Populus alba
White poplar

White poplar (Populus alba) is a medium-sized deciduous and dioecious tree native to central and southern Europe and Central Asia, extending to North Africa, and has a lifespan of up to 400 years (Uzan Eken et al., 2024). The tree produces a lot of seeds and has fast root growth, making it a pioneer species capable of colonizing areas. It is found in humid areas, along rivers, in mixed woodlands, and at forest edges, thriving in areas with plenty of light, good access to water, and well-textured and well-drained soils.

White poplar is highly adaptable, tolerating salty water and urban pollution, and is resistant to pests and diseases (Uzan Eken et al., 2024). This makes it a popular choice for afforestation on saline and arid soils, urban and landscape plantings, soil stabilization, and watershed protection in riverine ecosystems, and a good candidate for resilient cultivation against future climatic changes (Uzan Eken et al., 2024). The species is especially valuable as an ornamental tree due to its distinctive white bark and two-coloured leaves with fuzzy undersides, giving the tree a silvery appearance.

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Acknowledgements

This distribution map has been developed by the European Commission Joint Research Centre (partly based on the EUFORGEN map) and released under Creative Commons Attribution 4.0 International (CC-BY 4.0)


Caudullo, G., Welk, E., San-Miguel-Ayanz, J., 2017. Chorological maps for the main European woody species. Data in Brief 12, 662-666. DOI: https://doi.org/10.1016/j.dib.2017.05.007

The following experts have contributed to the development of the EUFORGEN distribution maps:

