of the desert phytomass, they present a very varied picture. Thus, for black saxaul forests, i.e. deserts with tree cover, phytomass values ​​exceeding 500 c/ha are noted, for ephemeral-shrub deserts - 125 c/ha. At the same time, dry biomass in the lichen-semi-shrub deserts of Syria is 9.4 c/ha, and in desert takyrs, where algae communities are developed, it is only 1.1 c/ha. Accordingly, annual primary production ranges from 100 to 1.1 c/ha, amounting to 60–80 c/ha for most types, according to P. P. Vtorov and N. N. Drozdov.

Semi-deserts and deserts of the temperate zone, often called steppes in foreign literature, are represented by wormwood, wormwood-hodgepodge, and saxaul communities in the Old World; in America they contain succulents from the cactus family. Tropical and subtropical deserts are very diverse, the flora and fauna of which differ in different geographical regions.

Thus, in Australia, a prominent role among the types of deserts is played by melgascrab with acacia melga, which, like many other Australian acacias, has flattened petioles - phyllodes - instead of leaves. In the deserts of South Africa, a significant role among plants is played by Welwitschia amazing - a gymnosperm plant with belt-shaped leaves in the Namib desert, numerous leaf succulents - aloe, as well as lithops, the leaves of which are almost entirely hidden in the soil, from stem succulents - species of euphorbia, in the Atacama desert in South America - tillandsias from bromeliads, as well as succulents from the family. cacti, etc.

From forests to deserts, the xerophilicity of communities increases. More xerophilic desert communities give way to mesophilic tropical rainforest communities.

Subtropical dry forest and shrubland zone

Among them, the first place is occupied by Mediterranean forest and shrub communities. A distinction is often made between laurel forests and shrubs and hard-leaved forests and shrubs. However, the differences between these communities are not so significant as to distinguish them into different classes of formations. This is one class that includes less xerophilic (laurel) and more xerophilous (stiffleaf) communities.

The distribution area of ​​laurel and hard-leaved communities is subtropics. They are distributed in the European-African Mediterranean, in South Africa, in North America, in Chile between 40 and 50 ° S. sh., over large areas of Australia.

A characteristic feature of this area is the discrepancy between the warm and wet periods. Maximum precipitation occurs in winter. Summer here is hot (July isotherm 20°) and dry. Winter is warm - average monthly temperatures are above 0°, the January isotherm is usually not lower than 4°, only for 1 - 2 days temperatures can fall several degrees below 0°. The average annual precipitation is 500–700 mm, but a significant part of it occurs in the cold season.

The appearance of forests in these areas is different. Where the amount of precipitation is higher, the air, due to the proximity of the sea, is more saturated with moisture and direct sunlight, penetrating through the humid atmosphere, does not burn the plants. Trees, which include, for example, the Canarian laurel, which lives on the Canary Islands, have flat, shiny, wide, leathery leaves. Sometimes forests are developed with a predominance of coniferous species with scaly flat leaves (thuja, cypress) or narrow flat needles (yew and other species). Where air humidity and precipitation are less, forests are formed by hard-leaved species, often with narrow leaves elongated parallel to the incidence of the sun's rays (such as eucalyptus trees in Australia). Tree buds are usually protected by bud scales; in shorter species, such as olive trees and undergrowth plants, scales may be absent. Epiphytes - flowering and fern-like plants - are either absent or located low (no higher than 2 - 3 m) on tree trunks. The predominant epiphytes are mosses and lichens. As a rule, the trees and shrubs of these forests are evergreen.

The layered structure of forests is as follows: two tiers of trees, less often one, a very often pronounced layer of low trees and shrubs, under which there is a grass-shrub layer. Moss and lichen cover is not expressed.

There are quite a lot of vines not only with herbaceous, but also with woody trunks (from the genera smilax, rosehip, blackberry, etc.), rising 2 - 3 m along the tree trunks.

Many plants are rich in essential oils. The herbaceous plant ash tree is called the “burning bush” because on a warm summer evening the air around it is so saturated with essential oils that it can be set on fire and a flame will break out, which, however, will not burn the stems and leaves of this plant. The growing season is compressed. Plants with deep roots that reach groundwater bloom at the beginning or end of the dry period (spring or autumn), and at the beginning of the wet period, plants with a more superficial root system, which use the upper soil horizons moistened by precipitation, begin to flower.

The animal population of these forests is quite diverse. Tree species (oaks, cyclobalanopsis, castanopsis, chestnuts, etc.), as well as coniferous species, produce significant quantities of high-quality edible fruits and seeds. Therefore, there are many species of squirrels, chipmunks, and flying squirrels. Of the terrestrial rodents, seed-eating species predominate: mice and rats in Eurasia, hamsters in North America. There are a large number of both insectivorous and granivorous birds. Many birds are sedentary. There is no real winter here and the amount of food all year round is sufficient for the life of many species of mammals and birds.

In areas dominated by subtropical laurel and hardleaf forests, a variety of plant communities are observed, partly related to the duration and severity of the dry period, partly to human activity cutting down primary forests.

In the European-African Mediterranean, laurel forests are represented by communities dominated by Canarian laurel. Many types of undergrowth also have large evergreen leaves. Ground and epiphytic ferns and mosses are abundant.

