51-733: The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas , and North Africa . The realm consists of several bioregions : the Euro-Siberian region; the Mediterranean Basin ; North Africa ; North Arabia ; and Western , Central and East Asia . The Palaearctic realm also has numerous rivers and lakes, forming several freshwater ecoregions. The term 'Palearctic'
102-477: A biodiversity hotspot . In Southeastern Asia, high mountain ranges form tongues of Palearctic flora and fauna in northern Indochina and southern China . Isolated small outposts ( sky islands ) occur as far south as central Myanmar (on Nat Ma Taung , 3,050 m; 10,010 ft), northernmost Vietnam (on Fan Si Pan , 3,140 m; 10,300 ft) and the high mountains of Taiwan . The realm contains several important freshwater ecoregions as well, including
153-546: A high carbon : nitrogen ratio make the leaves and branches of scleromorphic species long-lived in the litter, and can lead to a large build-up of litter in woodlands. The toxic compounds of many species, notably Eucalyptus species, are volatile and flammable and the presence of large amounts of flammable litter, coupled with an herbaceous understorey, encourages fire. All the Australian sclerophyllous communities are liable to be burnt with varying frequencies and many of
204-471: A lower CO 2 uptake than malacophyllous or laurophyllous leaves. These lower transpiration rates may reduce the uptake of toxic ions and better provide for C-carboxylation under nutrient-poor conditions, particularly low availability of mineral nitrogen and phosphate. Sclerophyllous plants are found in tropical heath forests, which grown on nutrient-poor sandy soils in humid regions in the Rio Orinoco and
255-721: A more summer-dominant rainfall, whereby falling under the humid subtropical climate zone ( Cfa / Cwa ). Furthermore, other areas with sclerophyll flora would grade to the oceanic climate ( Cfb ); particularly the eastern parts of the Eastern Cape province in South Africa, and Tasmania , Victoria and southern New South Wales in Australia. Sclerophyll plants are also found in areas with nutrient-poor and acidic soils, and soils with heavy concentrations of aluminum and other metals. Sclerophyll leaves transpire less and have
306-555: A much smaller area of the continent, being restricted to relatively high rainfall locations. They have a eucalyptus overstory (10 to 30 metres) with the understory also being hard-leaved. Dry sclerophyll forests are the most common forest type on the continent, and although it may seem barren dry sclerophyll forest is highly diverse. For example, a study of sclerophyll vegetation in Seal Creek, Victoria , found 138 species. Even less extensive are wet sclerophyll forests. They have
357-428: A taller eucalyptus overstory than dry sclerophyll forests, 30 metres (98 ft) or more (typically mountain ash , alpine ash , rose gum , karri , messmate stringybark , or manna gum , and a soft-leaved, fairly dense understory ( tree ferns are common). They require ample rainfall—at least 1000 mm (40 inches). Sclerophyllous plants are all part of a specific environment and are anything but newcomers. By
408-499: A very high biodiversity , are under great pressure from the population. This is especially true for the Mediterranean region since ancient times. Through overexploitation (logging, grazing, agricultural use) and frequent fires caused by people, the original forest vegetation is converted. In extreme cases, the hard-leaf vegetation disappears completely and is replaced by open rock heaths . Some sclerophyll areas are closer to
459-405: Is also one of the world's most endangered biogeographic regions; only 4% of the region's original vegetation remains, and human activities, including overgrazing , deforestation , and conversion of lands for pasture, agriculture, and urbanization, have degraded much of the region. Formerly the region was mostly covered with forests and woodlands, but heavy human use has reduced much of the region to
510-453: Is limited to the coastal western sides of the continents, but nonetheless can typical in any regions of a continent with scarce annual precipitation or frequent seasonal droughts and poor soils that are heavily leached. The sclerophyll zone often merges into temperate deciduous forests towards the poles, on the coasts also into temperate rainforests and towards the equator in hot semi-deserts or deserts. The Mediterranean areas, which have
561-499: Is particularly noticeable in the eucalypt and Melaleuca species which possess oil glands within their leaves that produce a pungent volatile oil that makes them unpalatable to most browsers. These traits make the majority of woody plants in these woodlands largely unpalatable to domestic livestock. It is therefore important from a grazing perspective that these woodlands support a more or less continuous layer of herbaceous ground cover dominated by grasses. Sclerophyll forests cover
