Chapter 2: North American Great Plains

How much fodder do the Great Plains produce in the central and northern part of the Great Plains? In what kind of a climate is the prairie rangeland growing?

Robert T. Coupland is at the Department of Crop Science and Plant Ecology, University of Saskatoon, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. He states in Natural Grasslands, Western Hemisphere 1992 about the Mixed Prairie, when it is growing:

Mixed Prarie in SW Canada and Western USA, from southeastern Alberta, southern Saskatchewan and south-western Manitoba; eastern Montana, western Dakota and western South Dakota; eastern Wyoming and part of western Nebraska; and a belt running southward through Kansas, Oklahoma and into Texas. It lies entirely within the Great Plains, with a latitudinal range of about 2600 km (from about 52 to 29°N. – R.T. Coupland (1992:151).

The following two places and climatic data are also from Natural Grasslands, Western Hemisphere 1992 Table 10.1: Selected climatic factors at IBP study sites in the mixed-prairie region.

Dickinson

In southwestern North Dakota. 46°53´N, 102°49´W. Elevation 830 m a.s.l. Mean annual precipitation 403 mm. Mean annual air temperature 4.1°C. July mean air temperature 21.1°C. Potential evapotranspiration 584 mm per year at earth’s surface. 584 mm : 16.95 = 34.45 kcal.cm² yr net radiation at earth’s surface. In the year 1970, this year’s growth 320 gDM/m². 320 gDM/m² yr : 584 mm ppt year = 0.5479452055 gDM/m² yr.

Cottonwood

At 43°57´N, 101°52´W, in central southern South Dakota. Elevation 744 m a.s.l. Mean annual precipitation 360 mm. Mean annual air temperature 8.5°C. July mean air temperature 23.7°C Potential evapotranspiration 703 mm per year. 703 : 16.95 = 41.47 kcal cm² yr net radiation at earth’s surface. Aboveground growth in the year 1970 = 210 gDM/m². Aboveground growth in the year 1971 = 312 gDM/m²

210 gDM/m² yr : 360 mm ppt yr = 0.5833333 gDM m²/mm ppt yr

312 gDM/m² yr : 360mm ppt yr = 0.8666666 gDMm²/mm ppt yr

The average of both places 0.725 gDM m²/mm ppt yr

After: Robert T. Coupland (1992:152, 163) Table 10.1, 10.2.

Grazing Plains bison on a bison ranch in southern Canada, in winter. From: Bison Pastures and Grazing Management (1998:7), published by Grazing and Pasture Technology Program (GAPT).

Northern Great Plains, Central Southern Canada

How much aboveground dry matter is growing on the native grasslands of southern Canada’s Prairie Provinces? How can we calculate that from the carrying capacities, in hectares per animal unit month? And at how much annual precipitation is this grass growing there? How large is there the annual solar net radiation at the earth’s surface?

I have based here my calculations on the following sources: Management of prairie rangeland 1981, published by the Saskatchewan Department of Agriculture, at Weyburn, Saskatchewan. By S. Smoliak and A. Johnston, Research Station, Lethbridge, Alberta. M. R. Kilcher, Research Station, Swift Current, Saskatchewan, and R. W. Lodge, Department of Regional Economic Expansion, Regina, Saskatchewan. From: Table 1, Weather records from six locations, and Table 6, map showing carrying capacity in ha/AUM on native grasslands in Southern Canada’s Prairie Provinces.

Net radiation at earth’s surface from Climates of North America, World Survey of Climatology Vol. 11, 1974 p. 116 Fig. 29, by R. A. Bryson and F. K. Hare (Eds.)

The term gDM/m² yr means here grams aboveground dry matter per square meter per year. And mm ppt yr means here millimeters precipitation per year. One animal unit per month (AUM) is here a 450-kg cow. She needs 350 kg dry matter per month. These 350-kg dry matter are 55% of the annual aboveground plant-production. The other 45% aboveground plant-production (286-kg dry matter) remain standing till next year, as carry-over, so that the plant-cover will stay healthy. Altogether that is then 636 kgDM/ha yr.

We shall assume now, that these 636-kg aboveground dry matter are growing on one hectare. How much is that then per square meter per year? One hectare has 10,000 m². On this grassland, then 63.6 gDM/m² has to grow per year.

