White elm (Ulmus laevis Pall.) isallogamous, and does not

hybridize with the other Euro-pean elm species which

belong to a different sec-tion of the genus. Flowers

are hermaphroditic andwind pollinated. Gen-eration time is shortand seed productionis regular and prolif-ic, with a high per-centage of viableseed and highgermination rates.Seeds dispersedby wind or carrieddownstream by

rivers enable thecolonisation of new

sites. Root suckeringmay play a role in the

regeneration of establishedstands whereas stool sucker-

ing is thought to be poor.The typical habitat of the

white elm is riparian deciduousforest, where it can tolerate pro-longed flooding for longer periods

Ulmus laevis

These Technical Guidelines are intended to assist those who cherish the valuable white elmgenepool and its inheritance, through conserving valuable seed sources or use in practicalforestry. The focus is on conserving the genetic diversity of the species at the European scale.The recommendations provided in this module should be regarded as a commonly agreed basisto be complemented and further developed in local, national or regional conditions. TheGuidelines are based on the available knowledge of the species and on widely acceptedmethods for the conservation of forest genetic resources.

European white elm

Eric CollinCEMAGREF, Nogent-sur-Vernisson, France

Technical guidelines for genetic conservation and use

Biology and ecology

EUFORGEN

and withstand lower tempera-tures than the field elm (U. minorMill.), with which it is often asso-ciated. Although it is typicallyfound in moist sites, it can toler-ate moderately dry, deep soilsand it is also found as a compo-nent in wooded steppe environ-ments. Along with field elm, thewhite elm is sporadically found inmixed oak forest. It is not foundon mountainous sites andprefers altitudes of less than 300m. In forest stands, it is a secondstorey tree, and in the open it canreach heights of 35 m. Individualtrees rarely live longer than 200years, but have been recordedas old as 300.

White elm is distributed acrosscentral and eastern Europe, fromthe Ural Mountains to easternFrance, and from southern Fin-land to the Caucasus and Bosnia.Since it is relatively rare and oftenconfused with the other two elmspecies indigenous to Europe, itsdistribution in southern Franceand northern Switzerland hasbeen underestimated in the past.It must still be confirmed if smallriparian populations recentlydiscovered in southern Franceare autochthonous or estab-lished aliens. Natural populations

of white elm are notfound in the British

Isles, Italy or Spain,and very little is

known aboutthis speciesin western

Europe.

White elm is of low economicvalue and unlike other Europeanelms, the timber is not prized.The cross-grained wood causesdifficulty in machine cutting anddefects. Wood density is lowerthan in other elm species, and itproduces poor quality firewood.However, due to its fast growth,ornamental value, and toleranceto soil compaction, de-icing saltsand air pollution, white elm haslong been used for amenityplantings in towns and on road-sides. It is rarely affected byDutch Elm Disease (DED) inwestern Europe, and its reneweduse in urban forestry has beensuggested.

Distribution Importance and use

Ulmus laevis UlmuEuropean white elmUlmus laevisEuropean white elmUlmus laevisEuropean white elm

Ulmus laevis has not been div-ided into sub-species and var-ieties. More information is parti-cularly needed about U. celtidea- an endemic species occurringin Russia, taxonomically veryclose to the white elm.

Studies using differentmolecular markers have revealedsignificant differences of whiteelm from the other two Europeanelm species, and also highlight-ed similarities with its NorthAmerican counterpart in thesame section, the Americanwhite elm (U. americana L.).

Chloroplast DNA studies of alarge, West European sampleidentified the same haplotype in93 % of the trees, and only twoother types: a rare type in south-west France, and another on thesouth eastern limit ofthe sampled zone.Isoenzyme studiescarried out in Finlandsuggest that randomgenetic drift may have causedsubstantial differentiation amongthe small populations at thenorthern fringe of the naturalrange.

Habitat destruction has causedenormous damage to white elmpopulations, and continues topose a major threat to the genet-ic diversity of the species. Dra-matic changes in the landscapeare occurring in riparian forestsalong the banks of large rivers,especially where land can bedrained and reclaimed for agri-culture or poplar cultivation.Consequently, white elm is nowoften restricted to fragmentedpopulations of a limited size,facing the risk of genetic drift.

The impact of DED on whiteelm populations is more seriousin central and eastern Europe,where infections and mortalityare frequent, than at the westernfringe of its natural range. This islargely due to the bark beetles

(Scolytus sp.) which are the vec-tors of the DED fungal agent(Ophiostoma novo-ulmi), whichprefer to feed on field elms inwestern Europe and rarely visitwhite elms.

