A survey of the vegetation of Ben Nevis - Scottish Natural Heritage

Scottish Natural Heritage Commissioned Report No. 090 (ROAME No. F02LD01)
M15b Trichophorum cespitosum-Erica tetralix wet heath, Typical sub-community
This is one of the most extensive types of vegetation on the lower to middle slopes in the study area. M15b
is the typical vegetation of damp, shallow peat on moderate slopes in the west Highlands. It has a
variegated, patchy, tufted sward of Calluna vulgaris, Erica tetralix, Trichophorum cespitosum and Molinia
caerulea, sprinkled with species such as Succisa pratensis, Dactylorhiza maculata, Polygala serpyllifolia,
Potentilla erecta and Narthecium ossifragum. Myrica gale is common in some examples; this is one of the
characteristic habitats of this species. In Glen Nevis there are examples of M15b in which there are big
colonies of Gymnadenia conopsea. There are large patches and cushions of bryophytes such as Sphagnum
capillifolium, S. tenellum, Campylopus atrovirens, Breutelia chrysocoma, Pleurozium schreberi and the
red-purple oceanic liverwort Pleurozia purpurea. Although M15b is floristically quite uniform the structure of
the vegetation can be very variable. Where it is regularly burnt and grazed the sward consists of an even
mixture of species, entwined with the dead leaves of Molinia caerulea. Where grazing is light and the
heaths are not burnt, they can thicken up into a dense, tall, tussocky sward of Calluna vulgaris and Molinia
caerulea in which the other species are less common.
M15c Trichophorum cespitosum-Erica tetralix wet heath, Cladonia sub-community
M15c takes over from M15b (see above) on steeper slopes, on thinner, drier peats and at higher altitudes,
though there are also examples of this type of vegetation at low levels on patches of shallower peat within
expanses of the Typical sub-community M15b and on moraines and rock outcrops within expanses of blanket
bog. It is also common on cliff ledges. The sward of M15c consists of a similar array of species to that of
M15b, but tends to be shorter, more sparse and more open. It is made up of mixtures of Calluna vulgaris,
Erica tetralix, E. cinerea, Trichophorum cespitosum and Carex panicea. Molinia caerulea is common, but
generally grows as a scattering of shoots rather than in the dense tufts typical of M15b. There is a speckling
of wet heath species such as Succisa pratensis, Dactylorhiza maculata, Polygala serpyllifolia, Narthecium
ossifragum and Potentilla erecta. At higher elevations there are examples of M15c with species such as
Huperzia selago and Carex pilulifera. Despite its name, M15c in the west Highlands is distinguished
more by Racomitrium lanuginosum than by lichens. R. lanuginosum grows in conspicuous silvery wefts among
the other species. Hypnum jutlandicum is common too, and there are patches of Campylopus atrovirens,
Sphagnum capillifolium and Breutelia chrysocoma.
M15d Trichophorum cespitosum-Erica tetralix wet heath, Vaccinium myrtillus sub-community
Compared with the other sub-communities of M15, the Vaccinium sub-community is a drier form of heath
which has a more varied and grassy sward. This is made up of Vaccinium myrtillus, Erica tetralix,
Trichophorum cespitosum, Nardus stricta, Molinia caerulea, Juncus squarrosus and Calluna vulgaris,
interleaved with species such as Vaccinium vitis-idaea, Empetrum nigrum ssp. nigrum, Eriophorum angustifolium
and Agrostis canina. The more characteristic wet heath species such as Narthecium ossifragum,
Dactylorhiza maculata and Succisa pratensis are less common here than they are in the other
sub-communities. The bryophyte flora is different, too. There is an assemblage of pleurocarpous mosses
such as Rhytidiadelphus loreus, Hypnum jutlandicum, Pleurozium schreberi, Hylocomium splendens and
Plagiothecium undulatum as well as the more typical Sphagnum capillifolium. Many examples are likely to
be the result of burning – which dries out the surface of the peat – and heavy grazing, which favours
Vaccinium myrtillus and graminoids at the expense of Calluna.
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