Stiffleaf forests are confined to somewhat more xerothermic areas and are formed in the Mediterranean by evergreen oaks (holm oak, and in the western part, cork oak). Such forests are quite light, so they have a rich undergrowth and grass cover. They contain strawberry tree, myrtle, cistus, tree-like heather Erica arborea, and olive, which now more often form cultural plantings. As a result of deforestation, various shrub communities have long emerged. This is most often the so-called maquis, a community spread throughout the Mediterranean. The maquis includes numerous species of evergreen shrubs, which formed the undergrowth in primary forests with an admixture of individual low trees. In some species, the leaves are ericoid, scaly, and some species have twig-like stems. Often maquis communities have a height of 6–8 m. Maquis includes pistachio, strawberry tree, cistus and many other species in various combinations.

Gariga represents the next step in forest degradation. These are shorter-growing communities, the upper tier of which is usually formed by a small number of species. This may be a scrub oak, dwarf palm or palmito. They often contain a lot of plants with a strong smell (thyme, rosemary, lavender, etc.), which prevents livestock from eating them. Many of these plants are cultivated for their aromatic substances. A variety of garigue called frigana is widespread in the eastern Mediterranean. These communities are especially characterized by plants with thorns and prickles, among aromatic plants - representatives of the Lamiaceae, as well as plants with twig-like stems. On the northern and eastern edges of the Mediterranean, where frost occurs, shrub communities include a significant number of leaf-deciduous species. Such communities are called shiblyak. This is where the lilac, widely grown in temperate countries, comes from.

In East Asia (subtropical regions of China and Japan), communities of this class of formations are widespread. Here, the hard-leaved forests are dominated by various representatives of the beech family (cyclobalanopsis, castanopsis, etc.), evergreens with leathery hard leaves, as well as subtropical coniferous trees (Yunnan pine, keteleeria, etc.). After cutting down these forests, shrub communities emerge, called “Chinese maquis”. It should be recalled that both the Mediterranean and subtropical East Asia are countries of ancient culture, where little primary natural vegetation remains. In China, for example, it was preserved only around ancient temples.

In other countries there are also communities belonging to the same classes of formations. Evergreen oaks dominate in North America. The shrubs that arise on the site of such communities are called chapparal.

Among the formations of laurel and hardleaf forests, the forests of evergreen sequoia stand apart, developed on the slopes of the Sierra Nevada and Coast Range in California. These forests are pure stands of redwood along river banks and river terraces. On the slopes it is mixed with Douglas fir, hemlock or hemlock), fir, and oak. Sequoia reaches maturity at the age of 500 - 800 years, lives more than 3000 years. The seeds have little germination, but it reproduces well by root and stump shoots. The understory includes evergreens and deciduous foliage. The shrub and grass cover also contains evergreen forms and herbaceous ones - the orchid (also found in the dark coniferous forests of Eurasia) and Cornus canadensis. In pure sequoias, the grass cover is dominated by ferns, and the ground cover is dominated by mosses. This forest is a transitional community from subtropical forest to dark coniferous forest.

In Australia, hard-leaved forests are formed mainly by eucalyptus trees, the height of which reaches 60–70 m. They have a rare admixture of trees of other species. These forests are very light, since the leaves are located edge-on in relation to the sun's rays. Therefore, the evergreen undergrowth, formed by numerous species, is very lush. There are especially many types of legumes and proteaceae. Epiphytes and flowering lianas are practically absent.

The hard-leaved subtropical shrubs of Australia are called scrub. Their vegetation cover is very close to the undergrowth of eucalyptus forests. The scrub is dominated by legume and myrtle species. The leaves are hard, edge-on, gray-green, dull, often represented by phyllodes (flattened petioles); many thorny plants. There are casuarinas with twig-like branches and bushy eucalyptus trees. The most luxuriant flowering is observed in autumn - in May, in spring - in August.

In southern Africa, hard-leaved vegetation is represented mainly by shrubs with leaves of ericoid, scaly and needle types from the family of heathers, legumes, rutaceae, buckthorns, proteaceae, etc.

L. E. Rodin and N. I. Bazilevich indicate a biomass of 410 c/ha for subtropical deciduous forest; according to P.P. Vtorov and N.N. Drozdov, fluctuations in biomass in subtropical forests and shrubs, depending on living conditions, range from 500 to 5000 c/ha, in maquis - closer to 500 c/ha. Net primary production of dry matter ranges from 50 to 150 c/ha, in communities close to maquis – 80–100 c/ha.

The tropical zone, in addition to the deserts described earlier, includes savannas and various types of tropical and equatorial forests and shrubs. Let's move on to consider them.

Savannah

Savannas are a type of vegetation in the tropical zone, usually trees and shrubs, but sometimes almost devoid of a tree layer. The amount of precipitation here is 900–1500 mm; there is usually one rainy season, followed by a dry period lasting 4–6 months. These changes from wet to dry periods create unique conditions for the existence of animals and plants. Trees often have thick bark with a thick layer of cork. They shed their leaves during the dry season. The grass cover is different - in humid conditions it is formed by tall grasses, through which it is difficult for a person to get through. In dry savannas with a longer dry period, these are either low grasses or various subshrubs, together with the grasses forming a closed grass cover. The trees are either evenly distributed among the grass, forming a community resembling an orchard in appearance, or they grow in groves alternating with areas occupied by herbs. Many trees have an umbrella-shaped crown. This crown shape favors the distribution of rainwater over the area occupied by the surface roots of these trees. In addition, the drying effect of wind during the dry period with this crown shape is reduced. With the onset of a period of drought, the above-ground parts of the grasses dry out and leaves fall from the trees. During periods of drought, fires (burns) often occur in savannas, which residents start to better fertilize the soil. At the end of the dry period, savannah trees usually bloom, and with the beginning of the wet period they put on leaves.

