The first thing that catches your eye when you find yourself in low latitudes, in areas of the equatorial, subequatorial, tropical and subtropical zones, is the red color of the earth. Red clay, red sand, red muddy rivers after rains, red dust settling on the traveler’s clothes create a feeling of another planet for a person who comes from the world of gray and brown lands. Soil maps show how this "red belt" covers the Earth's landmass: soils at low latitudes are depicted using colors that have a red tint. And the names here are appropriate: red soils, red-yellow, red, brown-red, reddish-brown.
The Murray catchment is particularly important. Here are photos of some typical Australian soils. Recent lights on the Bathurst Island coast from Darwin. Terra Rosa on clayey limestone in the subtropical region of Russia. from Sydney. A humic soil, probably Pararendzin, on young limestone-sand deposits along the coast of south-west Victoria.
Old wet sandy soil over the beaches of south-west Victoria. The white horizon is colored by precipitated salt or limestone. Brown Ranch in a road cut on south coast. Eutrophic Cambyses on Maury Tower Hill. A layer of precipitated limestone is visible in the outflow of the tuff layer.
Why is the soil in the tropics so colored? This happened due to soil-forming rocks that were subjected to severe weathering. In this huge area globe Soil freezing never occurs. Almost everywhere here, with the exception of the subtropics, where it is cool in winter, there is constant summer. Over a significant part of this territory, more than 1000 mm of rain falls per year, i.e. a layer of water more than 1 m thick.
The vegetation of the poorer lake in the Murray flood is destroyed by flooding and soil salinization. They begin to spread halophytes such as salmon. In underdeveloped countries, one person costs about $400. There are three types of agriculture - agricultural, industrial, post-industrial.
Agriculture Performs two main tasks. It must provide food and raw materials for industry. It is divided into crop production and livestock production. Mechanization - machines are used, chemicals are used - fertilizers, sprays. The deployment of agriculture depends on many factors. Natural factors include soil, relief, climate. Socio-economic factors - market, transport, labor. Agro-industrial complex- cultivation, breeding, transportation, storage, processing of raw materials, sales, equipment, fertilizers.
Heat and moisture are a huge destructive force for minerals, since warm water dissolves them much more than water from melted snow. In addition, warmth and moisture are a fertile environment for the lush, which all year round“injects” more and more portions into the soil organic acids, and soil waters carry them to great depths. It is also very important that the age of the surface layers of soil in the tropics and subtropics is hundreds of thousands and millions of years. In this they are very different from the soils of temperate latitudes, where most of the territory was glaciated, and is determined by “only” tens of thousands of years.
Green revolution - best varieties, irrigation systems, chemical and technical means. About 100 million tons of wheat, 70 million tons of corn and 15 million tons per year are growing. Strawberry crops - potatoes - temperate zone, comes from I to South America 260 million tons, used as feed for the production of starch and alcohol, the disadvantage is that it loses its value after freezing, bananas, cassava, jams - sweet potatoes.
From America grown mainly in Europe, Russia, Japan, Europe, Ukraine, cotton - from seeds, China, India, Pakistan, peanuts - peanuts, up to 60% oil, Brazilian, India, Canada, olive oil - around Mediterranean Sea, subtropical zone, coconut palm - pulp drying, pressing, 70% oil, Philippines, Indonesia, tropical areas, Pacific Ocean, palm oil - Indonesia, Africa.
If we imagine that all the rain that fell in low latitudes over a million years went into the soil, then every piece of tropical land was washed with a huge mass of warm water with acid. The height of this water “column” is 1000 km. Of course, part of the water evaporates and flows over the surface without getting into the soil, but still, even if 1% of the fallen moisture is used to wash the soil (in fact, more), then the height of the column is not 1000, but 10 km. Try to imagine this destructive force! With such strong and long weathering, most minerals and chemical elements are washed out not only beyond the soil layer 2 m deep, but also to the depth of the weathering crust, which can be 5 m and even more than 10 m.
Fruits - Bananas - Latin America, pineapple - tropics, Pacific, citrus, grapevine, temperate - apples, plums, apricots, peaches, cherries. Vegetables - cabbage - the most common, temperate zone, tropics, tomatoes, peppers, carrots, onions.