Fazia Krouchi (Algeria), Hasmik Ghalachyan (Armenia), Thomas Geburek (Austria), Berthold Heinze (Austria), Rudi Litschauer (Austria), Rudolf Litschauer (Austria), Michael Mengl (Austria), Ferdinand Müller (Austria), Franz Starlinger (Austria), Valida Ali-zade (Azerbaijan), Vahid Djalal Hajiyev (Azerbaijan), Karen Cox (Belgium), Bart De Cuyper (Belgium), Olivier Desteucq (Belgium), Patrick Mertens (Belgium), Jos Van Slycken (Belgium), An Vanden Broeck (Belgium), Kristine Vander Mijnsbrugge (Belgium), Dalibor Ballian (Bosnia and Herzegovina), Alexander H. Alexandrov (Bulgaria), Alexander Delkov (Bulgaria), Ivanova Denitsa Pandeva (Bulgaria), Peter Zhelev Stoyanov (Bulgaria), Joso Gracan (Croatia), Marilena Idzojtic (Croatia), Mladen Ivankovic (Croatia), Željka Ivanović (Croatia), Davorin Kajba (Croatia), Hrvoje Marjanovic (Croatia), Sanja Peric (Croatia), Andreas Christou (Cyprus), Xenophon Hadjikyriacou (Cyprus), Václav Buriánek (Czech Republic), Jan Chládek (Czech Republic), Josef Frýdl (Czech Republic), Petr Novotný (Czech Republic), Martin Slovacek (Czech Republic), Zdenek Špišek (Czech Republic), Karel Vancura (Czech Republic), Ulrik Bräuner (Denmark), Bjerne Ditlevsen (Denmark), Jon Kehlet Hansen (Denmark), Jan Svejgaard Jensen (Denmark), Kalev Jðgiste (Estonia), Tiit Maaten (Estonia), Raul Pihu (Estonia), Ülo Tamm (Estonia), Arvo Tullus (Estonia), Aivo Vares (Estonia), Teijo Nikkanen (Finland), Sanna Paanukoski (Finland), Mari Rusanen (Finland), Pekka Vakkari (Finland), Leena Yrjänä (Finland), Daniel Cambon (France), Eric Collin (France), Alexis Ducousso (France), Bruno Fady (France), François Lefèvre (France), Brigitte Musch (France), Sylvie Oddou-Muratorio (France), Luc E. Pâques (France), Julien Saudubray (France), Marc Villar (France), Vlatko Andonovski (FYR Macedonia), Dragi Pop-Stojanov (FYR Macedonia), Merab Machavariani (Georgia), Irina Tvauri (Georgia), Alexander Urushadze (Georgia), Bernd Degen (Germany), Jochen Kleinschmit (Germany), Armin König (Germany), Armin König (Germany), Volker Schneck (Germany), Richard Stephan (Germany), H. H. Kausch-Blecken Von Schmeling (Germany), Georg von Wühlisch (Germany), Iris Wagner (Germany), Heino Wolf (Germany), Paraskevi Alizoti (Greece), Filippos Aravanopoulos (Greece), Andreas Drouzas (Greece), Despina Paitaridou (Greece), Aristotelis C. Papageorgiou (Greece), Kostas Thanos (Greece), Sándor Bordács (Hungary), Csaba Mátyás (Hungary), László Nagy (Hungary), Thröstur Eysteinsson (Iceland), Adalsteinn Sigurgeirsson (Iceland), Halldór Sverrisson (Iceland), John Fennessy (Ireland), Ellen O'Connor (Ireland), Fulvio Ducci (Italy), Silvia Fineschi (Italy), Bartolomeo Schirone (Italy), Marco Cosimo Simeone (Italy), Giovanni Giuseppe Vendramin (Italy), Lorenzo Vietto (Italy), Janis Birgelis (Latvia), Virgilijus Baliuckas (Lithuania), Kestutis Cesnavicius (Lithuania), Darius Danusevicius (Lithuania), Valmantas Kundrotas (Lithuania), Alfas Pliûra (Lithuania), Darius Raudonius (Lithuania), Robert du Fays (Luxembourg), Myriam Heuertz (Luxembourg), Claude Parini (Luxembourg), Fred Trossen (Luxembourg), Frank Wolter (Luxembourg), Joseph Buhagiar (Malta), Eman Calleja (Malta), Ion Palancean (Moldova), Dragos Postolache (Moldova), Gheorghe Postolache (Moldova), Hassan Sbay (Morocco), Tor Myking (Norway), Tore Skrøppa (Norway), Anna Gugala (Poland), Jan Kowalczyk (Poland), Czeslaw Koziol (Poland), Jan Matras (Poland), Zbigniew Sobierajski (Poland), Maria Helena Almeida (Portugal), Filipe Costa e Silva (Portugal), Luís Reis (Portugal), Maria Carolina Varela (Portugal), Ioan Blada (Romania), Alexandru-Lucian Curtu (Romania), Lucian Dinca (Romania), Georgeta Mihai (Romania), Mihai Olaru (Romania), Gheorghe Parnuta (Romania), Natalia Demidova (Russian Federation), Mikhail V. Pridnya (Russian Federation), Andrey Prokazin (Russian Federation), Srdjan Bojovic (Serbia) , Vasilije Isajev (Serbia), Saša Orlovic (Serbia), Rudolf Bruchánik (Slovakia), Roman Longauer (Slovakia), Ladislav Paule (Slovakia), Gregor Bozič (Slovenia), Robert Brus (Slovenia), Katarina Celič (Slovenia), Hojka Kraigher (Slovenia), Andrej Verlič (Slovenia), Marjana Westergren (Slovenia), Ricardo Alía (Spain), Josefa Fernández-López (Spain), Luis Gil Sanchez (Spain), Pablo Gonzalez Goicoechea (Spain), Santiago C. González-Martínez (Spain), Sonia Martin Albertos (Spain), Eduardo Notivol Paino (Spain), María Arantxa Prada (Spain), Alvaro Soto de Viana (Spain), Lennart Ackzell (Sweden), Jonas Bergquist (Sweden), Sanna Black-Samuelsson (Sweden), Jonas Cedergren (Sweden), Gösta Eriksson (Sweden), Markus Bolliger (Switzerland), Felix Gugerli (Switzerland), Rolf Holderegger (Switzerland), Peter Rotach (Switzerland), Marcus Ulber (Switzerland), Sven M.G. de Vries (The Netherlands), Khouja Mohamed Larbi (Tunisia), Murat Alan (Turkey), Gaye Kandemir (Turkey), Gursel Karagöz (Turkey), Zeki Kaya (Turkey), Hasan Özer (Turkey), Hacer Semerci (Turkey), Ferit Toplu (Turkey), Mykola M. Vedmid (Ukraine), Roman T. Volosyanchuk (Ukraine), Stuart A'Hara (United Kingdom), Joan Cottrell (United Kingdom), Colin Edwards (United Kingdom), Michael Frankis (United Kingdom), Jason Hubert (United Kingdom), Karen Russell (United Kingdom), C.J.A. Samuel (United Kingdom).
 

