A biome is a large regional or subcontinental system. The classification of terrestrial ecosystems into biomes is based on vegetation types and basic invariants. physical characteristics landscape. The geographical distribution of biomes corresponds to the soil-climatic zones of the continents. They exist for a long time and are sufficiently adapted to the specific physical and geographical conditions of the environment. Here is a brief description of the main terrestrial biomes of the world.
Tundras are located in the polar latitudes of the northern hemisphere, between taiga forests in the south and polar ice in the north. total area arctic tundra - about 8 million km2. Small in area, but ecologically similar areas are found in the highlands above the upper limit of forest distribution. The main limiting factors here are low temperatures and a short growing season (average annual temperature is below 0°C). The soil, with the exception of a thin top layer, remains permanently frozen (“permafrost”). The tundra is essentially wet arctic grassland with vegetation consisting of grasses, sedges, shrubs, and, in drier places, lichens ("reindeer moss").
Boreal coniferous (taiga) forests stretch in a wide strip across Eurasia and North America. They occupy an area of more than 10 million km2. Mountainous areas with such forests occur even in the tropics. The main tree species are represented here by coniferous evergreen trees - various types of spruce, fir, pine, etc. During the whole year, dense shade reigns in such forests, so the shrub and grass layers are usually poorly developed. However, a continuous green cover that contains chlorophyll persists throughout the year, and therefore, despite low temperatures for 2/3 of the year (average annual temperature from -10 to +4 ° C), this biomare is characterized by a fairly high level of annual production. . Coniferous forests are the world's largest suppliers of timber.
Temperate mixed forests occupy areas with a relatively large amount and uniform distribution of precipitation (600-1500 mm per year) and moderate average annual temperature (4 - 16 ° C), which, as a rule, is characterized by clear seasonal fluctuations. The woody vegetation of these forests is made up of various types of coniferous and deciduous trees: pines, oaks, beeches, maples, elms and many others. The shrub and grass layers, as well as soil biota, are well developed here. Such forests covered more than 12 million km2, in particular, all of Central Europe, east North America, East Asia, parts of South America, Australia and New Zealand. As we move from high latitudes to lower latitudes, the proportion of evergreen deciduous tree species in the forests increases, which gave reason to some authors to divide this biome into deciduous forests of the temperate zone and humid evergreen forests of the warm temperate (subtropical) zone. However, there are no clear biogeographic boundaries between these two forest types of vegetation, and the second of them does not form a clear geographical zone. The mixed forests of the temperate zone are the most important biotic regions of the world, since it is in these regions that civilization has reached its highest development. As a result, this biome has changed greatly under the influence of human activity, and more than 75% of its area has been replaced by cultural groups.
Hardwood evergreen forests develop in areas with a warm temperate (subtropical) climate, where it rains in winter and dry in summer. The vegetation consists of coniferous and deciduous trees and shrubs with tough evergreen leaves. These are various types of evergreen oaks, as well as pines, cedars, cypresses, eucalyptus trees (in Australia), araucaria (in Chile) and many others. Such groups are common in the Mediterranean, California, Mexico, South Africa, Chile and South Australia. The area of their primary distribution did not exceed 1.5 million km2. As a result of anthropogenic impact, most of these forests are now represented by degraded shrub thickets (the so-called maquis - in the Mediterranean, chaparral - in North America).
The steppes of the temperate zone are located where, at moderate average annual temperatures (0-16 ° C), the amount of precipitation (250-750 mm) insufficient for the development of forest vegetation falls). Vast steppe expanses occupy 9 million km2 in the interior of Eurasia, North America, in the south of South America and in Australia. The vegetation cover of the steppes is based on herbaceous plants - cereals, as well as composite flowers, legumes, etc. Extremely fertile chernozem soils develop in the steppe ecosystems, so a significant part of them is now occupied by arable land. Feature natural steppes- the presence of large herbivores (bison, antelopes, saigas, etc.), which, together with periodic fires, helps to maintain the structure of the steppe ecosystems.
Tropical savannahs (steppes with sparse trees or groups of trees) are located in warm areas (average annual temperature above 16°C), where there is a large amount of precipitation (1000-1500 mm) during the year, but there are 1-2 long dry seasons when fires, which is an important environmental factor. Large areas of this type are found in Africa, South America and Australia (about 15 million km2 in total). The plant cover is dominated by a variety of cereals. The landscape of the African savannah is dotted with picturesque acacias, baobabs, euphorbiaceae and palm trees. The African savannah is unmatched in the abundance and diversity of herbivores.
Deserts are common in areas where less than 250 mm of precipitation falls during the year. They occupy about 30 million km2 on all continents of the world. Plants and animals of the desert are adapted to the lack of water in different ways. The sparse vegetation cover consists of annuals, ephemera, succulents and desert shrubs. Vast areas of "bare ground" deserts are not necessarily devoid of life. Mosses, algae and lichens can exist here. Animal world The desert is also quite rich: it is a variety of insects, reptiles, birds and mammals.
Moist deciduous tropical forests are common in areas with a humid tropical climate (average annual temperature above 20 ° C, annual rainfall exceeding 1500 mm), where the dry season is pronounced, during which most trees lose their leaves. The main factor here is seasonal fluctuations in the amount of precipitation that is quite significant during the year. In terms of species composition, seasonal rainforests are second only to tropical rainforests. They occupied an area of more than 7.5 million km2 in tropical Asia, Africa and America.
Moist evergreen (rain) rainforests are the ecosystems where the diversity of life reaches its maximum. Over 2000 mm of precipitation falls here, which is more or less evenly distributed throughout the year. The rainforests of the world are concentrated in three main areas: the Amazon and Orinoco basins in South America and the Central American isthmus; the Congo and Niger basins in Central and West Africa; Malay Peninsula and South Islands East Asia and New Guinea. More than 50% of the total biotic diversity of the planet is concentrated in these ecosystems. The primary area of their distribution covered about 12 million km2, but as of 1990, the area of rain forests (together with secondary forests in their place) was only 7 million km2 (World Resources 1994-95). Tropical deforestation is one of the main environmental issues modern world.
The ironic scrub, or dry rainforest, is found where moisture conditions are intermediate between desert and savanna or seasonally wet. tropical forest. Such vegetation occupies large areas in Tropical Africa, South Asia, Australia and South America (more than 2 million km2). The main climatic factor here is the unfavorable distribution of the generally sufficient amount of precipitation. These are forests or woodlands, consisting of small deciduous trees and shrubs, which are often thorny.
It is more expedient to attribute mountain ecosystems to provincial ones, since they have a rather peculiar character due to the variety of physical conditions and relief features. their groupings are located in the form of altitudinal belts. In particular, in the Carpathians, altitudinal belts of oak (broad-leaved) forests (up to 400 m), beech and mixed forests(400 - 1000 m), spruce forests (1000 - 1300 m), subalpine meadows and slates (1300 - 1800 m), alpine meadows (above 1800 m). The vegetation of each belt has analogues in the lowland biomes (for example, alpine meadows with ecological features resemble the tundra, spruce forests- taiga). At the same time, the isolation of mountain ecosystems from each other and from their lowland counterparts, as well as specific relief and climate conditions, entail a high level of biota endemism (i.e., a significant number of plant and animal species that are distributed in small limited areas).
Freshwater ecosystems are conveniently divided into three groups:
1) non-flowing, or ribbon (from lat. lenis - calm) ecosystems - lakes and ponds;
2) flowing, or lotic (from lat. lotus - washing) ecosystems - streams and rivers;
3) swamp ecosystems.
Compared to marine and terrestrial freshwater ecosystems, they occupy an insignificant part of the Earth's surface, but their importance to humans is enormous. Fresh water is the most convenient and cheapest source of water for domestic and industrial needs. In addition, they are a convenient and cheap recycling system. Almost all Largest cities of the world are located on large rivers, lakes and estuaries, which serve as free collectors. Mankind is so vicious with the use of this natural resource that water now threatens to become a major limiting factor for humans as a species.
marine ecosystems
The most interesting from an ecological point of view are the following characteristics of the marine environment:
1) the world ocean occupies 70% of the Earth's surface;
2) life is observed at all depths of the oceans, however, near the continents and islands, the waters are most densely populated;
3) the sea is continuous and is not divided into isolated areas, like land or fresh water;
4) there is a constant circulation of water in the sea due to horizontal and vertical currents;
5) dominate the sea different kind waves, ebbs and flows occur, caused by the attraction of the Moon and the Sun;
6) the average salinity of sea water is 3.5% ( fresh water- less than 0.05%);
7) sea water is alkaline (normal pH = 8.2), but often poor in vital nutrients.
In the World Ocean, oceanic regions (most of the open ocean), continental shelf regions (coastal regions where the most favorable conditions for life) and upwelling regions (where cold deep waters rich in nutrients rise to the surface) are distinguished. Upwelling biomes support colossal populations of fish and seabirds. They are located along the western coast of Africa and the Americas.
As can be seen even from this short description, the biosphere of the planet consists of various ecosystems, the functioning of which occurs according to the general laws of energy conversion and the circulation of substances. All natural ecosystems have a common feature - their biota is not only maximally adapted to the specific physical conditions of the environment, but also at the same time exerts a certain influence on the environment, realizing the energy, biogeochemical, water transformation, organizational and environmental functions of the biosphere.
Biomes are the largest terrestrial ecosystems corresponding to the main climatic zones of the Earth (desert, grassy and forest); aquatic ecosystems - the main ecosystems that exist in the water sphere (hydrosphere). Sometimes in the literature there is a close, but less clear classification, primarily highlighting tropical rainforests, savannahs, deserts, steppes, temperate forests, coniferous (taiga), tundra.[ ...]
Biomes - landscape-geographical zones (tundra, taiga, broad-leaved forests, desert, etc.).[ ...]
A biome is a set of plant and animal species that make up the population of one natural zone and is characterized by a certain type of community structure, expressing a complex of adaptations to environmental conditions.[ ...]
The biomes inhabiting the habitats are characterized by certain climax vegetation and certain animal species. There is a close relationship between both components (groupings) of the biome.[ ...]
All of these biomes are terrestrial. You can add freshwater and marine to them, which, of course, can be subdivided in more detail.[ ...]
