Technical guidelines for genetic conservation and use Pedunculate and sessile oaks u Quercus robur/Quercus petraea

Alexis Ducousso1 and Sandor Bordacs2 1 INRA, Laboratory of Forestry Research, Pierroton, France 2 National Institute for Agricultural Qualification (OMMI), Budapest, EUFORGEN Hungary

These Technical Guidelines are intended to assist those who cherish the valuable white oaks genepool and its inheritance, through conserving valuable seed sources or use in practical forestry. 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 basis to be complemented and further developed in local, national or regional conditions. The Guidelines are based on the available knowledge of the species and on widely accepted methods for the conservation of forest genetic resources.

Biology and ecology The hybrid foliar characteristics resulting from controlled crosses resemble more the female parent Pedunculate (Quercus robur L.) and are not intermediate between and sessile (Q. petraea (Matt.) the parental forms. Liebl.) oaks are large deciduous Pedunculate oak is very tol- trees that reach 30–40 m in erant to soil conditions and the height and live 800 years and continental climate but it prefers more. They are monoecious and fertile and well-watered soils. allogamous, anemophilous and Mature trees tolerate flooding. predominantly outcrossing. Sessile oak has a very large eco- Trees usually reach seed- logical niche because it accepts bearing age at between soil pH from 3.5 to 9 and xeric to 40 and 100 years old. humid conditions. It is more tol- Mast seed crops vary erant to drought and poor soil according to individual than pedunculate oak but more tree, population, region sensitive to airless soil condi- and year. Vegetative tions. The minor species of ses- reproduction through sile oak in southeastern Europe coppicing has been are well adapted to wide ecolog- widely used to regenerate oak ical niches from humid to stands. extremely xeric. Natural hybridization in oaks In plains, plateaux and hills, has been reported in many stud- pedunculate oak is a pioneer ies. In European white oaks species and sessile oak a late hybridization is asymmetric: Q. successional species. Sessile petraea preferentially pollinates oak could reach climax stage if Q. robur. This asymmetry can summers are dry. In valleys and reinforce the succession of flood plains pedunculate oak is a species, replacing the pioneer late successional species which species (Q. robur) with a late suc- reaches climax with sycamore, cessional species (Q. petraea). plane, maple, ash and elm. Qedunculateuercus and sessile oaksQuercus robur roburQuercus petraeaPedunculate andQ sessileu

Distribution Importance and use Genetic knowledge

Sessile and pedunculate oaks Among the 13 European white Oak classification has raised are widely distributed in Europe oak species, pedunculate and conflicting opinions. There is so from northern Spain to southern sessile oaks are the most impor- much variation within species Scandinavia and from Ireland to tant. They are among the eco- that the concept of species is Eastern Europe. The peduncu- nomically and ecologically most questioned and further compli- late oak reaches the Ural Moun- important deciduous forest tree cations in taxonomy are due to tains. The natural range of ses- species in Europe. frequent interspecific hybridiza- sile oak is generally included in High forest, coppice-with- tion. The genus Quercus is sub- that of pedunculate oak but the standards and coppice are the divided into two subgenera: eastern limit is the Ukraine. They three main silvicultural regimes. Euquercus and Cyclobalanopsis. occur in plains on most types of Since the beginning of the 19th The subgenus Euquercus, now soil from sea level to 1800 m ele- century, foresters have converted called subg. Quercus, has been vation. Some minor species are many coppice and coppice-with- further subdivided into four sec- restricted to southeastern standard stands to high forest. tions: Rubrae, Protobalanus, Europe. Recently, silviculture that is close Cerris and Quercus. Both Q. to nature has been promoted in petraea and Q. robur belong to most European countries. Natural the last of these, also named regeneration should be a priority white oaks. These taxa are divid- but as it presents difficulties, ed into subspecies or minor plantations are sometimes species. required. The genetic quality of Oaks are among the most the forest reproductive material is diverse species of forest trees. crucial for the technical and eco- High levels of diversity are most nomic issues of these plantations. likely due to the maintenance of Oak timber is traditionally large population sizes, long-dis- used for building, ships and fur- tance geneflow and interfertility. niture. Today the best woods Long delays between genera- are used for quality cabinet- tions may be advocated, which making, veneers and barrel prevent oak populations from staves. Rougher material undergoing genetic drift. is used for fencing, roof White oaks make up a com- beams and specialist plex of species where genes are building work. It is also a commonly exchanged. The inter- good fuel wood. specific differentiation, regard- During autumns with good less of the molecular markers acorn crops (the mast years) ani- used, is only slightly larger than mals are grazed under the trees the intraspecific variation. to fatten them. This tradition still The geographic distribution exists in some restricted areas, of genetic diversity of chloroplast such as the Basque region and genomes is strikingly different eastern Europe. from that found using nuclear uoaksercusQuercus robur Quercus petraea PedunculatepetraeaQ and sessile oaksQuercus robuPedunuc

