Tarim Basin deciduous forests and steppe | |
---|---|
Ecology | |
Realm | Palearctic |
Biome | temperate broadleaf and mixed forests |
Borders | Taklimakan desert |
Geography | |
Area | 54,533 km2 (21,055 sq mi) |
Countries | China |
Autonomous region | Xinjiang |
Conservation | |
Conservation status | Critical/endangered |
Protected | 4,051 km2 (7%) [1] |
The Tarim Basin deciduous forests and steppe is a temperate broadleaf and mixed forests ecoregion in the Xinjiang Uyghur Autonomous Region of western China. The ecoregion includes deciduous riparian forests and steppes sustained by the region's rivers in an otherwise arid region.
The Tarim Basin is a desert basin lying in westernmost China. The basin is surrounded by high mountains – the Kunlun Mountains to the south, which form the northern edge of the Tibetan Plateau; the Pamir Mountains to the west; and the Tian Shan to the north.
The basin is arid, but the surrounding mountains receive considerable rainfall and snow. Rivers drain into the basin from the mountains, including the northward-flowing Hotan River, which drains the western Kunlun Mountains, the Yarkand River, which drains the Pamirs, and the Aksu River, which drains the western Tian Shan mountains. These rivers join to form the Tarim River, which flows for 1300 km in an arc across the northern and eastern basin. The Kongque River drains southeastwards from the central Tian Shan. The basin is endorheic, with no outlet to the sea, and Tarim River and Kongque rivers empty into a complex of salt lakes in the eastern portion of the basin. The lower Tarim River empties southeast into Taitema Lake in the southeastern basin, and the Kongque empties eastwards into Lop Nur. The Qarqan River rises in the central Kunlun Mountains and also empties northeastwards into Taitema Lake. Taitema Lake is approximately 800 meters above sea level. [2]
Soils in the ecoregion are generally sandy loam.
The basin has an arid continental climate. Average annual temperatures range from -20º C in the winter months to 40º C during the summer months. Rainfall averages only 50 mm per year on the floor of the basin. Annual precipitation in the surrounding mountains can exceed 1000 mm per year. The rivers are sustained snowfall and glacial melt (about 60% of total flow) and by rainfall (about 40%). [2] About 75% of the annual runoff comes in the months of July, August and September, creating an regular summer flood season. [3]
The natural vegetation includes wetland, riparian forest, and shrub communities. In seasonally and permanently-flooded areas there are reed swamps and wet meadows of Myricaria pulcherrima, Phragmites australis , and Calamagrostis pseudophragmites . The riparian forests, known as Tugay, are dominated by the deciduous desert poplar (Populus euphratica) on the lower river terraces, along with Elaeagnus angustifolia . The upper river terraces are home to drier forests and shrubby woodlands, with Tamarix ramosissima and Halostachys caspica along with Populus euphratica and salt-tolerant halophyte plants. Populus pruinosa occurs along the upper reaches of the rivers, but not in the lower basin. [3]
The forests and wetlands are important habitat for migratory and resident birds. The ecoregion is home to several mammal species, including Yarkand deer (Cervus elaphus yarkandensis). The Yarkand deer population declined from 10,000 individuals in the 1950s to less than 3000 in the 1990s. [2]
The Silk Road passes through the Tarim Basin, and the region's rivers have supported settled and nomadic people for centuries. Much of the river lowland has been converted to agriculture and pasture. Since the 1950s, the Chinese government has settled many people in the area from elsewhere in China, and the region's growing population accelerated conversion of habitat, draining wetlands, and diverting water for agriculture. Water diversion has both reduced flows in the river and lowered the groundwater table, endangering the forests. [4]
Since 1921 the Tarim has been diverted via the Kongque into Lop Nur, and freshwater flows to the 320 km of the lower Tarim and Taitema Lake were much reduced. Construction of Daxihaizi Dam in 1972 mostly eliminated freshwater flows into the lower Tarim. Most of the forest died off, and wildlife, including wild camels, was decimated. [2] In 2000, the government started regular water releases from the upstream dams into the lower Tarim, which allowed the forests, wildlife, and groundwater to recover somewhat. [5]
A 2017 assessment found that 4,051 km2, or 7%, of the ecoregion is in protected areas. Very little habitat remains outside protected areas. [1] Tarim Huyanglin Nature Reserve, established in 1983, protects the largest remaining block of habitat on the Tarim River, including an un-dyked stretch of river in the western portion of the reserve where natural river processes still prevail. [3]
The Tian Shan, also known as the Tengri Tagh or Tengir-Too, meaning the "Mountains of God/Heaven", is a large system of mountain ranges in Central Asia. The highest peak is at the Jengish Chokusu at 7,439 metres (24,406 ft) high. Its lowest point is at the Turpan Depression, which is 154 m (505 ft) below sea level.
