B A C K F RO M T H E B R I N K M A N A G E M E N T S E R I E S
B A C K F RO M T H E B R I N K M A N A G E M E N T S E R I E S
Front cover image: B u x b a u m i a v i r i d i s capsules on an alder log Stewart Taylor, RSPB
Design: rjpdesign.co.uk
Print: crownlitho.co.uk
Looking after Green Shield-moss
(Buxbaumia viridis) and other
mosses and liverworts
on dead wood
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Alder stands may have ideal habitat for Buxbaumia viridis © Stewart Taylor
Plantlife is the UK’s leading charity working to
protect wild plants and their habitats. The charity
has 10,500 members and owns 23 nature reserves.
In 2008, Plantlife is ‘Lead Partner’ for 77 species
under the UK Government’s Biodiversity Action
Plan. Conservation of these species is delivered
through the charity’s Back from the Brink species
recovery programme, which is jointly funded by
Countryside Council for Wales, Natural England,
Scottish Natural Heritage, charitable trusts,
companies and individuals. It involves its members
as volunteers (Flora Guardians) in delivering many
aspects of this work. Plantlife’s head office is in
Salisbury, Wiltshire, and the charity has national
offices in Wales and Scotland.
Plantlife Scotland
Balallan House
Allan Park
Stirling
FK8 2QG
Tel. 01786 478509
www.plantlife.org.uk
[email protected]
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Green Shield-moss (Buxbaumia viridis)
The moss Buxbaumia viridis is a rare and
endangered species which grows on decaying
wood, an important habitat for a whole range
of mosses and liverworts, a group of small and
ancient plants collectively known as bryophytes.
Buxbaumia viridis is a threatened species here
and in Europe as a whole, and one that has
suffered a considerable loss of available habitat.
It has a scattered distribution in forest habitats
across the northern hemisphere from southwest Asia and China to western North America
but is limited to montane areas in the southern
part of its range.
The habitat
A fallen tree provides an ideal habitat for a
range of bryophyte species once the bark has
fallen away and the wood begins to rot,
whereas standing dead wood, though good for
other organisms, is usually too dry for
bryophytes. Many of these specialist mosses
and liverworts are widespread in Scotland but
some are rare. We do not know what precise
conditions on the log give rise to the most
diverse stands of this community but it seems
likely that the uneven texture of the log, its
sponge-like capacity for holding moisture and,
possibly, the nutrients released during decay
are all important. Size does matter here as
the larger logs offer not just the obvious
greater surface area but also better buffering
against changes in humidity and greater
longevity. Most Buxbaumia viridis plants are
associated with logs that have (or once had) a
diameter of more than 20cm.
This broadleaf, sheltered woodland at Abernethy Forest in Strathspey has numerous logs suitable
for Buxbaumia viridis © Stewart Taylor
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Buxbaumia viridis capsules may be grazed probably by slugs, birds or rodents. © Stewart Taylor
The problems
The species
The loss of woodland cover over the
centuries and, more recently, the intense
management of woodland areas has led to a
significant loss of habitat for these bryophyte
species. The removal or ‘tidying up’ of fallen
trees has been a particular problem so that
the volume of dead wood, in even the least
managed of our woodlands, is far below that
in natural woodland. In stands that have had
little recent management, the volume of fallen
dead wood may be in excess of 60m3 per
hectare, which is comparable with old-growth
woodland in Europe and America. However, in
woodland managed for timber, volumes of
dead wood can be less than 20m3 per hectare.
The problem for these bryopyhtes is not just
one of simple loss of habitat but also lack of
continuity of habitat at any one site when the
absolute volume of dead wood is so small.
Green Shield-moss (Buxbaumia viridis) is
different to virtually all other mosses in that it
has tiny leaves which are invisible in the field;
this means that it can only be spotted when it
has its distinctive fruiting-body. With most
other mosses it is the green leaves (the
gametophyte) that you see frequently with
small fruiting bodies (the sporophytes).
