What is latitudinal zoning? Its main regularity. Latitudinal zoning and altitudinal zonality in the geographic envelope

Latitudinal (geographic, landscape) zoning means a natural change in various processes, phenomena, individual geographic components and their combinations (systems, complexes) from the equator to the poles. Zoning in elementary form was already known to scientists of Ancient Greece, but the first steps in the scientific development of the theory of world zoning are associated with the name of A. Humboldt, who at the beginning of the 19th century. substantiated the idea of ​​climatic and phytogeographic zones of the Earth. At the very end of the XIX century. V.V. Dokuchaev elevated latitudinal (in his terminology, horizontal) zoning to the rank of a world law.

For the existence of latitudinal zoning, two conditions are sufficient - the presence of a flux of solar radiation and the sphericity of the Earth. Theoretically, the flow of this flow to the earth's surface decreases from the equator to the poles in proportion to the cosine of latitude (Fig. 3). However, the actual amount of insolation entering the earth's surface is influenced by some other factors that are also astronomical in nature, including the distance from the Earth to the Sun. As you move away from the Sun, the flux of its rays becomes weaker, and at a sufficiently far distance the difference between the polar and equatorial latitudes loses its significance; so, on the surface of the planet Pluto, the calculated temperature is close to -230 ° С. On the other hand, when you get too close to the Sun, it is too hot in all parts of the planet. In both extreme cases, the existence of water in the liquid phase, life, is impossible. Thus, the Earth is most “fortunately” located in relation to the Sun.

The inclination of the earth's axis to the plane of the ecliptic (at an angle of about 66.5 °) determines the uneven inflow of solar radiation by seasons, which significantly complicates the zonal distribution

The mass of the Earth also affects the nature of zoning, albeit indirectly: it allows the planet (as opposed to, for example, "light

171 koy "of the Moon) to hold the atmosphere, which serves as an important factor in the transformation and redistribution of solar energy.

With a homogeneous material composition and the absence of irregularities, the amount of solar radiation on the earth's surface would change strictly in latitude and would be the same on the same parallel, despite the complicating influence of the listed astronomical factors. But in the complex and heterogeneous environment of the epigeosphere, the flow of solar radiation is redistributed and undergoes various transformations, which leads to a violation of its mathematically correct zoning.

Since solar energy is practically the only source of physical, chemical and biological processes that underlie the functioning of geographic components, latitudinal zoning must inevitably appear in these components. However, these manifestations are far from unambiguous, and the geographic mechanism of zoning turns out to be quite complex.

Already passing through the thickness of the atmosphere, the sun's rays are partially reflected and also absorbed by the clouds. Because of this, the maximum radiation arriving at the earth's surface is observed not at the equator, but in the belts of both hemispheres between the 20th and 30th parallels, where the atmosphere is most transparent to the sun's rays (Fig. 3). Over land, the contrasts of atmospheric transparency are more significant than over the Ocean, which is reflected in the figure of the corresponding curves. The curves of the latitudinal distribution of the radiation balance are somewhat smoother, but it is clearly noticeable that the surface of the Ocean is characterized by higher numbers than the land. The most important consequences of the latitude-zonal distribution of solar energy include the zoning of air masses, atmospheric circulation and moisture rotation. Under the influence of uneven heating, as well as evaporation from the underlying surface, four main zonal types of air masses are formed: equatorial (warm and humid), tropical (warm and dry), boreal, or masses of temperate latitudes (cool and humid), and arctic, and in Southern Hemisphere Antarctic (cold and relatively dry).

The difference in the density of air masses causes disturbances in thermodynamic equilibrium in the troposphere and mechanical movement (circulation) of air masses. Theoretically (without taking into account the influence of the Earth's rotation around the axis), air currents from heated near-equatorial latitudes should rise up and spread to the poles, and from there the cold and heavier air would return in the surface layer to the equator. But the deflecting action of the planet's rotation (Coriolis force) introduces significant amendments to this scheme. As a result, several circulation zones or belts are formed in the troposphere. For equator-

The 172nd belt is characterized by low atmospheric pressure, calmness, ascending air currents, for tropical belts - high pressure, winds with an eastern component (trade winds), moderate belts - low pressure, westerly winds, polar ones - low pressure, winds with an eastern component. In summer (for the corresponding hemisphere), the entire atmospheric circulation system shifts to its "own" pole, and in winter - to the equator. Therefore, in each hemisphere, three transitional belts are formed - subequatorial, subtropical and subarctic (subantarctic), in which the types of air masses change according to the seasons. Due to atmospheric circulation, zonal temperature differences on the earth's surface are somewhat smoothed out, however, in the Northern Hemisphere, where the land area is much larger than in the Southern, the maximum heat supply is shifted to the north, to about 10 - 20 ° N. NS. Since ancient times, it has been customary to distinguish five heat zones on Earth: two cold and temperate and one hot. However, this division is purely conventional, it is extremely schematic and its geographical significance is not great. The continual nature of the change in air temperature near the earth's surface makes it difficult to delineate the thermal zones. Nevertheless, using the latitudinal-zonal change of the main types of landscapes as a complex indicator, we can propose the following series of thermal zones, replacing each other from the poles to the equator:

1) polar (arctic and antarctic);

2) subpolar (subarctic and subantarctic);

3) boreal (cold-temperate);

4) subboreal (warm-moderate);

5) pre-subtropical;

6) subtropical;

7) tropical;

8) subequatorial;

9) equatorial.