Southern Canada, with its grassland, its carrying capacity of cattle and bison and horses in hectares per animal unit of the native grasslands of the Prairie Provinces (1 hectare = 2.47 acres). The key to this map at the top right hand: from the top down: a) less than .01 ha, b) .92 - 1.2 ha, c) 1.3 - 1.8 ha, d) more than 1.8 ha. From: management of the prairie rangeland, Agriculture Canada, Weyburn, Saskatchewan (1976) Fig. 6.

Plains bison on summer pasture on a bison ranch in southern Canada. From Bison Pastures and Grazing Management (1998:5), published by Grazing and Pasture Technology Program (GAPT).

Mixed Prairie Stipa-Bouteloua type: Site 1

From management of prairie rangeland (1981:11, and Table 3). Up to about 53°N in S Saskatchewan and SE Alberta, 100-115°W. There, 1.8 hectares are needed, to feed one animal unit per month (1.8 ha/AUM). Annual precipitation 250-350 mm, an average 300 mm per year. Annual net radiation at earth’s surface is about 35 kcal cm² per year. 1.8 ha/AUM is then 35.0 gDM/m² yr : 300 mm ppt yr = 0.167 gDM m²/mm ppt yr.

Mixed Prairie: Stipa-Bouteloua type: Site 2

From management of prairie rangeland (1981:15). (1981:11, and Table 3) Up to about 53°N in S Saskatchewan and SE Alberta, 100-115°W. 1.4 ha/AUM = 45.0 gDM/m² yr. Annual precipitation less than 350 mm. 35 kcal cm² net. radiation at earth’s surface per year. 45.0 gDM/m² : 350 mm ppt yr = 0.128 gDM m²/mm ppt yr. The average of both sites is here 0.1475 gDM m²/mm ppt yr

Mixed Prairie: Stipa-Bouteloua-Agropyron type: Site 1

In S Saskatchewan and SE Alberta, near 53-55°N, 100-115°W. About 35 kcal cm² net radiation at earth’s surface per year. Annual aboveground dry matter production 560 kg/ha. One needs then 1.1 hectare to feed one animal unit one month. That is 56.0 gDM/m² per year. There is 1.1 ha/AUM. Annual precipitation is less than 350 mm per year. 56.0 gDM/m² : 350 mm ppt = 0.16 gDM m²/mm ppt per year.

Mixed Prairie: Stipa-Bouteloua-Agropyron type: Site 2

In southern Saskatchewan and SE Alberta, near 53-55°N, 100-115°W. About 35 kcal cm² net radiation at earth’s surface per year. Annual aboveground plant-production 730 kg/ha = 73.0 g/m² yr. There 2.2 ha/AUM are needed. 73.0 gDM/m² : 350 mm ppt =0.208 gDM m²/mm ppt yr. The average of both sites is 0.184 gDM m²/mm ppt yr

Fescue Prairie: Fescua scabrella: Site 1

From management of prairie rangeland (1981:15). Up to about 53°N, 123°W. Southern half of middle of Alberta, east of Rocky Mountains, a narrow strip, and in lower third of Saskatchewan, also a narrow strip running East-West, near 53°N. About 33 kcal cm² net radiation at earth’s surface per year. 460-560 mm ppt, average 510 mm ppt yr. 900 kg/ha = 90 gDM/m² yr. One animal unit needs there 1.8 ha of native rangeland (1.8 ha/AUM). 90.0 gDM/m² : 510 mm ppt = 0.176 gDM m²/mm ppt yr

Fescue Prairie: Fescua scabrella: Site 2

From management of prairie rangeland (1981:15). Up to about 53°N, 123°W. Southern half of middle of Alberta, east of Rocky Mountains, a narrow strip, and in lower third of Saskatchewan, also a narrow strip running East-West, near 53°N. About 33 kcal cm² net radiation at earth’ surface per year. 460-560 mm ppt, average 510 mm ppt yr. 1400 kgDM/ha = 140 gDM/m² yr. One animal unit needs here 1.1 ha of native rangeland, to live one month (1.1 ha/AUM). That is 140 gDM/m² yr. 140 gDM/m² : 510 mm ppt = 0.274 gDM m²/mm ppt yr. The average of both sites is 0.225 gDM m²/mm ppt yr

Other Prairie Rangelands in Central Southern Canada

The following sites are also from management of prairie rangelands (1981:8) Table 1, annual precipitation, and Figure 6, carrying capacity in ha/AUM on native grasslands in Canada’s Prairie Provinces, in (1981:17) Fig. 6. Annual average net radiation at earth’s surface is from Climates of North America, World Survey of Climatology Vol. 11 (1974:116) Fig. 29, by R. A. Bryson and F. K. Hare (Eds.)

