On the south-facing slopes of Torr Mor, at the western end of Drumbeg (NC117329), there is a small area of woodland (satellite photo 1). It is particularly striking during a couple of weeks in the spring, when the many oak trees it contains are in fresh young leaf (photo 2). I must have driven past this woodland many hundreds of times, but had never taken a closer look at it until 16th May.
Parking up near the Viewpoint, I dropped down past the small house at Torr Beag, and then climbed up a sheep track into the eastern edge of the wood (photo 3).
Lichens
The multiple trunks of the first oak I encountered were relatively small (photo 4), with younger smooth bark covered with lichens (photo 5), later identified by lichenologist Brian Coppins as Lecidella elaeochroma (lower, black on pale green) and Pertusaria leioplaca (upper, creamy with warty apothecia). The former is widespread on smooth-barked trees, the latter more western in its distribution.
Other rougher-barked branches bore lichens such as the plum-fruited felt lichen Pectenia plumbea (photo 6), which is even more westerly in its distribution and a good indicator of Scotland’s Atlantic Rainforest.
Naming the oaks
Moving further into the woodland, I was able to take a closer look at the foliage of the oaks. When the leaves emerge, they are bronzy (photo 7), but turn green as they expand amongst the male catkins (photo 8). I collected a small sample of more mature leaves (photo 9) to examine later, since Assynt oaks are tricky to name.
As expected, they showed a mixture of characters, including the presence of auricles (little ears) at the base of the leaves and short stalks, together with a fuzz of tiny stellate (star-like) hairs along the midribs and veins.
This placed them firmly in the camp of the hybrid between pedunculate and sessile oaks, Quercus x rosacea, as is the case with nearly all of the local oaks we have checked. These hybrids may well be ancient in origin, possibly dating back to the post-glacial period, about 6000 years ago, when oaks invaded Sutherland from the south.
Individual oaks making up the canopy were often multi-stemmed and some of considerable age (photo 10).
Ground flora
Most of the shadier areas of the woodland floor are dominated by mosses and liverworts (photo 11), plants less attractive to grazers like sheep and the numerous red deer seen around Drumbeg. There were occasional clumps of primroses (photo 12), and a scatter of other woodland herbs such as wood sorrel and common dog-violet, but the sward was somewhat lacking in diversity.
On the edge of the woodland there were, however, a few oak seedlings (photo 13), providing potential for regeneration, if they escape grazing.
An isolated oak
Having climbed over a tumbledown wall along the top of the woodland, I found myself in a small enclosure containing a ruin and a single old oak (photo 14). A closer look at this tree revealed an impressive growth of tree lungwort Lobaria pulmonaria on an upright stem (photo 15).
A horizontal stem bore its less common yellow-grey relative Lobarina scrobiculata (photo 16), together with a good variety of other lichens. The relative abundance of these lichens was a reminder that the photobiont in their symbiotic partnership requires light to photosynthesise, so growth is often at its most luxuriant on the sun-lit side of trees.
Into the wood again
Having had a good look at this tree, I made my way back into the upper edge of the wood, where rock outcrops were themselves smothered in places with both of the lungworts and many other lichens (photos 17-18). This precise area falls in a gap between the two local 1:50,000 scale geological maps issued by the British Geological Survey. However, another smaller-scale map suggests that the conspicuous mineral-rich mafic dyke which transects Drumbeg village is almost certainly exposed at this point, hence the variety of lichens.
Circling back
The steeply-sloping rocky landscape was getting quite challenging at this point, so I took a last look over the canopy to Loch Drumbeg beyond (photo 19). I then returned to the car round the back of Torr Mor, through more extensive woodland on its seaward side, and then following an old track, noting a scatter of more, isolated, oak trees on the way (photo 20).
I have since learned that most of the woodland clothing the south-facing slopes of Torr Mor is on the in-bye land of a crofter born and bred in Drumbeg. Since it is one of best examples of native oak woodland in Assynt, I have obtained her permission to collect a more comprehensive sample of the lichens present, to send off to Brian Coppins.
Follow-up
With some time to spare on 25th May, I took a quick look at the westernmost part of this woodland (NC116329; photo 21), which runs up the march fence with Culkein Drumbeg, above the cattle grid (photo 22). It contains the same mix of trees, mainly downy birch, with scattered hazels, rowans and several large oaks, but being close to the road and bounded by fences, has a richer ground flora, with some thirty species noted, including pignut, bluebell, honeysuckle and greater stitchwort.
I also found a small aspen seedling. This was intriguing because, although there are two magnificent aspens further to the east, just above the road, this seedling must be the progeny of separate male and female trees, and flowering male trees are a very rare sight in Assynt.
Ian M. Evans
Photos by author unless otherwise indicated