When I went out to Strathfarrar on 27th August it had been about 10 months since my last visit to the glen. Such a long gap between trips to this beautiful area of old Caledonian Forest is quite unusual for me, but that’s because I’ve been concentrating my photographic trips recently on Glen Affric. I’ve also been to Chile a couple of times in the intervening period, so the months had slipped by and I was quite overdue for a return to what is one of my favourite places in the Highlands. It was therefore with considerable anticipation of having an interesting day that I headed there on one of the last days of August, hoping to catch the end of summer in the glen.
When I arrived there, however, I was struck immediately by the clear signs of the imminent approach of autumn visible all around. The leaves on some of the deciduous trees, such as rowan (Sorbus aucuparia) and silver and downy birch (Betula pendula and Betula pubescens respectively) had already begun to change colour, and a few bright yellow leaves of the latter had fallen on to the fronds of some bracken (Pteridium aquilinum) at the edge of the road.
This seemed very early for the trees to be losing their leaves, and I suspect it is a result of the hot and mostly dry summer that the Highlands have experienced this year. I’ve noticed in the past that trees, especially rowans, that are growing in dry or rocky sites tend to have an earlier colour change to their leaves, due to a lack of moisture in the soil, and I think that tendency has been exacerbated by the exceptionally hot weather we had in July in particular this year.
However, August was a more normal month in terms of temperatures and rainfall, and some recent wet days must have encouraged fungi to appear, as there were plenty of them visible this day in Strathfarrar.
I hadn’t gone far into the glen at all when I came across large numbers of fungal fruiting bodies on some fallen birch trunks near the road. I recognised these from their scaly caps and dense clustering as being honey fungi (Armillaria sp.). There are several closely related species within this genus, but it is difficult for a non-expert such as myself to tell them apart. I contacted Liz Holden, a mycologist who helps me with fungal identifications, and she named the species as Armillaria cf borealis.
Honey fungi are parasitic on broadleaved trees and also saprobic, meaning that they feed on dead wood. Some species are more parasitic in their ecological function, while others seem to be only weakly parasitic and instead derive most of their nutrition from breaking down the cellulose and lignin of dead trees. By doing so, they fulfil a vital role in the process of decomposition and decay, through which the nutrients stored in the wood of a tree are recycled and transformed for use by other organisms in the forest ecosystem.
There was an alder tree (Alnus glutinosa) growing right next to the birch log, and I took a break from photographing the fungi to look at it. Almost immediately I spotted a bright green metallic beetle on one of the leaves. This was a leaf beetle (Chrysomela aenea), which I wrote about in my recent blog, ‘Life on a young alder tree‘. That described finding it in Glen Affric, but I had first encountered this species in Strathfarrar in 2015, so it was good to come across it again there now.
On the other side of the road, another fungus caught my eye. This was a solitary mushroom, with a yellowish-orange cap, which had the unmistakable signs on it of having been grazed by a slug, most likely the European black slug (Arion ater).
This fungus looked familiar to me, as I’ve seen it before in the forest, and I thought it was a member of the Russula genus, but I didn’t know which species it was. When I sent the specimen to Liz, she identified it as the yellow swamp brittlegill fungus (Russula claroflava). The cap of the fungus displayed a visual record of the movement of the slug across it, as its grazing had left a meandering path where the surface layer of the fungus had been eaten, revealing the whiter section underneath. In a couple of places the white layer and the gills had also been consumed, leaving holes right through the cap.
Slugs in the Caledonian Forest are omnivorous, with a varied diet that includes carrion, fungi, earthworms, leaves, stems, dead plant material and dung. The black slug in particular seems to relish fungi in the autumn, as I have often come across it feeding on mushrooms. However, its tastes must favour some fungi more than others, with fungi in the Bolete group often being targeted, whilst species such as the chanterelle (Cantharellus cibarius) are almost never touched. That’s just fine by me, as I collect chanterelles from the forest to eat every year, and I’m glad I don’t have to check them to see if they’ve been partially eaten and are covered with slime trails from slugs. Another feature of chanterelles is that they are seldom infested with maggots, unlike the Boletes, and this adds to their attractiveness for fungal foragers such as me. Before leaving this area I returned to the log with the honey fungi, and found a fruiting body inside a hole in the wood – I couldn’t resist taking a photograph of it.
Driving further into the glen, I stopped at another section of the birch woodland, where I’d seen some more fungi beside the road as I passed by. Parking in one of the passing places on the single track road, I walked back towards where the fungi were. On the way, my attention was drawn by a small reddish-brown shape on a frond of bracken (Pteridium aquilinum). Looking closer, I recognised it as a shieldbug, and although I didn’t definitively identify it at the time, I suspected it was the birch shieldbug (Elasmostethus interstinctus).