America, Guinea Bay, Brazil. Textile crops - depends on where the fiber comes from. Spices - pepper - from India, dried berries, black, white, green, red, vanilla - in tropical regions, in America, in Mexico, in vanilla crystals, in cinnamon - Asian monsoon, in dried bell pepper bark - in Hungary, Bulgaria , Romania, Balkans, comes from America, caraway seeds - from Europe, the Netherlands, Czech Republic, mustard - temperate zone, Netherlands, France, seeds, horseradish - Czech Republic, temperate zone, Europe, bay leaf - Mediterranean.
IN upper layers weathering crust, which serves as the soil-forming rock for the soils of the tropics and subtropics, mainly the most stable minerals remain - kaolinite, consisting of aluminum, silicon, oxygen and hydrogen, silicon oxide - quartz, as well as large number oxides of iron and aluminum. It is these iron oxides that give soils and weathering crusts their red color. Sometimes such soils are called ferrallitic for their high iron content (from Latin ferrum - iron, aluminium - aluminum and Greek lithos - stone). In soils of the tropics and subtropics, especially when very humid, most nutrients washed out. They are contained only in litter, turf and humus horizon. It is from there that lush vegetation sucks them out and returns them there for their “descendants.”
Industrial crops - quinine - evergreen tree, quinine powder against malaria, bark made of powder, rubber - tropical forests, tree flowing from rubber, third natural rubber, Brazil, camphor-mastic, East Asia, something like menthol, massage, pressing camphor oil, potatoes - starch.
Livestock Domestic animals have been domesticated. Animals provide proteins, fats, skin, feathers, wool, meat, milk. Animals behave as a means of transport, labor, etc. animal breeding is divided into extensive and intensive. There are more than 400 breeds of cattle. There are yachts in Tibet, in large tropical areas. There are more than 1.5 billion cattle in the world. They provide 90% of the milk consumed, 40% of the meat consumed. The largest herds are in India, but are not exploited economically.
Where do the other colors in tropical soils come from? This is also due to iron oxides. The most important minerals are iron oxides, which “control” the color of the soil: the minerals of more weathered soils are red hematite and yellow limonite, and the minerals of less weathered soils are brown goethite. The first two names are easy to remember: hematite means “blood” in Greek, and limonite immediately reminds us of a yellow sour fruit. Goethite is named after the German writer Goethe. Red hematite is simply iron oxide with chemical formula Fe2C3, and yellow and brown minerals contain water associated with the oxide. Depending on the humidity of the climate and on the degree of weathering of minerals in the tropics and subtropics, such a “various colors” of soils is created.
Largest meat producer, Argentina. In densely populated areas there is intensive use of agriculture, mainly for milk, in sparsely populated areas it is more for meat and extensive farms. Raising pigs Provides a third of the meat. They behave in areas where there is enough corn and potatoes. They behave in climatic zone temperate climate with intensive reproduction. The advantage of pig farming is that it grows quickly and grows faster. Muslims do not eat pork.
Sheep farming was the most important before. A quarter of the sheep live for their wool, and the rest for meat, cheese, and milk. One sheep produces up to 5 kg of wool per year. Extensive farming is used in drier areas and is easy to propagate. Goat breeding Especially in Asia. They reproduce easily and are not widespread. They don't care about harsher conditions and are treated with milk and leather.
The most humid soils of the equatorial belt are red-yellow soils, and in subtropical zone they are called red soils and yellow soils. In these forest soils, the litter and small humus horizon are replaced by weathering with red and yellow colors. The highly weathered but less moist soils of subequatorial tall-grass savannas are called red soils. The humus horizon in them is much thicker than in forest equatorial soils. In drier savannas and hardleaf forests, the soils are less weathered, have less red hematite and more brown goethite, so these soils are called red-brown and brown-red. The humus horizon in them is less dark in color and less thick, and calcium carbonates may appear in the profile. Even drier and even less weathered soils of deserted savannas are classified as reddish-brown soils. In addition to carbonates, gypsum formations can also be found in them. And only in deserts where there has never been a humid climate (for example, in the central part of the Sahara), tropical soils not red. The soils here are classified as brown tropical desert soils. In the most lifeless deserts of the world, where precipitation may not fall for years (Atacama in and some areas of the Sahara), the soils are replaced by bare rocky and sandy surfaces. There are a lot of saline soils and salt marshes here. The Atacama is so dry that deposits of saltpeter (potassium nitrate), one of the most water-soluble salts, have formed there.