The zoning of atmospheric circulation is closely related to the zoning of moisture circulation and humidification. A peculiar rhythm is observed in the distribution of precipitation over latitude: two maxima (the main one at the equator and the minor one at boreal latitudes) and two minima (in tropical and polar latitudes) (Fig. 4). As is known, the amount of precipitation does not yet determine the conditions for the moisture and moisture supply of landscapes. To do this, it is necessary to correlate the amount of precipitation falling annually with the amount that is necessary for the optimal functioning of the natural complex. The best integral indicator of the need for moisture is the amount of evaporation, i.e., the limiting evaporation theoretically possible at given climatic (and above all temperatures)

conditions. G.N. Vysotsky was the first to use this ratio back in 1905 to characterize the natural zones of European Russia. Subsequently, N.N. Ivanov, independently of G.N.Vysotsky, introduced an indicator into science, which became known as moisture factor Vysotsky - Ivanova:

K = g / E,

where G- the annual amount of precipitation; E- annual value of evaporation 1.

1 For comparative characteristics of atmospheric humidification, the dryness index is also used RfLr, proposed by M. I. Budyko and A. A. Grigoriev: where R- annual radiation balance; L- latent heat of vaporization; G- the annual amount of precipitation. In terms of its physical meaning, this index is close to the opposite indicator. TO Vysotsky-Ivanov. However, its application gives less accurate results.

In fig. 4 that the latitudinal changes in precipitation and evaporation do not coincide and, to a large extent, even have the opposite character. As a result, on the latitudinal curve TO in each hemisphere (for land) there are two critical points where TO goes through 1. The quantity TO- 1 corresponds to the optimum of atmospheric humidification; at K> 1 moisture becomes excessive, and when TO< 1 - insufficient. Thus, on the land surface, in its most general form, one can distinguish an equatorial belt of excessive moisture, two symmetrically located on both sides of the equator belts of insufficient moisture in low and middle latitudes and two belts of excessive moisture in high latitudes (see Fig. 4). Of course, this is a highly generalized, averaged picture that does not reflect, as we will see later, gradual transitions between belts and significant longitudinal differences within them.

The intensity of many physical and geographical processes depends on the ratio of tegoto supply and moisture. However, it is easy to see that the latitudinal-zonal changes in temperature conditions and moisture have different directions. If the reserves of solar heat generally increase from the poles to the equator (although the maximum is somewhat shifted to tropical latitudes), then the moisture curve has a sharply expressed wavy character. Without touching on the methods of quantitative assessment of the ratio of heat supply and humidification, let us outline the most general patterns of changes in this ratio in latitude. From the poles to approximately the 50th parallel, the increase in heat supply occurs under conditions of a constant excess of moisture. Further, with approaching the equator, an increase in heat reserves is accompanied by a progressive increase in dryness, which leads to a frequent change of landscape zones, the greatest diversity and contrast of landscapes. And only in a relatively narrow strip on both sides of the equator is there a combination of large reserves of heat with abundant moisture.

To assess the influence of climate on the zoning of other components of the landscape and the natural complex as a whole, it is important to take into account not only the average annual values ​​of heat and moisture supply indicators, but also their regime, i.e. intra-annual changes. So, for temperate latitudes, seasonal contrast of thermal conditions is characteristic with a relatively uniform intra-annual distribution of precipitation; in the subequatorial zone, with small seasonal differences in temperature conditions, the contrast between dry and wet seasons is sharply expressed, etc.

Climatic zoning is reflected in all other geographical phenomena - in the processes of runoff and hydrological regime, in the processes of waterlogging and the formation of groundwater

175 waters, the formation of the weathering crust and soil, in the migration of chemical elements, as well as in the organic world. Zoning is clearly manifested in the surface layer of the World Ocean. Geographic zoning is especially striking and to a certain extent integral expression in the vegetation cover and soils.

Separately, it should be said about the zoning of the relief and the geological foundation of the landscape. In the literature you can find statements that these components do not obey the law of zoning, i.e. azonal. First of all, it should be noted that it is illegal to divide the geographical components into zonal and azonal, because in each of them, as we will see, the influences of both zonal and azonal laws are manifested. The relief of the earth's surface is formed under the influence of the so-called endogenous and exogenous factors. The first include tectonic movements and volcanism, which are of an azonal nature and create morphostructural features of the relief. Exogenous factors are associated with the direct or indirect participation of solar energy and atmospheric moisture, and the sculptural forms of relief they create are distributed zonal on the Earth. Suffice it to recall the specific forms of the glacial relief of the Arctic and Antarctic, thermokarst depressions and heaving mounds of the Subarctic, ravines, gullies and subsidence depressions of the steppe zone, aeolian forms and drainless saline depressions of the desert, etc. In forest landscapes, a thick vegetation cover restrains the development of erosion and determines the predominance of "soft", weakly dissected relief. The intensity of exogenous geomorphological processes, for example, erosion, deflation, karst formation, significantly depends on latitudinal-zonal conditions.

The structure of the earth's crust also combines azonal and zonal features. If igneous rocks are of undoubtedly azonal origin, then the sedimentary stratum is formed under the direct influence of climate, the vital activity of organisms, soil formation and cannot but bear the stamp of zoning.

Throughout the entire geological history, sediment formation (lithogenesis) proceeded unevenly in different zones. In the Arctic and Antarctic, for example, unsorted clastic material (moraine) accumulated, in the taiga - peat, in deserts - clastic rocks and salts. For each specific geological era, it is possible to reconstruct a picture of the zones of that time, and each zone will have its own types of sedimentary rocks. However, over the course of geological history, the system of landscape zones has undergone repeated changes. Thus, the results of lithogenesis were superimposed on the modern geological map.

