Exploring Quinag: upstream of Loch Airigh na Beinne

December 29th 2020

Exploring Quinag: upstream of Loch Airigh na Beinne

The striking north-facing buttresses on Quinag, Sail Gharbh and Sail Ghorm, together with the wall connecting them to Spidean Coinich, are all composed of reddish Torridonian sandstones, capped in the east by younger, grey, Cambrian quartzites.  They rise from a basement of much older Lewisian gneiss, which extends north and west to the coast.

As part of our ongoing exploration of the Quinag estate, we visited on 27th September 2020 the valley south-west of Loch Airigh na Beinne (NC2230), from which there are few wildlife records (photo 1).  All but a tiny corner of this 1km square lies on the gneiss, but it is crossed by two of the Scourie dykes which thread their way through these rocks in Assynt (photo 2).  The mafic rock of which they are composed introduces a degree of mineral-enrichment which is often reflected locally in the vegetation.

Loch

We left our cars by the old bridge over the Unapool Burn and made our way up an old fence line to the south-west, which marks the boundary of the Newton hill ground.  After half an hour we crossed a saddle and got our first glimpse of a long, narrow, un-named loch (photo 3), which is one of the sources of the Allt a’Ghamhna.  Here recording started.

Gwen’s dog, Jess, startled a pair of red grouse, which flew off over the hill and we than made our way along the southern shore of the loch.  A tall, rather elegant grass was growing in the water in a shallow bay and a sample was collected.  It was later confirmed as bog hair-grass Deschampsia setacea, a nationally scarce species, largely confined to north and north-west Scotland, for which this was a ‘new’ site.  We also saw nearby an adult palmate newt.

The loch had a range of the aquatics typically found in such acid waters, including white water-lily Nymphaea alba, the reddish emergent stems of water lobelia Lobelia dortmanna, the much larger ones of bulrush Schoenoplectus lacustris, and also bright green mats of floating spike-rush Eleogiton fluitans.

A brief detour to a smaller lochan to the north (photo 4) added the bootlace-like leaves of floating bur-reed Sparganium angustifolium.  Gwen also spotted at its edge the larval case of a caddisfly Agrypnia obsoleta, made of spirally-arranged plant fragments, which she knew from her Quinag Lochs Project (2010).

Rejoining the main loch, we came across a small caterpillar with yellow chevrons along its back.  This proved to be an early stage of the northern eggar moth (photo 5), quite unlike the large hairy larvae with which we are more familiar. Shortly afterwards, Gwen found a tiny orange club-shaped fungal fruiting body in a clump of bog-moss (photo 6).  It was later identified as an early stage of the scarlet caterpillarclub Cordyceps militaris, which is parasitic on the larvae of this and other heathland moths, albeit rather larger examples.

Lochside crag and scree

At the foot of a crag at the far end of the loch, protected from grazing by boulder scree, there was a magnificent old rowan, with ripe berries (photo 7).  We made our way over there for lunch, which we enjoyed with the sun shining brightly over the towering buttress of Sail Gharbh.  The combination of crag, scree and adjacent loch margins boosted the plant list, with an assortment of ferns, mountain everlasting Antennaria dioica, goldenrod Solidago virgaurea and pill sedge Carex pilulifera, bringing the running total to about 50 species.  Judging by their rough texture and rich lichen flora, some of the boulders in the scree (photo 8) had obviously been derived from the mafic dyke.

Down the exit burn

After lunch we started down the exit burn from the loch (photo 9), coming across the first small example of base-flushed vegetation associated with the mafic dyke.  It contained tawny, dioecious and flea sedges Carex hostiana, C. dioica and C. pulicaris, and also few-flowered spike-rush Eleocharis quinqueflora.  These are usually associated with stands of black bog-rush Schoenus nigricans; there happened to be none at this site, but it turned up later.

We then made our way north-west to a conspicuous outcrop of dyke rock (NC227304), from which we could see all the way down the valley to Loch Airigh na Beinne.  On the outcrop there was dwarf juniper Juniperus communis nana (photo 10), the only time we saw it that day.  In stony areas around its base were purplish-brown membranous mats of mountain dulse Gloeocapsa magma (photos 11-12)  This unusually large, terrestrial, cyanobacterium is not uncommon in our hills, although NBN only has one record, from the Beinn Eighe NNR near Kinlochewe.

