Observations

Winter is the time to appreciate lichens.

| jaclyn

Look at the dog lichen in the frost.

Dog lichen with frost and Dog lichen with fruiting bodies


On the underside of a dog lichen there are white root-like structures. They are supposed to resemble the teeth of a dog. Although, the orange-red fruiting bodies, in my view, are more indicative as they look like blood dripping from fangs. It was due to having associations with dogs that, historically, these lichens were considered as a cure for rabies. Nowadays, they are indicative of wet places.

There are many different lichens, growing on almost any surface, including trees, rocks, soil, and artificial surfaces such as concrete and tarmac.

At this time of year, they are more noticeable because there are no leaves on the trees.

Lichens are a partnership between a fungus and one or two types of algae.

The fungus gives the lichen structure providing a layer around the algae protecting it from extremes of temperature and drought.
In return, algae through photosynthesis provides carbohydrate nutrition for both partners.

There are three distinctive types of Lichen

Crustose lichens are the first type to consider, and their name comes from their crust-like appearance on a surface. They are too hard to dislodge, even when scratching them with a fingernail.

Crusty lichen on a fence

The second type is the leafy lichens, often referred to as Foliose lichens, and unlike the group above, you can lift them off their surface with the scratch of a fingernail.

A leafy lichen on bark

Finally, the third type is the Fruticose lichens. Bushy in appearance, these lichens are usually only attached by one sucker-like hold fast.

Bushy lichen on a twig

Lichens are highly sensitive to air quality, and as a result, they are good indicators of air pollution.

In the past, sulphur dioxide affected air quality, and because of this, very few lichens could survive, but as air quality improved, lichens started to reappear.

The rule was the fluffier the lichen, the cleaner the air.

It will be interesting to see if, in the future, increasing levels of nitrogen from car use and farming will have a detrimental impact on lichens as not all lichens can tolerate high levels of this type of pollution.

Velvety Green, Icy White and Vivid Copper 

Three images of the different colours of winter. Mossy green on trees, white hair ice in a rosette pattern and copper beech leaves against the slate grey of water.
| jaclyn

If asked to describe the colours of winter, I would come up with drab greys and browns, which are not very inspiring.
However, I have noticed on recent walks that these drab tones are merely the backdrop for more vivid colours to pop.

The first colour to pop was the velvety green cloaking the trees.
Not a colour you associate with trees in winter.
Green is the colour you notice in spring as fresh new leaves burst out their buds.
Yet here we are in the middle of winter, and I see green trees.
At this time of year, it is not leafy green but instead mossy green.
But is it just mossy green?
On closer examination, different lichens and ferns also play their part in brightening a winter’s walk through the woods.

The next colour to pop was icy white, in the form of white clumps forming on the dead branches of trees scattered on the woodland floor.
Closer examination revealed delicate strands of ice forming beautiful intricate patterns, a phenomenon known as hair ice.

For this to occur, the conditions required are specific.
Rotting wood from broad-leaved trees in a moist atmosphere where the temperature is below freezing enables water to push out of the pores. Then if a specific fungus is present, stable strands of ice will form that can create beautiful formations.
If you are interested in a more detailed description, it is worth visiting the Met Office website for more information.

Finally, the vivid copper tones of the leaves from young beech trees go well with the velvety green of the moss, and when viewed next to the river, they stand out.
Beech trees, particularly young ones, hang onto their withered leaves during winter.
They are not the only trees to do this, as oaks also do it as part of a phenomenon called marcesence.
There appear to be different explanations as to why trees do this.
One explanation is that it could be to protect leaf buds as they form during winter, another is that it provides a source of nutrients for the tree when they eventually fall off.

Whatever the reason, the vivid copper of the beech and the velvety green of the moss, together with the icy white of hair ice when it is around, all brighten up what could be a drab walk in winter.