Threats togenetic diversity

Genetic knowledge

us laevis Ulmus lamUlmus laevisEuropean white elmUlmus laevisEuropean white elmUlmus laevisEuropean

Despite this pathological threat,the in situ conservation of whiteelm genetic resources is still pos-sible through the establishmentof a network of conservationstands. These stands should beselected across the natural dis-tribution range, incorporatingecological variation, comprisingat least 50 flowering trees ineach. In countries where thedistribution of this species inthe wild is unknown, a pre-liminary inventory shouldbe undertaken. Priorityshould be given to margin-al populations and rarefloodplain communities indanger of deforestation.Silvicultural managementshould stimulate andpromote natural regener-ation. However, plantingof the original or localmaterial may berequired when regen-eration is poor or thenumber of seed trees isinsufficient.

Complementary ex situconservation measures mustbe undertaken when no legalhabitat protection measure canbe taken, when populations aresmall and fragmented, or whenthe impact of DED is too strong.In emergency cases, ‘static’ con-servation measures, such asclonal archives and cryo-preservation of seed lots can beapplied. However, ‘dynamic’ ex

situ conservation units, such asconservation seed orchards (inartificial conditions) or pseudo insitu conservation units (plant-ations in original habitat), whichbrings together diverse materialfrom the same eco-region andenhances genetic exchange, arehighly recommended. Whiteelms can easily be propagatedby cuttings, and field clonalarchives can be maintained aslow hedges (1.5 – 2 m), which areless attractive to the vectors ofDED.

A European core collectionof elm clones has already

been established withmaterial from the ninecountries participatingin the EU RESGENproject. It is importantthat this collection iscomplemented withmaterial originatingfrom all the relevantregions of Europe.

aevis Ulmus laevisn white elmUlmus laevisEuropean white elmUlmus laevisEuropean white elmUlmus laev

Guidelines for geneticconservation and use

Ulmus laevis UlmEuropean white elmUlmus laevisEuropean white elmUlmus laevisEuropean whi

Distribution range of Europeanwhite elm.

The Author wishes to acknowledge contribution from Dr. Lorenzo Mittempergher and CAB InternationalForestry Compendium CD-Rom (2003). for the 'Biology and ecology' and 'Importance and uses' para-graphs

www.euforgen.orgMore information

mus laevis UlmusThese Technical Guidelines wereproduced by members of theEUFORGEN Noble HardwoodsNetwork. The objective of the Net-work is to identify minimum genet-ic conservation requirements inthe long term in Europe, in orderto reduce the overall conservationcost and to improve the quality ofstandards in each country.

Collin, E. 2003. EUFORGEN Tech-nical Guidelines for genetic con-servation and use for Europeanwhite elm (Ulmus laevis). Interna-tional Plant Genetic ResourcesInstitute, Rome, Italy. 6 pages.

Drawings: Ulmus laevis, GiovannaBernetti. © IPGRI, 2003.

ISBN 92-9043-603-4

EUFORGEN secretariat c/o IPGRIVia dei Tre Denari, 472/a00057 Maccarese (Fiumicino)Rome, ItalyTel. (+39)066118251Fax: (+39)0661979661euf_secretariat@cgiar.org

hite elmUlmus laevisEuropean white elmUlmus laevisEuropean white elmUlmus laevis

Selected bibliography

Collin, E. 2002. Strategies and guidelines for the conservation of the geneticresources of Ulmus spp. Pp. 50-67 in Noble Hardwoods Network: Reportof the fourth and fifth meetings, September 1999 and May 2001 (J. Turok,G. Eriksson, K. Russel and S. Borelli, compilers). International Plant Genet-ic Resources Institute, Rome, Italy.

Mittempergher, L., A. Fagnani, and F. Ferrini. 1993. The White Elm: an interest-ing and ill-known elm [in Italian]. Monti e Boschi 44 (4): 13-17.

Webber, J. 2000. Insect vector behavior and the evolution of Dutch elm dis-ease. Pp. 47-60 in The Elms: breeding, conservation and disease man-agement (C. P. Dunn, editor). Kluwer Academic Publishers, Boston, USA.

Whiteley R.E., Black-Samuelsson S., Jansson G. 2004. Within and betweenpopulation variation in adaptive traits in Ulmus laevis, the European whiteelm. (manuscript).

EUFORGEN