bryophytes and lichens of ancient atlantic oakwoods - Plantlife

LOWER PLANTS AND FUNGI PROJECT - TRAINING DAY
13 th and 15 th October 2009
BRYOPHYTES AND LICHENS
OF ANCIENT ATLANTIC OAKWOODS
INCLUDING IDENTIFICATION, ECOLOGY AND MANAGEMENT ADVICE
COURSE NOTES
By Andy Acton, Course Leader and Consultant Lichenologist
October 2009
General aims of the training day
The training will raise awareness of the importance of lichens in ancient Atlantic oakwoods,
including woods outside designated areas/sites (SACs, SSSIs etc.) as well as woods in
designated sites. Participants will be introduced to some typical lichens of these woodlands,
as well as gaining knowledge about the ecology and appropriate management techniques.
It is hoped that the day will generate useful woodland management discussion across the
disciplines represented by delegates.
What are lichens?
Lichens are dual organisms composed of a fungus and a green alga and/or cyanobacterium
(commonly known as a blue-green alga). The fungus (mycobiont) forms the body of the
lichen (the thallus). The alga/cyanobacterium (photobiont) manufactures food using the
energy of sunlight (photosynthesis).
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Growth forms
Lichen thalli have a variety of growth forms:
• Foliose (consisting of leafy lobes)
• Fruticose (shrubby, beard-like, and also special forms found in Cladonia lichens:
pixie-cups, soldiers and horn lichens)
• Squamulose (consisting of tiny lobes or scales)
• Crustose (crusty – consisting of thick porridge-like crusts or thin crusts that discolour
the substrate)
• Leprose (powdery lichens)
Figure 1: The foliose Green Satin Lichen (Lobaria virens), a conspicuous member of the
Lobarion lichen community
Figure 2: The fruticose Shrubby Beard Lichen (Usnea flammea)
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Figure 3: The squamulose Mealy-rimmed Shingle Lichen (Pannaria conoplea) is a
member of the Lobarion lichen community. In this example, the squamules (scales) are
visible at the margins of the thallus and the centre of the thallus is obscured by a dense crust
of vegetative propagules (soredia).
Figure 4: The crustose Cudbear Lichen (Ochrolechia androgyna) that looks like splats of
pale grey porridge on trees with acid bark is a typical member of the Parmelion lichen
community.
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Atlantic woodlands- our ‘Celtic’ rainforest
The climate of the Atlantic coastal fringes of Europe (Ireland, western Britain, small areas of
France, Spain, Portugal) and parts of Norway are heavily influenced by the North Atlantic
Drift (the Gulf Stream). These areas have much milder winters than the east coast of Britain
and other areas of Europe at the same latitudes. These mild winters, and our notoriously
wet weather, with abundant rainfall throughout the year, give ideal conditions for the
development of a diverse flora of ferns, lush carpets of bryophytes (mosses and liverworts),
and colourful assemblages of lichens that can give our ancient Atlantic woodlands the
character of a rainforest. This ‘temperate’ or Celtic rainforest supports many lichen and
bryophyte species that are largely confined to ancient or long established woodland. Many
of these species are absent in other parts of Britain and Europe, and some are globally rare.
Some species have their world headquarters in Britain and a few lichens have only ever
been recorded in Britain (endemic species), while yet others have odd distribution patterns
with a few widely scattered sites across the globe.
Although the following guidelines have been developed for Atlantic oakwoods, much of the
information, including the management recommendations, apply to other types of Atlantic
woodlands. All types of Atlantic woodland (i.e. all woods in the West Coast Scotland
Important Plant Area (IPA, for details see the Plantlife website) can be important for lichens.
Atlantic Woodlands are part of the coastal temperate rainforest biome. This biome has a
very restricted global distribution (Figure 5).
Figure 5: Global locations of temperate rainforest biome (in green) from Worrell (2009).
There are also small areas on the coasts of France, Spain and Portugal.
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Atlantic oakwoods
Atlantic oakwoods are a type of woodland in the west of the British Isles where oak forms a
significant component of the canopy. Other tree and shrub species may include birch, holly,
Rowan and Hazel. More locally, for example in flushed or wetter areas, there may be other
species such as alder, willow and sometimes some ash.
Relationship with NVC
Woodland types: Atlantic oakwoods are mostly W11 and/or W17, also often with significant
stands of W4 and locally sometimes W7, W9. Wet woodlands (W4, W7) can be good
habitats for epiphytic lichens and stands of W9 with ash and/or hazel can support particularly
important lichen assemblages.
Associated open ground habitats: Typically include acid grasslands (e.g. U4, U5),
bracken (U20), dry heaths (H10, H12, H21), wet heaths (M15), wet flushes and rush
pastures (M6, M23), mires (e.g. M25, M17) and rocky outcrops/boulders.
Types of Atlantic oakwood
The following types are largely adapted from some descriptions of Atlantic oakwood habitats
developed by Sandy Coppins as part of Scottish Natural Heritages programme of monitoring
woodland Sites of Special Scientific Interest (SSSIs) notified for their lichen interest.
1 Exposed, upland oak and oak-birch woodland
Description
Oak, oak-birch and birch in very exposed situations (e.g. exposed coastal stands) and/or on
very thin soils (e.g. over acid rock outcrops, or on steep, often rocky terrain). Trees are
generally stunted or have contorted growth forms. In very exposed stands the canopies can
be dense and compact, with distinctly wind-pruned shapes. Stands often grade into more
sheltered birch-oak or birch woods, where the stature of the trees gradually assumes more
normal growth form. These woods can be important for oceanic bryophytes where they
occur on slopes with a north or north-easterly aspect.
History
This oakwood type was traditionally used as sheltered grazing. It is unlikely that very
exposed scrubby forms with exposed stunted trees would have been intensively coppiced in
the past, so these scrubby woodlands may represent an ancient, relatively undisturbed
habitat.
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Figure 6: Exposed coastal oakwood near Glen Uig, Moidart, Lochaber © Andy Acton
Figure 7: Typical contorted oak in exposed coastal oak woodland © Andy Acton
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2 Relatively sheltered oak-birch woods with other tree/shrub species fairly frequent
(especially Hazel, Rowan, willow and holly) and more locally Alder, Ash.
Description
Deciduous woodlands in relatively sheltered situations e.g. on sheltered slopes, in wooded
valleys, along sheltered coastlines or associated with the undulating terrain of rocky
outcrops/knolls/ridges alternating with small, damp valleys (e.g. the parallel ridges, ‘cnaps’,
in Knapdale). Trees present can include oak, birch with some Rowan, Hazel and willow,
holly and more locally Alder, Ash. Mires or wet woodland types may be found in the hollows,
terraces and small valleys between knolls/ridges. This type of oakwood is not so obviously
even aged as ‘industrial’ oakwoods and often has many more overmature/veteran trees
(often including ‘phoenix’ trees). They also have a more diverse range of tree species).
History
This type of oakwood has typically been used as sheltered grazing and although most have
generally been subject to woodland management at some point in the past, the woodland
has not been managed as intensively as the ‘industrial’ oakwoods.
Figure 8: Relatively
sheltered mixed oak-birch
woodland at Dallachulish,
Glen Creran SSSI, Argyll.
© Anna Griffith.
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3 ‘Industrial’ oakwoods
Description
Woods dominated by even-aged oak. The understorey is sparse and other tree and shrub
species are often local (e.g. on wet ground, associated with very steep ground, ravines,
outcrops etc.).
History
Stands have been managed intensively in the past for charcoal, oak bark for tanning and
timber, and many are of plantation origin. There is often clear evidence of past woodland
management such as charcoal hearths, stone dykes or remnants of earth banks used to
exclude browsers, multi-stemmed oaks or evidence of former multi-stemmed trees that have
been singled or have self singled.
Figure 9: Even aged Atlantic Oakwood at Elleric, Glen Creran SSSI, Argyll © Andy Acton
