Oriental sweet gum is an attrac-tive, deciduous tree, 30-35 m inheight with a straight trunk of100 cm in diameter. Flowers are

unisexual and bloomfrom March - April.

The fruits ripen inNovember - Decem-

ber and the seeds arewind dispersed. Orientalsweet gum trees produce

seeds annually, but abundantseed crops occur every

three years. Although seedsgerminate readily, cold-moist

stratification provides uni-form conditions for germ-

ination.Oriental sweet gum

trees favour an eleva-tion of between 0-

400 m, a mean annual rainfall of1000-1200 mm and a meanannual temperature of 18°C.They can grow on slopes and drysoil, and optimal growth is onrich, deep and moist soils suchas bogs, river banks and coastalareas.

Liquidambar orientalis

These Technical Guidelines are intended to assist those who cherish the valuable oriental sweetgum genepool 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.

Oriental sweet gum

Murat Alan1 and Zeki Kaya2

1 Forest Tree Seeds and Tree Breeding Research Directorate, Gazi,Ankara, Turkey2 Middle East Technical University, Department of BiologicalSciences, Ankara, Turkey

Technical guidelines for genetic conservation and use

Biology and ecology

EUFORGEN

Oriental sweet gum oppor-tunely produces coppice bysprouting/ suckers, and inreasonable conditions, naturalregeneration is also possible.

The natural range of orientalsweet gum is a limited area insouthwest Turkey and RhodosIsland in Greece between 36°-38° N, and it is found at altitudesof 0-1000 m.

Oriental sweet gum is importantboth as a relic and endemicspecies. It is also economicallyimportant, due to its natural bal-sam producing ability, which israre among forest trees.

Since research and breedingfocus on the oil (balsam) produc-tion properties, data on woodcharacteristics are limited.Although the wood is not suit forsawmill processing, it is a pre-ferred fuel wood due to the oilcontent.

Sweet gum oil is used inmedicine, and the chemical

and cosmetic indus-tries. It is used as afixative in producingsoap and cosmet-ics, and is a raw

“ingredient” for cin-namyl alcohol and acid.

All oil produced is export-ed, providing an income for

local people. The species alsohas some value as an orna-mental, due to its attractiveform and colour.

Distribution Importance and use

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There is very little genetic knowl-edge or ongoing research on thisspecies. According to fossil evi-dence, although the speciesspread into the northern part ofAnatolia in the past, its distribu-tion is now restricted to theMediterranean. Two different mor-phological types are observed -those that produce oil and thosethat do not. Oil producing (bal-sam) trees are smaller withlarge branches and thebark has large scales.The type that does notproduce oil has astraight trunk withsmaller branches andsmaller bark scales.

Although there isvery little information avail-able on the genetics of thisspecies, its ecological andbiological characteristicsgive some indication aboutthe patterns of geneticdiversity. Trees growing fromsea level to 400 m, are knownas “plain sweet gum”, whiletrees at higher altitudes are“mountain sweet gum”. Treesgrowing at the higher alti-tudes form small groupsand tolerate frost better.

Studies on vegetativepropagation indicate thatgrafting methods fromcleft, bud and splice aremost successful in openforest areas and green-house conditions.

In 1947 the natural distributionarea of oriental sweet gum was7000 ha. Today it is limited toabout 3200 ha. Most of the treeshave been damaged due to pooroil production methods, whichinvolve wounding to stimulate

and increase the oil produc-tion. If performed proper-

ly, the trees can bekept healthy. Badly

wounded trees areabout 20 m inheight, crookedand weak, whileunwounded treescan reach about35m in height withstraight stems.Grazing and hab-

itat destruction arealso posing a threat,

especially in Turkey. The rich, fertile soils

found in the naturaldistribution area of thespecies means thatmany forest stands arebeing destroyed so theland can be farmed.Areas close to the culti-

vated land are alsodrained of the mois-ture that sweet

gums require for opti-mum growth.

