by Juliet Bailey.
Eight members met on a very pleasant afternoon on the last day of February to look at the lichens in Newent.
We started at a tree surrounded by a wooden guard in the Lakeside park. It wasn’t the tree that was of interest, but the guard rails which offered nice specimens of the lichen Physcia aipolia, enough for one each to be examined at a comfortable height for viewing. Everyone had a hand lens and we went through the basics of lichen structure and ecology at that point.
Next we moved to a young beech tree, its smooth trunk supporting the roundels of Phlyctis argena staring out like white eyes. I demonstrated here that a spot of potassium hydroxide on the thallus goes yellow and slowly turns red. This was compared to the immediate blood red reaction when potassium hydroxide was put on the golden yellow Xanthoria parietina from a fallen twig. A sycamore tree not far away had sheets of Hyperphyscia adglutinata.
Next we examined the lichens on the stone handrail along the top of the balustrade at the end of the lake. This was covered in completely different suite of lichens to what we had seen on the trees, all of them the thinnest crusts including Aspicilia contorta and Caloplaca aurantia. These species indicate it is a calcareous stone substrate.
We then moved into the churchyard where the majority of monuments are more acidic, displaying yet another suite of species. The dark brown Melanelixia fuliginosa was very obvious, as was the white of Ochrolechia parella. We discussed founder effect and lichenometry, ie looking at colonisation events and whether you can use the size of a thallus to date stonework. Participants quickly latched on to the fact that you can tell the pH of a stone from the lichens it carries, pointing out the few monuments that showed the orange roundels of Caloplaca (mostly C. flavescens here).
We looked at the effect of metal, seeing lichen death-zones in the run-off from copper plaques on some of the ledgers.
Anyone wanting to know more about lichens or attend Gloucestershire Lichen Group meetings (held mostly on Tuesdays in the warmer months) please contact me at glos.lichens@gmail.com.