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#1732772332416612-763: Is the broadest biogeographic division of Earth's land surface, based on distributional patterns of terrestrial organisms. They are subdivided into bioregions , which are further subdivided into ecoregions . A biogeographic realm is also known as "ecozone", although that term may also refer to ecoregions. The realms delineate large areas of Earth's surface within which organisms have evolved in relative isolation over long periods of time, separated by geographic features, such as oceans , broad deserts , or high mountain ranges , that constitute natural barriers to migration. As such, biogeographic realm designations are used to indicate general groupings of organisms based on their shared biogeography. Biogeographic realms correspond to
663-624: Is the same scheme that persists today, with relatively minor revisions, and the addition of two more realms: Oceania and the Antarctic realm . The Palearctic realm includes mostly boreal/subarctic-climate and temperate-climate ecoregions, which run across Eurasia from western Europe to the Bering Sea . The boreal and temperate Euro-Siberian region is the Palearctic's largest biogeographic region, which transitions from tundra in
714-539: The Bering land bridge , and have very similar mammal and bird fauna, with many Eurasian species having moved into North America, and fewer North American species having moved into Eurasia. Many zoologists consider the Palearctic and Nearctic to be a single Holarctic realm . The Palearctic and Nearctic also share many plant species, which botanists call the Arcto-Tertiary Geoflora . The lands bordering
765-671: The Cerrado biogeographic region of Bolivia , Paraguay and Brazil , and in the Mediterranean biomes that cover the Mediterranean Basin , California , Chile , and the Cape Province of South Africa . In the Mediterranean basin , holm oak , cork oak and olives are typical hardwood trees. In addition, there are several species of pine under the trees in the vegetation zone. The shrub layer contains numerous herbs such as rosemary , thyme and lavender . In relation to
816-563: The Holarctic realm . Following the nomenclatural conventions set out in the International Code of Area Nomenclature , Morrone defined the next biogeographic kingdoms (or realms) and regions: The applicability of Udvardy scheme to most freshwater taxa is unresolved. The drainage basins of the principal oceans and seas of the world are marked by continental divides. The grey areas are endorheic basins that do not drain to
867-500: The Mediterranean Sea in southern Europe, north Africa, and western Asia are home to the Mediterranean Basin ecoregions, which together constitute the world's largest and most diverse mediterranean climate region of the world, with generally mild, rainy winters and hot, dry summers. The Mediterranean basin's mosaic of Mediterranean forests, woodlands, and scrub are home to 13,000 endemic species. The Mediterranean basin
918-548: The Palearctic flora region include the holm oak ( Quercus ilex ), myrtle ( Myrtus communis ), strawberry tree ( Arbutus unedo ), wild olive ( Olea europaea ), laurel ( Laurus nobilis ), mock privet ( Phillyrea latifolia ), the Italian buckthorn ( Rhamnus alaternus ), etc. The sclerophyll regions are located in the outer subtropics bordering the temperate zone (also known as the warm-temperate zone). Accordingly,
969-651: The caribou ). Several large Palearctic animals became extinct from the end of the Pleistocene into historic times, including Irish elk ( Megaloceros giganteus ), aurochs ( Bos primigenius ), woolly rhinoceros ( Coelodonta antiquitatis ), woolly mammoth ( Mammuthus primigenius ), North African elephant ( Loxodonta africana pharaoensis ), Chinese elephant ( Elephas maximus rubridens ), cave bear ( Ursus spelaeus ), Straight tusked elephant ( Palaeoloxodon antiquus ) and European lion ( Panthera leo europaea ). Biogeographic realm A biogeographic realm
1020-423: The floristic kingdoms of botany or zoogeographic regions of zoology . From 1872, Alfred Russel Wallace developed a system of zoogeographic regions, extending the ornithologist Philip Sclater 's system of six regions. Biogeographic realms are characterized by the evolutionary history of the organisms they contain. They are distinct from biomes , also known as major habitat types, which are divisions of
1071-468: The sclerophyll shrublands known as chaparral , matorral , maquis , or garrigue . Conservation International has designated the Mediterranean basin as one of the world's biodiversity hotspots . A great belt of deserts , including the Atlantic coastal desert , Sahara Desert, and Arabian Desert , separates the Palearctic and Afrotropic ecoregions. This scheme includes these desert ecoregions in
