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Fraxinus Excelsior

Fraxinus Excelsior

Technical guidelines for genetic conservation and use Common ash excelsior

Alfas Pliûra1 and Myriam Heuertz2 1 Lithuanian Forest Research Institute, Girionys, , EUFORGEN 2 Centre de Recherche Public – Gabriel Lippmann, Luxembourg

These Technical Guidelines are intended to assist those who cherish the valuable ash genepool and its inheritance, through conserving valuable sources or use in practical . The focus is on conserving the genetic diversity of the at the European scale. The recom- mendations 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

Common ash ( L.) is the largest in the Fraxinus and at maturity (90-120 ) it can reach 20-35 m (maximum 40 m) in height. The mean stem diameter varies from 30-70 cm (maximum 150 cm) in adult specimens. The is irregu- lar with massive , elongated in forest stands. Common ash is pollinated. Flowering starts at 15-20 years on single and at around 30 years within stands at irregular intervals. The breeding sys- tem is polygamous, rang- ing from male to female individu- als with hermaphroditic interme- diates. Morphologically hermaph- roditic individuals are often pre- dominantly male or female. Inter- annual variation in expression is observed. The fully developed start to disperse by wind in the . Seed usu- orommon ashFraxinusFraxinus excelsiorCommon ashFraxinus excelsior excelsCommon ashFraxinus excelsior

ally lasts for two but can Distribution Importance and use last for up to six. Stored seed requires combined warm-cold stratification to germinate. The natural range of common Of the four different ash species Common ash requires a rich ash covers most of from growing naturally in Europe, soil and tolerates a pH as low as the shores of the Ocean common ash is the most impor- 4.5, but prefers soil above 5.5. It in the West to the Volga River in tant commercially. Despite the is highly tolerant of seasonal the East, with the exclusion of high demand for this quality tim- water-logging and favours flood- the most northern and southern ber, only a few European coun- plain forests. It is also a typical parts. The northern limit of the tries have gene conservation or species of slopes and ravines, natural range is about 64° North tree breeding programmes in growing in association with other in , the southern margin place for this species. characteristic species such as reaching 37° North in . In Common ash timber is hard, , lime and . Although mountainous areas, common elastic and withstands pressure, dormant trees are very cold ash is found in the Pyrenees at shock and splintering. It is used hardy, the young are sen- 1750-1800 m above sea level mainly for handles, and for sitive to . and in the Swiss Alps at 1630 m. sports equipment such as hock- Common ash exhibits inter- In (Iran), it can be found at ey sticks, oars and hurdles. It has mediate properties between a much higher elevations of up to a straight grain and there is little pioneer species and a permanent 2200 m. distinction between sapwood forest component. Although dis- and , making it very persal and natural regenera- valuable for , veneer and tion are efficient, the com- flooring. The formation of “black petition ability of the heart”, a dark stain of the hard- species is only strong , can occur in mature trees. when the ecological This varies within and between requirements are individual trees and different met. Vegetative sites and reduces the economic regeneration is value. Ash and are strong after cop- astringent and the leaves are picing. used in modern herbal medicine for their laxative properties. siorrCommon ash FraxinusFraxinus excelsiorCommon ashFraxinus excelsiorCommon exce ashFraxinus excels

