Summar y of the total botanical interest

The Glen Coe survey area has a great diversity of vegetation and habitat types including several which are uncommon in Britain or Europe, and a rich flora including several rare species. These combine to make the site one of the most botanically interesting places in the British uplands. The most notable habitats here are: ● Snow-beds (U11, U12, U14, U18 and Pohlia ludwigii types) on the north side of the main Bidean ridge. Diverse, extensive and containing several nationally uncommon species, these are some of the most impressive examples of snow-bed vegetation in the west Highlands. They are nationally important. ● Basic igneous crags and associated tall herb vegetation (U15 and U17) and flushes (M11 and M12) on the north side of Bidean. Nationally important populations of some rare montane plants, including what may be the largest populations of Saxifraga cernua and S. rivularis in Britain.

● Bryophyte-rich heaths (H20c and H21b) on the north-facing slopes on Bidean, the Three Sisters and Buachaille Etive Mór. These heaths contain excellent, internationally important assemblages of northern, sub-montane and montane oceanic liverworts. This is around the southern limit of the very rich northern oceanic liverwort assemblages which occur from here northwards through the western Highlands. ● Rocky, bryophyte-rich woodland (W17) on the very steep N slopes on the NE end of Gearr Aonach,

and stretching from the Allt Coire Gabhail boulder-field and ravine down to the confluence with the River Coe (‘Meeting of Three Waters’) and further downstream along the River Coe. Taken together, these two areas of woodland form one of the richest sites for oceanic bryophytes in Britain.

● Excellent, internationally important examples of western, oceanic blanket bog (M17 and M18 with M1 and M3) in two areas in the NE of the survey area – NE of Buachaille Etive Beag and Buachaille Etive Mór. This is ‘top quality’ bog because of its floristic diversity, microtopography, good Sphagnum carpets and apparent lack of disturbance in the past.

● Limestone area on the steep NE and N slopes of Meall Mór: grassland (CG10, CG11, CG12, U4F, U5c and M25c), flushes (M10 and M11), tall herb vegetation (U15 and U17), woodland (W9), Dryas heath (CG14) and Salix myrsinites scrub (W20). A diverse mixture of vegetation types, with a very rich flora of calcicole species, some of which are nationally uncommon. Rather like a north-western outlier of Breadalbane-type calcicolous vegetation. Nationally important.

Among the various ecological divisions in the Scottish Highlands, two are particularly important with regard to vegetation. One is between the east and the west. The west has a more oceanic climate and the east a more continental one. There are corresponding differences in the typical vegetation: most notably the greater abundance and diversity of bryophytes in the west. Glen Coe is on the western side of this division, with very good bryophyte-rich heaths and woods, and fine examples of wet blanket-bog. The other ecological division is between areas with predominantly acid rocks and those with a greater extent of base-rich rocks. The Glen Coe hills have both acid and basic rocks: there are very good examples of acidophilous woods, heaths, bogs and snow-beds, and some of the best examples of basiphilous vegetation outside the Breadalbanes.

Other parts of the western Highlands have mixtures of vegetation types similar to that on the Glen Coe hills. On the Mamore Forest, to the north across Loch Leven, there is a similar range of dwarf-shrub heaths including Dryas octopetala heath CG14 and liverwort-rich Calluna-Vaccinium-Sphagnum heaths H21b. There are herb-rich Festuca-Agrostis-Thymus CG10 and Nardus U5c grasslands, Rhytidiadelphus loreus

snow-beds U13b, Trichophorum-Eriophorum blanket bog M17 and birch woodland W11 and W17. These types of vegetation also occur on Ben Nevis. Ben Nevis is higher than Bidean nam Bian and has a large plateau where snow collects; snow-bed vegetation is more extensive there and on the adjacent peaks than it is on Bidean. Saxifraga cernua and S. rivularis also grow on Ben Nevis, although they are not known from any other hills in this part of the country. The hills around Glens Affric and Cannich also have much snow-bed vegetation, including large patches of Rhytidiadelphus loreus snow-bed U13b and Cryptogramma-Athyrium snow-bed U18. They have tall-herb ledge vegetation U16 and U17, montane willow scrub W20 on cliffs, pine woodland W18, western Trichophorum-Eriophorum blanket bogs W17 and bryophyte-rich heaths. They are as far west as Glen Coe but are further from the sea. Though there are oceanic elements in the flora and vegetation, there is not such a rich flora of oceanic bryophytes, and many of those that do occur grow in the montane heaths and snow-beds where they are protected from frost by a layer of snow in winter. There are also Calluna-Cladonia heaths H13, Vaccinium-Cladonia heaths H19, Carex-Polytrichum sedge heaths U8 and Juncus trifidus heaths U9: all eastern, boreal types of montane vegetation. There are hills further west, such as Ladhar Bheinn in Knoydart, which are almost as high as Bidean and have similarly rich assemblages of oceanic plants and vegetation (e.g. Averis 2001). However, although the precipitation is still very great, these more western hills have less snow-bed vegetation, none of the eastern vegetation types such as Calluna-Cladonia heath H13 and Carex-Polytrichum heath U8, and fewer montane species than the Glen Coe hills.