Poultry farming. Provides quality meat, eggs, feathers. Intensive breeding is very thoughtful. There are 11 billion poultry in the world. One chicken produces up to 300 eggs per year. Asia, donkeys and donkeys - mule - mare and donkey, mule - horse and donkey - in Latin America, northern northern regions, Lapland, Siberia - Tibet, mountainous regions, camels - llami - Andy, elephant - tropical regions, African, Indian regions, dogs - Eskimos, lamb and camel hybrid.
They are hunted primarily in beaded light belt areas. Fishing for cod, herring, mackerel, tuna, sardines. There are approximately one million whales in the seas. Their hunting is prohibited, but they are hunted in Norway, Russia, Japan. The sea is also used to produce energy, salt, other minerals, algae, shellfish, pearls, and crustaceans. Freshwater fishing is much less common.
Soils sub tropical zone often represent a transitional stage between the red soils of low latitudes and the soils of the temperate zone. The wettest red soils and yellow soils are closest to the soils of the equatorial belt. In the subtropics there are widespread soils in which the red color gradually disappears as the climate becomes drier. In the South American savannas - pampas, reddish-black soils are found. They seem to be between red soils and chernozems. They contain a reddish, weathered horizon beneath the horizon. In large areas of the Mediterranean, Eastern and in the mountains of Central Asia, as well as in America, and under subtropical dry forests and shrubs, brown soils are formed, in which there are signs of both reddish soils and soils of a temperate climate - brown soils. In the profile of brown soils, under the dark humus horizon, there is a weathering horizon that is redder than in brown soil. The soils of even drier landscapes - shrub steppes, Iran and Central Asia - are gray-brown (they are carbonate, and there is little humus in them), and from them it is a stone's throw to gray soils, which belong to the soils of the subtropics. Black coalescent soils are also common in the tropics and subtropics. In dry conditions, as well as in temperate zone, V soil cover In the tropics and subtropics, large areas can be occupied by takyrs, sandy desert soils, salt marshes, and solonetzes.
For tropical soils, invertebrate animals are primarily important, especially termites and huge earthworms. Termites use soil particles to build termite mounds so large that an elephant can hide in them. In arid places, termites are capable of making passages several tens of meters deep into the earth in order to reach groundwater. Together with water, they extract essential nutrients for nutrition. chemical elements and, bringing them to the surface of the soil, increase fertility. Worms play a huge role in the formation of tropical soils. Some of their species reach enormous sizes - 3 m in length and 2.5 cm in diameter. They mix the organic remains of tropical soils that fall to the surface, or drag them to depth, thereby saving them from immediate decomposition, and form humus horizons. Their emissions (20 - 25 cm high) to the surface resemble in size the emissions of moles.
Is it possible, without going to the distant southern regions, to feel at least a little bit like you’re in the tropics? If you mean the color of the earth, then you can. In the south of Russia, in the Sochi region, as well as among our neighbors in Azerbaijan, you can find real subtropical yellow soils, and in - real red soils. However, red soils also exist where, according to all the laws of soil geography, they should not exist, for example, in Arkhangelsk region, not far from, in Tatary, Perm and Kirov regions, some areas of the Trans-Urals, Siberia, in the steppes. Here, the red color of the soil is due to very ancient (hundreds of millions of years) weathering crusts, when the climate in these places was the same as in the modern tropics. In some places the glacier greatly crushed these ancient loose rocks, but their color was preserved. Ordinary podzolic soils and podzols with pink leaching horizons sometimes form on them, and sometimes even washing the soils with snow waters cannot change the original color of the rock. In the steppe, chernozems, chestnut soils, and solonetzes are formed on red rocks.