176 of all geological periods, when the zones were not at all the same as they are now. Hence the external variegation of this map and the absence of visible geographical patterns.

It follows from what has been said that zoning cannot be regarded as a simple imprint of the modern climate in the earth's space. Essentially, landscape zones are space-time formations, they have their own age, their own history and are changeable both in time and space. The modern landscape structure of the epigeosphere took shape mainly in the Cenozoic. The equatorial zone is distinguished by the greatest antiquity; with the distance to the poles, the zoning is experiencing more and more variability, and the age of the modern zones decreases.

The last significant restructuring of the world system of zoning, which captured mainly high and temperate latitudes, is associated with continental glaciations of the Quaternary period. Oscillatory displacements of zones continue here in the postglacial time. In particular, over the past millennia there has been at least one period when the taiga zone in places has advanced to the northern edge of Eurasia. The tundra zone within its present-day borders arose only after the subsequent retreat of the taiga to the south. The reasons for such changes in the position of the zones are associated with the rhythms of cosmic origin.

The action of the zoning law is most fully manifested in the relatively thin contact layer of the epigeosphere, i.e. in the actual landscape sphere. With distance from the surface of the land and ocean to the outer boundaries of the epigeosphere, the influence of zoning weakens, but does not completely disappear. Indirect manifestations of zoning are observed at great depths in the lithosphere, practically in the entire stratisphere, that is, in the thickness of sedimentary rocks, the relationship of which with zoning has already been mentioned. Zonal differences in the properties of artesian waters, their temperature, salinity, chemical composition can be traced down to a depth of 1000 m and more; the horizon of fresh groundwater in zones of excessive and sufficient moisture can reach a thickness of 200-300 and even 500 m, while in arid zones the thickness of this horizon is insignificant or it is completely absent. On the ocean floor, zoning is indirectly manifested in the nature of bottom silts, which are predominantly of organic origin. It can be considered that the law of zoning applies to the entire troposphere, since its most important properties are formed under the influence of the subaerial surface of the continents and the World Ocean.

In Russian geography, the significance of the law of zoning for human life and social production has been underestimated for a long time. V.V. Dokuchaev's judgments on this topic are

177 were considered as an exaggeration and a manifestation of geographical determinism. The territorial differentiation of the population and economy has its own laws, which cannot be completely reduced to the action of natural factors. However, to deny the influence of the latter on the processes taking place in human society would be a gross methodological mistake, fraught with serious socio-economic consequences, as we are convinced by all historical experience and modern reality.

Various aspects of the manifestation of the law of latitudinal zoning in the field of socio-economic phenomena are discussed in more detail in Ch. 4.

The zonality law finds its most complete, complex expression in the zonal landscape structure of the Earth, i.e. in the existence of the system landscape zones. The system of landscape zones should not be thought of as a series of geometrically regular continuous stripes. Even V.V.Dokuchaev did not think of zones as an ideal belt shape, strictly delimited by parallels. He emphasized that nature is not mathematics, and zoning is just a scheme or law. As we further investigated the landscape zones, it was found that some of them were torn, some zones (for example, the zone of broad-leaved forests) are developed only in the peripheral parts of the continents, others (deserts, steppes), on the contrary, tend to the inland regions; the boundaries of the zones deviate to a greater or lesser extent from the parallels and in some places acquire a direction close to the meridian; in the mountains, latitudinal zones seem to disappear and are replaced by altitudinal zones. Such facts gave rise to the 30s. XX century some geographers argue that latitudinal zoning is not a universal law at all, but only a special case characteristic of the great plains, and that its scientific and practical significance is exaggerated.

In reality, however, various kinds of violations of zoning do not refute its universal significance, but only indicate that it manifests itself differently in different conditions. Every natural law operates in different ways under different conditions. This also applies to such simple physical constants as the freezing point of water or the magnitude of the acceleration of gravity: they are not violated only under the conditions of a laboratory experiment. Many natural laws operate simultaneously in the epigeosphere. The facts, which at first glance do not fit into the theoretical model of zoning with its strictly latitudinal continuous zones, indicate that zoning is not the only geographical regularity and it is impossible to explain the entire complex nature of territorial physical-geographical differentiation only by it.

178 pressure peaks. In the temperate latitudes of Eurasia, the differences in average January air temperatures on the western periphery of the continent and in its inner extreme continental part exceed 40 ° C. In summer, it is warmer in the interior of the continents than in the periphery, but the differences are not so great. A generalized idea of ​​the degree of oceanic influence on the temperature regime of continents is given by indicators of the continentality of the climate. There are various methods for calculating such indicators, based on taking into account the annual amplitude of average monthly temperatures. The most successful indicator, taking into account not only the annual amplitude of air temperatures, but also the daily, as well as the lack of relative humidity in the driest month and the latitude of the point, was proposed by N.N. Ivanov in 1959. Taking the average planetary value of the indicator as 100%, the scientist divided the whole series of values ​​obtained by him for different points of the globe into ten continental belts (in brackets, the numbers are given in percent):

1) extremely oceanic (less than 48);

2) oceanic (48 - 56);

3) temperate oceanic (57 - 68);

4) sea (69 - 82);

5) slightly marine (83-100);

6) slightly continental (100-121);

7) moderately continental (122-146);

8) continental (147-177);

9) sharply continental (178 - 214);

10) extremely continental (over 214).

