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of Slave river at the Government Hay Camp. On July 12, frost was found 
at about one foot on a hillside exposed to the noonday sun, high on the 
eastern slope of Caribou mountains. No deeply rooted plants may enter 
such situations unless they can adapt themselves. 
The effect of a constantly frozen surface below the ground-level would 
tend to lessen the amount of seepage through the soil and increase the run- 
off. In relatively undrained regions this condition assists in the the ex- 
tensive development of muskegs (bogs), with their typical vegetation of 
plants that are suitable to acid soils. The cold or cool weather, in which 
bacterial decay and humus formation are greatly retarded, has a strong 
tendency to render very slow the successive movements in ttie development 
of the vegetation which are dependent upon chemical changes in the soil. 
Such movements, also, which are dependent upon topographic change and 
the formation of new barren areas for colonization by plants, are greatly 
retarded because of the shortness of the season available for erosion and 
deposit. These retarding results are especially significant in a study of 
young vegetations just beginning their development on the recently ex- 
posed land surfaces in the Athabaska-Great Slave Lake region. 
A fruitful field for investigation that may be mentioned in this con- 
nexion is the degree to which the plants naturally selected to enter the 
region are drawn from those that are able to live with a minimum amount 
of available nitrogen in the soil. Prevailingly cold, acid soils, containing 
much raw humus, are poor in available nitrogen, and plants that inhabit 
them must either get along with this small amount or have some means of 
utilizing atmospheric nitrogen that has been fixed by other plants. 
TYPES OF VEGETATION IN WOOD BUFFALO PARK 
Coniferous forest is the predominating vegetation in Wood Buffalo 
park. Although floristically different in some respects from that in other 
regions, this forest is a part of the extensive belt of conifers that extends 
from the St. Lawrence basin to Alaska and sends its representatives south- 
ward on the mountain chains of the continent. Canada spruce Picea 
glauca, and jackpine Pinus Banksiana , are by far the commonest species 
in the timber, the former occurring mostly upon the better soils of the up- 
lands and along the major streams, and the latter being confined to semi- 
barren rocky hills, and to dry, sandy knolls and plains. 
The casual traveller along the rivers gets an erroneous idea, however, 
of the actual extent of the forest, since the banks are usually clothed with 
a rather heavy growth of it. Journeys inland, together with examination 
of aerial photographs and the maps that have been made from them, dispel 
this idea, and it is soon found that river flood-plain timber is largely con- 
fined to the banks of the present rivers. The largest continuous stands 
are to be found on the rolling country of the uplands which are bounded on 
the south by Peace river, on the east and northeast by Salt Mountain 
escarpment and the Salt Plains, and on the west by Moose Lake basin ; and 
which extend northward and northwestward across Little Buffalo river. 
Other extensively forested areas are on the eastern slopes of Caribou 
Mountain plateau. The timber is confined largely to sandy and gravelly, 
well-drained soils. 
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