In the subtropical zone, the following main groups of soils are distinguished:
· Soils of moist forests
Soils of dry forests and shrubs
Dry subtropical steppes and low-grass semisavannas
Red soils and yellow soils humid subtropics. Widely developed in eastern Asia(China, Japan) to the southeast. USA - Florida and southern states. On the Black Sea coast (Adjara), Caspian Sea (Lepkoran). Climate. Precipitation ranges from 1 to 3 thousand mm per year, mild winters and moderately hot summers. Average annual t 14 0 C.
The vegetation is represented by hornbeam, oak, chestnut, and juniper. Biomass sub tropical forests exceeds 4000 c. with hectares
The soil-forming rocks of the red soils are the weathering crust, and there is an accumulation of Al and Fe enriched in kaolinite. How the color of the soil is determined.
Classification of red soils. Typical (occupying sloping slopes) and podzolized (developing on gentle slopes, available horizon A 2 contains humus from 4 to 9%, pH 4.2-4.5).
Yellow soils are formed in drier conditions and have a pale yellow color. IN rural farming These soils are used for growing tea, citrus fruits, grapes, fruits, and vegetables.
Brunozems wet subtropical soil. These soils are close to chernozem-like. They are found in North and South America within the humid subtropical pampa. They develop on basaltic metamorphic and weathered rocks. The relief is flat. The climate is warm and evenly humidified (500-1400 mm per year). Brunozems are divided into typical, leached, and reddish.
Brown soils of dry subtropical forests
And bushes.
In a variable-humid subtropical climate, brown soils form under dry forests and shrubs (oak, laurel, tree-like juniper, hawthorn). Precipitation (600-700 mm per year) falls from November to March. Soil-forming rocks are represented by Quaternary sediments, eluvium, limestone and dolomite.
Thickness A 1 – 60-70 cm of humus contains 4-6%.
Brown soils are divided into 3 subtypes
1. Brown leached ones boil below A 1 at a depth of 80-110 cm, develop in the most humid areas.
2. Brown typical - boil in horizon B.
3. Brown carbonate - characterized by carbonate content throughout the entire profile. They are confined to the most arid zones. Brown soils are characterized by high fertility. They grow grapes, fruit trees, and olives.
Gray soils of dry subtropics are presented in the foothills of the ridges Central Asia. The annual precipitation is 500-600 mm per year in summer t 0 reaches 30 0 C, in winter 1-2 0 C. Vegetation defines subtropical steppes and low-grass semi-savannas (cereals, giant umbellifers - ferula, ephemeral bluegrass, poppies, tulips).
The soil-forming rocks are loess. Cotton, rice, melons, and grapes are grown on irrigated soils.
Tropical soils. In this belt, the most common are red-yellow ferralitic soils of permanently humid tropical forests to red-brown soils of middle savannas and soils of tropical deserts. The soils of permanently humid tropical forests are colored red and yellow. They are located in South America, Africa, Madagascar, Ceylon and Australia.
The climate is characteristic high temperatures And a large number precipitation (more than 10,000 mm). Rainforests have huge biomass (5000 centners per hectare to 17000 centners per hectare). Most The litter is destroyed due to the intense destruction of microorganisms.
Soil-forming rocks are eruptive, effusive or sedimentary-metomorphic. Iron hydroxides are formed during soil formation. Humus content from 3-10% pH from 5.5 to 6.5. in the area of humid forests large area occupy the soils of tropical swamps.
Soils of tall grass savannas. Characteristic feature is the alternation of rainy and dry periods with an average annual amount of 1000-1500 mm. Red and yellow soils are formed on ancient weathering ridges. They are highly enriched with hydroxides. Humus content is 2-4%. These soils are quite fertile and are used for growing sugar cane, coffee, citrus fruits, and many crops.
Lecture 15 (2 hours)
Patterns of spatial distribution of soils
On the continents.
