Looking after Green Shield-moss (Buxbaumia viridis) and ... - Plantlife

BACK FROM THE BRINK MANAGEMENT SERIES 


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 

scotland@plantlife.org.uk

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 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 60m 3 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 20m 3 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. 

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The species 

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,

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. 

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 

Buxbaumia viridis can be found on deadwood in 

conifer plantations © Gordon Rothero 

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 

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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 

4 

0 

9 

8 

7 

6 

Key to symbols 

1950 onward 

Pre 1950í 

0 1 2 3 4 5 

Anastrophyllum hellerianum is a tiny, nationally 

scarce liverwort that grows on dead wood 

© Gordon Rothero 

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

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 Frequency 

Dicranum scoparium 80% 

Lophocolea bidentata 60% 

Mnium hornum 60% 

Dicranum fuscescens 40% 

Hylocomium splendens 40% 

Lepidozia reptans 40% 

Lophozia ventricosa 40% 

Oxalis acetosella 40% 

Pohlia nutans 40% 

Riccardia palmata 40% 

Cladonia sp 10% 

Deschampsia flexuosa 10% 

Eurhynchium praelongum 10% 

Nowellia curvifolia 10% 

Pinus seedling 10% 

Rhytidiadelphus loreus 10% 

Tetraphis pellucida 10% 

Tritomaria exsectiformis 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 5m 3 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 

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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

RSPB Abernethy National Nature 

Reserve – a case study of pro-active 

deadwood management 

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. 

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 

1m 3 of fresh deadwood is created in each 

hectare over a five to ten year cycle. 


RSPB are working hard to increase the amount of 

dead wood at Abernethy Forest, a stronghold for 

Buxbaumia viridis © Stewart Taylor 

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). 

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. 

● 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 5m 3 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. 

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Who to contact for advice 

If you think you have Buxbaumia viridis in your 

woodland and would like some specialist 

support, then please contact: 


Balallan House 

Allan Park 

Stirling 

FK8 2QG 

Tel 01786 478509 


scotland@plantlife.org.uk 

British Bryological Society 

c/o Gordon Rothero 

Stronlonag 

Glenmassan 

Dunoon 

Argyll 

PA23 8RA 

gprothero@aol.com 

This leaflet was written for Plantlife Scotland 

by Gordon Rothero, Bryologist


Buxbaumia viridis capsule. © Stewart Taylor 

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Damper woodlands within RSPB Abernethy Caledonian pine forest in Strathspey are a stronghold for 

Buxbaumia viridis © Stewart Taylor 

British Lichen Society 


scotland@plantlife.org.uk 

Plantlife International – The Wild Plant Conservation Charity 


Balallan House,Allan Park, Stirling FK8 2QG 

Tel. 01786 478509 

ISBN: 978-1-904749-41-7 © October 2008 

Plantlife International – The Wild Plant Conservation Charity is a charitable company limited by guarantee. 

Registered Charity Number: 1059559 Registered Company Number: 3166339. Registered in England 

Charity registered in Scotland no. SC038951 

Front cover image: Buxbaumia viridis capsules on an alder log Stewart Taylor, RSPB Design: rjpdesign.co.uk Print: crownlitho.co.uk

Looking after Green Shield-moss (Buxbaumia viridis) and ... - Plantlife

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