On the diagram of the generalized continent (Fig. 5), the belts of continental climate are arranged in the form of concentric bands of irregular shape around the extremely continental cores in each hemisphere. It is easy to see that at almost all latitudes, continental varies widely.

About 36% of atmospheric precipitation falling on the land surface is of oceanic origin. As it moves inland, sea air masses lose moisture, leaving most of it on the periphery of the continents, especially on the slopes of mountain ranges facing the Ocean. The greatest longitudinal contrast in the amount of precipitation is observed in tropical and subtropical latitudes: abundant monsoon rains on the eastern periphery of the continents and extreme aridity in the central, and partly in the western regions affected by the continental trade winds. This contrast is aggravated by the fact that the evaporation rate sharply increases in the same direction. As a result, on the Pacific Ocean periphery of the tropics of Eurasia, the moisture coefficient reaches 2.0 - 3.0, while in most of the tropical zone it does not exceed 0.05,

181 physical and geographical zoning of the Earth, he divided all continents into three longitudinal sectors- western, eastern and central and for the first time noted that each sector differs in its characteristic set of latitudinal zones. However, the English geographer A.J. Herbertson, who back in 1905 divided the land into natural belts and in each of them identified three longitudinal segments - western, eastern and central.

With the subsequent, deeper study of the pattern, which has come to be called the longitudinal sector, or simply sector, it turned out that the three-term sectoral division of the entire land mass is too schematic and does not reflect the entire complexity of this phenomenon. The sectoral structure of the continents has a clearly pronounced asymmetric character and is not the same in different latitudinal belts. So, in tropical latitudes, as already noted, a two-term structure is clearly outlined, in which the continental sector dominates, and the western one is reduced. In polar latitudes, sectorial physical and geographical differences are weakly manifested due to the dominance of fairly uniform air masses, low temperatures and excessive moisture. In the real belt of Eurasia, where the land has the greatest (almost 200 °) length in longitude, on the contrary, not only are all three sectors well expressed, but it is also necessary to establish additional, transitional stages between them.

The first detailed scheme of the sectoral division of the land, implemented on the maps of the Physico-Geographical Atlas of the World (1964), was developed by E. N. Lukashova. There are six physical-geographical (landscape) sectors in this scheme. The use of quantitative indicators as criteria for sectoral differentiation - moisture and continental coefficients, and as a complex indicator - the boundaries of the distribution of zonal types of landscapes made it possible to detail and clarify the scheme of E. N. Lukashova.

Here we come to the essential question of the relationship between zoning and sector. But first it is necessary to pay attention to a certain duality in the use of terms. zone and sector. In a broad sense, these terms are used as collective, essentially typological concepts. So, speaking "desert zone" or "steppe zone" (in the singular), they often mean the whole set of territorially separated areas with the same type of zonal landscapes, which are scattered in different hemispheres, on different continents and in different sectors of the latter. Thus, in such cases, the zone is not thought of as a single integral territorial block, or region, i.e. cannot be considered as an object of regionalization. But at the same time, the same ter-

182 mines can refer to specific, integral, territorially isolated units that correspond to the concept of the region, for example Desert Zone of Central Asia, Steppe Zone of Western Siberia. In this case, we are dealing with objects (taxa) of regionalization. In the same way, we have the right to speak, for example, of the "western oceanic sector" in the broadest sense of the word as a global phenomenon uniting a number of specific territorial areas on different continents - in the Atlantic part of Western Europe and the Atlantic part of the Sahara, along the Pacific slopes of the Rocky mountains, etc. Each such piece of land is an independent region, but they are all analogues and are also called sectors, but understood in a narrower sense of the word.

The zone and sector in the broad sense of the word, which clearly has a typological connotation, should be interpreted as a common noun and, accordingly, write their names with a lowercase letter, while the same terms in a narrow (i.e., regional) sense and included in their own geographical name, - with a capital letter. Options are possible, for example: the Western European Atlantic sector instead of the Western European Atlantic sector; Eurasian Steppe Zone instead of Eurasian Steppe Zone (or Eurasian Steppe Zone).

There are complex relationships between zoning and sectorization. Sector differentiation largely determines the specific manifestations of the law of zoning. Longitudinal sectors (in a broad sense), as a rule, are elongated across the strike of latitudinal zones. When moving from one sector to another, each landscape zone undergoes a more or less significant transformation, and for some zones the boundaries of the sectors turn out to be completely insurmountable barriers, so that their distribution is limited to strictly defined sectors. For example, the Mediterranean zone is confined to the western oceanic sector, and the subtropical wet forest - to the eastern oceanic one (Table 2 and Fig. B) 1. The reasons for such seeming anomalies should be sought in the zonal-sector laws.

1 In fig. 6 (as in Fig. 5) all continents are brought together in strict accordance with the distribution of land in latitude, observing a linear scale along all parallels and the axial meridian, that is, in the Sanson equal-area projection. This transmits the actual area ratio of all contours. A similar, widely known and included in textbooks scheme of E.N. Lukashova and A.M. Ryabchikov was built without observing the scale and therefore distorts the proportions between the latitudinal and longitudinal extent of the conditional land mass and the areal relationships between individual contours. The essence of the proposed model is more accurately expressed by the term generalized continent instead of the often used perfect continent.

