Botanical Journal of the Linnean Sociery (1989), 101: 103-109.
Lichens at Dungeness
JACK R. LAUNDON
Department
SW75BD
of Botany, British
Museum (Natural History), Cromwell Road, London
LAUNDON,J. R., 1989. Lichens at Dungeness. The lichen vegetation at Dungeness is reviewed.
The most important lichen communities are of three types. Firstly, there are the crustose lichens
which colonize the bare pebbles. Secondly, the tracts of rich Cladonia turf which form the lichen
heath and which play a major role in the vegetation cycle. Thirdly, there are the epiphytes on Prunus
scrub. In addition, lichens on artificial substrates, especially wooden fences, are noteworthy. About
150 species occur, amongst the most interesting being Cladonia mitis, Lecanora helicopis, Lecidea insidiosa,
Parmelia soredians, Rinodina aspersa and Usnea glabrata. A new combination is made in the genus
Porpidia. The term 'bird farming' is published. The fragmentation of the vegetation by building and
gravel extraction receives critical comment.
ADDITIONAL KEY WORDS:-Bird farming- conservation.
CONTENTS
103
104
105
106
108
109
Introduction .
Crustose lichens on pebbles
Lichen heath .
Scrub.
Artificial substrata.
References
INTRODUCTION
Shingle beaches are amongst the least hospitable habitats for plants and
animals. The ground is composed of rounded pebbles, over which there is
initially little or no soil. The pebbles are unstable, in as much as they are subject
to movement by wave action immediately by the coast and trampling by feet or
vehicles elsewhere. There is no shade from the heat of the sun and little respite
from the wind carrying salt spray. In such extremes only specially adapted
plants and animals can flourish, and amongst these are certain lichens. These are
poor competitors and need open vegetation for survival. Each lichen consists of a
fungus and a photobiont (an alga or cyanobacterium) living together, the latter
providing the nutrients. This mode of nutrition enables lichens to exist in places
which are inhospitable to other plants. There are about 1500 species in Britain.
From Dungeness 148 lichen species are reported, plus another ten requiring
confirmation of identification. Specimens of many of these are housed in the
herbarium of the British Museum (Natural History), London; those studied for
the writing of this paper are cited '(BM!)'.
103
0024-4074/89/090103+07 $03.00/0
© 1989 The
Linnean Society of London
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J. R. LAUNDON
At Dungeness the shingle consists almost entirely of flint pebbles which the sea
has, in the past, heaped up into ridges. Five separate beaches have been formed
successively from west to east, with belts of marsh between them. The five are
Jury’s Gap, Forelands, Holmstone, West Ripe, and Denge Beach. This last was
mostly formed between about AD 750 and the present time (Lewis & Balchin,
1940: fig. I ) , and is the most extensive and important. It now extends inland for
a distance of 5 km.
The pebbles are acid and, therefore, calcicolous plants are scarce. Along the
southern shore there is a prominent, largely natural ridge of unstable shingle.
The only common plant here is seakale, Crambe maritima L., which grows on top
of the ridge and down the landward side. This plant is confined to the littoralfringe or drift line, with no associated lichens, except for a few growing on
driftwood.
CRUSTOSE LICHENS ON PEBBLES
Behind the southern coastal ridge the bare shingle is colonized by crustose
lichens. These are pioneer species-the first colonizers, which become crowded
out when growing on other rocks. They are small and often poorly developed.
The dominant species on pebbles adjoining the drift line is Rhizocarpon richardii
(Lamy ex Nyl.) Zahlbr. (R. constrictum Malme). This forms a zone 300 m wide,
extending from Pen Bars westwards to the Wicks, a distance of 5 km where it
blackens the pebbles, with up to 25% cover.
An interesting lichen of this zone is Lecanora helicopis (Wahlenb. ex Ach.) Ach.,
which is frequent on sheltered pebbles at Abnor Pit, near Galloways, alongside a
salt-marsh (BM!). This species is quite rare in lowland Britain.