All savannas are characterized by an abundance of herd mammals. In Africa - the classic country of savannas - countless herds of antelopes, zebras, elephants, and giraffes are confined to them; Among the birds there is the African ostrich. In Australia, various marsupials live in the savannas, including the giant kangaroo, and there is the emu, a ratite bird. In South America there are small deer, and among the ratites - rhea. In all savannas, except Australian ones, there are many shrew-rodents. In South America, rodents are abundant in viscacha and tuco-tuco. In Africa, in addition to rodents, aardvarks also predominate. In Australia, burrowing placental mammals are replaced by marsupials - wombats, marsupial moles, etc. Termites build dense adobe structures in savannas. Some inhabitants of the savannah, such as the African aardvark, can use their strong claws to tear apart these structures, eating their owners. The abundance of large ungulates and other herbivores is the reason for the existence of a significant number of predators in savannas. Lions, cheetahs in Africa, jaguars in South America, and the wild dingo in Australia are hunters of large herbivores. In addition, savannas are characterized by carrion eaters including mammals, birds, as well as various invertebrate animals that feed on corpses. Some of the carrion-eating mammals, such as hyenas in Africa, have strong teeth and powerful head muscles, which allows them to bite even the tibia of ungulates. This is due to the fact that carrion is not very common. If the animal finds it, it strives to use the prey completely. Large birds that feed on carrion (vultures, vultures, condors) are also very characteristic of savannahs. Many of them have necks without feathers, which allows them to stick their heads deep into the carcass, pulling out the entrails. Large carrion-eating birds of prey have a mutual notification system about the availability of food. They fly high, paying attention to the behavior of other flying predators. When one of them, seeing carrion, begins to decline, this serves as a signal for the decline of other individuals. The sources of water for the inhabitants of savannas are rivers flowing through valleys overgrown with so-called gallery forests. Here, in conditions of significant air humidity, numerous blood-sucking dipterans live. In Africa, these include tsetse flies, some species of which transmit the disease of cattle raised in savannas, Nagana, which is usually fatal, while others carry sleeping sickness in humans. In South America, savannas are most often inhabited by triatomid bugs, which are carriers of Chagas disease, which, like nagana and sleeping sickness, is a trypanosomiasis. Chagas disease can affect both animals and humans.

Tropical woodlands and thorny bushes, deciduous, semi-deciduous, seasonal evergreen forests. This series of tropical communities corresponds to an increase in air humidity, an increase in annual precipitation and a more even distribution across the seasons. Let us briefly characterize these communities.

Tropical woodlands

Tropical woodlands are very diverse in structure. In Africa, in such sparse forests, baobabs and acacias are found, often, as in savannas, with umbrella-shaped crowns. In South America, tropical woodlands include caatinga and tree-shrub communities, in which trees called quebracho ("break the axe") because of the hardness of the wood play a significant role. The shape of the trunks is irregular, often curved, the trees are stocky, with crooked branches. There is no close canopy in these communities. Shrubs with crooked trunks often develop among thinned trees. Sometimes there are bottle-shaped trees, the trunk of which is thick and contains a significant amount of water. There are many succulents - cacti in South America, euphorbias - in Africa. Trees can be green all year round. Moreover, their foliage often faces the sun's rays, as, for example, eucalyptus trees in Australia. Many small-leaved trees or trees with scaly leaves. Sometimes (in Australian acacias) phyllodes are observed. These forests contain a variety of epiphytes and vines, which can be very numerous or may be completely or almost completely absent. Thorns are widespread on trees and shrubs. Very often, deciduous trees and shrubs predominate or are only found. In many deciduous trees, foliage begins to develop long before the onset of the rainy season.

Deciduous tropical forests

Tropical open forests in wetter regions give way to deciduous tropical forests. In the area of ​​their distribution, precipitation amounts to 800–1300, rarely up to 1400 mm per year. The duration of the dry period is 4 – 6 months a year. In each of the months of the dry period, less than 100 mm of precipitation falls, and in two - less than 25 mm of precipitation. In such forests, despite the name “deciduous”, a significant number of evergreen trees grow mainly in the lower tiers. However, there are fewer of them here than in semi-deciduous ones. Trees with compound leaves are common. Trees, as a rule, are gnarled and low. The bulk consists of trees of the lower tier, not exceeding 12 m. There are also emerging trees rising above the general level of the forest stand up to 20, rarely up to 37 - 40 m in height. The shrub layer is closed. There is almost no grass cover. In the lighter areas of the forest, grasses are abundant in the grass cover. Among the epiphytes, orchids and ferns are noted. Lianas often climb up trees and one another as thick as an arm. Wetter versions of these forests are often called monsoon forests, but among the monsoon forests there are also semi-deciduous ones. Teak forests are characterized by the fact that teak, which forms the upper tree layer, sheds its leaves, but among the trees of the lower layer there are also evergreen species. Sal forests are formed by tallow that sheds its leaves. In the undergrowth there are also trees that retain foliage during the dry season.

