Global grasslands: comparing the U.S. Northwestern Glaciated Plains and the Mongolian-

Manchurian Steppe

Brooke Jacobson

University of Idaho

Moscow, ID 83843

406-839-4706

jaco7785@vandals.uidaho.edu

Keyword : Northwestern Glaciated Plain, temperate, glaciated, Mongolian-Manchurian, arid

Reference: Jacobson, B.A. 2012. Global grasslands: comparing the U.S. Northwestern

Glaciated Plains and the Mongolian-Manchurian Steppe. REM 452.

Figure 1: The Norwest Glaciated Plains,

highlighted in orange, and the Missouri

Coteau, depicted in blue. Adapted from

WWF, 2012.

The Northwestern Glaciated Plain stretches from the southern regions of Alberta and

Saskatchewan, through north-eastern Montana,

and follows the Missouri River south through

North and South Dakota into a small portion of

Nebraska (Figure 1). The eastern edge of this area,

the Missouri Coteau, is also considered part of this

ecoregion for the purposes of this paper. This

grassland-steppe ecoregion covers roughly

160,000 km2 (USGS 2011) in the United States

and 250, 000 km2

in its Canadian range (Vance

1997). It is bordered to the west by the Rocky

Mountains and to the north by the Aspen

Woodlands and Boreal Forest. The land is not as wet and flat as the Northern Glaciated Plains to

the east, or as irregular topographically as the Northwestern Great Plains that border this area to

the south (EPA 2012). The Northwestern Glaciated Plains has a semiarid climate that exhibits

warm to hot summers with frigid winters. Temperatures range from 3 to 7 ºC, and decline with

elevation and northern latitude. Elevation in the ecoregion ranges from 610 to 1839 m (USGS

2011). Precipitation is low in the in the region, and yearly averages vary from 250 to 380 mm

(McNab and Avers 1994). The growing season is this ecoregion lasts roughly 100 - 130 days.

The Northwestern Glaciated plain lie in the rain shadow of the Rocky Mountains, and

consequently the weather patterns are largely controlled by storm systems from the Gulf of

Mexico. Most precipitation falls in the spring and early summer, and the region receives the

majority its moisture in the months of May and June (USGS 2011). In the northern reaches of

Northwestern Glaciated

Plains

Ecoregion

Figure 2: Rolling glaciated Canadian

grassland. From Robert T. Coupland 1961.

this ecoregion, up to 20% of the annual precipitation may fall in the form of snow (USFS 2011).

High winds are also a factor that have a large influence on climate and exacerbate

evapotranspiration. Some areas have an annual moisture deficit of 30 cm per year or more

(Yansa 1998) Due to this variable weather pattern and its semiarid climate, the area is subject to

drought (USGS 2011).

Topography is variable within the Northwestern Glaciated Plain. Mountains in the

Montana portion of the ecoregion formed from volcanic activity and were influences by glacial

movement (Stewart and Kantrud 1972). Physiognomic features in the eastern Missouri Plateau

differ from areas in greatly from these mountain outcrops. The Missouri Plateau, also referred to

as the Coteau du Missouri or “hills of the Missouri”, is the rolling grassland region along the

Missouri River (Kruse and Piehl 1986). Its northern range includes the grassland region in

southern Canada known as Palliser’s Triangle.

Despite the varying topography,

the Northwestern Glaciated Plains are

predominantly hilly to flat grassland

prairies with occasional mountain outcrops

and playas (Figure 2). These playa areas,

referred to as prairie potholes, occur in

both the Canadian and U.S. portions of the

plain. These water bodies, which may be

ephemeral or permanent, are shallow depressions formed after the melting glacial ice buried

beneath deposited sediments during the Pleistocene glaciations. The glacial till that is covers the

land in this area is comprised of more than 50% silt and clay, making these soils fertile, but

sometimes impermeable where they have formed aquitards -- land formations which restrict

groundwater permeability (Van der Kamp and Hayashi 1998). Gneiss, granite, dolomite,

quartzite, and limestone comprise the glacial till in the Couteau du Missouri, often giving the

land a stony appearance. The glacial parent material of the plain, much of it containing

carbonates and pyrite, are the source for much of the salts in prairie wetlands (Van der Kamp and

Hayashi 2009). Many of these potholes are ephemeral due to the hot summer climate. The

wetland and pothole areas of the Northwestern Glaciated Plains serve as important breeding

habitat for of dabbling ducks, Anas spp. (Krapu 2000).