Buxbaumia viridis has a relatively large capsule
raised on a stalk so that the whole structure is
about 2cm tall. The capsule is green in the
winter, turning a brownish-straw colour in
summer when the millions of spores are shed.
Confusion is only possible with the related
Brown shield-moss (Buxbaumia aphylla), which
can also occur on dead wood. It is probable
that the vegetative parts of the plant persist
on logs but only produce fruiting bodies when
the conditions are favourable. As it rots away,
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Buxbaumia viridis can be found on deadwood in
conifer plantations © Gordon Rothero
Confusion is only possible with the related
Brown shield-moss Buxbaumia aphylla
© Stewart Taylor
the condition of any one log will eventually
become unsuitable for Buxbaumia viridis, so
spore production is essential to enable the
plant to move on. The number of capsules
produced each year is therefore critical.
known on some 13 sites. There are two
concentrations of records, one in the glens
west of Inverness and the other in Strathspey
with a few recent records on Deeside. It
seems likely that some other sites further
west will be found, although Buxbaumia viridis
is a boreal-montane species and presumably
not suited to the wetter, milder west. It has
never been seen in southern Britain and all the
more southerly sites in Europe are associated
with mountains.
Old capsules of Buxbaumia viridis.
© Stewart Taylor
Green Shield-moss grows on dead wood from
a range of trees, both broadleaf and conifer,
and may persist even when the wood is very
fragmented, even occurring on the wood chips
on old anthills. It usually grows on softer,
fibrous dead wood but has also been found on
the bark of dead alder.
All the UK records for Buxbaumia viridis are in
the north and east of Scotland, extending from
East Ross in the north and, historically, to
Arbroath in Angus in the south. It is currently
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Key to symbols
1950 onward
Pre 1950í
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Anastrophyllum hellerianum is a tiny, nationally
scarce liverwort that grows on dead wood
© Gordon Rothero
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0
1
2
3
4
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Map created using DMAP
In the United Kingdom, Buxbaumia viridis is
rated as Endangered in the bryophyte Red
Data Book (by Church et al., 2001), has a
Biodiversity Action Plan and is listed on
Schedule 8 of the Wildlife and Countryside
Act. The Endangered threat category means
that the plant is deemed to be at a very high
risk of extinction in the wild because of its
small range and patchy distribution and the
small number of plants in total. It is also listed
in Annex II of the EC Habitats and Species
Directive and on Appendix 1 of the Council of
Europe Bern Convention. Its listing on
Schedule 8 means that is illegal to collect the
plant without a licence.
Perhaps the best indicator species of the right
kind of conditions for Buxbaumia viridis are the
two liverworts Nowellia curvifolia and Riccardia
palmata. These two species are common on
rotten logs in humid sites, Nowellia curvifolia
forming distinctive copper-coloured patches of
thin stems and Riccardia palmata forming dense
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green patches of flat fronds. All of the other,
more frequent, associates of Buxbaumia viridis
in the table below are very common species in
a variety of habitats and not just on rotting
wood. Two nationally scarce species also occur
on similar logs: Anastrophyllum hellerianum
which is a tiny liverwort with yellow stems
tipped with dark red, and Calypogeia suecica
which forms flat whitish, green patches but
needs a microscope for confirmation.
The liverworts Nowella curvifolia (shown below)
and Riccardia palmata are perhaps the best
indicator species of the right kind of conditions
for Buxbaumia viridis. © Gordon Rothero
B A C K F RO M T H E B R I N K M A N A G E M E N T S E R I E S
Buxbaumia viridis growing amidst associated
species of lichens and bryophytes at
Rothiemurchus © Gordon Rothero
Percentage frequency of
associated species on five logs
with Buxbaumia viridis.