The main criteria for the diagnosis of landscape zones are objective indicators of heat supply and moisture. It has been experimentally established that among the many possible indicators for our purpose, the most acceptable

It should be noted that each such series of analogous zones fits into a certain range of values ​​of the adopted heat supply indicator. So, the zones of the subboreal series lie in the range of the sum of temperatures 2200-4000 "C, subtropical - 5000 - 8000" C. Within the accepted scale, less clear thermal differences are observed between the zones of the tropical, subequatorial and equatorial belts, but this is quite natural, since in this case, the determining factor of zonal differentiation is not heat supply, but humidification 1.

If the rows of analogous zones in terms of heat supply generally coincide with latitudinal belts, then the rows of humidification are of a more complex nature, containing two components - zonal and sectoral, and there is no unidirectionality in their territorial change. Differences in atmospheric humidification due to

1 Due to this circumstance, as well as due to the lack of reliable data in table. 2 and fig. Tropical and subequatorial belts 7 and 8 are united and the analogous zones related to them are not delimited.

187 are caught both by zonal factors during the transition from one latitudinal belt to another, and by sector factors, i.e., by longitudinal moisture advection. Therefore, the formation of analogous zones in terms of moisture in some cases is associated mainly with zoning (in particular, taiga and equatorial forest in the humid row), in others - with sector (for example, subtropical humid forest in the same row), and in others, with a coinciding effect. both patterns. The latter case includes the zones of subequatorial variable moisture forests and forest savannas.

The surface of our planet is heterogeneous and is conventionally divided into several belts, which are also called latitudinal zones. They regularly replace each other from the equator to the poles. What is latitudinal zoning? Why does it depend and how does it manifest itself? We will talk about all this.

What is latitudinal zoning?

In certain corners of our planet, natural complexes and components differ. They are unevenly distributed and can seem chaotic. However, they have certain patterns, and they divide the surface of the Earth into so-called zones.

What is latitudinal zoning? This is the distribution of natural components and physical and geographical processes in belts parallel to the equatorial line. It manifests itself in differences in the average annual amount of heat and precipitation, the change of seasons, vegetation and soil cover, as well as representatives of the animal world.

In each hemisphere, the zones replace each other from the equator to the poles. In areas where mountains are present, this rule changes. Here, natural conditions and landscapes are replaced from top to bottom, relative to the absolute height.

Both latitudinal and altitudinal zoning are not always expressed in the same way. Sometimes they are more noticeable, sometimes less. The peculiarities of the vertical change of zones largely depend on the distance of the mountains from the ocean, the location of the slopes in relation to the passing air currents. The most pronounced altitudinal zonation is expressed in the Andes and the Himalayas. What is latitudinal zoning is best seen in lowland regions.

What does zoning depend on?

The main reason for all the climatic and natural features of our planet is the Sun and the position of the Earth relative to it. Due to the fact that the planet has a spherical shape, the solar heat is distributed unevenly over it, heating some areas more, others less. This, in turn, contributes to unequal heating of the air, which is why winds arise, which also participate in the formation of the climate.

The natural features of individual parts of the Earth are also influenced by the development of the river system on the terrain and its regime, the distance from the ocean, the level of salinity of its waters, sea currents, the nature of the relief and other factors.

Manifestation on the continents

On land, latitudinal zoning is more pronounced than in the ocean. It manifests itself in the form of natural zones and climatic zones. The following belts are distinguished in the Northern and Southern Hemispheres: equatorial, subequatorial, tropical, subtropical, temperate, subarctic, arctic. Each of them has its own natural zones (deserts, semi-deserts, arctic deserts, tundra, taiga, evergreen forest, etc.), of which there are many more.

On which continents is the latitudinal zoning pronounced? It is best observed in Africa. It can be traced quite well on the plains of North America and Eurasia (Russian Plain). In Africa, latitudinal zoning is clearly visible due to the small number of high mountains. They do not create a natural barrier to air masses, therefore climatic zones replace each other without breaking the pattern.

The equator line crosses the African continent in the middle, so its natural zones are distributed almost symmetrically. So, humid equatorial forests pass into savannas and light forests of the subequatorial belt. This is followed by tropical deserts and semi-deserts, which are replaced by subtropical forests and shrubs.

Interestingly, zoning is manifested in North America. In the north, it is usually distributed in latitude and is expressed by the tundra of the arctic and taiga of the subarctic belts. But below the Great Lakes, the zones are distributed parallel to the meridians. The high Cordillera to the west block the winds from the Pacific. Therefore, natural conditions change from west to east.

Zoning in the ocean

The change of natural zones and belts also exists in the waters of the World Ocean. It is visible at a depth of up to 2000 meters, but very clearly traced at a depth of 100-150 meters. It manifests itself in a different component of the organic world, the salinity of water, as well as its chemical composition, in the temperature difference.

The belts of the oceans are practically the same as on land. Only instead of the arctic and subarctic, there is a subpolar and polar, since the ocean reaches directly to the North Pole. In the lower layers of the ocean, the boundaries between the belts are stable, while in the upper layers they can shift depending on the season.

Latitudinal (geographic, landscape) zoning means a natural change in physical and geographical processes, components and complexes (geosystems) from the equator to the poles.

The belt distribution of solar heat on the earth's surface determines the uneven heating (and density) of atmospheric air. The lower atmosphere (troposphere) in the tropics warms up strongly from the underlying surface, and weakly in the circumpolar latitudes. Therefore, above the poles (up to an altitude of 4 km) there are areas with increased pressure, and at the equator (up to 8-10 km) there is a warm ring with reduced pressure. With the exception of circumpolar and equatorial latitudes, the rest of the space is dominated by western air transport.