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#17327723324161122-628: The temperate rain forests of the Euxine-Colchic deciduous forests ecoregion. Central Asia and the Iranian plateau are home to dry steppe grasslands and desert basins, with montane forests, woodlands, and grasslands in the region's high mountains and plateaux. In southern Asia the boundary of the Palearctic is largely altitudinal. The middle altitude foothills of the Himalaya between about 2,000–2,500 m (6,600–8,200 ft) form
1173-404: The 1960s, it was used originally in the field of biostratigraphy to denote intervals of geological strata with fossil content demonstrating a specific ecology. In Canadian literature, the term was used by Wiken in macro level land classification , with geographic criteria (see Ecozones of Canada ). Later, Schultz would use it with ecological and physiognomical criteria, in a way similar to
1224-708: The Earth's surface based on life form , or the adaptation of animals, fungi, micro-organisms and plants to climatic, soil , and other conditions. Biomes are characterized by similar climax vegetation . Each realm may include a number of different biomes. A tropical moist broadleaf forest in Central America, for example, may be similar to one in New Guinea in its vegetation type and structure, climate, soils, etc., but these forests are inhabited by animals, fungi, micro-organisms and plants with very different evolutionary histories. The distribution of organisms among
1275-455: The Mediterranean area since the Neolithic , which permanently changed the face of the landscape. In the sclerophyll regions near the coast, permanent crops such as olive and wine cultivation established themselves; However, the landscape forms that characterize the degenerate shrubbery and shrub heaths Macchie and Garigue are predominantly a result of grazing (especially with goats). In
1326-673: The Rio Negro basins of northern South America on quartz sand, in the kerangas forests of Borneo and on the Malay Peninsula, in coastal sandy areas along the Gulf of Guinea in Gabon, Cameroon, and Côte d'Ivoire, and in eastern Australia. Since water drains rapidly through these soils, sclerophylly also protects plants against drought stress during dry periods. Sclerophylly's advantages in nutrient-poor conditions may be another factor in
1377-842: The WWF system, the Australasia realm includes Australia , Tasmania , the islands of Wallacea , New Guinea , the East Melanesian Islands , New Caledonia , and New Zealand . Udvardy's Australian realm includes only Australia and Tasmania; he places Wallacea in the Indomalayan Realm, New Guinea, New Caledonia, and East Melanesia in the Oceanian Realm, and New Zealand in the Antarctic Realm. The Palearctic and Nearctic are sometimes grouped into
1428-425: The annual average temperatures are relatively high at 12–24 °C (54–75 °F); An average of over 18 °C (64 °F) is reached for at least four months, eight to twelve months it is over 10 °C (50 °F) and no month is below 5 °C (41 °F) on average. Frost and snow occur only occasionally and the growing season lasts longer than 150 days and is in the winter half-year. The lower limit of
1479-412: The boundary between the Palearctic and Indomalaya ecoregions. China , Korea and Japan are more humid and temperate than adjacent Siberia and Central Asia, and are home to rich temperate coniferous, broadleaf, and mixed forests, which are now mostly limited to mountainous areas, as the densely populated lowlands and river basins have been converted to intensive agricultural and urban use. East Asia
1530-643: The concept of biome . In the Global 200 /WWF scheme, originally the term "biogeographic realm" in Udvardy sense was used. However, in a scheme of BBC , it was replaced by the term "ecozone". The World Wildlife Fund scheme is broadly similar to Miklos Udvardy 's system, the chief difference being the delineation of the Australasian realm relative to the Antarctic, Oceanic, and Indomalayan realms. In
1581-492: The course of the last millennia, the original vegetation in almost all areas of this vegetation zone has been greatly changed by the influence of humans. Where the plants have not been replaced by vineyards and olive groves , the maquis was the predominant form of vegetation on the Mediterranean. The maquis has been degraded in many places to the low shrub heather, the garigue . Many plant species that are rich in aromatic oils belong to both vegetation societies. The diversity of
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1632-425: The dominant overstorey acacia species and a majority of the understorey acacias have a scleromorphic adaptation in which the leaves have been reduced to phyllodes consisting entirely of the petiole . Many plants of the sclerophyllous woodlands and shrublands also produce leaves unpalatable to herbivores by the inclusion of toxic and indigestible compounds which assure survival of these long-lived leaves. This trait
