Lichens

Lichens

At Rannoch just about every surface becomes covered in lichens after a year or two. We are very lucky because this means that the air is pure. Lichens are ecological indicator species as they grow in profusion only when there is little air pollution.

Most people would, not unreasonably, think that lichens are a single organism but as long ago as 1867 the Swiss botanist Schwendener suggested that they are a symbiotic relationship (a relationship where both participants benefit) between an alga and a fungus. There is an interesting connection with Highland Perthshire because the children’s author, Beatrix Potter was also interested in fungi and lichens. She used to come to Dalguise on holiday with her family and did a lot of illustrations of fungi which were highly regarded. She was encouraged by the postman who was a keen amateur naturalist.

She observed and grew the spores of fungi and of lichens and she joined in the hot scientific debate about what lichens were although it is not totally clear which side of the debate she came down on. The old fashioned view had been that lichens were a single organism and the new view, at that time, was that they were a combination of fungi and algae (or Cyanobacteria). More recently researchers have shown that algae also consist of a yeast (a single celled fungus). The situation is complicated but it is clear that the fungus gains carbohydrates from the algae and it seems that the yeast may well have a role in protecting the lichen from predation.

Lichens have many different growth forms and amongst those at Rannoch we have particularly luxuriant lichens growing on trees. When there are no leaves on the trees the lichens form what appears to be a second layer of foliage and some photosynthesis can continue even in the winter.

Lichens often contain chemicals which can form the basis of cloth dyes with both subtle and vivid colours. The lichens which grow on the Schiehallion limestone pavement are white and they could well be absorbing calcium from the rock. Some lichens are specific to particular species of tree.

(25th December 2019)