Fróðskaparrit - 01.01.1987, Side 87

The Ecology of Some Marine and Maritime
Lichens on Rocky Shores of the Faroe Islands
Anna Maria Fosaa
1. Introduction
This work was undertaken by the present
author in May 1986 during a survey of the
lichens of the Faroe Islands, in connection
with her thesis.
The lichen vegetation of the Faroe Is-
lands has previously been studied only on a
few occasions. The most well known of
these are Lindsay (1867), Deichmann
Branth (1901), Townrow (1960), Degelius
(1966), Hansen (1968), and Hansen and
Fosaa (1985).
Biologists working with the vegetation
on the seashore have been aware of the
phenomenon, that the lichens are growing
in belts of different colour. These belts
show the lichen zonation across the sea-
shore.
Lewis (1964) and Fletcher (1973) based
their seashore zonation studies of the
organisms on the seashores. Biologists
from the beginning of this century based
their studies on low and high tide, but later
other discovered that the theoretical bor-
ders were not similar to those observed,
since it is not only the tide that had influ-
ence on the zonation but also other physi-
cal factors. The composition of the popula-
tions on one shore is often different from
the composition of the populations on
another shore at the same level.
Lewis (1964) and Fletcher (1973) classi-
fied the shore as follows: -(1) the littorial
zone, that is the most marine influ-
enced.—(2) the supralittorale zone, which
is rarely submerged by the seawater and is
separated in three parts: one mesic-supra-
littorial zone nearest to the sea, one sub-
mesic supralittorial, and one xeric supra-
littorial zone farthest off water,—(3) the
terrestial region containing halophilic
species, that are species which tolerate the
seawater and species which do not tolerate
the seawater, respectively.
The survey below is a combination of the
system of Fletcher (1973) and Lewis
(1964). The terms used by Lewis are
identified by an asterisk. Fletcher (1973)
used by the species listed as an indicator for
the zones.
In this paper it will be discussed, whether
this classification system applies to the sea-
Fróðskaparrit 34.-35. bók (1986-87): 91-106