Bonchurch Down, Isle of Wight, Saturday 27th June 2015

A joint meeting with the new Isle of Wight Lichen Group organised by the Streets. They had found a very interesting lichen rich heathland on top of the down, which the WLG was invited to visit. We met at the car park at the end of the rough track on top of Bonchurch Down beyond the radar station SZ57327868 at 10.30am.

As well as Shiela & Les Street, and Collin Pope from the Island, Nichola Bacciu, Ginnie Copsey, Mathew Prince and Neil Sanderson came over on the ferry, with Neil Sanderson leading. The site started right by the car park (SZ573 787), but was rather trampled here. The top of the down here was capped by very flinty superficial deposits, deeply burying the chalk. The heather was short and open, but at first most of the lichens were on the flints with Rhizocarpon reductum, Buellia ocellata, Parmelia sulcata and Porpidia tuberculosa. Terricolous lichens were very thin on the ground to start with, but the tiny pioneer crusts Placynthiella uliginosa and Placynthiella icmalea were detectable if one peered closely. Larger lichens occurred sparingly including Cladonia furcata subsp. furcata and three normally epiphytic species Evernia prunastri, Hypogymnia physodes and Usnea flammea.

Trampled Heath

Further from the car park the short heather got a bit taller and the lichens bigger and denser. The Evernia prunastri and Usnea flammea were taller and Cetraria muricata, at its only known Island site appeared, along with Peltigera hymenina, Cladonia diversa and another normally epiphytic species Flavoparmelia caperata. Then we moved into a very rich area, with patchy low growing heather, with bands of flint between, which gave the impression of a montane heath developed on stone polygons at 800m in the Highlands! In reality this appeared to just be patchy heather on flints not actual relict stone polygons, but it was visually striking. Here we added Cladonia portentosa, Cladonia squamosa var. subsquamosa and well developed Cladonia gracilis to the list of Cladonia species but it was the assemblage of normally epiphytic species that was most striking. We recorded Parmotrema perlatum, Melanelixia glabratula, Parmelia saxatilis, very unusually Fuscidea lightfootii and Hypogymnia tubulosa on flint or the ground. The later was fertile, also a very rare sight. On the Heather were Hypotrachyna afrorevoluta, Parmelia sulcata, Graphis elegans, Physcia tenella and Buellia griseovirens. Also seen were the more typical heathland species Micarea erratica on a flint and Micarea viridileprosa on the soil sheltering under a flint.

Short lichen rich heathland, on less trampled area

The area of short lichen rich heath was quite small and was separated from the taller dense lichen poor heath to the north by an old trench of unknown purpose. Possibly the car park was once much bigger and the trench originally delimitated it? The acid soil exposed on the sides of the trench provided a new habitat adding the Cladonia species Cladonia coniocraea, Cladonia cryptochlorophaea, Cladonia floerkeana, Cladonia cervicornis s. str. and Cladonia ramulosa, along with smaller crusts including Trapeliopsis granulosa, Placynthiella dasaea, Lepraria incana s. str. and Micarea prasina s. lat, along with Placynthiella icmalea and Micarea viridileprosa, which had already been recorded.

After noting a few common concrete species on information plinth, we settled down for lunch, with a panoramic view over the channel. As we finished lunch, the round the Isle of Wight yacht race moved into view.

Panorama & Yacht race

After lunch, we headed north to another area of rich heath. On the way we recorded an area of Gorse scrub with young Oak (SZ573788). These supported a typical assemblage of common species on the twigs. However, Nichola collected some small black apothecia, which turned out to be Rinodina biloculata Nb (NR/DD) (pictures ). This twig species is increasingly being found in the south west on nutrient enriched twigs and is easily over looked as Amandinea punctata or Catillaria nigroclavata. It is not clear if it is spreading or simply under recorded.

We then reached the base of and old gravel pit cut into the plateau edge with short heath wth high lichen cover in its base. This was not species rich, but had some strong colonies of Cladonia ciliata var. ciliata along with Cladonia ciliata var. tenuis and Cladonia portentosa. The rim of the quarry also supported Rhizocarpon reductum on flint, Cladonia cervicornis s. str. and Cladonia diversa but was not as rich as expected. Up on the plateau, there was more short heath, which proved to be much richer. Enriched patches near the dew pond added Cladonia rangiformis and Cladonia humilis, but with a general acidic headland assemblage elsewhere. This including Cladonia portentosa, Cladonia ciliata var. ciliata, Cladonia uncialis subsp. biuncialis, Cladonia crispata var. cetrariiformis, Cladonia squamosa var. subsquamosa and Cetraria muricata along with Baeomyces rufus, Hypogymnia physodes and Trapeliopsis granulosa. The best find came on a patch of hard black humus on a abandoned path (Waymark VT01, SZ57304 78972), where we found three thalli of Heath Tooth Pycnothelia papillaria, with Cladonia uncialis subsp. biuncialis, Cladonia floerkeana, Trapeliopsis granulosa and Cladonia floerkeana. Two further patches of Pycnothelia papillaria were found to the south east on the same old patch (Waymark VT02, SZ57310 78967).

I knew Pycnothelia papillaria was a good record for the Isle of Wight; it is now a very rare and declining species in lowland Europe outside of the New Forest. I checked the 2003 Isle of Wight Flora when I got back and found, to my surprise that the only record of Pycnothelia papillaria from the Isle of Wight was made from Bonchurch Down in 1992 by a certain Neil Sanderson. He also recorded the only record of Cetraria muricata from the Isle of Wight at the same time. Now, I can remember visiting Bonchurch Down during a cycle ride around the Island, but I had totally forgotten finding Pycnothelia papillaria and Cetraria muricata then! Nice to refind them, however.

The gravel pit and northern plateau

Casting around a bit, we found no more lichen rich heath, so headed back to the car park. In the north east corner of the first lichen rich area we had looked at (SZ573 787), there was a particularly mixed area, with abundant Cetraria muricata, the best stand seen on the day, along with some Cladonia ciliata var. ciliata not seen in this area in the morning. I took the opportunity of taking some more photos of this spectacularly lichen rich heath.

Lichen rich heathland

This was an impressive but quite unusual area of lichen rich heath. The best bits were on areas of short dry heath, but it was not entirely clear why the rich areas were being kept short. Light human trampling and pony grazing appeared to be the main influences, but possibly past disturbance might have had a roll. Certainly the taller heath surrounding was very lichen poor. We found a total of 45 species growing on the heath on the ground, on flints and on the heathers (species list). Using the Cetrelia, Cladonia & Pycnothelia Index (CCP Index: that is the total numbers of Cetrelia, Cladonia & Pycnothelia taxa recorded on the ground or on heathers, this is used to assessed heathland lichen diversity) the whole site scored 18. These were very good totals for heathlands outside of the New Forest, with the site containing some species which were very rare on the Isle of Wight. Pycnothelia papillaria and Cetraria muricata are only known from this site on the Island, Cladonia ciliata is only otherwise recorded from Headon Warren and Cladonia gracilis from two other sites (The Isle of Wight Flora, 2003). The most impressive feature, however, was the shear abundance of the common epiphytes on the heather stems and on the ground in parts of the site.

An additional 16 species were noted on the scrub, including Rinodina biloculata, a Data Deficient and Nationally Rare species, which was new to the Island.

To see the route taken click on the text below.

We had some time to spare before the Lymington Ferry left, so the mainland contingent went a longer way back by Compton Down, in the west, where it had been reported that the very rare Oxtongue Broomrape Orobanche picridis was having a particularly good year. This was located in an old hollow way above the military road and admired.

Oxtongue Broomrape Orobanche picridis