One or several communities of animals and plants can live in one biome, and the species diversity of communities depends on its age, climate, productivity, etc.[ ...]
Terrestrial biomes are distinguished here by natural or original features of vegetation, and types of aquatic ecosystems by geographical and physical features. Listed in Table. 2 sixteen main types of ecosystems represent the environment in which human civilization developed. These are the main biotic communities that support life on Earth.[ ...]
Most of the Earth's biomes are usually dominated by several plant species of the same growth form. In many cases, these plants belong to different genera and families, and they arose independently from other plants belonging to other forms of growth, in other words, they are the product of evolutionary convergence. Convergence is particularly pronounced in tropical rainforests, where hundreds of tree species with very similar appearance and leaf shape can be found in the same forest. In these communities, existing in optimally bla-. In favorable environmental conditions, competition for a place in the tree layer to the greatest extent determines the shape of trees. In addition to the trees of the main tier, the local forests include species of a wide variety of growth forms. However, trees that do better under such conditions vary within a very narrow range of leaf shape and type, most notably in soil requirements and reproductive adaptations. The phenomenon of evolutionary convergence is also well expressed in communities exposed to harsh environments. Two communities that are similar in the importance of features of wide adaptation, but different in most other respects - desert and plankton - can illustrate this phenomenon.[ ...]
The boundaries of the distribution of biomes are determined by the landscape components of the continents; as a rule, the name contains the dominant vegetation (forest, shrub, etc.). In aquatic ecosystems, plant organisms do not dominate; therefore, physical signs habitats ("stagnant", "flowing" water, open ocean, etc.).[ ...]
Omega variety. Diversity of biomes in epsilon space. For its analysis, geographical maps of different scales and the methodology of their study using geographic information systems are used.[ ...]
On our planet, there is a change of biomes in the latitudinal (from south to north) and vertical (when climbing mountains) directions.[ ...]
Significant transformations within biomes and a shift in their balance between ecosystems of a lower order inevitably cause self-regulation at a higher level. This is reflected in many natural processes - from changes in the depth of groundwater to the redistribution of air flows. A similar phenomenon is also observed at the level of very large systems of the biosphere when the ratio between biome territories changes. In the course of land development, in the broadest sense of the word, both component and territorial balance are disturbed. To a certain extent, this is permissible and even necessary, because only in a non-equilibrium state are ecosystems able to produce useful products (recall the formula for net community production). But not knowing the measure, a person strives to get more than nature can give, forgetting that reserves have a foundation of a great many elements that are not yet included in the concept of "resources".[ ...]
This is a general flowchart for grassland biome models typical of a number of western US states. The purpose of constructing the model was to study the intraseasonal dynamics of both the meadow biome as a whole and its parts - vegetation cover, animals, and soil, taking into account the influence of climate and anthropogenic impacts. To characterize the behavior of the system, the constants and variables of the model are singled out. The latter are divided into external and internal variables. External control variables affect the performance within the system. The most important external control variables include precipitation, solar radiation, temperature and wind speed over vegetation. Next, we consider a set of internal state variables (levels). These variables change from step to step in response to changes in external controls or other internal variables. Examples of such variables are the moisture content in the soil layers, green mass, and the number of animals. Rates (speeds of processes), i.e. flows from one 'capacity' to another may be influenced by either physical or physiological processes. So, for example, for the state variable 'terrestrial plant biomass', the input flow rate is determined by the intensity of photosynthesis and the movement of water and mineral elements from the roots. The rate of outflow from this “capacity” is associated with the eating of grass by animals, dying off, the outflow of metabolites into the roots, and trampling the grass cover by animals. Each tempo variable is affected by several variable equations and control actions. The rate of photosynthesis, for example, depends on the leaf index of available soil moisture, solar radiation, and air temperature. A person is also considered as a control variable or an external force acting on the flows into or out of the system.[ ...]
Silent evidence of this was a number of collapsed civilizations in the steppe regions. the globe. When a person, at the cost of hard work and hard-earned money, creates an artificial pasture, he will not think of exploiting it until it is completely destroyed, just as it will not come to his mind to burn down his own house. However, as Leopold put it well (see sec.[ ...]
Judging by estimates of biomass and productivity of biomes (Table 3.1), the total biomass of the biosphere (in terms of dry matter) is about 2 trillion tons, the annual production of biomass is 10 times less. The living matter of the biosphere is 99.5% represented by the biomass of terrestrial plants. The total productivity of the biota of the biosphere is characterized in Table. 3.3. The total amount of energy converted by the biota of the biosphere per year exceeds 1022 J. Due to the ability to transform solar energy into the energy of chemical bonds, plants and other organisms perform a number of fundamental biogeochemical functions on a planetary scale.[ ...]
There are terrestrial, marine and freshwater biomes. Each of the terrestrial biomes is characterized by a certain set of vegetation (trees, shrubs, grasses, etc.) with which the animals living in these habitats are associated. Biomes are tundra, coniferous forests, deciduous forests, tropical rainforest, steppe, chaparral, desert.[ ...]
It should be noted that there are many transitional options between the main types of biomes - forest-tundra, forest-steppe, coniferous-deciduous forest, semi-desert, etc. Of particular interest is the savannah - the transition zone between rainforests and deserts.[ ...]
Biome based diversity maps. Ideas about the biome, classification of biomes, biome as a basic unit of biodiversity accounting. Biome types and their mapping. Regional biomes and their mapping. Biome mapping indicators.[ ...]
Animal world: species composition richer than all other biomes combined. Especially numerous are amphibians, reptiles and birds (frogs, lizards, snakes, parrots), monkeys and other small mammals, exotic insects with bright colors, and brightly colored fish in water bodies.[ ...]
Our considerations so far have concerned the individual organism. However, we are interested in whole biomes and ecosystems. It turned out that the concept of a limiting factor is applicable at this level as well. Thus, the annual amount of precipitation is a limiting factor for certain types of vegetation (Fig. 2.13), and temperature, more precisely, the combination of temperature and precipitation, limits the nature of the forest ecosystem (Fig. 2.14).[ ...]
Zonal vegetation - natural climax plant communities characterizing certain biomes and corresponding climatic zones. They form independent vegetation zones(tundra, taiga, coniferous forests, broad-leaved forests, savannas, tropical rainforests, steppes, deserts, etc.). Sometimes the concept of "interzonal vegetation" is also distinguished - phytocenoses that do not form independent zones anywhere, but are found simultaneously in several natural zones (sphagnum bogs, saline communities, willows along rivers, etc.).[ ...]
In Australia the forests are dominated eucalyptus trees and shrubs. Trees are widely introduced in other places of these biomes - in California (USA), in the Colchis Lowland (Georgia).[ ...]
The largest land communities, occupying large areas and characterized by a certain type of vegetation and climate, are called biomes. The type of biome is determined by climate. In different areas of the globe with the same climate, similar types of biomes are found: deserts, steppes, tropical and coniferous forests, tundra, etc. Biomes have a pronounced geographical zonality (Fig. 45, p. 142).[ ...]
Two abiotic factors - temperature and amount of precipitation (rain or snow) - determine the placement of earth's surface the main terrestrial biomes - very large ecosystems (steppe, taiga, tundra, desert, etc.). The regime of temperature and precipitation in a certain area for a sufficiently long period of time is called climate.[ ...]
Ecosystems of a lower order must be territorially balanced within the biosphere. In other words, the Earth should have the required number of tundras, forests, deserts, etc. - as biomes, and inside the tundra biome, optimal tundra should be preserved, inside the coniferous forest biome - optimal forest cover, etc. And so on to the smallest biogeocenoses. [...]
According to Y. Odum (1986), a biome is "a large regional and subcontinental ecosystem characterized by some basic type of vegetation or other characteristic feature of the landscape." The boundaries of the distribution of biomes are determined by the landscape components of the continents, in the name - the dominant vegetation (forest, shrub, etc.). In aquatic ecosystems, plant organisms do not dominate, therefore, physical signs of the habitat (“stagnant”, “flowing” water, open ocean, etc.) are taken as the basis. Yu. Odum proposed a classification of the natural ecosystems of the biosphere on the principles of the biome approach (Fig. 7.2.), which best characterizes the landscape approach in ecology.[ ...]
BIOM - according to Y. Odum (1986, vol. 1, p. 14) “a term denoting a large regional or subcontinental biosystem characterized by some basic type of vegetation or other characteristic feature of the landscape.” The biocenoses that make up the biome are closely interconnected by the flows of energy and substances. To distinguish between terrestrial biomes, in addition to the physical and geographical conditions of the environment, the life form of plants is also used. For example, trees absolutely dominate in humid tropical forests and play a significant role in other forest formations, perennial grasses prevail in the tundra and steppes, and annual grasses in deserts and semi-deserts.[ ...]
The biome includes not only climatic climax vegetation, but also edaphic climaxes and stages of development, in which other life forms dominate in many cases (Ch. 9). Thus, herbaceous communities represent a temporary stage of development in the deciduous forest biome, where the climax life form; are broad-leaved deciduous trees. The biome is identical to the main "plant formation" in the sense in which the term is used in plant ecology; the only difference is that a biome is a unit of an entire community, not just vegetation. The biome includes not only plants, but also animals. In general, it can be said that a biome corresponds to the "main biotic zone", if this expression is understood as a community zone, and not a floristic or faunistic unit. The biome corresponds to the "main zone of life" as understood by European ecologists, but does not correspond to the "zone of life" as understood by American ecologists. In North America, the term "life zone" refers to a series of "temperature zones" described in 1894 by C. Merriam and widely used in the study of birds and mammals. The original temperature criteria have been abandoned, and the distribution of animals is now the basis of Merriam's life zones, so that these zones are increasingly becoming community zones and in many cases the same as parts and subsystems of biomes. For a comparison of the biomes and life zones of Merriam, see Y. Odum (1945).[ ...]
Thus, the biome is broadleaf deciduous forests of the temperate zone in the eastern United States. Prairies and other grasslands in the temperate dry climate of the Midwest and Western United States is also a biome. A biome is a group of terrestrial ecosystems of a given continent that have a similar structure or physiognomy of vegetation and the general nature of environmental conditions, which is reflected in this structure and in the characteristics of their animal population.[ ...]
