How much fodder do the dry meadows produce further north in North America: in the southwestern part of the Northwest Territories, where the bison is grazing? And how much fodder is growing on the dry meadows further west, at the same latitude in the southwestern part of the Yukon Territory?
Dry Meadows in Slave River Lowlands, N.W.T.
H.W. Reynolds and A.W.L. Hawley have published their findings in Bison ecology in relation to agricultural development in the Slave River lowlands, NWT, Occasional Paper Number 83 Canadian Wildlife Service 1987. The Slave River lowlands (SRL) are situated in the southwestern part of the Northwest Territories (NWT), between Great Slave Lake on the north and the 60th parallel to the south. 112-113°W. The area lies in the Great Slave plain portion of the Interior Plains Province. It is characterized by low-lying, flat land with numerous lakes and abandoned stream beds. The elevation of the lowlands decreases from about 207 m at Fort Smith in the south to about 158 m at Fort Resolution in the north. Reynolds, Hal W. (1987:13)
The annual precipitation at the southeastern limit of the SRL, Fort Smith, averaged 33 cm during 1973-72 and 47 cm during 1973-75. The mean annual temperature was –3.5°C during 1941-70. Reynolds, Hal W. (1987:13)
Hal W. Reynolds and Donald G. Peden: studied aboveground plant production at the Hook Lake area in the Slave River lowlands (SRL) during 1974 and 1975. The mean annual herbage yield for wet meadows in 1974 and 1975 (4480 kg/ha and 4320 kg/ha, respectively) significantly exceeded that for dry meadows (2680 kg/ha and 1880 kg/ha, respectively. Herbage yield was not limiting to the production of bison in the SRL. Reynolds, and Peden (1987:39)
The annual herbage yield estimated in 1974 and 1975 for wet meadows (4480 and 4320 kg/ha, respectively) was significantly greater than the yield estimated for dry meadows (2680 and 1880 kg/ha, respectively) (Table 1). Reynolds and Peden. (1987:40)
Slave River lowland, NWT: Summary
Just above the 60°N, at 112-113°W. 158-207 m above sea level. Average annual precipitation 470 mm in 1973-1975. Average annual net radiation at earth’s surface at Hook Lake, where aboveground plant production in the Slave River lowland was measured, is about 27.5 kcal cm² yr. The flooded wet sedge meadow was growing there in 1974 and 1975 an average 400 gDM/m² yr. That is 43% more than the dry meadow. Annual aboveground plant production of dry meadows in 1974 was 268 gDM/m² yr, and in 1975 was 188.0 gDM/m² yr. The average of both years is 228 gDM/m² yr. 228 gDM/m² yr : 470 mm ppt yr = 0.485106383 gDM/m² yr
Kluane Area, SW Yukon Territory
The Kluane Area lies in the southwestern part of the Yukon Territory, east of Alaska, between 61°-62°North. How much aboveground dry matter is growing there now on the dry grassland. That is on grassland, which does depend mostly or completely on the annual precipitation, since the ground is so dry. That is, in contrast to the wet meadows, growing on wet ground, close to the shore of rivers, ponds, and lakes, and which may be flooded in spring or even during the whole summer. What have scientists found out now about this?
H. W. Reynolds and co-workers report in their Range Assessment of the Nisling River Valley, Yukon Territory as habitat for wood bison (May 1982): The Nisling River Valley lies between longitudes 137°05’ and 138°26’ and north latitudes 61°35’ and 62°00’. Elevations in the study area range from approximately 900 m a.s.l. along the valley bottom to 2,000 m in the surrounding mountains. The area lies within the southern fringe of the permafrost region of Canada. That is, at the southern limit of discontinuous permafrost. In most sites, permafrost is close to the surface and frost polygons are often evident, particularly in the eastern portion of the study area at higher elevations.
R. Johansen and co-workers report about the Grazing potential for selected areas in the Greater Kluane Planning Region (1989:4, 5, 12) about the most productive dry grasslands and wet grasslands, which are growing there now.
Annual aboveground plant-production
Carex (sedge meadows), flooded in late spring and in summer.