The bracken frond it was on was directly underneath the branches of a large birch tree, which tended to confirm my suspicions about its identity. Looking around, I soon spotted another of the same shieldbugs on a different bracken frond, on the other side of the tree. Shieldbugs are a visually interesting groups of insects, with distinctive angular shapes, stippled surfaces on their scutellums (as the cover of their wings is known as) and coloration that is often bright, as in this species.
Back at home later on, I was able to confirm that it was indeed the birch shieldbug by looking on the Internet at the British Bugs website, which includes an excellent chart illustrating all the life cycle stages for many of the British shieldbugs. While I was still in the forest though, I saw another invertebrate on the same bracken frond as one of the shieldbugs. This was the alder spittlebug or froghopper (Aphrophora alni) which can be difficult to tell apart from the common froghopper (Philaenus spumarius). The latter is best known for the blobs of white foam or ‘cuckoo spit’ that it produces on vegetation in early summer for its nymphs to develop inside.
Turning to the other side of the road, I spent a couple of minutes appreciating a perfectly formed fly agaric fungus (Amanita muscaria), which had caught my eye from the car as I had passed by.
I’m fascinated by things like the pattern of white spots on the cap of this fungus. These are the remains of the veil that covers the mushroom when it first emerges from the soil. As the cap expands and opens outwards, the veil breaks apart and becomes spread out, forming these rather wart-like spots. In some cases the spots disappear entirely by being washed off by the rain, while in others they persist until the mushroom decomposes and rots away. The exact pattern of spots is different on every fly agaric, giving each fruiting body a unique and individual appearance. The fungus grows in mycorrhizal association with birch trees, and is one of the commonest mushrooms in the Caledonian Forest in late summer and early autumn. 2018 seems to be a particularly abundant year for them, as I’m finding lots of them every time I’m out in the forest at the moment.
I walked along the road for a little bit, looking for some more fungi that I’d seen when I had passed by in the car. There was a gorse bush (Ulex europaeus) right beside the road, and I noticed another shieldbug on it. I recognised this one as being the red-legged shieldbug (Pentatoma rufipes), but it was dead – I couldn’t see what could have caused that. I wasn’t very happy to encounter the gorse, because it’s not a part of the Caledonian Forest ecosystem. Although it’s native to Scotland, its natural habitat is mainly in coastal areas, where its deep tap root helps to stabilise sandy soils. It only occurs in glens such as Strathfarrar and Affric in areas of gravel or grit along the edge of tracks and roads – typically its seeds have been brought in with that material when roads or tracks are constructed or upgraded. As a result it forms an unnatural linear strip of vegetation along the edge of the roads and tracks – in Glen Affric Trees for Life has been working for many years to remove it from those roadside verges.
After a few metres I came across a group of different fungi that I’d seen previously, and I really had the sense from their abundance that autumn was fast approaching. It’s at the end of summer, when the temperature starts to drop and rainfall increases that many fungi begin to fruit, with their mushrooms appearing in the forest, often in considerable profusion. The first fungus I came to there was one of the ‘scaber stalk’ fungi, which are so-called because of the scabers, or small projections, that protrude from their stalks and give their stems a distinctive appearance. They are in the genus Leccinum, which is part of the bolete group of fungi, all of which have tubes or pores on the undersides of their caps, instead of the gills that are more commonly found on mushrooms. It can be difficult to tell the individual species of Leccinum apart from each other though, and I had to turn to Liz Holden again to get this one identified as being the mottled bolete fungus (Leccinum variicolor).
Very close by was another member of the bolete group, this time in the genus Boletus itself. It was the penny bun or cep (Boletus edulis), another common species, which as its scientific name indicates, is edible. It is highly prized by mushroom hunters for its culinary flavour, but it has to be harvested when it is young, for it very quickly gets infested with the white larvae or maggots of fungus gnats. I collected this specimen and took it home, but didn’t eat it, as larvae began emerging from the pores, making it rather undesirable for me as a vegan!
Also nearby were some other scaber stalk mushrooms, which Liz identified for me as Leccinum cf cyaneobasileucum – a species which doesn’t yet have a common English name. There were two of them together, and one had been partially eaten by a slug, like the brittlegill fungus I’d seen earlier.
From there I moved on further west in the glen, to where the birch-dominated woodland is replaced by Scots pines (Pinus sylvestris). In some places there are just a few scattered old pines, and with some dark rain clouds appearing in the otherwise blue sky, these created some dramatic landscape views . The last of the heather (Calluna vulgaris) was still in blossom, and its purple colour contrasted with the pale green of the bog myrtle (Myrica gale) it was growing amongst.