Genetic knowledge Iberian Peninsula, the Alps Threats to and/or in and in the Balkan genetic diversity Peninsula. This result is in agree- The genetic variation of a species, ment with fossil data and On the European scale, common both within and between popula- the postglacial re-colonisation of ash is not an endangered tions, is influenced by many fac- Europe from these refuges. species. However, the natural tors. The mating system, pollen Nuclear DNA markers lev- range and area of ash forests has and , role and suc- els of intra-population differenti- decreased during the last 4000 cessional stage in forest ecosys- ation similar to other Noble years as the area of agricultural tems, site conditions and histori- such as , lands has increased. Silvicultural cal influences such as colonisa- elm and , but higher than methods have promoted com- tion patterns after the glacial peri- is found in and . High mon ash in the last 30-40 years ods of the Quaternary are particu- differentiation was particularly due to the high economic value, larly important. Two types of observed between populations supporting natural regeneration, genetic variation can be distin- in southeastern Europe and in planting and thinning. guished: (i) adaptive variation (i.e. northern central Europe, indicat- Common ash genetic enabling adaptability) and (ii) a ing the high conservation value resources are threatened by priori neutral variation (i.e. not of ash genetic resources from , loss of suitable affected by natural selection). these areas. habitats, unsustainable exploita- Adaptive variation, expressed tion and improper management in the phenotype in response to (i.e. uncontrolled transfer of natural selection, has been reproductive material), natural investigated through provenance climatic changes, global warm- and progeny trials. These studies ing, air pollution, competition revealed that variation between with other species, pests and families within provenances/ game damage. These pressures populations was generally as could lead to population extinc- high as variation between prove- tion. Despite the high regenera- nances/populations. tion potential, the reproduction Phenological traits, including of some valuable autochthonous the date of burst and set, populations is not ensured, and displayed geographic patterns the health status of mature on a large spatial scale, whereas stands in some countries has growth and form, which are influ- deteriorated significantly in enced by soil and competition recent years. Therefore, common conditions, varied at the local ash is considered to be threat- level. The existence of different ened at the population level by ecotypes, (i.e. floodplain, hillside, most countries. slope and limestone ecotypes), has never been proven by proge- ny studies. Chloroplast DNA data used to investigate neutral variation suggests ice age refuges in the elsiorsiorCommon ashFraxinus excelsiorFraxinusCommon ashFraxinus excelsiorCommon exc ashFraxinus ex

Guidelines for genetic tions). Whenever possible, in situ regeneration of the target conservation and use conservation activities should be species, creating multi-age struc- undertaken jointly for other ture and habitat diversity, and Genetic conservation aims at Noble Hardwoods. increasing generation turnover. ensuring continuous survival and Where common ash occurs in To conserve an even-aged adaptability of the target species. large populations in a country, in mature stand in situ, parts of the These objectives are met when situ conservation is sufficient, population should be opened the Multiple Population Breeding with the selection of up to three (thinned or cut in narrow strips of System (MPBS) is applied. gene conservation populations/ 15-30 m width) to create condi- Ideally in MPBS, a breeding pop- gene reserves of 5-15 ha in size, tions for natural regeneration. ulation is subdivided into sub- with at least 100 flowering trees Preferably, this should be under- populations which are then in each provenance. A high den- taken in the following the grown over a wide range of site sity of in situ gene conservation , when maximum seed is conditions. populations should be estab- produced by the stand. An area In each country where com- lished in Southeast Europe, adjacent to the gene reserve mon ash is found, an inventory especially in and could be set aside for natural should be undertaken to define , which have been regeneration, and could later be the geographical distribution of colonised by populations from incorporated as part of the the species, conservation status, different ice age refuges. In these reserve. threats and potential use pat- regions, neutral genetic markers To promote regeneration in terns. Ecogeographic zones show high differentiation among clear-cut strips, randomly select- (provenance regions) should be populations, suggesting that they ed, abundantly flowering seed delimited according to climatic may have different potentials to trees should be left. If the popula- variation, topography, soil and cope with future climatic condi- tion consists of some stands or vegetation. Trees are generally tions. Specific conservation groups of trees of different ages best adapted to the ecological efforts are also recommended in but there is no regeneration, the conditions of the region where northern central Europe, due to oldest stands or groups should they evolved. Therefore, local the high level of differentiation be cut as soon as the mast years material should be used for plan- between populations in southern have produced sufficient seed tations wherever possible, unless , although the historical yield or regeneration under the otherwise recommended as the origin of this differentiation still canopy or in areas set aside. result of data from provenance needs to be verified. Increasing the number of stands trials. In situ gene conservation pop- or demes (groups of trees) of dif- To ensure the adaptive ulations need to be man- ferent ages in the population potential of Fraxinus excelsior in aged to increase their enhances intra-population genet- Europe, it is recommended that adaptive potential ic variation as the portion of trees two complementary gene con- by ensuring involved in regeneration increas- servation networks of popula- the natural es. Regeneration can also be tions are established, specifical- stimulated by site scarification ly: (1) a network of 20-30 in situ and weed control. If these regen- populations throughout prove- eration support measures are not nance regions; and (2) a network successful, it is recommended of ex situ populations (progeny that material originating from the trials, provenance trials, collec- population is planted: seeds FraxinusCommon ashFraxinus excelsiorCommon ash Fraxinusexcelsio excelsiorCommon ashFraxinus

