Canisp and Loch Borralan

September 17th 2020

Canisp and Loch Borralan

On 2nd July 2020 we set out to Canisp and Loch Borralan to re-find three of our rarest local pteridophytes (ferns and fern allies).  The eastern slopes of Canisp are the only site in Assynt, and Highland, for Issler’s club-moss Diphasiastrum x issleri, out of only six in Britain and Ireland, all Scottish.  The interrupted club-moss Lycopodium annotinum, which also grows on Canisp, is widespread in Scotland, but only known from one other site in Assynt, just off the path to the waterfall Eas a’Chual Aluinn (NC2628).  Loch Borralan is one of two local sites for pillwort Pilularia globulifera, the other being Cam Loch (NC2112/2212).  This aquatic fern was once widespread in Britain and Ireland, but has been lost from many sites due to habitat destruction; it has not been found north of Assynt.

Canisp

We parked overlooking the northern end of Loch Awe, and followed the traditional path up the hill, crossing a dry section of the bed of the Allt Mhic Mhurchaidh Gheir (the burn of MacMurchaidh the Fat?; photo 1), and, running parallel to it, an impressive spate channel full of white quartzite boulders (photo 2).  We then struck off the path in a westerly direction and up the hill to a point on the 230 m contour line (NC235164), where we found the first plants in a population of Issler’s club-mosswhich runs along this rocky hill-side for some 500m. (photo 3), and is probably the most extensive in Britain.

It is closely related to much more widespread alpine club-moss L. alpinum, but distinguished by the yellow-green colour of its foliage and subtle differences in the shape of the leaves on the underside of the branches (photos 4-5).  Spore-bearing cones occur on upright stems at the end of the shoots (photo 6).  Issler’s club-moss was first found here in 1985 by Archie Kenneth, ‘an inverterate wanderer amongst our western hills’, but noted by him without a grid reference, and later re-located by Colin Scouller from Rhue, near Ullapool.

Lunch time list

Lunch was taken a little higher up the hill, with panoramic views of the lochs and hills to the east (photo 7); this is a spacious landscape, with the busy road just a distant linear feature.  The whole of this area is underlain by Cambrian quartzites, which are composed of almost pure silica and quite the dourest rock in Assynt, with vegetation that is noticeably species-poor.  We counted, as an example, all the higher plants visible from our lunch spot and could only muster nine species.

However both prostrate juniper Juniperus communis nana and bearberry Arctostaphylos uva-ursi were locally frequent in places, evidence that this landscape has not been burned, unlike much of the Assynt hill ground.  Animal life was sparse, apart from signs of red deer and red grouse, but we did find the galls of the cecidomyiid fly Oligotrophus panteli on the juniper and nymphs of the almost ubiquitous meadow grasshopper Chorthippus parallelus.  We also came across two colourful adults of the wood tiger moth (photo 8), whose larvae probably feed here on bell heather Erica cinerea, and the showy caterpillar of an emperor moth (photo 9).

After lunch we continued up the hill in a north-westerly direction for another kilometre, to the 340m contour.  Here, guided by a precise grid reference from a previous visit in 2009, we managed to re-locate a stand of interrupted club-moss, extending over a small area of a very ordinary–looking rocky hillside (photo 10), covered in heather Calluna vulgaris (NC226172).

This is a more robust plant than Issler’s club-moss, with prostrate stems sprawling through the heather (photo 11), from which arise upright ones bearing dense whorls of spiky leaves and single terminal cones (photos 12-13).  The plant gets its vernacular name from the ‘interruptions’ in the leaf cover owing to shorter leaves produced at the end of each season.  It was first recorded at this locality in May 1998.

Return from the hill

Large heath butterflies were flying as we turned to find our way back, after taking a last look up to the seemingly still-distant summit of Canisp, a further 3km across rocky ground with 500+m of climb (photo 14).  We followed the obvious path along the south side of the Allt Mhic Murchaidh Gheir, with good views of its rocky gorge (photo 15), which affords shelter to a few trees, and had a fair amount of water flowing down it.  Quite what happens to that water lower down we didn’t have time to investigate; as mentioned before, the watercourse was dry where we crossed it on the way up.

We left the path to investigate one of the large peaty tumps (photo 16), which are a prominent feature of gently-sloping quartzite landscapes here and on the eastern slopes of Quinag.  Despite questioning a number of geologists in the past, no explanation has been forthcoming as to how they came into being.  They rise several metres above the surrounding base rock, and do not appear to have accreted around boulders.  They must have formed at a time when there was extensive deposition of peat locally, but we have no idea of how they came to be so isolated.

Be that as it may, they have quite a distinctive flora, with mats of woolly fringe-moss Racomitrium lanuginosum, and patches of crowberry Empetrum nigrum.  They also serve as convenient territory markers for birds of prey and foxes, which leave pellets and scats on them.  This particular one (at NC236168) had an old bird pellet (photo 17), possibly that of a merlin, composed of amphibian and bird bones, with a scattering of beetle shards, and also a clump of the colourful coprophilous slender cruet-moss Tetraplodon mnoides (photo 18), probably on an old fox scat.   

Loch Borralan

We reached the car after a very enjoyable six hours on the hill and thought that we might round off the day with a quick look at the north-western end of Loch Borralan (NC255113), some 5km to the south (photo 19). Back in 2009, there was a flourishing population, in its sandy-bottomed shallows, of the aquatic fern pillwort Pilularia globulifera, which was shown to visiting cognoscenti of the British Pteridological Society.

We did succeed in finding some creeping rhizomes of the fern (photo 20) in one of the sparser patches of common spike-rush Eleocharis palustris, with loose material on the surface of the water that may have been up-rooted by deer or water-birds.  However they were only just beginning to develop their upright linear fronds, which can grow to 8cm, and there was no sign yet of the spherical sporocarps at the bases of the fronds from which the plant gets its vernacular name.

We also found an unusual higher plant belonging to the cress family, which flowers and fruits under water, awlwort Subularia aquatica (photo 21), a new record for that loch.

Another successful Assynt adventure, to Canisp and Loch Borralan.

Ian M. Evans and Gwen Richards

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