Lichen communities in the British Isles: A preliminary conspectus

364 P. W. James, D. L. Ilazpksworth and F. Rose
'Iasrn X_continued
Species Stand
V. glaucintt
V. hochstetteri
V. muralis
V. sphinctrina
V. airidula
-)- ',
1.2
_L)
J-.0
+.0
)- ')
_J- ')
-l?
-)_ )
+,0
-L)
+.0
1. '.)
-L?
+.0
+.2
1.2
t)
1. Sutherland, lnchnadamph, lowcr slopes of
transition between acid rock u"a ti-".ton.,
e 1961, r.w .J .
Ramsey (17 1992462): transition beru,ee n
exposed site, incl. + 10., aspect 270o,
.w.J.
ove Lochan an
st 1.970, p.W.J.
): exposed sitc,
Carsaig, near Nuns.pass (l 7/525205);
ust 1969, p.W.J.
, Great Close (44/90367g): smalt outcrop
, 0.5 x 0.5 m, 16 August 1967, p.\N.I:
centricae Mot. (Motyka, 1926, pp. 219, 226)
this nodum but this was poorly circumscribe.l
the non-British Leciclea'nioeiatra as a main
VI. Siliceous Rock Communities
have, with the notable exception
received scant attention in thc
ever, support more lichen species
ish Isles. While many communities
occur, problems of identification of
survey work undertaken mean that
ularly tentative.
t of these communities parallel
(see p. 304) with the ac{dition of
rdness and friabilitl, and (3) heavy
10. Lichen Communilies in the British Isles 365
In order to draw similar alliances and associations together, the siliceous
rock communities have been grouped into six broad habitat categories: (A)
shaded, (B) exposed, (C) nutrient-enriched, (D) mineral-rich, (E) marine
and maritime, and (F) aquatic.
All. 14. Leprarion chlorinae
A. Shaded
Leprarion chlorinae Smarda & Hadad, in Klika & Hadad, Pffuoda, Bnto 36,253
(1944).-Cystocoleion nigriWirth, Diss. Bot., Lehre 17,105 (1972).
An alliance of shaded underhangs and recesses in hard siliceous rocks
which are sheltered from direct rain; the acid rock counterpart of communities
in dry bark recesses (pp.306-313) and similar situations on
limestone (pp. 349-360). Crustose and leprose species predominate in this
alliance and many of hese are abundantly sorediate; indeed a high
proportion are unknown fertile.
A comprehensive key to the lichens of shaded acid rock crevices and
underhangs in Britain is provided by James (1970) and includes information
on the distribution of the species.
Some species-poor communities referable to this alliance are also able
to occur on upturned tree roots, soil, pebbles in roadside cuttings or in old
acid woodlands, as well as in the dry overhangs and recesses in rock of
which they are characteristic. The essentially corticolous Coniocybeturn
furfuraceae (p. 308) is also able to spread on to rock and dry soil in suitably
shaded sites and form intergrades with both the Lecideetum lucidae and the
L. syloicolae. The broad ecological amplitude of the Leprarietum incanae
(p. 312) includes siliceous rocks on which it can form transitions to the
Lecideetum lucidae and Racodietum rupestris in particular,
The Sclerophytetum circumscriptae of recesses in maritime rocks, u'hich
occupies comparable but more base-rich habitats than the Leprarion
chlorinae, is discussed separately below (pp. 387-388), while the heavymetal
requiring Lecanoretum epanorae, which also has an affinity for
dry crevices, is discussed on p. 383.
Mention should also be made here of a community of uncertain syntaxonomic
position which is currently poorly known and thus not recognizecl
formally here: the Lecidea phaeops-L. taylori nodum. This'is essentially a
community of damp overhangs oi .*pot.d rocks lvithin sheltered woodland
sites to which Gyalidea hyalinescens may also be faithful; that it requires
damp rocks indicates that it should be placed in an alliance othcr than the
Leprarion chlorinae and may perhaps be close to l\e Aspicilietum lacustris
(p. 3e1).