Uplands invariably have areas of localised
surface water seepage with mire
vegetation which usually contrasts strongly with that of the blanket mires. These
areas are often associated with emergent drainage water from springs, rills or
flushes, and they occur on slopes of varying steepness and amongst a wide range
of other vegetation, from dry grasslands and heaths to blanket mire. Soligenous
mires of this kind are often especially well developed on the lower glacial drift-
covered slopes and on the valley floors of the steeper mountains, but they occur
high up into the montane zone where they are often associated with prolonged
snow cover. Individual examples are usually small (less than 5 ha) but in the
aggregate they sometimes cover quite large areas of an upland massif. The
underlying peat is usually shallow (less than i m) and many examples have peaty
gley soils rather than true mire peats. Though widespread all over the hill country of
northern and western Britain, soligenous mires are better developed and more
varied in high rainfall areas than on some of the dry eastern moorlands.
As acidic, base-poor rocks predominate
in the British uplands, the commonest
types of soligenous mire are oligotrophic, typically with a Sphagnum lawn
composed of species (e.g. S. recurvum] which need moving water, and a Carex
sward with species such as C. echinata, C. nigra, C. curia and Carex rostrata. This
bears obvious resemblances to lowland poor-fen communities of other mires. High-
altitude Highland examples locally have montane species such as Carex aquatilis,
C. rariflora, C. bigelowii and Sphagnum lindbergii. The most widespread type of
soligenous mire, occurring in nearly all the British uplands, is one dominated by
Juncus effusus, with variable ground cover of Sphagnum recurvum, S. palustre and
Polytrichum commune. Oligotrophic Juncus acutiflorus mires with Sphagnum carpet
occur in parts of western Scotland, and grade into a still more widespread
community with Myrica gale and tussocky Molinia caerulea; whilst Molinia caerulea
occurs still more widely as a dominant of flush mires without Myrica, and with a
variable cover of Sphagnum. Juncus squarrosus-Sphagnum flush communities
occur widely on acidic mountains.
The mesotrophic soligenous mires typically
have a moss layer composed of the
relatively basiphilous Sphagnum spp. (e.g. S. teres, S. contortum, S. squarrosum,
S. subsecundum, S. warnstorfianuni) and/or Bryalean mosses such as Aero-
cladium cuspidatum, Aulacomnium palustre, Mnium pseudo-punctatum and Bryum
pseudotriquetrum, with a mixed sedge-forb sward containing Carex nigra, C.
demissa, C. panicea, C. pulicaris, C. hostiana, Leontodon autumnalis, Prunella
vulgaris, Ranunculus acris and Euphrasia officinalis agg. Carex rostrata may be the
dominant sedge and Juncus acutiflorus sometimes replaces the carices as
dominant vascular plant; J. squarrosus also does so on some of the basic Scottish
mountains. These mesotrophic communities occur widely on the more basic
mountains but are somewhat local. They grade into markedly eutrophic mires on
calcareous mountains, notably those of Carboniferous Limestone in northern
England and Dalradian mica-schists and limestones in central Scotland. The
calcareous soligenous mires typically have a carpet of' brown mosses' usually
containing the same mixture of species (e.g. Scorpidium scorpioides, Campylium
stellatum) as those of the lowland rich-fens but with northern species (e.g.
Cinclidium stygium) often present. There is a variable development of a sedge-forb
sward, containing many of the species found in the mesotrophic examples, but
greater constancy of others such as Carex lepidocarpa and Eleocharis
quinqueflora. In western Scotland these upland rich-fen communities merge into
lowland counterparts, as on the wet machairs, and on both shell sand and limestone
.there is a characteristic type dominated by Schoenus nigricans, with few other
species. At high levels, both the mesotrophic and eutrophic soligenous mires often
occur in complexes with basic flushes and springs, the whole being an especially
favourable habitat for many montane base-demanding plants of wet ground.
An interesting feature of soligenous mires
is that various kinds of mixtures of poor
and rich communities frequently occur. Sometimes there are fairly obvious spatial
changes in nutrient content of the water supply, giving a sudden separation of
contrasting communities. The more puzzling examples are various types of mosaic
pattern of poor and rich communities, especially those involving a vertical
.separation of the different components.
Soligenous mires differ from the topogenous
lowland .mires in having a vascular
plant sward of much lower .Stature; usually this appears to be the result of the heavy
'grazing by sheep, deer or cattle which characterises the British uplands. On the
poorer mountains, such flushed .sites often carry the most palatable vegetation and
are selectively grazed. As well as reducing the stature of the sward, .this grazing
tends to suppress completely the shrub and tree growth so usually present in
Scandinavian counterparts (within the altitudinal limits of shrubs and trees).
Probably most British soligenous mires, except the high-altitude examples, would
carry growths of willow and perhaps birch in the absence of grazing. Grasses and
sedges also probably tend to increase in abundance at the expense of forbs and
bryophytes. Some soligenous mires have been modified by deliberate draining,
which promotes conversion to grassland or heath, or allows the planting of trees,
but on the whole .these mires are not deliberately altered. Some examples
,become so heavily charged with water during exceptional .rainfall that landslips
occur and destroy them.
Soligenous mires obviously intergrade
with the seepage areas often found within or
along the edges of blanket mires, and the wetter types of community which
sometimes regenerate in the gullies of eroding blanket mires are best regarded as
soligenous mire. Similarly, there is no distinct line of demarcation between this
class and valley mires, although the latter are more typically lowland and southern,
.with usually a rather larger area and deeper peat. In hill country the placing of a
particular mire in one of these two classes is sometimes an arbitrary procedure.
The more distinctive types of soligenous
mire association are listed in the
classification of upland vegetation, p. 297.
