35 
The Salix association passes to the spruce forest of the surrounding 
country through a narrow transition zone involving Populus tacamahacca 
much like that of the river flood-plains. In the event of burns, Populus 
tremuloides also plays an important part in the arrangement. Where very 
low land adjoins the lake the Salix association passes directly to a Picea 
mariana-Larix-Sphagnum muskeg, and the muskeg forest merges imper- 
ceptibly with the Picea glauca timber. On the low semi-muskeg shore of 
a small lake at the base of Caribou mountains Salix pyrifolia ta,kes the 
place of Salix planifolia. 
MUSKEG VEGETATION 
Hundreds of square miles in Wood Buffalo park are covered with 
muskegs, which are locally distinguished from “ sloughs ” by the presence 
of mosses that predominate in their ground cover. In the early part of the 
summer season they are wet at the surface but not thawed below a foot 
or two. By late June or early July they become soft to much greater depths 
and make formidable barriers to overland travel through the country. 
Where there has not been much standing water the surface layers begin 
to dry appreciably in August, so that they become more passable in late 
summer or early autumn. Ponds that persist throughout the year are 
abundant and are of large size in some districts. The largest muskeg areas 
in the park are in Moose Lake basin, where they are almost continuous for 
many miles. One may look westward and southwestward from the top of 
the Ninishith hills at the point where Little Buffalo river cuts through them 
and see clearly the Caribou mountains (16) 30 miles away. Only a few 
low ridges rise above the flat-lying lowlands that intervene, and nearly the 
whole area is a maze of muskegs and lakes (16). From the surface of Moose 
lake much the same view may be had. The contrast between this type of 
terrain and that farther eastward is shown by the fact that it is possible 
to travel from Fort Smith overland to Peace point in midsummer with 
almost no hindrance from muskegs. They are common on the uplands but 
are usually small and separated bv dry ridges. 
Lewis, Dowding, and Moss (36) have published excellent descriptions of 
the muskeg vegetation in the northern forest of central Alberta, where the 
results of their studies show considerable similarity to the writer’s on Wood 
Buffalo park. The general trend in the development of a mesophytic forest 
by the filling of shallow lake and pond basins described above is greatly 
modified by the introduction of bog mosses. In some places (Figure 3, H) 
these appear at the actual margin of the lake, but are more often separated 
from it by a wet meadow of sedges and other plants of the shore-line asso- 
ciations. The mosses are commonly associated with sedges and are being 
invaded by a hummocky growth of Sphagnum with typical muskeg shrubs. 
The next stage is the growth of a muskeg forest of black spruce and tama- 
rack and the gradual accession of the Canada spruce of the surrounding 
country. This trend, in a more or less complete series, may be seen on the 
shores of muskeg ponds, or may have its various later stages occupying 
whole depressions where the wetter conditions have ceased to exist. 