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Lichens of Atlantic oakwoods
Most of the lichen species of conservation importance in Atlantic woodlands are associated
with three important lichen communities: the Lobarion pulmonariae community (usually
referred to as the Lobarion) on mildly acidic bark (Hazel, Ash, Elm, Rowan, willow, old oak),
the Parmelion laevigatae (hereafter shortened to Parmelion) on very acidic bark (oak, birch,
Alder), and these woods also provide a specialist habitat for the Graphidion scriptae
(hereafter Graphidion) best developed on the smooth bark of hazel stems (but also on rowan
and old hollies). All three communities can be found in Atlantic oakwoods.
The Lobarion - the ‘lungs of the forest’
This community includes some of our most conspicuous species of epiphytic lichens
(epiphytic lichens are those that typically grow on trees and shrubs). One of the most
characteristic species of this community is the Tree Lungwort (Lobaria pulmonaria). This
very distinctive species with its surface network of ridges resembles green lungs hanging
from the trees.
Well-developed Lobarion communities can include good populations of a number of species
that are rare elsewhere in Europe, and largely confined in Britain to ancient woodland or
parkland. Well developed Lobarion communities will usually have a diverse range of species
including several Lobaria species, 'stinky' Sticta species (that smell fishy when wet), jelly
lichens (Collema and Leptogium species), felt lichens (Degelia species), shingle lichens
(Pannaria and Fuscopannaria species) and dog lichens (Peltigera species).
The Lobarion interest on the even-aged oak trees of the ‘industrial’ oakwoods can at first
glance appear be poor compared to other types. However, some trees may still support
scarce and threatened Lobarion species and unusually good populations of some other
specialist lichens such as the Nationally Scarce species Smokey Joe (Opegrapha fumosa)
and the Nationally Scarce Porina coralloidea (a crustose lichen). Individual trees and
woodland habitats pre-dating the even-aged ‘industrial’ stands are very important in
otherwise even-aged oakwoods e.g. open grown veteran pasture or boundary trees, other
old trees and shrubs (e.g. Hazel, Rowan, birch, Alder, holly) and areas that have not been
planted with oak such as riparian areas, very steep rocky terrain, outcrops, very wet ground.
In general the more uneven the topography, and the more trees and woodland habitats
present that predate the 'even-aged ‘industrial’ oaks, the greater the chance that the evenaged
trees will have developed or will in time develop a rich lichen flora.
The Parmelion: grey lobes and whitish crusts on acid bark
Trees with very acidic bark (birch, alder and oak) and sheltered rocks can support leafy
lichens with small pale greyish leafy lobes, shrubby pale greyish ‘coral’ lichens and thick
whitish crust-like ’cudbear’ lichens of the Parmelion laevigatae. When well-developed this
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Parmelion community can include a number of notable lichens including scarce and endemic
species.
The Graphidion (‘smoothies’) on smooth bark
Hazel in Atlantic woodlands is important because, as well as being one of the best hosts for
Lobarion lichens, its smooth stems support a specialist hyperoceanic form of the Graphidion
community that is globally very rare. Many Atlantic woodlands in western Scotland with
significant stands of hazel support a well developed Graphidion with some specialist
hyperoceanic species. The hazel in Scotland is so good for lichens because it has not been
so intensively managed as in other parts of Britain (e.g. in England where it was often
coppiced on a rotational basis).
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Indicators of high quality epiphytic lichen habitats
Indicators of high quality Lobarion communities
The presence of a range of leafy lobes and scaly patches of green, brown, blackish and
slate grey Lobarion lichens indicates a well-developed Lobarion community. The presence
of several of the Lobarion community species illustrated in Acton & Griffith (2008a) may
indicate that a woodland could have a Lobarion community of conservation importance.
Particularly good indicators of Lobarion communities of high conservation importance
include:
• Specklebelly lichens e.g. Norwegian Specklebelly (Pseudocyphellaria norvegica)
(Figures 21, 22, Appendix I), and Golden Specklebelly P. crocata (Figure 26,
Appendix II)
• Shingle lichens e.g. Brown Shingle Lichen (Fuscopannaria sampaiana) (Figures 23,
24, Appendix I).
• Jelly lichens Collema and Leptogium species (e.g. see Acton & Griffith, 2008a)
However, Lobarion communities of conservation importance may not have any of the above
species.
Figure 10: A typical Lobarion
community with the conspicuous
green leafy Tree Lungwort
(Lobaria pulmonaria), grey lobes
of ‘Lob scrob’ (Lobaria
scrobiculata) and the brown
lobes of Floury Sticta (Sticta
limbata) © Andy Acton
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Indicators of high quality Parmelion communities
The presence of a range of pale grey leafy, coral-like and crustose Parmelion lichens
indicates a well-developed Parmelion community (Figure 11). The presence of several of
the Parmelion community species illustrated in Acton & Griffith (2008b) may indicate that a
woodland could have a Parmelion community of conservation importance.
Particularly good indicators of Parmelion communities of high conservation importance
include:
• Loop lichens e.g. Hypotrachyna laevigata (Figure 27, Appendix II) and H.
taylorensis (Figure 28, Appendix II)
• Coral lichens Sphaerophorus globosus (Figure 29, Appendix II) and Black Eyed
Susan (Bunodophoron melanocarpum) (Figure 30, Appendix II)
• Tree Flute (Menegazzia terebrata) (Figure 31, Appendix II)
•
Fig. 11: A well-developed Parmelion community on oak. The presence of the community is
indicated by thick whitish, porridge-like crusts (cudbear lichens) and pale grey leafy lobes
© AndyActon
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Indicators of high quality Graphidion communities
It is extremely difficult to identify a well-developed Graphidion community based on a list of
indicator species because identification of most of the species requires the expertise of a
lichenologist. The presence of a patchwork of fawn, brownish, pale grey, whitish or orange
patches with minute spots, pimples, warts and scribbles on the smooth bark of species such
as hazel, may indicate that a woodland could have a Graphidion community of conservation
importance. However, this patchwork is often only apparent on very close examination of
stems and is very easily overlooked by non-lichenologists. Only an experienced
lichenologist can make a definitive assessment, and in the absence of specialist
assessment, it should be assumed that any stands of hazel in western Scotland may
be of high importance for Graphidion lichens.
Most Graphidion species are difficult to identify and many require microscopic examination,
but two species that can be identified once they have been pointed out include one that
forms thin whitish crusts with distinctive barnacle-like fruits on smooth hazel stems and
another that forms small orange patches with black pimple-like fruits on hazel stems:
• Barnacle Lichen (Thelotrema lepadinum) (Figure 32, Appendix II)
• Orange Pox Lichen (Pyrenula occidentalis) (Figure 33, Appendix II)
Fig. 12: Typical Graphidion
community on the smooth bark of
hazel with a patchwork of raised,
barnacle-like fruits of the Barnacle
Lichen (Thelotrema lepadinum),
and script lichens with tiny black
elongated fruits like Arabic script.
Much less obvious are the pale
fawn patches with fruits that look
like very tiny black dots under a
hand lens. © Andy Acton.
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Why do Atlantic woodland lichens need to be protected?
Very high quality lichen habitats have a very restricted distribution in Britain and many
habitats are fragmented. Although some parts of Western Scotland have extensive stands
of Atlantic woodland, in many areas these are a fragment of what they once were. In the
past high quality lichen habitats have been lost to farmland/pasture (past woodland
clearance and overgrazing), conifer plantation, Rhododendron, and woodland management
(timber, fuel, ‘industrial’ oak plantation, coppice for tanbark/charcoal etc.) More recent
threats include continued loss due to over-grazing and, paradoxically, in some cases loss
due to dense thickets of natural regeneration (leading to reduction/loss of suitable lichen