Forage production: 62 g/m² yr
Grazing capacity: 9 ha/AUY (animal units per year).
There the wood bison is able to graze in late fall and winter, when the water level has dropped enough.
Artemisia-Festuca (grassland/parkland). This is a dry grassland.
Forage production: 37 g/m² yr.
Grazing capacity: 15 ha/AUY.
Artemisia-Festuca (grassland/parkland)
This is a dry grassland in the aspen phase. That is, when the aspen trees have begun to invade this grassland.
Forage production: 45 g/m² yr.
Grazing capacity: 12 ha/AUY.
Arctostaphylos-Bromus (dry grassland slopes)
This grassland is growing on steep south facing slopes. The grazing potential is generally limited, because of the steep slopes and inaccessibility.
Forage production: 27.5 gDM/m² yr
Grazing capacity: 20 ha/AUY.
J. MacPherson and A. Hodgson report in their Agriculture and Grazing Greater Kluane Planning Region (1989:5) and Appendix III.
Climate in the Greater Kluane Planning Region
Aishihik: Mean annual temperature –4.4°C. Mean annual precipitation 256.3 mm. About the annual aboveground plant-production (dry weight), they give the same values as R. Johansen et al. (1989)
Wet sedge meadow 62 gDM/m² yr
Grassland/Parkland
In grassland phase: 37 gDM/m² yr
In aspen phase: 45 gDM/m² yr
Dry grassland on steep south-facing slopes: 27.5 gDM/m² yr.
Arthur Bailey and co-workers report in their Management of Yukon Rangelands (1992:20, 21) about a dry grassland at Kluane Lake: Fringed Sage-Sheep’s Fescue Community: This community is found along the north shore of Kluane Lake. Sheep’s fescue is the principle grass, which is quite appropriate since Dall sheep grazed the observed area. Other grass and grass-like species include glaucous bluegrass and blunt sedge. Stands of this community occur on steep, southerly-facing slopes. It would appear that windblown sediment (= loess) continues to be deposited on these slopes. This is a result of the high winds, which pick up particles as they blow down the valleys of glacier fed rivers flowing eastward out of Kluane National Park. The addition of loess seems to enhance the productive capacity for grazing on these soils.
Herbage production: 400 kg/ha = 40 gDM/m² yr
Grazing capacity: 4 ha/AUM = 48 ha/AUY
AUM: animal unit per month. AUY = animal unit per year. – A. Bailey et al. (1992:20, 21)
Average annual net radiation at earth’s surface in Kluane Area, in SW Yukon, between 61°-62° North is about 25 kcal cm² (kly). According to R. A. Bryson and F. K. Hare, in Climates of North America, World Survey of Climatology, Volume 11 (1974) Figure 29
Kluane Area: Summary
Located at 61°-62°North and 137°-138°West. Valley bottom about 900 m above sea level. Annual average precipitation 256.3 mm. Annual average net radiation at earth’s surface about 25 kcal cm² yr (kly). Most productive dry grasslands:
Dry grassland, without aspen trees: 37 gDM/m² yr
Loess-blown dry grassland at Kluane Lake, Dall sheep pasture, on steep, south-facing slopes: 40 gDM/m² yr.
The flooded wet sedge meadow produces about 62 gDM/m² yr. That is 37% more than on the loess-blown dry grassland on the south-facing steep slopes at Kluane Lake, where 40 gDM/m² yr is growing, where the Dall sheep is grazing.
37 gDM/m² yr : 256.3 mm ppt yr = 0.1443620757 gDM.m²/mm ppt yr
40 gDM/m² yr : 256.3 mm ppt yr = 0.1560671089 gDM.m²/mm ppt yr
At 25 kcal cm² yr net radiation at earth’s surface and about 900 m above sea level.
This means: The dry grassland in the Kluane Area in the SW Yukon, at 61°-62°North, east of Alaska, without any aspen trees, produces 0.1443620757 grams aboveground dry plant matter per square meter per year per millimeter of annual precipitation.
And the dry loess-blown grassland, on the steep south-facing slopes at Kluane Lake, where the Dall sheep is grazing, is growing 0.1560671089 grams aboveground dry plant matter per square meter per year.