The hill slopes between Sgorr nam Fiannaidh and the Pap of Glen Coe, outwith the study area to the west, are made of Dalradian quartzite. Although this ground is adjacent to the study area, its flora and vegetation are quite different. There is much more heather and very little grassland. There is Calluna-Vaccinium- Sphagnum damp heath H21, Calluna-Eriophorum blanket bog M19 with much Rubus chamaemorus, and on the upper slopes large patches of Calluna-Racomitrium heath H14 on gravelly, windswept ground. The montane species Loiseleurea procumbens is common here.

The Polytrichum-Kiaeria and Salix-Racomitrium snow-beds U11 and U12, the Alchemilla-Sibbaldia snow-bed U14 and the Pohlia ludwigii snow-bed occur in intricate and quite bewildering mosaics in the upper corries of the study area. These communities have many plants in common, and the distribution of individual species seems to be quite random, though there may be subtle differences of shelter, shade, wetness of the soil and duration of snow-lie on a very small scale. Much of the vegetation in the upper corries does not fit neatly into an NVC category. Though the individual types can be recognised here and there, all possible intermediates also occur and, in fact, cover more of the ground. In the west Highlands, only Ben Nevis and the adjacent hills are known to have more extensive and better-developed snow-beds than those in Glen Coe. These two ranges of hills, because of their great height and the high precipitation they receive, have the best examples of these types of vegetation outwith the eastern and central Highlands. On both sites these acid snow-beds and tall-herb vegetation on base rich ledges occur in unusually close proximity. Another interesting element in the vegetation of both Bidean nam Bian and the Ben Nevis range is Racomitrium heath in which the dominant species is R. ericoides rather than R. lanuginosum. We found this type of vegetation – identical to the normal Carex-Racomitrium heath except for the dominant species – on the summit of Stob Coire nan Lochan on gravel and shattered stone. Similar heath was discovered by McVean & Ratcliffe (1962) on the summit of Aonach Mór east of Ben Nevis. On that hill it is (or was) more extensive, covering some tens of square metres where wind-blown sand from nearby eroded surfaces was continually being added to the vegetation. R. ericoides can tolerate repeated burying by sand and shingle.

It is exactly this which enables it to colonise riverside shingle and the edges of tracks. On Stob Coire nan Lochan there is no obvious sand, and no obvious reason why R. ericoides should take the place of R. lanuginosum. Its occurrence here is interesting, though, because R. ericoides is the dominant species in some moss heaths in Iceland and Jan Mayen Island (McVean & Ratcliffe 1962) and over small areas in the hills of the Faroe Islands (Hobbs & Averis 1991).

The Salix myrsinites scrub W20 on Meall Mór is very interesting. Pure scrub of S. myrsinites is rare. The species is more common as a component of more mixed willow scrub including such species as S. lapponum and S. arbuscula. Pure S. myrsinites scrub in Britain seems to be a community of limestone. Elsewhere it occurs at Inchnadamph in Sutherland and at Rassal in Wester Ross. In these two places it occurs at low altitudes on dry limestone, without the rich underlayer of tall herbs. The scrub on Meall Mór, with its tall swards of herbs on dripping limestone ledges, is more like the mixed willow scrub in the Breadalbane hills than it is like the low-altitude scrub in the far north west. Dryas octopetala is one of the few species common to both. D. octopetala is a plant of open ground and it is rare to see it growing under trees and shrubs, as it does here. It also grows under birch trees on the limestone in Strath Suardal on Skye (Averis & Averis 2000), and under hazel in the Burren in western Ireland (Mabey & Evans 1980).

The birch woods in Glen Coe have a rich flora of oceanic bryophytes. There are woods with a similar array of species in Glen Nevis and Glen Creran (Averis 1991) and in Knoydart (Averis 2001). These woods are notable because northern liverworts such as Scapania ornithopodioides and Plagiochila carringtonii, generally plants of moderate to high altitudes, grow in them. It is also notable that more southern species, such as Bazzania trilobata and Saccogyna viticulosa, grow in mixed mats with the northern and montane plants. This tends to happen most often where the climate is very oceanic. Species of contrasting phytogeographical distributions are able to grow together because the winters are not too cold for the southern species and the summers are not too warm for the northern species. Glen Coe is an especially good place for this. Another example is the lowland, southern species Silene dioica. It grows in the upper part of Coire nam Beitheach, at over 900m, in the company of montane plants such as S. acaulis, Saxifraga cernua, S. rivularis, S. nivalis, Poa alpina and Cystopteris montana. Yet another example is the normally montane Empetrum nigrum ssp. hermaphroditum. This species occurs here not only at high altitudes on the mountains but also low down in the wooded boulder-field of the Allt Coire Gabhail.