habitat).
Lichen are very slow to colonise new habitat and once lichen habitats are lost due to habitats
loss/disturbance/inappropriate management – lichens may never recover. Thus the priority
should be to prevent loss/damage to what remains, with expansion of habitat only
appropriate where this does not compromise existing high quality habitat.
Species of conservation importance
A large number of species of conservation importance are strongly associated with or found
within Atlantic woodlands including Atlantic oakwoods. These include:
Schedule 8 species
• ‘Blackberries in custard’ (Pyrenula hibernica) (on hazel in Atlantic valley/ravine
woodlands). (See Figure 34, Appendix II)
• Fuscopannaria ignobilis, a shingle lichen: (on ash, oak and elm).
• Tree Lungwort (Lobaria pulmonaria) (on a wide range of trees including ash, hazel,
oak, and rowan. This species has recently been included on Schedule 8 in order to
control any collection for commercial purposes). (See Figure 36, Appendix I)
Nationally Scarce, Rare, BAP and Scottish Biodiversity List species
A large number of Nationally Scarce, Nationally Rare, Biodiversity Action Plan (BAP) and
Scottish Biodiversity List (SBL) species are strongly associated or found within Atlantic
Woodlands, including Atlantic Oakwoods.
Species for which we have International responsibilities
Our Atlantic woodlands support a significant proportion of the European and/or global
populations of 86 lichen species for which the UK has international responsibility, and a few
of these species are endemic (i.e. only known from Britain).
Woods & Coppins (in prep) gives further details on lichen species of conservation
importance.
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ECOLOGICAL REQUIREMENTS FOR RICH ATLANTIC LICHEN FLORAS
Lichens
Areas of ancient woodland i.e.
areas that have escaped intensive
management (including more inaccessible
stands of trees within woodlands that have
generally been more intensively managed.
For example, trees in wet areas, ravines or on
steep rocky slopes).
Light/temperature
Exposure/humidity
Variety of microhabitats/niches
Some of the best areas for lichens have been subject to a history of non-intensive management (e.g.
ancient woodland pasture). Sheltered oak-birch woods on uneven topography are often the most diverse
and likely to be the most interesting for lichens, but other oakwood types can still be very important where
they are associated with other woodland habitats (Ash, Hazel, wet woods). Woodland habitats and veteran
trees pre-dating the even-aged ‘industrial’ stands are particularly important in even-aged oakwoods.
Woodland habitat networks: adjacent areas of old woodland can be important sources for colonisation of
younger woodlands as trees age and develop suitable bark characteristics for a range of different lichen
species.
Well lit to moderately shaded. Very heavily shaded sites tend to be dominated by bryophytes but some
important lichen interest may still be present. Trees in very windy and exposed situations tend to be poorer
due to lower humidity levels. Woodlands with high lichen interest often include well lit but relatively
sheltered, humid habitats (e.g. glades) as well as moderately shaded, very humid habitats.
Moderate to high humidity. Some epiphytic lichen (e.g. those of the Lobarion) thrive in very humid
environments, but others prefer less humid conditions.
Most of the lichen interest is likely to occur on trees but additional habitats that can be locally important
include boulders and rocky outcrops.
A range of tree/shrub species and ages (including moribund/dead trees) provide a range of micro habitats
including rough and smooth bark, sheltered or exposed bark, very acidic bark (e.g. oak, birch, Alder) and
trees/shrubs with less strongly acidic bark (e.g. Ash, Hazel, Elm, Rowan, willow, old oak).
Veteran trees and old hazels can be particularly good for lichens. Branches and twigs also provide
additional niches for lichens.
Riparian woodland, wooded valleys and ravines with Ash, Alder, willow, and Hazel can be particularly
important. Also areas of wet woodland with birch, Alder, willow.
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Important woodland features influencing the abundance and
diversity of Atlantic lichens
Diversity of tree and shrub species and ages
Different tree and shrub species have different bark characteristics, and these characteristics
alter as a tree matures. A range of tree and shrub species that are young-mature to
overmature ensures a range of bark conditions. Saplings and very young trees are generally
of low importance for lichens and very dense regeneration can pose a shade threat to
notable lichens (see below) but some saplings and young trees are desirable to provide
future habitat and add to overall biodiversity because they provide a niche for earlycolonising
species. If Hazel is present, a range of stem sizes is desirable as smooth Hazel
stems provide important habitat for a range of highly specialist Atlantic lichens.
Diverse woodland structure
The best woods for lichens and bryophytes often have a diverse woodland structure that
includes areas with a closed canopy, dappled shade, glades, a patchy understorey
including Hazel, some denser stands of Hazel, standing and fallen deadwood, veteran
trees. These conditions provide a diversity of light/shade regimes and variation in humidity
giving a variety of niches for both bryophytes and lichens.
Old and veteran trees
These act as an important refuge for a variety of species as they often have a variety of
micro-habitats. Some may be relict trees from former pastoral systems (old, open grown
ancient pasture trees). They can also provide deadwood habitat. Large stools of Hazel
can be particularly important for lichens and bryophytes. Large trees along margins of an
otherwise shaded wood (e.g. boundary trees, wayside trees) can be important for more
light-demanding species of lichen, though the open habitat generally means that these
boundary/wayside trees are less important for oceanic bryophytes.
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Figure 13: Veteran oak within Conifer Plantation at Glencripesdale NNR, Sunart SSSI
© Andy Acton
Less intensively managed woodland habitats
Wet woods, riparian woods, valley woodland and ravines, and woodland on steep,
rocky terrain have often been less intensively managed in the past and can support a
greater diversity of tree and shrub species and therefore can be important areas for lichens
and bryophytes. In long established plantation oakwood, such stands are particularly
important as many tree and shrub species and their associated lichen and bryophyte flora
may be confined to them. These can be an important source for colonisation as the
woodland matures.
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Figure 14: Wet birch woodland on flat terraces above the River Avich; birchwoods such as
this may initially be viewed as of low conservation importance but they can support high
lichen interest. © Andy Acton
Diverse topography: including valleys, ravines, rock outcrops
Variation in topography results in a range of woodland habitats with a diversity of light and
humidity regimes which will ensure the optimum conditions for a range of lower plants and
thus give a diverse flora. Aspect can be important; for example well-lit, south-facing slopes
will have a different flora to shadier north-facing slopes. Particularly important topographical
features in Atlantic woodlands include river valleys and ravines, rocky outcrops, flushed
slopes, flat terraces, boulders, rocky slopes, boulder screes.
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Rock outcrops and boulders
These habitats are of overwhelming importance for oceanic bryophytes and provide habitat
for saxicolous lichens. These habitats are so important because of the lack of competition
by other, more robust woodland floor species and the cycle of accumulation of plants on the
rock-face and subsequent sloughing off provides a steady supply of new, open habitat for
the smaller species.
Potential threats
Rhododendron
Dense Rhododendron casts a very heavy shade that is disastrous for any existing lichen or
bryophyte interest. R. ponticum is one of the major threats to Atlantic lichens and
bryophytes in western Scotland.
Figure 15: Rhododendron bushes cast heavy shade over the woodland floor and lower
trunks of trees © Anna Griffith
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Figure 16: Woodland after removal of Rhododendron clearly showing the effect of dense
