A walk up the Unapool Burn, Quinag

July 4th 2020

A walk up the Unapool Burn, Quinag

Assynt’s moorland can look a bit dour early in the year, since its constituent vegetation takes time to green up (see, for contrast, the last photo, taken in June).   However this is a good time to appreciate the bones of the landscape, as we found on a walk up the Unapool Burn, below Sail Gharbh (NC2330/2329), on 2nd May.

We parked near the old bridge (built c.1830 as part of the Sutherland Estate’s grand plan to link up the north-west by road), and took the left bank of the winding Burn, in which deep pools alternate with gravel riffles (photo 1).  The erosive power of the Burn had exposed a 3m high section of the bank at the edge of one such pool, in which dense peat was sitting on a thick bed of silt (photo 2).

At the junction of the two there was a narrow band of fragments of trees, perhaps birch.  These presumably dated back to the brief climatic optimum about 4500 years ago, when woodland flourished across the local landscape, albeit only for about 500 years.  But what accident of topography had caused the deposition of such a substantial bed of silt, and were the trees rooted in it, or just washed-up on its surface?

Onwards and upwards

We continued along the left bank to the point where the exit burn from Loch nan Eun (loch of the bird/s) joins the Unapool Burn proper.  We followed this tributary up to a gneiss outcrop, where shelter from a cool northerly breeze provided a suitable spot for lunch, eaten whilst we were serenaded by a distant common snipe and meadow pipits.

A short walk afterwards took us to a shallow bay at the eastern end of Loch nan Eun (photo 3).  The aquatic vegetation was beginning to show signs of life, with buds on the bogbean Menyanthes trifoliata and bright-green mats of floating club-rush Eleogiton fluitans amongst the dominant straw-coloured debris of last year’s bottle sedge Carex rostrata.  The leathery leaves of bearberry Arctostaphylos uva-ursi began to appear on the heather-covered banks, a good sign, since it is very intolerant of burning.   We also heard the alarm call of a greenshank.

Leaving the main body of the loch, we made our way uphill, past pockets of very high heather Calluna vulgaris (another good sign), to the edge of the plateau of reddish-brown Torridonian rocks which occupy higher parts of this landscape up to and including the towering crags of Sail Gharbh.

In places very large blocks of fissured sandstone had broken off from the edge of the plateau, presumably during the Ice Age, and come to rest at crazy angles (photo 4).  These often coarse-grained rocks are from the lowest strata in the local Torridonian sequence, the Diabaig Formation, which includes conglomerates and basal breccias.

Their highest edges were ornamented with some striking bright yellow lichens, possibly where perching birds had provided extra nitrogen (photo 5).  Lichens are notoriously difficult to identify from photographs, but the aptly-named Lecanora sulphurea is possible candidate.

Boggy ground

For the next half a kilometre we were plodging across a flattish, very wet landscape, past numerous shallow bog pools, some of which had been part of Gwen’s Quinag Loch Survey back in the summer of 2010.  They are not productive of much wildlife interest so early in the year (nor were they then, as it happened), apart from very colourful piles of droppings left by red grouse (photo 6).  The black parts, incidentally, are the contents of that part of their gut known as the caecum.  Other visual interest was provided by the reflections in the bog pools of last year’s stems of common cottongrass Eriophorum angustifolium (photo 7).

We were quite thankful to reach the upper course of the Unapool Burn, near to a point where a large chunk of reddish wood, so-called ‘bog pine’, was sticking out of the eroded peat (photos 8-9).  This was another reminder of the climatic optimum, about 4500 years ago, when Scots pine Pinus sylvestris last occurred as a native species in this landscape, if only for a few hundred years.

The course of the Burn provided some diversity of animal life, with a frog, small brown trout leaping in pools, a wrenin high heather and even a fleeting glimpse of a fast-flying small tortoiseshell.  Botanical interest continued to be slight, apart from the bright pink flowering rosettes of lousewort (photo 10).

We had a cup of tea in full sun where the Allt Chranaidh, which drains Lochan Gainmhich at the foot of Glas Bheinn, joins the Unapool Burn (photo 11), and then made our way back to the bridge (photo 12, taken 18th June, of a greener landscape).  We had enjoyed our four hour walk, since there was quite a bit to look at, despite initial misgivings about the weather.

 

Ian M. Evans and Gwen Richards

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