Seasonal semi-deciduous forests

Seasonal semi-deciduous forests are also very diverse. They are developed where the dry period lasts 1 - 2.5 months and the annual precipitation is 2500 - 3000 mm per year. Here, taller trees shed all their foliage at once, and epiphytic orchids go into a dormant state during the dry season. With increasing climate humidity, only emergents remain deciduous, and under their canopy all tree species retain foliage during the dry season. The general characteristic features of semi-deciduous forests are as follows. They can exist during a dry period of up to 5 months with precipitation of less than 100 mm in each month of this period. Such forests have some features characteristic of a tropical rainforest - plank-shaped tree roots, the presence of tall emergents. The differences from tropical rainforests are predominantly floristic: some species are found only in rainforests, others are found both in rainforests and in seasonal deciduous and semi-deciduous forests, and still others are present only in seasonal forests or are more abundant in them. Apparently, the layering here, as in rain forests, is poorly expressed. In both places there is no layer of bushes.

In terms of animal population, the forests of this series are similar to tropical rain forests. Termite structures are observed rising above the soil surface. Their number ranges from 1–2 to 2000 per 1 ha. Above-ground buildings usually occupy 0.5–1% of the soil surface, varying from 0.1 to 30%. The number of terrestrial mollusks, locusts, rodents, ungulates, and, in Australia, kangaroos and wallabies replacing them is increasing. The seasonal aspects of the animal population are expressed with the dominance of one or another group. Of the birds, the role of granivorous forms—weavers in Africa, buntings—in South America is increasing.

L. E. Rodin and N. I. Bazilevich indicate for savannas biomass values ​​from 268 to 666 c/ha with primary production of 73 – 120 c/ha. P.P. Vtorov and N.N. Drozdov give values ​​of 50–100 c/ha for the dry phytomass of open forests and savannas with an annual production of 80–100 c/ha. The biomass of consumers in savannas is measured in tenths of centners per hectare. In open forests, apparently, the zoomass is somewhat less than in savannas.

Tropical rainforests

They are characterized by a number of features. They grow in optimal humidity and temperature conditions. These conditions ensure maximum vegetation production, and therefore total production. The climate of the area where these forests occur is characterized by an even annual temperature range. Average monthly temperatures fluctuate within 1 – 2°C, rarely more. At the same time, the daily temperature amplitude is much greater than the differences between average monthly temperatures and can reach 9°. The absolute maximum temperatures in the forests of the Congo Basin are 36°, the minimum –18°, the absolute amplitude is 18°. The monthly average amplitudes of daily temperatures are often 7 – 12°. Under the forest canopy, especially on the soil surface, these differences decrease. Annual precipitation is high and reaches 1000 – 5000 mm. Some areas may experience periods of less rainfall. Air humidity ranges from 40 to 100%, on rainy days it stays above 90%. Although air humidity is high, which prevents the penetration of sunlight to the soil surface, the leaves of the tallest trees, exposed to direct sunlight, are in conditions of significant dryness and have a xeromorphic character.

The length of the day varies little within the equatorial and tropical zones. Even at the southern and northern borders of the tropical zone, it varies only from 13.5 to 10.5 hours. This constancy is of great importance for plant photosynthesis.

In the tropics, increased evaporation in the first half of the day leads to the accumulation of vapor in the atmosphere and rainfall mainly in the second half of the day.

Cyclonic activity in tropical rainforests is characterized by a significant frequency of hurricanes, sometimes very powerful. They can fell huge emerging trees, forming windows into the forest stand, which causes a mosaic of vegetation cover. In the tropical rainforest, two groups of trees stand out: shade-loving dryads and nomads, which tolerate significant lightening. The former develop under the canopy of an undisturbed forest. When lightened as a result of hurricanes, they cannot develop and are replaced by species that tolerate lightening, which form spots in the “windows”. When nomads reach a significant size and close their crowns, shade-tolerant trees begin to develop under their canopy.

The soils of the tropical rainforest (red, red-yellow and yellow) are ferrallitic: they are insufficiently supplied with nitrogen, potassium, phosphorus and many trace elements. The litter of tree leaves is no thicker than 1–2 cm, but is often absent. A paradoxical feature of the tropical rainforest is the poverty of its soils in water-soluble mineral compounds, which are mainly contained in trees, and once in the soil, they are quickly washed into deeper horizons.

The tropical rainforest is characterized by a significant number of tree species. With different counts (often including only trees with a diameter exceeding 10 cm or a girth of at least 30 cm), the number of their species ranges from 40 (on the islands) to 170 (on the mainland). There is a significantly smaller number of grass species - from 1 - 2 on the islands to 20 on the mainland. Thus, the relationship between the number of tree and grass species is reversed compared to temperate forests.

Of the interlayer plants in tropical rainforests, there are many lianas, epiphytes, and there are strangler trees. It can be assumed that the number of vines is several dozen species, epiphytes - more than 100 species, and strangler trees - several species; In total, there are 200–300, or even more species of interlayer plants, along with trees and herbs.