Lop Nur or Lop Nor is a now largely dried-up salt lake formerly located in the eastern fringe of the Tarim Basin in the southeastern portion of the Xinjiang Autonomous Region, northwestern China, between the Taklamakan and Kumtag deserts. Administratively, the lake is in Lop Nur town, also known as Luozhong of Ruoqiang County, which in its turn is part of the Bayingolin Mongol Autonomous Prefecture.
The Tarim River, known in Sanskrit as the Śītā, is an endorheic river in Xinjiang, China. It is the principal river of the Tarim Basin, a desert region of Central Asia between the Tian Shan and Kunlun Mountains. The river historically terminated at Lop Nur, but today reaches no further than Taitema Lake before drying out.
The Tarim Basin is an endorheic basin in Xinjiang, Northwestern China occupying an area of about 888,000 km2 (343,000 sq mi) and one of the largest basins in Northwest China. Located in China's Xinjiang region, it is sometimes used synonymously to refer to the southern half of the province, that is, Southern Xinjiang or Nanjiang, as opposed to the northern half of the province known as Dzungaria or Beijiang. Its northern boundary is the Tian Shan mountain range and its southern boundary is the Kunlun Mountains on the edge of the Tibetan Plateau. The Taklamakan Desert dominates much of the basin. The historical Uyghur name for the Tarim Basin is Altishahr, which means 'six cities' in Uyghur. The region was also called Little Bukhara or Little Bukharia.
Dzungaria, also known as Northern Xinjiang or Beijiang, is a geographical subregion in Northwest China that corresponds to the northern half of Xinjiang. Bound by the Altai Mountains to the north and the Tian Shan mountain range to the south, Dzungaria covers approximately 777,000 km2 (300,000 sq mi), and borders Kazakhstan to the west and Mongolia to the east. In contexts prior to the mid-18th century Dzungar genocide, the term "Dzungaria" could cover a wider area, coterminous with the Oirat-led Dzungar Khanate.
The Yarkand River is a river in the Xinjiang Uyghur Autonomous Region of western China. It originates in the Siachen Muztagh in a part of the Karakoram range and flows into the Tarim River or Neinejoung River, with which it is sometimes identified. However, in modern times, the Yarkand river drains into the Midstream Reservoir and exhausts its supply without reaching the Tarim river. The Yarkand River is approximately 1,332.25 km (827.82 mi) in length, with an average discharge of 210 m3/s (7,400 cu ft/s).
Altyn-Tagh is a mountain range in Northwestern China that separates the Eastern Tarim Basin from the Tibetan Plateau. The western third is in Xinjiang while the eastern part forms the border between Qinghai to the south and Xinjiang and Gansu to the north.
The Yarkand deer, also known as the Tarim deer or Lop Nor stag, is a subspecies of the Central Asian red deer that is native to the province of Xinjiang, China. It is similar in ecology to the related Bactrian deer in occupying lowland riparian corridors surrounded by deserts. Both populations are isolated from one another by the Tian Shan Mountains and probably form a primordial subgroup of the Central Asian red deer.
