During the first half of May I made a couple of trips out to Glen Strathfarrar, which contains one of my favourite remnants of the original Caledonian Forest. There’s extensive areas of old Scots pines (Pinus sylvestris) that are relatively little-visited by people, and the glen also contains a good number of aspen trees (Populus tremula), as well as some less common species such as oak (Quercus petraea) and juniper (Juniperus communis). The glen has a locked gate across the road into it, and only 25 cars are allowed in at any one time, so it’s always a quiet place to go and spend a day in the forest.
On the first of these trips the leaves of the deciduous trees were still relatively newly-opened, and were a vivid bright green colour. That fresh green only lasts for a couple of weeks or so though, as the leaves turn a deeper shade of green once they are completely unfurled and maximising the amount of energy they can photosynthesise from the sun. This period, between leaf burst and the darkening of the new leaves, is a very special part of the year, and one in which I like to spend as much time as possible out in the forest. This was one of the reasons for these two trips to Strathfarrar, whilst another was to experience as much of the newly-emerging life as possible.
On this particular day I’d arranged to go out with Dan Puplett, a former colleague at Trees for Life who now works freelance, leading various nature-based activities such as looking for animal tracks and signs. We’d been discussing having a day in the forest together for some months, and it was great to finally have a chance to catch up with each other, and to share some time in the pinewoods in Strathfarrar. Once we were past the locked gate, we took our time going up the glen, stopping at various points along the roadside where I knew there might be some features of interest to us.
The first place we stopped at was a place where there are a few old Scots pines beside the River Farrar, as well as a large aspen tree and a couple of nests of wood ants (Formica aquilonia). I was interested to see if there was much activity on the ant nests, but before looking at them I found some other interesting subjects – a cluster of dog violets (Viola riviniana) on a gravel bar beside the river, and, on a piece of dead wood, some tiny white fungi which I recognised as being a species called snowy disco (Lachnum virgineum).
I’ve seen these fungi in Strathfarrar before and featured a couple of photos of them in a blog I wrote in 2011. Despite being difficult to see they are quite beautiful and I find them very photogenic – they are a good example of the beauty in miniature in Nature.
On a previous visit to this part of Strathfarrar I’d noticed some disturbed ground in this area, and it was still visible on this day. Dan said it was the work of a badger (Meles meles) which had been rooting in the ground. He went off to have a look around to see if he could find any signs of a badger sett nearby, while I spent some time looking at the wood ants on one of the nests there. As it was quite a warm day, the ants were very active, with large numbers of them moving back and forth rapidly on their nest. When I get a chance I like to observe wood ants closely, as there’s often interesting behaviour to be seen.
Almost immediately I noticed that a number of ants were moving small whitish shapes on the surface of the nest, and when I looked more closely I realised these were small pieces of pine resin. This was exciting for me to see, as scientific research has revealed that wood ants deliberately harvest pine resin like this and use it for its anti-bacterial and anti-fungal properties to help keep their nests free from the diseases such organisms could cause for them. Details of the research, carried out by a team of scientists on a closely-related wood ant species (Formica paralugubris) in Switzerland, can be seen here. I watched the ants for quite a while, as some of the workers struggled to manouevre the pieces of resin over the miniature obstacle course that was the surface of their nest. Sometimes one ant would transport a piece of resin by itself, while in other instances two or more ants would cooperate on moving the resin. I saw that they were indeed taking the resin inside the nest, down through some of the many small holes that provide access to the interior from the surface. I also shot some video footage to document this behaviour, and here’s a brief compilation of that:
The ants were not just busy on their nest though, as the workers range over quite a large area, searching for food and other organic material that they drag back to the nest. There was quite a large aspen tree a few metres away from this nest, and when I looked at the trunk I saw ants both climbing and descending it. I was intrigued by this, as I wondered what the ants were looking for higher up in the tree. Possibly there were some aphids on some of the branches, although I was slightly doubtful about that, as the aspen didn’t have any leaves yet. It is always the last tree species to gain its new leaves in the spring, with it sometimes being early June when the leaves appear.
Wood ants tend a species of aphid (Pterocomma tremulae) that feed on aspen trees, sucking the sap from the twigs and excreting a clear liquid called honeydew, which is what the ants feed on. Although this aspen didn’t have any leaves yet, the sap would probably already have been rising, thereby enabling the aphids to feed and attract the ants. However, this is just speculation on my part, as it was a tall aspen tree, and there was no way I could see if there were any aphids high on the tree’s twigs or not!
Down beside the river, on the gravel bar where the dog violets were flowering, my attention was caught by some vivid looking examples of great wood-rush (Luzula sylvatica). I was slightly surprised to see them there, as I usually come across them in damp, shady spots within the forest, but here they were in quite an open situation. This species keeps its leaves, which are green and glossy, through the winter, but these plants had what looked like new leaves on them as well – they were an orangish brown colour.
Because of both the shiny-ness of its leaves, and the fact that they grow upwards sheathing each other to form a hollow cylinder, great wood-rush always reminds me of the bromeliads that grow in the tropical rainforests of the Americas. Somehow it seems like a slightly exotic plant for Scotland!
After spending quite a bit of time in this area, we moved west, further into the glen. I suggested crossing the river at a certain point where I knew there was a ford, to visit a part of the glen I hadn’t been to for about 30 years, and Dan readily agreed, as he’d never been to that area himself.
The water level in the river seemed relatively low, and there was a line of stones marking the route of the ford, so we were able to cross it uneventfully. I had brought a pair of wellington boots with me specially for this, changing into them for the crossing and then putting my regular hiking boots back on once we were on the other side. Dan prefers to wear special tall rubber boots when he’s out in the forest anyway, so he didn’t need to change his footwear at all.