Species
Dicranum scoparium
Lophocolea bidentata
Mnium hornum
Dicranum fuscescens
Hylocomium splendens
Lepidozia reptans
Lophozia ventricosa
Oxalis acetosella
Pohlia nutans
Riccardia palmata
Cladonia sp
Deschampsia flexuosa
Eurhynchium praelongum
Nowellia curvifolia
Pinus seedling
Rhytidiadelphus loreus
Tetraphis pellucida
Tritomaria exsectiformis
Frequency
80%
60%
60%
40%
40%
40%
40%
40%
40%
40%
10%
10%
10%
10%
10%
10%
10%
10%
Site management
The most important management message is
the most simple: leave all fallen timber. For
some amenity woodlands there may be health
and safety issues over trees near paths but
otherwise all wood should be left where it falls.
Obviously not all dead wood is suitable for
bryophytes, particularly those dry, stark, grey
remains of old trees in open, heathy pine
woodland, although these do provide an
important habitat for other organisms. The
Forest Enterprise booklet Life in the Deadwood
provides a wealth of information on the general
importance of deadwood in woodland and
suggests that a minimum of 5m3 per hectare of
logs of 20cm diameter should be the aim.
Studies in Sweden suggest that the best
predictor of the occurrence of Buxbaumia viridis
is the volume of large dead wood on a site.
In semi-natural woodlands there should be a
policy of increasing the amount of large fallen
timber, often termed ‘coarse woody debris’.
This may be a passive policy of not clearing
fallen timber which will gradually increase the
volume of dead wood, or an active policy of
felling or uprooting selected trees where the
woodland can sustain this kind of
management. Most sites for Buxbaumia viridis
are close to watercourses, possibly because of
the increased humidity on such sites, and
increasing the amount of dead wood in such
sites would have added value.
A large proportion of the woodland within the
stronghold areas for Buxbaumia viridis in north
eastern Scotland is commercial plantation with
a relatively short rotation. Such woodland
may have a lot of dead wood but most of it
tends to be too small for Buxbaumia viridis.
Extending the rotation on at least some of these
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sites would increase the volume of coarse
woody debris. Within the plantations there are
usually areas with some broadleaf woodland,
often along watercourses, and these offer an
opportunity for habitat creation. Felling a few
large trees from the edge of the plantation into
such areas, possibly during harvesting, would
provide a habitat for the future. Although such
sites might initially be too open and dry on a
clear-fell site, once the re-stock trees are big
enough to provide shelter, the dead trees will
have decayed enough to offer suitable habitat.
Similarly, it would also be possible to leave
tangles of wind-throw to become a patch of
dead wood within the re-stock site, allowing
sufficient distance between the logs and the new
crop so that enough light can penetrate.
When a patch of woodland is clear-felled, there
are always large, cut logs left on the site. In
some situations it may be possible to use these
to create suitable habitat if they can be moved
to appropriate sites that are relatively
sheltered but that will not be too shaded by
the new crop of trees. This is best done during
felling when the appropriate machinery is on
site. The area of available habitat would be
increased if the logs were not in neat stacks.
Continuity of supply
Decaying wood is a habitat with a finite
lifetime; eventually the log will rot away and be
absorbed into the woodland floor. Buxbaumia
viridis is able to persist on small fragments long
after the log has fallen apart but eventually it
will die out. To ensure the continuity of the
community of rotten log species on any site,
there will need to be a supply of logs some of
which already have the bryophytes, some which
are just coming into the right condition for
colonisation and yet more that are just fallen.
The period over which a log remains in suitable
condition will vary; conifer logs seem to remain
viable for much longer than birch which falls
apart rather quickly. So a flexible approach will
be needed depending on the type of woodland.
Buxbaumia viridis is found on this fallen log resting on a dry stone wall at Rothiemurchus, Strathspey.
© Gordon Rothero
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RSPB Abernethy National Nature
Reserve – a case study of pro-active
deadwood management
RSPB are working hard to increase the amount of
dead wood at Abernethy Forest, a stronghold for
Buxbaumia viridis © Stewart Taylor
A key objective of the RSPB’s management plan
for Abernethy Forest is the development of a
self-sustaining native forest of natural character.
