23_237-252.pdf

Lichenologist 23(3): 237-252 (1991)
MICROCLIMATIC INFLUENCES ON LICHEN
DISTRIBUTION AND COMMUNITY
DEVELOPMENT
K. J. CANTERS*, H. SCHOLLERJ, S. OTT§ and H. M. JAHNS§
Abstract: The distribution of cryptogams and phanerogams and the microclimate
of different habitats have been studied. It is shown that a forest community of
phanerogams includes an assemblage of different microhabitats inhabited by different
lichens and mosses. The distribution of lichens and mosses is governed by factors
that are often of little importance to higher plants.
Introduction
Plant communities dominated by lichens and mosses are less well known than
those consisting mainly of phanerogams. The question whether cryptogams
should be treated together with higher plants in the same associations has often
been discussed. Arguments for a separate classification of cryptogamic
communities are the widely differing minimum areas for mosses, lichens,
herbs, shrub and trees and the entirely different microclimatic conditions for
diese layers of the vegetation (Barkman 1990). However, the whole vegetation
is connected in an ecological respect, which argues for a whole phytocoenosis
system. There is no simple solution to these problems but in this paper an
attempt is made to give some examples of the difficulties encountered in this
area of research. The observations described here will be published in much
more detail in other papers. They are used in this context for a broad and
general discussion of some interesting problems.
Methods
Methods for microclimatic measurements have been described in several papers (Schuster et al.
1982; Jahns & Ott 1983; Jahns & Fritzler 1982; Ott 1989). The details of mapping procedure etc.
will be given in other papers together with a more detailed account of the experiments and results.
For cluster analysis the' Tabord ' programme, developed by van der Maarel et al. (1979) was used.
Results
Plant distribution in a heterogenous forest area
The research area investigated was situated in the valley of the Wisper, a
tributary of the Rhine in the Taunus mountains. This tree-covered rocky spur
of the mountain has one side exposed to the north-east and covered by beech
forest and the other side faces south-west and is covered by open oak forest.
*Centrum voor Milieukunde, Rijksuniversiteit Leiden, Garenmarkt lb, 2311 PG Leiden, The
Netherlands.
JBotanisches Institut, Universitat Frankfurt, Siesmayerstr. 70, D-6000 Frankfurt, Germany.
§Botanisches Institut, Univeristat Diisseldorf, Universitatsstr. 1, D-4000 Diisseldorf, Germany.
0024-2829/91/030237+ 16 $03.00/0 © 1991 The British Lichen Society

238 THE LICHENOLOGIST Vol. 23
FIG. 1. Vegetation on a tree-covered spur of a mountain with a north-east facing slope (left part) and
a south-west facing slope (right part). Distribution of cluster-groups.
The vegetation was studied by cluster analysis and by principal component
analysis (PCA). Good correlations between the vegetation and the distribution
of abiotic factors such as light and pH were observed.
A cluster analysis of the complete research area showed several groupings
(Fig. 1, A-F) each representing homogeneous vegetation according to the rules
of plant sociology. The principal species in each group, higher plants as well as
lichens and mosses, and their abundance are given in Fig. 2. No lichens were
present (epiphytic lichens were excluded) in the cluster groups A and B from
the north-east facing slope. In group C the first species of Cladonia appear, but
only C.furcata is found with large numbers of thalli. The main occurrence of
Cladonia is in the cluster groups E and F, with a marked increase in Parmelia
conspersa and Polytrichum piliferum in cluster group F. This means that on the
southern-facing slope lichens and mosses could be used together with the
higher plants for the definition of the cluster groups.
A PCA of both slopes together included the cryptogams and resulted in a
clear picture. Only the occurrence of the plants and not their abundance was
used. The resulting scatter showed a gradient that could be separated into 10
parts (Fig. 3). The gradient shows a continuous change starting from the lower
part of the northern slope, passing upwards to the transition zone between the
two slopes and ending in three open areas at the margin of the south slope. A
comparison between PCA and cluster analysis shows a high degree of conformity.
The distribution of abiotic factors was also investigated by PCA and a
high degree of conformity between the distribution of vegetation and the light
intensity (Fig. 4), the pH and the ground cover by dead leaves was found.