The Eurasian Steppe, also called the Great Steppe or The Steppes, is the vast steppe ecoregion of Eurasia in the temperate grasslands, savannas and shrublands biome. It stretches through Hungary, Bulgaria, Romania, Moldova, Ukraine, southern Russia, Kazakhstan, Xinjiang, Mongolia and Manchuria, with one major exclave, the Pannonian steppe, located mostly in Hungary.
The Yarkand hare is a species of mammal in the family Leporidae. It has soft, straight, sandy brown dorsal pelage which has grayish-black stripes, and completely white ventral pelage. Endemic to China, the Yarkand hare is restricted to the Tarim Basin in Southern Xinjiang, China. It is mainly nocturnal, and forages on grass and crops. The female produces two or three litters annually, each consisting of two to five young. It is rated as near threatened on the International Union for Conservation of Nature Red List of Endangered Species and by the Red List of China's Vertebrates. However, Chinese geneticists have stated the species is "endangered" due to limited habitat and its fragmentation, and over-hunting and poaching.
The Kaidu River, also known under its ancient name Chaidu-gol, is a river in the Xinjiang Uyghur Autonomous Region of China and an important source of water for the region. The Kaidu River is responsible for many substantial effects on the environment. Affecting the land and its people in many different ways.
The Keriya River is a river in the province of Xinjiang in China. It flows for 519 km (322 mi) from the Kunlun Shan mountain range north into the endorheic Tarim Basin, but is lost in the desert several hundred kilometers south of the Tarim River. The only major settlement along the river is Keriya Town, east of Hotan. The river is an important source of irrigation water and also supplies historically important oases along its course. Its drainage basin covers about 7,358 km2 (2,841 sq mi).
Tugay is a form of riparian forest or woodland associated with fluvial and floodplain areas in arid climates. These wetlands are subject to periodic inundation, and largely dependent on floods and groundwater rather than directly from rainfall. Tugay habitats occur in semi-arid and desert climates in Central Asia. Because Tugay habitat is usually linear, following the courses of rivers in arid landscapes, Tugay communities often function as wildlife corridors. They have disappeared or become fragmented over much of their former range.
Populus euphratica, commonly known as the Euphrates poplar, desert poplar, diversiform-leaved poplar, or poplar diversifolia, is a species of poplar tree in the willow family.
Altun Shan National Nature Reserve is a large, arid area in the southeast of Xinjiang Autonomous Region, on the northern edge of the Tibetan plateau and the southern edge of the Tarim Basin in northwest China. It surrounds the Kumkol Basin, an endorheic basin in the western third of the Altyn-Tagh mountains. The reserve is sometimes referred to as the "Arjin Mountains Nature Reserve", or "Aerjinshan". The reserve covers the southern portions of Qiemo County and Ruoqiang County of Bayingolin Mongol Autonomous Prefecture in Xinjiang.
Bayanbulak Grassland National Nature Reserve is the second largest grassland in China, located in the Bayanbulak Basin of the Tian Shan mountains in northwest China. The terrain is mostly flat, and encompasses a middle section of the Kaidu River. The reserve is 200 km northwest of Korla in Bayingolin Mongol Autonomous Prefecture of Xinjiang Uyghur Autonomous Region.
The Tian Shan montane steppe and meadows ecoregion covers a 2,000 km long stretch of grasslands of the isolated Tian Shan mountains of Central Asia. It is characterized by high-altitude flat and rolling grasslands.
The Tian Shan foothill arid steppe ecoregion covers the northern and western approaches to the Tian Shan mountains, centered on Lake Issyk-Kul in Kyrgyzstan. This region receives more moisture from Central Asia, thereby supporting more vegetation and diversity of plant and animal species than the deserts to the south.
The Central Asian riparian woodlands ecoregion is spread out across the deserts and plains of central Asia between the Aral Sea and the mountains 2,000 kilometres (1,200 mi) to the east. The long narrow components of the ecoregion follow the large rivers fed by snowmelt, and provide critical habitat for migratory birds as they travel through the arid region. The vegetation is referred to as tugai, characterized by low tangles of trees and brush along the edges of the rivers and associated wetlands, and fed by groundwater instead of precipitation.