One attribute of this natural character is the
abundance and frequency of dead wood. At
Abernethy, at least 40% of the BAP, Red Data
Book, Nationally Rare or Nationally Scarce
non-avian species found in woodland areas are
associated with deadwood. However, in most
areas of the forest, current deadwood
frequency and volumes are as little as 5 – 10%
of that which is recorded from more natural
boreal forests in Scandinavia and North West
Russia, the closest analogies to Abernethy in
continental Europe.
Methods used include totem poling by pole
saw, harvester and by tree surgeon, ringbarking or other damage to the lower trunk
(all to create standing dead wood), felling at
ground level or to leave a high stump, and
winching with hand or tractor winch (all to
create fallen wood).
The RSPB have identified approximately1600 ha
of Scots pine plantations more than 40 years
old in Abernethy, within which woodland
restructuring will be by a rolling programme of
deadwood creation. No timber will be
extracted. Their aim is to ensure a continuity of
standing and fallen deadwood in both space and
time. As a minimum, they aim to ensure that
1m3 of fresh deadwood is created in each
hectare over a five to ten year cycle.
Creation of deadwood is integrated with
other management aims, including maintaining
minority broadleaf species and juniper, or to
enhance areas of blaeberry.
The RSPB use a variety of techniques to create
deadwood, such as pulling trees over with a
tractor and winch. © Stewart Taylor.
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Summary of management
recommendations for Green Shieldmoss (Buxbaumia viridis)
Even the most simple management to increase
the volume of dead wood will be worthwhile.
Who to contact for advice
If you think you have Buxbaumia viridis in your
woodland and would like some specialist
support, then please contact:
Plantlife Scotland
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Include a deadwood policy in the site
management plan
Leave all fallen trees in situ.
Leave individual logs, not neatly stacked
piles.
Actively manage and fell to create
deadwood logs of at least 20cm diameter,
during routine forestry operations, aiming
for a minimum of 5m3 per ha.
Favour sites adjacent to watercourses or
sheltered, humid areas for deadwood
creation and retention.
Ensure a continuous supply of coarse
woody debris.
Extend rotation of commercial
compartments if possible, to increase the
volume of coarse woody debris.
Utilise broadleaf areas within commercial
stands to create deadwood habitat.
Fell a few trees from commercial
compartments into broadleaf areas.
Leave tangles of wind-throw to become a
patch of dead wood within re-stock sites,
allowing sufficient distance between the
logs and new crops so that enough light
can penetrate.
Where possible, move remaining logs in
clear fell areas to more suitable sites.
Balallan House
Allan Park
Stirling
FK8 2QG
Tel 01786 478509
www.plantlife.org.uk
[email protected]
British Bryological Society
c/o Gordon Rothero
Stronlonag
Glenmassan
Dunoon
Argyll
PA23 8RA
[email protected]
This leaflet was written for Plantlife Scotland
by Gordon Rothero, Bryologist
B A C K F RO M T H E B R I N K M A N A G E M E N T S E R I E S
Buxbaumia viridis capsule. © Stewart Taylor
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B A C K F RO M T H E B R I N K M A N A G E M E N T S E R I E S
www.plantlife.org.uk
[email protected]
Plantlife International – The Wild Plant Conservation Charity
Plantlife Scotland
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Tel. 01786 478509
ISBN: 978-1-904749-41-7 © October 2008
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F ro nt c ov er im a ge: B u x b a u m i a v i r i d i s c aps ul es o n an al de r l og St ew ar t T ayl or , R SP B
British Lichen Society
De si gn : r j p de si gn. co. uk
Pri nt : crow nl i t ho. co. uk
Damper woodlands within RSPB Abernethy Caledonian pine forest in Strathspey are a stronghold for
Buxbaumia viridis © Stewart Taylor