Chapter 2: Truelove Lowland, Devon Island

In what kind of a climate and on what kind of a plant-cover is the muskox living on Truelove Lowland, Devon Island? - In the book, Truelove Lowland, Devon Island, Canada: A High Arctic Ecosystem (1977) we shall find out more about this. It was edited by L. C. Bliss.

Net radiation was 17.8 kly yr (17.8 kcal/cm² yr). These measured values are in marked contrast to calculated values for Resolute Bay with its 2.5 kly (2.5 kcal/cm²) yr for net radiation (Hare and Hay 1974). Furthermore, the same authors present annual net radiation isopleths, which show that values in the Low Arctic may vary from 11 kly (11 kcal/cm²) yr (Barrow, Alaska) to 25 kly (25 kcal/cm²) yr (Hudson Bay Lowland) and only reaches zero at the latitude of northern Ellesmere Island. That is to say, a positive radiation balance exists over virtually the entire terrestrial arctic. By interpolation, the net radiation balance for Devon Island should be about 3 kly (3 kcal/cm²), rather than 17.8 kly (17.8 kcal/cm²), as presented above. (1977:89)

Microclimatological studies on Truelove Lowland

After Courtin and Labine (1977:74) Table 1. Annual mean climatic data for weather stations adjacent to Devon Island (Thompson 1967).

Rydén has estimated, that annual precipitation averages 185 mm on the Lowland. ...Truelove Lowland is essentially an oasis in the High Arctic Polar Desert. The phenomenon, however, is not unique. Adjacent lowlands to the Truelove, show similar characteristics, if not so well developed. The Fosheim Peninsula, Lake Hazen, and Tanquary Fiord on Ellesmere Island are also atypical for their latitude. ...Truelove Lowland is characterized not only by higher insolation and warmer temperatures, but also by abundant soil moisture in the meadows, that represent a major portion of the terrestrial vegetated area. (1977:96, 102, 103)

Ecology and primary production of Sedge-moss Meadow communities,

Truelove Lowland, on Devon Island

Annual net production of the aboveground biomass averaged 28 g m² at the frost-boil meadow, 42 g m² in the hummocky meadow and 45 g m² in the wet meadow. Aboveground production of 28-45 g m² was approximately 50% that of comparable low arctic sedge communities. Michael Muc (1977:169, 170, 179). (Table 4).

Ecology and primary production of Raised Beach communities,

Truelove Lowland

Growing season on raised beaches of Truelove Lowland, Devon Island

1970: 60 days (20 June – 18 Aug)

1971 55 days (15 June – 8 Aug)

1972 45 days (5 July – 18 Aug). - J. Svoboda (1977:199)

Intensive Raised Beach Site: Protein content averaged ca. 5% to 7% (Table 15). Both protein and phosphorus were lower in raised beach, than in meadow plants. Relatively high amounts of crude protein were found in humus and litter, probably due to the presence of soil microorganisms and invertebrates. A high content of crude fibre (ca. 50%) suggests the low digestibility of these plants, except for their minute green parts. On Intensive Raised Beach Sites: Protein content averaged ca. 5% to 7%. – J. Svoboda (1977:210)

Chemical composition of plants. Adapted from J. Svoboda (1977:211) Table 15. Percentage (air dry basis) on Raised Beach Site, Truelove Lowland, Devon Island. Average of harvests. Harvested I (22 June), 3 (7 July) 8 August).

Energy content of plants on Truelove Lowland, Devon Island

Dryas integrifolia (5259 cal/g)

Arctic herbs (4840 cal/g), compared to alpine herbs (4601 cal/g)

Arctic willow S. arctica in meadows (5106 cal/g), on raised beaches 5317 cal/g and 5317 cal/g. Alpine willows (Salix herbacea and S. uva ursi from Mt. Washington had a caloric content ca. 4920 cal/g (Bliss 1962). J. Svoboda (1977:211).

Crude protein (N x 6.25) in aboveground parts in the Truelove Lowland ecosystem, Devon Island. Adapted from T.A. Babb, and D.W.A. Whitfield (1977:594) Table 3. The aboveground brown and dead parts of the plants on Truelove Lowland do contain so much crude protein, that the muskox should be able to maintain on them at least its body weight also in winter, if there is enough dry mass. The muskox reduces its metabolic rate in winter, just like the moose and the bison, also when it has much food. Rhizome: produces shoots above and roots below the surface of the ground.

Energy budgets and ecological efficiencies on Truelove Lowland

Evapotranspiration is a larger component here, than in the Alaskan Arctic, probably the product of the unusually high net radiation (18 kly yr) (= 18 kcal/cm² year), compared with the expected values of 2-3 kly (2-3 kcal/cm²) yr at this latitude and the measured 11 kly (11 kcal/cm²) yr at Barrow. Net radiation comprises 80% to 90% of global radiation on sunny days, but only 57% to 67% on cloudy days. High values for net radiation help to explain, why these areas are more favorable for plants and animals.