The most important consequences of uneven latitudinal heat distribution are the zoning of air masses, atmospheric circulation and moisture circulation. Under the influence of uneven heating, as well as evaporation from the underlying surface, air masses are formed, differing in their temperature properties, moisture content and density.

There are four main zonal types of air masses:

1. Equatorial (warm and humid);

2. Tropical (warm and dry);

3. Boreal, or masses of temperate latitudes (cool and humid);

4. Arctic, and in the southern hemisphere Antarctic (cold and relatively dry).

Unequal heating and, as a result, different density of air masses (different atmospheric pressure) cause disturbance of thermodynamic equilibrium in the troposphere and movement (circulation) of air masses.

As a result of the deflecting action of the Earth's rotation, several circulation zones are formed in the troposphere. The main ones correspond to four zonal types of air masses, so there are four of them in each hemisphere:

1. Equatorial zone common to the northern and southern hemispheres (low pressure, calm, updrafts);

2. Tropical (high pressure, easterly winds);

3. Moderate (low pressure, westerly winds);

4. Polar (low pressure, easterly winds).

In addition, there are three transition zones:

1. Subarctic;

2. Subtropical;

3. Subequatorial.

In transitional zones, the types of circulation and air masses change seasonally.

The zoning of atmospheric circulation is closely related to the zoning of moisture circulation and humidification. This is clearly manifested in the distribution of atmospheric precipitation. The zoning of precipitation distribution has its own specificity, a kind of rhythm: three maxima (the main one at the equator and two minor ones in temperate latitudes) and four minima (in polar and tropical latitudes).

The amount of precipitation in itself does not determine the conditions for moisture or moisture supply of natural processes and the landscape as a whole. In the steppe zone, with 500 mm of annual precipitation, we are talking about insufficient moisture, and in the tundra, at 400 mm, it is excessive. To judge the moisture content, one needs to know not only the amount of moisture supplied to the geosystem annually, but also the amount that is necessary for its optimal functioning. The best indicator of the need for moisture is volatility, that is, the amount of water that can evaporate from the earth's surface in a given climatic conditions, assuming that moisture reserves are not limited. Evaporation is a theoretical value. It should be distinguished from evaporation, that is, actually evaporating moisture, the amount of which is limited by the amount of precipitation. On land, evaporation is always less than evaporation.

The ratio of the annual precipitation to the annual evaporation rate can serve as an indicator of climatic humidification. This indicator was first introduced by G.N. Vysotsky. Back in 1905, he used it to characterize the natural areas of European Russia. Subsequently, N. N. Ivanov plotted the isolines of this ratio, which was called the moisture coefficient (K). The boundaries of landscape zones coincide with certain values ​​of K: in the taiga and tundra it exceeds 1, in the forest-steppe it is 1.0 - 0.6, in the steppe - 0.6 - 0.3, in the semi-desert 0.3 - 0.12, in the desert - less than 0.12.

Zoning is expressed not only in the average annual amount of heat and moisture, but also in their mode, i.e., in intra-annual changes. It is generally known that the equatorial zone is distinguished by the most even temperature regime, four thermal seasons are typical for temperate latitudes, etc. The zonal types of precipitation regime are varied: in the equatorial zone precipitation falls more or less evenly, but with two maxima; in subequatorial latitudes, summer is sharply expressed. maximum, in the Mediterranean zone - winter maximum, uniform distribution with a summer maximum is characteristic for temperate latitudes, etc.

Climatic zoning is reflected in all other geographic phenomena - in the processes of runoff and hydrological regime, in the processes of waterlogging and formation of groundwater, the formation of the weathering crust and soils, in the migration of chemical elements, in the organic world. Zoning is clearly manifested in the surface layer of the ocean (Isachenko, 1991).

Latitudinal zoning is not consistent everywhere - only Russia, Canada and North Africa.

Provinciality

Provinciality refers to changes in the landscape within a geographic zone when moving from the outskirts of the mainland to its interior. Provinciality is based on longitudinal and climatic differences as a result of atmospheric circulation. Longitudinal climatic differences, interacting with the geological and geomorphological features of the territory, are reflected in soils, vegetation and other components of the landscape. The oak forest-steppe of the Russian Plain and the birch forest-steppe of the West Siberian Lowland are an expression of provincial changes of the same forest-steppe type of landscape. The same expression of the provincial differences in the forest-steppe type of landscape is the Central Russian Upland dissected by ravines and the flat Oka-Don plain dotted with aspen bushes. In the system of taxonomic units, provinciality is best revealed through physical-geographical countries and physical-geographical provinces.

Sectorality

Geographic sector is a longitudinal segment of a geographic belt, the originality of which is determined by longitudinal-climatic and geological-orographic intra-belt differences.

The landscape-geographical consequences of the continental-oceanic circulation of air masses are extremely diverse. It was noticed that as the distance from the oceanic coasts to the interior of the continents, a natural change of plant communities, animal population, and soil types takes place. Currently, the term “sector” is adopted. Sectorality is the same general geographic pattern as zoning. Some analogy is noticeable between them. However, if both heat supply and humidification play an important role in the latitudinal-zonal change in natural phenomena, then humidification is the main factor of the sector. Heat reserves do not change so significantly in longitude, although these changes also play a certain role in the differentiation of physical and geographical processes.

