A day in Glasdrum Wood, Part 2

This is the follow up to my previous blog, about my visit to Glasdrum Wood National Nature Reserve in Argyll at the end of July. Rather than make one very long blog, I decided to split it into two, in the interest of making it more readable, and also for my own ease of posting blogs relatively regularly. The amount of work involved in creating each blog is obviously proportional to the length of the blog, and my aim is to get two blogs posted each month, so dividing my day at Glasdrum between two has enabled me to keep to that schedule.

Anyway, continuing on after my lunch break at Glasdrum, I came to another group of oaks (Quercus petraea) and on one of those I found some common spangle galls on the underside of several leaves. These are induced by the sexual generation of a tiny wasp (Neuroterus quercusbaccarum), and I featured the currant galls produced by the agamic, or non-sexual, generation of this wasp in a recent blog from Glen Affric. These spangle galls were quite young and hadn’t reached their full size yet. They would do so by the end of the summer, and then the wasp larvae overwinter as pupae in the galls on the fallen oak leaves on the ground, before emerging in the next spring to lay eggs on the new leaves and catkins of the oak, inducing the currant galls once again. So the cycle of alternating gall types induced by this wasp continues …

While I was looking at the galls I noticed one or two aphids on the oak leaves and I suspected these were the common oak aphid (Tuberculatus annulatus). Ed Baker, who helps me with aphid identifications, confirmed they were indeed Tuberculatus, but said he’d need a specimen to confirm the species.

 

 

 

 

 

 

 

In the interim, I’ve labelled these photos here as being the common oak aphid (Tuberculatus annulatus), and will amend this if necessary, if Ed comes back with a different identification from the specimen I’ve sent him. I liked the visual combination of the hairy, deep red gall and the yellow-green of the aphid. Seen together in close up they reveal some of the wonders of the miniature world all around us, but which is rarely seen or appreciated – I had to search quite a number of the oak’s leaves to find the galls and then spot the aphids amongst them.

Something caught my eye on a nearby downy birch tree (Betula pubescens) – small protuberances sticking out from the trunk in various places. These were a new sight for me, and I thought they might be an unusual fungus.

 

 

 

 

 

 

 

However, when I sent some samples to Liz Holden, the mycologist who helps me with fungal identifications, she replied saying they were not a fungus at all, but were instead adventitious roots growing out of the tree’s trunk.

Looking at another birch tree nearby, I noticed a ladybird on some of the new shoots, so I stopped to take some photographs of it.

 

 

 

 

 

 

 

It was the 10-spot ladybird (Adalia decempunctata), which is a common species throughout the UK. Knowing that ladybirds are predators of aphids, I began searching the leaves of this birch, and very soon found some aphids on one of them. There was a large, slightly blue-ish winged aphid that I recognised as being the downy birch aphid (Euceraphis punctipennis), together with some smaller, wingless aphids which turned out to be nymphs, or an earlier life stage, of the same species.

I looked at a number of other leaves on the tree as well, but didn’t find any more aphids, so I don’t know if I was just lucky with the first ones I searched, or whether there were more on other parts of the tree that I didn’t see. However, I did spot another insect of interest – a green bug or Hemipteran, which like the aphids, sucks the sap of plants and trees. This was identified for me by Joe Botting as being the black-kneed capsid bug (Blepharidopterus angulatus). Like the ladybird, it is a common species throughout Britain, occurring on various trees, including birch.

Walking further along, I came to a group of alder trees (Alnus glutinosa) with their trunks covered in moss and some ferns growing at their base – together they formed a classic temperate rainforest tableau.

 

 

 

 

 

 

 

 

I had a quick look at some of the leaves on one of the alders and soon spotted some galls induced by a mite (Eriophyes laevis). This is another common and widespread species and the pustule-like galls are highly visible on the leaves, often bright yellow-green or even red in colour.

Just a few feet away from the alder, there were some meadowsweet plants (Filipendula ulmaria), so knowing that galls also occur on those leaves, I had a look at them. I felt like I was in ‘gall finding mode’, as almost immediately I saw some galls induced by a midge (Dasineura ulmaria) on one of the plants.

 

 

 

 

 

These galls look superficially similar to those on the alder, but midges of course are insects, whereas mites are invertebrates in the class Arachnida, along with spiders and ticks.

It’s interesting that these two very different and evolutionarily quite distinct organisms should induce similar-looking galls on unrelated plant species – alder and meadowsweet. In both cases, the galls provide protection and a food source for the mite nymphs and midge larvae respectively. This is an example of the phenomenon called convergent evolution, whereby completely unrelated species evolve similar traits or behaviours, in response to environmental or ecological factors.

Continuing further along, I came to another area with a number of large oak trees (Quercus petraea) so I left the trail and walked around in amongst them for a few minutes. It was a classic temperate rainforest setting, with lots of moss on both the trees and the rocks on the forest floor. There were also plenty of ferns, especially on the larger branches of the oaks, and I find the rich green vibrancy of these wet forests very pleasing to my eye, and also a good subject for photography.