According to an extensive survey of the region by Stewart and Kantrud (1972), wetland

vegetation in the Northwestern Glaciated Plain includes Ditichlis stricta, Hordeum Jubatum,

Carex brevior, Juncus balticus, and Carex antherodes. Other species including Typha spp.,

Symphoricarpos occidentalis, and Rosa woodsii also occur, as well as Salix spp. and Populus

spp. Salinity is the main determinant of the species composition of these wetlands (Neill 1993,

Stewart and Kantrud 1972).

Dominant grasses include in the Northwestern Glaciated Plain include Hesperostipa

comata, Bouteloua gracilis, Hesperostipa spartea, Agropyron smithii, and Koeleria macrantha

(Brown 1993, Coupland 1961, Stewart and Kantrud 1972). Woody species and forbs are less

common in the dry grasslands and include Salix spp. and Populus spp.

Fire and drought have historically been determinants of natural vegetation in the region

(Taylor 2011). Since the arrival of Europeans around 100 years ago, conversion of native

rangeland to agriculture has been an ongoing phenomenon in this region. Irrigation is difficult in

the drier areas, but access to ground water by has opened up more arid land in the area. Drainage

of the Prairie Pothole region and conversion to cropland has also changed the hydrology and

habitat functions of the area. Fossil fuel extraction has also had an impact on the Northern

Glaciated Plain. Oil and natural gas development began in the mid-nineteen-hundreds, and

continued mining of the Bakken formation have also changed the landscape of the Northwestern

Glaciated Plains in eastern Montana and western North Dakota.

British explorer Captain Palliser explored the region that is now southern Canada in the

mid nineteenth century and reported that the area was unlikely to be utilized by European

immigrants. He described it as possessing desert-like characteristics, and assumed it was not

fertile enough for crop production (Last 1994). Today, Palliser’s triangle is the bread basket of

Canada. At the beginning of the twenty-first century, the glaciated planes of Canada have more

than 80% of Canada’s farmland (Boehm 2004). According to a study by the Taylor (2011), land

cover in the Northwestern Glaciated plains of the U.S. has markedly changed between 1973 and

2000. Fluctuations in precipitation determine the size of prairie potholes and lakes, and increased

moisture in the 1980s decreased the available land for crop cultivation. Also, many farmers

participated in the Conservation Reserve Program, and many crop acres were converted to

grassland (Taylor 2011).

With the introduction of European crops, other exotic plant species have also been

brought into the plains. Many species were introduced for pasture forage, and include Bromus

inermis, Agropyron cristatum, and Dactylis glomerata. Invasive species in the area that thrive in

disturbed sites include Salsola tragus, Bassia scoparia, and Melilotus officinalis (Stewart and

Kantrud 1972).

Ecoregions of Eastern Eurasia. The

Mongolian –Manchurian Steppe is

region 30. Udvardy 1975.

The Mongolian-Manchurian Steppe is part

of the Palearctic ecozone in central Asia, and covers

about 1 million square kilometers (Udvardy 1975,

McGinley 2008). The geographic range of the

steppe is bordered by Russia to the north and the

Gobi Desert to the southwest. It covers much of

Mongolia, and stretches into the northeastern region

of China, the Inner Mongolia Autonomous Region.

The topography of the areas is dominated by undulating hills and tablelands. The lands vary from

meadow steppes to desert grasslands and shrublands. The yearly average temperature within this

ecoregion ranges from -2.1 to – 3.3 ºC. Summer is the rainy season in most areas, and winters are

extremely cold and dry (Hall 1930).