The vertical structure of a tropical rainforest is characterized by the following features: taller emerging trees are rare. The trees that form the main canopy, from its upper to lower boundaries, give gradual differences in height, so the canopy is continuous and not divided into tiers. Thus, the layering of a tropical rainforest stand with a polydominant structure (the presence of many dominant species) is not expressed, and only with an oligodominant or monodominant structure can it be expressed to one degree or another. There are two reasons for the poor expression of the layering of a tree stand in a humid tropical forest: the antiquity of the community, due to which the “adjustment” of trees of different species to each other has reached a high degree of perfection, and the optimality of living conditions, due to which the number of tree species that can exist together here is very large.

There is no shrub layer in the tropical rainforest. The life form of a shrub did not find a place for itself here, since woody plants, even only 1–2 m in height, are represented by plants with a single trunk, i.e., they belong to the life form of a tree. They have a well-defined main trunk and are either dwarf trees or young trees that subsequently emerge into higher canopy horizons. This is apparently due to insufficient light, which leads to the formation of main trunks by plants. Along with the trees, there are also plants with perennial herbaceous trunks several meters high, which are absent in the temperate zone. The grass cover of a tropical rainforest is characterized by a predominance of one species (often ferns or selaginella) with a slight admixture of other species.

Of the inter-tiered plants, we will mention first of all vines, which are extremely diverse in the way they climb trees: there are species that climb with the help of tendrils, cling, wrap around a support or lean on it. Characterized by an abundance of vines with woody trunks. Lianas under the forest canopy, as a rule, do not branch and only when they reach the tree crown do they produce numerous leafy branches. If a tree cannot withstand the weight of the vine and falls, it can crawl along the surface of the soil to a neighboring trunk and climb onto it. Lianas hold together the crowns of trees and often hold them high above the ground even when the trunks or large branches of the trees have already rotted.

Among epiphytes, several groups are distinguished. Epiphytes with cisterns are found in tropical America and belong to the bromeliad family. They have rosettes of narrow leaves that are in close contact with each other. Rainwater accumulates in such rosettes, in which protozoa, algae, and after them various multicellular invertebrates - crustaceans, ticks, insect larvae, including mosquitoes - carriers of malaria and yellow fever, settle. There are cases when these miniature pools are even inhabited by insectivorous plants - bladderworts, which feed on the listed aquatic organisms. The number of such rosettes can be several dozen on one tree. Nesting epiphytes and sconce epiphytes are characterized by the fact that, in addition to leaves rising into the air, they have either plexuses of roots (nesting epiphytes) or leaves pressed to the tree trunk (sconce epiphytes), among which and under which rich soil accumulates. nutrient organic substances. The soil from fern nests in Southern China contained from 28.4 to 46.8% humus, while the soil collected under epiphytic mosses belonging to the group of protoepiphytes contained only 1.1% humus.

The third group of epiphytes consists of hemi-epiphytes from the aroid family. These plants, having begun their life on the ground, climb trees, but maintain a connection with the earth by developing aerial roots. However, unlike those vines that are characterized by aerial roots, hemiepiphytes remain alive even after their roots are cut. In this case, they sometimes get sick for a while, but then they grow stronger, bloom and bear fruit.

The remaining epiphytes, which do not have any special adaptations to life in trees, are called protoepiphytes. This classification of epiphytes belongs to the famous German physiologist and ecologist A.F. Schimper. In relation to light, epiphytes are divided by P. Richards into shady, sunny and extremely xerophilic.

Small-sized epiphytes that settle on tree leaves are called epiphylls. They belong to algae, mosses and lichens. Flowering epiphytes, settling on tree leaves, usually do not have time to complete their development cycle. The very existence of this group of epiphytes is possible only in a humid tropical forest, where the lifespan of each leaf sometimes exceeds a whole year, and the air humidity is so high that the surface of the leaves is constantly moistened.

Strangler trees, belonging to various species, most often of the genus Ficus, are a specific group of plants of the tropical rainforest. When their seeds land on a tree branch, they begin their lives as epiphytes. Most often, the seeds of strangler trees are carried onto the branches by birds that feed on their sticky fruits. These plants produce two types of roots: one of them sinks into the ground and supplies the strangler with water and mineral solutions. Others, flat, wrap around the trunk of the host tree and suffocate it. After this, the strangler remains standing “on his own two feet,” and the tree strangled by him dies and rots.

Trees in tropical rainforests are characterized by the phenomenon of cauliflory or ramiflory - the development of flowers on trunks below the crown or on the thickest branches. This is explained by the fact that with such an arrangement of flowers, they are easier to find for pollinators, which can be either various butterflies or ants crawling along the trunks.

The second reason, according to V.V. Mazinga, is the formation of large fruits with large seeds by many trees, which is necessary for the successful development of seedlings in the low soil fertility of a tropical rainforest. Such fruits cannot be supported on thin branches, and the absence of a thick layer of cork makes it possible to develop dormant shoots, including flowering ones, anywhere on the trunk.

Trees of the tropical rainforest are characterized by a number of morphological features. Leaf blades of many species have “drip” drawn ends. This helps rainwater drain from the leaves more quickly. The leaves and young stems of many plants are equipped with a special tissue consisting of dead cells. This fabric - velamen - accumulates water and makes it difficult to evaporate during periods when there is no rain. Most of the feeding (sucking) roots of trees are located in the surface litter horizon of the soil, which is much less thick than the corresponding soil layer of temperate forests. In this regard, the resistance of tropical rainforest trees to the action of winds and, especially, hurricanes is low. Therefore, many trees develop plank-shaped roots that support the trunks, and in wetter, swampy areas, stilt roots. The plank-shaped roots rise to a height of 1 - 2 m. These buttresses, supporting trees of tropical rainforest, often reach enormous sizes.