 

 

 

 

 

 

 

 

 

Like the cloud forests of the tropics, a temperate rainforest such as this has plenty of epiphytes growing on the trees. Whereas in a tropical forest those will be bromeliads and orchids, here the epiphytes are mostly mosses, lichens and ferns.

In both ecosystems though, those plants use the trees for support, but do not take any nutrients from them. Instead, they rely on the near constant atmospheric humidity for moisture, and airborne particles of dust and organic material to provide the nourishment they need to grow. These epiphytes also play a role in intercepting some of the rain that falls, absorbing it and thereby reducing the amount that reaches the ground.

Some of that moisture will later evaporate from the epiphytes, helping to maintain a high level of humidity in the local atmosphere, and creating optimal conditions for the continued growth of the epiphytes. Mosses that grow on the trunks of the trees also absorb some of the water that flows down the trunks in times of heavy rainfall, and the capacity of the epiphytes to soak up a large quantity of moisture reduces the likelihood of flooding.

As if to emphasise this, I came across a small stream, where the water was cascading over some rocks, and it was lined in part with a couple of different fern species, including hard fern (Blechnum spicant). The upright fronds of this are the fertile fronds, which release the fern’s spores – the majority of its fronds lie flat to the ground and are sterile, playing no part in the reproductive process.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

By this time it was late in the afternoon and I was nearing the end of the circular trail in the forest. I’d read on the information leaflet about the reserve that Glasdrum is noted for the presence of a rare lichen, Norwegian specklebelly (Pseudocyphellaria norvegica), which can be seen on the trunks of hazel trees along the path, but I hadn’t found any of it yet.

When I came to an area with quite a few hazel trees growing beside the path, I began checking their trunks to see if I could spot this lichen. There was a photograph of it on the leaflet I’d picked up, so I knew what to look for, and fairly quickly I found a tree with a likely candidate lichen on it, growing next to some of the green satin lichen (Lobaria virens) that I’d seen earlier (in Part 1 of this blog). However, upon closer examination it didn’t look quite right, as the thallus (as the main body of a lichen called) didn’t have spots on it.

I was later able to get this species confirmed as being Pseudocyphellaria intricata by John Douglass, a lichenologist who very kindly helps me with identifications. Back on the trail though I soon found another lichen with spots on it, which I was sure was the Norwegian specklebelly.

 

 

 

 

 

 

 

Because I knew what to look for, it was quite a distinctive lichen when I saw it, and there were several patches on some hazels that were growing beside each other.

 

 

 

 

 

 

The common name for this species is derived from the whitish speckles on the underside of its thallus, but it is the spots on the upper surface that are conspicuous and distinctive, as in the photos above. Most lichens do not have common or English names, including the other lichen in the same genus (Pseudocyphellaria intricata) that I found on some of the hazels, but this one has been given quite a descriptive name, because of its rarity, and that helps with remembering it.

In recent years considerable work has been done to give English names to over 1,000 of the most common fungi that occur in Britain, and the same has been done for many of our moss species. A similar effort is much-needed for lichens, and I hope that someone will take on this task in the near future, as it will greatly assist in helping people to identify, and identify with, lichens.

Norwegian specklebelly is listed as Endangered on the European Red List of threatened lichens, and western Scotland, particularly Argyll, is recognised as containing the best populations of this species in the world. Like the tree lungwort (Lobaria pulmonaria) and green satin lichen (Lobaria virens) that I’d seen earlier in the day, it is a member of the Lobarion group of lichens, and is a key indicator species of Atlantic temperate rainforests of high conservation importance. Also like the lungworts, Norwegian specklebelly is a cyano-lichen, meaning that in addition to the fungus and alga that comprise all lichens, it also has a third partner in its symbiosis – a cyanobacterium (Nostoc sp.). Cyanobacteria absorb nitrogen from the air, fixing it into the thallus of the lichen, and when the lichen decays or falls to the ground, the nitrogen becomes available for other organisms. By doing so, the lichen adds natural fertiliser to the soil, and this process is an important and integral one in these temperate rainforest ecosystems.

Finding the Norwegian specklebelly was a fitting climax and highlight to what had been an excellent day of exploration in Glasdrum Wood. However, I’d only seen a very small part of its total area, so I’ll need to return another time to wander around in other parts of it, further afield from the visitor footpath. Meanwhile, here’s a compilation of some video footage that I took during the day:

Having started the day by leaving my home at 6 am, it was after 6 pm when I left Glasdrum for the 3 hour drive back to Findhorn, so it was a long trip overall. Shortly after departing from the reserve, the road passes through the village of Appin and reaches Loch Linnhe, the long sea loch that stretches northeast up to Fort William. When I reached the first viewpoint of the loch, there was some very dramatic late afternoon light, with shafts of sunlight shining through gaps in what looked like serious rain clouds. It had been dry for the entire time I’d been at Glasdrum, so this seemed like a fitting farewell gift from the day, with the rain for which the area is famous beginning to move in as I was leaving …