1991 Microclimate influences on lichens—Canters et al. 239
Oxolis acetosella
IW.VJ
H * » * »1
Cardamine pratensis I.V.'.'.I
Mercurialis perennis
Anemone nemoroso
Lamiastrum galeobdolon
Dryopteris filix-mos
Festuca altissima r
Luzula luzuloides [•:•
Polypodium vulgare
I
Polytrichum formosum
Hypnum cupress i for me
Dicronum scopar/um
Avenella flexuosa
Clodonia furcato
Pleurozium schreberi
Fagus sylvatica (seedling)
Hierocium lacnenalii and H. glaucinum
Clodonia coniocraea
Cladonia orbusculo
Quercuspetraea (seedling)
Clodonia ciliota
Cladonia squamoso
Cladonio rangiferina
Dicronun spunurn
Calluna vulgarls
Hieracium umbellatum
Polytrichum piliferum
Genista pilosa
Parmelia conspersa
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240 THE LICHENOLOGIST Vol. 23
4 * 4 5
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FIG. 3. PCA of the occurrence of phanerogams and cryptogams on the mountain spur. The gradient
is divided into 10 parts and starts from the lower part of the northern slope and ends at the upper
margin of the south slope.
A separate PCA was made for the south-west exposed slope, which alone is of
interest for the cryptogams. Not only the distribution of clusters along the first
axis, but also the arrangement of individual species showed the same interesting
pattern. For example, Polypodium vulgare was found at one end of the axis and
Calluna vulgaris at the opposite end. Festuca cinerea occurs mainly in the
middle part of the axis. This corresponds with a light gradient from dark
{Polypodium) to light {Calluna). Of the cryptogams Polytrichum piliferum is
found at the end of the axis together with Calluna. For Cladonia a characteristic
distribution exists along the axis: all species occur in the middle part of the axis
and not at the extremes but C.furcata and C. squamosa are found nearer to the
darker part of the gradient and C. arbuscula and C. rangiferina in the lighter
areas.
This summary of the experiments shows that cryptogams can be included
with phanerogams in both cluster analysis and PCA, and that they contribute to
the study of the whole phytocoenosis. To summarize the results: Cladonia
(sect. Cladina) species are absent in the shady beech forest and in the open
sunny areas of the oak forest but dominate the rest of the oak forest. The
open oak forest contains an undergrowth of certain cryptogams, which can be
included in the sociological characteristics of the Quercetalia roboris-petraeae.
This statement does not answer the question whether, for lichens and mosses,
the open forest is a homogeneous area or an accumulation of completely
different microhabitats. Probably only the sum of these habitats together gives

1991 Microclimate influences on lichens—Canters et al. 241
-ss-
-50 SO too
180
X »0" a
FIG. 4. PCA of the light intensity (largest dots = highest intensity). The gradient shows the same
pattern as the PCA of the vegetation (see Fig. 3).
the impression of homogeneity. In this case the separated associations of
cryptogams are obscured by their inclusion into the description of the forest
community. To answer this question the scale of research must be reduced.
Lichen distribution in microhabitats in the forest
The tree-crowns of the open forest are responsible for variations in the light
intensity at ground level. Small 2 x 2 m plots were marked out at the border of
shadow areas in such a way that in summer there was a gradient from light,
warm and dry conditions at the lower left corner to dark, humid and cold
conditions at the upper right corner. The result should be a gradient of those
microclimatic factors that are most important to cryptogams. In winter, when
the trees are bare, the microclimate is more homogeneous. Therefore the differentiation
in the distribution of species must occur in the other months of the
year. The spatial distribution of microclimatic data was recorded for every hour
of the day; an example is given in Fig. 5. The microclimatic measurements were
combined in a gradient, which is shown in Fig. 6 for three plots.
The distribution of the plants was recorded in each quadrat including some
higher plants and the dominant lichens and mosses. For mapping, the 2 x 2 m
plots were divided into 400 small 10x10 cm quadrats. Figures 7 & 8 show the
distribution in two plots. The upper row contains the frequently occurring
plants common to all plots. The second row shows the distribution of frequently
occurring plants found only in one or two quadrats. The last row