Lacombe, Alberta.

Near 56°N, 113°W, S. W. of Edmonton. About 33 kcal cm² net radiation at earth’s surface per year. 452 mm ppt yr. One animal unit needs then less than 0.91 hectare per month. Less than 0.91 ha/AUM. That is 699 kg/ha dry matter/AUM (55% intake and 45% carry-over) = 69.6 gDM/m² year. 69.9 gDM/m² : 452 mm ppt = 0.155 gDM m²/mm ppt yr.

Lethbridge, Alberta.

About at 49°N, 113°W, in southern Alberta. About 40 kcal cm² net radiation at earth’s surface. 411 mm ppt yr. .92-1.2 ha/AUM average 1.06 ha/AUM = 674 kg/ha = 67.4 gDM/m² year. 67.4 gDM/m² : 411 mm ppt yr = 0.164 gDM m²/mm ppt yr

Brandon, Manitoba

Near 50°N, 98°W, east of Winnipeg. 452 mm ppt yr. About 40 kcal cm² net radiation at earth’s surface per year. Less than 0.91 ha is needed there, to feed one animal unit one month (0.91 ha/AUM). That is 699 kg/ha or 66.9 gDM/m² yr. 69.9 gDM/m² : 452 mm ppt = 0.155 gDM m²/mm ppt yr

Swift Current, Saskatchewan

Near 51°N, 108°W, west of Regina, in southern Saskatchewan. About 37 kcal cm² net radiation at earth’s surface. 358 mm ppt yr. Less than 0.91 ha/AUM. That is 69.9 gDM/m² yr. 69.9 gDM/m² : 351 mm ppt = 0.196 gDM m²/mm ppt yr. 

Prairie bison on a grassland in Southern Canada, an a bison ranch. From: Bison Pastures and Grazing Management, published by Grazing and Pasture Technology Program (GAPT) (1998:1)

Rocky Mountain Bighorn Range

Dry grasslands and how much fodder is growing there, gDM.m²/mm ppt yr. From: Range ecology of Rocky Mountain bighorn sheep in Canadian national parks. By John G. Stelfox, Canadian Wildlife Service, Report-Series Number 39, 1976. Study area: with bighorn sheep in Western Canada, in Alberta at Alberta/British Columbian border. Grasslands growing on valley bottoms, on mountain summits and ridges, and on slopes.

Waterton Lakes National Park

49°04´N, 113°57`W, 1295 m a.s.l., mean ann. temp. 5.0°C. Mean ann. precipitation 1075 mm. About 38 kcal cm² net radiation at earth’s surface per year. Productive rough fescue (Festuca scabrella). Used mostly by bighorn sheep, but also by a few mule deer and elk (wapiti). 619 kg/ha DM.yr (61.9 gDM/m² yr) (aboveground forage produced per year). 61.9 gDM/m².yr : 1075 mm ppt yr = 0.05758139535 gDM.m²/mm ppt yr.

Banff National Park

51°11´N, 115°34´W, 1383 m a.s.l., 2.1°C mean ann. temperature. About 35 kcal cm² net radiation at earth’s surface per year. 469 mm mean annual precipitation. Productive rough fescue-sedge (Carex spp.). Used by bighorn sheep, elk (wapiti) and a few mule deer. 474 kg/ha DM yr = 47.4 g DM/m² yr (aboveground forage produced per year). 47.4 gDM/m² yr : 469 mm ppt yr = 0.1010660981 gDM.m²/mm ppt year.

Jasper National Park

Unproductive sedge-wheatgrass – wild rye. Used by bighorn sheep, and some elk, and deer. Ca. 33 kcal cm² yr solar net radiation at earth’s surface. 52°53´N, 118°04´W, 1050 m a.s.l. Mean ann. temp. 3.0°C, 406 mm mean ann. precipitation. 225 kg/ha DM.yr. 22.5 gDM/m² yr (aboveground forage produced per year). 22.5 gDM/m² yr : 406 mm ppt yr = 0.05541871921 gDM.m²/mm ppt year. John G. Stelfox (1976:10, 14, 25)

Bison bulls in Yellowstone Park in winter near hot wells. Photo by T. D. Brock. From: Brock Biology of Microorganisms (1997:3)