1683-815: The equator than the Mediterranean zone—for example, the interior of Madagascar , the dry half of New Caledonia , the lower edge areas of the Madrean pine-oak woodlands of the Mexican highlands between 800 and 1800/2000 m or around 2000 m high plateaus of the Asir Mountains on the western edge of the Arabian Peninsula . While the winter rain areas of America, South Africa and Australia , with an unusually large variety of food crops , were ideal gathering areas for hunter gatherers until European colonization , agriculture and cattle breeding spread in
1734-580: The heavily developed rivers of Europe , the rivers of Russia , which flow into the Arctic , Baltic , Black , and Caspian seas, Siberia 's Lake Baikal , the oldest and deepest lake on the planet, and Japan's ancient Lake Biwa . One bird family, the accentors (Prunellidae), is endemic to the Palearctic region. The Holarctic has four other endemic bird families: the divers or loons (Gaviidae), grouse (Tetraoninae), auks (Alcidae), and waxwings (Bombycillidae). There are no endemic mammal orders in
1785-480: The highly developed sclerenchyma from the plant, which is responsible for the hardness or stiffness of the leaves. This structure of the leaves inhibits transpiration and thus prevents major water losses during the dry season. Most of the plant species in the sclerophyll zone are not only insensitive to summer drought, they have also used various strategies to adapt to frequent wildfires , heavy rainfall and nutrient deficiencies. The type of sclerophyllic trees in
1836-536: The moderate annual precipitation is 300 mm (12 in) ( semi-arid climate ) and the upper limit 900–1,000 mm (35–39 in). Generally, the summers are dry and hot with a dry season of a maximum of seven months, but at least two to three months. The winters are rainy and cool. However, not all regions with sclerophyll vegetation feature the classic Mediterranean climate ; parts of eastern Italy, eastern Australia and eastern South Africa, which feature sclerophyll woodlands, tend to have uniform rainfall or even
1887-542: The northern reaches of Russia and Scandinavia to the vast taiga , the boreal coniferous forests which run across the continent. South of the taiga are a belt of temperate broadleaf and mixed forests and temperate coniferous forests . This vast Euro-Siberian region is characterized by many shared plant and animal species, and has many affinities with the temperate and boreal regions of the Nearctic realm of North America . Eurasia and North America were often connected by
1938-492: The ocean. According to Briggs and Morrone: According to the WWF scheme: Sclerophyll Sclerophyll is a type of vegetation that is adapted to long periods of dryness and heat. The plants feature hard leaves , short internodes (the distance between leaves along the stem) and leaf orientation which is parallel or oblique to direct sunlight. The word comes from the Greek sklēros (hard) and phyllon (leaf). The term
1989-718: The original sclerophyll vegetation in the world is high to extremely high (3000–5000 species per ha). Most areas of the Australian continent able to support woody plants are occupied by sclerophyll communities as forests , savannas , or heathlands . Common plants include the Proteaceae ( grevilleas , banksias and hakeas ), tea-trees , acacias , boronias , and eucalypts . The most common sclerophyll communities in Australia are savannas dominated by grasses with an overstorey of eucalypts and acacias. Acacia (particularly mulga ) shrublands also cover extensive areas. All
2040-630: The palearctic realm; other biogeographers identify the realm boundary as the transition zone between the desert ecoregions and the Mediterranean basin ecoregions to the north, which places the deserts in the Afrotropic, while others place the boundary through the middle of the desert. The Caucasus mountains, which run between the Black Sea and the Caspian Sea , are a particularly rich mix of coniferous, broadleaf, and mixed forests, and include
2091-551: The potential natural vegetation, around 2% of the Earth's land surface is covered by sclerophyll woodlands, and a total of 10% of all plant species on Earth live there. Sclerophyll woody plants are characterized by their relatively small, stiff, leathery and long-lasting leaves. The sclerophyll vegetation is the result of an adaptation of the flora to the summer dry period of a Mediterranean-type climate . Plant species with this type of adaptation tend to be evergreen with great longevity, slow growth and with no loss of leaves during