Almost as soon as we had crossed the river we found something of interest, when Dan spotted a badger paw print just a few metres from the water’s edge. It was next to a hole and the imprint of the badger’s claws was clearly visible in the soft earth. Dan does a lot of animal tracking as part of his own work, so he recognised it immediately, and pulled out a tiny ruler, to both measure the size of the print and to act as a visual indicator of the size in photos. It was great for me to see a confirmed badger print, as that will enable me to identify them myself in future, such as in the area where I’d found the snowy disco fungus earlier in the day. It’s also an indication of what I like about going out into nature with someone like Dan – we can both learn from each other. While I couldn’t have identified a badger print previously, Dan didn’t know about the snowy disco fungus, so we were able to share our respective sets of knowledge, to the benefit of us both.
We only walked another few metres from the site of the badger paw print when my attention was taken by a series of low mounds distributed across a flat and relatively open section of land.
It took me just a few moments to recognise what I was seeing – the nests of yellow meadow ants (Lasius flavus).
We have some of those ants on our land at Dundreggan, and I know of several nests there, but I’d only ever seen one or two nests in close proximity before. Here, however, there were literally dozens of nests spread across the flat open landscape, and the scene reminded me more of the termite mounds that occur in the Kimberley region of northwestern Australia, or those in the cerrado region of central Brazil, than of a typical Scottish landscape! It was certainly a distinctive feature in the glen, and Dan and I spent a while wandering amongst the mounds, many of which were covered by closely-cropped heather (Calluna vulgaris).
I assume that the ants must somehow be restricting the growth of the heather on the mounds – I’ll need to do some research to find out what the mechanism for that is. Unlike the nests of wood ants, there are rarely if ever any yellow meadow ants visible on the outside of their nests. Instead, they seem quite still and innocuous from the outside, revealing nothing of all the activity goes on underneath the surface. To see the ants at all, it’s usually necessary to disturb the surface a little, and I did this on one of the nests, so that Dan could have sight of the ants.
These ants are much smaller than the wood ants (Formica aquilonia) that we’d seen earlier, with the workers reaching a maximum length of just 4 mm, compared to the 10 mm size of the wood ants. Apparently they spend almost their entire time underground, and feed primarily on the honeydew excreted as a waste product by root aphids. Those are a group of aphids that suck the sap of plants at their root collars, where the roots meet the stem of the plant at the point where it emerges above the ground. The common name of this species is derived from the yellowish-orange colour of the ants, and they have very small eyes, as an adaption to their life in the darkness underground.
The disturbance I made on the surface of the nest didn’t survive for long. Almost immediately the ants emerged, scurrying around in frenetic activity to repair the damage. After a few minutes no more ants were visible, and when I returned to look at that nest 10 or 15 minutes later, the small hole I’d made had been filled in and was no longer visible. As I looked around this area with all the nest mounds, it was quite a realisation to acknowledge that this was a veritable ant city, with numerous ‘districts’ – the individual nests – scattered around the area.
Leaving the meadow area behind we walked on into the pinewood beyond. Like Glen Affric, most of the native pinewood area in Glen Strathfarrar is situated on the south side of the glen, on the north-facing slopes. Those tend to be wetter than the south-facing slopes, because of the lesser exposure to the sun there. One consequence of this is that the wetter conditions mean that the soils are generally poorer and more acidic, but are also less susceptible to burning, which may have removed many of the forests in Scotland in the past. This seems to have enabled the ones to survive there, and in similar fashion on the north facing slopes of neighbouring glens, such as Cannich, Affric and Glenmoriston. The south-facing slopes by contrast, being drier, have better soils and trees such as oak (Quercus petraea), hazel (Corylus avellana) and wych elm (Ulmus glabra) would have thrived there in the past. Indeed, there are still some scattered remnants of those species in Strathfarrar today, on the south-facing slopes in the eastern part of the glen.
We hadn’t walked very far into the pinewood area when we came across a rather unusual old downy birch tree (Betula pubescens) that had been snapped in two and blown down by a storm. The tree must have had an interesting life, as the fallen part of its trunk was covered in a number of large burls, clustered together in a way that I hadn’t seen before on any tree in Scotland. Burls (or burrs as they are also known) are usually the result of stress to a tree, and are formed by dormant buds causing abnormal growth. The size and number of them on this tree made me wonder what sort of stress it had experienced to produce so many …
Another feature of the tree was a number of black areas on the part of the trunk that was still standing, and I recognised these as being the sterile conks of the chaga fungus (Inonotus obliquus). They are sterile as they are not the fertile surfaces that release the spores of the fungus. They are irregular in shape and have an appearance similar to burnt charcoal, with a texture that is slightly crumbly. The fungus is parasitic on birch trees, in both Europe, northern Asia and North America, causing a white rot that weakens and eventually kills its host. When I noticed these conks, that explained why the tree had been snapped in two by the storm – the fungus had weakened the wood sufficiently for it to break in a high wind. We have a birch tree at Dundreggan similarly infected with the chaga fungus , and it too snapped in a storm a few years ago, right where the fungal conks were on the trunk. The chaga fungus has long been known to have healing properties, particularly in Russia and eastern Europe, and recent research has shown that it has potential beneficial effects as an anti-cancer agent. Whether the presence of the chaga fungus was related to the numerous burls on the tree is an open question …
At this point we’d come to the end of our time, as Dan needed to get home relatively early. The sun came out for our last few minutes in the old pinewood, adding to the brightness and vitality of the forest, with all the new leaves on the birches. The day had gone by really quickly, and as is often the case I hadn’t got to see as much of the forest as I’d hoped, especially on the south side of the river. However, it had been another very interesting and educational day, and one that left me wanting to return soon to Strathfarrar – that will be the subject of part 2 of this blog.