Alan Watson Featherstone, the founder of Trees for Life, writes about his experiences out in the Caledonian Forest, and about his work for the charity.


Hair ice and frosted lichens

Lobes and apothecia of a dog lichen (Peltigera sp.) and moss covered in frost, in the gorge at Inverfarigaig.

Lobes and apothecia of a dog lichen (Peltigera sp.) and slender mouse-tail moss (Isothecium myosuroides) covered in frost, in the gorge at Inverfarigaig.

In the middle of December, on a cold and frosty morning, I decided to make a return visit to Inverfarigaig, to explore more of the temperate rainforest in the gorge there. I’d spent a very satisfying day at the site in early November, which featured in a recent blog I wrote, and my appetite had been whetted then to discover more of this special area, on the southeast side of Loch Ness. On that day I’d spent almost all my time in a very small section of the gorge, and I suspected that there would be a lot more of interest, if I looked at other parts of the area.

Moss-covered trees in the temperate rainforest area at the convergence of the Farigaig River and a smaller tributary in the foreground.

Moss-covered trees in the temperate rainforest area at the convergence of the Farigaig River and a smaller tributary in the foreground.

Another reason for going was that I’d photographed some bracket fungi on a fallen log on that earlier visit, thinking it would be straightforward and easy to identify them from the photos when I got back home, but that had turned out not to be the case. I hadn’t collected any samples of those fungi in November, so I planned to do so now, so that I could send them to Liz Holden, the mycologist who helps me with fungal identifications. Upon reaching Inverfarigaig, I headed straight for the log with the bracket fungi, near where a tributary burn flows into the Farigaig River itself, and collected one of the many brackets on it as a specimen.

Hair ice on the dead stem of a hazel (Corylus avellana) in temperate rainforest beside the Farigaig River.

Hair ice on the dead stem of a hazel (Corylus avellana) in temperate rainforest beside the Farigaig River.

While I was doing this I noticed some unusual white patches on the dead stems of a couple of hazels (Corylus avellana) a few feet away, so I went to take a closer look at them. As I approached I could see that the patches were composed of very fine and delicate white strands of ice packed closely together, and all lined up parallel with each other. I assumed that these formations were what are known as frost flowers, which I’d heard of before, and had seen photographs of on various occasions, but I hadn’t encountered them personally until now. They were extraordinarily beautiful, and I studied them closely with appreciation and wonder, whilst trying not to breathe out on them, which could have led to them melting from the heat of my breath. It was an almost perfectly wind-still morning, but an occasional slight breeze caused some of the filaments to vibrate very slightly in the gentle air currents, almost like the strings of a harp.

Closer view of the hair ice on the dead hazel stem.

Closer view of the hair ice on the dead hazel stem.

It was only a few days later, after some of the photos I took were posted on Trees for Life’s Facebook page, that I discovered, as a result of someone’s response there, that this phenomenon is called hair ice.

Detail of the hair ice on the dead hazel, showing the structure of the filaments.

Detail of the hair ice on the dead hazel, showing the structure of the filaments.

 

 

 

 

 

 

This section of the hair ice was emerging from part of the dead hazel stem that was covered in moss.

This section of the hair ice was emerging from part of the dead hazel stem that was covered in slender mouse-tail moss (Isothecium myosuroides).

Apparently, hair ice only occurs on dead wood (whereas frost flowers can appear on living plants), and does so on nights when the air is humid (i.e. with a lot of moisture content) but just above freezing, while the ground temperature is just below zero degrees. Although this phenomenon has been known of for a long time, and a theory was first postulated for its cause over a century ago, it was only in 2015 that it was confirmed that it is the presence of a fungus, Exidiopsis effusa, that is the key factor in the development of these beautiful ice shapes.

Another view of the hair ice and the moss on the dead hazel.

Another view of the hair ice and the slender mouse-tail moss (Isothecium myosuroides) on the dead hazel.

In this closer view, the fine detail of the individual ice filaments can be seen.

In this closer view, the fine detail of the individual ice filaments can be seen.

