| Summary: | During the past 150 years the amount of CO2 in the atmosphere, [CO2], has increased severely, mostly due to an increase in the burning of fossil fuels and land-use changes. It is predicted that [CO2] will have doubled in the end of this century. Future temperature (T) is also expected to increase due to climate forcing following the increase in [CO2]. In this experiment we studied the effect of elevation of [CO2] and T on needle morphology and shoot growth. It was made by using whole-tree chambers around mature trees. In this research the main goal was to find out what effects elevated [CO2] and T had on specific needle area (SNA), needle density, needle length and width, annual shoot length and shoot needle area at different heights in 40-year-old field-grown Norway spruce trees at the Flakaliden experimental site in northern Sweden. The present study was a part of a larger experiment examining the long-term morphological and physiological responses of the trees. Elevated T significantly increased SNA (P<0.04) and shoot length (P<0.02). No significant treatment effects or interactions between [CO2] and T were found for needle area density, needle density, average needle length or width. Most morphological parameters changed significantly with height in the tree. From the present study it can be concluded that elevated T can possibly increase needle area, through significant changes in annual shoot lengths. Elevated [CO2] is, however, not expected to have a direct effect on needle morphology or needle area of Norway spruce and no interactive changes are expected between elevated [CO2] and T. It is important to note that needle morphology changes more with height in the tree than due to changes in environmental parameters, such as temperature and CO2. When comparing different treatments, care has to be taken that needles from comparable sites within tree canopies are used. Skógar heimsins leika stórt hlutverk í kolefnishringrásinni. Undanfarin 150 ár hefur magn koldíoxíðs aukist verulega í andrúmsloftinu ...
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