Looking After Green Shield-Moss (Buxbaumia Viridis) and Other
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BACK FROM THE BRINK MANAGEMENT SERIES BACK FROM THE BRINK MANAGEMENT SERIES Looking after Green Shield-moss (Buxbaumia viridis) and other mosses and liverworts on dead wood capsules on an alder log Stewart Taylor, RSPB Design: rjpdesign.co.uk Print: crownlitho.co.uk Buxbaumia viridis 3 Front cover image: BACK FROM THE BRINK MANAGEMENT SERIES Alder stands may have ideal habitat for Buxbaumia viridis © Stewart Taylor Plantlife is the UK’s leading charity working to Plantlife Scotland protect wild plants and their habitats. The charity Balallan House has 10,500 members and owns 23 nature reserves. Allan Park In 2008, Plantlife is ‘Lead Partner’ for 77 species Stirling under the UK Government’s Biodiversity Action FK8 2QG Plan. Conservation of these species is delivered Tel.01786 478509 through the charity’s Back from the Brink species recovery programme, which is jointly funded by www.plantlife.org.uk Countryside Council for Wales, Natural England, [email protected] 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. BACK FROM THE BRINK MANAGEMENT SERIES Green Shield-moss (Buxbaumia viridis) fallen away and the wood begins to rot, The moss Buxbaumia viridis is a rare and whereas standing dead wood, though good for endangered species which grows on decaying other organisms, is usually too dry for wood, an important habitat for a whole range bryophytes. Many of these specialist mosses of mosses and liverworts, a group of small and and liverworts are widespread in Scotland but ancient plants collectively known as bryophytes. some are rare. We do not know what precise Buxbaumia viridis is a threatened species here conditions on the log give rise to the most and in Europe as a whole, and one that has diverse stands of this community but it seems suffered a considerable loss of available habitat. likely that the uneven texture of the log, its It has a scattered distribution in forest habitats sponge-like capacity for holding moisture and, across the northern hemisphere from south- possibly, the nutrients released during decay west Asia and China to western North America are all important. Size does matter here as but is limited to montane areas in the southern the larger logs offer not just the obvious part of its range. greater surface area but also better buffering against changes in humidity and greater The habitat longevity. Most Buxbaumia viridis plants are A fallen tree provides an ideal habitat for a associated with logs that have (or once had) a range of bryophyte species once the bark has diameter of more than 20cm. This broadleaf, sheltered woodland at Abernethy Forest in Strathspey has numerous logs suitable for Buxbaumia viridis © Stewart Taylor 1 BACK FROM THE BRINK MANAGEMENT SERIES 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 Green Shield-moss (Buxbaumia viridis)is centuries and, more recently, the intense different to virtually all other mosses in that it management of woodland areas has led to a has tiny leaves which are invisible in the field; significant loss of habitat for these bryophyte this means that it can only be spotted when it species. The removal or ‘tidying up’ of fallen has its distinctive fruiting-body. With most trees has been a particular problem so that other mosses it is the green leaves (the the volume of dead wood, in even the least gametophyte) that you see frequently with managed of our woodlands, is far below that small fruiting bodies (the sporophytes). in natural woodland. In stands that have had Buxbaumia viridis has a relatively large capsule little recent management, the volume of fallen raised on a stalk so that the whole structure is dead wood may be in excess of 60m3 per about 2cm tall. The capsule is green in the hectare, which is comparable with old-growth winter, turning a brownish-straw colour in woodland in Europe and America. However, in summer when the millions of spores are shed. woodland managed for timber, volumes of Confusion is only possible with the related dead wood can be less than 20m3 per hectare. Brown shield-moss (Buxbaumia aphylla), which The problem for these bryopyhtes is not just can also occur on dead wood. It is probable one of simple loss of habitat but also lack of that the vegetative parts of the plant persist continuity of habitat at any one site when the on logs but only produce fruiting bodies when absolute volume of dead wood is so small. the conditions are favourable. As it rots away, 2 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 Confusion is only possible with the related not suited to the wetter, milder west. It has Brown shield-moss Buxbaumia aphylla never been seen in southern Britain and all the © Stewart Taylor more southerly sites in Europe are associated with mountains. the condition of any one log will eventually become unsuitable for Buxbaumia viridis,so Old capsules of Buxbaumia viridis. spore production is essential to enable the © Stewart Taylor 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 3 BACK FROM THE BRINK MANAGEMENT SERIES 0 9 8 Key to symbols 7 1950 onward Pre 1950í Anastrophyllum hellerianum is a tiny, nationally 6 scarce liverwort that grows on dead wood © Gordon Rothero 0 1 2 3 4 5 green patches of flat fronds. All of the other, Map created using DMAP more frequent, associates of Buxbaumia viridis in the table below are very common species in In the United Kingdom, Buxbaumia viridis is a variety of habitats and not just on rotting rated as Endangered in the bryophyte Red wood. Two nationally scarce species also occur Data Book (by Church et al., 2001), has a on similar logs: Anastrophyllum hellerianum Biodiversity Action Plan and is listed on which is a tiny liverwort with yellow stems Schedule 8 of the Wildlife and Countryside tipped with dark red, and Calypogeia suecica Act. The Endangered threat category means which forms flat whitish, green patches but that the plant is deemed to be at a very high needs a microscope for confirmation. risk of extinction in the wild because of its small range and patchy distribution and the The liverworts Nowella curvifolia (shown below) small number of plants in total. It is also listed and Riccardia palmata are perhaps the best in Annex II of the EC Habitats and Species indicator species of the right kind of conditions Directive and on Appendix 1 of the Council of for Buxbaumia viridis. © Gordon Rothero 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 BACK FROM THE BRINK MANAGEMENT SERIES Buxbaumia viridis growing amidst associated Site management species of lichens and bryophytes at The most important management message is Rothiemurchus © Gordon Rothero 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 Percentage frequency of predictor of the occurrence of Buxbaumia viridis associated species on five logs is the volume of large dead wood on a site. with Buxbaumia viridis. In semi-natural woodlands there should be a Species Frequency policy of increasing the amount of large fallen Dicranum scoparium 80% timber, often termed ‘coarse woody debris’. Lophocolea bidentata 60% This may be a passive policy of not clearing Mnium hornum 60% fallen timber which will gradually increase the Dicranum fuscescens 40% volume of dead wood, or an active policy of Hylocomium splendens 40% felling or uprooting selected trees where the Lepidozia reptans 40% woodland can sustain this kind of Lophozia ventricosa 40% management. Most sites for Buxbaumia viridis Oxalis acetosella 40% are close to watercourses, possibly because of Pohlia nutans 40% the increased humidity on such sites, and Riccardia palmata 40% increasing the amount of dead wood in such Cladonia sp 10% sites would have added value.