About six miles downstream from Dundreggan, and just a mile from where the River Moriston flows into Loch Ness, Glenmoriston narrows dramatically at a place called Levishie. The topography there steepens, and on the south side of the glen in particular the land slopes precipitously down to the river. This provides shade from the sun for most of the year, as well as some protection from the wind, and these factors, together with the constant spray of water from the gently tumbling water, create ideal conditions for a small patch of temperate rainforest to flourish alongside the river there.
I often stop at Levishie on my way to Dundreggan, and on several occasions over the years I’ve never made it any further into the glen, as I’ve found so much of interest, during what I expected to be brief stops there. In late October this year, on a wet and overcast day when I was headed towards Dundreggan, I decided to take advantage of what were ideal conditions to be in a temperate rainforest and dedicate the day to exploring the riparian area at Levishie instead of going on to our own land further up the glen.
While it may not be widely known that Scotland has its own rainforests, there are still small scattered patches of the temperate rainforest ecosystem that formerly were much more widespread in western parts of the country. From Argyll northwards to Wester Ross, most of the low-lying coastal areas would have hosted this green, mossy and distinctive forest type, while inland, along narrow river valleys such as this at Levishie, smaller pockets of rainforest would have thrived at suitable sites. Requiring year-round mild temperatures and constant high local atmospheric humidity, temperate rainforests are characterised by a profusion of ferns, bryophytes (mosses and liverworts) and lichens that cover the trees, rocks and the forest floor itself. Green is the prevalent colour everywhere, and entering a temperate rainforest is reminiscent of a tropical rainforest due to the verdant lushness of the vegetation.
During the past three decades I’ve visited many of the temperate rainforest areas of the world, from the southwest of Chile, the Fiordland region of New Zealand’s South Island and Tasmania to the laurel forests of Madeira and La Gomera in the Canary islands, as well as the Pacific Northwest of Canada and the USA. In the British Isles, I’ve been to tiny fragments of our former rainforests at Killarney National Park in Ireland and the western valleys of Wales, as well as a number of areas in northwestern Scotland. Because these more local patches of rainforest are only tiny fragments of what they must have been in the past, they are very important, both in an ecological context, and also by providing a window into another aspect of our (mostly) lost forest heritage. For me it’s always a special experience to step into their green and luxuriant umbrage, especially on a wet day like this, when temperate rainforests are at their most vibrant.
Almost immediately my eye was drawn to some tree lungwort (Lobaria pulmonaria) on a goat willow tree (Salix caprea) near the river. This was particularly lush and brilliant in coloration, with its lobes, or thallus, fully hydrated because of the rain. Tree lungwort is one of the largest lichens occurring in Scotland and is also widely distributed in old growth forests elsewhere in the northern hemisphere – in the Pacific Northwest of the USA and Canada it is considered an indicator species for temperate rainforest ecosystems.
A few feet away, there was a small mushroom growing on a moss-covered dead branch of a hazel tree (Corylus avellana). I recognised it as one of the bonnet fungi (Mycena spp.). There were several of these growing nearby, and when I later sent a sample to Liz Holden, who helps me with fungal identifications, she confirmed it as being the common bonnet fungus (Mycena galericulata).
Like tree lungwort, this species is widely distributed in the northern hemispheric, and is saprotrophic, meaning that it grows on, and decomposes, the dead wood of trees.
Hazel is one of the most common trees in this section of riparian woodland along the River Moriston, and the leaves were brilliant in their autumn colours.
Hazel is a very important component of the temperate rainforests in Scotland, and these Atlantic hazel woods, as they are known, are the habitat for a unique assemblage of lichens and fungi, as described in a recently-published book. The fungi include the unusual hazel gloves fungus (Hypocreopsis rhododendri), and a number of rare crustose lichens – those being the lichens that grow flush with their substrate, which in this case is the trunks of the hazels.
I’m not knowledgeable enough in lichen identifications to know if these hazels at Levishie are hosting any of the rare species, but the stems were completely covered in crustose lichens. These had grown contiguously with each other, so that the edge of one lichen met the edges of its neighbours, and this had resulted in the actual bark of the hazels no longer being visible on some sections of the stems.
Higher up on several of the hazels, the stems were covered in moss, and this was the case for some other trees as well, with a silver birch (Betula pendula) being a particularly good example.
The mosses and lichens that grow on the trees are known as epiphytes, and their abundance is one of the defining features of rainforests, in both tropical and temperate regions. Epiphytes are plants that grow on other plants or trees, using those for support, but not taking any nutrients from them. This distinguishes them from parasitic plants, which obtain some or all of their nutrients from their host plant or tree. In rainforests, it is the high atmospheric humidity that enables these epiphytes to flourish, as they can gain the moisture they need from water droplets in the air, and nutrients from airborne dust and litter falling from the trees above.
