Location and General Description
The basin of the Nenjiang River is enclosed by low mountains, the Large Hinggan to the west and the Little Hinggan to the north. Higher mountains that form the base of the Korean Peninsula define the southern margin of the plain. The whole region drains into the East Sea (Sea of Japan) through the Songhua River, a major tributary of the Amur River of the Russian Far East.
Soils in the basin have been deposited from rivers and lakes throughout the Quaternary. These tend to be poorly drained, creating swampy, sometimes saline conditions in the low-lying areas. Boggy peat soils are present in some areas. Westward, this swampy landscape undergoes a transition to the drier steppes of the Hinggan foothills.
The climate here is continental monsoon climate and is warmer and drier than in the surrounding mountains with mean annual precipitation of 400 to 450 mm.
Typical vegetation in the lowlands of the Nenjiang River Basin consists of a distinctive coniferous swamp forest interspersed among meadows dominated by grasses and sedges. Forests are dominated by the larch (Larix gmelini ssp. olgensis) which may grow through a lower story of birch (Betula japonica). Meadows are dominated by grasses such as (Calamagrostis epigeios) and (C. langsdorfii) that are adapted to grow in flooded soils. These often grow as dense tussocks that emerge from the flooded areas. Lakes are often filled or lined at the margin by the salt-tolerant reed, Phragmites communis.
The basin contains extensive flooded grassland areas, typified by the landscapes contained within its two largest nature reserves, Zhalong (in Heilongjiang Province) and Momoge (in Jilin Province). Among the flooded meadows are shallow, reed-filled lakes, rivers and old river courses undergoing ecological succession to grassland. Lakes may be either fresh or brackish, and salt concentrations are increasing in many areas as a result of fresh water diversions for agriculture.
Two large nature reserves protect wetland habitat in this ecoregion. Zhalong Nature Reserve (2,100 km2), located in the lower drainage basin of the Wuyur (Ulun) River, is a vast complex of permanent and seasonal freshwater marshes with numerous shallow lakes and ponds and extensive reed beds (Phragmites spp.). Extensive flooding occurs during the spring and summer rainy season.
Zhalong serves as a wetland breeding area for bird species such as the rare red-crowned crane (Grus japonensis) and Chinese merganser (Mergus squamatus). In addition to flooded grasslands, the reserve includes a network of freshwater reed marshes (400 km2) that line or fill numerous small lakes and ponds. Natural lakes are mostly permanent freshwater, although some are seasonal or saline. During the April-June breeding season, productivity is high, with abundant fish, frogs, mollusks and aquatic insects, making this an ideal breeding area for waterfowl.
More than 200 bird species have been recorded here, including at least six of the world’s 15 crane species. The four species that breed here include red-crowned crane (Grus japonensis), white-necked crane (G. vipio), Siberian crane (G. leucogeranus), and Damoiselle crane (Anthropoides virgo), while two species stage here prior to migrating to their breeding habitat, the common crane (G. grus) and hooded crane (G. monachus). Other rare bird species that breed here are white stork (Ciconia ciconia), black stork (C. nigra), Oriental white ibis (Threskiornis aethiopicus melanocephalus), Mandarin duck (Aix galericulata), and white spoonbill (Platalea leucorodia). This wetland habitat, together with the surrounding grassland, was declared a Ramsar site in 1992. It serves as a Chinese center for research on cranes, a bird revered in China as a symbol for long life.
Zhalong also supports 42 fish species, and the amphibians Bufo raddei, Hyla arborea, Rana nigromaculata, and R. temporaris. The frog, R. amurensis, is a protected amphibian that inhabits this area. A few small nature reserves such as Heilonggong and Shanhe have been established to protect this species.
Momoge Nature Reserve (1,440 km2) serves as a breeding and staging ground for six crane species, an estimated 2,000 individuals overall, including red-crowned crane, Siberian crane, white-necked crane and Damoiselle crane. Other rare birds that breed here are great bustard (Otis tarda) and white stork (Ciconia ciconia). The area is thought to have potential for ecotourism and outdoor recreation, but is threatened by pollution as well.
Zhalong Nature Reserve and other areas of wetland habitat in the Nenjiang River Basin have been threatened for many years by overfishing and encroachment by agriculture. However, many reserves have been put into place to protect the rare and endangered bird species of this ecoregion.
Types and Severity of Threats
Disruptive activities include collecting reeds, hunting, and collecting bird eggs. Salinization has become a problem in some areas. This occurs when demand for irrigation water is so high that insufficient fresh water passes through the system to thoroughly flush out the salt. Industrial and tourism development also threatens some areas.
Petroleum and natural gas deposits provide one of China’s most productive oilfields here in the Songhua-Nenjiang Plain. The oil industry must be regulated very carefully, however, in order to be compatible with the wetland bird habitat.
General recommendations for nature reserves in this area are to control as best possible the pollution caused by oil extraction, to prevent over-fishing, to avoid dam construction, and attempt to develop tourism in a manner that is compatible with ecological integrity of these wetland areas.
Justification of Ecoregion Delineation
Due to the fertile soil in the region, the surrounding areas are intensively used for agriculture and thus the original extent of this ecoregion is difficult to estimate. Mapped ecoregion boundaries are derived from the CVMCC (1979) Vegetation Map of China saline meadow and flooded grassland (66, 67) along the Nenjian River. Adjacent areas of annual cultivation (70a) are also included.
Chinese Vegetation Map Compilation Committee (CVMCC). 1979. Vegetation map of China. Map (1:10,000,000). Science Press, Beijing.
International Crane Foundation. Retrieved (2000) from: http://www.savingcranes.org/species/default.asp
MacKinnon, J. and K. Phillipps. 2000. A Field Guide to the Birds of China. Oxford University Press, New York.
MacKinnon, J., M. Sha, C. Cheung, G. Carey, Z. Xiang, and D. Melville. 1996. A biodiversity review of China. Worldwide Fund for Nature (WWF) International, Hong Kong.
Meine, C.D. and G.W. Archibald. editors. 1996. The cranes: Status survey and conservation action plan. IUCN, Gland, Switzerland, and Cambridge, U.K. 294pp. Northern Prairie Wildlife Research Center Home Page. http://www.npwrc.usgs.gov/resource/distr/birds/cranes/cranes.htm (Version 02MAR98).
Ramsar Convention on Wetlands. Retrieved (2000) from: http://www.ramsar.org/lib_dir_2_2.htm#ch2
United Nations Educational, Scientific, and Cultural Organization. Retrieved (2000) from: http://www.unesco.org
Prepared by: Chris Carpenter
Reviewed by: In process