Wych elms in Assynt (3): Culag Bridge
This is the first of a series of portraits of local wych elms, a contribution by the Assynt Field Club to the Assynt Elm project. It focusses on other species associated with them.
Around the old Culag Bridge, at the south end of Lochinver (NC094221) there is a group of large elms (photo 1); they also extend a short way up the Culag River. Two of the trees on the west side are now inside the deer fence surrounding the Games Field.
Associated mosses and liverworts
We took a closer look at six of these trees on 18th October 2023 with bryologist Gordon Rothero, who listed the mosses and liverworts on their trunks (photo 2). Two mosses were almost ubiquitous, cushions of the darker green yoke-moss Zygodon viridissimus (photo 3) and sprawling shiny shoots of the silky wall feather-moss Homalothecium sericeum (photo 4).
In his account of Assynt bryophytes in the Flora of Assynt (2002), Gordon describes the first as ‘an uncommon moss occurring as both an epiphyte on the trunks of trees with nutrient-rich bark and on shaded rocks’, and the second as an ‘attractive moss…common on dry base-rich rocks’, which ‘also occurs on large elms and ash trees’.
He also recorded the mosses Brachythecium rutabulum (‘uncommon’), Hypnum andoi (‘reasonably frequent on the limbs and trunks of larger trees’) and Pterygonium gracile (interestingly, ‘almost exclusively on mildly basic rocks on the margins of lochs’), and the leafy liverwort Metzgeria furcata (‘a common feature as an epiphyte, particularly on hazel’). In all, a fairly predictable list of species indicative of the nutrient-rich bark which is a feature of mature wych elms.
Other features of interest
Whilst Gordon was at work on the bryophytes, we noted and photographed other features of interest on the six trees. Ian took more photographs of some of these on 23rd February 2024.
The two trees just in the Games Field (photo 5) are much larger than others around its margins and must pre-date them by many decades. Both are heavily burred, burrs being natural outgrowths covered in very rough bark and sprouting small twigs (northern tree, photo 6).
Wetter burrs on the southern tree have been colonised by the lobed green thalli of the largest British lichen, tree lungwort Lobaria pulmonaria (photo 7). Formerly much more widespread in the British Isles, its distribution was severely curtailed by air pollution and it is now restricted to western parts, particularly ancient woodlands with oceanic climates. It is widespread in suitable habitats in Assynt.
At the foot of the trunk of the southern tree, on the east side, we noted a large, pale-edged, perennial bracket fungus (photos 8-9). This has been identified by mycologist John Hedger as the giant elm bracket Rigidiporus ulmarius, a wood-rotting species not previously recorded from the Highlands.
North of the bridge
There are four more large wych elms on the eastern side of the river, north of the bridge, all bearing copious growths of either tree lungwort (photo 10), ivy, or both. The largest of these is the northernmost which, when we looked at it in October (photo 11), had at the foot of the trunk a striking clump of fruiting bodies of the shaggy scalycap Pholiota squarrosa (photo 12). This fungus is described as saprotrophic; it feeds on already dead wood and is not known to cause ‘tree failure’.
To finish on a positive note, on the February visit the dark flower buds on elm twigs high above the river were just beginning to expand (photo 13).
Ian M. Evans and Gwen Richards
Photos 9, 12 and 13 by Gwen Richards, the rest by Ian Evans