23 
If this reasoning is correct, then the oldest forest in Wood Buffalo park 
is that of lodgepole pine Pinus contorta var. latifolia, and black spruce 
Picea mariana, on the summits of Caribou plateau which stood above the 
1,600-foot post-Glacial lake. It may be considered comparable in age with 
the woodlands of the Cretaceous uplands to the southward, where advanced 
fir-spruce forests abound, and in both age and floristic content with the 
Cordilleran forest of the upper Peace drainage. Certain areas of it may 
have been exposed to plant cover during at least the later advances of 
Pleistocene ice. 
Dry ridges and sand-plains on the morainic uplands are usually clothed 
with an open woods of jackpine Pinus banksiana . The dryness, the park- 
like aspect, and the scarcity of undergrowth have made these ridges the main 
routes of travel for generations. The wood bison early sought them out 
for migration lines between summer and winter feeding grounds, and have 
worn their characteristic deep trails in them. In its simplest form this 
wood consists of a pure stand of the pine, 'with ground cover mainly of 
reindeer lichens Ciadonia alpestris, Cetraria nivalis , and others, broken 
here and there by small patches of cranberry V actinium Vitis-idaea var. 
minus , 
The lowering of the levels of the morainically dammed lake that 
stood in Moose Lake basin has exposed low, sandy ridges, some of which 
are now only a foot or two above the surrounding muskegs and small lakes. 
These ridges show the jackpine timber in its simplest form and indicate 
that it is the initial vegetation on such ground now developing. Similar 
evidence is to be found on the east shore of Pine lake, where a series of 
abandoned curved sand spits bears an open pine woods and shows that the 
lake level has fallen in recent geologic time. The question as to Whether the 
pine woods was the original vegetation on the higher ridges when these were 
exposed after the withdrawal of the 1,100-foot lake has not been solved, but 
the writer is inclined to think that such was not the case (52) . The habits 
and range of Pinus Banksiana at the present time indicate that it is not a 
tree of the most exposed sub-arctic timber. It has only a few scattered rep- 
resentatives in the country just south of the timber-line, where its normal 
habitat on rocky and sandy ridges is taken by Canada spruce. In Wood 
Buffalo park there is a high sandhill southeast of Lane lake which stands 
out prominently above the surrounding country. The pine disappears on 
its upper slopes where there is a park-like timber of spruce similar to that 
near the timber-line far to the northeast. The lichen mat on the hill-top 
shows also a more boreal character, with Cetraria islandica an abundant 
species. It seems reasonable to suppose that Canada spruce was the first 
timber on some of the ridges, at least, and that it has persisted in the more 
exposed places. The park-like spruce woods would probably be easily 
invaded by jackpines if they occurred at a lower level. 
Older pine woodlands show all stages of a transition to the richer 
spruce forests of the lower slopes. There appears to be little question that 
the normal course of development, when undisturbed, is to spruce. Many 
of these stages are clearly shown in the vicinity of Pine lake where the 
writer has studied them on several occasions. The first changes come with 
the introduction of a scattering of shrubs and perennial herbs, and with the 
