Corresponding Author

E-mail address: martin.mullett@forestry.gsi.gov.uk

http://orcid.org/0000-0002-6013-0347

Forest Research, Farnham, Surrey, UK

Correspondence

Martin Mullett, Forest Research, Alice Holt Lodge, Farnham, Surrey, UK.

Email: martin.mullett@forestry.gsi.gov.uk

Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Tartu, Estonia

Instituto Nacional de Investigação Agrária e Veterinária, Oeiras, Portugal

Russian Research Institute of Floriculture and Subtropical Crops, Sochi, Krasnodar region, Russia

Forest Research Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria

Instituto Nacional de Investigação Agrária e Veterinária, Oeiras, Portugal

Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Tartu, Estonia

Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Tartu, Estonia

Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, Tartu, Estonia