242 THE LICHENOLOGIST Vol. 23
LOT
•
rel E 84 %
=100 = 68250 Lux
gOO
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1• =100=7000 Lux
K
7"
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8"
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13"
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rel. F 39 %
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14"
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• =100=50500 Lux
rel.E35%
FIG. 5. Distribution of microclimatic factors in the 2 x 2 m plots during the day. 1 = relative light
intensity (percentage of lightest spot), 2 = temperature (°C), 3 = vapour pressure deficit (mm Hg),
(*light intensity at lightest spot; rel.F. =rel. humidity).
contains the rare species. Species with a concentration in the lower left (light)
corner are placed in the left part of the figures, species with a preference for the
darker corner are situated to the right and plants without obvious preference in
the middle. Figure 7 shows that many species are concentrated in corners or at
one side of a quadrat. Examples are Polytrichum piliferum and P. formosum,

1991 Microclimate influences on lichens—Canters etal. 243
13
— —
9 \
I
•
I
J
I
1
14
10
1
1
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FIG. 6. Microclimatic gradients for direct gradient analysis in the 2 x 2 m plots, divided into 16
quadrats for mapping of vegetation. The quadrats are projected onto the gradients.
which occur in opposite corners. The same is more or less true for Cladonia
arbuscula and Dicranum scoparium. Avenella flexuosa seems to show a certain
preference for the right upper corner of the area. In Fig. 8 the quadrat shows a
concentration of P. piliferum and D. spurium in the left part and of P. formosum
in the upper part of the area. Among the rare species, Genista pilosa prefers the
left lower corner, Festuca cinerea the lower part and Luzula luzuloides the right
upper corner.
Of the total of 25 species, 12 occurred in all quadrats examined. A comparison
of these 12 species shows that:
(1) Some species (e.g. P. piliferum, C. portentosa) occurred in the left or the
left lower part (with more light).
(2) Some species (e.g. C.furcata, A. flexuosa, H. cupressiforme, D. scoparium,
P. formosum) were distributed in the right part or the upper right corner (darker
area).
(3) Some species (e.g. C. rangiferina, C. arbuscula, Pleurozium schreberi, C.
ciliata) showed no clear preferences.
The results were also examined by direct gradient analysis. The 2 x 2 m plots
were divided into 16 quadrats of 25 x 25 cm and the occurrence and abundance
of species were recorded. The quadrats were projected onto the microclimatic

Polytrichum
piliferum
Dicranum
spurium
Cladonia
portentosa
Cladonia
Pleurozium Melampyrum Cladonia
Dicranum Hypnum
arbuscu/a schreberi pratense ciliata scoporium cupressiforme
Cladonia
furcata
m
• "
• ' 3
Parmelia
conspersa
Hieraciun
pilosella
Hypogymnia
physodes
Calluna Quercus
vulgaris petraea
m Teucrium
scorodonic
Hieracium
um be IIa turn cf. Hieracium
lachenalii
Cladonia
cornuto
Cladonia
coccifera
Cladonia
pyxidata
Cladonia
sguamosa
Cladonia
g/auca
•
•
m
• 1
• i
1
Genista
pilosa
Festuca
cinerea
C/adonia
verticillata
Fagus
sylvatica
m m
Galeopsis
tetrahit
Cladonia
macilenta
Cladonia
gracilis
Cladonia Luzula
floerfteano luzuloides
m
•
FIG. 7.
Polytrichum
piliferum
Dicranum
spurium
Cladonia Cladonia Cladonia Pleurozium Melampyrum Cladonia Polytrichum Dicranum Hypnum Avenella Cladonia
portentosa rangiferina arbuscula
m
schreberi pratense ciliata scoparium cupressiforme flexuosa furcata
m
Hierocium
pilosella
Hypogymnia Caliuna Quercus Teucrium Hieracium Hieracium C/adonia C/adonia Cladonia Ciadonio Clodonia
physodes vulgaris petraea scorodonia umbellatum cf lachenalii cornuto coccifera pyxidata squamosa gtouco
i"'
Genista
pilosa
m
• •
m
a
Festuca Cladonia Fagus Galeopsis C/adonia Clodonia Cladonia Luzula
cinerea verticillatc sylvatica tetrahit macilenta gracilis fioerkeana luzuloides
•
7.* • \
FIG. 8.
FIGS 7 & 8. Distribution of species in two 2 x 2 m plots divided into 400 quadrats. Upper rows = frequently occurring species; middle rows = species frequent
but c ilv found in r fe 1 r r=
quadrats; Jo' x ro"
r 8 = r'
r
^ «•" "'is., -

