Resurvey of the Corticolous Lichen flora of Epping Forest
Species absent in 1989-91 but recorded before 1920 and re-found in this survey are: Amandinea
punctata, Arthonia spadicea, Cladonia chlorophaea, Fuscidea lightfootii, Hyperphyscia
adglutinata, Hypogymnia physodes, Lecania cyrtella, Lecanora chlarotera, Lecanora dispersa,
Lecidella elaeochroma, Punctelia subrudecta, Phlyctis argena, Physcia caesia, Xanthoria
candelaria. This represents a significant recovery.
Although Pentecost and Rose (1968-70) noted the absence of Physcia spp. and Xanthoria spp.,
these are now common particularly at car parks and open areas throughout the Forest. The once
frequent Parmelia saxatilis, recorded during all three major surveys, was not refound. Hypogymnia
physodes, widely recorded by Boreham (1993), was not common.
The following selection of species, recently recorded by James, Pitt & Blatchley (pers. comm.) on
old Hornbeam at Bockhanger Wood, Mersham, Nr. Ashford, Kent are typical of those that would be
expected in a less polluted woodland of the maturity of Epping Forest (those in bold were also
previously recorded in Epping): Acrocordia gemmata, Anisomeridium biforme, Arthopyrenia
punctiformis, Arthonia spadicea, Chrysothrix flavovirens, Cliostomum griffithii, Cresponia premnea,
Dimerella pineti, Enterographa crassa, Evernia prunastri, Flavoparmelia caperata, Graphina
anguina, Graphis scripta, Lecanactis abietina, Lecanora chlarotera, L. expallens, Lepraria incana,
L. lobificans, Melanelia fuliginosa subsp, glabratula, Micarea prasina, Ochrolechia subviridis,
Opegrapha herbarum, O. ochrocheila, O. prosodea, O. vulgata, Parmelia revoluta, P. saxatilis, P.
sulcata, Pertusaria albescens var. Corallina, P. hemisphaerica, P. hymenea, P. leioplaca,
Phaeographis dendritica, Phlyctis argena, Pyrenula chlorospila, P macrospora, P. nitida,
Pyrrhospora quernea, Rinodina exigua, Schismatomma decolorans, S. niveum.
Several of these species (underlined below) arc amongst those recorded in Epping Forest by Rose
in 1970 in Wintry Wood, but not found by Hawksworth or during this pilot survey: Pertusaria
hymenea, P. leioplaca, P. pertusa, Diploicia canescens, Calicium salicinum, Graphis scripta,
Pyrrhospora quernea, Pyrenula chlorospila. The recent absence of Pertusaria spp. is surprising
with Pertusaria pertusa and P. amara unexpectedly absent from our pilot survey. However, the old
woodland species Opegrapha ochrocheila was recorded. This species is an indicator species of
the Opegraphetum fuscellae complex, that occurs on dry bark of deciduous trees and includes
Opegrapha vulgata and Pyrenula macrospora (James et al. 1977). The scattered distribution of
this species in the more sheltered inner areas of the Forest reflects the encouraging development of
a typica] woodland community not strongly influenced by nitrogen.
Conclusions
Historical records for Epping indicate that both ancient woodland species and some nitrophiles
were present before sulphur dioxide and acid rain contributed to the almost total extinction of these
species. The ancient woodland indicator species require undisturbed conditions over a period of
several centuries and sulphur dioxide pollution has almost certainly destroyed the continuity of
coverage and spread of such species. Thus the new flora is predominantly nitrophile, the old
woodland species having been entirely lost. The New Index of Ecological Continuity (NIEC) (Rose
& Coppins 2002) is a measure of ecological continuity and conservation status of woodland. An
index value above 20 is considered to be indicative of a site of conservation importance. The New
Forest has an Index value of 65 (Sanderson 1998), Burnham Beeches, located to the West of London
had an NIEC index of 5 in the 1989 records (Purvis 1989) and 7 in 2003 (pers. comm.), and
Bockhanger Woodland, 3. A site of the maturity of Epping could be expected to carry a flora
similar to that recorded at Burnham Beeches or Bockhanger Wood. They are considerably better
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Essex Naturalist (New Series) 20 (2003)