This varying topography causes a wide range of climatic conditions. The Mongolian-

Manchurian ecoregion has a temperate climate (Mongolian-Manchurian grassland). The mean

elevation of the region is around 1,500 m, covering the grasslands of the Great Higgan Mountain

in the Inner Mongolia Autonomous Region to the Mongolian Plateau and desert steppe to the

west and north. The grasslands of the Great Higgan Mountains have cooler winters than

international regions with comparable latitude due to the presence of strong northwesterly winds.

The large expanse of grassland soil in the Mongolian-Manchurian Steppe is an important

part of the global carbon cycle. Mollisols in this region contains high amounts of black carbon

(BC), a product of the incomplete combustion of organic material. According to a world-wide

study of carbon in grassland ecosystems, soils of Mongolian-Manchurian Steppe contained up to

4 times more BC than similar international sites (Rodionov et al. 2010).

Biological soil crusts (BSCs) are also an important component of this rangeland system.

These crusts are comprised of intricate associations of lichens, algae, mosses, and cyanobacteria.

BSCs are critical to the stabilization and nutrient cycling of soils, especially in arid environments

(Evans. R. D. and J. R. Johansen 1993, Landgston and Neuman 2005). A study of BCSs in the

Mongolian Steppe by Liu et al. (2009) found that high density sheep grazing had a negative

impact on both BSC cover and potential nitrogen fixation compared to lower stocking rates. In

the same study, one year of grazing removal showed little regrowth of the BSC. This result was

consistent with similar studies that predict slow recovery rates of BSCs in North America, where

a Utah study of these soils that estimated historic moss cover would take up to 250 years to

reestablish (Belnap 1993). The ability of these organisms to fix nitrogen and prevent soil erosion

is critical for the growth of plants. The vegetation these soils support is important to providing

species habitat in the Mongolia-Manchurian Steppe.

Grasslands and shrublands in Mongolia and northern China are native habitat to many

plant and animal species. Drought resistant grasses such as Stipa gobica, Agropyron desertorum

as well as shrubs such as Ephedra equisetina are prevalent in the arid southwestern area of this

region, adjacent to the Gobi Desert. Other prevalent grasses include Leymus chinensis and Stipa

grandis. Shrub vegetation in the more desert-like regions include Ceratoides latens, Salsola

passerine, and Potaninia mongolica (Bai 2008). The brown-eared pheasant, Crossoptilon

mantchuricum, winters in the vegetation of these dry shrub-steppe communities. Crossoptilon

mantchuricum is the area’s only endemic bird, and the health of every constituent of the

ecosystem is necessary for the success of this species (WWF 2012). Native ungulates are also

facing challenges in the steppe. The Mongolian gazelle, Procarpa gutturosa, has been negatively

affected by the development of these rangelands. In a study of these migratory animals (Olsen et.

al. 2009), the recent erection of fences, especially on the Russian-Mongolian border have

restricted the movement of the gazelle as the ecoregion has become increasingly arid. Fences

also cause mortality to the animals. Many of these fatalities are a result of fences around trans-

rangeland railways (Olsen et. al. 2009).

These grasslands have undergone little intensive agronomic conversion compared to

many temperate rangelands world-wide due to a long history of grazing and nomadic culture

(Henwood 1998). The fertile grassland soils of the region have supported crops such as wheat

and soybeans. The Manchurian Plain has been referred to as the “Grain basket of Asia,” due to

its grain production (Hall 1930). However, sheep and goat herding has remained the major

agricultural practice in the region (Mongolian-Manchurian grassland 2012). Overgrazing has

been a result of heavy utilization, especially by goat grazing.

The Northwestern Glaciated Plains of North America and the Mongolian-Manchurian

Steppe are both important temperate grasslands. These rangelands have similar climate,

topography, and species. Both are have been impacted by drought and face the challenges of

anthropogenic utilization and development. It is important that these fragile grassland resources

continue to be studied and stewarded in order to continue providing the many ecosystem services

that are vital to the health of the planet.

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