shade on the woodland floor and tree trunks © Anna Griffith
Clearfelling/rotational coppice
Large scale felling and rotational coppicing within Atlantic woodlands will seriously damage
any lichen and bryophyte interest and should be avoided. If a crop is desired (e.g. for wood
fuel), it would be far preferable to thin dense thickets of recently established trees (e.g.
birch).
Hazel is one of the most important species in Atlantic woodlands for lichens. Hazel is
naturally multi-stemmed and therefore it should not be assumed that multi-stemmed stools
indicate ex-Hazel coppice. It is a common misconception that Hazel requires coppicing.
Although Hazel was cut in the past, in the Atlantic woodlands of western Scotland this has
generally not been done on an intensive, rotational basis. This is why Hazel in Scottish
Atlantic woodlands is so good for lichens. Any Atlantic Hazel stand that is important for
lichens and which has been subject to past cutting, is important despite any cutting, and not
because of any cutting.
Thinning operations and small scale coppicing (e.g. for wood fuel)
Although these forms of less intensive woodland management are preferable to large-scale
operations, there is still the risk that stems or trees with high lichen or bryophyte interest
could be inadvertently removed.
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Figure 17: Recently coppiced Hazel stand, Sutherland © Anna Griffith
Figure 18: A coppiced Hazel stool
where all stems have been removed,
and upon which were growing the
European Red List, Nationally Scarce
and BAP species Norwegian
Specklebelly (Pseudocyphellaria
norvegica). Many epiphytic lichens
are extremely slow to colonise and
spread, and require bark with specific
characteristics such as pH (related to
tree species and tree age), and bark
structure (smooth, rough, dry, damp –
related to tree species and age, microhabitat).
Once the stems have been
removed, the lichens will persist for a
short while, but will die as the wood
rots. Any dramatic loss of humidity is
also likely to have and adverse affect
on any lichens (and bryophytes) that
remain on rocks and adjacent trees.
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Scrub clearance
The clearance of ‘scrubby’ woods of birch, willow and Hazel may be a threat to very
important habitats for lichens and bryophytes. Wet woods of birch and willow may be
important habitats for Parmelion lichens and epiphytic oceanic bryophytes. Hazel in western
Scotland can be of international importance for Lobarion and Graphidion lichens and for the
Lejeunea liverwort community.
Continued long term overgrazing of moribund woods, woodland fragmentation and
loss
Very long term overgrazing can eventually lead to decline in canopy and decline in diversity
of tree species (e.g. old trees of palatable species with a relatively short life span such as
rowan may disappear). Continued long-term overgrazing prevents woodland regeneration
and ultimately lead to loss of woodland cover and fragmentation, which are major threats to
lichens and bryophytes.
However, it is important to note that woodlands can survive relatively long periods of heavy
grazing and old pasture woodlands are some of the best habitats for lichens. Provided the
continued presence of old trees of the full range of tree species is assured in the long term,
undergrazing can be more of a threat to lichen habitats than overgrazing. However, whilst
some canopy loss may not be a direct threat to lichens, any general opening up of the
canopy will be unfavourable for oceanic bryophytes unless the sites are very rocky or have a
northerly aspect.
Figure 19. Moribund Hazel wood on Skye where long-term over-grazing has prevented the
successful recruitment of new shoots to stems and thus led to the development of tree-form
Hazels © Anna Griffith
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Undergrazing: due to decline in domestic stocking levels or stock exclusion
Well-intentioned woodland regeneration schemes involving the erection of stock and/or deer
fencing can be a potential threat to lichens. The aim should be to restore woodland habitat
not simply increase tree cover in the landscape. Widespread dense thickets of native and
non-native species (including birch, holly, Sycamore, beech, Sitka Spruce) may pose a
shade threat to lichen and bryophyte assemblages on trees and rocks. Infilling of gladed
areas by thickets of natural tree regeneration threatens range of habitats (species-rich
grassland, flushes, mires etc.) and may reduce available habitat for a number of notable
lichens that prefer well lit conditions. Particularly at risk are some of the Lobarion species on
old trees and on Hazel, especially those associated with glades, along woodland edges or
waysides. Unhindered thicket regeneration of just one or a few vigorous species will lead to
long term decline in woodland composition and structure and consequent loss of
biodiversity. In addition, the spread of ivy, and even in extreme case honeysuckle, when
unhindered by browsing, can smother trunks of trees, rocky outcrops, boulders etc. and
reduce available habitat for lichens and bryophytes. The main problem for bryophytes within
exclosures is the growth of a coarse herb and dwarf shrub layer which can completely cover
important communities on rocks and tree bases and these coarse plants can also produce
much litter which can accumulate and similarly smother low rocks and change the character
of flushes.
The decline in low-intensity livestock farming accompanied by the continued decline in
stocking levels may lead to expansion of our Atlantic woodlands. However, the rapid infilling
of glades and shading of old/veteran trees and trees along woodland edges may be a major
threat to lichen flora of Atlantic woodlands. Grazing by stock and deer may need to be
considered as a conservation management tool in these situations.
Figure 20: This exclosure has been
functional for over 30 years. Inside
extremely dense birch regeneration has
established that has infilled glades,
outcompeted any seedlings of other tree
species and cast dense shade on trunks of
previously open-grown, well-lit mature trees.
© Anna Griffith
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Developments: windfarms, hydro schemes, road improvements etc.
Any tree felling and canopy loss can reduce humidity levels and lead to direct loss of
epiphytes (especially bryophytes, but also those lichens that require more humid conditions
such as jelly lichens). Ground disturbance may also directly threaten bryophytes (e.g. those
on boulders) and may adversely affect hydrological regimes (and may thus affect humidity).
In addition to the threats from infrastructure (pipeline routes, accesses etc), hydro-electric
power schemes pose additional threats through their impact on hydrology. There is a direct
impact on those species growing on rock in the water channel but there may also be
changes in the humidity regime in the woodland as flow rates are reduced over the length of
river affected.
Potential conflicts between management practices for lichens and
bryophytes
Oceanic bryophytes are more susceptible to desiccation than many lichens. A policy of
opening up glades for the lichen interest in a woodland may be beneficial for lichens if it
avoids felling trees with high lichen interest but this practice has the potential to damage the
bryophyte interest. Lichens are more threatened by heavy shading than bryophytes; so a
policy of ‘filling in’ the canopy to increase humidity levels for bryophytes may pose a shade
threat to valuable lichen communities.
In either situation, it would be wise to assess the lichen and bryophyte floras in order to
minimise potential negative impacts. One thing is clear, very heavy shade dramatically
reduces the diversity of both lichens and bryophytes and should be avoided.
Management for other woodland features - complementary
management and potential conflicts
• Grazing and browsing
Grazing and browsing by stock and deer can be fully compatible with management
for lichens and bryophytes. Domestic stock or deer can be important conservation
management tools. Grazing levels can be manipulated to, for example expose a
suitable seed bed for tree seedlings, permit and control levels of tree regeneration
(and hence determine future woodland structure) and to maintain woodland glades.
Grazing can to used to maintain a species-rich sward and, especially in the case of
cattle, can be used to control rank vegetation and maintain a variable sward height
(e.g. for invertebrates, woodland ground flora).
24