1991 Microclimate influences on lichens—Canters et al.
Polytrichum pil/ferum
Cladonia ciliata
245
I 2 5 9 6 131014 3 7 II 15 4 8 12 16 I 2 5 9 6 13 10 143 7 II 15 4 8 12 14
FIG 9
FIGS 9—11. Abundance of species in quadrats 1—16 in the direct gradient analysis for three 2 x 2 m
plots. Warm and dry conditions to the left, dark and wet conditions to the right of every diagram.
gradients described above (Fig. 6), in order to compare the distribution of
species along the gradient. Figures 9-11 demonstrate the preference of certain
species for the light, warm end of the gradient while others prefer the darker
end. A third group seems to react indifferently. Among these is C. furcata, a
species that will be discussed separately (see below).
It is concluded that the distribution of lichens and mosses show characteristic
patterns on a very small scale. The same is apparently true for some
phanerogams.
Lichen distribution in microhabitats in an open area
In the open forest area the tree crowns are responsible for a distinct pattern of
light patches and a resulting microclimatic variation. For comparison an open

246 THE LICHENOLOGIST
Polytrichum piliferum
Cladonia ci/iata
Vol. 23
Cladonia portentosa
Cladonia furcata
60 - ^^
I 5 2 9 6 3 10 13 7 4 14 II 8 12 15 16
FIG. 10.
20
I I I I I I i i
5 2 9 6 3 10 13 7 4 14 II 8 12 15 16
area at the border of the forest was examined. This area was only 10x3 metres
but the distribution of cryptogams showed distinct patterns. A microclimatic
gradient from the trees to the open parts could be observed along which the
lichens showed distinct preferences. From the forest outwards the vegetation
was dominated by Polytrichum formosum, Cladonia arbuscula and C. rangiferina.
Towards the open parts followed in sequence C. portentosa, P. piliferum,
C. macilenta and C. floerkeana,and finally Baeomyces roseus and Pycnothelia
papillaria. Cladonia furcata again showed no clear preferences. The details of
these patterns and the behaviour of other species together with microclimatic
correlations will be discussed elsewhere.
The distribution patterns exist not only for species but also for groups
of species. It is possible to distinguish (Fig. 12) a Polytrichum formosum-
Cladina zone (1), a P. piliferum zone (2), a C. portentosa zone (3), a

1991 Microclimate influences on lichens—Canters et al.
247
Polytrichum piliferum
Cladonia ciliata
g, Cladonia rangiferina
5 2 9 6 3 10 13 7 4 14 II 8 12 15 16 I 5 2 9 6 3 10 13 7 4 14 II 8 12 15 16
FIG. 11.
C. portentosa-Baeomyces transition zone (4), a Baeomyces zone (5), a Grimmia
pulvinata zone (6), and other transition zones (7).
Microclimatic influences on lichen distribution and community
development
The last section again showed a separation of cryptogam vegetation into units
on a scale much too small for phanerogams. A joint treatment of both groups
would only serve to obscure the existing differences. If the distribution of
cryptogams is characterized by small areas, the influence of abiotic factors must
also be effective on a corresponding scale. In the first instance this means
microclimatic influences. Some of the decisive factors are also relevant to
ecological investigations of higher plants. However, often the distribution of