Soil geography is a field of soil science that studies general patterns soil distribution and soil cover of individual regions. Dokuchaev identified five world zones
1. Boreal
3. Black soil steppes
4. Aerial
5. Lateritic
In 1906, K.D. Glinka compiled the first soil map peace, which was demonstrated in 1927 at International Congress soil scientists in Washington. The combination of all materials across continents made it possible to create in 1956 new map world on a scale of 1:20000000 by a team of authors led by I.P. Gerasimov. Continental maps and a general summary map were compiled using a unified system and linked to the main physiographic components. Zonal soils are confined to one or another geographical zone: polar, boreal, subboreal, subtropical and tropical equatorial. In total, 31 types of zonal and 34 types of hydrozonal soils were identified, occupying lowland areas and 23 types of soils in mountainous areas.
The soil cover of different continents varies markedly. In Eurasia it is very diverse. In the northern part of Europe, soddy-podzolic soils predominate, and on the Scandinavian Peninsula and the polar islands arctic and tundra soils, and to the south there are brown soils. IN Western Siberia and Kazakhstan, Eastern Siberia soil zones change from forest-tundra to gray-brown, and in the territory of the D. Eastern part there are brown forest soils. Central Asia bears the soil cover of subtropical desert and desert-steppe soils. In the area of southern China, subtropical red soils and yellow soils and red ferralitic tropical soils with massifs of black soils are developed.
In Australia, red and yellow ferralitic soils are also common in the northern part; to the south they are replaced by red and red-brown soils of dry forests and savannas. Desert soils are located in the center of the continent (red deserts). In the eastern part of the continent, in the oceanic zone, red soils of tropical and subtropical forests have formed. In the mountains eastern Australia there are brown forests, western brown soils of dry forests and shrubs.
North America has a certain similarity in soil cover with northern part Eurasia. Arctic and tundra soils formed in the Arctic cover, and in Alaska - turf soils similar to Kamchatka. The northern part of the plains is covered with soddy-podzolic soils, and brown forest soils are found in the Appalachian region. West Coast The continent is represented by mountain-podzolic in the north and mountain-chernozem, as well as mountain-brown in the south.
In the south and central America Tropical ferralitic soils predominate. In areas of dry steppes, black and reddish-black soils are common. Mountain desert soils are developed in the mountain ranges. The Amazon and Orinoco basins have an abundance of marsh soils, while the Pacific coast of Peru and Chile is home to deserts with nitrate salt marshes.
Lecture 16 (2 hours)
Land resources peace
Among the main resources of the biosphere that are actively used by humans (water, air, vegetation, fauna), soil takes the leading place.
Land resources occupy about 1/3 of the planet's surface, almost 14.9 billion hectares, and without Antarctica and Greenland - 13.4 billion hectares.
10% - occupied by glaciers
15.5% - deserts, rocks, coastal sands
7.5% - tundra and swamps
2% - cities, mines, roads
3% - lands spoiled by man (bad land)
As a result, agricultural land accounts for only 11% or 1.5 billion hectares.
There is a trend towards a decrease in the area of agricultural land category. At the same time, the availability (in terms of 1 person) of arable land and forest land is decreasing.
Almost 1/3 (145 million hectares or 31%) is occupied by mountainous lands unsuitable for agriculture (Perinees, Carpathians, Alps, etc.).
More than 50 million hectares of land are waterlogged and require drainage reclamation; about 20 million hectares require irrigation; 83 million hectares require chemical reclamation.
One of the main reasons for changes in land use areas in agriculture is desertification. This process threatens the entire landmass and 20% of the population in 100 countries.
It is estimated that in the coming years, annual losses from desertification will reach $26 billion.
Currently, food production on average per person requires 0.3 - 0.5 hectares of land. On at the moment The planet's population is more than 6.5 billion people.
On our planet there is significant amount arable land. Their total area is 3 billion 190 million hectares. This means that the area of arable land can be doubled. The most commonly used soils are ferrallitic soils, chernozems, desertified soils, soddy-podzolic soils, and alluvial soils.
Land use in the cold zone
From arctic deserts up to mid-taiga forests, the limiting factor is heat deficiency. Livestock farming is of a focal nature. From crop production, it is possible to grow early ripening potatoes and cabbage in the forest-tundra.
