THERMAL ZONES OF THE EARTH: CHARACTERISTICS, FLORA AND FAUNA - GEOGRAPHY - 2024

The thermal zones of the Earth are latitudinal geographic strips of the planet defined based on its annual average temperatures. In general terms, the thermal zones of the Earth are the warm zone, the temperate zone and the cold zone.

The warm zone is located between the Tropic of Cancer and the Tropic of Capricorn, in a continuous band on both sides of the Equator. The temperate zone features two separate areas, one between the Tropic of Cancer and the Arctic Circle and the other between the Tropic of Capricorn and the Antarctic Circle.

Map of the average annual temperature depending on the location. Source:

For its part, the cold zone, like the temperate zone, forms two areas, one at each terrestrial pole. These define the so-called polar circles, the Arctic Circle and the Antarctic Polar Circle.

From another perspective, taking into account that the temperature also varies with the height above sea level, altitude thermal zones are established. In this sense, the climate in the mountains reproduces the thermal zones, establishing a warm floor, a temperate one, and a cold or alpine one.

Warm zone

The warm zone of the Earth encompasses the so-called intertropical strip, also a torrid zone or simply a tropical zone. It is bounded by the Tropic of Cancer line to the north (23 ° N) and the Tropic of Capricorn to the south (23 ° S). From the biogeographic and climatic point of view, in this zone are the tropical and subtropical life zones.

- Characteristics

Weather

The hot or tropical climate is characterized by high solar radiation, high average temperatures throughout the year, and high rainfall. Every month they have average temperatures higher than 18 ºC, being close to 27 or 29 ºC.

In some cases, a subtropical zone is delimited in the transition area between the tropical and temperate zones, around the tropics. The subtropical zone is characterized because the average temperature of the warmest month exceeds 22 ºC.

Rain forest. Source: Delorme at French Wikipedia

Rainfall generally exceeds 1,000 mm on average per year, being lower in dry forests (600 to 1,000 mm). In the rain forests, precipitation can reach up to 16,000 mm per year, as occurs in the Chocó jungle (Colombia).

The precipitations can be uniformly distributed during the year or concentrated mainly in a period. In the latter case, two climatic seasons are formed, a dry period and a rainy one.

Floors

An important problem in tropical soils is the leaching or washing of nutrients due to high rainfall. Otherwise soils are variable both in structure, texture and fertility.

Water

Tropical seas and oceans are warm waters, generally low in nutrients, but the temperature facilitates the development of highly productive biomes. Among these are coral reefs and mangroves with associated underwater grasslands.

Due to the high equatorial rainfall, in the warm or tropical zone there are extensive hydrographic basins. Among them are the basins of large rivers such as the Amazon (America), the Congo (Africa) and the Mekong (Asia).

Biodiversity

The most biodiverse biomes on the planet develop in the warm thermal zone, such as tropical forests, both rain forests and dry forests. Especially the Amazon rainforest, the Congo jungles and the jungles of Southeast Asia.

In this region there are also savannas that cover large areas in America and tropical Africa.

Flora

The greatest diversity of angiosperms is found in the warm zone, with endemic families such as Cactaceae, Rapateaceae, Bromeliaceae and Caricaceae.

Orchid (Dendrobium chameleon). Source: snotch from Sapporo, Hokkaido, Japan

In addition, other groups reach their greatest diversity in this area such as Orchidaceae, Palmae, Moraceae, Anacardiaceae, and the Mimosoideae of the Leguminosae.

Cultivated species

Among the cultivated species that have their origin in the warm zone are pineapple, cassava, papaya, cocoa, avocado and corn in America. While tropical Africa originated bananas, coffee and sorghum, and in Asia sugar cane and rice.

On the other hand, in the warm zone, but in a thermal floor tempered by the altitude, the tomato and the potato originated in America.

- Fauna

In the warm zone there is the greatest animal diversity as the fauna present in the tropical jungles and African savannas.

Amazon jungle

This jungle develops in the middle of the tropical or warm zone and there are various species of mammals. These include the howler monkey (Alouatta spp.) And the spider monkey (Ateles spp.), The tapir (Tapirus terrestris), the collared peccary (Pecari tajacu) and various species of rodents.