markers. The chloroplast Effective pollen dispersion Threats to genome of oak stands tends to has been measured by using genetic diversity be completely fixed within popu- parentage analysis. In Q. petraea lations but fully differentiated and Q. robur, more than half the Since 8500 BP, humans have among stands, whereas the male parents contributing to pol- strongly reduced the distribution nuclear genetic diversity resides lination of female parents located of oaks although the oak forest mostly within populations. Mole- in a 5-ha study stand were actu- coverage has increased since cular markers in the nucleus ally located outside the stand. the 19th century owing to silvicul- show a weak geographic struc- Although nearest neighbours tural management. Now, most ture with an east-to-west cline. contributed preferentially to polli- oak forests are managed, As for molecular traits, phe- nation, pollen dispersion curves primeval forests like Bialowieza notypic and adaptive traits also are clearly composed of a short- in Poland being very rare. A long exhibit extremely high levels of and long-distance contribution tradition of oak forest manage- diversity, even for fitness-related most likely related to different ment exists in Europe which traits. Phenotypic traits exhibit wind-transport mechanisms. seems very conservative regard- important population differentia- Acorns are dispersed by small ing genetic resources but the tion, but not as much as for rodents and the European jay, impact of the different silvicultur- chloroplast genome. Geographic which is very efficient in seed al practices is relatively trends of variation exist for phe- dispersal. unknown. The main threat is the nological traits, growth and form The distribution of adaptive introduction of exotic genotypes attributes. diversity is not correlated to neu- through plantations. This men- During the Quaternary era, tral diversity; there is no footprint ace was neglected in the past. oaks were subjected to impor- left of the maternal origin on the White oaks have very large eco- tant migrations in response to variation of adaptive traits. It is logical niches and sometimes climatic changes. During the last more likely that geographic vari- occupy extreme habitats (rocky ice age, their natural ranges ation for adaptive traits resulted slopes in mountains, sand were restricted to the southern from more recent local selection dunes, saline soils, peat bog, Iberian peninsula, central Italy pressures and human impact garigues). and the southern Balkan penin- than from the ancient origin of sula. In less than 7000 years, the stand. Humans are modify- oaks have spread to their mod- ing the genetic resources by ern-day range. Interspecific population transfers and also by hybridization was a key migra- silviculture regimes. tion mechanism as it facilitated the dispersion of late succes- sional species (Q. petraea) into pioneer species (Q. robur). The subsequent recolonization by various post-glacial migration routes has left a genetic trace which chloroplast DNA reveals. These movements have pro- foundly impacted the genetic diversity distribution. uculateercus and sessile oaksQuercus roburrobur Quercus petraeaPedunculate Quand sessile oaks