There is little seasonal change in tropical rainforests. Leaf fall can be of different types. Very rarely, individual emergents, those most exposed to meteorological conditions not modified by the forest canopy, can stand without leaves for several days. The change of foliage in the majority of trees can occur continuously throughout the year, it can occur differently on different shoots, and finally, periods of leaf formation and dormancy can alternate. In the buds, most often the leaves do not have special protection; less often they are protected by the bases of the petioles, stipules or scaly leaves. The annual layers either do not develop at all, or begin to develop when the tree reaches a certain age, or do not form closed circles. Therefore, the age of trees in tropical rainforests can be determined only very approximately by the ratio of the height of the tree and its annual growth.

Tropical trees can bloom and bear fruit continuously throughout the year or several times a year; many species bloom annually or once every few years. Abundant fruiting does not always follow abundant flowering. There are monocarpics - which die off after fruiting (some bamboos, palm trees, grasses). However, monocarpics are found less frequently here than in seasonal climates.

T. Whitmore distinguishes three phases in the life of a tropical rainforest - clearings, forest construction, and its maturity. Any combination of species that dominate a given area of ​​the forest does not remain constant, as A. Obreville points out: in the place of one or another dead tree, a tree of a different species has a greater chance of growing than a tree of the same species.

Tropical rainforests have been heavily modified by humans. During the phase of primitive culture, the influence of man on the life of the forest was no more intense than the influence of the animals that inhabited this forest.

During the phase of the traditional culture of the local population, the impact of the slash-and-burn farming system was observed, in which crops and plantings in place of cut-down and burned forest areas exist for a year or three, after which such areas are abandoned and forest is regenerated on them. Under traditional culture, the development of monsoon forests was observed in places, and then savannas in place of tropical rainforests, where human impact was stronger.

The introduction of modern European and North American culture leads to the destruction of forest over vast areas, to its replacement by secondary forests and various non-forest communities, including cultural lands.

The biomass of tropical rainforests is significant. It is usually 3500 - 7000 c/ha in primary forests, rarely 17000 c/ha (in the mountain rainforests of Brazil), in secondary forests it is 1400 - 3000 c/ha. It turns out to be the most significant of the biomass communities on land. Of this biomass, 71–80% is the share of non-green above-ground parts of plants, 4–9 is the share of above-ground green parts, and only 16–23% is the share of underground parts that penetrate the soil to depths of 10–30, rarely deeper than 50 cm. Total The foliage area ranges from 7 to 12 ha for every hectare of soil surface.

The annual net production is 60 - 500 c/ha, i.e. equal to 1 - 10% of the biomass, the annual litter is 5 - 10% of the biomass.

Among the inhabitants of tropical rainforests, many are associated with canopies. These are monkeys, prosimians, sloths, squirrels, flying squirrels, woolly wings, among insectivores - tupai, similar to squirrels, mice and rats. Some of them, such as sloths, are inactive and spend a long time hanging from branches. This makes it possible for algae to settle in the grooved hair of sloths, giving the animal a green color that makes it invisible against the background of foliage. Due to this way of life, the hair of this animal does not grow from the back to the belly, as in most mammals, but from the belly to the back, which facilitates the drainage of rainwater. Many mammals - woolly wings, flying squirrels, as well as reptiles - flying dragons from lizards, flying frogs from amphibians - have adaptations for gliding flight. There are many animals and hollow-nesting birds. These include squirrels, chipmunks, rats, tupai, woodpeckers, hornbills, owls, bearded birds, etc. The abundance of snakes climbing branches, including species that feed on bird eggs, leads to the development of special adaptations. Thus, male hornbills wall up holes in hollows with clay where their females sit on their eggs in such a way that only the beak of the females protrudes from the hollow. Males feed them throughout the incubation period. If the male dies, the female is also doomed to death, since she is not able to break off the layer of clay from the inside and leave the hollow. At the end of incubation, the male releases the female he has walled up.

Plant materials are used to build nests by representatives of a wide variety of animal groups. Weaver birds build bag-like nests closed on all sides with narrow entrances. Wasp nests are made from a papery substance. Some types of ants make nests from pieces of leaves, others from whole leaves that continue to grow, which they pull towards each other and fasten with cobwebs secreted by their larvae. The ant holds the larva in its paws and uses it to “stitch” the edges of the leaves.

Weed chickens build nests on the surface of the soil from piles of rotting leaves. Such nests are maintained at a temperature sufficient for incubation of eggs and hatching of chicks. When the chicks hatch, they do not see their parents, who have long since left the nest, and lead an independent lifestyle.

Termites are common inhabitants of tropical rainforests; they do not, or almost never, build adobe structures here, as in savannas. They, as a rule, live in underground nests, since they cannot live in light, even diffused light. To climb tree trunks, they build corridors from soil particles and, moving along them, eat tree wood, which is digested in their intestines with the help of symbionts from among protozoan animals. The weight of soil particles lifted by termites onto tree trunks averages 3 c/ha (observation by the author in Southern China).

