Asia – plant geography
Farthest to the north, in Siberia, is the Arctic tundra with species-poor heaths and bogs. Further south is the gradual forest tundra (taiga) and coniferous forest. In Russia and Western Siberia the northern forest border is formed by an eastern breed of spruce and in Eastern Siberia by larch.
The boreal coniferous forest grows in a wide belt in central Siberia between approximately 45 ° and 70 ° and is dominated by spruce, pine, birch, elm and willow. The growth period is about three to five months and the annual rainfall is 350-700 mm; approximately 2/3 of the zone have permafrost, and large areas are covered by the marshes. The flora is uniform and relatively species-poor.
Deciduous forest occurs in Western Siberia as a mosaic between the coniferous forest in the north and the steppe in the south, but is found especially in the temperate parts of East Asia, i.e. in central and northeastern China and in most of Japan. These forests are richer in species than similar deciduous forests in Europe and North America, but are often dominated by species from the same genera, such as oak, chestnut, elm, ash, walnut, maple and linden. A number of genera, such as hickory, trumpet and tulip tree, occur in East Asia and North America, but disappeared from Europe during the ice ages. Many ornamental shrubs originate from the East Asian deciduous forest area, e.g. species of rose, cherry, lilac, Forsythia and Spiraea. To the north and in mountainous areas is a larger tinge of conifers. Above the tree line, species-rich alpine meadows are found in Japan and especially in China.
In southern Japan and the southern part of central China, the deciduous forests are becoming species-rich, evergreen forests with species from the families Lauraceae (laurel), Theaceae (tea), Magnoliaceae (magnolia) and Hammamelidaceae (witch hazel). Among the bare-seeded plants, some peculiar “living fossils” occur: Ginkgo (temple tree) and Metasequoia (spruce). Bamboo species can dominate locally. China is believed to have approximately 30,000 species of seedlings or almost three times as many as Europe. In most of the lowlands, the natural vegetation has been replaced by cultivated areas.
The Pontic-Central Asian region includes very large areas of steppe, semi-desert and desert from southern Ukraine and Russia through the Iranian highlands and Central Asia to the Pamir, Tibet and Gobi. The southern Russian black soil areas were previously characterized by grass steppes, which were often dominated by feather grass and had a rich spring flowering of bulbous plants, but they are now for the most part cultivated. The Iranian highlands and adjacent areas are dominated by steppes and semi-deserts with many thorny cushion plants in genera such as Cousinia and Astragalus. The area is relatively rich in species, e.g. there are approximately 9000 species of seedlings in Iran alone. The plateaus of the Pamir, Tibet, and Gobi are dry and barren; the species-poor vegetation is characterized by grasses, wormwood and species in the saltwort family. This family is also common in the salt-affected lowland areas north of the Caspian Sea.
In the eastern Himalayas (Sikkim), mountain rainforest grows at altitudes between approximately 900 and 2000 m; it contains both tropical elements such as screw palms and bamboo and northern temperate genera such as Castanopsis and Lithocarpus (from the beech family). The rainforest is replaced by a coniferous forest zone and in the fog zone (approximately 2600 to 4000 m) by Rhododendron scrub. In the alpine area there is a rich meadow vegetation with, for example, many species of cow dung and mountain heaths with low shrubs of barberry, juniper and species in the heather family. The vegetation boundary is about 5700 m above sea level.
According to countryaah, large parts of Southeast Asia are characterized by rainforests and monsoon forests, which are among the Earth’s most species-rich vegetation types. Important families are the screw palms, the ginger family, the dipterocarpus family and the fig family. The area is very rich in orchids, especially epiphytic species. Among epiphytic rainforest plants is also found the insectivorous Nepenthes. Pepper, cinnamon, mango, breadfruit and sago palm originate from here, and so do sugar cane and coconut palm. In drier areas, such as in the interior of Thailand, forests are deciduous; here grows teak. In the Philippines and New Guinea there is a certain Australian touch, e.g. Casuarina (iron wood) and Eucalyptus, on high mountains also species from genera that usually occur in northern temperate regions, e.g. buttercups and starlings. Along the Malabar coast of India is tropical rainforest with bamboo and palm trees. In large parts of the Indian Peninsula, the original vegetation is savannah-like with acacias and other genera in the pea flower family; in the northwest there are desert-like areas.