Similar temperate continental deciduous forests are common in North America, Europe, and East Asia. Temperate grasslands occur in similar climates in North America, Eurasia, and the Southern Hemisphere. Even wider groups of convergent biomes, or formations, of different continents are called biome types, or formation types. These broad categories are so few that they could well be described in this book. The concept of biomes and biome types is justified for terrestrial communities. It can also be extended to aquatic communities, but this seems less natural, since aquatic communities change one into another in a different way and are characterized by less clear dependences of the structure on climate.[ ...]
Wet tropical forests. These forests are located in a number of equatorial regions. They are moderately high average annual temperatures, which change little during the day and seasons, as well as significant humidity and almost daily precipitation. These biomes are dominated by evergreen trees, retaining most of their leaves or needles. all year round, which ensures a continuous year-round flow of photosynthesis processes.[ ...]
The ecosystem is the main functional unit in ecology, since it includes both organisms and the inanimate environment - components that mutually influence each other's properties and are necessary to maintain life in its form that exists on Earth. If we want our society to move towards a holistic solution of problems that arise at the level of biomes and the biosphere, then we must first of all study the ecosystem level of organization.[ ...]
Earlier, we have already said that one of the main difficulties is how to obtain discrete structures on a set of continuously measured parameters. The fact is that the entire plant shell of the Earth is a mosaic of discrete forms. These are biogeocenoses, the boundaries of which, as a rule, are set by the boundaries of phytocenoses, and larger units, such as biomes (for example, taiga or steppe).[ ...]
This community can, however, be considered as a subdivision of the northern coniferous forest biome. Humidity is the limiting factor here; 250-500 mm of unevenly distributed precipitation determine the park appearance of pygmy pine (Pinus edulis, P. monophytla) and junipers (several species of the genus Juniperus), as shown in Fig. 198. This community occupies a wide strip between the desert or steppe and thicker coniferous forests at higher altitudes. Pine cones and juniper berries are an important food source for animals. The jay, great tit and bush tit are characteristic permanent species of sedentary birds; the first two are widespread in this biome. For more on dwarf conifers, see Woodbury (1947) and Hardy (1945).[ ...]
Succession ends with a stage when all species of the ecosystem, while reproducing, retain a relatively constant number and no further change in its composition occurs. Such an equilibrium state is called a climax, and the ecosystem is called a climax. Under different abiotic conditions, different climax ecosystems are formed. In a hot and humid climate it will be a rain forest, in a dry and hot climate it will be a desert. The main biomes of the earth are the climax ecosystems of the respective geographical areas.[ ...]
As in the tundra, seasonal periodicity and fluctuations in the number of populations are expressed here. A classic example is the population cycle of a hare and a lynx (Fig. 88). In coniferous forests, outbreaks of bark beetles and leaf-eating insects are also observed, especially if the stand consists of one or two dominant species. A description of the North American coniferous forest biome can be found in Shelford and Olson (1935).[ ...]
Sometimes "intermediate" ecosystems (according to the hierarchy of subordination) disappear altogether, as well as elementary ones, in their original form. The hierarchy of ecosystems is sharply simplified in terms of the number of levels - only the 2nd from the bottom level of the biome or landscape strip is preserved as a whole (see Chapter 2) and species only correspond to them in terms of distribution, occupying microareas that hardly make up full-fledged ecosystems (rather, their paracelles). [...]
Energy cannot be transferred in closed cycles and reused, but matter can. - Matter (including nutrients) can pass through the community in "loops". - The cycle of nutrients is never perfect. - Exploring the Hubbard Brook forest - Nutrient inputs and outputs are generally low compared to the amounts involved in the cycling, although sulfur is an important exception to this rule (mainly due to "acid rain") - Deforestation breaks the cycling and leads to loss of nutrients .- Terrestrial biomes differ in the distribution of nutrients between dead organic matter and living tissues, - Currents and sedimentation are important factors influencing the flow of nutrients in aquatic ecosystems.[ ...]
The functional structure of the Ministry of Natural Resources of Russia approved to date and the list of tasks of the ministry allow us to speak about the preservation of a predominantly exploitative ideology and the former value orientation, according to which the main wealth of Russia is in its bowels. However, a correct resource assessment, associated with global forecasting models and environmental and economic analysis of the current situation in the world and in our country, indicates something else: the main natural wealth Russia is the assimilation and production potential of its biota, mainly forests, in a significant part of the territory not affected by economic activity. It is they that determine the powerful environment-forming, environment-regulating and environment-purifying function of the biome of northern and northeast Asia, which is of great importance for the entire planet.[ ...]
In the biocenotic series there are no longer individuals and individuals as such. These latter form synusia, which, in turn, break up, and vice versa, aggregate into population consortia. This feature - on the one hand, association, and on the other, separation - is characteristic of many biotic formations. Bio-geocenotic consortia form the same parcels, which in turn integrate into biocenoses, called associations by botanists. Separate biocenoses, combined, add up biocenomic types, the interaction of which forms regional biotas (in botany, usually with the dominance of some kind of plant formation and type of successional processes). The latter compose biomes in a purely biological, rather than ecological-geographical sense (“biobiomes”), as biocenotic formations that have their own evolution, but conditionally considered outside environmental factors.[ ...]
An empirical generalization of all biogeographic regularities relating to ranges and the conditions for the existence of species within them is the rule of geographical optimum: the living conditions of a species are most optimal for it in the center of the range. Obviously, it is assumed that the abiotic and biotic environment is the most favorable here, and the ecological niche has been worked out with the greatest perfection. However, it is often not the spatial-geometric center of the range that is meant, but its ecological "center". For example, for fur seals, many other marine mammals, colonial birds, and any terrestrial species with a disjunctive or other type of discontinuous range, the geometric center of their range is unlikely to be optimal for life. The view may not exist at all. Rather, on the contrary, the ecological optimum forms a part of the area with the highest density of the species population - it has the highest density and total abundance in the most favorable places for the existence of populations of the species. These places can be located both in the depths of the outlined area, and at its geographical boundaries. In its “pure” form, the geographic optimum rule is valid only for species with a vast continuous range, usually occupying all or most of the biome or geographic zone. However, in this case, variants are often possible when some edges of the species distribution area turn out to be the most favorable. For example, many taiga animals (elk, wolf, etc.) are clearly confined not to the deaf middle taiga, but to its so-called subtaiga southern strip. There is more fodder here due to natural causes and due to human disturbance of forests, moreover, it is warmer and, as a rule, the snow cover is less deep.[ ...]
Organisms are constantly changing physically into the chemical nature of the abiotic environment, giving new compounds to the sources. Thus, the composition of sea water in the bottom and fishing is largely determined by the activity of carrot organisms; plants planted on sandy soils completely change the soil over the years and turn them into fertile ones. As a result, the community of organisms in their habitat develops as a single whole, forming a complex system of regulation that maintains favorable conditions for life on Earth. Sometimes a large terrestrial regional or trans-continental ecosystem characterized by some basic type of vegetation and another characteristic feature of the landscape (tundra, tropical forest, deciduous forest, desert, etc.) is referred to as a biome. From an ecological point of view, biomes are equivalent to ocean eco-themes.[ ...]
Palmgren (1949) and Cole (1951 and 1954) suggested that the oscillations, which seem regular to us, may be the result of random changes in the complex of biotic and abiotic environmental conditions in which the population is located; if so, then none of the factors can be considered more important than the others. Keith (1963) made a detailed statistical analysis of cycles in northern birds and mammals and concluded that the decadal cycle was "real" (not random), although it was usually difficult to prove that shorter cycles were not due to random fluctuations. It is shown that the 7-10-year cycle is characteristic, in addition to the hare and lynx, also for the collared hazel grouse, and this cycle in the vast expanse of Canada and the lakeside states occurs synchronously and usually correlates with the hare cycle. Cycles similar in duration were found in prairie grouse, partridge, muskrat, and fox, but in these cases they are more limited in scope and less regular. It is interesting that the gray partridge, introduced into the northern regions of North America, apparently "learned" the 10-year cycle; however, the data on this subject are insufficient, since the duration of acclimatization of the gray partridge is short. At the same time, there is sufficient evidence that the 7-10-year cycle of forest insect pests is typical for Europe.
Characteristics of the main land biomes
- 1. Biome. Vegetation. Flora. Fauna. Animal world
Biome - it is a set of communities of any zone or subzone.
Vegetation - a set of plant communities (phytocenoses) inhabiting any territory. The distribution of vegetation is determined mainly by the general climatic conditions and obeys the laws of latitudinal zonality in the plains and altitudinal zonality in the mountains. At the same time, certain features of azonal and intrazonal features are observed in the geographical distribution of vegetation. The main classification units of vegetation are: "vegetation type", "formation" and "association". The most important ecological groups of plants - trees, shrubs, shrubs, dwarf shrubs and herbs.
Trees- perennial plants with a lignified main stem (trunk) that persists throughout life (from tens to hundreds of years), and branches that form a crown. The height of modern trees ranges from 2 to 100 m, sometimes more. Trees belong mainly to conifers and dicots. Life form - phanerophytes.
shrubs - perennial woody plants with a height of 0.6 - 6 m, which do not have a main trunk in the adult state. The life expectancy of most shrubs is 10 - 20 years. Shrubs are widespread along the border of forests (shrub steppe, forest tundra). In forests, they usually form undergrowth. Are important currant, gooseberry other. Life form - phanerophytes.
Subshrubs - perennial plants in which renewal buds persist for several years, and the upper parts of the shoot are replaced annually. The height of most shrubs is no more than 80 cm. The shrubs grow mainly in arid areas. Their typical representatives are teresken, species of wormwood, astragalus, saltwort and others. Life form - chamefites.
Shrubs - undersized perennials with woody shoots; height 5-60 cm, live 5-10 years. Widespread in the tundra willow species, many heathers), in coniferous forests, in sphagnum bogs ( cranberry, cassandra, wild rosemary), in the highlands, etc. Life form - chamefites.
semishrubs - perennial small shrubs, for example thyme.
Herbs - annual and perennial plants, which are characterized by the absence of upright above-ground stems that experience an unfavorable season. All herbs have renewal buds at the soil level or in the soil (on rhizomes, tubers, bulbs).
