|Asia has the richest flora of the earth’s seven continents|
Asia has the richest flora of the earth’s seven continents. Because Asia is the largest continent, it is not surprising that 100,000 different kinds of plants grow within its various climate zones, which range from tropical to Arctic.
Asian plants, which include ferns, gymnosperms, and flowering vascular plants, make up 40 percent of the earth’s plant species. The endemic plant species come from more than forty plant families and fifteen hundred genera.
Asia is divided into five major vegetation regions based on the richness and types of each region’s flora: tropical rain forests in Southeast Asia, temperate mixed forests in East Asia, tropical rain/ dry forests in South Asia, desert and steppe in Central and West Asia, and taiga and tundra in North Asia.
Tropical Rain Forests
The Asian regions richest in flora, tropical rain forests, are found in the island nations of Southeast Asia, which extend from Kinabalu in the north to Java in the south, and from New Guinea in the east to Sumatra in thewest. In this vast archipelago, the longest island chain between Asia and Australia, are thirty-five thousand to forty thousand vascular plant species.
Tropical rain forests grow there year-round because of the region’s warm temperatures and plentiful rainfall. The forests contain great varieties of tall trees, some towering 148 feet (45meters) high.Within any 1-square-mile area, one can see as many as one hundred tree species with no single species dominant.
The rain forests have mostly broad-leafed evergreens,with some palm trees and tree ferns. The upper most branches of the trees form canopies that cover and protect the earth below. Because little sunlight penetrates the dense canopies, few shrubs or herbs grow in the rain forests. Instead, many vines, lianas, epiphytes, and parasites are twined on tree branches and trunks. Mangroves fringe the tropical rain forests along the coasts.
Temperate Mixed Forests
|Asia temperate mixed forest|
Second in floral richness, East Asia’s temperate mixed forests contain thirty thousand to thirty- five thousand plant species. This region ranges from Japan in the east to the Himalayan nations (Bhutan, Sikkim, and Nepal) in the west, and from Russia’s Amur River Valley in the north to China’s Hainan Island in the south.
East Asia’s temperate weather is similar to the climate of eastern North America, with hot summers and cool winters. From south to north and from the east coasts to lower elevations in mountainous areas in the west, the vegetation changes from evergreen to deciduous broad-leafed forests, with dense shrubs, bamboo, and herbs in different layers beneath the forest canopy.
The major tree species are of the magnolia, oak, tea, laurel, spurge, azalea, and maple families. Herbs include members of the primrose, gentian, pea, carrot, foxglove, composite, buttercup, and rose families.
The Himalayan range is the point where the regions of South Asia, East Asia, and Central and West Asia join. From the Qinghai-Tibet Plateau in southwest China to the lower areas of the Himalayas, elevation usually is between about 5,000 and 13,000 feet (1,500 and 4,000 meters).
Mountains with deep valleys showcase complex, multiple vegetation types—from mixed forests and dense shrubs to alpine meadows in mountain plains. Many primary seed plants (gymnosperms and flowering plants), grow there.
Untouched native vegetation in East Asia is usually found only in mountainous or remote areas.On mountains at high elevations, the points where the temperatures are so cold that trees cannot grow form what is called the tree line.
Near the tree line, only plants related to coniferous and alpine species grow. Above about 13,000 feet (4,000 meters) in high mountain areas, no vegetation grows. Instead, snow caps or icebergs exist year-round.
Tropical Rain/Dry Mixed Forests
|Tropical Rain/Dry Mixed Forests|
The third-richest region, tropical rain/dry forests, is found in South-Asia, which reaches from the Philippines in the east to Pakistan in the west, and from the Himalayas in the north to Thailand in the south. Twenty-five thousand to thirty thousand species of plants grow there.
This region has both tropical rain forests and tropical seasonal dry forests. The tropical rain forest is mainly found in the region’s lowlands and the seasonal dry forests in the highlands or mountainous areas. More often, these two types of forests are combined.
The tropical seasonal dry forests usually grow in a climate with wet and dry seasons or under a somewhat cooler climate than the tropical rain forests. The canopy, formed from primarily deciduous broad-leafed species, is much thinner than the canopy in the tropical rain forest, so more sunlight reaches plants below.
Many different plant species live together, forming tropical jungles. Tall, thick-trunked trees, colorful orchids, ferns, dense mosses, and twined vines and lianas dominate this vast region.
The major components of these kinds of forests are members of the dipterocarpas, sweetsop, laurel, piper, fig, dissotis, akee, gardenia, periwinkle, milkweed, African violet, palm, and aroid families. In central and southern India and in some areas of Pakistan there are tropical grasslands, called the savanna. Because of the savanna’s hot, dry weather, mainly coarse grasses grow there.
Desert and Steppe
The desert and steppe region in Central and West Asia has twenty to twenty-five thousand species of plants. This region stretches from north and northwest China and Mongolia in the east to Turkey in the west, and from Kazakhstan in the north to the Arabian Peninsula in the south. This region’s vegetation changes from semi desert or desert to the temperate grassland called the steppe.
Central and West Asia contains the largest desert-steppe landscape in the Northern Hemisphere. Few plant species grow in the steppe and nearly none in the desert. The herbs and fewwoody plants that grow in these dry areas are members of the grass, pink, mustard, pea, saxifrage, stonecrops, lignum vitae, forget-me-not, and lily families. Because the desert environment is so dry, plant species must be able to survive in the arid weather for long periods of time.
Central and West Asia—with its steppe between the desert in the south and coniferous forests in the north—forms one of the world’s largest foraging areas, providing food resources for both wild and domestic animals, such as camels, sheep, goats, cows, and horses.
