The Tibetan Plateau, treeless except in the southeastern river valleys, supports a range of alpine vegetation types that includes meadow, steppe, cold desert and sub-nival cushion plant communities at elevations ranging from 3,500 to nearly 6,000 meters (m). Dry, cold, and expansive, the Tibetan Plateau possesses an alpine landscape of complex zonation with a general trend from moist alpine scrub to steppe vegetation to high, cold desert along a transect from southeast to northwest.
Location and General Description
The alpine deserts of northern Tibet include the lofty plateau that lies between the Karakoram and Kunlun mountain regions and extends eastward along the northern margin of the plateau. The Kunlun, a prominent mountain range of Central Asia, extends 2,500 kilometers (km) from east to west, connecting western Sichuan with the Pamir Range and forming the northern rim of the Tibetan Plateau. The Kunlun is truly remote. Its crest looks southward toward the highest and least densely populated part of this plateau and northward into the hyper-arid Tarim Basin. To the west, in the coldest, driest part of the Tibetan Plateau, even the lake basins exceed 5,000 m in elevation. Hard frosts occur nearly every night, year-round, and mean temperatures are below freezing for 9-10 months of the year. As a result of the sustained cold temperatures, extensive permafrost occurs in this area.
Precipitation is generally very sparse, in many areas only about 20 to 50 millimeters (mm) a year, all in the form of snow which melts and evaporates quickly in the intense sunlight. However, a more detailed look at precipitation patterns shows some variation. North slopes catch enough arctic moisture to support limited stands of spruce (Picea schrenkiana), and the highest elevations receive enough precipitation to create a winter snowpack that supplies productive oases at the foot of the mountains. Winds here are persistent and strong.
Because the Tibetan Plateau is gently inclined, with the highest elevations in the northwest, latitude and elevation jointly define a gradient of cooling temperatures from southeast to northwest. Latitude affects temperature by controlling the angle and intensity of solar radiation. Elevation affects temperature by controlling the air pressure and hence the heat capacity of the air.
The alpine zone in Tibet includes all areas where the average temperature during July, the warmest month of the year, is no more than 10oCelcius (C). In fact, almost all of the plateau except the southern river valleys–the Indus, Sutlej, and Tsangpo (including the Lhasa Valley)–falls within this "high cold" alpine zone. Within the alpine region, moisture determines whether a region supports meadow, steppe or alpine desert vegetation. As precipitation decreases northwestward, vegetation changes from dense scrub to meadow to steppe to desert. In Tibet, forests are confined to valleys. Forests never occur on the plateau due to cold, continental climate and the fact that the plateau lies above the 10o isotherm.
Soils are salty in many areas and underlain with permafrost. Plant cover is very sparse, less than 8 percent, and often as low as 1 to 2 percent. It comprises a high-cold desert community dominated by Ceratoides compacta, a thorny, densely branched cushion plant that grows on debris and gravel slopes up away from the cold, salty dry lake beds. Associated species include Pegeophyton scapiflorum and Hedina tibetica. There are few others.
According to Chang, "very low temperatures, very short or non-existent growing season, severe drought, high wind, and barren, rocky, and salty soil are typical ecological conditions for the high-cold desert plateau zone." The one woody plant which persists in these highlands, a species of tamarisk (Myricaria) that grows along riverbeds, holds all of its woody stems underground. Only the branchlets and minuscule leaves are exposed to form a dense cushion no more than 1 centimeter (cm) above ground.
Slopes above the lake basins support Carex compacta together with C. moorcroftii in a high cold steppe association. This slope vegetation is probably more robust due to temperature inversions in the lake basins, a pattern common to montane interior basins of western North America as well. A sparse subnival zone supports cushion plants like Saussurea gnaphaloides and Melandrium apetalum above 5,300 m. Permanent snowline is situated at 6,000 to 6,200 m.
A few small montane coniferous forest stands are found on the northern slopes of the Kunlun Mountain Range, overlooking the Tarim Basin at elevations of 2,700 to 3,600 m. Their total area is about 200 km2. The dominant tree is the spruce Picea schrenkiana with shrubby juniper in sunny sites.
Because the Kunlun and adjacent regions of Tibet have been uplifted recently (3,000 m in the past two million years), the high alpine environments here are geologically young and lack species that are deeply endemic. Moreover, the harsh environment limits biodiversity. About 700 species of vascular plants (245 genera) have been identified from the Kunlun, most at lower elevations, and the area records 21 large mammals and 150 bird species. Even so, plant species here include several phyto-geographical elements: Iran-Turanian (e.g. paleo-Mediterranean taxa like Ceratoides, Peganum, and Kalidium), Central Asian (e.g. montane desert taxa like Sympegma, Nitraria, Ajania, and Artemisia parvula, or alpine steppe taxa like the grasses Stipa and Festuca), and Tibetan (Stipa, Carex, Ceratoides compacta, and the alpine cushion plants Thylacospermum caespitosum, Arenaria bryophylla and Myricaria prostata).