Several of the oceanic bryophytes which grow so prolifically in the woods also occur on the open slopes. Herbertus aduncus, Pleurozia purpurea, Scapania gracilis, S. ornithopodioides, Plagiochila spinulosa, P. carringtonii, Mastigophora woodsii, Mylia taylorii, Bazzania tricrenata, B. pearsonii, Anastrepta orcadensis and Lepidozia pearsonii form the hepatic mat community which makes up the characteristic bryophyte layer of liverwort-rich Calluna-Vaccinium-Sphagnum heath H21b and, with the addition of the more montane Scapania nuimbosa and Anastrophyllum donnianum, of liverwort-rich Vaccinium-Racomitrium heath H20c. More unusually, many of these species grow in their characteristic mixed mats in damp Festuca-Agrostis- Galium grassland U4d, Trichophorum-Erica wet heath M15, Oreopteris limbosperma and Pteridium aquilinum fern communities U19 and U20, and in Crypyogramma-Athyrium snow-beds U18. They occur from the foot of the main glen at about 100m to over 900m in the high corries. Only in the far west Highlands are these species so widely distributed through so many types of vegetation and over such an altitudinal range. The hillsides in Glen Coe are green and grazed, with little heather except on the cliffs. This pattern of vegetation is common in this part of Scotland: for example on the hills in Glen Etive, the Black Mount,

Beinn Dòrain, Beinn an Dòthaidh, Beinn Cruachan, Ben Lui and the western Breadalbanes. This is almost certainly because of the great intensity of grazing where the rocks are rich and the herbage nutritious. All these hills have similar vegetation on their long green slopes: mixtures of sub-montane Vaccinium- Deschampsia heath H18, Nardus-Galium U5 and Festuca-Agrostis-Galium U4 grasslands, Oreopteris limbosperma fern beds U19 and bracken U20.

One of the more interesting types of grassland which we found on the slopes of Meall Mór is the herb-rich form of Festuca-Agrostis-Galium grassland U4F. This is a rare grassland community which seems to occur only on steep slopes which are flushed with moderately base-rich water and which are not grazed too hard. We have found it on Mull (Averis & Averis 1995b, 1999b), Beinn Eighe (Averis & Averis 1998) and on Ben Lui (Averis & Averis 1999a). We have seen more of it on Ben Lui than anywhere else: it has become very extensive on the north-facing slopes since the sheep flock was sold. It was also good to see examples of herb-rich Juncus squarrosus heath U6R and Deschampsia cespitosa grassland U13ahr. Both occur in the Breadalbane hills and over richer rocks in the north-west Highlands, but neither is described in the NVC. The Glen Coe hills are not far from Ben Lui and the western Breadalbanes. Bidean nam Bian is only about 15km west of Ben Lui, but its vegetation and flora are considerably more oceanic. Many of the oceanic bryophytes which are so plentiful in Glen Coe do not grow on Ben Lui at all, showing the very steep gradient of oceanicity inland from the west coast. Ben Lui, like Glen Coe, is within the range of native pine woodland and there are some fine surviving examples of Pinus-Hylocomium woodland W18 in lower Glen Cononish. There is Trichophorum-Eriophorum bog M17 there too, but it is much more degraded by burning and heavy grazing than that in Glen Coe. The oceanic snow-bed communities Rhytidiadelphus loreus snow-bed U13b and Cryptogramma-Athyrium snow-bed U18 are much less extensive on Ben Lui and the adjacent hills than they are in Glen Coe, but there are more lichen-rich heaths, and more Calluna-Eriophorum blanket mires M19 on Ben Lui. Carex saxatilis mires M12 are common on Ben Lui as they are throughout the Breadalbanes. There seems no reason why this type of vegetation should be so scarce on the Glen Coe hills. The tall-herb ledge vegetation on Ben Lui, as elsewhere in the Breadalbanes, is tall, lush and luxuriant, forming vertical gardens of grasses, ferns and flowering herbs. In the Glen Coe hills, only the limestone crags of Meall Mór have anything like the typical Breadalbane tall-herb ledges and herb-rich woodland and scrub on crags. Alhough there is much Luzula-Geum vegetation on Bidean nam Bian and its satellite peaks, most of it, and certainly the patches with the more interesting rare species, belongs to the Alchemilla-Bryum sub-community U17a. U17a has a more open, patchy and shorter sward than the Geranium sub-community U17b which is so noticeable on Ben Lui and on the other Breadalbane hills with basic rocks.