As the valley widened, its floor became dominated by the tussocks of purple moor-grass Molinia caerulea, which does not make for easy progress.  So we decided to investigate a line of crags along its northern side (photo 13).  The first was rather dour, its only feature of interest, in this almost tree-less landscape, being a large, almost dead, rowan.  One small branch remained alive, but at its foot the rotting wood of shed branches was stained vivid green by the green elfcups fungus Chlorociboria aeruginascens.

Another overhanging crag a little further along (NC226306) proved much more productive, presumably part of the mafic dyke.  The shining fronds of black spleenwort Asplenium adiantum-nigrum were wedged into crevices and at its foot an earthy shelf housed a carpet of small herbs.  These included abundant wild thyme Thymus polytrichus, bird’s-foot trefoil Lotus corniculatus (the only time we saw it all day), sprawling heath speedwell Veronica officinalis and the aging leaves of primrose Primula vulgaris. 

Back into the valley

We then dropped back down into the valley, where a small bog pool attracted our attention.  Here we finally located black bog-rush, accompanied by a few late flowers of the dainty pale butterwort Pinguicula lusitanica, which we are always delighted to find. There was also a 3cm frog, one of several seen during the day.

Our next stop was in a small area of short grassland beside a tiny tributary burn, presumably also base-flushed from the dyke above.  Under a boulder there were a few plants of sanicle Sanicula europaea, which we often think of as a relic of former woodland.  There was more primrose and wild thyme, some fairy flax Linum catharticum and a variety of grassland species commonplace elsewhere, but very sparse in this landscape.  They included meadowsweet Filipendula ulmaria, cat’s-ear Hypochaeris radicata, self-heal Prunella vulgaris, meadow buttercup Ranunculus acris and, as a bonus, a small patch of alpine lady’s-mantle Alchemilla alpina.

Buoyed up by this, relative, rush of floral diversity, we then made our way across the valley to some steep, mossy, heather-covered, north-facing crags (photo 14).  They were conspicuous because they bore the few trees of downy birch Betula pubescens we saw that day.  They were on gneiss proper, and rather dour, adding added to our list only the birch, wood soft-grass Holcus mollis and wood sorrel Oxalis acetosella.  However, there were adjacent to the birches an assortment of colourful gill fungi, presumably mycorrhizal, including a bright red brittlegill Russula sp. and a yellowish milkcap Lactarius sp.  Nearby was a small deer exclosure, erected by the John Muir Trust to monitor woodland regeneration.

Turning for home

By this point in the afternoon, the sky had clouded over, and we were beginning to weary from negotiating purple moor-grass tussocks in the valley and slippery wet heath almost everywhere else.  Tea was taken on a hillock by a lively tributary burn off Sail Gharbh and we then turned for home up a shoulder on the south side of the valley (photo 15).  The area was not without interest, since there were a number of stony flushes, presumably enriched by run-off from dyke rock.  They contained much black bog-rush and its associates, including more pale butterwort and a small stand of broad-leaved cottongrass Eriophorum latifolium.

Reflections on diversity

We eventually reached the road after some six hours on the hill, with a list for the 1km square of nearly 90 species.  The vegetation survey of the whole of Quinag, undertaken by Ben and Alison Averis in 2006 and 2007, mapped this area generally as a mosaic of bare rock, dry or wet heath and mire, with a little open water.  The dominant plants of these communities might amount to some 30 species.

The broad scope of their survey, which was accomplished in just 17 days, did not allow them the luxury of documenting small areas of diversity.  We were fortunate enough to spend most of a day in just part of the 1km square, where close attention to loch-sides, crags, scree and tiny patches of base-enriched flush and grassland enabled us to triple their plant list.

However, it has to be admitted that faunal diversity was not great so late in the season.  Apart from the animal life already mentioned, we also came across and identified the nest-web of an orb-web spider Larinioides cornutus, an emperor moth cocoon, the almost ubiquitous larvae of fox moth, the larval cocoons of the micro-moth Coleophora cf. alticollella on heath rush, an old hooded crow nest in the lochside rowan, and, of course, plenty of signs of red deer.

 

Ian M. Evans and Gwen Richards

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