Distribution range of common ash

should be collected from at least injured trees, thus simulating and for conservation/breeding (each 50 trees per population, prefer- stimulating the natural selection of 2-4 ha in size) should be estab- ably from central parts of the processes in the forest, and lished in each provenance region gene reserve. To prevent gene stand regeneration. Each gene with entries sampled from single flow from outside the gene conservation population must be trees randomly chosen from 10- reserve, a buffer zone of 100- constantly monitored, including 20 stands within the region and 150 m should be created by the health status and regenera- from marginal populations if gradually removing mature flow- tion success. applicable. As soon as reproduc- ering ash trees within this zone. For populations that are mar- tive age is reached, open pollina- To secure the sustainability of ginal, isolated, endangered, tion of the best individuals select- each population, careful tending growing under special ecological ed within each should is required. Effective treatment conditions or carrying rare fea- ensure the next generation. About including adequate silvicultural tures, in situ conservation should 50 optimally adapted individuals measures, protection against be complemented by ex situ should be the founders of each disease or insect outbreaks, fire measures. The most effective new gene conservation/ breeding or other factors must be under- form is through progeny trials, sub-population. taken promptly. Thinning should which permits joint gene conser- be undertaken from below, vation and breeding. On a nation- removing suppressed and al scale, 1-3 progeny plantations orexcelsiorCommon Fraxinus ashFraxinus excelsiorCommon ashFraxinus excel excelsiorCommon ashFraxi EUFORGEN

These Technical Guidelines were Selected bibliography produced by members of the EUFORGEN Noble Hardwoods Network. The objective of the Baliuckas V., T. Lagerström, and G. Eriksson. 2000. Within and among popula- tion variation in juvenile growth rhythm and growth in Fraxinus excelsior Network is to identify minimum and avium. Forest Genetics 7 (3): 193-202. genetic conservation require- Bugala, W. (ed). 1995. Our forest trees: Popular scientific monograph, Volume ments in the long term in Europe, 17: 569 European ash - Fraxinus excelsior L. [in Polish]. Institute of in order to reduce the overall , . conservation cost and to improve Heuertz, M. 2003. Population genetic structure in common ash: a focus on the quality of standards in each southeastern European genetic resources. PhD thesis, Free University of Brussels, , and the Public Research Centre – Gabriel Lippmann, country. Luxembourg. Kleinschmit, J., J. Svolba, V. Enescu, A. Franke, H.M. Rau and W Ruetz. 1996. First results of provenance trials of Fraxinus excelsior established in 1982 [In German]. Forstarchiv 67: 114-122. Wallander, E. 2001. of wind- in Fraxinus () – an Citation: Pliûra A., and M. Heuertz. ecophylogenetic approach. PhD thesis, Botanical Institute, Göteborg University, Sweden. 2003. EUFORGEN Technical Guidelines for genetic conserva- Weiser, F. 1995. Studies into the existence of ecotypes of ash (Fraxinus excel- sior) [in German]. Forstarchiv 66: 251-257. tion and use for common ash (Fraxinus excelsior). International Genetic Resources Institute, Rome, Italy. 6 pages.

Drawings: Fraxinus excelsior, Giovanna Bernetti. © IPGRI, 2003.

ISBN 92-9043-567-4

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