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2142-402: The prevalence of sclerophyllous plants in nutrient-poor areas in drier-climate regions, like much of Australia and the Cerrado of Brazil. The zone of the sclerophyll vegetation lies in the border area between the subtropics and the temperate zone , approximately between the 30th and 40th degree of latitude (in the northern hemisphere also up to the 45th degree of latitude). Their presence
2193-752: The region, but several families are endemic: Calomyscidae ( mouse-like hamsters ), Prolagidae , and Ailuridae ( red pandas ). Several mammal species originated in the Palearctic and spread to the Nearctic during the Ice Age , including the brown bear ( Ursus arctos , known in North America as the grizzly), red deer ( Cervus elaphus ) in Europe and the closely related elk ( Cervus canadensis ) in far eastern Siberia, American bison ( Bison bison ), and reindeer ( Rangifer tarandus , known in North America as
2244-531: The time of European settlement, sclerophyll forest accounted for the vast bulk of the forested areas. Most of the wooded parts of present-day Australia have become sclerophyll dominated as a result of the extreme age of the continent combined with Aboriginal fire use. Deep weathering of the crust over many millions of years leached chemicals out of the rock, leaving Australian soils deficient in nutrients, particularly phosphorus . Such nutrient deficient soils support non-sclerophyllous plant communities elsewhere in
2295-488: The unfavorable season. As a result, the thickets that make up these ecosystems are of the persistent evergreen type, in addition to the predominance of plants, even herbaceous ones, with "hard" leaves, which are covered by a thick leathery layer called the cuticle , that prevents water loss during the dry season. The aerial and underground structures of these plants are modified to make up for water shortages that may affect their survival. The name sclerophyll derives from
2346-553: The woody plants of these woodlands have developed adaptations to survive and minimise the effects of fire. Sclerophyllous plants generally resist dry conditions well, making them successful in areas of seasonally variable rainfall. In Australia, however, they evolved in response to the low level of phosphorus in the soil—indeed, many native Australian plants cannot tolerate higher levels of phosphorus and will die if fertilised incorrectly. The leaves are hard due to lignin , which prevents wilting and allows plants to grow, even when there
2397-449: The world and did so over most of Australia prior to European arrival. However such deficient soils cannot support the nutrient losses associated with frequent fires and are rapidly replaced with sclerophyllous species under traditional Aboriginal burning regimens. With the cessation of traditional burning non-sclerophyllous species have re-colonized sclerophyll habitat in many parts of Australia. The presence of toxic compounds combined with
2448-406: The world's biogeographic realms has been influenced by the distribution of landmasses , as shaped by plate tectonics over the geological history of the Earth . The "biogeographic realms" of Udvardy were defined based on taxonomic composition. The rank corresponds more or less to the floristic kingdoms and zoogeographic regions . The usage of the term "ecozone" is more variable. Beginning in
2499-405: Was coined by A.F.W. Schimper in 1898 (translated in 1903), originally as a synonym of xeromorph , but the two words were later differentiated. Sclerophyllous plants occur in many parts of the world, but are most typical of areas with low rainfall or seasonal droughts, such as Australia, Africa, and western North and South America. They are prominent throughout Australia , parts of Argentina ,
2550-756: Was first used in the 19th century, and is still in use as the basis for zoogeographic classification. In an 1858 paper for the Proceedings of the Linnean Society , British zoologist Philip Sclater first identified six terrestrial zoogeographic realms of the world: Palaearctic, Aethiopian/ Afrotropic , Indian / Indomalayan , Australasian , Nearctic , and Neotropical . The six indicated general groupings of fauna, based on shared biogeography and large-scale geographic barriers to migration. Alfred Wallace adopted Sclater's scheme for his book The Geographical Distribution of Animals , published in 1876. This
2601-501: Was not much affected by glaciation in the ice ages , and retained 96 percent of Pliocene tree genera, while Europe retained only 27 percent. In the subtropical region of southern China and southern edge of the Himalayas, the Palearctic temperate forests transition to the subtropical and tropical forests of Indomalaya , creating a rich and diverse mix of plant and animal species. The mountains of southwest China are also designated as
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