Resurvey of the Corticolous Lichen flora of Epping Forest
in particular deadwood invertebrates and the moss Zygodon forsteri. A history of pollarding has
ensured the retention of a large number of veteran trees and, together with wood pasture management,
is an important contributory factor to the rich diversity of one of the most studied woodlands in
England.
Background
Lichen records for Epping go back over two centuries to the beginning of the industrial revolution.
Edward Forster recorded lichen species in the Forest from 1784 tol796 and his collections and
notebooks, housed in the Natural History Museum, provide a useful baseline against which to
assess changes in diversity and community structure to the present day. Forster recorded from all
habitats and made careful notes of substrate and location. He listed a total of 65 epiphytic species.
These early records, though incomplete, give a good indication of the community structure and
considerable diversity present at that time. Other notable surveys include those of the Reverend
James Morrison Crombie (1865-68 and 1881-1885), who provided very detailed accounts and
recorded the highest diversity over the history of the site, including many ancient woodland indicator
species (Rose & Coppins 2002). Paulson and Thompson (1911, 1913,1918 and 1920) also recorded
extensively. These historical records and a small number of surveys (unpublished) carried out by
Rose & Pentecost (1969-70) were reviewed by Hawksworth et al. (1973). They stated that of the
118 epiphytes recorded over the 170-year period only 28 remained in 1970 and the majority of
these, 22, were located in the remoter north-eastern parts of the Forest beyond Epping Town. Only
6 were recorded in the main body of the Forest.
Laundon (1970) investigated the distribution and diversity of London's lichens in the late 1960s.
He recorded only 9 epiphytic species (11% of the London flora) within a radius of 16 km from
Charing Cross, including the London Borough of Waltham Forest, the most abundant of which was
Lecanora conizaeoides. He recorded on all substrates and assigned a species range to each borough.
Waltham Forest was classified within the 16-25 species range, exceeding the neighbouring boroughs
of Hackney and the city (0-5), and Newham and Redbridge to the east (6-15), but lower than
Barnet (26-35) to the west and many of the southern sites. He considered the absence of, 'such
common species as Evernia prunastri, Lecanora expallens, Parmelia spp. (sens. lat.) and Pertusaria
spp.' as 'striking'. He attributes reduced diversity to air pollution, but also notes that urban sprawl,
changes in habitat management, and on a positive note, the protection afforded by the greenbelt,
have all played a part in the temporal and spatial changes in lichen diversity in the London area.
Hawksworth & McManus carried out a survey of the Forest between 1989 and 1991 (Hawksworth
1992). Their primary objective was to determine, 'to what extent, if any, the lichen flora on the
trees in Epping Forest had changed since the 1973 checklist' (Table 2, Appendix A). They examined
twenty sites along a transect from Leyton Flats in the south to Wintry Wood in the north, selecting
from those identified in historical records as having interesting or rare species. Many of the 'common
missing species' identified by Laundon had returned, with the notable exception of Pertusaria
species. They recorded a total of 41 lichens. Historical survey details are summarised in Table 1.
They found that their richest site, Wintry Wood, was again the most northerly; sites south of Woodford
Green closest to London, were consistently poor with only 1 to 8 species. The area between
Woodford Green and Epping Town, in the main body of the Forest, hosted 13 to 15 species. They
state, with the exception of Wintry Wood, that the greatest diversity was found in sheltered hollows
and gullies and near streams and lakes. They also recorded the thallus size of macro lichens at each
location to establish colonisation dates. Hawksworth used annual growth rates (Rose & Hawksworth
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Essex Naturalist (New Series) 20 (2003)