Some of the bracken was just beginning to change colour here, making this the brief time of the year when the yellow hues of the dying fronds complements the purple of the heather. For me this is a very pleasing, although ephemeral, combination of colours, especially when there’s also some blue sky visible. Before moving on any further, I had a quick look at the trunk of one of the pines, as I’m fascinated by the patterns that the different layers of the bark make, together with the scattering of lichens growing on the trunk.
As I entered into a denser stand of Scots pines, my attention was drawn to some bright red colour at the base of an old birch tree. It was a patch of blaeberries (Vaccinium myrtillus) with the leaves already in full autumnal colour display, growing beside some heather that was still in flower. Together these created another beautiful combination of natural colours, one which I often think of as forming the ‘wild garden’ of the Caledonian Forest. 2018 is a good year for the berries on the blaeberry plants, and I was savouring a few of them as I walked around, making the wild garden analogy particularly appropriate on this day.
Blaeberry patches vary in terms of the colour their leaves change to in the autumn. In some cases the leaves go yellow, but others turn bright red, like this one here. I wonder if the variation is due to different minerals in the soil that are taken up by the plants?
As I walked around amongst the Scots pines, there were signs of the early arrival of autumn everywhere. Particularly noticeable were the bright red colours of the leaves on some young rowan seedlings, in amongst the heather and blaeberries. The intensity of the colours, especially the red, seemed stronger than in many other years, and I suspect that may be due to the relatively hot summer we’ve had in 2018.
Only some of the blaeberry plants had leaves with autumnal colours – others were still green. However, where they had changed already, the rich tapestry of bright hues was breathtaking under the canopy of the old pines.
Red is particularly prominent as a colour in the Caledonian Forest at this time of the year. From the berries and leaves of the rowan, to the fly agaric fungus and the autumnal leaves of the blaeberry plants and the berries of the closely-related cowberry (Vaccinium vitis-idaea), these scarlet and crimson hues bring the forest alive in a magical and colourful way.
I was following a path through the forest that leads uphill on the south side of the glen, and there’s a special old oak tree (Quercus petraea) along the way. It’s a tree that has had a unique life history, as its main trunk was blown down at some point and is now lying supine on the ground, covered in moss and relatively inconspicuous at first glance. However, it’s still alive, and after that event, a new trunk has grown upwards at right angles to the fallen section, and forms the main body of the tree today.
I always spend a little while with this tree when I pass it, but today it would be my final destination, as it was getting late and I needed to begin the return journey home. Also, the midges (Culicoides impunctatus), which had been getting more prevalent as the day wore on, were now quite bad, so I couldn’t linger for long! I had a quick look to see if there was anything of interest on the leaves, and almost immediately I came across a small green leafhopper.
Thanks to the expertise of Joe Botting, one of the creators of the British Bugs website that I mentioned earlier in this blog, I was able to get it identified as being Eurhadina pulchella, which is widespread and common on oaks in Britain. Then, on the underside of another leaf I spotted a winged aphid (Tuberculatus annulatus). Like the leafhopper, this is a common species on oaks, and indeed its English name is the common oak aphid. Unlike some species of aphid, it doesn’t form dense aggregations, but is usually seen as a few scattered individuals on an oak leaf.
I had a look under some other leaves to see if there were any more aphids, without success, but I did discover a tiny black wasp on one leaf. It seemed to be exploring the leaf and investigating what looked like stunted galls on its surface. When I contacted Margaret Redfern, an expert on plant galls, about this she replied that the galls looked like young common spangle galls that are induced by a wasp (Neuroterus quercusbaccarum), but in this case had failed to develop properly, probably due to the very dry summer this year. She also thought that the wasp itself looked like a female of this gall-inducing species (Neuroterus quercusbaccarum), but I’ve not yet been able to find anyone who can examine the specimen and confirm this identification.
That was my final photograph of the day, as I had to make a rapid retreat to avoid being bitten excessively by the hordes of midges that had accumulated around me, during the minutes I’d been looking at the oak. It had been another memorable day though out in the Caledonian Forest, one in which I felt that I had been there right on the transition between summer and autumn. As a result of that, one of the photos I’d taken, of the blaeberries in their red autumnal colour under the old pines (which features earlier in this blog), has made its way on to the cover of the Caledonian Forest Engagement Diary for 2019 that I’ve produced for my family and some friends.
Featuring 58 colour photographs of the forest from sites such as Strathfarrar, Glen Affric and Dundreggan in Glenmoriston, this is a successor to the Trees for Life Engagement Diary that I published for almost 30 years, beginning with the 1989 edition. I’ve had some additional copies of this diary printed, so if anyone who is missing the annual Trees for Life Diary would like to purchase one, please contact me at firstname.lastname@example.org for details. The price is £16, plus £2.50 for post and packing (ie £18.50 altogether).