Asia – Climate
Large parts of Asia are far from the sea, and the continent is characterized by a continental climate with very large differences between summer and winter. This is especially true of Siberia, but also large parts of China and the rest of Central Asia; West Asia also has a continental climate. In South Asia, it is hot all year round, and seasonal differences are manifested by precipitation, rainy season and dry season. Around the equator there are areas completely without seasons (e.g. Singapore).
In winter, it is extremely cold in Siberia and Central Asia, and every winter a large and stable high pressure is formed here. In summer it is hot and the air pressure is usually low. These differences in air pressure are the cause of the winds’ characteristic change with the seasons: In summer, humid winds blow in over the continent, the summer monsoon, and in winter dry winds blow from the high pressure over the sea, the winter monsoon (see monsoon). It is especially southern and eastern Asia from India to Japan that is affected by these winds (“Monsoon Asia”).
The temperature variations in Asia are very large. The northeastern regions of Siberia are some of the coldest in the world in winter; the average January temperature in Ojmjakon is -50 °C. In the large coniferous forest area, the winter temperatures are -10 °C to -30 °C, and here there are short but warm summers. In the tropical regions of South Asia it is 25-30 °C most of the year, and in the Middle East some of the world’s highest temperatures reach above 50 ° C.
There are also large differences in precipitation, both the average annual precipitation and the distribution in months. The world’s rainiest region is located in Monsoon Asia. Cherrapunji in the Indian state of Meghalaya receives an average of 11,437 mm per year. This heavy rainfall falls in prolonged cloudbursts from April to August, while December and January are almost dry. Part of the rain falls in connection with powerful tropical cyclones, which form over the warm oceans and hit the coastal landscapes with destructive force. Almost every year, many people die in Bangladesh during the floods; the rest of Monsoon Asia is also regularly affected by these storms. The inland plateaus in eastern China, on the other hand, lie in rain, and here fall below 100 mm per year; The Himalayan mountains prevent the summer monsoon from reaching.
The effect of the thermal highs and lows is amplified by the high-lying jet streams. Eastward equatorial jet streams contribute some of the energy that triggers the very powerful summer monsoon, and in winter the shift of the global circulation pattern to the south causes subtropical western jet streams to form branches north and south of the Himalayan-Tibet. East of the highlands, they converge and strong dynamic high pressures occur, which together with the energy from the general thermal winter high pressure over the continent results in the dry NE monsoon.
Asia – wildlife
The majority of Asia, together with Europe, is the Palaearctic region. India and Baghdad with surrounding islands make up the Oriental region, while the southwestern part of the Arabian Peninsula belongs to the Afrotropic region. In the Palaearctic part of Asia, there are no major endemic groups due to the contact with Europe – and in earlier geological periods also with North America.
Along the Arctic coast there are several species of auks in large numbers. Here also live walruses and polar bears, which together with the polar fox and reindeer of the tundra are widespread throughout the North Pole (circumpolar). The bird life on the tundra is poor in species. In the taiga live wolves, brown bears and wolverines, mammals, which are also found in northern Europe, but in addition there are sable. Of birds, bull and lapland owl typical.
In the steppe and desert areas south of the taiga live steppe antelopes (saiga), steppe marmots, steppe squirrels and hamsters as well as birds such as stairs, larks and steppe eagles. Asia’s mountain ranges house numerous animal species within many animal groups, see Himalayas and the Caucasus.
In the deciduous forests of East Asia, the oriental fauna is beginning to make a serious impact with e.g. leopard and tiger; but the boundary between the Palaearctic and the Oriental region is fluid. In the mountains of northern Thailand, there are steelworms and bumble bees, which are typical representatives of the Palaearctic region, while the wildlife down in the valleys is distinctly oriental. Further west, the Himalayas draw a sharp boundary between the two regions.
In its species composition, the oriental part of Asia’s fauna is clearly different from the Palaearctic, but it has many similarities with the afrotropic fauna; Among the common animal groups that are not found elsewhere are rhinos, elephants, hyenas, rhinoceros birds and sunbirds. The species richness of South Asia’s rainforests is colossal, surpassed only by the fauna of South American forests.