 

 

 

 

 

 

 

The fungus facilitates the formation of these very thin filaments of ice, which have a diameter of about 0.02 mm, on exposed dead wood (never on tree bark) and enables their continuous growth or extrusion into these parallel curled shapes. A time lapse video showing the growth of some hair ice can be seen here on the BBC website.

This section of the hair ice looked like it had been curled by an invisible wave, frozen in the act of breaking across the dead hazel stem.

This section of the hair ice looked like it had been curled by an invisible wave, and then frozen in the act of breaking across the dead hazel stem.

Closer view showing where the ice hairs emerge from the wood.

Closer view showing where the hair ice emerges from the wood.

 

 

 

 

 

 

Another patch of the hair ice, showing the structure of the filaments.

Another section of the hair ice, showing the structure of the filaments.

Individual ice hairs can be up to 20 cm. long, but are ephemeral, melting as soon as the temperature rises, or the sun shines on them. However, in ideal conditions they can persist for hours or even some days, with the fungus acting like anti-freeze, preventing the individual hairs from recrystallising and merging together to form larger ice structures. This has been confirmed by experiments in which the fungus was removed with a fungicide, and although ice still formed on the wood, it was of a more normal crust-like shape, without all the individual hairs in parallel with each other.

Another view showing the ice hair patches in the wider perspective of the woodland at Inverfarigaig.

Another view showing the hair ice  patches in the wider perspective of the woodland at Inverfarigaig.

In this wider angle view, several different clusters of the hair ice have grown on this dead hazel.

In this wider angle view, several different clusters of the hair ice have grown on this dead hazel.

 

 

 

 

 

 

 

I found a number of these dead hazel stems in the vicinity that also had hair ice on them, including some with multiple patches. It was also very obvious that the phenomenon was only occurring on dead hazels, as there was no hair ice on living ones.

Tree lungwort (Lobaria pulmonaria) with its thallus fringed with frost crystals.

Tree lungwort (Lobaria pulmonaria) with its thallus fringed with frost crystals.

After spending quite a while with the hair ice, I turned my attention to another manifestation of the cold weather – delicate crystals of frost that were adorning various lichens and mosses on the trees. As a temperate rainforest, this woodland in the gorge at Inverfarigaig is characterised by an abundant proliferation of moss and lichen species that cover many of the trees, the rocks and in some places the ground itself, giving the site the characteristic lush, green, exotic appearance of this ecosystem.

Closer view of the tree lungwort (Lobaria pulmonaria) and its fringe of frost crystals.

Closer view of the tree lungwort (Lobaria pulmonaria) and its fringe of frost crystals.

Some of the hazels were hosting good colonies of tree lungwort (Lobaria pulmonaria) – one of the largest lichens in the UK – and the presence of which is an indicator of temperate rainforest, both here in Britain, and more commonly, in other parts of its range such as the Pacific Northwest of North America. Tree lungwort is easy to identify, with its large, irregularly-shaped lobes, which have a rippled green surface to them. On this day, they were all fringed with a delicate tracery of frost crystals, making them stand out from the moss behind.

A larger patch of tree lungwort (Lobaria pulmonaria) with slender mouse-tail moss (Isothecium myosuroides) amongst its lobes.

Wider view of the same patch of tree lungwort (Lobaria pulmonaria), with slender mouse-tail moss (Isothecium myosuroides) amongst its lobes.

This gorge area at Inverfarigaig provides ideal conditions for these temperate rainforest lichens to flourish, and the extensive patches of tree lungwort there are some of the largest I’ve come across in Scotland.

Sections of the stems of this fallen hazel were completely encrusted with tree lungwort (Lobaria pulmonaria).

Sections of the stems of this fallen hazel were completely encrusted with tree lungwort (Lobaria pulmonaria).

 

 

 

 

Tree lungwort (Lobaria pulmonaria) with a dog lichen (Peltigera praetextata) above on the stem of a fallen hazel.

Tree lungwort (Lobaria pulmonaria) with a dog lichen (Peltigera praetextata) above it on the stem of a fallen hazel.