• Other woodland flora and fauna
Management of woodland for lower plants is compatible with management for fungi,
butterflies, other invertebrates, bats, birds and vascular plants. Management for bats
involves retention of old/veteran trees and gladed areas, including open ground along
woodland edges; these aims are fully compatible with the lichen interest. Butterflies
associated with woodland habitats are, like many well-developed lichen communities,
reliant on the presence of gladed conditions. Generally, management for woodland
butterflies associated with woodland habitats (grazing to control scrub invasion of
glades and clearing by hand) is beneficial for lichens as it keeps glades open.
However, such management should be confined to restoring glades that are known
to have only recently infilled, and in situations where new glades are not naturally
opening up to replace those that are infilling.
25

Woodland Management Recommendations
The expansion and linking of areas of broadleaf woodland is the best policy for ensuring a
bright future for oceanic lichens and bryophytes. However, as many Atlantic lichens and
bryophytes are inconspicuous they have frequently been neglected in the past when
decisions have been made on site management. Today, the profile of lichens and
bryophytes has been raised but it is still easy to overlook them when it comes to making
decisions on site management. Even when their importance on a site is recognised, it is
often assumed that if we ensure continuity of large scale habitat (woodland) the lower plants
will look after themselves. However, there are potentially serious implications of this
approach due to the possible conflicts between management purely for woodland features
(e.g. the encouragement of inappropriate levels of tree regeneration may threaten lichen
interest on old trees/shrubs). So management should specifically consider the needs of
lichens and bryophytes, to enable populations and communities to persist and thrive, whilst
potential lichen and bryophyte habitat is expanded. Many of these recommendations will
benefit other woodland species and encourage a diversity of woodland structure and tree
composition. Some general guidelines are given below.
• Woodland expansion and woodland habitat networks
Woodland loss and fragmentation has historically been the major threat to lichens
and bryophytes and in many areas, fragmentation of suitable habitat is still a threat.
Woodland expansion and the establishment of woodland habitat networks is
important for the long term continuity and diversity of the lichen and bryophyte
communities. Woodland expansion should be encouraged beyond the boundaries of
existing woodlands, to link up existing fragments of old woodland. Extensive, dense
tree regeneration within the boundary of existing woodland should be avoided in
areas with high lichen interest. In some woods, only relatively low recruitment rates
may be necessary for woodland continuity.
• Eradicate Rhododendron
All Rhododendron ponticum should be eradicated from Atlantic woodlands and any
other habitats in the vicinity.
• A general principle
A general principle would be to manage to ensure continued presence of a range of
tree/shrub species and ages (including moribund/dead trees) and provide a range of
micro-habitats including rough and smooth bark, sheltered or exposed bark, very
26