In the eastern part of this ecoregion is Arjin Shan, one of China’s largest nature reserves at 45,800 km2. This expansive steppe desert landscape, at a lower elevation (4,200 m) than areas to the west, supports intact populations of many rare Tibetan mammals, including eleven species of ungulates. Wild yak (Bos grunniens) persists here as does Asiatic wild ass (Equus hemionus). Other species include Tibetan wild ass (Equus kiang), Tibetan antelope (Pantholops hodgsoni), Tibetan argali (Ovis ammon), Blue sheep (Pseudois nayaur), Tibetan gazelle (Procapra picticaudata). About 1,500 wild yaks probably occur in and around the Aru Basin in the western part of the Kunlun. Their predators, snow leopards (Uncia uncia), brown bears (Ursus arctos) and wolves (Canis lupus) also occur here at low density.
The western end of this ecoregion also contains an important nature reserve, Taxkorgan (14,000 km2) that supports the Marco Polo sheep subspecies of argali (Ovis ammon polii), Asiatic ibex (Capra ibex), and their predators. Another ungulate, Tibetan wild ass, appears to have been extirpated from this reserve. In general, Taxkorgan’s fauna shows an affinity to Central Asia while Arjin Shan supports large mammals that are endemic to the Tibetan Plateau.
Saline lakes at the fringes of the ecoregion serve as a staging and breeding area for migratory waterfowl such as the black-necked crane (Grus nigricollis) as well as the widespread, ground-nesting Tibetan snowcock (Tatraogallus tibetanus).
A single endemic mammal, Kozlov's pika (Ochotona koslowi) is found in this ecoregion. Based on limited biological surveys, the known distribution of Kozlov's pika is restricted to three regions, 1) the Valley of the Winds; 2) the juncture of the Kala and Kunlun Mountains, which is located south-east of Mount Kongke; and 3) in the Arjin Mountain Nature Reserve. The distribution is nearly continuous between Aqik Lake, Moon-tooth River and Rabbit Lake.
The limited spruce forests are vulnerable because they are small and grow very slowly, and should be protected by designating a nature reserve in the Uytag area.
Types and Severity of Threats
Wild mammals are subject to hunting pressure and competition from domestic livestock in the more productive locations closer to human habitation, while human pressure is still fairly low in the more remote areas. Management of the nature reserves needs to be improved in response to immigration and increased herding activities in these areas.
Justification of Ecoregion Delineation
This ecoregion covers roughly the Kunlun mountain range which is located on the northern edge of the Tibetan Plateau. The boundary is based on the CVMCC Vegetation Map of China classes alpine cushion vegetation, sparse alpine vegetation, and alpine meadow situated between the mountain range and the Tarim Basin. Farther to the south, the same classes of sparse alpine vegetation but with a higher proportion of alpine grassland are included in the Central Tibetan Plateau ecoregion. This ecoregion is comparable to the Kunlun Mountains biogeographic subunit in the Tibetan Plateau according to Mackinnon.
Additional information on this ecoregion
- For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
- To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
- World Wildlife Fund Homepage
- Chang, D.H.S. 1981. The Vegetation Zonation of the Tibetan Plateau. Mountain Research and Development 1(1): 29-48.
- Chinese Vegetation Map Compilation Committee (CVMCC). 1979. Vegetation map of China. Map (1:10,000,000). Science Press, Beijing, China. ISBN: 7030089561
- MacDonald, D., editor. 1999. The Encyclopedia of Mammals. Barnes and Noble Books. ISBN: 0199206082
- MacKinnon, J., Meng Sha, C. Cheung, G. Carey, Zhu Xiang and D. Melville. 1996. A Biodiversity Review of China. Worldwide Fund for Nature (WWF) International, Hong Kong.
- MacKinnon, J. 1996. Wild China. The MIT Press, Cambridge MA. ISBN: 0262133296
- Schaller, G.B. 1997. Tibet's hidden wilderness: Wildlife and nomads of the Chang Tang Reserve. Abrams. ISBN: 0810938936
- Schaller, G.B. 1998. Wildlife of the Tibetan Steppe. The University of Chicago Press, Chicago.ISBN 0226736539.
- Schaller, G.B, Li Hong, Lu Hua, Ren Junrang, Qiu Mingjiang and Wang Haibin. 1987. Status of Large Mammals in the Taxkorgan Reerve, Xinjiang, China. Biological Conservation 42: 53-71.
- Schaller, G.B, Li Hong, Lu Hua, Ren Junrang, Qiu Mingjiang and Wang Haibin. 1987. Status of Large Mammals in the Taxkorgan Reerve, Xinjiang, China. Biological Conservation42: 53-71.
- Zhang Baiping. 1995. Geoecology and Sustainable Development in the Kunlun Mountains, China. Mountain Research and Development 15(3): 283-292.
- Zhao, Ji. editor. 1990. Zheng Guangmei, Wang Huadong, Xu Jialin. The Natural History of China. McGraw Hill Publishing Company, New York. ISBN: 0002190435
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