Status of Populus alba conservation in Europe

Genetic diversity and variation

White poplar has high genetic diversity within populations and low genetic differentiation between populations (Palancean et al., 2018). Roughly 84% of genetic variation is within populations (Uzan Eken et al., 2024). However, the species has a wide distribution, with populations adapted to local climates and environments, creating lots of intraspecific variation (Palancean et al., 2018). Populations of white poplar in riverbank and floodplain forests have been shown to have higher genetic diversity than those elsewhere (Uzan Eken et al., 2024). White poplar is genetically like aspen (Populus tremula), leading to the formation of hybrid zones between the two species and introgression, increasing genetic diversity (Palancean et al., 2018).

Genetic distribution and clustering

White poplar shows moderate geographically related genetic and morphological variation among populations, with northern provenances having large leaves and straight stems while provenances in the warmer and drier Mediterranean region have smaller leaves and curved stems (Palancean et al., 2018). Southern populations also tend to have greater and more diverse genetic diversity. For example, populations in Iberia show local adaptations and regional spatial genetic structuring (Macaya Sanz, 2015; Palancean et al., 2018).

White popular shows some genetic clustering according to geographic distance, and spatial genetic clustering (Uzan Eken et al., 2024). Strong spatial genetic structuring can be the result of low gene dispersal by both seeds and pollen and/or because most trees in a specific area tend to mate with each other (Dering, Rączka, and Szmyt, 2016). In white poplar, clear differences in spatial genetic structuring are observed between male and female plants; this may be because of increased mortality of female plants, which seem to require better conditions to thrive (Dering, Rączka, and Szmyt, 2016).

Gene flow

Pollen of the white poplar can travel up to 100 km by the wind, and its seeds are dispersed by wind and water (Uzan Eken et al., 2024). However, the species is dioecious, and the number of seed sources is half that of a monoecious species (Dering, Rączka, and Szmyt, 2016). However, much of white poplar regeneration occurs vegetatively and clonally, which may increase spatial genetic structuring (Dering, Rączka, and Szmyt, 2016). Vegetative reproduction is common in isolated white poplar populations, potentially having a homogenizing effect in fragmented populations (Guarino et al., 2015; Uzan Eken et al., 2024).

 

The bibliographic review was conducted by James Chaplin of the EUFORGEN Secretariat in August 2024.

Threats

Riparian forests where white poplar grows are under threat from changes in river systems and changes in land use to agriculture (Palancean et al., 2018). White poplar populations in Europe have decreased in size and become fragmented, reducing diversity and adaptive potential, and changing populations’ genetic structure; as such, the species and its genetic resources are now under threat (Palancean et al., 2018; Uzan Eken et al., 2024). The use of poorly adapted reproductive material in efforts to restore riparian forest ecosystems has also increased the risk of genetic erosion (Palancean et al., 2018).

Management

When the goals are long-term gene conservation and maximizing the adaptive potential, dynamic in situ conservation is preferable to ex situ conservation (Palancean et al., 2018). Conservation units should be established throughout the range of the species and include more than one conservation site per river system (Palancean et al., 2018). Buffer zones can be established around restored populations using male trees to reduce introgression of unwanted genetic material (Palancean et al., 2018).