Tapir or Tapir (Tapirus terrestris). Source: Bernard DUPONT from FRANCE

The largest predator is the American tiger or jaguar (Panthera onca), but there are also other species of smaller felines.

Other widely represented groups are reptiles such as river turtles and snakes. Some species of snakes are poisonous, such as the pineapple (Lachesis muta) and the mapanare (Bothrops spp.) And others such as the anaconda (Eunectes murinus) are amphibious and hunt by constriction or drowning.

Among the birds, the harpy eagle (Harpia harpyja) and the condor of the Andes (Vultur gryphus) stand out. As well as the toucans (family of the ranfástidos) and the oriopendola or guacharaca (Ortalis ruficauda).

African savanna

These are extensive plains dominated by grasses with little or no tree cover. In them we find large herds of herbivores such as the wildebeest (Connochaetes taurinus), the zebra (Equus quagga), antelopes and gazelles.

The elephant (Loxodonta africana) and the giraffe (Giraffa camelopardalis) also inhabit the savanna. There are also carnivores such as the lion (Panthera leo), the leopard (Panthera pardus), the cheetah, the hyena (Crocuta crocuta) and the wild dog or lycaon (Lycaon pictus).

The primates

In the warm zone there are primates such as the gorilla (Gorilla spp.) And chimpanzees in the African forests (Pan troglodytes and Pan paniscus). While the orangutan (Pongo pygmaeus) lives in the jungles of Borneo, where it is threatened today.

Temperate zone

The Earth's temperate zone encompasses two latitudinal bands, one in the northern hemisphere and one in the southern hemisphere. In the northern hemisphere the temperate zone goes from the Tropic of Cancer to the line that defines the Arctic Circle. While in the southern hemisphere it extends between the Tropic of Capricorn and the line that marks the beginning of the Antarctic polar circle.

From the biogeographical point of view in this zone are the warm temperate and cold temperate life zones.

- Characteristics

In general terms, it is an intermediate zone between the hot and cold zones, not only geographically, but also in climate and biodiversity.

Weather

The temperate climate presents a seasonality made up of four well-defined seasons that are spring, summer, autumn and winter. During the summer the temperatures are high while in winter they are very low, with moderate temperatures in spring and colder in autumn.

The rains are less than in the warm zone and are concentrated in autumn and winter, precipitating in the form of rain or snow.

Floors

Given the equilibrium in temperature and precipitation, temperate zones are rich in deep and fertile soils, especially in areas of deciduous forest.

Water

The seas of the temperate zone present waters with temperatures lower than the warm zone and richer in nutrients. Although the diversity of species is lower than in the tropical zone, the populations are more numerous due to this greater availability of nutrients.

Its hydrographic basins are smaller in size and flow than tropical basins, due to the lower average annual rainfall.

Biodiversity

Although in the temperate zone the biodiversity is lower than in the tropical or warm zone, it also reaches very important levels. Especially the 5 zones of Mediterranean climate that exist in the extension of the temperate zone.

In addition to ecosystems such as the Mediterranean forest, this area has extensive areas of grasslands, especially in North America.

Coniferous forest in the Southern Hemisphere. Source: David

A characteristic of the temperate zone flora is that it has a great diversity of gymnosperms. In it, both gymnosperm (coniferous) and broadleaf (angiosperm) forests and mixed forests develop.

- Flora

The flora of the temperate zone has endemic families such as Fagaceae, especially the Quercus genus, whose species predominate in temperate broadleaf forests. Other characteristic genera of temperate deciduous forests are Fagus, Betula, Castanea and Carpinus.

In the southern hemisphere the genus Nothofagus of this family is characteristic. Among the families that reach their greatest diversity in the temperate zone are Rosaceae, Oleaceae and Cruciferae.

Gymnosperms

Gymnosperm forests include species of Pinaceae (Pinus, Abies, Cedrus, Sequoia) and Cupressaceae (Juniperus, Cupressus) in the Northern Hemisphere. While in the southern hemisphere, Pinaceae and Araucariaceae (Araucaria) predominate.

Cultivated species

The Mediterranean area is a very important center of origin and diversification of cultivated plants. Among the cultivated species from the temperate zone are the apple, pear, olive tree, vine and wheat.

