Allt a’Chalda Mor, Inchnadamph
Four major watercourses drain the eastern ramparts of Assynt, from Glas Bheinn south to Cnoc na Sroine, and of these the northernmost, Allt a’Chalda Mor, is perhaps least often visited. It rises on the south-western flanks of Beinn Uidhe (NC2625) and flows some 5km into Loch Assynt just north of Calda House (NC2423). The lowest reach cuts through Cambrian limestones in a magnificent wooded gorge.
The gorge
On 29th September 2021, Gordon Rothero was up on his usual autumn visit. There was bright sunshine, tempered by a cool wind, and we decided to explore a stretch of this river, from the A837 up to the junction with the Allt nam Breac (NC2423).
The river was running strongly, and noisily where it dropped over small falls, which made the going along the water’s edge quite challenging. Gordon tackled this, focussing on the bryophyte flora of the limestone exposed along its banks. Meanwhile, Gwen and Ian followed the southern edge of the gorge, recording higher plants and animal life.
The commonest trees along the gorge are downy birches (photo 1), with frequent rowans, scattered hazels, several fine wych elms (photo 2) and occasional grey willows and hollies.
The riverside yielded some 45 species of bryophytes, including the tiny leafy liverwort rock pouncewort Cololejeunia calcarea (photo 3), which is restricted to damp basic rocks. Gordon also had hart’s-tongue Asplenium scolopendrium, wall rue Asplenium ruta-muraria and brittle bladder-fern Cystopteris fragilis on shaded outcrops along the water’s edge, all typical of limestone. On the sides of the gorge (photo 4), we found the hanging heads of a rare tall grass hairy brome Bromopsis ramosa.
Half-way up the gorge, we were entertained by the sight of a cushion of foam, about the size of a car wheel, spinning busily in a shallow pool in the middle of the watercourse (photo 5). A video made by Gwen can be seen here on the Field Club’s YouTube Channel.
Out of the gorge
Gordon emerged when waterfalls made further progress along the river impossible (photo 6), and we then walked up the moorland on the south side. A large loop, above the wooded section of the gorge, gave us a vantage point for lunch (NC246236, photo 7). After lunch, Gordon explored an earthy slope on the upstream side of this loop, which provided his best finds of the day, two more small leafy liverworts. Scarce notchwort Leiocolea badensis has only once before been found in Assynt, by the doyen of liverwort studies Jean Paton, back in 1969. An even rarer flapwort, Jungermannia polaris, is a species of montane base-rich ground, not previously recorded below 450m and ‘new’ to the North-West.
We then continued up the winding course of the river to another loop with a vertical cliff bearing scattered trees (photo 8), out of reach of browsers, opposite which we found the leaves of globeflower Trollius europaeus.
Stony flushes and outcrops
After that we left the watercourse to explore some stony flushes, the first of which (NC247236) provided our only sighting that day of broad-leaved cottongrass Eriophorum latifolium. The second (NC249236) had some thin sprawling plants of a horsetail, which defied identification on the day and continued to do so back home, despite scrutiny under a low-power microscope. Samples have gone off to an expert in the Natural History Museum for his opinion.
Some oddly-shaped reddish-brown rocks on a near skyline (photo 9) next attracted our attention; the geological map later identified these as an isolated outcrop of iron-rich Fucoid Beds. On boulders derived from the outcrop, Gordon and Gwen each found two tiny fruiting bodies of the white-stalked puffball Tulostoma niveum (photo 10), a significant northerly extension of the known range in Assynt of this nationally rare fungus.
From these heights we made our way down a north-facing slope to the junction (photo 11) of the main river and its tributary, the Allt nam Breac (NC249237). We were able, with some care, to ford the main river and then worked our way up the winding tributary.
This added brooklime Veronica beccabunga and intermediate water-starwort Callitriche brutia ssp. hamulata to the higher plant list. Brooklime has rounded, rather shiny, leaves and an apparent liking for sites on the limestone. The water-starwort is a distinctive member of a ‘tricky’ genus, its narrow leaves having spanner-shaped ends; it shows, again, a preference for the eastern parts of the parish. Gordon continued to add bryophytes to his list until we left the survey area at a limestone outcrop on a slope west of the burn (NC247239).
Summary of finds
Four hours exploration yielded 76 mosses, 19 liverworts and 125 higher plants.
Insect life was scarce, but we noted adult meadow grasshoppers Chorthippus parallelus in two places, a birch shieldbug Elasmostethus interstinctus at the edge of the gorge (photo 12), a fox moth caterpillar, and a red admiral butterfly. We also found galls of the mite Aculus kochi on yellow saxifrage Saxifraga aizoides and of the sawfly Eupontania collactanea on creeping willow Salix repens. Birds were few, some meadow pipits, a dipper up and down the wooded stretch, single buzzard and kestrel overhead, and much higher, a skein of pink-footed geese. However, it was a very good day out for the time of year.
Ian M. Evans and Gwen Richards