BACK FROM THE BRINK MANAGEMENT SERIES Lichens and elm trees
Back from the Brink Management Series Elm trees were once a familiar part of the countryside and cultural landscape throughout the British Isles, with well grown trees often found in parklands, pastures and along roadsides. In some parts of the country Wych Elm was also a major component of our ancient woodlands.the main epidemic of Dutch Elm disease in the late 1960s and 1970s killed an estimated 20 million trees.this dramatically changed the landscape of the British Isles, but the effect on the flora associated with these trees has been less widely documented. Why were Elm trees important for lichen? Over 200 lichen species have been recorded growing on elms in Britain. Old Elm trees had a rough, water retentive, naturally alkaline bark (ph 4 7), which lichens favour. Old elms often grew in well-lit situations in open parkland, in pasture and along roadsides which were ideal for the colourful and species-rich Xanthorion lichen community to develop.this community is characterised by the presence of the bright yellow, leafy lichen Xanthoria parietina, along with grey and brown species belonging to the Physcia family. In many areas of central, eastern and southern England these species were joined by a number of Elm specialists including: Anaptychia ciliaris Eagle s claws Bacidia incompta Sap-groove lichen Caloplaca luteoalba Orange-fruited Elm-lichen Collema fragrans Clustered mini-jelly lichen Cryptolechia carneolutea Shy cross-your-heart lichen Gyalecta flotowii Pale crater lichen Today, all these species are Red Listed, i.e. they have undergone a dramatic and significant decline, and are now rare and threatened not just in the British Isles but also in parts of Europe. Bacidia incompta and Caloplaca luteoalba are also Priority Species under the UK Biodiversity Action Plan. Sap-groove lichen (Bacidia incompta)
Collema fragrans Anaptychia ciliaris Caloplaca luteoalba Bacidia incompta Gyalecta flotowii Cryptolechia carneolutea
Back from the Brink Management Series The decline of Orange-fruited Elm-lichen (Caloplaca luteoalba) Orange-fruited Elm-lichen was once widespread in central and south-eastern England and parts of eastern Scotland and unlike many lichens, it is relatively rare in the western oceanic areas. It is a characteristic species of old Elm trees in parklands, pastures and along roadsides, sometimes found with other Elm specialists like Bacidia incompta and Collema fragrans, often associated with wounds from cut branches. By the start of the Dutch elm disease epidemic it had already declined through the loss of hedgerows and atmospheric pollution due to sulphur dioxide, but between 1960 and 1980 it under went a dramatic decline. All records Current sites Current information indicates this species is no longer found on Elm in Wales and has been recorded from only three trees since 2000 in England. In Scotland the species is doing rather better although Dutch elm disease is progressing up the east side, threatening surviving Elms and their associated lichens.
Back from the Brink Management Series The importance of wayside trees Isolated trees along roadsides, by tracks and in pastures are collectively known as wayside trees. Their well-lit trunks may be affected by nutrient enrichment from dung and dust particles, so the lichen species found on these trees are very different from those found in ancient woodland. In the absence of Elms, trees with a naturally alkaline bark (such as Ash, Maple and Sycamore) are very important for many lichens including some that were formerly widespread on the old Elms. Several of the former Elm specialists often favour damaged trees, occurring around and below old wounds and sap runs, or are found on hard lignum inside hollow trees. How can we conserve these species? All the Elm lichen specialists survive, albeit in small quantities, on other trees such as Ash, Beech, Field Maple, Horse Chestnut and Sycamore.They show a preference for veteran trees that are often hollow or wounded, and are sometimes found on trees that receive no statutory protection. Conserving and managing these veteran wayside trees will help to protect these and many other uncommon and declining lichen species. Current threats to wayside tree lichens include the: Continuing loss of old wayside trees through natural causes and their non-replacement Loss of trees along roadsides due to road improvement schemes Increase of ammonia and nitrogen pollution occurring as a result of intensive agriculture Increase of Ivy on the trunks of hedgerow trees smothering the lichens that grow on them Elm specialists and many other lichens associated with wayside tree habitats can be conserved by: Protecting trees supporting populations of Elm specialists through Tree Preservation Orders Liaising with landowners and managers of sites with important populations of Elm specialists and other threatened wayside tree species Ensuring good practice is used when managing habitats around and adjacent to important trees Developing agri-environment schemes to encourage tree planting in places that have been highlighted as important for lichens that grow on wayside trees
Further advice and information on lichens associated with Elm trees can be obtained from: Plantlife International The Conservation Officer 14 Rollestone Street, British Lichen Society Salisbury, The Natural History Museum Wiltshire Cromwell Road, SP1 1DX London Tel: 01722 342730 SW7 5BD Email: enquiries@plantlife.org.uk Email: b.edwards@dorset-cc.gov.uk English Nature Northminster House, Northminster, Peterborough, PE1 1UA Tel: 01733 455000 Orange-fruited Elm-lichen (Caloplaca luteoalba) BRITISH LICHEN SOCIETY Text written by Bryan Edwards Photographs by Bryan Edwards & The Natural History Museum Plantlife International wishes to acknowledge the financial support of English Nature in this jointly resourced project. See also: Veteran Trees: A guide to good management. Helen Read. English Nature. 2000. Elm map project: http://www.ramblers.org.uk/elms/default.htm ISBN: 1 904749-06-2 DESIGN: RJP DESIGN 01234 315147