- Fauna

This is the habitat of the brown bear (Ursus arctos) and the black bear (Ursus americanus). Likewise, the elk (Alces alces), the reindeer (Rangifer tarandus) and the deer (Cervus elaphus) are presented.

Moose (Alces alces). Source: Donna Dewhurst

Among the canids are the wolf (Canis lupus) and the fox (Vulpini spp.), While among the felines there are several species of lynx (Lynx spp.).

Birds also reach great diversity in the temperate zone, with species such as the stork (Ciconia ciconia). As well as various falconids and a large number of songbird species.

Domesticated species

The temperate zone is the center of domestication of the species that make up the cattle, sheep and pigs. Likewise, in this area poultry such as hen and turkey were domesticated.

Cold zone

The cold zone of the Earth also includes two latitudinal bands, in this case between 66 ° and 90 ° latitude. In the northern hemisphere the cold zone is limited to the Arctic Circle and in the southern hemisphere it is delimited in the Antarctic Polar Circle.

From the biogeographical and climatic point of view, the boreal or subpolar and polar or arctic life zones are found here.

- Characteristics

The cold zone covers the smallest total area and landmass. On the other hand, the growing season in this area of ​​the Earth is very short.

Weather

The cold climate is characterized by its extreme low temperatures, presenting long winters of up to 9 months. The minimum temperature in the Arctic reaches -50 ° C, and the maximum varies from 6 to 29 ° C. On the other hand, summers in Antarctica are colder, reaching averages of or 3 ° C.

Precipitation is scarce and falls in the form of snow and solar radiation is low. In the taiga, precipitation can reach 370 mm per year, but in the polar desert it does not exceed 110 mm.

In the cold zone, two zones are climatically defined: the subpolar, boreal or sub-arctic climate zone, and the polar or arctic climate zone. The first is characterized by presenting no more than 4 months a year with average temperatures above 10 ºC.

The polar zone is defined because the average temperature of the warmest month does not exceed 10 ºC.

Floors

The most outstanding characteristic of the cold zone soils is the presence of permafrost, which are soils with a permanently frozen layer. In areas with average temperatures below -5 ° C there is a continuous permafrost.

In the case of areas with temperatures between 0 ° C and -5 ° C, intermittent permafrost occurs during the year. On the other hand, much of the year the soils are covered with snow or ice, especially in Antarctica.

Water

The Arctic and Antarctic oceans are characterized by cold waters and a great wealth of marine fauna. For much of the year, vast ocean areas are covered by an ice sheet.

In this area most of the fresh water is in the form of ice and the rivers are frozen for much of the year.

Biodiversity

Taiga. Source: peupleloup

Due to extreme temperature conditions, the cold zone is the one with the least biological diversity on the planet. The characteristic biomes are the taiga or boreal forest and the tundra, an extensive herbaceous plain dominated by mosses and lichens.

- Flora

The Taiga

In the southern areas the taiga or boreal forest develops, where conifers predominate, with genera such as Pinus, Picea and Abies.

The tundra

It develops in the northernmost latitudes of the cold or polar zone. It is a large semi-desert area. Mosses (Sphagnum, Scorpidium), lichens (more than 1,000 species), sedges (Carex, Eriophorum) and grasses (Poa, Deschampsia) predominate in this area, with few shrubs.

- Fauna

Polar Circle

Seal (Phoca vitulina). Source: Andreas Trepte

Like the flora, the fauna in the cold zone is not very diverse, however species such as the polar bear (Ursus maritimus) inhabit. As well as marine mammals such as seals (Phocidae family) and sea lions (Otaria flavescens). Among the birds are several species of seabirds and penguins.

Boreal forest

The reindeer, the Arctic fox (Vulpes lagopus), the lemmings (Lemmini tribe), the musk ox (Ovibos moschatus) and the wolf inhabit these forests.

Reindeer domestication

The Sami people who inhabit Scandinavia and Russia have traditionally herded the reindeer and domesticated it as a draft animal for sledding.

References

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7. World Wild Life (Viewed Nov. 26, 2019). Taken from: worldwildlife.org.