acidic bark (e.g. oak, birch, alder) and trees/shrubs with less strongly acidic bark (e.g.
Ash, Hazel, Elm, willow, old oak).
• Retain old and veteran trees
This should ensure that trees with high lichen and/or bryophyte interest are not felled
(and thus retained as important habitat).
• Leave all dead wood on site
Dead wood is an important habitat for bryophytes and lichens as well as fungi and
invertebrates.
• Moderate coppicing of stands of Hazel
As a general rule, when wanting to carry out cropping of Hazel in Atlantic woods,
complete coppicing of the stool is to be avoided, as all lichens and bryophytes
(specialist as well as common species) get taken away with the cut product, and
those specialist species are very poor colonisers and therefore unlikely ever to return.
For hazel, the recommendation is always to carry out very small-scale selective
cutting of individual stems as required (thatching spars, pea-sticks, walking sticks,
etc.), as this allows the overall integrity of the stool to remain fairly intact, and so a
greater chance that the associated lichens and bryophytes remain as part of habitat.
Any larger scale operations should be restricted to hazel stands established purely
for that purpose.
• Sensitive woodland thinning operations
Lichen assemblages on trees can generally tolerate some thinning operations
Thinning may be beneficial where dense thickets of regeneration are posing a threat
to established lichen-rich habitats. Small-scale thinning in even aged woods (e.g. of
‘industrial’ oakwoods for timber) can be used to also diversify woodland structure
(e.g. patchy thinning to create small glades) and thus diversify lichen habitat.
However, carrying out this practice on a rotational basis is likely to be damaging, as
many of the more important species are slow colonisers with more specific habitat
niche requirements.
Small-scale cutting/coppicing of recently-established birch would come into this
category, though ideally grazing should be used to control re-growth. If wanting to
coppice birch regularly (say for wood fuel), then ‘new’ stands are best to utilize, rather
than in-fill in established Atlantic woods; regular fluctuation of light/shade conditions
27

