Lichens and elm trees - Plantlife

BACK FROM THE BRINK MANAGEMENT SERIESLichens and elm trees

Back from the Brink Management SeriesElm trees were once a familiar part of the countryside and cultural landscapethroughout the British Isles, with well grown trees often found in parklands, pasturesand along roadsides. In some parts of the country Wych Elm was also a major component ofour ancient woodlands.The main epidemic of Dutch Elm disease in the late 1960s and 1970skilled 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 arough, water retentive, naturally alkaline bark (pH 4 – 7), which lichens favour. Old elms oftengrew in well-lit situations in open parkland, in pasture and along roadsides which were ideal forthe colourful and species-rich Xanthorion lichen community to develop.This community ischaracterised by the presence of the bright yellow, leafy lichen Xanthoria parietina, along with greyand brown species belonging to the Physcia family. In many areas of central, eastern and southernEngland 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 lichenToday, 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. Bacidiaincompta and Caloplaca luteoalba are also Priority Species under the UK Biodiversity Action Plan.Sap-groove lichen(Bacidia incompta)

Collema fragransAnaptychia ciliarisCaloplaca luteoalbaBacidia incomptaGyalecta flotowiiCryptolechia carneolutea

Back from the Brink Management SeriesThe decline of Orange-fruited Elm-lichen (Caloplaca luteoalba)Orange-fruited Elm-lichen was once widespread in central and south-eastern England and partsof eastern Scotland and unlike many lichens, it is relatively rare in the western oceanic areas. Itis 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, oftenassociated with wounds from cut branches. By the start of the Dutch elm disease epidemic ithad already declined through the loss of hedgerows and atmospheric pollution due to sulphurdioxide, but between 1960 and 1980 it under went a dramatic decline.All recordsCurrent sitesCurrent information indicates this species is no longer found on Elm in Wales and has beenrecorded from only three trees since 2000 in England. In Scotland the species is doing ratherbetter although Dutch elm disease is progressing up the east side, threatening surviving Elmsand their associated lichens.

Back from the Brink Management SeriesThe importance of wayside treesIsolated 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 thelichen 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 oldElms. Several of the former ‘Elm specialists’ often favour damaged trees, occurring around andbelow 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 areoften 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 otheruncommon and declining lichen species. Current threats to wayside tree lichens include the:●●●●Continuing loss of old wayside trees through natural causes and theirnon-replacementLoss of trees along roadsides due to road improvement schemesIncrease of ammonia and nitrogen pollution occurring as a result ofintensive agricultureIncrease of Ivy on the trunks of hedgerow trees smothering the lichens thatgrow on themElm specialists and many other lichens associated with wayside tree habitats can be conserved by:●●●●Protecting trees supporting populations of Elm specialists through TreePreservation OrdersLiaising with landowners and managers of sites with important populations ofElm specialists and other threatened wayside tree speciesEnsuring good practice is used when managing habitats around and adjacent toimportant treesDeveloping agri-environment schemes to encourage tree planting in placesthat have been highlighted as important for lichens that grow on wayside trees

Further advice and information on lichens associated with Elm treescan be obtained from:Plantlife InternationalThe Conservation Officer14 Rollestone Street, British Lichen SocietySalisbury,The Natural History MuseumWiltshireCromwell Road,SP1 1DXLondonTel: 01722 342730SW7 5BDEmail: enquiries@plantlife.org.ukEmail: b.edwards@dorset-cc.gov.ukEnglish NatureNorthminster House,Northminster,Peterborough,PE1 1UATel: 01733 455000Orange-fruited Elm-lichen (Caloplaca luteoalba)BRITISH LICHENSOCIETYText written by Bryan EdwardsPhotographs by Bryan Edwards & The Natural History MuseumPlantlife International wishes to acknowledge the financial support of English Nature in this jointlyresourced 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.htmISBN: 1 904749-06-2DESIGN: RJP DESIGN 01234 315147