Resurvey of the Corticolous Lichen flora of Epping Forest
Dimerella pineti was frequent and abundant at all sites although Hawksworth did not find it in 1989.
He suggested it might have been overlooked by him at that time; there is a record for 1983 from J.F.
Skinner (Hawksworth 1992). Lepraria species (L. incana and L. lobificans), Micarea prasina and
Buellia griseovirens occurred in abundance on old Beech and Oak. Cladonia species were frequent at
most sites with Cladonia coniocraea and C macilenta present at all, but in general the diversity of
Cladonia species appears to have declined along with other species considered to prefer more acidic
conditions. Hypogymnia physodes also tends to favour a low pH, but was present at three of the four
sites and thalli size exceeded that recorded by Boreham in 1993. Parmelia saxatilis was not found and
its decline is concomitant with the much impoverished areas of Epping heathland, the cause partly
attributed to increased nitrogen deposition and reduced acidity as well as poor habitat management.
Foraminella ambigua, another species that was colonising in London during high sulphur dioxide
levels, was significantly not recorded during our survey. A notable decline in the distribution of this
species in the south-east of England has occurred in the last ten years.
Frequent and abundant foliose species included Melanelia subaurifera. Pomella sulcata, Punctelia
subrudecta and P. ulophylla. Fruticose species were not found with the exception of Ramalina
farinacea with an average thallus length of 1 cm, well below rural size but typical of urban areas.
Temporal and Spatial Trends
A total of 168 corticolous and lignicolous species have been identified in Epping surveys since
records began in 1784 (Table 2, Appendix AJ. The current total of 64 represents less than a third
of the historical diversity and includes a significant number of species new to the Forest. However,
this survey was over a four day period and new species were being identified at the end of each day
suggesting that this total is not fully representative of the current Forest flora. A review of the
more recent records (Hawksworth & McManus 1991) shows that 14 species recorded then were
not found during this pilot survey although not all their sites were revisited. These were Candelaria
concolor, Cladonia coccifera, C digitata, C fimbriata, C. floerkeana, Enterographa crassa,
Foraminella ambigua, Graphis elegans, Mycoblastus fucatus, Opegrapha atra, O. vulgata,
Placynthiella icmalea, Trapeliopsis flexuosa, and Usnea subfloridana.
Fig. 2. Corticolous records from 1784 to 2003
These species are not common to the London area with the exception of Candelaria concolor.
Essex Naturalist (New Series) 20 (2003)
73