Flora, that is, the totality of systematic units (species, genera, families) in a given territory, should be distinguished from vegetation.
Flora can be defined as a historically established set of species of plants, fungi and microorganisms that inhabit a territory or inhabited it in past geological epochs.
Fauna - a set of animal species that live in a certain area. The fauna is formed in the process of evolution from animals of different origin: autochthonous (arising here), allochthonous (originating elsewhere, but settled here long ago), immigrants (introduced here relatively recently). The term "fauna" is also applicable to the totality of animals of any systematic category (for example, bird fauna - avifauna, fish fauna - ichthyofauna, etc.).
Animal world - a set of individuals of various animal species characteristic of a given territory.
Under the influence of climatic factors, zonal features of biomes were formed. Despite the similarity of climates in different meridional sectors of the same zone, communities of different sectors differ in the set of plant and animal species that make up them. All this leads to differences in the structure and dynamics of biomes (4,5,16,23,35,40,46,52)
2. Zonal, intrazonal and extrazonal communities
biome community forest
Any biome has its own specific set of communities. At the same time, in every biome there are 1) zonal communities, 2) intrazonal communities, 3) extrazonal communities.
1 . Zo social communities occupy in any natural zone plakors (well-drained vast plains or watersheds) on soils of medium mechanical composition (on sandy loam and loam). As a rule, zonal communities occupy the largest spaces within a zone.
2 . Ying transzonal communities nowhere do they form "their" zone, but they are found in non-zonal conditions of several neighboring or even all natural zones.
In ecology, the following intrazonal communities are distinguished:
1) intrazonal communities, characteristic of the non-zonal condition of several neighboring zones,
2) azonal, characteristic of non-zonal conditions of all land zones.
However, there is no real difference between these categories. Large biocenotic categories, types of vegetation (for example, meadows, swamps) exist in all or almost all natural zones. The distribution of smaller categories (eg formation class) will be limited to only a few zones. Such, for example, are sphagnum, green moss and papyrus bogs, tall grass and steppe meadows, etc. Intrazonal vegetation and animal populations bear the imprint of the zone with which they are genetically and ecologically related. That is why in zones that lie farther from each other, they are less similar than in neighboring ones.
3 . Ek strazonal communities form zonal communities outside this zone, but, going beyond the boundaries of their “own” zone, they are confined to non-zonal conditions. For example, broad-leaved forests, which form a special independent zone, do not occur in the steppe on watersheds, but descend along the slopes of river valleys and into steppe ravines. In the steppe beams they form the so-called canopy forests. Similarly, to the north of the steppe zone, islands of the steppe may be tied to the slopes of the southern exposure, as is the case in Yakutia and the Magadan region. Finally, along the western slope of the Urals there is a huge forest-steppe island located in the subzone of mixed forests. It has all the signs of a forest-steppe: the presence of birch pegs, steppe areas with John's hoof, thickets of steppe shrubs ( steppe cherry, steppe mindala etc.). This forest-steppe is associated with the outcrop of gypsum and anhydrites, which create favorable conditions for the forest-steppe vegetation and animal population. In all these cases, we are talking about extrazonal communities.
Thus, within any biome there are zonal communities (on plains under zonal conditions), as well as intrazonal and extrazonal communities (under nonzonal conditions). The combination of these three types of communities forms its own unique type of biome.
3. Cold (polar) deserts
Cold polar deserts formed in the cold Arctic climate in the Northern Hemisphere or in the Antarctic climate in the Southern Hemisphere. In the conditions of polar deserts, vegetation does not form a continuous cover. Often, up to 70% of the earth's surface is occupied by gravelly, stony, and sometimes cracked into polygonal soils. The snow here is shallow and is blown away by strong winds, often of a hurricane character. Often, only individual tufts or cushions of plants huddle among stony and gravelly placers; and only in the lower areas do spots of a denser vegetation cover turn green. Plants develop especially well where birds abundantly fertilize the soil with excrement (for example, in places of nesting clusters, the so-called bird colonies).
Within the polar deserts, there are few birds that are not connected with the sea ( snow bunting, Lapland plantain and etc.). Colonial species predominate everywhere. This biome is characterized by bird colonies, in which the leading ecological role is played by auks (chistik, little auk, dead end), seagulls (burgomaster, kittiwake, silverandflock, small polar and etc.), eider(Northern Hemisphere) and penguins, burgomasters, white plovers(Southern Hemisphere). As a rule, bird markets are confined either to cliffs or to areas of soft ground in which some birds dig holes. Penguins, for example, take their young to polar ice and snows.
From mammals, some species penetrate into the polar deserts. lemmings (Ob, hoofed), but their number is still not very large. Plants are predominant mosses and lichens; there are also some flowering (for example , cyanosis squat, polar poppy and etc.). In the pollination of these plants take Active participation insects and especially bumblebees, as well as Diptera (flies, mosquitoes and etc.).
Diptera - This is a detachment of insects in which only the front pair of wings is developed.
AT arctic wilderness the stock of phytomass is about 2.5 - 50 c/ha, and its annual production is less than 10 c/ha.
4. Tundra
Tundra characterized by extremely harsh conditions for the growth of plants and animals. The growing season is short and lasts from 2 to 2.5 months. At this time, the summer Sun does not descend, or only for a short time falls below the horizon line and the polar day is established. That is why long-day plants dominate in the tundra.
There is little precipitation - 200 - 300 mm per year. Strong winds, especially harsh in winter, blow the already shallow snow cover into depressions. Even in summer, nighttime temperatures often drop below 0 0 C. Frosts are possible on almost any summer day. average temperature July does not exceed 10 0 C. Permafrost is located at a shallow depth. 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 soils, forming a continuous stratum. Soils of light mechanical composition thaw in summer to a depth of about one meter or more. In depressions where a lot of snow accumulates, permafrost can be very deep or absent altogether.
The relief of the tundra is not flat, leveled. Elevated flat areas can be distinguished here, commonly referred to as blocks, and interblock depressions, having a diameter of tens of meters. In some areas of the tundra, these low areas are called alas. The surface of blocks and interblock depressions is also not completely flat.
According to the nature of the relief, the tundra is divided into the following types:
1) hilly tundra , which are characterized by hillocks 1 - 1.5 m high and 1 - 3 m wide or manes 3 - 10 m long, alternating with flat hollows;
2) large hilly tundra characterized by a height of hillocks from 3 to 4 m with a diameter of 10 - 15 m. The distance between the hillocks varies from 5 to 20 - 30 m. Large-hilly tundras are developed in the southernmost tundra subzones. The formation of mounds is 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, the upper layers of peat protrude, leading to the formation and gradual growth of hillocks.
3) spotted tundra are developed in the more northern subzones of the tundra and are formed in the winter period of the year as a result of the outpouring of quicksand on the day surface, which leads to the formation of bare spots, between which rare plants huddle. Spotted tundras can also be formed under the influence of strong winds and frosts without quicksand effusions: in the winter period of the year, the soil cracks into polygonal parts, soil particles accumulate in the cracks between them, on which plants settle in the warm season.
The vegetation of the tundra is characterized by the absence of trees and the predominance of lichens and mosses. Of the lichens, fruticose of the genera are plentiful cladonia, centria, stereocaulon and others. These lichens give a small annual increase. For example, annual growth forest cladonia is from 3.7 to 4.7 mm, cladonia slender- 4.8 - 5.2 mm, glomerular cetraria - 5.0 - 6.3 mm, snow cetraria- 2.4 - 5.2 mm, easter stereocaulon- 4.8 mm. That is why the reindeer cannot graze in the same place for a long time and is forced to move in search of food. Reindeer can use the visited pastures only after many years, when its main fodder plants - lichens - grow.
All types of tundra are characterized green mosses. Sphagnum mosses are found only in the more southern areas of the tundra.
The vegetation cover of the tundra is very poor. There are few annuals due to the short growing season and low temperatures in the summer. Only where the vegetation cover is disturbed under the influence of human activity, or where there are emissions from the burrows of animals - inhabitants of the tundra, annuals can develop in significant quantities.
Of the perennials, there are many winter-green forms, which is also associated with the need for a more complete use of the short growing season. In the tundra, there are many shrubs with low, woody trunks and branches creeping along the soil surface, pressed to the earth's surface, as well as herbaceous plants that form a dense turf. Cushion-shaped forms are extremely widespread, which save heat and protect plants from low temperatures. Often the plants have a trellis, elongated shape. Of the winter green shrubs, it should be distinguished partridge grass, cassiopeia, cranberries, crowberries; from shrubs with falling leaves - blueberry, dwarf birch, dwarf willow. Some dwarf willows have only a few leaves on short, squat trunks.
In the tundra, there are almost no plants with underground storage organs (tubers, bulbs, succulent rhizomes) due to low temperatures and deep freezing of the soil.
Tundra - treelessness. Ecologists believe that the main reason for the treelessness of the tundra lies in the objective contradiction that exists between the flow of water into the roots of trees and its evaporation by branches raised above the snow surface. This contradiction is especially clearly revealed in the spring, when the roots cannot yet absorb moisture from the frozen soil, and evaporation by the branches is carried out very intensively. This hypothesis is confirmed by the fact that along the river valleys, where the permafrost goes deep and the winds that increase evaporation are not so strong, the trees penetrate far to the north.
According to the features of the vegetation cover The tundra is subdivided into the following three subzones:
1) arctic tundra : spotted tundra is widespread, there are no closed shrub communities, green mosses predominate, sphagnum mosses are absent;
2) typical tundra: shrub communities dominate, lichen communities are widespread, green mosses dominate, sphagnum mosses are present, forming small peat bogs;
3) southern tundra: sphagnum peatlands are well developed, and forest communities are formed along the river valleys.
In the tundra, the winter and summer seasons stand out more clearly than in any other zone. Seasonal migrations of animals are pronounced here. A vivid example of migration can be the flights of birds leaving the tundra for the winter, and returning here again in the spring.
