The aim of this thesis is defined by the title, and two experimental approaches were used to investigate different aspects of the effect of elevated [CO<SUB>2</SUB>] on Sitka spruce; firstly the long term effect on mature tissue using branch bags and secondly, the interaction between [CO<SUB>2</SUB>] and nutrient supply rate on the growth and physiology of seedling trees. Six branches of six 16 year-old Sitka spruce trees were continuously exposed to elevated [CO<SUB>2</SUB>] (700 μmol mol<SUP>-1</SUP>) for four years. Branch growth, shoot numbers, needle size, stomatal density, nutrient and carbohydrate concentration, photosynthesis and stomatal conductance were measured throughout the experiment. There was no effect of elevated [CO<SUB>2</SUB>] on the growth of the branches or needles, or on the nutrient or carbohydrate concentrations of needles. Neither was there evidence for an acclimation of photosynthesis or stomatal conductance to growth in elevated [CO<SUB>2</SUB>] in current year needles. However, there was some down-regulation of photosynthesis in one-year old needles coincident with an increase in soluble carbohydrate concentration. In a second experiment one-year old seedlings were re-potted into sand and grown for eight months in open-top chambers in either ambient or 700 μmol mol<SUP>-1</SUP> [CO<SUB>2</SUB>]. They were supplied with nutrients at two rates: a high rate designed to permit maximum growth rate, and a low rate 1/10 the high rate. Growth was measured each week and six harvests were made during the experiment. A purpose built whole-tree gas exchange system was used to measure independently above and below ground CO<SUB>2</SUB> fluxes over 24 hours. Shoot photosynthesis responses to [CO<SUB>2</SUB>] and needle nutrient and carbohydrate concentrations were also measured. Elevated [CO<SUB>2</SUB>] enhanced growth and increased allocation to roots at both high and low nutrient supply rates, but growth enhancement was larger at the high nutrient supply rate.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:641353 |
| Date | January 1997 |
| Creators | Barton, Craig V. M. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/10744 |
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