Physico-geographical sectors are large regional units stretching in a direction close to the meridional and replacing one another in longitude. So, in Eurasia there are up to seven sectors: humid Atlantic, Moderate continental East European, sharply continental East Siberian-Central Asian, Monsoon Near Pacific and three others (mostly transitional). In each sector, the zoning acquires its own specifics. In the oceanic sectors, the zonal contrasts are smoothed; they are characterized by a forest spectrum of latitudinal zones from taiga to equatorial forests. The continental spectrum of zones is distinguished by the predominant development of deserts, semi-deserts, and steppes. The taiga has special features: permafrost, the dominance of light coniferous larch forests, the absence of podzolic soils, etc.

Latitudinal zoning- a natural change in physical and geographical processes, components and complexes of geosystems from the equator to the poles.

Reasons for zoning

The primary reason for natural zoning is the uneven distribution of solar energy in latitude due to the spherical shape of the Earth and changes in the angle of incidence of sunlight on the earth's surface. In addition, from the distance to the Sun, and the mass of the Earth affects the ability to hold the atmosphere, which serves as a transformer and redistribution of energy.

The inclination of the axis to the plane of the ecliptic is of great importance, the irregularity of the solar heat supply by seasons depends on this, and the daily rotation of the planet determines the deviation of air masses. The result of the difference in the distribution of the solar radiant energy is the zonal radiation balance of the earth's surface. The unevenness of heat input affects the location of air masses, moisture circulation and atmospheric circulation.

Zoning is expressed not only in the average annual amount of heat and moisture, but also in intra-annual changes. Climatic zoning is reflected in the runoff and hydrological regime, the formation of the weathering crust, waterlogging. It has a great influence on the organic world, specific forms of relief. The homogeneous composition and high mobility of the air smooth out the zonal differences with height.

There are 7 circulation zones in each hemisphere. Latitudinal zoning is also manifested in the World Ocean.

The main reason for latitudinal zoning is the change in the ratio of heat and moisture from the equator to the poles.

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Literature

• Dokuchaev V.V.: Horizontal and vertical soil zones. SPb .: type. SPb. city ​​administration, 1899.28 p.
• Milkov F.N., Gvozdetsky N.A. Physical geography of the USSR. Part 1. - M .: Higher school, 1986.

Excerpt from Latitudinal Zoning

Latitudinal zoning- a natural change in physical and geographical processes, components and complexes of geosystems from the equator to the poles. Latitudinal zoning is due to the spherical shape of the Earth's surface, as a result of which there is a gradual decrease in the amount of heat coming to it from the equator to the poles.

Altitudinal zonality- a regular change in natural conditions and landscapes in the mountains as the absolute height increases. Altitudinal zonation is explained by climate change with altitude: a drop in air temperature with altitude and an increase in precipitation and atmospheric humidification. Vertical zonation always begins with the horizontal zone in which the mountainous country is located. Above the belt, they are replaced in general in the same way as the horizontal zones, up to the area of ​​polar snows. Sometimes the less accurate name "vertical zonality" is used. It is inaccurate because the belts are not vertical, but horizontal, and replace each other in height (Figure 12).

Figure 12 - Altitude zonation in the mountains

Natural areas- These are natural-territorial complexes within the geographic zones of land, corresponding to the types of vegetation. Relief plays an important role in the distribution of natural zones in the belt, its pattern and absolute heights - mountain barriers that block the path of the air flow, contribute to the rapid change of natural zones to more continental ones.

Natural zones of equatorial and subequatorial latitudes. Zone humid equatorial forests (gilea) is located in the equatorial climate zone with high temperatures (+ 28 ° С), and a large amount of precipitation throughout the year (more than 3000 mm). The zone is most widespread in South America, where it occupies the Amazon basin. In Africa, it is located in the Congo Basin, in Asia - on the Malacca Peninsula and the Great and Small Sunda Islands and New Guinea (Figure 13).

Figure 13 - Natural zones of the Earth

Evergreen forests are dense, rugged, grow on red-yellow ferralite soils. Forests differ in species diversity: an abundance of palms, lianas and epiphytes; mangroves are widespread along the sea coasts. There are hundreds of species of trees in such a forest, and they are arranged in several tiers. Many of them bloom and bear fruit all year round.

The fauna is also diverse. Most of the inhabitants are adapted to life in trees: monkeys, sloths, etc. Terrestrial animals are characterized by tapirs, hippos, jaguars, leopards. There are a lot of birds (parrots, hummingbirds), the world of reptiles, amphibians and insects is rich.

Savannah and woodland zone located in the subequatorial belt of Africa, Australia, South America. The climate is characterized by high temperatures, alternating wet and dry seasons. The soils are of a peculiar color: red and red-brown or reddish-brown, in which iron compounds accumulate. Due to insufficient moisture, the vegetation cover is an endless sea of ​​grasses with detached low trees and thickets of shrubs. Woody vegetation gives way to grasses, mainly tall grasses, sometimes reaching 1.5–3 meters in height. Numerous cactus and agave species are common in the American savannahs. Certain types of trees have adapted to the dry period, storing moisture or retarding evaporation. These are African baobabs, Australian eucalyptus trees, South American bottle trees and palms. The animal world is rich and varied. The main feature of the savannah fauna is the abundance of birds, ungulates and the presence of large predators. Vegetation contributes to the spread of large herbivorous and carnivorous mammals, birds, reptiles, insects.

Zone variable humid deciduous forests from the east, north and south, it frames the gileas. Both evergreen rigid-leaved species, which are characteristic of gilis, and species that partially shed their foliage in summer are widespread here; lateritic red and yellow soils are formed. The fauna is rich and varied.

