A day in Glasdrum Wood, part 1

For quite a few years I’d been wanting to visit Glasdrum Wood, a special area of temperate rainforest that is protected as a National Nature Reserve (NNR) on the west coast of Scotland, and at the end of July I finally made a visit there. Situated about midway between Fort William and Oban, on the north shore of Loch Creran, the wood is about 3 hours by car from my home so I set off at 6 am to ensure I had enough time to explore the woodland.

Over the years I’ve spent time in quite a few of the relic temperate rainforests on the west coast, and I was excited to visit what was a new site for me, and one that is protected for its special features.

 

 

 

 

 

 

 

The NNR covers 169 hectares, and woodland is the predominant vegetation in most of the lower elevation sections of it (above 300 metres, the tree cover gives way to mire and heath), so I planned to spend the day in the forest.

 

 

 

 

 

 

Reaching the site just after 9 am, I began walking around the visitor footpath that leads through a part of the woodland, and as it turned out, it took me all day to complete its relatively short length of just over 1 km. As usual, I began to find many subjects of interest along the way, and within 50 metres of leaving the car park, I came across the moss-covered oak trees (Quercus petraea) shown here, which provided some classic imagery of the green wonderland that is a temperate rainforest.

The day was overcast and it looked like there had been some rain in the previous 24 hours, so conditions were ideal for appreciating (and photographing) the richness of the plants, trees and fungi in the forest.

 

 

 

 

 

 

In damp conditions like this, the lichens and mosses are fully hydrated, and are at their vibrant best, radiating the fullness of life. By contrast, on dry sunny days, they are shrivelled in size and paler in colour, appearing limp and ‘in retreat’ from the desiccating conditions. Thus, the best time to visit a temperate rainforest is just after the rain, and in relatively bright overcast conditions like this, when the soft, muted light provides an even illumination that reveals all the details and textures of the vegetation.

As I walked around, I began to notice all sorts of interesting features – for instance, some fungi growing on a fallen dead branch of one of the oak trees and, nearby, an intricately-shaped mine in the leaf of a honeysuckle plant (Lonicera periclymenum). I’d not seen this particular mine before, but when I consulted the excellent British leaf miners website later on, I was able to confirm it as being caused by the larva of a fly (Chromatomyia aprilina).

The honeysuckle was growing near a holly tree (Ilex aquifolium), and while I was looking at that I noticed some small green shapes on the underside of some of the leaves. I wasn’t sure what these were, but I took a number of photographs of them, and later sent those to Joe Botting, a specialist in Hemiptera who helps me with identifications. He replied that rather then being a true bug or other hemipteran, they were instead juvenile forms of barkflies, or psocids, which are in a different insect order – the Pscoptera – and are also known as book lice or bark lice. He said that because they hadn’t developed any distinguishing features yet it would be impossible to say what species they were.

On another piece of fallen oak branch nearby, I saw something which I did recognise – the hairy curtain crust fungus (Stereum hirsutum). This is a distinctive bracket fungus that grows on dead wood, and gets its common name from the hair-like structure of its upper surface and the curtain-like pattern of the edge of its brackets. This is quite a common saprotrophic fungus, meaning that it  breaks down dead wood, recycling the nutrients in it so that they become available other organisms in the forest.

I’ve seen this fungus quite often, and wrote a blog especially about it last year. In that instance it was growing on the dead branch of a downy birch (Betula pubescens) at Dundreggan, and it was being parasitised by another fungus – the leafy brain fungus (Tremella foliacea). There was no sign of this parasitic fungus with the hairy curtain crust fungi at Glasdrum though, but I enjoyed looking at its convoluted shapes and the hairy upper surface of the brackets. I wondered what the evolutionary advantage of the hairiness is? There was no immediately obvious answer that sprang to my mind, so it will have to remain as another of Nature’s mysteries, at least for the time being.

Moving further into the forest, I began to notice some hazel trees (Corylus avellana) amongst the oaks. I was particularly interested in these, because in the temperate rainforests of Scotland’s west coast they provide the habitat for a special group of lichens called the Lobarion community. These lichens take their name from the genus of the best known species, tree lungwort (Lobaria pulmonaria), and include several rare species, so I was keen to see what was on these hazels. While there were some small clumps of tree lungwort visible, my attention was taken by a much larger patch of a closely-related species, green satin lichen (Lobaria virens). I’ve seen this species previously in abundance in Tomie’s Wood in Killarney National Park in the Republic of Ireland, where there is an excellent example of oak-dominated temperate rainforest, and we’ve also got a small example of it at Dundreggan, on a hazel tree in the gorge of the upper Allt Ruadh, or Red Burn.

It’s quite an easy lichen to identify and can be distinguished from tree lungwort by its smoother thallus (as the main part of a lichen is known) and the greater abundance of apothecia – the brown discs that release the spores of the fungal partner in the symbiotic organism that is the lichen.

 

 

 

 

 

 

On one of the hazel trees I saw another foliose or leafy lichen growing beside some of the green satin lichen, and I had to send a photo of it to John Douglass, a lichenologist who helps me with identifications, to find out what species it was. He replied that it was a species called Sticta sylvatica, which is another lichen in the Lobarion community. Like the lungworts (Lobaria spp.), the Sticta  lichens consist of a three way symbiosis, with a cyanobacterium occurring in addition to the fungus and alga which comprise all lichens.

Glasdrum Wood is growing on rocks which are mostly black slates and phyllites, but there are some sections of it where there are outcrops of limestone, and on these ash trees (Fraxinus excelsior) replace oak as the dominant canopy tree. Walking further up the trail, I reached a particularly fine, large ash tree, so I chose that as the spot to have my lunch. There was a bench conveniently placed on the path nearby, so I’m sure that many other people had enjoyed a bite to eat there before me!

 

 

 

 

 

 

 

 

 

In recent years there has been a lot of concern about the future of ash trees, because of a disease called Chalara, which has devastated the ash trees of Denmark, but I was pleased to see that this ash looked in perfect health.

After lunch I continued my exploration of the wood, and that features in part 2 of this blog, which also includes some video footage from the day.