On some of the hazels there were clusters of another group of large foliose, or leaf-like, lichens – the dog lichens (Peltigera spp.). There are a number of different species of dog lichens occurring in Scotland’s temperate rainforests, and as a group they are easy to recognise, although it’s harder for a non-expert like me to identify individual species amongst them. In this case I had to rely on the assistance of John Douglass, a lichenologist who helps me with identifications, to name the particular species I photographed.

Dog lichen (Peltigera praetextata) with many brown apothecia, on the branch of a fallen hazel.

Dog lichen (Peltigera praetextata) with many brown apothecia, on the branch of a fallen hazel.

All lichens are compound organisms, consisting of a fungus and an alga growing so closely together in a symbiotic, mutually beneficial relationship that they are only given one scientific name. However, the dog lichens, like tree lungwort, have a third partner in their symbiotic partnership – a cyanobacterium (Nostoc sp.). Cyanobacteria have the ability to absorb or ‘fix’ nitrogen from the atmosphere, incorporating it into their physical structure, and when the lichens they are part of die and fall to the forest floor, this nitrogen becomes available for other organisms to utilise. This is therefore one of the ways in which the forest improves its own fertility, through the transfer of nitrogen from the air to plants and then the soil.

Apothecia of a dog lichen (Peltigera praetextata) covered in frost crystals, amongst slender mouse-tail moss (Isothecium myosuroides) .

Closer view of the apothecia of a dog lichen (Peltigera praetextata) covered in frost crystals, amongst slender mouse-tail moss (Isothecium myosuroides) .

The brown lobes on the edges of the dog lichen’s thallus are called apothecia, and these are the structures that release the spores of the fungal partner in the lichen.

Apothecia of a dog lichen (Peltigera praetextata) above a lobe of tree lungwort (Lobaria pulmonaria), fringed with frost crystals.

Apothecia of a dog lichen (Peltigera praetextata) above a lobe of tree lungwort (Lobaria pulmonaria), fringed with frost crystals.

 

 

 

 

 

 

 

With the frost decorating the lichen apothecia like tiny chandeliers, there was a whole miniature world of wonders to explore on the branches of these fallen hazels, and I spent quite a while marvelling at these delicate and ephemeral works of natural art.

Another patch of the dog lichen (Peltigera praetextata) growing below a common polypody fern (Polypodium vulgare) on the stem of a fallen hazel.

Another colony of the dog lichen (Peltigera praetextata) growing below a common polypody fern (Polypodium vulgare) on the stem of a fallen hazel.

Another group of apothecia on a different patch of the same dog lichen (Peltigera praetextata).

Another group of apothecia on some dog lichen (Peltigera sp.) that couldn’t be identified to species level from the photograph.

 

 

 

 

 

 

Slender mouse-tail moss (Isothecium myosuroides) with spore capsules, covered in frost crystals.

Slender mouse-tail moss (Isothecium myosuroides) with spore capsules, covered in frost crystals.

 

 

 

 

The mosses too were festooned with frost, and the shapes of these tiny ice structures seemed to echo, and extend, those of the leaves of the mosses themselves.

Mamillate plait-moss (Hypnum andoi) with abundant spore capsules, covered in frost crystals.

Mamillate plait-moss (Hypnum andoi) with abundant spore capsules, covered in frost crystals.

Some patches of moss were distinguished by the spore capsules rising vertically up out of their foliage, creating a diminutive landscape of bryophyte periscopes, seeming to peer at their surroundings. In reality, of course, the capsules contain the moss’ spores, and their additional height facilitates the distribution of the tiny spores by the wind, enabling the moss to establish new colonies at suitable sites some distance from their parent.

Some more of the same dog lichen (Peltigera praetextata) amongst slender mouse-tail moss (Isothecium myosuroides), covered in frost.

Some more of the same dog lichen (Peltigera praetextata) amongst slender mouse-tail moss (Isothecium myosuroides), covered in frost.

Here the fang-like rhizines can be seen on this patch of dog lichen (Peltigera praetextata), while there's also some tree lungwort (Lobaria pulmonaria) in the booth right of the image.

Here the fang-like rhizines can be seen on this patch of dog lichen (Peltigera praetextata), while there’s some tree lungwort (Lobaria pulmonaria) in the bottom right.

