Manitoba displays a large range of vegetation types that are arranged with a climatically determined north/south zonation. Grass-covered areas in the south give way to parkland and forested areas further north and eventually to shrub tundra in the extreme northeast.
In southern and west central Manitoba, agriculture, grazing, forestry and urban development have drastically altered the natural vegetation, but vast areas in the north and northeast are in near pristine state. Vegetation that often obscures the earth’s surface is clearly shown on air photos; particularly useful are colour infrared images that can detect stressed areas. Wetlands cover about 40 percent of Manitoba and do not conform to the climatically determined zonal distribution of vegetation. They occur in all parts of the province and provide distinctive ground cover well shown on air photos.
Individual animals are too small to appear on all except very large-scale images. However, some animals (e.g. beaver) profoundly affect drainage systems.
5.30: Palsas in Wet Fenland South of Churchill
In this area a surficial layer of marine silt overlies silty till.[i] It lies within the area of discontinuous permafrost; i.e., there are areas where water below ground is continually frozen. A series of creeks including Alston Creek 1 and Wakworth Creek 2 drain northward ultimately into the Churchill River just off the photo to the west. Palsas—ice-filled peat mounds—are light-toned and circular to oval 3. The surrounding fen is lower, wetter, and darker 4. The fen is also darker along drainage ways 5 where the permafrost is thawed and the active layer—the layer in which ice melts during the summer—is thicker. In the area, marked 6 ridges and ponds display a reticulate pattern, giving rise to the term "net fen." There are vestiges of raised strandlines 7, now about 100 feet (30.5 m) above sea level. Above the general level of the strandlines are numerous lakes, some of which are darker-toned 8, whereas others are very light 9 due to specular reflection.
The thin white line in the west 10 is the Hudson Bay Railway leading north to Churchill. The whistle point Bylot 11 is located at the bend in the line. Construction began at The Pas in 1910 and was completed on March 29, 1929. The total distance from The Pas to Churchill is 510 miles (816 km), much of it over spongy muskeg and discontinuous permafrost. The building of the line was a remarkable engineering feat, but maintenance costs over discontinuous permafrost have been high and in recent years the existence of the line has been constantly threatened. It is now owned and run by an American company.
Figure 5.30: Palsas in Wet Fenland South of Churchill
Vertical air photograph: A17406-57
Flight height: 30,000 feet a.s.l.; lens focal length: 88.28 mm