Nenjiang River grassland

• Category: Grassland, Tundra, and Human Biomes.
• Geographic Location: Asia.
• Summary: The Nenjiang River Grassland is an ecologically significant region under threat from agriculture and other human activities.

The Nen River, or Nen Jiang, rises in the mountains that form the borderland between China’s northeast and the Russian Far East. It is a tributary of the Sungari River, which is in turn a tributary of the mighty Amur. It descends across the Songhua-Nenjiang, or Song-Nen, Plain, where it meanders through grasslands that have considerable ecological importance. Numerous tributaries flow into the Nen in its course across the grassland from both branches of the Khingan Ranges; these contribute to flooding in the region. Many soil types have been deposited by the different water flows, and the region is important for agriculture. As a result, there is more farming and fishing activity here, which threatens the sustainability of several species.

The Nen River is frozen for up to four months of the year. Flooding is a regular issue at the time of the thaw and during the summer rainy season, particularly at the confluences of the Nen and important tributaries. The river is navigable, by small craft at least, for extensive distances along the plain. River transportation was an important means of spreading populations, and developing economy and society in the premodern era; the Nen River consequently was instrumental in the early settlement of Heilongjiang Province in China.

The Nen River region has a continental monsoon climate, and is warmer and drier than the surrounding mountains. The mean annual precipitation is 15–17 inches (400–450 millimeters).

Biodiversity and Conservation

The grassland region as a whole consists of a complex mix of flowing and still water, interspersed with marshes and areas of reeds. The diverse environments represent space for fish, waterfowl, insects, and amphibians; the protected Siberian wood frog Rana amurensis is one of several species that dependd on the area.

The extensive marshy and wetland habitats are protected to some extent by the Zhalong and Momoge nature reserves. The Zhalong reserve, known as Home of the Cranes, contains many permanently flooded areas, resulting in part from the overflowing Wuyu’er River, and is home to a variety of species, most notable of which are rare or vulnerable crane species. The 811 square miles (2,100 square kilometers) of the reserve are home to 46 fish species, more than 150 types of birds, 277 different kinds of insects, and 21 other animals.

Approximately 700 of the world’s 1,000 endangered cranes are residents of the Nen, including the threatened red-crowned crane (Grus japonensis). Some 15 crane species are found in the Zhalong, which is an internationally important wetland area. Resident cranes include the white-naped crane (G. vipio), demoiselle crane (Anthropoides virgo), common crane (G. grus), the endangered Siberian crane (G. leucogeranus), and hooded crane (G. monacha), as well as other rare birds such as the endangered oriental white stork (Ciconia boyciana), black-headed ibis (Threskiornis aethiopicus melanocephalus), mandarin duck (Aix galericulata), and Eurasian spoonbill (Platalea leucorodia).

Cranes also are present in the Momoge Nature Reserve, which is known as Heaven for Birds, and is located mainly in Jilin Province. Its 355,832 acres (144,000 hectares) are 80 percent flooded. Cranes represented in this grassland region include hooded, demoiselle, and white-crowned cranes. Many cranes use this area as a stopping point while migrating to and from Siberia.

Typical vegetation in the lowlands of the Nen 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 spp. olgensis) and birch (Betula japonica). Meadows are filled with such grasses as Calamagrostis epigeios and C. langsdorfii that are adapted to flooded soils. These grasses often grow as dense tussocks. Lakes are often filled or lined at the margin by the salt-tolerant reed (Phragmites communis). Upland areas are dominated by grasslands, forest-grasslands with crooked elms, and shrub groves of wild apricot.

Common amphibians include toad (Bufo raddei), tree frog (Hyla arborea), and the frogs Rana nigromaculata and R. amurenss.

Environmental Threats

Unfortunately, salinity has begun to threaten parts of the grasslands, significantly impacting the area’s habitat sustainability. Demand for water for agricultural irrigation can place pressure on the ability of the system to maintain its freshwater resources, which can intensify if the currently low level of tourism and economic development begins to increase. There is a further long-term threat represented by the possible presence of exploitable oil and gas reserves in the region.

River salinity concern is accompanied by overfishing and egg collecting, as well as pollution linked to agricultural and other human-based activities. The loss of soil may have long-term climate-change effects, which could alter the vegetation of the region. Wildfire incidents have grown to almost uncontrollable outbreaks when excessive reed clearance and low water levels have coincided, as occurred in 2000 and 2001, when more than 32,124 acres (13,000 hectares) of reedbeds were destroyed.

Experts are aware of the threats facing the region, and able stewardship has resulted in the creation of an incipient Asian Wetland Network project, which has brought together representatives from China with others from Iran, Russia, and Kazakhstan. Together, they are working to gather information, write manuals, and raise awareness.

Climate change poses additional threats. Rising temperatures and rainfall amounts could vary enough to impact the vegetation and the environment for local wildlife. Warmer temperatures could expand the agricultural lands and increase the accompanying chemical runoff that affects water levels and quality. Research is ongoing to attempt to predict effects and find ways to mitigate them.

While the area is incredibly important to the many crane populations, limited swaths of land are protected for their usage. Two significant areas of protection are the Zhalong Nature Reserve and the Momoge Nature Reserve. Both are Ramsar wetlands of international importance. More protections may be needed though to help maintain balance to support the many species that rely on these areas.

Bibliography

Carpenter, Chris. “Nenjiang River Grassland.” One Earth, www.oneearth.org/ecoregions/nenjiang-river-grassland/. Accessed 23 Nov. 2024.

Li, Fengping, Guangxin Zhang, Hongyan Li, and Wenxi Lu. "Land Use Change Impacts on Hydrology in the Nenjiang River Basin, Northeast China." Forests, vol. 10, no. 6, 2019. DOI: 10.3390/f10060476. Accessed 23 Nov. 2024.

MacKinnon, John Ramsay, et al. A Biodiversity Review of China. Hong Kong: Worldwide Fund for Nature International, 1996.

Wang, Zhi-chaing, Jian-chun Fu, Chengyuan Hao, and Zhichao Chen. “The Spatial-Temporal Pattern Changes of the Red Crowned Crane (Grus Japonensis) Population in Zhalong NNR and the Related Driving Forces.” Acta Ecologica Sinica 29, no. 6 (2009).

Xia, Xueqi, Zhongfang Yang, Yan Liao, Yujun Cui, and Yansheng Li. “Temporal Variation of Soil Carbon Stock and Its Controlling Factors Over the Last Two Decades on the Southern Song-Nen Plain, Heilongjiang Province.” Geoscience Frontiers 1, no. 1 (2010).