My attention kept being drawn back to the dog lichens though, and I spent quite a long time taking photographs of them. I’m fascinated by the patterns and shapes of their apothecia, and how they contrast so dramatically with the thallus in their colour, form and texture.

Moss-covered trees and a fern beside the small tributary burn, just upstream from its junction with the Farigaig River.

Moss-covered trees and a fern beside the small tributary burn, just upstream from its junction with the Farigaig River.

Eventually I did move on however, and went over to the edge of the watercourse, where the small tributary burn merges with the Farigaig River itself. The moss-covered trees there create a strong and vivid visual impression of the green lushness of the temperate rainforest ecosystem.

Here the tributary burn on the right flows into the Farigaig River behind, in the midst of a nice stand of moss-covered trees.

Here the tributary burn on the right flows into the Farigaig River behind, in the midst of a nice stand of moss-covered trees.

 

 

 

 

 

 

Another view of the mamillate plait-moss (Hypnum andoi) on a dead hazel stem with hair ice emerging from it.

Another view of the mamillate plait-moss (Hypnum andoi) on a dead hazel stem with hair ice emerging from it.

 

It was now the middle of the afternoon and the daylight was beginning to fade. There were some other patches of hair ice nearby, so I finished up for the day by taking a few more photographs of them.

Hair ice on the underside of a dead hazel stem with mamillate plait-moss (Hypnum andoi) on the upper side.

Hair ice on the underside of a dead hazel stem with mamillate plait-moss (Hypnum andoi) above.

 

 

 

 

 

 

Detailed view of some of the hair ice on a dead hazel stem.

Detailed view of some of the hair ice on a dead hazel stem.

 

Having never seen hair ice before, I’d spent much of the day appreciating and photographing this remarkable phenomenon of Nature. I’d been aiming to make the most of the unique opportunity offered by the conditions at Inverfarigaig on this day, recognising that it might be years before I encountered hair ice again.

With thanks to John Douglass and Gordon Rothero for their assistance in identifying the lichens and mosses respectively, that are featured in this blog.

7 Responses to Hair ice and frosted lichens

  1. Fiona Mill says:

    Dear Alan, it’s a while since I left a comment, but thank you for another piece of thought-provoking and informative writing. The photography as always captures the place so well that the effect for me is almost tactile.
    Congratulations on being listed in the Guardian alternative New Year Honours list. Well-deserved and a tribute to the great work you’re doing here and world-wide. Warm wishes, Fiona

    • Hi Fiona,

      Many thanks for your comment – it’s very heart-warming to get feedback like this for my writing and photography. I was rather surprised, but delighted, to be included on the Guardian New Year’s list, and that has given me a great start to 2016., as does receiving comments like yours.

      With best wishes,

      Alan

  2. Ashley says:

    Another amazing post!

  3. Hi Alan – down here in Moffat in Dumfriesshire we have a Gallow Hill which is covered in hair ice. I am involved in an effort to bring together a community purchase of the hill this year – we have a landowner willing to sell. The hill has a fascinating history and I am hoping the hair ice may be an indicator of other rare fungus. If you get the chance please visit Friends of Gallow Hill on Facebook and have a look.
    Best wishes, Robbie Porteous, Moffat

  4. Wonderful photos. Interesting information about the cyanobacterium. Here’s an article in which you might be interested – “Toby Spribille … has shown that that largest and most species-rich group of lichens are not alliances between two organisms, as every scientist since Schwendener has claimed. Instead, they’re alliances between three. All this time, a second type of fungus has been hiding in plain view.”http://www.theatlantic.com/science/archive/2016/07/how-a-guy-from-a-montana-trailer-park-upturned-150-years-of-biology/491702/
    Ya gotta love it!

    • Hi Peggy,

      Many thanks for your comment, which I’ve just seen. I wasn’t aware of the research that article refers to, so I’m very grateful to you for providing the link to it. In fact I did know that some lichens (e.g. tree lungwort, Lobaria pulmonaria) have a third partner in their symbiosis – a cyanobacterium – but that’s different to what Toby Spribille has discovered. Life on Earth, and the relationships between different organisms, is revealed as being more complex and interconnected the closer we look at it!

      With best wishes,

      Alan

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