248 THE LICHENOLOGIST Vol.23
FIG. 12. Distribution pattern of species groups in an open area 1, Polytrichum formosum-Cladonia
(Sect. Cladina) zone; 2, P. piliferum zone; 3, C. portentosa zone; 4, C. portentosa-Baeomyces
transition zone; 5, Baeomyces zone; 6, Grimmia pulvinata zone; 7, other transition zones.
lichens can only be explained by factors that are irrelevant to higher plants or at
least different in their way of influencing the higher and lower vegetation.
The influence of many factors such as light, water relations and insolation
have been discussed in many papers. Some of these factors have already been
mentioned together with the examination of the forest area (see above). Here,
only some aspects will be reported that are often omitted.
The influence of dead leaves
The examination of small areas in the forest showed an influence of light and
temperature on the distribution of cryptogams. The occurrence of many
lichens showed a correlation with these factors and the real distribution
patterns of these species could only be explained by work on this microscale.
However, some species such as C.furcata seemed to be indifferent to light and
temperature. The climatic conditions on the lichen-free, north-east facing slope
should also be suitable for the species, but it does not occur there. This could be
due to the influence of dead leaves, which gather on this slope in a thick layer. To
test this hypothesis some transplantation experiments were carried out.
Thalli of several species of Cladonia were transplanted from the south slope
to the north slope. Each species was exposed on two 1 m 2 plots. One plot was
regularly cleared of all dead leaves (plot B) while from the other only sufficient
leaves were removed to prevent the lichens from being completely covered (plot
A). The condition of the lichens and their disintegration was classified with a
simple system. The development of the transplants is shown in Table 1.

1991 Microclimate influences on lichens—Canters etal. 249
TABLE 1. Condition of several transplanted Cladonia species
Date
16 September 1976
6 October 1976
22 November 1976
17 February 1977
31 March 1977
13 May 1977
6 July 1977
8 September 1977
13 December 1977
1 March 1978
C. rangiferina
A* B
_ +
—
—
-
—
—
-
0
0
C. arbuscula
A B
+
+ —
+ — —
+ -
+ —
+
+-_0
+ —
__
0
0 0
C. squamosa
A B
+
+
—
-
—
- 0
0
0
0
+
+
+
+
—
-
--0
0
C.furcata
A B
+ +
+ +
+ +
+ +
+ +
+ +
+ +
+ + +
+ + +
+ ++§
•Plot A with only a few leaves removed. Plot B regularly cleared of all dead leaves.
X + +, Very good (thallus upright without any disintegration); +, good (some small discoloured
parts); +, intermediate (discoloured parts and some spots with disintegration beginning; —, bad
(thallus partly dead and disappearing, some parts still left alive); , very bad (only some parts of
the thallus left, discoloured, broken down); 0, disappeared.
§Fertile thallus with apothecia.
The transplant experiment showed that for three of the four species the
microclimate of the north slope is unsuitable and the thalli degenerate. The
remaining dead leaves in plot A have an additional negative influence. On the
other hand C. furcata can, as expected, survive under these microclimatic
conditions only if the dead leaves are removed. In the completely leaf-free plot
B even apothecia were formed.
Dead leaves are therefore an extremely important factor for lichens in forest
communities. On the south slopes most leaves are blown away by the wind. The
remaining leaves do not lie on the cushions of Cladonia sect. Cladina species;
they slide down and gather between the cushions. The growth form of these
lichens therefore enhances their chances for survival in wooded areas.
The combined influence of wind and rain
The importance of some climatic factors can be understood only when they
are observed together. During research on the microclimate of lichen habitats
on an island in the North Sea the distribution of Physcia tenella on Sambucus
was recorded. It could be shown that the development depended on the water
relations, but that there existed no simple correlation with precipitation. The
really important influence was the wind from the sea, which in open locations
could direct the rain through the foliage to the trunk. In the lee of the dunes this
did not happen. The combination of exposure to wind with the rainfall was a
decisive factor for lichen occurrence.
Dewfall and 'dry nights '
Another example of an environmental influence often omitted is dewfall,
which is always important to lichens. In the course of a project, a transect

