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Ecoregion Description


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Species Richness


# of Endemic Species


Threats

618: Argun

Major Habitat Type:

temperate upland rivers

Author:

Nina Bogutskaya

Countries:

China; Mongolia; Russia

Boundaries:

This ecoregion includes the Argun’ [Ergun He] River drainage,  Uldz Gol River drainage, and lakes and marshes of the Barun-Torey and Zun-Torey depressions, which are now endorheic.

The southern border of the ecoregion follows the course of the Kerulen [Herlen Gol = Herlen He] River, which flows from the southern spurs of the Altan Ulugui Range [Altan Olgiy Nuruu]. In the east, the Bol’shoy Khingan Range [Da Hinggan Ling] divides the Middle Amur tributaries (ecoregion 617) and the Nen Jiang drainage (Songhua Jian ecoregion [620]) with the Khalkhin [Halhaiin] Gol, Haylar [Hailar He], and Gan He drainages (in the Argun’ River system). The northwestern border of the ecoregion follows the divide between the Shilka River and the Argun’ River drainages (Dutugtu Uul Range in the west and the Nerchenskiy Khrebet Range in the east).

Drainages flowing into:

Sea of Japan (eastern Pacific Ocean)

Main rivers or other water bodies:

The ecoregion includes the Argun’ River, Khalkhin [Halhaiin] Gol River, Haylar [Hailar He] River, Gan He River, Buir Nor [Buyr Nuur] Lake, Dalai Nor [Hulun Nur] Lake, Uldz Gol [Uldza] River, and Barun-Torey and Zun-Torey lakes and salt marshes.

The Argun’ River is mostly fed by a number of mountainous rivers that are similar to the sources of the Ingoda and Onon rivers (Shilka (Amur) ecoregion [619]). There are two large lakes, Buir Nor and Dalai [Hulun] Nor, in the upper Argun’. Buir Nor is an oval shape that is elongated from north to south. Its coasts are only slightly indented, and basically flat. Relatively steep coasts are only along the northeastern part of the lake. The lake is relatively shallow, with the average depth around 5 m. The deepest part is at the mouth of the Khalka [Halkyn-gol] River. The Orshon River flows from the lake, connecting it to the Dalai [Hulun] Nor. Along the eastern coast of the Buir Nor are several smaller isolated lakes with salty water. The Dalai [Hulun] Nor Lake is larger then Buir, and much deeper. The Kerulen [Herlen He] River flows into the southwestern end of the lake. The Dalai Nor is connected by a channel (called Mutnaya Protoka) with the Hailar River, and their confluence is the beginning of the Argun’ River, which receives almost no water from the Dalai Nor and Kerulen drainage. The total length of the Argun’ River (including Hailar) is about 1520 km, and the watershed is about 232,000 km2.

Topography:

The ecoregion occupies the most elevated part of the Amur basin (350-2500 m asl), which runs deep into the continent.

Climate:

The Upper Amur catchment (ecoregions 618 and 619) is different from the other part of the Amur basin by its geoclimatic conditions. It is characterized by less humidity and a severe continental climate.

Freshwater habitats:

The most peculiar features of the ecoregion are two big shallow lakes and a number of intermittent lakes and marshes in the Torey Depression. In general, rivers and lakes contain little water and lack high floods. By the end of summer some river sections become shallow. The  Torey lakes region, however, is characterized by an unusual system of underground water. As a result, it contains a number of small lakes that do not dry out even during the hottest and driest seasons, as well as a large pine-tree forest (400 km2) that grows on a waterless sandy valley. The beds of the Barun-Torey and Zun-Torey are periodically filled with water, with a total surface area of 800-900 km2 and depths up to 4-6 m.

Terrestrial Habitats:

Much of the ecoregion is characterized by the flat and rolling grasslands of the Mongolian-Manchurian grassland ecoregion and Daurian forest steppe ecoregion that stretch west from the Da Hingann Mountains (WWF 2001). The Da Hinggan-Dzhagdy Mountains conifer forests and East Siberian taiga occur in the east.