The genetic structure of popula-tions urgently needs to be investi-gated for conservation purposes.

Although there are currentlyno comprehensive conservationmeasures, some practices, suchas seed stands, nature conser-vation areas and clonal seedorchards, have contributed tothe dynamic conservationprocess of oriental sweet gum.To meet the specific conser-vation requirements, these pro-grammes must be revised toincrease the population sizes andensure representation of diversehabitats within the natural rangeof the species.

For species with limitedgenetic information, it is oftenassumed that genetic variationfollows geographic and ecologi-cal variation. To capture theadaptive variation in orientalsweet gum, ecogeographiczones should be defined accord-ing to climatic variation. Theminimum effective size of a geneconservation population is 50trees, and it is recommendedthat each population is com-posed of at least 150-200, toensure enough flowering andfruiting trees.

Natural regeneration shouldbe stimulated and used whereverecological conditions allow. Seedproduction is normally sufficientand seed orchards can produceseed in about seven years. Toconserve and enhance the diver-

Threats togenetic diversity

Genetic knowledge Guidelines for geneticconservation and use

ntalis Liquidambar al sweet gumLiquidambar orientalisOriental sweet gumLiquidambar orientalisOriental swee

sity in small populations it is alsorecommended that effective pop-ulation sizes are increased byplanting local material.

Local material should also beused for afforestation purposeswherever possible. For the fur-ther improvement of orientalsweet gum plantations, “select-ed” and “tested” material (seedor clonal) should be used infuture.

In situ stands should be tend-ed, including thinning, under-story clearing, and weeding.These and other silviculturalmeasures in gene conservationstands are more effective than ifthe stands are left unmanaged.

Multiple uses of the geneconservation stands are encour-aged, including oil production.Recommended oil productionmethods (Topçuolu, 1968)should be followed to ensuresustainable oil production. Thedesignated gene conservationstands should serve as a sourceof reproductive material forbreeding, afforestation, oil pro-duction and landscape planting.Utilizing well adapted seedsources is the most effective toolin genetic conservation. Treescan also be planted in forestriverbeds to act as a firebreak forPinus brutia, and this should bepromoted to increase the use ofthis species.

In order to conserve sufficientgenetic variation to maintain theadaptive potential of orientalsweet gum, it is recommendedthat a network of in situ geneconservation stands is estab-lished throughout the distributionarea. Several fairly small popula-tions could be selected for theestablishment of such a network.Since oriental sweet gum existsin mixed stands with Platanusorientalis and Alnus orientaliswhich are also Noble Hard-woods, a few natural popu-lations could be extendedto conserve the associ-ated species.

This in situ networkshould be complementedwith ex situ collections,which will also enableprovenance research. Theestablishment of new clonal

seed orchards should be espec-ially considered for oil productionto reduce the pressure on naturalstands.

In regions where seedsources are limited, local ex situcollections (stands) should beestablished to serve both con-servation and seed production.These collections should typical-ly be established within the localregion of provenance. Measuresshould be taken to protect themagainst undesired pollinationfrom outside. These stands canbe bulk collections, seedlingseed orchards and clonal seedorchards. From a conservationperspective, priority should begiven to resources that arethreatened by extinction or con-

tamination from undesiredprovenances, small popula-tions and unique popula-tions or individuals.

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Distribution range of oriental sweet gum

www.euforgen.orgMore information

entalis LiquidambThese 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 conserva-tion cost and to improve the qual-ity of standards in each country.

Citation: Alan M. and Z. Kaya.2003. EUFORGEN TechnicalGuidelines for genetic conserva-tion and use for oriental sweetgum (Liquidambar orientalis).International Plant GeneticResources Institute, Rome, Italy.6 pages.

Drawings: Liquidambar orientalis,Giovanna Bernetti. © IPGRI, 2003.

ISBN 92-9043-605-0

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

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Selected bibliography

EUFORGEN