Natural zones of tropical and subtropical latitudes. In the tropical belt of the Northern and Southern Hemispheres, zone of tropical deserts. The climate is tropical desert, hot and dry, because the soils are underdeveloped, often saline. Vegetation on such soils is scarce: rare hard grasses, thorny shrubs, hodgepodge, lichens. The fauna is richer than the flora, since reptiles (snakes, lizards) and insects are able to stay without water for a long time. Among mammals - ungulates (gazelle antelope, etc.), capable of covering long distances in search of water. Oases are located near the water sources - "spots" of life among the dead desert spaces. Date palms and oleanders grow here.

In the tropical zone, there is also zone of humid and variable-humid tropical forests. It formed in the eastern part of South America, in the northern and northeastern parts of Australia. The climate is humid with consistently high temperatures and a lot of rainfall, which falls in the summer during monsoon rains. On red-yellow and red soils, variable-moist, evergreen forests, rich in species composition (palms, ficuses), grow. They are like equatorial forests. The fauna is rich and varied (monkeys, parrots).

Subtropical stiff-leaved evergreen forests and shrubs typical for the western part of the continents, where the climate is Mediterranean: hot and dry summers, warm and rainy winters. The brown soils are highly fertile and are used for the cultivation of valuable subtropical crops. The lack of moisture during the period of intense solar radiation led to the appearance in plants of adaptations in the form of hard leaves with a waxy bloom, which reduce evaporation. Stiff-leaved evergreen forests are decorated with laurels, wild olives, cypresses, and yews. In large areas, they have been cut down, and their place is taken by fields of grain crops, orchards and vineyards.

Zone of humid subtropical forests located in the east of the continents, where the climate is subtropical monsoon. Precipitation occurs in summer. The forests are dense, evergreen, broad-leaved and mixed; they grow on red and yellow soils. The fauna is diverse, there are bears, deer, roe deer.

Zones of subtropical steppes, semi-deserts and deserts distributed by sectors in the interior regions of the continents. In South America, the steppes are called pampas. The subtropical dry climate with hot summers and relatively warm winters allows drought-resistant grasses and grasses (wormwood, feather grass) to grow on gray-brown steppe and brown desert soils. The fauna is distinguished by its species diversity. Typical mammals are gophers, jerboas, gazelles, kulans, jackals and hyenas. Lizards and snakes are numerous.

Natural zones of temperate latitudes include zones of deserts and semi-deserts, steppes, forest-steppes, forests.

Deserts and semi-deserts temperate latitudes occupy large areas in the interior of Eurasia and North America, small areas in South America (Argentina), where the climate is sharply continental, dry, with cold winters and hot summers. On gray-brown desert soils, poor vegetation grows: steppe feather grass, wormwood, camel thorn; in depressions on saline soils - saltwort. The fauna is dominated by lizards, snakes, turtles, jerboas, saigas are widespread.

Steppe occupy large areas in Eurasia, South and North America. In North America, they are called prairies. The climate of the steppes is continental and dry. Due to the lack of moisture, there are no trees and a rich grass cover is developed (feather grass, fescue and other grasses). In the steppes, the most fertile soils are formed - chernozem. In the summer, the vegetation in the steppes is sparse, and in the short spring, many flowers bloom; lilies, tulips, poppies. The fauna of the steppes is represented mainly by mice, gophers, hamsters, as well as foxes and ferrets. The nature of the steppes has largely changed under the influence of man.

To the north of the steppes is the zone forest-steppe. This is a transitional zone, the forest areas in it are interspersed with significant areas covered with grassy vegetation.

Deciduous and mixed forest zones represented in Eurasia, North and South America. The climate, when moving from the oceans inward to the continents, changes from maritime (monsoon) to continental. Vegetation changes depending on the climate. The zone of deciduous forests (beech, oak, maple, linden) becomes the zone of mixed forests (pine, spruce, oak, hornbeam, etc.). To the north and further inland, conifers are widespread (pine, spruce, fir, larch). Small-leaved species (birch, aspen, alder) are also found among them.

The soils in the broad-leaved forest are brown forest, in the mixed forest - sod-podzolic, in the taiga - podzolic and permafrost-taiga. Almost all forest zones of the temperate zone are characterized by a wide distribution swamps.

The fauna is very diverse (deer, brown bears, lynxes, wild boars, roe deer, etc.).

Natural zones of subpolar and polar latitudes. Forest tundra is a transitional zone from forests to tundra. The climate in these latitudes is cold. Soils are tundra-gley, podzolic and peat-boggy. Light forest vegetation (low larch, spruce, birch) gradually turns into tundra. The fauna is represented by the inhabitants of the forest and tundra zones (snowy owls, lemmings).

Tundra characterized by treelessness. The climate is characterized by long cold winters, damp and cold summers. This leads to severe freezing of the soil, forms permafrost. Evaporation here is small, organic matter does not have time to decompose and, as a result, swamps are formed. Moss, lichens, low grasses, dwarf birches, willows, etc. mossy, lichen, shrub. The fauna is poor (reindeer, arctic fox, owls, pies).

Arctic (Antarctic) Desert Zone located in polar latitudes. Due to the very cold climate with low temperatures throughout the year, large areas of land are covered with glaciers. The soils are almost undeveloped. In ice-free areas, there are stony deserts with very poor and sparse vegetation (mosses, lichens, algae). Polar birds settle on the rocks, forming “bird colonies”. In North America, there is a large ungulate animal - the musk ox. The natural conditions in Antarctica are even more severe. Penguins, petrels, cormorants nest on the coast. Whales, seals and fish live in Antarctic waters.