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Zone 6S is typical of the black spruce-feathermoss-Ledum groenlandicum
type . In Zones 4, 5 and 6N the black spruce is more open and the lichen
cover becomes dominant with both Ledum sp . being present . In Zones
2 and 3 these peatlands are covered with a very open black sprucelichen-Ledum
decumbens type of vegetation .
The vegetation on the Mesisols associated with peat polygons
(see Figure 4) is dominantly Cladonia alpestris (approximately 75
percent cover) and C . rangiferina with clumps of Ledum decumbens
and Empetrum ni rum also being present . Dichranum sp . and Sphagnum sp .
represent the mosses, the latter being dominant in the moist polygonal
trenches (see Plate 2A and Plate 3A) .
Physical and Chemical Characteristics :
The fiber content of Mesisols
(see Appendix I : Tables 1 to 3) developed from fen peat materials
is moderately to moderately well decomposed with the exception of
Drepanocladus fen peat which is undecomposed . Those developed from
forest peat materials are moderately decomposed with various amounts
of wood present . The pH of these soils varies greatly, reflecting
the chemistry of the peat parent material .
Mesisols developed from
fen peats are medium acid to mildly alkaline (pH 5 .6 to 7 .5) . The
surface layer of the soil has a higher pH (neutral to mildly
alkaline) and the pH decreases with depth to become medium to
slightly
acid .
On the other hand, Mesisols developed from forest peat materials
range from extremely acid to strongly acid . Here, the surface layer
of the soil is more acid and the acidity decreases with depth .
This is due partly to the thin sphagnum peat surface layer which has
a low pH and partly to
the fact that most of these soils are perennially
frozen .
Water migration into the frozen core increases the nutrient