The abundance of natural shelters leads to a decrease in the number of burrowing forms of mammals. A specific feature of the soils of tropical rainforests is a large number of large earthworms, reaching a meter or more in length. High humidity of the air and soil surface is the reason why representatives of leeches, which in other biomes live in water, come to land. Ground leeches are abundant in tropical rainforests, where they attack animals and humans. The presence of hirudinin in their saliva, which prevents blood clotting, increases blood loss in those animals that land leeches attack.

The abundance of diverse species and life forms leads to the development of complex symbiotic relationships. Thus, a number of plants in tropical rainforests have special voids in their trunks where predatory ants settle, protecting these plants from leaf-cutter ants. To feed these predatory ants, host plants develop special protein-rich bodies called Belt bodies and Müller bodies. Predatory ants, settling in the trunks of plants and feeding on the high-calorie food provided by the plants, prevent any insects from penetrating the trunks and destroying the leaves of the host plants. Leaf-cutter ants (umbrella ants), cutting off pieces of tree leaves, transport them to their underground nests, chew them and grow certain types of mushrooms on them. Ants ensure that mushrooms do not form fruiting bodies. In this case, at the ends of the hyphae of these fungi, special thickenings appear - bromination, rich in nutrients, which the ants use mainly for feeding their young. When a female leafcutter ant goes on a mating flight to start a new colony, she usually takes pieces of the fungal hyphae into her mouth, allowing the ants to grow bromides in the new colony.

Probably in no community are the phenomena of protective color and form so developed as in the tropical rainforest. There are many invertebrates here, the very name of which indicates their similarity to parts of plants or some objects. These are stick insects, wandering leaves and other insects. Aposematic, bright, intimidating coloration, warning that the animal is inedible, is also widespread in tropical rainforests. Often the way to save harmless species of invertebrates is to imitate such poisonous forms with their bright, frightening colors. This coloration is called pseudoaposematic or pseudo-repellent. The necessary conditions for such pseudo-aposematic coloration to operate are: coexistence of harmless, non-poisonous forms with those they imitate, and their significantly smaller numbers compared to those poisonous forms that are the object of imitation. Otherwise, predators will more often grab harmless imitators than poisonous objects of imitation, and the instinct warning against eating these poisonous forms will not be developed.

Although every inhabitant of a tropical rainforest has a certain daily rhythm of activity, general manifestations of activity, including loud cries, are characteristic of the inhabitants of this forest around the clock. The voices of many small animals are deafening. Thus, small birds can have very loud voices, which apparently helps them find individuals of their own species among dense foliage, and also creates misconceptions among enemies about the size of the screaming animal. During the day, the forest is dominated by the calls of cicadas and various diurnal species of birds, at night - by the voices of nocturnal birds, frogs, toads and woodlings. All this reinforces the impression of the rich life of the tropical rainforest.

In the area of ​​tropical rainforests, two types of cultural landscapes predominate: plantations and irrigated ones, mainly rice fields.

Plantations of coconut palm, breadfruit, mango, hevea and other trees are, as it were, extremely thinned and severely depleted forests. They are characterized by a relatively small number of species of synanthropic animals that are absent in forests (sparrows, magpies, crows, etc.). There are much more forest animals that constantly live on plantations or periodically visit them.

Fields that are flooded for a long time have a unique animal population. Among the birds, the mynahs, mynas and others visit these fields mainly during the period of maturation of the cultivated plant. A huge number of herons, rails, and duck birds feed here during periods when there is a lot of water. Many invertebrates, such as mollusks, have adapted to periodic changes in moisture conditions.

These are the main zonal communities of land. To complete the picture, it is necessary to briefly characterize the intrazonal communities of mangroves, characteristic primarily of the equatorial and tropical zones. These communities develop in the tidal zone. The trees that live here have leathery, tough, succulent leaves (the plants are succulents) because the abundant ocean water contains significant amounts of salts. The development of stilted roots helps them stay in semi-liquid silt. The lack or absence of oxygen in the soil inhabited by mangrove communities is the reason for the development of respiratory roots by trees, which have negative geotropism and rise upward from the soil. It is typical for the trees living here to germinate seeds directly in the inflorescence. Such a sprout can reach a length of 0.5 - 1.0 m. Falling into the ground with its heavy, pointed lower end down, these sprouts stick into the ground and are not carried away by tidal biscuits, which is very important for the regeneration of trees that form mangroves. There can be no talk of any shrub or herbaceous layer here: this is prevented by sea level fluctuations and semi-liquid soil.

The inhabitants of mangrove communities (hermit crabs, crabs) have adapted to life in two environments. Reproducing in water, they use the surface of the soil of mangrove communities for feeding during low tides. The ground is often riddled with burrows of many of these animals. Mudskipper fish can see both in water and in the air. They often lie on the stilted roots and branches of mangrove trees and feed on both the numerous aerial inhabitants of these communities (dragonflies, mosquitoes and other dipterans) and aquatic invertebrates. The crowns of mangroves are often inhabited by typically terrestrial forms - parrots, monkeys, etc. The number of tree species forming communities is very limited and in each specific case does not exceed several species.

Inland waters

There are two main types of inland water bodies: standing (lakes, swamps, reservoirs) and flowing (springs, streams, rivers). These types of reservoirs are connected by transitional forms (oxbow lakes, flowing lakes, temporary watercourses).