Rhizocarpon richardii declines away from the drift line but is replaced by other
encrusting lichens, of which Buellia aethalea (Ach.) Th.Fr. is much the most
abundant. Rhizocarpon obscuratum (Ach.) Massal. is also common, whilst Aspicilia
caesiocinerea (Nyl. ex Malbr.) Arnold and the dark foliose lichen Parmelia
glabratula (Lamy) Nyl. subsp. fuliginosa (Fr. ex Duby) Laundon are frequent on
sheltered pebbles. The sorediate Rinodina aspersa (Borrer) Laundon (Buellia
aspersa (Borrer) P. James, Rinodina fatiscens (Th.Fr.) Vainio) (BM!), described
from flints in Sussex, is now scarce. Two other sorediate lichens occurring on
pebbles are Porpidia soredizodes (Lamy ex Nyl.) Laundon, comb. nov.*
and P. tuberculosa (Sm.) Hertel & Knoph, both of which are local. Another local
species is Lecidea erratica Korber, distinguished by the presence of abundant
pycnidia. This lichen has many noteworthy synonyms, including L. chalybeiza
Nyl., L. expansa Nyl. ex Mudd (1861) non L. expansa Chevall. (1826), and
L. myriocarpoides Nyl. Research on the taxonomy and nomenclature of Aspicilia
caesiocinerea, Buellia ocellata (Flotow) Korber (B. verruculosa auct.) , Rhizocarpon
richardii, and Rinodina aspersa has been carried out and published (Laundon,
1986a). The association Lecideetum erraticae was described from Dungeness
(James, Hawksworth & Rose, 1977: 394-395).
*Basionym: Lccidea crustulata [subsp.] soredizodes Lamy ex Nyl. in Flora, Jena 66: 534 ( 1 xii 1883). Type:
France, Hautes-Pyrknkes, Cauterets, sapinikre du Riou, on slate, 22 vii 1883, “Ex Nyl.”, Lamy de la Chapelle,
Lichens des environs de Cauterets . . . 1883 . . . fax. 11 p. 36 (PC!-holotype [TLC: stictic acid; medulla I-], HNyl. 16241 !-fragment, EM!-slide collection).
LICHENS AT DUNGENESS
105
LICHEN HEATH
Within the Rhizocarpon richardii zone, communities of Cladonia lichens begin to
develop. The most common species near the sea is Cladonia rangiformis Hoffm.
forming bushy clumps of whitish-grey forked thalli. Associated species are the
yellow Cladonia foliacea (Huds.) Willd. and the grey Cladonia cervicornis (Ach.)
Flotow, both characteristic of bare shingle with little surface humus. Ferry,
Barlow & Waters (1989) have shown that the shingle is less acid at the coast
than inland, which probably accounts for the different lichen flora near the sea.
One of the main flowering plants in this community is Sedum anglicum Huds., the
English stonecrop.
Away from the sea, the development of the vegetation is related, at least to
some extent, to the level of the water-table below the shingle surface. In hollows
where water is present sallow (Salix spp.) scrub develops, and rich aquatic and
marsh communities occur (Ferry & Henderson, 1984; Ferry & Waters, 1988).
These are amongst the few natural freshwater pools on shingle in lowland
Britain. Where the water-table comes within a metre of the surface, lichen heath
and scrub develops. Where the shingle is very dry, the landscape is quite barren
and only a few crustose lichens are found, as on the site of the current RSPB
excavation at Walkers Outland. The absence of plant colonization on parts of
Dungeness is especially interesting and controversial. Are these deserts really
natural?
Alongside the hollows, and on the ridges on the eastern side of Denge Beach,
lichen heath has formed. In this community one of the reindeer lichens, Cladonia
portentosa (Dufour) Coem., is dominant, associated with the moss Dicranum
scoparium Hedw., the grass Festuca filiformis Pourret (F. tenuifolia Sibth.), sheep's
sorrel (Rumex acetosella L.), and wood sage ( Teucrium scorodonia L.). This
vegetation type is described by Ferry et al. ( 1989). Lichens establish only where a
suitable anchorage is available and where humus has been formed from moss
shoots and a variety of flowering plants, notably broom (Cytisus scoparius).
A few other lichens occur in the lichen heath, but only Cladonia gracilis (L.)