Seasonal migrations are characteristic and reindeer. So, reindeer for the summer they move to the sea coasts in the more northern regions of the tundra, where the winds to some extent reduce the intensity of the midge attack ( horseflies, mosquitoes, midges, gadflies), tormenting animals with their constant bites. In winter, deer go to more southern regions, where the snow is not so dense and it is easier for them to “hoof” it, getting food. Nomadic reindeer herds constantly accompanies tundra partridge, which, as a result of this, gets the opportunity to use the areas of soil dug up by deer for searching for food. Reindeer migration routes can be very long.
It should be noted that animals, on the one hand, experience the influence of conditions environment On the other hand, by their vital activity they have a powerful impact on the formation of various natural complexes. A striking example of the transformation of the environment by animals is the vital activity of lemmings.
Lemmings - a group of mammals of the subfamily of voles. The body length is up to 15 cm, the tail is up to 2 cm. About 20 species of lemmings are known to live in the forests and tundras of Eurasia and North America. Lemmings are the main food of the arctic fox. They can be carriers of pathogens of a number of viral diseases. In some years they breed en masse and undertake distant migrations.
The amount of food consumed by lemmings is 40 - 50 kg of plant matter per year. On a day, a lemming eats 1.5 times more than it weighs. The burrowing activity of lemmings has a huge ecological impact on tundra life. The number of lemming holes ranges from 400 to 10,000 per 1 ha, which significantly increases soil aeration. Lemmings “throw out” on the day surface up to 400 kg of soil per 1 ha. These emissions intensively develop plant species such as daisy core, krupka, fescue, arctic fireweed, rush etc. Lushly developed vegetation on these ejecta creates the impression of miniature oases.
The rhythms of nature are associated with mass breeding of lemmings, which occur once every three years.
Another striking example of the impact of animals on the habitat is the burrowing activity of ground squirrels. Long-tailed ground squirrel, for example, promotes the creation of forb-meadow communities on well-drained soils and wastes.
Geese and other waterfowl also contribute to the occurrence of vegetation changes in the tundra: after plucking grass, patches of bare soil form. In the future, increased aeration leads to the development of sedge-cotton grass, and then sedge-moss tundra.
In the tundra, self-pollination of plants and wind-assisted pollination are widespread; entomophilia is poorly developed. Insects rarely visit flowers. For example, in tundra conditions, perhaps only bumblebees are the only pollinator of plants with irregular flowers - Astragalus, Ostrolodochnikov, Mytnikov.
Many flowers of tundra plants have a very short lifespan. Yes, at cloudberries, covering the vast expanses 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 the flight of insects, then the chances of pollination with the help of insects fall. Many insects hide in flowers not in search of nectar, but seek refuge here from adverse weather conditions. And this means that they can sit in one flower for a long time, and then fly to a flower of another species, which also reduces the chances of plants for pollination by insects.
Soil inhabitants in the tundra are not numerous and are concentrated in the upper soil horizons (mainly in the peat horizon). With depth number soil inhabitants decreases rapidly, as the soil is saturated with moisture or is frozen.
Many northern birds are characterized by large clutch sizes and, accordingly, large broods compared with individuals of the same species living in more southern zones. This can be attributed to the abundance of insects that serve as food for birds. The growth of young animals in the tundra is faster than in the south.
Many people incorrectly believe that with a high duration of the illuminated period of the day, birds feed their young for a longer time. However, it should be noted that even where the day is around the clock, birds still sleep for a significant part of the astronomical night. In all types of tundra, there are few reptiles and amphibians due to permafrost.
The phytomass in the arctic tundra is very small and amounts to about 50 c/ha, in the shrub tundra it increases to 280-500 c/ha.
5. Forest tundra
forest tundra - natural area Northern hemisphere, transitional between the forest zone of the temperate zone and the tundra zone. In the natural landscapes of the forest-tundra zone, there is a complex complex of light forests, tundra, swamps and meadows.
Ecologists sometimes consider the forest-tundra a transition zone and often consider it as a tundra subzone. However, this is a special zone, the biocenoses of which differ from both tundra and forest ones.
The forest-tundra is characterized woodlands . Birds appear here in a significant number, nesting among the bushes, for example, bluethroat. In the forest-tundra, the amount of seed food increases, which leads to an increase in the number and diversity of mice. The permafrost goes deeper. K rarely standing trees there are nests of corvids and small birds of prey. The forest-tundra has a special set of conditions for existence, both in comparison with the tundra and in comparison with the forest. It is characterized by such types of trees as berefor, spruce(in the West), larch(in the east).
6. Coniferous forests of the temperate zone (taiga)
Taiga - type of vegetation with a predominance of coniferous forests. Taiga forests are common in the temperate zone of Eurasia and North America. In the forest stand of the taiga, the main role is played by spruce, pine, larch, fir; the undergrowth is poor, the herbaceous-shrub layer is monotonous ( blueberries, lingonberries, sour, green mosses).
Taiga communities are typical only for the temperate zone of the Northern Hemisphere. They are absent in the southern hemisphere.
Taiga forests can be formed either by dark coniferous species - spruce, fir, Siberian cedar pine (Siberian cedar), or light coniferous - larch, as well as pine(mainly on soils of light mechanical composition and sands).
In the taiga, the warmest month has a temperature from +10 0 C to +19 0 C, and the coldest month - from -9 0 C to -52 0 C. The cold pole of the Northern Hemisphere lies within this particular zone. The duration of the period with average monthly temperatures above 10 0 C is short. There are 1 - 4 such months. The growing season is quite short. According to ecological features and floristic composition, communities of dark coniferous and light coniferous taiga forests are distinguished.
Communities of dark coniferous forests (spruce, fir, cedar) are quite simple in structure: the number of tiers is usually 2-3. Here are the following tiers:
tree layer;
herbaceous or grass-shrub layer;
moss layer.
In dead-cover forests, there is only one (tree) layer, and grass (grass-shrub), moss layers are absent. Shrubs are solitary and do not form a pronounced layer. All dead cover forests are characterized by significant shading. In this regard, grasses and shrubs reproduce more often vegetatively than by seeds, forming clumps.
Forest litter in dark coniferous forests decomposes very slowly. Winter-green plants are widely represented ( lingonberry, pear). Lighting, in contrast to broadleaf forests, is the same throughout the growing season. Therefore, there are practically no plants timing the development of flowers for the early spring months. The corollas of flowers of plants of the lower tier have white or pale colored tones, clearly visible against the dark green background of the moss cover and in the dusk of a dark coniferous forest. In the untouched dark coniferous forest, air currents are very weak, there are practically no winds. Therefore, the seeds of a number of plants of the lower tier have an insignificant weight, which allows them to be transported from place to place even by very weak air currents. For example, seeds Wintergreen single color(seed weight - 0, 000 004 g) and goodyear orchids(seed weight - 0,000,002 g).
How can an embryo developing from seeds of such an insignificant weight be fed? It turns out that the development of plant embryos with such tiny seeds requires the participation of fungi, i.e. mycorrhiza development.
Mycorrhiza (from Greek. mykes- mushroom and rhiza- root, i.e. mushroom root) - mutually beneficial cohabitation (symbiosis) of the mycelium of the fungus with the root of a higher plant, for example, boletus with aspen, boletus with birch). Mitz e liy (mushroom) - the vegetative body of fungi, consisting of the thinnest branching threads - hyphae.
The hyphae of the fungus, which are extremely abundant in dark coniferous forests, grow together with the embryos developing from such seeds and supply them with the necessary nutrients, and then, when the embryo grows and gets stronger, it, in turn, provides the fungus with photosynthesis products - carbohydrates. The phenomenon of mycorrhiza (symbiosis of a higher plant and a fungus) is very widely developed in forests in general, and is especially common in dark coniferous taiga forests.
Mycorrhiza (fungal root) is formed not only by flowering plants, but also by many trees. The fruit bodies of many fungi that form mycorrhiza are edible for humans and animals. These are, for example, porcini mushroom, russula, boletus growing under pine and larch, boletus and boletus associated with small-leaved trees developing on the site of reduced dark coniferous forests, etc.
An important role in the distribution of seeds is played by animals that eat the juicy pulp of the fruits of taiga plants. It should be noted that eating such juicy fruits by animals is a condition for high germination of their seeds for a number of plant species. At blueberries and cranberries for example, the high acidity of berry juice prevents seed development in an intact berry. If the berry is crushed by the paws of the beast or digested in its stomach, then the surviving seeds germinate quite well. High germination and good seed development are also facilitated by excrement ejected from the intestines with seeds. In this case, the excrement serves as fertilizer for the developing seedlings. Thrushes, for example, successfully disperse seeds mountain ash and many other wild berries, and the Bears- seeds raspberries, mountain ash, viburnum, currants etc.
Ant dispersal is a characteristic method of seed dispersal in dark coniferous forests. Some species of taiga plants have seeds equipped with special fleshy appendages (caruncles) that make them attractive to the inhabitants of the dark coniferous forest.
In the dark coniferous taiga, there is often a moss cover; it is very moisture-absorbing and, being wet, becomes heat-conducting. Therefore, the soils of dark coniferous forests can freeze heavily in winter. The species composition of the forest stand, as well as the grass-shrub layer, is especially poor in the taiga of Europe and Western Siberia, richer - in Eastern Siberia and the Far East, and relatively rich in North America, where there are several species of the same genera of dark coniferous species as in Eurasia ( spruce, fir). In addition, North America has a large presence hemlock and pseudo-hemlock, absent in Eurasia. In the grass-shrub layer of the North American taiga, there are many forms close to Eurasian ones - sour, weekly and etc.
The dark coniferous taiga, like other types of forest, has a number of features that determine the nature of the animal population. In the taiga, as in other forests, there are few gregarious land animals. Meet boars, come in winter reindeer and wolves. This is due to the fact that the presence of a forest stand makes it difficult for animals to visually alert each other about impending danger. Among the birds of prey are especially characteristic hawks which are well adapted to the conditions of life in the taiga. Hawks have relatively short wings and a long tail. This contributes to their quick maneuvering among the branches of trees and a sudden attack on the victim.
AT taiga forest relatively few excavators, because the presence of numerous shelters in the form of hollows, fallen trunks, depressions in the earth's surface relieves animals of the need to dig complex systems of holes.