Winter snow depth averaged 15 to 20 cm on crests of raised beaches and lichen barrens on Rocky Point, 45 cm in the meadows and surfaces of lakes and ponds, and 60 to 100 cm on the lower slopes and transition zone of raised beaches and the rock outcrops. During the snowmelt period, water covers most meadows. The two major habitats of the Lowland, sedge-moss dominated meadows (41%) and raised beaches (11.4%). - Whitfield, D.W.A. (1977)

Aboveground net plant production (g/m²) for the major plant communities of Truelove Lowland. The mean values are based upon 1 to 3 years of data (Bliss et al., Jefferies, Muc, Svoboda). Adapted from Whitfield, D.W.A. (1977:662) Table 3. Forbs = plants with large leaves.

Result: Truelove Lowland, Devon Island, muskox pasture

17.8 kcal/cm² yr annual net radiation at earth’s surface

Annual precipitation 185 mm

Wet sedge meadow 45 g DM/m² yr

Hummocky meadow 42 g DM/m² yr

"The boundary of tundra and taiga (boreal forest, open woodland and forest tundra): In Canada the southern limit of tundra occurs near the 75-80 kJ cm² isoline of annual net radiation, whereas in Alaska it occurs at the 67 kJ cm² isoline (Hare & Ritchie, 1972). It is important, to use integrated climatic factors, rather than single ones, such as temperature, to demarcate these vegetation zones." Bliss, L. C. (1981:8).

High Arctic

A shorter growing season (2 to 2.5 months versus 3 to 4 months);     cooler summers (July means 4°C to 8°C versus 4°C to 11°C) and degree days above 0°C (150° to 900°). Bliss, L. C. (1981:17)

Study sites: Truelove Lowland, Devon Island, Canada (75°33´N, 84°40´W) – a high arctic coastal lowland. Point Barrow, Alaska (71°18´N, 156°41´W) – a low arctic coastal lowland. Bliss, L.C. (1981:90).

"The Truelove Lowland, with a mean elevation of 25 m, is a lush site, that results from an abundance of moisture and a much higher net radiation regime, than is typical of that latitude, as calculated by Hare & Ritchie (1972) (Courtin & Labine, 1977). It is surrounded by polar desert vegetation, that reflects a continental high arctic climate, in spite of its proximity to the Arctic Ocean. This is, because the ice-free period of the year, coinciding with the growing season, is very short – no more than four to six weeks." Bliss, L. C. (1981:90).

Overwintering

"During the summer, herbaceous vegetation stretches from horizon to horizon, and food seems superabundant. However, with the onset of winter, translocation of nutrients and the death of leaves lowers the quality of forage, and wind-packed snow makes most of the midsummer standing crop unavailable.

"Herbivores, with sufficient mobility, simply leave the tundra during winter and go to more favourable ranges. ... Many caribou and reindeer leave the tundra, to enter adjacent forested ranges, or more exposed alpine areas, where snow is soft or shallow and where lichens can be readily obtained. Sedentary species, such as muskox, move short distances to areas, where snow conditions favor foraging. Muskox rarely eat significant mounts of lichens, their main winter diet consisting of dead and frozen grasses and sedges." Bliss, L.C. (1981:365)

Devon Island Muskoxen

"When considering those areas, occupied by muskox, 23% of the above-ground forage available in the preferred habitat on the entire lowland. Summer grazing of the Truelove Lowland is highly sporadic and muskox are virtually absent during periods of melt-off (May-June), and during the period August to February. ... The year-round quality of the muskox diet may be moderately high and not as variable as that of Rangifer, as the energy content of monocotyledonous plants remains constant at 19.8 kJ (2.389 kcal) g organic matter (Muc, 1974), the digestibility is estimated at 62-75% (Hubert, 1974, 1977) and the respective summer and winter nitrogen content of the diet is approximately 3.0 and 1.7%." White, R.G. (1981:429).

In summer: 3.0% nitrogen (N) x 6.25 = 18.75% CP (dry weight)

In winter: 1.7% N = 10.625 % CP (dry weight)

"Previous studies with grazing herbivores in temperate grassland systems show, that the availability of forage limits intake of digestible organic matter below a total biomass (dry matter) of 200-220 g m², or an available green biomass of 0.25 x 200 or 50 g m².

"Predictions of the amount of available green biomass, which would support maintenance of body weights in lactating and non-lactating reindeer, are respectively 35 and 25 g m², which is in good agreement with field results of 30 to 40 g m² for sheep and 30 to 37 g m² for lambs. Hence, although the total aboveground biomass of vascular plants may frequently be in excess of 100 g m², for most for the year the amount of green or preferred material may be less, than 30% of this figure, and a decline in body weight of animals would be expected. At biomass levels below 20 g m², feeding time must be maximised." White, R. G. (1981:439-441). 

Musk-ox herds form a defence circle with horns out, keeping the young in the middle. From: Bernard Stonehouse, Animals of the Arctic - the ecology of the Far North (1971:110)