Fish Fauna:

The fish fauna of the Argun’ River drainage is typical for the Amur, but contains a relatively limited number of species. It lacks most migratory species characteristic of the Lower Amur. The ecoregion is most similar to the Shilka (Amur) ecoregion [619], differing from the latter by the presence of species in the genera Hypophthalmichthys, Saurogobio, and Lefua, and the absence of two species of Sarcocheilichthys, Gobio soldatovi tungussicus, Gobiobotia, Xenocypris, and Hemiculter leucisculus. In general, the ecoregion is characterized by the predominance of limnophylous species.

The occurrence of several cultrine cyprinids – which are typical of the Lower Amur and commonly considered to be conspecific – in the Buir Nor and Dalai [Hulun] Nor lakes is interesting from a taxonomic point of view. This is questionable since there are at least some minor external morphological differences judging from poor published data. A comparative study is urgently needed.

The species composition of the Kerulen and Torey parts of the ecoregion is relatively impoverished. Kerulen lacks most of the ecoregion’s lacustrine species. Shallow intermittent lakes of the Torey Depression, including the Ul’dza and Imalka tributaries, only support small-sized fishes such as Prussian carp (Carassius gibelio), Misgurnus mohoity, and Lefua pleskei  that are adapted to the difficult conditions within intermittent water bodies, or those that can escape to the upper reaches, such as Amur minnow (Phoxinus lagowskii) and Czekanowski’s minnow (P. Czekanowskii).

Description of endemic fishes:

Hemiculter varpachovskii, the only strict endemic species in the ecoregion, is a typical lacustrine cultrine cyprinid. It has been commonly considered to be conspecific with species that are mostly distributed in Lake Khanka and other parts of the Lower Amur drainage.

Other noteworthy fishes:

The species Lefua pleskei needs a special revision and may represent a distinct taxon. A comparison should be made with eightbarbel loach (Lefua costata) from Lake Dalai Nor (43.3 N 116.6 E isolated, south of Inner Mongolia=Nei Mongol Zizhiqu [NOT Dalai Nor=Hulun Nur in the Argun drainage]).

Ecological phenomena:

The lacustrine ecosystems of lakes Buir Nor [Buyr Nuur] and Dalai Nor [Hulun Nur] need further study; there may be a case of ecological parallelism (development of a pelagic fish assemblage) with Lake Khanka in the Lower Amur.

Evolutionary phenomena:

The Dalai [Hulun] Nor and Buir Nor lake systems and endorheic hollows of the Torey Lakes represent relict water bodies that remain from an ancient lacustrine plain which was located south of the main Transbaikalian centers of orogenesis. The study and revelation of probable relict forms in these lakes still lie ahead. It seems that cultrine species occurring in the lakes (e.g. Hemiculter varpachovskii) may represent distinct species or at least lineages that are phylogenetically distinct from those distributed in the Lower Amur.

Justification for delineation:

The ranges of the the Bol’shoy Khingan [Da Hinggan Ling], which stops monsoons, represent the orographic border of the upper part of the basin (so-called "Anikinskiy Porog" (Anikin Threshold). At the same time, the Argun’ ecoregion in the south is clearly different from the Shilka basin (618) in the north by the composition of the fish fauna. In general, the ecoregion is characterized by the predominance of limnophylous species.

Level of taxonomic exploration:

Poor; most species distributed in the Argun’ drainage need taxonomic revision, especially in comparison with paired forms from the Lower Amur in the genera Acanthorhodeus, Hemiculter, Chanodichthys, Misgurnus, Thymallus.

References/sources:

Bashlakov, Ya K. (1966)"Reasonable ways of study of water yield formation in the Transbaikalia" In Problems of geography and biology. (pp. 3-50) Chita: Chita State Pedagogical Institute.

Karasev, G. L. (1987). "Fishes of Transbaikalia" Novosibirsk: Nauka.

Karasev, G. L. (1974). "Reconstructions of fish fauna in Transbaikalia" Vopr. Ichthyol 14(2) 191-210.

World Wildlife, Fund (2001). "Terrestrial Ecoregions of the World" 2005 (2005; www.worldwildlife.org/science/ecoregions/biomes.cfm).

The Nature Conservancy World Wildlife Fund
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