Little Assynt: lochs, rocks and lichens

April 10th 2021

Little Assynt: lochs, rocks and lichens

After very mixed weather for a week or more, the forecast for Saturday 27th March 2021 looked fair.  Neither of us had recently visited Little Assynt, so we drove to the Field Car Park and walked the Loop and Ken’s Paths east to west. It was also another opportunity to add to the Field Club’s Little Assynt Wildlife Project.

The Loop Path is sheltered to begin with (photo 1), but opens out at the junction with the Link Path, where there is a steep pull up to the high section north of Gob Ard.  This gives a good view across Loch na h-Innse Fraoich (loch of the heathery islands) to the western flanks of Quinag (photo 2).

Our first stop, for hot drinks, was on this section, overlooking an un-named loch at NC157263 (photo 3).  Beside the path was a clump of hare’s-tail cottongrass Eriophorum vaginatum, first of the ‘sedges’ to flower (photo 4); the single, fluffy, fruiting heads from which it gets its name come later.  The loch was visited in 2018 (see Torr Mor, Bryophytes and Desmids, 29th March 2018), when vegetation from a pool near its exit burn yielded a desmid alga Cosmarium tuddalense new to the British Isles.

A conspicuous small rock in its northern half often raises hopes of divers, dashed on closer inspection through binoculars.  Gwen thinks the loch should have a name.  She suggests either ‘Loch with the rock that looks like a bird’, or ‘Ear Loch’ from its general shape.  Can anyone render these in Gaelic?

Loch an t-Sabhail

A little further along the high path, the two lochs associated with the old settlement of Loch Beannach Farm came into sight (photo 5) and we dropped down a steep tussocky slope to the eastern shore of the southern one, Loch an t-Sabhail (loch of the barn).

On our way we passed a dark rock outcrop (photo 6-7) with the rough texture and pitted surface indicative of the ultra-mafic dykes that slice occasionally through the Lewisian gneiss.  In its crevices were clumps of the tough, shiny, over-wintering fronds of black spleenwort Asplenium adiantum-nigrum; the tips of which had been frosted (photo 8).  This fern is often found on ultra-mafic outcrops.  Shortly afterwards we spotted a tiny colourful moth caterpillar on heather (photo 9), later identified as a first instar northern eggar, very different from the later large hairy stages.

A mafic crag

We worked our way along the eastern shore of this loch and then up the exit burn from that above it, Loch an Ruighein (loch of the sheiling).  Just to the east of the burn there is a north-facing wet, shady, crag housing a few scraggy trees of downy birchand rowan and coated with ferns, mosses, liverworts and lichens (photo 10).  The rock appeared to be that of one of the more numerous mafic dykes that also slice through the Lewisian gneiss.  Its barer areas bore numerous tight cushions of a pale-grey lichen, looking like coral close-up, a species of Sphaerophorus, possibly S. globosus (photo 11).  Some cushions are so neat they look as if they have been trimmed.

On peat hanging down the crag Gwen noticed clusters of tiny orange fungi, with some larger examples nearby (photos 12-14). They were a gill fungus (or basidiomycete) called Lichenomphalia alpina, which is associated with a green alga Coccomyxa to form one of a small number of basidiolichens.  The ‘bobbly’ green cells of the alga form a mucilaginous mat around the bases of the fungal fruiting bodies.

At the base of the crag were the large grey thalli of the common, but very handsome, dog lichen Peltigera membranacea (photos 15-16), in which a more customary ascomycete fungus is partnered by the cyanobacterium Nostoc.  The thalli are fringed with numerous shaggy rhizines which help to attach them to their mossy substrates but, unlike roots, are not involved in the uptake of nutrients.

Loch an Ruighein

From below this crag, we had a very good view of the nearest of several islets in this loch. They carry well-grown examples of prostrate juniper Juniperus communis nana, which is the only form found in the north-west (photo 17).  It is now restricted locally to areas that are not burned or heavily grazed by deer, such as loch islands.

We had our lunch on the shore of the loch west of the exit burn, where a heathery bank provided some shelter from a chilly wind (NC154266).  It also gave us great views, across the loch, of the lichen-speckled rock rampart on its northern side (photo 18) and old sheiling grounds below (Am Ruigheam).  This rampart is another, very striking, example of a mafic dyke.  The term mafic has replaced the older one basic and relates to the metal-rich composition of the rocks (ma for magnesium and f for ferrum or iron).  We were also treated to the spectacle of a golden eagle drifting along the ridge above the rampart and away to the west.

We then made our way over old cultivation ground to the north of the former settlement and back to the Loop Path, noting on the way some partially-frosted frogspawn, two teal off the southern end of Loch an t-Sabhail and a cock stonechat.

Ken’s Path

Taking the slightly more strenuous option, we climbed up to the viewpoint overlooking Loch Beannach (photo 19), recollecting our boat trip on it the previous autumn (Loch Beannach: a visit to the largest island, 5th September 2020).  The margins of the path provided the first flowers seen this year of colt’s-foot, a solitary one of lesser celandine, and two colourful late instar caterpillars of the drinker moth, shortly to pupate.

The construction of this and the other paths on Little Assynt may have substantially extended the range of the local moles.  We suspect that they were previously more or less restricted to the richer soils of old cultivation and sheiling grounds, but molehills are now a regular feature along path margins (photo 20).  Path building and maintenance improves drainage, creates linear grasslands and must have augmented the local earthworm populations.  Molehills are an unexpected by-product of improved access, together with a more diverse if at times ‘weedy’ flora, and basking sites for reptiles such as adders.

Back to the start

The last section of the Loop Path is about a quarter of the whole circuit (4.5 km in all), and since rain clouds were fast approaching from the south-west, we did not dawdle.  However, we did note the use of the path by a fox, which had left malodorous scats in conspicuous spots alongside it, to mark its passing.

There was just one further observation to log.  On a ridge between two of the hollows on the path is a small viewpoint (NC148257), with three flat-topped rocks as seats (photo 21).  Pausing for a breather, we noticed that one of them bore thalli of an odd-looking pale-grey lichen, with creamy-buff warty growths (photos 22-23).  It was Placopsis gelida, a species once thought to be rare in the far north-west.  The ‘warts’ are composed of the cyanobacterial photobiont, and the lichen seems to colonise recently-exposed faces of mineral-rich rocks, as here in (relatively) recently-quarried material or in new roadside cuts.

So, an enjoyable walk, snatched out of a run of poor days, with excellent views over some of Little Assynt’s many lochs, a variety of lichens, which are at their most obvious in the winter, and a golden eagle as bonus.

 

Ian M. Evans and Gwen Richards

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