1991 Microclimate influences on lichens—Canters et al. 251
LI Lh Tl T2 L2Pr HR Ra Hu Wm Me Hs Wl Mb Hz Sa G2 Go W2 W4 NA HT la
FIG. 15. Key: H, Parmelia caperata; 0, Ochrolechia androgyna; •, Graphis scripta.
;
nz
i
n
i
n n n
M
n
i
i i i i 10
11Hi 6 H n c
' fa
J;
i
y Lin
Ml:
:j H H
• : w, ', ', ', ; > • •
LI Lh Tl T2 L2 Pr HR Ra Hu WmMe Hs Wl Mb Hz Sa G2 Go W2 W4 NA HT 2a
FIG. 16. Key: fS,Pseudeverniafurfuracea; 0, Platismatiaglauca; U,Cetrariachlorophylla.
through the valley of the Wisper from the Rhine valley to the Taunus mountains
was examined. The results of this study will be published in more detail
elsewhere (Scholler unpublished data). The Rhine valley is characterized by
warm, subcontinental summers and mild, sub-oceanic winters. The Wisper
valley is colder and the hills of the Taunus have a submontane climate. The
climate can be characterized by diagrams including factors such as rainfall and
humidity but in the usual form both are of little relevance to lichen vegetation.

252 THE LICHENOLOGIST Vol.23
It is better to count the number of nights without dewfall. In the narrow Wisper
valley dew accounts for one-tenth of the precipitation. Figure 13 shows along
the transect the number of dry nights during a 2-year period. It can be seen that
in the middle part of the valley hardly any night without dewfall occurred,
and this was the only part with an exceptionally rich lichen vegetation. The
parameter of dry nights and the distribution of lichen vegetation show a high
degree of conformity.
The study of an open oak forest showed the advantage of studying lichen
distribution on a microscale as opposed to the variations in higher plants on a
much larger scale. The distribution along the transect in the valley of the
Wisper deals with both groups of organisms on the same scale, but here again
the lichens give a much more detailed separation of vegetation zones. Naturally
not all lichen species react in the same way. Figure 14 shows that some species
occur in the lower part of the valley, whereas others (Fig. 15) grow in the middle
part and a third group are found in the upper hills (Fig. 16). Sometimes a lichen
species may be replaced by a closely related species along the transect. An
example of such a lichen pair with different microclimatic requirements is
Parmelia conspersa and P. somloensis. The picture is further complicated by the
fact that certain species seem to change their microclimatic requirements along
the transect. Cladonia arbuscula occurs in open localities in the middle part of
the valley and particularly in shady places in the warmer, lower parts. This is
the well-known law of relative habitat constancy. For lichens this law applies to
smaller areas than for higher plants.
Conclusions
The distribution of lichens is governed by microclimatic factors that influence
higher plants in different ways or not at all. The microclimate causes a separation
of much smaller units in cryptogams than in phanerogams. A joint treatment
of both types of plants in ecological investigations can sometimes obscure
the existing differences. On the other hand the description of a phytocoenosis
including cryptogams together with the higher plants may be of advantage in
some cases. However, it must be remembered that the lichens and mosses
inhabit special microhabitats and niches within the phytocoenosis. There
probably exists no general solution for these problems and the selection of a
suitable method must be governed by the nature of the problem.
REFERENCES
Barkman, J. J. (1990) Controversies and perspectives in plant ecology and vegetation science.
Phytocoenologia 18: 565-589.
Jahns, H. M. & Fritzler, E. (1982) Flechtenstandorte auf einer Blockhalde. Herzogia 6: 243-270.
Jahns, H. M. & Ott, S. (1983) Das Mikroklima dicht benachbarter Flechtenstandorte. Flora 173:
183-222.
Maarel, E. van der, Jansen, J. G. M. & Louppen, J. M. W. (1979) TABORD, a program for
structuring phytosociological tables. VegetatioiS: 143-156.
Ott, S. (1989) Standorte epiphytischer Flechten in einem Diinengebiet. Herzogia 8: 149-175.
Schuster, G., Herold, K. & Jahns, H. M. (1982) Mikroklimatische Messungen an Flechtenstandorten.
Neue Messapparaturen. Herzogia 6: 183-200.
Accepted for publication 27 April 1991