Willd. is constantly present, yet has low cover values. The most exciting lichen in
this community is Cladonia mitis Sandst. Dungeness is the only locality in England
for this otherwise arctic lichen. It is apparently a post-glacial relic, which
survived the forest maximum in open coastal habitats near Dungeness; the
Nottingham catchfly Silene nutans L. is believed to have survived in a similar way
on nearby chalk cliffs (Rose, 1957: 68). In 1955 P. W. James and I collected
Cladonia mitis between Lydd-on-Sea Station (now gone) and Dungeness Point
(BM!); it was collected again from this area by P. W. James in 1958 (BM!), but
has not been seen from there in recent years. Fortunately, it still grows on the
Ministry of Defence Ranges (BM!), but there are only four plants
present-perhaps the last four plants in England.
Other members of the lichen heath include Cladonia ciliata Stirton var. tenuis
(Florke) Ahti, Cladonia furcata (Huds.) Schrader, and Coelocaulon aculeatum
(Schreber) Link. Between Pen Bars and Galloways, lichens which are normally
corticolous (Evernia prunastri (L.) Ach., Hypogymnia physodes (L.) Nyl., Parmelia
caperata (L.) Ach., and P. sulcata Taylor) are common on the shingle. However,
the heath is remarkable for the extraordinary dominance of Cladonia portentosa
and the low cover values of other lichens, and for its stability in occupying
I06
J. R. LAUNDON
the same areas over many decades, as shown by the study of old air photographs.
Before 1958 Dungeness was undeveloped and unspoilt. I first visited it in 1952
and never expected that it would become so damaged in later years. In 1952 the
landscape was idyllic. The best and most extensive area of lichen heath was to
the west of the Grand Redoubt fortress. In 1958 everything changed. The
Central Electricity Generating Board issued a Compulsory Purchase Order for
land for a nuclear power station. The Nature Conservancy (1958) opposed the
order at an enquiry, but they unfortunately lost the case. This decision in favour
of the CEGB led the Nature Conservancy to make a grave error ofjudgment. In
1959 it abandoned plans for a proposed nature reserve because “repercussions of
the power station on the remaining area shows conclusively that the future
scientific interest will be too much reduced to qualify it for National Nature
Reserve status” (Nature Conservancy, 1960: 38). Yet in 1977 it admitted that
the “construction of a nuclear power station has detracted little from this value”
(Ratcliffe, 1977: 52), no reduction in interest outside the power station having
taken place.
In the late 1950s large-scale gravel winning was established on the beaches
(Findon, 1985: 16). The chief operator was the Amey Roadstone Corporation, a
subsidiary of Consolidated Gold Fields Ltd. Their most controversial
development was the digging of a large gravel-pit within the Royal Society for
the Protection of Birds reserve next to the Open Pits. This is called Burrowes Pit,
named in honour of Mr R. B. Burrowes, who devoted his savings to the
conservation of the beach. It was begun in 1970 and completed in 1977. The
RSPB obtained a substantial income from the sale of gravel royalties. In the year
ended 31 March 1974 alone, it received E56304 in mineral royalties (Royal
Society for the Protection of Birds, 1974: 7). It may be questioned whether this is
taking bird farming” too far to engage in open-cast mining in what is regarded
as a nature reserve. This and other gravel-pits have now fragmented the lichen
heath and other shingle vegetation into a series of isolated pockets in contrast to
its former continuous glory. The loss of the stone curlew, Burhinus oedicnemus (L.),
as a breeding species from Dungeness (Scott, 1985:86) may reflect this
fragmentation.
SCRUB
Scrub occurs on the shingle where conditions are suitable. In wet hollows it is
of sallow (Salix cinerea L.). On drier shingle the scrub is of four types: gorse (Ulex
europaeus L.), broom (Cytisus scoparius (L.) Link), blackthorn (Prunus spinosa L.),
and holly (Ilex aquifolium L.).
Old willow scrub has a good lichen flora; it is well described by Ferry &
Waters (1984). It is especially noteworthy for the abundance of Lecanora confusa
Almb., and for the occurrence of Parmelia reticulata Taylor, recorded from Salix
between the Open Pits (Ferry & Waters, 1984: 154).