When natural regeneration is not sufficient, supplemental planting can take place. However, white poplar has been commercially produced through clonal selection in various countries. Therefore, origins of provenances must be considered in restoration programmes and seedlings to be used in planting must come from appropriate sources (Macaya Sanz, 2015; Uzan Eken et al., 2024).

 

The bibliographic review was conducted by James Chaplin of the EUFORGEN Secretariat in August 2024.

Genetic Characterisation of Populus alba and its GCUs

Availability of FRM

FOREMATIS

EUFORGEN’s publications

Technical guidelines for genetic conservation and use

Populus alba - Technical guidelines for genetic conservation and use of white poplar

Publication Year: 2018
Author: Palancean, I.; Alba, N.; Sabatti, M.; de Vries, S.M.G.

As a general objective, the conservation of genetic resources should maintain the adaptation potential of species and populations. Static ex situ conservation is a widely applied strategy for short term conservation to preserve genotypes in ex situ collections or genebanks. Dynamic in situ conservation is preferable when the objective is long-term gene conservation and maximization of the adaptive potential of a species. This can be achieved through in situ conservation of native stands (including restoration of stands), long-term breeding programmes or both. Successful in situ conservation of white poplar in Europe primarily depends on the location and protection of its natural habitats.

The conservation units should be distributed throughout the distribution range of the species, preferably including more than one conservation site per river-system. A preliminary assessment of the genetic diversity among adult trees in the candidate populations is recommended to conserve a high amount of diversity and a low number of clonal duplicates. Particular attention must be paid to all practices that have an impact on flowering habit and the regeneration process, which determine the effective population size. Conditions for seed-set and seedling establishment should be optimized. The number of flowering and seeding trees provides a practical approach to assess the effective size of a given population. At least 50 fructifying and unrelated trees are required to keep genetic variation at a satisfactory level within a population. If natural regeneration does not occur successfully in some of the units, then supplemental planting with seedlings from appropriate sources might be carried out.

For restored populations, introgression with unwanted genetic material can be limited by creating a “buffer zone” around the population consisting of local male trees. Active management and evaluation of the restored populations are highly recommended and should include replacement of poorly flowering individuals, corrective thinning, new additions to and from the genebanks, and removal of unsuitable individuals.

As a general objective, the conservation of genetic resources should maintain the adaptation potential of species and populations. Static ex situ conservation is a widely applied strategy for short term conservation to preserve genotypes in ex situ collections or genebanks. Dynamic in situ conservation is preferable when the objective is long-term gene conservation...

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References

Dering, M., Rączka, G., and Szmyt, J. 2016. Sex-specific pattern of spatial genetic structure in dioecious and clonal tree species, Populus alba L. Tree Genetics & Genomes, 12: 70. https://doi.org/10.1007/s11295-016-1028-5

Guarino, F., Cicatelli, A., Brundu, G., Heinze, B., and Castiglione, S. 2015. Epigenetic diversity of clonal white poplar (Populus alba L.) populations: could methylation support the success of vegetative reproduction strategy? PLoS One, 10(7): e0131480. https://doi.org/10.1371/journal.pone.0131480

Macaya Sanz, D. 2015. Population genetic structure of Iberian white poplar (Populus alba L.): the role of mating system, hybridization and demographical history. PhD thesis, Universidad de Valladolid, Spain.

Palancean, I., Alba, N., Sabatti, M., and de Vries. S.M.G. 2018. EUFORGEN Technical Guidelines for genetic conservation and use for white poplar (Populus alba). Barcelona, Spain, European Forest Genetic Resources Programme (EUFORGEN). 6 pages.

Uzan Eken, B., Kirdok, E., Velioglu, E., and Ozden Ciftci, Y. 2024. Genetic variation in white poplar (Populus alba L.) populations as characterized by SSR markers. Turkish Journal of Botany, 48(1): 2. https://doi.org/10.55730/1300-008X.2790

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