around established lichen or bryophyte-rich trunks will lead to a rapid decline in these
communities, unable to tolerate such rapid habitat changes.
Specialist lichen and bryophyte surveys are strongly recommended prior to any
thinning/coppice operations in Atlantic woods to identify areas suitable/ unsuitable for
these operations, including marking up any individual trees or shrubs that should be
retained.
• Felling of commercial conifer plantations
Large scale felling operations can lead to a dramatic reduction in humidity levels in
adjacent broadleaf woodland leading to the desiccation, and potential loss of some
bryophytes and lichens. With larger stands of broadleaf woodland, this is only likely
to affect the edge, and is unlikely to significantly affect the lichen and bryophyte
communities. However, the lichens and bryophytes associated with smaller stand of
trees within conifer plantations may be more vulnerable, especially narrow strips of
riparian woodland. If there are any particularly rare and important lichen species
present (highly likely in the case of ravines), specialist advice should be sought on
how to minimise impacts.
• Avoid disturbance to areas of wet woodland
Including areas of scrubby birch and willow – such scrubby areas are often
dismissed as of low conservation interest but may be important habitats for lichens
and bryophytes.
• Avoid disturbance to areas of riparian woodland
• Avoid long term exclusion of all grazing from woodland
Some level of grazing is generally desirable but prescribing a fixed grazing level is
not always possible. The level (seasonality and the number and type of grazing
animals – cattle, sheep, ponies, etc.,) should be flexible and determined by the
fluctuating condition of a site and seasonality (wet summers, or long dry summers,
etc.). Grazing as a management tool should focus on ensuring continuation within
the site of various features – veteran trees, woodland regeneration, lichens,
bryophytes, invertebrates etc. High grazing levels may be retained for long periods
provided woodland continuity is assured in the long term. Sustained periods of very
low grazing levels can be a serious threat to a diverse woodland structure, glades,
flushes and species-rich grassland. Temporary low grazing levels (or temporary
enclosure) can allow a flush of regeneration and ensure woodland continuity in the
long term. Woodland regeneration exclosures should be viewed as temporary
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measures. If left up for too long they may permit undesirable thickets of dense
regeneration to become widespread (see below).
• Control growth of dense thickets of tree regeneration in areas with high lichen
interest
Extensive, dense thickets of tree regeneration (often of birch or non-native conifers
but also Rowan, holly Ash, Beech and Sycamore) can pose a shade threat in
woodlands or to individual trees with high lichen interest (e.g. regeneration within
open woodlands or along woodland edges with old trees, surrounding old boundary
trees, old trees or shrubs along the margins of woodland glades, any open grown
veterans). Cattle or deer could control the formation of dense thickets if introduced
early enough, otherwise hand cutting might be necessary before stock/deer can have
any significant impact. Some species and/or growth stages may not be selected by
certain animals, so advice may need to be sought as to which grazing animals will
target particular areas with problem regeneration. Do not allow extensive dense
regeneration along well-lit woodland edges if the trees along these edges support
well-developed lichen communities.
• Adopt and ‘egg-and-basket‘ approach – consider smaller, temporary
exclosures
Don’t put all your eggs in one basket. Patchiness is good - e.g. variability in size and
successfulness of stands of regeneration. Ensure a variety of shade, light and
humidity – e.g. if erecting a deer fence don’t use it to exclude all stock/deer from the
whole woodland for a long period. Fencing should only be seen as a temporary
measure. Smaller exclosures, exclosures with gates to allow grazing animals
controlled entry or ‘leaky’ fences (where stock can periodically gain access for a
limited time) may help to ensure a more varied woodland structure develops. This
would need careful monitoring to ensure that the regeneration of more palatable
species is not affected, leading to a reduction in diversity of tree species.
• Tree planting
Planting should be considered if diversity of tree species is declining. Suitable
ground often has birch and Rowan seedlings and young saplings suppressed by
browsing. These may rapidly get away after a reduction in browsing and may form
extensive dense thickets. Regeneration of desirable species such as Hazel, Ash and
oak may be absent or does not successfully establish naturally. If so, consideration
should be given to planting. Until established, trees could be protected with staked
29

tubes/mesh, small temporary exclosures or anything to hand (old bits of fencing,
small wooden exclosures, etc., any thinnings from control of birch thickets, gorse
waste from clearing, etc.) Care should be taken to avoid scraping damage to mature
trees as this could easily dislodge any lichen or bryophyte interest. However,
planting should only be at low densities and not be at the expense of boundary edges
or be likely to result in the eventual loss of glades.
• Developments
Any construction works, including access tracks should, where possible, be
sited/routed to ensure minimal disturbance to mossy boulders, wayside trees, old or
veteran trees, areas of wet woodland and riparian areas. If the felling of any Atlantic
woodland/trees, including scrubby woodlands, cannot be avoided, specialist lichen
and bryophyte survey is strongly recommended to provide advice on minimising
impacts. Advice from specialists should also be sought on the impacts of changes in
hydrology as a result of water extraction for hydro-electric power schemes.
• Adopt the precautionary principle
Atlantic woodlands are very special habitats and some are protected by conservation
designations but many woodlands that are important for lichens and bryophytes lie
outside designated sites. If in doubt, it is a fairly safe to assume that the lichen and
bryophyte interest in an Atlantic woodland with mature and old trees, and hazel stools
is likely to be high, and particularly so if the woodland is rocky or has a ravine. Such
sites should be managed sensitively.
• Specialist survey
If proposed management includes operations that are potentially damaging to
habitats that may support lichen or bryophyte interest, seek specialist advice and if
necessary commission specialist surveys. In particular, all woodland thinning
operations and all developments that impact on any stands of Atlantic woodlands
should be subject to specialist lichen and bryophyte surveys.
30

References
Acton & Griffith, 2008a. Lichens of Atlantic Woodlands Guide 1. A water resistant field guide
focusing on Lobarion lichens; Guide 2 focuses on the Parmelion laevigatae. Plantlife Scotland.
Acton & Griffith, 2008b. Lichens of Atlantic Woodlands Guide 2. . A water resistant field guide
focusing on the Parmelion laevigatae. Plantlife Scotland.
Coppins, A.M. & Coppins, B.J. 2002. Indices of Ecological Continuity for Woodland Epiphytic
Lichen Habitats in the British Isles. British Lichen Society, London.
Woods, R.G. & Coppins , B.J. In prep. A Conservation Evaluation of British Lichens. British
Lichen Society, London.
Further reading
Management of woodland plants in Atlantic broadleaved woodland: a conservation framework.
Rick Worrell, in prep. Plantlife Scotland.
Lichens: An Illustrated Guide to the British and Irish Species. Frank Dobson. 5 th Edition
(2005). Richmond Publishing Co. Ltd. A guide to most of the common lichens of a range of
habitats.
Lichen Habitat Management. Fletcher, A. (ed.) 2001. British Lichen Society and Countryside
Council for Wales.
Other sources of information
www.bls.org.uk The British Lichen Society (BLS).
www.nwdg.org.uk The Native Woodland Discussion Group (NWDG) runs regular training
courses on lichens and bryophytes of Atlantic woodlands.
www.britishlichens.co.uk The britishlichens website has useful photos of many British lichens.
Lichen identification events
Two-day courses that give a basic introduction to lichens, species identification and habitats are
run by the Native Woodland Discussion Group (www.nwdg.org.uk). Week long course are run
through the Field Studies Council at Kindrogan Field Studies Centre.
Who to contact for advice
Plantlife Scotland, Ballan House, Allan Park, Stirling FK8 2QG
Tel: +44 (0)1786 478509 www.plantlife.org.uk, scotland@plantlife.org.uk
31