The differences in the winter and summer composition of the animal population in the dark coniferous taiga are less pronounced than in the tundra and forest tundra. In winter, many herbivorous species feed not on herbaceous and shrubby plants, but on twigs: for example, moose, hare and etc.
The animal population as a whole is relatively poor, both qualitatively and quantitatively. A number of species that live mainly on trees feed on the earth's surface. These are, for example, forest pipit, thrushes and a number of other birds. Others, on the contrary, nest on the soil surface, and feed mainly in the crowns of conifers: black grouse, hazel grouse, capercaillie.
In coniferous forests, seed fodder, in particular coniferous seeds, is of great importance. They give high yields not annually, but once every 3-5 years. Therefore, the number of consumers of these feeds ( squirrel, chipmunk, mouse-like rodents) does not remain at the same level, but has its own rhythms associated with harvest years. As a rule, the next year after a high yield of seeds, there is a sharp increase in the number of individuals of those animal species that feed on these seeds. During the years of starvation, many inhabitants (for example, squirrel) make migrations to the west, during which they swim across major rivers(Yenisei, Ob, Kama, etc.) and thus expand their habitats.
In addition to seed feed, berry and branch feed, as well as needles and wood, are of great importance for taiga animals.
For some animals, needles are an indispensable food; for example, for gypsy moth, producing a real devastation of forests over large areas.
In the dark coniferous taiga are very numerous primary(attacking healthy trees) and secondary(attacking weakened trees) wood pests - barbel beetles and their larvae, bark beetles and etc.
Many species of mammals and birds that feed on trees are well adapted to climbing and often live in trees. These are squirrels and chipmunks from mammals, nuthatch, pikas, woodpeckers from birds. In the diet of birds and other animals that climb trees and nest in hollows, big role insects that feed on seeds and wood play coniferous trees. Good for climbing trees lynx, somewhat worse - Brown bear.
Of the terrestrial mammals of the taiga, the following are most characteristic: Elk from ungulates, bank voles from rodents, shrews from insectivores.
A number of forest dwellers connect tree communities with grass communities. So, herons nest on trees in the forest, and feed along the banks of rivers, lakes or in meadows.
The amplitude of fluctuations in the number of rodents in taiga forests is not as significant as in the tundra, which is associated with a less severe climate and with the protective role of taiga massifs, in which the direct impact of climate on animals is somewhat mitigated.
Communities of light coniferous forests (pine, larch) in Europe are represented mainly oby pinetonovena and are confined mainly to soils of light mechanical composition. In Siberia and North America, primary light coniferous forests can also be associated with soils of a heavier mechanical composition. Here, various types of larches play a large role in them, and in North America, pines. In North America, pines reach their exceptional diversity.
An important feature of light-coniferous forests is a sparse stand associated with an increased light-loving nature of larches and pines. Therefore, in the soil cover of light coniferous forests, they acquire a significant ecological role. lichens and a highly developed shrub layer formed by rhododendrons, rakitnandlump, viburnum, rosehip, currant and others. In North America, light coniferous forests are often found bebark fir, pseudo-hemlock and a number of other breeds.
The biomass within the taiga varies markedly depending on the type of forest, increasing from the forests of the northern taiga to the forests of the southern. In the pine forests of the northern taiga, it is 800 - 1000 centners / ha, the middle taiga - 2600 centners / ha, the southern taiga - about 2800 centners / ha. In the spruce forests of the southern taiga, biomass reaches 3,330 q/ha.
7. Broad-leaved forests
broadleaf forests temperate zone grow in a milder climate than coniferous forests. Unlike conifers, with the exception of larches, broad-leaved trees drop their leaves for the winter period of the year. It is very light in early spring in broad-leaved forests, as the trees are not yet covered with leaves. Illumination is the main factor in the formation of layering.
In broad-leaved forests, abundant fallen leaves cover the soil surface with a thick loose layer. Under such litter, the moss cover develops very poorly. Loose litter protects the soil from a sharp drop in temperature and, consequently, winter freezing of the soil is either completely absent or very insignificant.
In this regard, a number of species of herbaceous plants begin to develop even in winter, as the thickness of the snow cover decreases and the temperature of the air and the earth's surface rises.
In deciduous forests, a group of spring ephemeroids appears, which, having finished flowering in early spring, then either vegetate or lose their aboveground organs ( oak anemone, goose onion and etc.). The buds of these plants often develop in autumn, with the buds the plants go under the snow, and in early spring, even under the snow, flowers begin to develop.
Anemone (anemone) - a genus of rhizomatous herbs (occasionally subshrubs) of the buttercup family. In total, about 150 species are known, growing all over the globe. Many types of anemone are early spring plants (for example, oak anemone).
A powerful litter allows a variety of invertebrates to overwinter. So soil fauna broad-leaved forests are richer than coniferous ones. In deciduous forests, animals such as mole feeding on earthworms, insect larvae and other invertebrates.
The longline structure of deciduous forests is more complex than that of taiga forests. They usually stand out from one ( dead-covering buchins) up to 3 - 5 tiers ( oak forests). The moss cover in deciduous forests is poorly developed due to thick litter. All single-story broad-leaved forests are dead cover.
Most of the herbaceous plants of the deciduous forest belong to broad oak grass. Plants of this ecological group have wide and delicate leaf blades and are shade-loving.
In the broad-leaved forests of Eurasia, there are many seed-eaters, among which various types of mice are especially diverse: wood mouse, yellow-throated mouse, Asiatic mouse and others. In North American forests, mice are replaced by hamsters having the appearance of mice, as well as representatives primitive jerboas which are good at climbing trees. Like all mice, they feed not only on plant foods (mainly seeds), but also on small invertebrates.
Broad-leaved forests do not form a continuous band covering the Northern Hemisphere. Significant tracts of broad-leaved forests are found in Western Europe, in the foothills of the Kuznetsk Alatau, where they form a continuous island of linden forests, in the Far East, etc. Significant areas of broad-leaved forests are also found in North America.
Broad-leaved forests are heterogeneous in floristic composition. So, in the west of Europe, in areas of mild climate, there are broad-leaved forests dominated by present chestnut and with admixture forest beech. Farther to the east, very shady beech forests dominate with a single layer of tree stand. Further to the east, without crossing the Urals, oak forests predominate.
In the northeastern part of North America, there are forests dominated by American beech and SakhaRmaple. They are less shady than European beech forests. In autumn, the foliage of North American broadleaf forests turns to various shades of reds and yellows. In these forests there are several types of vines - ampelopsis known as "wild grapes".
Maple - genus of trees and shrubs of the maple family. In total, about 150 species are known, growing in North and Central America, Eurasia and North Africa. Maples grow in deciduous and mixed forests. Norway maple, Tatar maple, field maple, sycamore and other species are used in protective afforestation and for landscaping purposes. Maple wood is used for the production of furniture, musical instruments, etc.
Oak forests in North America occupy the more continental regions of the Atlantic states. Several species are found in North American oak forests. oak, many kinds maple, lapina (hickory), tulip derevo from the magnolia family, plentiful creepers.
Hickory (hazel ) - family tree genus walnut. The height of some species reaches 65 m. In total, about 20 species are known, growing in North America and East Asia (China). In many countries, some types of hickory are cultivated as ornamental plants and used in shelter afforestation. nuts pecan and other types of hickory are edible and contain up to 70% edible oil.
Broad-leaved forests are especially rich in species. Far East. There are many types of broad-leaved tree species here: oak, walnut, maple, as well as representatives of genera that are absent in European broadleaf forests, for example, maakia, aralia other. The rich undergrowth includes honeysuckle, lilac, rhododendron, privet, mock orange and others. Abundant, especially in more southern regions, creepers ( actinidia etc.) and other epiphytes.
Aralia - genus of plant family Araliaceae. There are trees, shrubs and tall perennial grasses. Only about 35 species are known, growing in the tropics and subtropics of the Northern Hemisphere. Many species are cultivated as ornamental plants.
In the Southern Hemisphere (Patagonia, Tierra del Fuego), broad-leaved forests are formed southern beech. The undergrowth of these forests contains many evergreen forms, for example, species barberry.
The biomass of broad-leaved forests is about 5,000 kg/ha.
8 . forest-steppe
forest-steppe - This is a natural zone of temperate and subtropical zones, in the natural landscapes of which steppe and forest areas alternate.
The forest-steppe zone is rather peculiar and is characterized by a combination of small forests with vast grassy or shrubby steppe spaces. In Eurasia, the forest areas of this zone are represented by small oak forests, as well as birch and aspen groves. The combination of forest and herbaceous or shrub formations favors the existence of a number of species that are not very characteristic of both the steppe and the forest.
Typical examples of forest-steppe species are rooks, for which the pegs serve as nesting places, and the steppe areas serve as feeding places, as well as numerous falcons (falcon, derbnik), cuckoo and other types.
9. Steppe
Steppes - vast expanses of the temperate zone, occupied by more or less xerophilous vegetation. The steppe zone is represented in Eurasia typical steppes , in North America - prairies , In South America - pampas , in New Zealand - communities Tussocks .
From the point of view of the conditions for the existence of the animal population, the steppes are characterized by the following main features:
good overview of the area;
an abundance of plant foods;
relatively dry summer period;
Existence summer period rest (half rest).
The steppes are dominated everywhere cereals, the stems of which are crowded into sods. In New Zealand, such sods are called Tussocks. Tussocks are very tall, their leaves are quite juicy, which is explained by the mild and humid climate.
In addition to cereals (monocotyledons), dicotyledonous plants are also widely represented in the steppes, which make up an ecological group. "forbs" .
The following two stand out groups of steppe herbs:
1) northern colorful forbs;
2) southern colorless forbs.
Northern colorful forbs are characterized by bright flowers or inflorescences; and for the southern colorless forbs - pubescent stems, narrow leaves, finely dissected and soft flowers.
For the steppes, annual ephemera and perennial ephemeroids are very characteristic, preserving tubers, bulbs and underground rhizomes after the death of the above-ground parts.
Ephemera - annual plants, the full development cycle of which occurs in a very short time (several weeks). Ephemera are characteristic of steppes, semi-deserts and deserts. Typical representatives ephemera are dimorphic quinoa, desert beetroot, sickle-shaped hornhead, some types cereals and legumes.
