Late Autumn Frost Resistance of Twelve North European Provenances of Quercus Species

Abstract

Twelve north European oak provenances [11 Quercus robur L. and one Quercus petraea (Matt.) Liebl] were tested for late autumn frost hardiness using visual methods and measurements of relative conductivity. Tissue from buds and twigs from 2-yr-old seedlings was used. The test was carried out in November and December. Temperatures between −20 and −32°C were necessary to cause serious damage to tissue, even when tissues were tested only a few weeks after leaf fall. Visual methods proved to be fast and could be applied in practical test applications. Estimation of twig viability was found to be a more reliable variable than bud assessment, which appears to be sensitive and not necessarily related to plant mortality. Relative conductivity is a more labour-intensive method and requires some technical equipment, but it provided the most consistent statistical results. Strong correlation between the visual methods and relative conductivity was demonstrated. Provenances originating from locations close to the Atlantic ocean (The Netherlands, the UK, Denmark and Norway) tended to be less frost resistant than more continental provenances (from Norway, Sweden, Finland and Poland). Frost tolerance was correlated with budset, but not with growth of the provenances. The results confirm the existence of specific ecotypes and suggest a high potential for adaptation in Q. robur.

Keywords:

• Electrolyte leakage
• frost hardiness
• provenance testing
• Quercus petraea
• Quercus robur
• relative conductivity

Acknowledgments

Thanks are due to Charlotte Bang Pedersen for executing the practical aspects of the study. The project was financed by the Royal and Veterinary Agricultural University, the Forest and Nature Agency and the Danish Forest and Landscape Research Institute. Thanks to Geert Kranenburg, Alterra, The Netherlands; Bill Brown, Forest Research Branch UK; Pekka Vakkari, Metla, Finland; Armin König, Grosshansdorf, Germany; and Henrik Fober, Kornik, Poland, for providing seeds.