Lichens

From the Souvenir booklet issued to mark the opening of The Island on Sunday 5th June 1994:

To see the micro world of lichens we really do need an expert to guide us. These very ancient and very fragile organisms will tell us about the past environment and about the health of the present. We were very fortunate that Barbara Benfield was willing to come from the other end of Devon to survey the lichens on the Island.

Eighty four lichen species were recorded from the trees, the bridge, and a ruined linhay on 18th May 1994. The most interesting habitats were the older oaks, beech and willow. On two old oaks, one on the bank below the weir, and one at the extreme western end of the Island, patches of creamy buff thallus with orange specks indicate the presence of Arthonia vinosa, a lichen only found in places where trees have been for centuries. Such lichens are known as "old woodland indicator species".

The most exciting lichens to record were all four of the British Phaeographis. P. lyelli, and P. inusta are very local to the South Western parts of Great Britain, but not common in those areas. Phaeographis lyelli is extinct east of the New Forest. Both of these lichens are growing on oak and willow, respectively, at the eastern end near the railway bridge. Growing on the same willow, Lecidea carrollii is another uncommon lichen confined to constantly humid situations in the South West of Britain. The pale grey-white crust which is the thallus of the commoner of the two Phaeographis can be seen growing extensively on a large beech by the river.

The pale green leafy thallus of Parmelia caperata is easy to see on a fallen apple, but grows on many other trees on the Island and elswhere in Britain. Another easily recognised lichen is at the base of an old oak growing on the river bank just above the water. It is a large patch of one of the "dog lichens" Peltigera lactucifolia. The dark brown lobes are crisp and curled over at the edges so that the paler undersurface shows up clearly. This lichen will dry to a pale brown or pale grey colour. Several feet above the Peltigera is a large thick crusty patch of a pale grey-white lichen called Pertusaria albescens. Also on this oak, and on an alder beside the river near the linhay is the blue grey foliose "old woodland indicator" lichen Parmelia reddenda which is local in the South West.

Other interesting lichens recorded were Dimerella lutea, an "old woodland indicator" with green crust and small orange fruit which only grows in damp slightly shady places, and the pale blue-grey foliose species Parmelia pastillifera a light loving lichen which occasionally grows on branches. At the Island it was seen on a branch which had fallen from the canopy of a beech. A 20cm length of Usnea articulata had also blown from the canopy. This lichen is exceedingly sensitive to pollution and had become extinct in many parts of the British Isles.

Care should be taken to prevent ivy from growing over important species.

B. Benfield 26th May 1994