Guidelines for genetic gene conservation with the fol- conservation and use lowing objectives: 1) Sampling of genetic diversity: These The forest reproductive material sampling strategies defined popula- transfer in international trade empirically or according to tions are at must be in agreement with EU results obtained with molecu- high risk of disap- Directives and the OECD lar and quantitative markers. pearing because the scheme. All scientific studies are 2) Conservation of evolutionary number of individuals is congruent for the promotion of mechanisms: the high gen- low, habitats are unstable local material. Forest managers etic diversity of white oaks is and human impact is often are urged to follow these guide- the result of evolutionary considerable. Pedunculate oak lines: mechanisms such as inter- is suffering recurrent decay due 1) Natural regeneration must be specific hybridization. to the forest dynamic and the a priority. 3) Conservation of oak ecosys- evolution of forestry practices 2) Reproductive material must tems: humans have created (forsaking of coppicing, ageing be transferred only at a local ecotypes adapted to different of the populations). Insects and scale; transfers among management for wood pro- pathogens also might be danger- provenance regions must be duction and acorn crops. ous, such as oak mildew strictly limited. Foresters Most of these management (Microsphera alphitoides) which must use genetic resources systems are neglected is reported to be of the most for artificial regeneration from because foresters have common pathogens. American local seed stands, that have undertaken conversion to oak wilt (Cerastocystis been selected for their phe- high forest. fagacearum) is also a consider- notypic values and silvicultur- 4) Conservation of endangered able risk for European forests. al histories. populations and minor The severity of the problem alone 3) Development of seedling- species: marginal or endan- does not guarantee that practi- raising agreements between gered populations in Europe cal, social, administrative and nurseries and forest man- need conservation measures. legal problems will be solved agers is needed. The first step is to take a cen- rapidly. Therefore, an emergency sus, then define a policy for action plan must be drawn up on At present in Europe, these each situation. a European scale. genetic resources are not really endangered except in some situ- In situ conservation methods ations (marginal populations in should be generally preferred. If coastal sand dunes or peatbogs; natural regeneration methods are altitudes >1400 m) and at the not sufficient, an adapted and limits of the natural range. These specified ex situ conservation genetic resources are potentially programme including a con- threatened by introduction of trolled autochthonous reproduc- exotic genotypes, species purifi- tive material system (e.g. clonal cation, neglected practices and seed orchards) should be used conversion to high forest. For as well to preserve the endan- these reasons, we recommend gered genepool. development of programmes of QuercusPedunculate and sessile oaksQuercus robur Quercusrobur petraeaPedunculate andQ s

Distribution range of pedunculate oak

Distribution range of sessile oak Qsessileuercus oaksQuercus robur Quercus petraeaPedunculate petraea and sessile oaksQuercus robu

EUFORGEN

These Technical Guidelines were Selected bibliography produced by members of the EUFORGEN Temperate Oaks and Beech Network. The objective of Bonfils, P., A. Alexandrov and J. Gracan. 2001 In situ conservation. Technical presentations on gene conservation and management of European white the Network is to identify oaks. Pp. 43-47 in Third EUFORGEN Meeting on Social Broadleaves, 22- minimum genetic conservation 24 June 2000, Borovets, Bulgaria (S. Borelli, A. Kremer, T. Geburek, L. requirements in the long term in Paule and E. Lipman, eds.). IPGRI, Rome, Italy. Europe, in order to reduce the Bordács, S. and T. Skrøppa. 2001: Ex situ conservation. Technical presenta- tions on gene conservation and management of European white oaks. Pp. overall conservation cost and to 48-59 in Third EUFORGEN Meeting on Social Broadleaves, 22-24 June improve the quality of standards 2000, Borovets, Bulgaria (S. Borelli, A. Kremer, T. Geburek, L. Paule and E. in each country. Lipman, eds.). IPGRI, Rome, Italy. Kremer, A., J. Kleinschmit, J. Cottrell, E.P. Cundall, J.D. Deans, A. Ducousso, A.O. Konig, A.J. Lowe, R.C. Munro, R.J. Petit and B.R. Stephan. 2002. Is there a correlation between chloroplastic and nuclear divergence, or what are the roles of history and selection on genetic diversity in European oaks? Forest Ecology and Management 156 (1-3):75-87. Petit, R.J., S. Brewer, S. Bordács, K. Burg, R. Cheddadi, E. Coart, J. Cottrell, U.M. Csaikl, J.D. Deans, S. Fineschi, R. Finkeldey, I. Glaz, P.G. Citation: Ducousso, A. and S. Goicoechea, J.S. Jensen, A.O. König, A.J. Lowe, S.F. Madsen, G. Mátyás, Bordacs. 2004. EUFORGEN R.C. Munro, F. Popescu, D. Slade, H. Tabbener, B. van Dam, B. Ziegen- hagen, J-L. de Beaulieu and A. Kremer. 2002. Identification of refugia and Technical Guidelines for genetic postglacial colonisation routes of European white oaks based on chloro- conservation and use for pedun- plast DNA and fossil pollen evidence. Forest Ecology and Management culate and sessile oaks (Quercus 156 (1-3):49-74. robur and Q. petraea). Interna- Petit, R.J., C. Bodenes, A. Ducousso, G. Roussel and A. Kremer. 2004. Hybridization as a mechanism of invasion in oaks. New Phytologist 161 tional Plant Genetic Resources (1):151-164. Institute, Rome, Italy. 6 pages.

Drawings: Quercus petraea, Gio- vanna Bernetti. © IPGRI, 2003.

ISBN 92-9043-660-3

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