Ephemeroids - perennial plants, the above-ground organs of which live for several weeks, then die off, and the underground organs (bulbs, tubers) remain for several years. Ephemeroids are characteristic of steppes, semi-deserts and deserts. Typical examples of ephemeroids are the following: swollen sedge, praboutSiberian fishing line, May lily of the valley, oak anemone, bulbous bluegrass, Corydalis, tulips, sedges and etc.
In the steppe zone there are various shrubs: spirea, caragana, steppe cherry, steppe almond, some types juniper. The fruits of many shrubs are readily eaten by animals.
For steppe animals, a burrowing lifestyle is very characteristic, which is the result of an arid climate and the lack of reliable natural shelters. There are many excavators and burrowers in the steppe: mole rats, ground squirrels, marmots, voles, hamsters, prairie dogs. Animals that do not make holes often lead a herd life and play an important role in the life of steppe biocenoses (for example, saiga). Without moderate grazing, in which animals break up accumulations of dead grass on the soil surface with their hooves, typical steppe plants degrade and are replaced by various annual and biennial weed species - thistle, thistle other.
Overgrazing also leads to the degradation of steppe vegetation, to the change of large-turf grasses ( feather grass) small-tufted cereals ( fescue, thin-legged etc.), and with further strengthening - to the emergence of the so-called talk , where steppe perennials almost disappear and are dominated by bulbous bluegrass , breeding mainly vegetatively, as well as annuals. In addition, during overgrazing, desertification of the steppes occurs and less xerophilous plants are replaced by wormwood and other species characteristic of deserts and semi-deserts.
Fires are an important ecological factor in the development of steppe biomes, as a result of which most of the above-ground grasses die. The height of the flame in the steppe fires can reach two to three meters. However, after a fire, the soil is enriched with valuable nutrients and the grass grows quickly. The biomass of steppe vegetation is approximately 2,500 c/ha, which is significantly lower than the biomass of temperate broadleaf forests.
10. Semi-deserts
Semi-deserts are natural zones of the temperate, subtropical and tropical zones with a predominance of semi-deserts. Semi-deserts are dominated by areas with sparse vegetation, which is dominated by grasses and wormwood (in Eurasia) or communities of perennial grasses and shrubs (on other continents).
The main feature of semi-desert biomes is that they are characterized by the complexity of the vegetation cover, which differs significantly from both the steppes and all other natural zones. Of the cereal communities, the semi-desert is most characterized by phytocenoses dominated by Sarepta feather grass. The semi-desert represents the optimal conditions for the existence of many species of animals, for example, the small ground squirrel, black ground squirrel, etc.
11. Deserts
Desert - a type of vegetation with a very sparse vegetation cover in conditions of extreme aridity and continental climate. Typical desert plants are ephedra, saxaul, saltwort, cacti, kendyr.
ephedra - genus of evergreen plants of the ephedra family. About 45 species are known to grow in the temperate and subtropical zones of the Northern Hemisphere. Contain alkaloids (ephedrine, etc.).
Saxaul a genus of woody or shrubby plants of the family haze. The height of some species reaches 12 m. In total, about 10 species are known to grow in the semi-deserts and deserts of Asia. Wood goes to fuel; green branches are food for camels and sheep. Saxaul is a good sand binder.
There are many ephemera and ephemeroids in deserts. The fauna of the deserts is presented antelopes, toatlans, jerboas, ground squirrels, gerbils, lizards, varied insects and etc.
Kulan - equine animal of the equine genus. The length is about 2 m. It lives in the deserts and semi-deserts of Western, Central and Central Asia. The number of kulan individuals is sharply reduced. In some countries, the kulan is under protection.
jerboas (jerboas ) - family of mammals of the rodent order. Body length 5.5 - 25 cm; the tail is longer than the body. Only about 30 species are known to inhabit the open landscapes of the Northern Hemisphere.
There are various types of deserts on the globe. Deserts can vary in temperature and thermal regimes. 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.
Extremely insufficient moisture is characteristic of all types of deserts. Annual precipitation in deserts usually does not exceed 200 mm. The nature of the precipitation regime is different. In the deserts of the Mediterranean type, winter precipitation prevails, and in the deserts of the continental type, a significant proportion of precipitation occurs in the summer. However, in any case, the potential evaporation is many times greater than the annual precipitation and amounts to 900-1500 mm per year.
The main soils of the deserts of the temperate zone are gray soils and light brown soils, which, as a rule, are 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 fundamental importance in characterizing deserts. Therefore, deserts, unlike other communities, are usually subdivided not according to the nature of the vegetation cover, but according to the dominant soils. In this regard, the following four types of deserts are distinguished:
1) clay;
2) salty (saline);
3) sandy;
4) stony.
Desert plants are highly adaptable to arid conditions. Everywhere in the deserts prevail dwarf shrubs, which are often dormant in summer. Plants adapt to living in arid conditions in a variety of ways.
Among the inhabitants of the deserts, especially the deserts of the tropical zone, there are many succulents, among which there are tree forms (for example, saxauls with scaly succulent leaves, etc.).
There are also shrubs devoid or almost devoid of foliage ( Eremospartons, Calligonatwe and etc.). In deserts, plants are widely represented, drying up during the absence of rains, and then reviving again. Lots of downy plants.
Ephemera use the period when deserts are wetter. In continental deserts with little winter precipitation, ephemera develop after occasional heavy summer rains. In deserts of the Mediterranean type, in which a certain amount of snow accumulates by spring, ephemera (ephemeroids) develop mainly in early spring.
In deserts, the vegetation cover never closes with its above-ground parts. Plants of sandy deserts are characterized by the following features:
The ability to give adventitious roots when filling the bases of the trunks with sand,
The ability of root systems not to die off when they are exposed as a result of winding sand,
leafless perennials,
The presence of long (sometimes up to 18 m) roots reaching the groundwater level.
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 many cereals and sedge.
Desert animals have also adapted to life in conditions of insufficient moisture. Burrowing lifestyle - characteristic desert dwellers. In burrows for the hot time of the day, when life on the soil surface practically freezes, they climb beetles, tarantulas, scorpions, wood lice, lizards, snakes and many other animals. The insignificant protective role of vegetation and its small fodder qualities are essential features of the living conditions of animals in deserts. Only such fast moving animals as antelopes from mammals and grouse of 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 or singly.
The conditions for the existence of animals in sandy deserts are peculiar. The friability 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 along the substrate by the development of hairs and bristles on the paws. The development of these adaptations in mammals is important not so much when running on sand as 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 burrowing in denser areas directly at the base of plant stems.
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Rice. 3.4.1. Distribution of some terrestrial biomes according to rainfall and temperature
Biomes have a certain integrity. For example, between the zones of deciduous forests and steppes, there is a forest-steppe zone, where forest and steppe biomes “meet”. Under the existing climate on the territory of the forest-steppe, both types of biogeocenoses can be stable. The forest requires more water than the steppe, but the forest soil holds it more efficiently than the steppe. Where a forest already exists, enough moisture is retained in the soil for the existence of a forest. Where the steppe is located, there is not enough water for the development of the forest. When the humidity or temperature of the climate changes, the border between the forest and the steppe gradually moves. The arid forest is replaced by the steppe, the humid steppe is overgrown with forest. Nevertheless, there remains a wide band where two types of ecosystems alternate in a mosaic pattern. Near-water areas, gullies, lowlands turn out to be forested, and areas with sandy soil, well-heated slopes - steppe. The characteristic type of vegetation depends on and influences the soil and climate, and also determines almost the entire composition of the community that develops in one place or another.
How to reflect the relationship of different types of communities relative to each other? There are two main methods - ordination(i.e. location in some space in a certain order) and classification(i.e. distribution into separate groups - classes or taxa). Ordination emphasizes the continuity of changes in properties, classification emphasizes the discreteness of discontinuities. An example of community ordination is shown in fig. 3.4.1., an example of a multi-level hierarchical classification of yoms is given below.
The main biomes on Earth are as follows.
Terrestrial biomes
Tundra. The biome has a cold humid climate, which is characterized by negative average annual temperatures, rainfall of about 200-300 mm per year and, most often, the presence of a layer of permafrost. There are arctic tundra, located in high latitudes, and alpine tundra, located in the highlands. Vegetation - undersized perennials: lichens, mosses, grasses and shrubs.
Taiga. Cold climate forest biome with long snowy winters and rainfall in excess of evaporation. The main forest-forming species are conifers, the species diversity of trees is low (1-2 dominant species).
deciduous forest. Temperate forest. It develops in regions with moderately warm summers and relatively mild winters with frosts. Characterized by a uniform distribution of precipitation, the absence of droughts, the excess of precipitation over evaporation. In autumn, as the length of daylight hours decreases, leaf fall occurs. Deciduous forests are relatively rich in species and are characterized by a complex vertical structure (presence of several tiers).
Steppe. An area of herbaceous vegetation in a semi-arid temperate zone. The most numerous herbs are grasses and sedges, many of which form a dense turf. Potential evaporation exceeds precipitation. Soils rich in organic matter are characteristic - steppe chernozems. Synonyms - prairie, pampa, veld.
Savannah. Tropical grass-tree communities that develop in areas with a stable alternation of dry and wet seasons. Individual trees or bushes are scattered between open grassy areas.
Desert. A fairly diverse group of biomes located in areas with extremely arid climates or, in the case of an arctic or alpine desert, extremely low temperatures. Sandy, rocky, clayey, saline, icy and other deserts are known. Typically (with the exception of ice deserts, which develop in very cold conditions) either an average annual rainfall of less than 25 mm, or conditions that provide very rapid evaporation of moisture.
Chaparral. Hard-leaved shrubland in a Mediterranean climate with mild, rainy winters and dry summers. It is characterized by a significant accumulation of dry wood, leading to periodic fires.
seasonal rainforest. It is distributed in areas with a hot climate and an abundance of precipitation, in which precipitation is unevenly distributed throughout the year, with a dry season. Extremely rich in species.
evergreen rainforest. The richest biome, located in regions with high rainfall (>2000) and almost constant temperature (about 26°C). In these forests, 4/5 of all plant species of the Earth are concentrated, woody vegetation predominates.
