Poster: Global change

Abs # 18: Dehardening of mountain birch ecotypes at elevated winter temperatures

Presenter:	Taulavuori, Kari , kari.taulavuori@oulu.fi
Authors	Taulavuori, Kari  (A)   Taulavuori, Erja  (A)   Skre, Oddvar  (B)   Nilsen, Jarle  (C)   Igeland, Bernt  (C)   Laine, Kari  (A)
Affiliations:	(A): University of Oulu, Department of Biology (B): Norway Forest Research Institute, Bergen (C): University of Tromsa, Department of Biology

The aim was to elucidate the effects of elevated winter temperatures on the dehardening process of mountain birch (Betula pubescens ssp. czerepanovii) ecotypes and to evaluate their susceptibility to frost damage under warming climate conditions. Ecotypes from 60-71 degrees N latitudes and 20-750 m altitudes were grown in northern Norway (70 degrees N)and subjected to simulation of the photoperiod in southern Norway (60 degrees N) by artificial illumination from September onwards. In November, the seedlings were transported to the south (60 degrees N) to overwinter at ambient or 4 degrees Celsius above ambient temperatures. Frost hardiness and lipid peroxidation were determined during January-April. The higher winter temperatures accelerated dehardening, and there were significant differences between the ecotypes. Among tree individuals of southern origin, the alpine ecotype exhibited the most rapid rate of dehardening, while the oceanic type showed the slowest rate. Lipid peroxidation supported the above findings. Since temperature elevation was unequal for the ecotypes with respect to climatic change, the frost hardiness results were normalized to obtain an equal +4 degrees Celsius temperature rise. The risk of frost injury seemed to be lowest in the northernmost ecotypes under the above temperature elevation, obviously due to their adaptation to a wider temperature range.