Gorse forms a plagio-climax at Dungeness in disturbed areas. Its lichen flora
has been little studied, but is considered to be of minor importance. Broom is
*Bird farming is a term, introduced by Mr F. H. Brightman, to denote the artificial alteration of land to
attract certain types of bird life. The Scrape at Minsmere RSPB Reserve in Suffolk is an outstanding example
of the art.
LICHENS AT DUNGENESS
107
much more interesting, because it is involved in a unique vegetation cycle on the
lichen heath (Scott, 1965: fig. 6; Peterken & Hubbard, 1972: fig. 10).
Broom colonizes shingle ridges inland from the coast. Plants die from the
centre and their rotting wood forms a layer over the shingle. This rotting wood is
colonized by cup lichens of the Cladonia chlorophaea (Florke ex Sommerf.)
Sprengel complex. The wood decays away, Cladonia chlorophaea dies, and various
flowering plants and lichens, especially Cladonia portentosa, replace it.
Recolonization by Cytisus may occur again, and the cycle is then repeated.
Several different chemotypes of the Cladonia chlorophaea complex occur on the
dead broom, and have been studied by Ferry & Pickering (1989). Dungeness is
one of the best places for work on this type of chemical variation in lichens.
Transition zones from shingle to alluvial soils occur on the landward side of all
the beaches. Both here and around the Open Pits colonization by prostrate
blackthorn scrub is evident. The bushes are often richly covered with fruticose
lichens, especially Evernia prunastri, Hypogymnia physodes and Usnea subjloridana
Stirton. The nuclear power station has no overt effect on this lichen vegetation.
The most interesting blackthorn lichen found in recent years (in 1976) is Usnea
glabrata (Ach.) Vainio (BM!), long thought to be extinct in Britain. B. W. Ferry
has found Usnea rubicunda Stirton recently on blackthorn on the west side of the
Ranges. I remember seeing this red Usnea locally abundant on blackthorns at the
Open Pits in 1955; it has, alas, long been extinct from Denge Beach. Fortunately,
Usnea cornuta Korber ( U. injlata (Duby) Motyka) is still locally abundant on
Walkers Outland. Other noteworthy lichens found on blackthorn include Bryoria
fuscescens (Gyelnik) Brodo & D. Hawksw., collected by F. Rose and B.J. Coppins
in 1968 (BM!), and Cetraria chlorophylla (Willd.) Vainio, seen in 1987.
Before 1878, Nephroma laevigatum Ach. (Nephromium lusitanicum (Schaerer) Nyl.),
Parmeliella plumbea (Lightf.) Vainio (Pannaria plumbea (Lightf.) Bory), Sticta
fuliginosa (Hoffm.) Ach., Sticta limbata (Sm.) Ach. (BM!), and Teloschistesjlavicans
(Swartz) Norman (BM!-last specimen collected by W. H. Hammond, received
1905) grew on the blackthorns "near the ponds" [i.e. Open Pits] (Holmes,
1878), but all are now extinct. Lobaria pulmonaria (L.) Hoffm. (BM!) and Lobaria
scrobiculata (Scop.) DC. (BM!-on blackthorn) also occurred, the former
covering "nearly an acre of ground profusely" "on the sand not far from the
cultivated fields", the latter "Extremely abundant ... on the sandy ridges"
(Holmes, 1878). The precise sites are unknown. These are all oceanic lichens
which are very sensitive to air pollution; at Dungeness they were on the edge of
their range. They became extinct probably early in the present century because
of the rise in background air pollution which occurred in south Kent, as
indicated by the spread of the pollution-tolerant lichen Lecanora conizaeoides Nyl.
ex Crombie on to Denge Beach.