Taiga and Tundra
|Taiga and Tundra|
The poorest region in floral richness, with only about five thousand vascular plant species, is North Asia. This region is primarily Siberia, the eastern part of Russia, reaching from the Ural Mountains in the west to the Bering Strait in the east and from the Arctic Circle in the north to Mongolia and Kazakhstan in the south.
The region’s weather is temperate, with short, mild summers and long, cold winters. The predominant vegetation in North Asia is coniferous (boreal) forest. This region, called the taiga, contains mainly pine, spruce, fir, larch, and some species in the birch, aspen, and willow families.
Because the trees there are straight and tall, the taiga provides timber for Russia’s forestry industry. Small, perennial herbs and a few types of shrubs grow in the taiga’s swamps or marshes. Farther north is the cooler Arctic area called the tundra. Plants that grow in tundra are resistant to the cold climate.
During the summer they complete their life cycle quickly, before winter comes. Tundra plant species are members of such common families as composites, peas, grasses, and reeds. Far beyond the tundra is Arctic ice.
Asia’s native plant species provide shelter and food for animals. For example, arrow bamboo and umbrella bamboo, found in the forests of central to southwest China, are the main food of the giant panda. Many plants in Asia also provide food, ornaments, or medicine for humans.
Rice is the main food for humans in Asia, especially in the tropics. In temperate Asia, wheat—one of the world’s main food sources—joins rice as a primary food source. Various beans and peas provide plant protein in the human diet and are eaten with vegetables and grains.
Asia has many tropical fruit plants, such as the mango, banana, litchi, citrus fruits, and breadfruit. Pears, apples, grapes, peaches, and strawberries are temperate fruits. The kiwi, one of the most nutrient-rich fruits, is cultivated in New Zealand but originally came from central China. The Chinese not only eat kiwi but also make kiwi wine.
Palm dates are another important fruit in West and Southwest Asia (the Arabian Peninsula). Vegetables grown in Asia include various cabbages, lettuce, onions, garlic, celery, carrots, soybeans, cucumbers, and squash. Ginger originally came from Asia.
Soybean oil is the major cooking oil in Asia. Although soybeans are native to Asia, they have become the biggest crop grown in the United States. According to the U.S. Department of Agriculture, in 1999 U.S. farmers harvested 73.3 million acres of soybeans, 2.3 million acres more than corn and 18.6 million acres more than wheat.
Another oil plant, the sunflower, is grown in temperate Asia. In tropical Asia, people use mustard oil, palm oil, cotton oil, and peanut oil. In Central and West Asia, the most popular oil is olive oil. Many other foods people enjoy throughout the world are native Asian plants, for example, tea and coconuts. Black pepper and sugarcane also are grown in tropical Asia.
Ornamental and Medicinal Plants
Many of Asia’s plant species have great ornamental value. Azaleas, dogwood, primroses, camellias, peonies, roses, lotus, daisies, cherries, and begonias are frequently planted in gardens. Ornamental conifers from Asia include pines, spruces, cedars, junipers, umbrella pines, and yews.
Thousands of wildflowers originating in Asia include poppies, snapdragons, slippers, columbine, trillium, marigolds, buttercups, gentian, lilies, bluebells, and violets. Europeans who explored Asia centuries ago brought ornamental plants back to their home countries.
As a result, many of these plants are now grown throughout the world. The world’s largest flower, rafflesia, grows in the tropical rain forests of Sumatra. In full bloom, the flower’s diameter is about 3 feet (1 meter).
Plants make up a large part of traditional Chinese medicine, which has been practiced for thousands of years. Today, some of these plants are used in alternative medicine in the West. They include ephedra, eucommia, cinnamon, ginseng, sanqi, and ginkgo.
Ancient species include such gymnosperms as the dawn redwood of central China. Dawn redwood is similar to California’s redwood and giant sequoia. Another fossil-like tree is East Asia’s ginkgo. This species not only has great ornamental value but also has great commercial value as an alternative medicine.
Ginkgo trees are also dust- resistant, which makes them a favorite in urban landscaping and the ornamental industry. Other Asian plants such as the magnolia and its allied families may represent the most primitive flowering plants.
Asian flora today also includes introduced plant species from other parts of the world that play important roles in people’s lives. For example, the rubber tree of South America is cultivated in tropical Asia.
This tree produces raw material for the natural rubber industry, in which Asia is the largest producer in the world. Cacao, a tree species that provides the basis of chocolate, was introduced from tropical America. Corn, one of the most common crops in Asia, was introduced from America several thousand years ago.
Several vegetables, including the tomato, potato, eggplant, green pepper, hot pepper, and chili (all from the nightshade family), were introduced to Asia long ago. Peanuts, originally from Brazil, are also cultivated in Asia.
Coffee, an increasingly popular beverage in Asia, came originally from Africa. An introduced fruit is the pineapple, which came from tropical America but now is popular in tropical Asia. The sweet potato, from Central America, is also cultivated in Asia. Tobacco is another crop introduced to and cultivated in Asia. It originally came from tropical America, but its yield in China has made that nation a leading producer.
Impact of Human Activity
Asia’s highly diversified flora have contributed positively to the daily lives of people around the world, but the demands of a rapidly growing population are a constant threat. Deforestation, overgrazing, and urbanization have become major reasons for heavy losses of Asian flora, especially in South and East Asia.
In China alone, eight key plant species were added to the first-class protection list in the Red Book of 1992 (equivalent to the U.S. endangered species list). Among the mare the Chinese silver fir, dawn redwood, and ginseng.
These plants only grow in several isolated locations and are rare in their original range. As natural vegetation is cut for farming, grazing, or simply for cooking and heating fuel, fewer plants remain. Although scientists from around the world have worked on this problem for decades, the situation has not improved.