Climatic control of bud burst in young seedlings of nine provenances of Norway spruce
Gunnhild Søgaard (1, 2), Øystein Johnsen (3), Jarle Nilsen (4) and Olavi Junttila (4)
1. Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway / 2. Corresponding author () / 3. Norwegian Forest and Landscape Institute, P.O. Box 115, NO-1431 Ås, Norway / 4. Department of Biology, University of Tromsø, NO-9037 Tromsø, Norway / Received April 10, 2007; accepted July 2, 2007; published online December 3, 2007
Summary
Detailed knowledge of temperature effects on the timing of dormancy development and bud burst will help evaluate the impacts
of climate change on forest trees. We tested the effects of temperature applied during short-day treatment, duration of short-day
treatment, duration of chilling and light regime applied during forcing on the timing of bud burst in 1- and 2-year-old seedlings
of nine provenances of Norway spruce (Picea abies (L.) Karst.). High temperature during dormancy induction, little or no chilling and low temperature during forcing all delayed
dormancy release but did not prevent bud burst or growth onset provided the seedlings were forced under long-day conditions.
Without chilling, bud burst occurred in about 20% of seedlings kept in short days at 12 °C, indicating that young Norway spruce
seedlings do not exhibit true bud dormancy. Chilling hastened bud burst and removed the long photoperiod requirement, but
the effect of high temperature applied during dormancy induction was observed even after prolonged chilling. Extension of
the short-day treatment from 4 to 8 or 12 weeks hastened bud burst. The effect of treatments applied during dormancy development
was larger than that of provenance; in some cases no provenance effect was detected, but in 1-year-old seedlings, time to
bud burst decreased linearly with increasing latitude of origin. Differences among provenances were complicated by different
responses of some origins to light conditions under long-day forcing. In conclusion, timing of bud burst in Norway spruce
seedlings is significantly affected by temperature during bud set, and these effects are modified by chilling and environmental
conditions during forcing.