Flowing reservoirs, as a rule, have fresh water. Salty springs and streams, especially rivers, are very rare. The salinity of stagnant bodies of water can vary sharply both in the composition of salts (with a high content of calcium carbonate, or lime, with a predominance of table salt, potash, Glauber's salt, soda, etc.), and in their quantity (from tenths of ppm to 347%o . in Lake Tambukan in the Caucasus). Stickleback fish can exist at salinity up to 59% o; larvae and pupae of enhydra flies – up to 120 – 160°/oo; at salinities exceeding 200%o, only a few species can exist; at salinity close to the maximum, i.e., 220% o, often only crustaceans live in lakes.

Water hardness - the content of calcium carbonate, is also a regulating factor, although even the hardest waters contain no more than 0.5% salts, i.e. they are fresh. Some inhabitants of inland waters, such as freshwater sponges and bryozoans, prefer hard water, while others, such as mollusks, prefer soft water. Reservoirs with hard water are, as a rule, confined to areas of development of limestone and dolomite, while reservoirs with soft water are associated primarily with areas of igneous rock outcrops.

In the inhabitants of fresh waters, their body fluids are hypertonic, that is, the concentration of salts in them is higher than in the water in which these organisms live. According to the laws of space, the water surrounding them strives to penetrate their bodies. To avoid swelling and death, the inhabitants of fresh waters must have either shells that are relatively impenetrable to the penetration of water, or special devices for removing water that penetrates the body (pulsating vacuoles in protozoa, kidneys in fish, etc.). Perhaps it was precisely because of these difficulties of existing in fresh water that representatives of many types of marine animals were not able to penetrate into inland waters.

The body fluids of the inhabitants of salty waters, including the oceans, are isotonic or slightly hypotonic (they have a salt concentration equal to or lower than in the environment), and the inhabitants of these waters themselves have special devices for releasing excess salts into the water. Obviously, the upper limit of life in inland waters is due to the fact that the salinity in them is so high that the excretion of salts from the body becomes impossible. The toxicity of such concentrated salt solutions probably also plays a role.

In inland water bodies, the content of organic matter and the associated amount of dissolved oxygen varies sharply. Reservoirs rich in humic acid (dystrophic) are associated with swamps and have dark-colored water. Their banks are peaty and the water is highly acidic. The organic world is poor. Gradually they turn into swamps. A significant content of organic substances in inland waters can lead to the so-called “bloom”, in which oxygen reserves are exhausted, fish and many invertebrate animals die. The death of aquatic animals (death) can also occur as a result of the enrichment of river and lake waters with organic substances due to anthropogenic impacts.

The temperature regime of inland water bodies is primarily related to the general climatic conditions of the areas in which the water bodies are located. In lakes of the temperate zone in summer, surface waters warm up more than bottom waters, so water circulation occurs only in the warmer surface layer, without penetrating deeper into layers of water with a lower temperature. Between the surface layer of water - the epilimnion and the deep layer - the hypolimnion, a layer of temperature jump is formed - the thermocline. With the onset of cold weather, when the temperatures in the epilimnion and hypolimnion are comparable, autumn mixing of water occurs. Then, when the water in the upper layers of the lake cools below 4°, it no longer sinks and with a further drop in temperature it may even freeze on the surface. In the spring, after the ice melts, the water in the surface layers becomes heavier, sinks, and at 4° spring mixing of the water occurs. In winter, oxygen reserves usually decrease little, since bacterial activity and animal respiration are low at low temperatures. Only if the ice is covered with a thick layer of snow does photosynthesis in the lake stop, oxygen reserves are depleted, and winter fish kills occur. In summer, the lack of oxygen in the hypolimnion depends on the amount of decomposing substances and on the depth of the thermocline. In highly productive lakes, organic matter penetrates from the upper layers into the hypolimnion in much larger quantities than in low-productive lakes, so oxygen is also consumed in large quantities. If the thermocline is located closer to the surface and light penetrates into the upper part of the hypolimnion, then the process of photosynthesis covers the hypolimnion and there may not be a lack of oxygen in it.

In lakes in cold countries, where the water temperature does not rise above 4°, there is only one (summer) mixing of water. They are covered with ice for a long time - 5 months or more. In subtropical lakes, in which the water temperature does not fall below 4°, there is also only one (winter) mixing of water. Ice does not form on them.

Thermal (hot and warm) springs are very unique, the temperature of which can reach the boiling point of water. In hot springs with temperatures exceeding the coagulation temperature of living protein and ranging from 55 to 81 °, blue-green algae, bacteria, some aquatic invertebrates and fish can exist. Most inhabitants of warm reservoirs, however, cannot tolerate temperatures exceeding 45°, and form a very unique biota of thermal springs, as a rule, from stenothermic species.

In contrast to thermal species, rivers and springs originating from glaciers and high-mountain snow fields have very cold water and are inhabited by very specific stenothermic, cold-loving species.

The movement of water in inland reservoirs is represented by waves and currents. The disturbances are well expressed only in large lakes; in the rest they are insignificant and do not reach strength, although to some extent comparable to disturbances in the oceans and seas. Lake currents replicate ocean currents in miniature. Flowing reservoirs differ greatly from each other in flow speed, starting with fast-flowing mountain streams and rivers, often with waterfalls and rapids, and ending with flat watercourses with a very weak current, measured in fractions of a meter per second.