Freshwater biomes
Lentic (stagnant) waters. Puddles, oxbow lakes, natural and artificial ponds, lakes and reservoirs. Living conditions are determined primarily by the depth (and illumination) and the amount of nutrients. The exchange of nutrients and gases between surface and depth is often difficult.
Lotic (flowing) waters. Streams, streams and rivers. The conditions are very dependent on the speed of the current. They are able to move significant amounts of water and other inorganic and organic substances, and are closely connected with the surrounding terrestrial systems.
swamps. Reservoirs with a large amount of organic matter, the destruction of which is slowed down due to a lack of oxygen in the water; mainly characteristic of temperate and moderately cold climates.
Marine biomes
Pelagial. Open ocean and sea depths away from the coast. Producers (first of all, phytoplankton) are concentrated in a relatively thin near-surface layer of water, where light penetrates. Characteristic is the continuous lowering of biogens from the surface to the depth.
continental shelf. Coastal zone of the seas and oceans, reaching to a depth of approximately 200 m. Rich in species and diverse marine communities. The most diverse aquatic ecosystems are characteristic of coral reefs, also belonging to the continental shelf. "Hot spots" of biodiversity are also characteristic of great depths - for example, for places where volcanic gases enter the sea water ("black smokers" and other phenomena).
Upwelling zones. Relatively small areas of the ocean, where the rise to the surface of deep waters enriched in nutrients. They have an exceptional impact on the productivity of the entire ocean as a whole.
Estuaries. Mixing zones of river and sea waters, formed in the seas opposite the mouths of large rivers. They are characterized by a significant amount of organic matter that is carried into the sea by rivers, and constant fluctuations in salinity.
Odum defines a biome as a large regional or subcontinental ecosystem characterized by a major vegetation type or other characteristic feature of the landscape, such as a temperate deciduous forest biome.
Biome- this is a natural zone or area with certain climatic conditions and a corresponding set of dominant plant and animal species (living population) that make up a geographical unity. To distinguish between terrestrial biomes, in addition to the physical and geographical conditions of the environment, combinations of the life forms of plants that make them up are used. For example, in forest biomes, the dominant role belongs to trees, in the tundra - to perennial grasses, in the desert - to annual grasses, xerophytes and succulents.
Natural factors that have been operating for many millions of years have led to the formation of various biogeographic regions on our planet. Scientists distinguish six such regions: the Nearctic, Palearctic, Eastern, Neotropical, Ethiopian and Australian regions. Some of them sometimes capture several continents and are characterized by a certain complex of biomes (from Greek bios - life and Latin ota - totality), making their specific contribution to the Earth's biosphere.
There are a number of major land biomes; the names of most of them are determined by the type of vegetation, for example, coniferous or deciduous forests, desert, tropical forest, etc. Ultimately, however, the biome type is determined by the climate, since the nature of the environment is determined mainly by temperature, precipitation, and the direction and strength of the winds. So, for example, in both the northern and southern hemispheres in areas lying in the equatorial belt, the winds mainly blow in the direction of the equator. They carry moisture with them, which falls in the form of heavy rains in the tropical zone; the result is tropical forests. However, both north and south of the tropics, the same winds are the cause of the formation of savannas and deserts. Farther from the equator, alternating winds from the subtropical and polar zones create a complex sequence of precipitation in different areas, which leads to the formation of steppes and temperate forests. Proximity to the ocean influences the distribution of precipitation and hence the distribution of vegetation types.
The same biomes are found all over the globe, on different continents, in different parts of the world. However, forests, steppes, etc. have their characteristics in various regions of the planet. The animals that have adapted to existence in these biomes are also different. Nearctic region
The Nearctic region includes the territory of all of North America, Newfoundland and Greenland. In the north, snow and ice give way to tundra, and then to a wide belt of coniferous forests. Further south is an array of temperate forests in the east, prairies in the central part, and a mixture of mountains, deserts and coniferous forests in the west. The main biomes are as follows.
Tundra. Low vegetation: mosses, lichens, sedge, stunted shrubs. Main animals: deer, musk ox, leming, polar hare, arctic fox, wolf, white polar bear, snowy owl.
coniferous forests. Mostly dense forests of fir, spruce and other coniferous trees. Main animals: elk, deer, porcupine, vole, shrews, wolverine, lynx, woodpeckers, American hazel grouse.
Steppes. Various combinations of herbaceous and shrubby vegetation. Main animals: bison, antelope, wild rabbit, American badger, red fox, coyote, prairie grouse, large number rattlesnakes.
Deciduous forests. Broad-leaved forests with a dense crown: oak, beech, maple; lots of flowers. Main animals: mole, gopher, black squirrel, raccoon, opossum, chipmunk, red fox, black bear, songbirds.
Hardwood forests. Thickets of juniper and shrubs with leathery leaves. Representatives of the fauna come from neighboring biomes.
desert. Of the plants, cacti, tree-like yucca, wormwood and shrubs are widespread. Main animals: wild rabbit, gopher, cactus mouse, pocket mouse, kangaroo rat and others.
Palearctic region
The Palearctic region includes all of Eurasia from the British Isles in the west to Bering Strait in the east and India and Indochina in the south. Just as in the Nearctic, zones stretch along the entire Palearctic eternal ice, tundra and coniferous forests. Temperate areas in China and Japan, as well as in Europe, are covered with deciduous forests, but the species composition of Asian forests is richer. The central regions of Asia are arid and treeless. The animals of the north of the Palearctic are closely related to the Nearctic, and in the south there are forms characteristic of the Eastern Region.
Tundra. In the tundra, both flora and fauna do not differ significantly from the inhabitants of this zone in the non-Arctic region.
Coniferous forests. The tree species that make up these forests - pine, fir, spruce - belong to the same genera as the corresponding trees of the Nearctic, but are different species from them. The same applies to animals - lynx, wolverine, elk. Herbs are about the same as in the Nearctic. Typical animals: saiga and antelope, wild donkeys, horse and camel, as well as ground squirrel, hamster, jerboa, martens, jackal.
Deciduous forests. Mostly beech, maple, oak, hornbeam, linden, but of different species than in the Nearctic. The fauna of the deciduous forests is also very similar to the Nearctic.
The Mediterranean area is very similar to the corresponding Nearctic biome, which is home to animals from various neighboring communities.
Deserts. Scattered bushes of wormwood, palm grass, thickets of camel thorn, saxaul and tamarisk. The fauna is represented by several species of herbivores, as well as hedgehogs, jerboas, gerbils, saccular rats and hamsters. From birds - eagles, falcons, owls.
Eastern region
Includes India and Indochina, as well as the islands of Ceylon, Java, Sumatra, Borneo, Taiwan and the Philippines. All the islands are completely covered with lush tropical forests, while a significant part of the mainland of the region is occupied by mountains with a diverse vegetation cover, turning into dry steppes in western India. From all tropical areas. The eastern region is the poorest in endemic (from the Greek endemos - local), i.e. found only in a given area, forms, although it is the center of origin and settlement of vertebrates.
A tropical forest. As in other tropical forests, hundreds of species of plants grow in abundance here, forming impenetrable thickets. Some typical plants are creepers, bamboo, manila hemp and teak, banyan and ebony. Among the animals, primates are widely represented - gibbons, orangutan, small relatives of monkeys - tupaya, tarsier, loris. Also characteristic are the Indian elephant, the tapir, two genera of rhinos, the porcupine, the tiger, the sloth bear and the bamboo bear, the deer and the antelope. Lots of pheasants poisonous snakes and various lizards, pheasants.
neotropical region
The region includes South and Central America, the tropical part of Mexico and the islands of the Caribbean archipelago. In continental South America, vast expanses are covered with tropical forests and steppes (pampas), but in some parts of the continent, as well as in Central America, there are relatively small areas that represent one of the most complex and unique plant complexes in the world. Because this area long time was completely isolated, its fauna, especially rodents, differs sharply from animals in other areas.
A tropical forest. Half of the continent is covered with tropical forest, unusually rich in lichens, mosses, orchids, bromeliads. Of the other plants, cabbage palm, tree fern, tropical almond, bamboo, creepers are characteristic. Lots of small animals.
Desert. The vegetation consists mainly of herbs and rare shrubs; date palms grow in oases. Euphorbia and plants with tuberous roots are found in the south. Of the animals, the gazelle, porcupine, jerboa, eagle, and lizards are common.
Steppes (pampas). The vegetation cover is a mixture of various herbs. Fauna - nandu, pampas deer, guinea pig, tuko-tuko, skunks.
australian area
The Australian region includes Australia, Tasmania, New Guinea, New Zealand and the Pacific Islands. In Australia, the central part of the mainland is represented by a desert bordered by steppes and savannahs with rare patches of tropical forest. The biomes of the islands are different - from tropical New Guinea to relatively cold New Zealand. The isthmuses that once connected separate parts of the land have long disappeared, and many endemic plants and animals arose on isolated islands. The niche occupied by placental mammals in all parts of the world is occupied by marsupials and partly wingless birds (kiwi). Main biomes:
Desert. The main vegetation is local forms of quinoa, acacias and various eucalyptus trees. Of the animals - marsupial mole, kangaroo mouse, jerboa marsupial rat, parakeets.
Savannah. Mostly steppes and thickets of various shrubs, eucalyptus, including red eucalyptus and other specific Australian plants. Of the animals, the giant red kangaroo and the emu are the most characteristic; there are also bandicoots, marsupial rabbit, wombats, cockatoos and other parrots.
A tropical forest represents either a typical forest of a hot and humid climate with a continuous canopy, numerous climbers and vines, or a rare eucalyptus forest. Tree kangaroo, koala, opossum, marsupial wolf, Tasmanian devil, platypus, flying dog, lyrebird live in the forests.
Thus, very short review biogeographic regions of the globe shows that on different continents, communities belonging to the same types (for example, tropical rainforests or steppes, deciduous forests or tundra) are inhabited by plants and animals belonging to different systematic groups. However, these animals and plants are characterized by similar organizational features due to similar environmental habitat conditions. Each biome has dominant, i.e. predominant groups both among types of plant communities and between animal populations. Knowledge of the genetic relationship of forms characteristic of a particular community in different regions of our planet, allows us to trace not only the development of fauna and flora, but also the origin of the biome as a whole
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