Scottish Natural Heritage, Great Glen House, Leachkin Road, Inverness, IV3 8NW.
Tel. 01463 72 5000 http://www.snh.org.uk/ The SNH species adviser for lower plants and
fungi: david.genney@snh.gov.uk
Acknowledgements
These course notes are largely based on the PowerPoint presentation given by Anna Griffith
shown at the Plantlife training event, and on a draft version of a leaflet currently being produced
for Plantlife Scotland by Andy Acton (lichenologist) & Gordon Rothero (bryologist). Oakwood
types largely follow the guidelines developed by Sandy Coppins for monitoring the condition of
oakwoods that have been designated as Sites of Special Scientific Interest (SSSIs) for their
lichen assemblage.
32

APPENDIX I
Norwegian Specklebelly (Pseudocyphellaria norvegica) and the Brown
Shingle-lichen (Fuscopannaria sampaiana)
Atlantic woods in Western Scotland support internationally important populations of both
these species. Both species are on the European Red List of threatened lichens with F.
sampaiana listed as Vulnerable and P. norvegica as Endangered. Western Scotland is the
world headquarters for P. norvegica.
Both species are Biodiversity Action Plan species and particularly good indicators of
Lobarion communities of high conservation importance in western Scotland. The presence
of either species in an Atlantic woodland is a very good indication that the woodland may be
of high conservation interest for its lichen assemblage, though, of course, their absence
does not indicate the woodland is of low interest for lichens.
Figure 21: Norwegian Specklebelly (Pseudocyphellaria norvegica) is a very good
indicator of high quality lichen habitat. It is mainly found on Hazel, oak, Ash, willow and
occasionally rock outcrops in Atlantic woodlands. Lobes are reddish brown when dry (darker
brown to grey brown when wet) with faintly grey-lilac powder along the margins and powdery
dots on the surface © Anna Griffith
33

Figure 22: Norwegian Specklebelly (Pseudocyphellaria norvegica)
Figure 23: Brown Shingle Lichen
(Fuscopannaria sampaiana) on
oak; this species is a very good
indicator of high quality lichen
habitat. It is mainly found on Hazel,
oak and Ash in Atlantic woodlands.
It is reddish brown when dry (paler
creamy grey-brown to darker greybrown
when wet) with pale greyish
to creamy powdery granules along
the lobe margins and spreading
onto the lobes © Andy Acton
34

Figure 24: A close-up of the Brown Shingle Lichen (Fuscopannaria sampaiana)
35

Figure 25. Map of 10km squares with records for the two Nationally Scarce, BAP lichens Pseudocyphellaria norvegica and Fuscopannaria
sampaiana in Great Britain and Ireland. Data from the NBN gateway http://data.nbn.org.uk/. © Crown Copyright. All rights reserved NERC
100017897 2004.
Norwegian Specklebelly Pseudocyphellaria norvegica Brown shingle lichen Fuscopannaria sampaiana
36

APPENDIX II
Photos of some other indicators of high quality lichen habitats in Atlantic
woodlands
Figure 26. Golden Specklebelly (Pseudocyphellaria crocata); lobes are pale grey brown
to dark red-brown when dry (darker brown to grey brown when wet) with yellow powder
along the margins and powdery dots on the surface. It is mainly found on Hazel, oak, Rowan
and willow. © Andy Acton
Figure 27: Smooth Loop lichen (Hypotrachyna laevigata) has pale grey leafy lobes and
is typical of Parmelion communities on birch, Alder and oak. © Andy Acton
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Figure 28: Tailed Loop Lichen
(Hypotrachyna taylorensis) has
pale grey leafy lobes and when
well-developed the older lobes roll
up to form distinctive tubes (‘tails’).
It is found on birch, Alder, oak and
rocks. © Andy Acton
Figure 29: Coral Lichen
(Sphaerophorus globosus) is
a shrubby coral lichen found on
birch, Alder, oak and rocks. A
patch of Cudbear Lichen
(Ochrolechia androgyna) is also
shown top left. © Andy Acton
38

Figure 30. ‘Black-eyed Susan’ (Bunodophoron melanocarpum); when fertile this coral
lichen has distinctive black fruits (the black eyes) when viewed from below.
39

Figure 31: Tree Flute (Menegazzia terebrata) has pale grey leafy lobes with distinctive
holes and is found on birch and willow. © Andy Acton
Figure 32: Barnacle Lichen (Thelotrema lepadinum) forms a whitish crust with distinctive
barnacle-like fruits and is found on Hazel, Ash, Rowan and oak. © Andy Acton
40

Figure 33. Orange Pox Lichen (Pyrenula
occidentalis): two separate thalli of the Pox
lichen are illustrated here - the two orangegreenish
tinged patches with black pimple-like
fruits. It can be found on Hazel, Rowan and
Ash. © Andy Acton
Figure 34: A close-up of the distinctive
fruits of ‘Blackberries in Custard’
(Pyrenula hibernica) on Hazel in the
Eas an Daimh Ravine, Glen Creran
SSSI, Argyll © Andy Acton
41