BIODIVERSITY IN CHINA
|Biodiversity Committee, CAS
BIODIVERSITY COMMITTEE OF THE CHINESE ACADEMY OF SCIENCES
2. HABITAT AND ECOSYSTEM DIVERSITY
Tropical seasonal rainforest dominated by Tetrameles nudiflora on limestone in Xishuangbanna.
China has a vast territory with complex climate, varied geomorphic types, a large river network, many lakes and long coastline. Such complicated natural conditions inevitably form diversified habitats and ecosystems. The terrestrial ecosystem can be divided into several types such as forest, tundra, marsh, etc. The aquatic ecosystem can be classified as marine, rivers and lakes.
The forested area of China is small with unbalanced distribution and variety of types. In total, it is approximately 11.5 million ha. with an average coverage about 12%. The proportion of forest coverage ranges from 55% to 4$ in different provinces.
Forest mainly has 212 formations indicated by the dominant species, co-dominant species or characteristic species in arbor layer. The bamboo forests of China are equally rich, with 36 formations. The shrublands are fairly complicated with 113 formations.
The forest of China can be roughly classified as coniferous forest, broad-leaved deciduous forest, and coniferous and deciduous mixed forest, etc.
The coniferous forest in China consists of taiga (44 types), warm temperate coniferous forest (5 types) and subtropical and tropical coniferous forest (27 types).
The temperate coniferous and deciduous broad-leaved mixed forest is mainly distributed in Northeast China.
Evergreen broad-leaved forest in Fanjingshan Mountain.
There are 42 main types of broad-leaved deciduous forest which are widely distributed over hilly areas and mid or lower mountainous areas in the temperate zone, the warm temperate zone and the subtropical zone of China. The broad-leaved deciduous forest is the zonal vegetation of the warm temperate zone.
The broad-leaved evergreen forest is composed of many broad-leaved evergreen tree species in the subtropical zone. Animals inhabiting this forest are in imminent danger of extinction due to habitat destruction.
Tropical seasonal rain forest and tropical rain forest covers a small area of Southern China. The 24 main types are dominated by more than one characteristic species. Tropical forests have been seriously destroyed especially on Hainan Island. To protect the remaining tropical forest is therefore a priority of conservation of ecosystem biodiversity in China.
The meadows are those communities which developed under appropriate moisture conditions. The dominant species are mesophytes and perennial plants. They can be divided into several types: typical meadows (27 formations), saline meadows (20 formations), marsh meadows (9 formations) and high cold meadows (21 formations). In total, there are 77 meadow formations.
Meadow-steppe in the Inner Mongolia.
Steppe consists of perennial xeric herbs, occurring from temperate to tropical zone. It is an ecosystem developed under certain hydrothermal conditions of semi-humid and semi-arid region. There are 45 formations of steppe, roughly classified as meadow steppe, typical steppe, desert steppe and high cold steppe. The steppe can be found in temperate semi-arid zones, such as the Qinghai-Xizang (Tibet) Plateau and the mountainous areas of arid regions with dominant species of Stipa, Festuca, Aneurolepidium, Cleistogenes and Artemisia respectively. The total area of temperate steppe in China is 315 million ha. Due to over exploitation and over-grazing, the steppe have deteriorated and the degenerative area has been estimated at 30% of the total.
Influenced by the warm air mass from the South China Sea and Indian Ocean, the tropical regions are covered with tropical forests, while the arid savanna can only be found in the xerothermic valley in the southern Yunnan and some parts of Hainan Island. In addition, some tropical forests felled repeatedly become secondary savanna.
The desert covers a total of 20% of landmass and is mainly found in northwestern region of the country. There are 52 formations of desert (small wood desert, shrub desert, small semi-shrub desert and cushion-like small semi-shrub desert).
It is a kind of wetland composed of helophytes, birds, birds, fishes and waterfowl. There are approximately 19 marsh formations which can be recognized as follows: herbaceous marsh 14, woody marsh 4 and peatbog one. Chinese mangrove (a tropical marsh forest), has 18 formations. The total area of marsh is about 11.5 million ha. It occurs in the mountainous area of Northeast, Sanjiang Plain and Qinghai-Xizang (Tibet) Plateau. The largest marsh is the Sanjiang Plain, Heilongjiang Province, now mostly reclaimed and turned into farmland. The remaining 2.27 million ha. are protected to some extent through establishment of some reserves.
In addition, there are 17 formations of tundra, alpine cushion-like and alpine mobile sand vegetation, with small distribution area.
2.7. Freshwater and Marine Ecosystems
Freshwater and marine ecosystem are homes to a tremendous diversity of fish, amphibians, invertebrates ,aquatic plants and microorganisms. The richness of biological diversity in coral reef could be sometimes compared with that of tropical forest. Marine ecosystems are far more diverse than terrestrial ones at higher taxonomic level, and marine organisms are highly diverse at the genetic level. Freshwater habitats are relatively discrete units causing hydro-biodiversity highly localized. Accordingly, freshwater ecosystems contains very high degree of endemism. Even though biodiversity is very high in freshwater and marine ecosystems, they are relatively little known. Scientists believe that the deep sea floor may contain as many as a million undescribed species.
Among numerous rivers, streams and lakes in China, there are 22 rivers longer than 1,000 km and 2,848 lakes larger than 1 km2. China is one of the largest producers of freshwater fish in the world. The silver carp (Hypophthalmichthys molitrix), bighead (Aristichthys nobilis) and grass carp (Ctenopharyngodon idellus) are well-known aquacultures. China is also rich in marine fish. There are 1,694 species recorded from China seas, consisting of 175 chondrichthyes and 1,519 teleosts. From the total of 2,804 fish species recorded, 440 are endemic.
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