Blackthorn is, of course, not the climax vegetation on the shingle. This is
considered, by some, to be holly, which still forms open scrub on Holmstone
Beach. About 300 ancient bushes, some well over 170 years old, remain, the
relics of a wood which "probably originated naturally before the eighth century
A.D." (Peterken & Hubbard, 1972: 571). The old word for holly is holm, and it
seems probable that the beach [Holmstone] was named after the holly wood
which covered it. A Saxon charter of c. 741 refers to a "wood called Ripp", ripae
meaning shingle banks, now the name of the beach [West Ripe] next to
Holmstone. In about 1539 Leland reported "Ther is a Place beyond Lydde, wher
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J. R. LAUNDON
as a great Numbre of Holme Trees groueth apon a Banke of baches throwen up
by the Se, and there they bat Fowle, and kil many Birdes” (Leland, 1744: 133).
Since this ancient woodland has never shown any signs of further development,
it could be regarded as the climax. I t is unique in Britain. A younger holly wood
(formed 1799-187 1) formerly occurred on Forelands Beach (Peterken &
Hubbard, 1972: 568). Only very isolated bushes occur on the other beaches, all
of which may have been planted. Peterken & Hubbard (1972: 568) consider that
sheep grazing either eliminated or prevented the establishment of holly
woodland on the eastern beaches in medieval times, where gorse scrub has long
formed a plagio-climax in disturbed areas.
Unfortunately, the lichen flora of the hollies on Holmstone Beach is not
remarkable. Lecanora conizaeoides and the green alga Desmoccoccus olivaceus (Pers. ex
Ach.) Laundon (Pleurococcus viridis (Agardh) Rabenh.) occur on live branches,
these being replaced by Lecanora expallens Ach. and scattered macrolichens, such
as Evernia prunastri, Parmelia sulcata Taylor, and Ramalina farinacea (L.) Ach., when
the branches are old and dead, and the leaves have been lost.
ARTIFICIAL SUBSTRATA
Artificial substrata are prominent in parts of Dungeness. Lichens are absent
from some, such as recent gravel pits and metal pylons, but are important on
others, such as concrete buildings and posts, and wooden fences. Some artificial
substrata are more important for lichens than for any other group of plants or
animals, but unfortunately they have not been studied in detail.
Several concrete bunkers are present as survivors from the Second World War
or have been built for use on the ranges. Concrete posts are used as supports for
wire fences. The concrete is often well-covered with common species of Caloplaca,
Candelariella, Lecanora, Physcia sensu lato, and Xanthoria. The most interesting
record is Caloplaca ruderum (Malbr.) Laundon, a species with a marked eastern
distribution in Britain (Laundon, 1986b: fig. 26). Small plants were frequent on
the concrete hemispherical hood of the ‘Listening Devices’ on eastern Denge
Beach in 1983. An account of the Listening Devices is given by Ingrams in
Godwin & Ingrams (1980: 151-152).
Wooden posts, bordering the tracks of disused railway lines, often have an
interesting lichen flora. Cyphelium inquinans (Sm.) Trevisan, Lecanora conizaeoides,
and Lecanora varia (Hoffm.) Ach. are all common on erect railway sleepers, which
form the posts of a fence on both sides of the disused railway on the south and
east sides of Lydd Airport. However, the most interesting lichens have been
found on fences further south. The most noteworthy of these is Lecidea insidiosa
Th. Fr., a lichenicolous lichen collected by Dr T. D. V. Swinscow from a railing
near Boulderwall on 4 March 1967 (BM!); this species grows on Lecanora varia,
killing the fungal partner and taking over the alga to become lichenized. It is
reported from only two other sites in the British Isles (Hawksworth, 1982: 385;
the quoted date of collecting is erroneous). Dr Swinscow also collected the
northern lichens Parmeliopsis aleurites (Ach.) Nyl. (BM!) and Pseudevernia furfuracea
(L.) Zopf (BM!) from other railings on the same date. I n contrast, the southern
lichen Parmelia soredians Nyl. was collected by P. W. James from a fence post near
Hamilton Farm, also on 4 March 1967 (BM!). Both chemotypes (BM!) of
LICHENS AT DUNGENESS
109
Pseudevernia furfuracea occur at Dungeness (Hawksworth & Chapman, 1971:
figs2, 3).
A few lichens occur on railway clinker. Stereocaulon vesuvianum Pers. was found
by P. W. James on clinker by Lydd-on-Sea Station in 1958 (BM!). This railway
line is now gone-like so much else at Dungeness.
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