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feather mosses is associated with small groups of evergreen herbs
and Equisetum sp .
Vegetation on sandy dunes, gravelly-sandy beaches and terraces
is dominated by pure or mixed pine, birch,
aspen and white spruce
forests . Here again, succession is toward the white spruce type .
Repeated fires, however, maintain large areas of pine and birch .
The shrub layer is dominated by Shepherdia canadensis , Rose sp . and
Juniperus communis . The herb and moss layer is dominated by Cornus
canadensis, Pyrola spp ., Lecopodium spp ., Arctostaphylos uva-ursi ,
feather mosses and lichens .
In Zones 2 and 3, on well and imperfectly drained mineral soils,
black spruce becomes dominant, especially on the imperfectly drained
sites . On perennially frozen soils black spruce with a thick carpet
of feather mosses forms the dominant forest cover .
The timberline occurs at 3,800 feet in the Nahanni Butte area .
The timberline further north, on Cap Mountain, is found at an
elevation of 3,300 to 3,400 feet . It is interesting to note that
alpine fir forms the timberline in the Nahanni Butte area, while
in the Cap Mountain area alpine fir
is absent and white spruce forms
the timberline . Above the timberline, on mineral soils, typical
alpine tundra vegetation is found .
On patterned ground, nonsorted circles, and hummocks in Zones
2, and 3, the tree layer is composed dominantly of black spruce
with some larch and white birch also being present .
The shrub
layer is composed of Ledum groenlandicum , L . decumbens , Betula
glandulos a, Alnus crispa , Vaccinium spp . and Rubus chamaemorus . The
herb and moss layer contains lichens (Cladonia alpestris , C . Mitis ,