In temperate rainforests, the trunks and branches of the trees are completely enveloped in epiphytic mosses and lichens, sometimes forming mats or cushions several inches thick. On a small scale, these form convoluted topographical surfaces that provide a large amount of habitat for insects and other invertebrates such as springtails. These in turn attract predators including spiders and harvestmen, adding to the diversity of life in these lush green ecosystems.
Because arboreal lichens derive their nourishment from the air and rain, they are very sensitive to atmospheric pollution and tree lungwort has been used in the UK for many decades as an indicator of air quality. Its presence here at Levishie illustrates that the air in this part of the Highlands is free of pollutants and generally very clean. This is due to the absence of sources of atmospheric pollution to the west, where the prevailing winds come from. Instead, the storms that blow in off the Atlantic Ocean bring clean air, and also clear away any pollutants that have accumulated from more local sources, such as the smoke from coal burned in houses.
While most lichens consist of a symbiosis between two organisms – a fungus and an alga – tree lungwort is one of those which also includes a third partner, in this case a cyanobacterium (Nostoc sp.).
The presence of the cyanobacterium provides another mechanism by which the lichen gains nutrients, as Nostoc sp. is able to absorb, or ‘fix’, nitrogen from the air and incorporate it into the thallus, or main body, of the lichen. This complements the action of the algal partner in the lichen, which harnesses the sun’s energy through the process of photosynthesis, producing carbohydrates and sugars.
On one of the stems of the hazel there was an extensive patch of the bleeding broadleaf crust fungus (Stereum rugosum), and its shapes seemed to reflect those of the lobes of the tree lungwort.
This fungus gains its common name from the fact that if its surface is scratched, a dark red liquid oozes out, looking a little like blood. It occurs on dead wood and branches of broadleaved trees, especially hazel, and its presence here was an indication that the stem it was growing on had died. This was otherwise difficult to determine, as it was in amongst other living stems, and was mostly covered in tree lungwort, making it impossible to see if the wood was rotting or not. Like the common bonnet fungi I’d seen earlier, this species is saprotrophic, so it helps with the decomposition of the dead wood it fruits on.
While I’d spent most of the day in amongst the hazels in this area of forest beside the river, there are a number of old oak trees (Quercus petraea) there as well, and my path took me to one of those now. It looked like a quintessential rainforest tree, resplendent in its green clothing of moss, which covered all the visible parts of its trunk and branches. Indeed it is the combination of oak and hazel which is most characteristic of the temperate rainforests of the British Isles – the so-called Celtic rainforests of Britain and Ireland.
There’s something about these old, moss-covered oaks that really speaks to me. They seem particularly full of life and to have a special presence or quality about them, which makes me think of the Ents of Fangorn Forest in Tolkien’s ‘Lord of the Rings’.
I was very much enjoying taking my time in exploring this mossy green wonderland beside the river, and had progressed a mere 200 yards or so from my car during most of the day. Every few steps, there was another tree, or group of trees, decorated and embellished with vivid green moss, radiant with life on what was continuing to be a very wet day. It was ideal conditions to be in a temperate rainforest like this. People often think that it’s best to be out in Nature on sunny days, but temperate rainforests like this are at their best in the rain.
I continued on a little further, to where I knew there was another oak tree with a particular fungus fruiting on it – the oak mazegill fungus (Daedalia quercina). I’d first seen this on the tree in November 2013, but as a tough bracket fungus, it can persist for several years virtually unchanged. Sure enough, the oak mazegill was still there, just as I remembered it, with a cluster of brackets fruiting together on the trunk of the oak. This fungus is usually found on dead oaks, and this one was visibly in the final stage of its life – there were just a few twigs and branches with any leaves on them.
This fungus derives its common name from the pattern of the pore surface on the underside of each bracket, which resembles a maze, with its labyrinthine pathways. In 2013, I’d taken the photograph below, which clearly shows the mazelike pattern, and this is one of the photographs I’ve included in the 2016 edition of the Trees for Life Engagement Diary. If you’d like to support Trees for Life and enjoy my images of the Caledonian Forest each week of the year, the diary can be ordered here.
There was a lot more of the forest to explore along this section of the River Moriston, but the daylight was rapidly fading due to the overcast conditions in the afternoon, so I had to finish up for the day and head for home. However, the day has left me with an appetite for more, so it won’t be too long before I make another visit to this small but beautiful area of rainforest at Levishie.