The aim of this thesis was to investigate the effects of elevated [CO<SUB>2</SUB>] and varying nutrient supply rates on the growth, phenology and physiology of Sitka spruce (<I>Picea sitchensis </I>(Bong.) Carr.).Two approaches were taken both using open top chamber facilities to fumigate seedling with either ambient (355 <I>μ</I>mol mol<SUP>-1</SUP> Co<SUB>2</SUB>) or elevated (700 <I>μ</I>mol mol<SUP>-1</SUP> CO<SUB>2</SUB>). Firstly, a long term study on the direct impact of elevated [CO<SUB>2</SUB>] was undertaken, this experiment ran for three consecutive years. Comparisons between responses obtained after one and three years exposure to elevated [CO<SUB>2</SUB>] were made. In addition, the impact of growing seedlings in OTCs <I>per se</I> was also investigated. Secondly, a study was conducted into the interaction between [CO<SUB>2</SUB>] and nutrient supply rate on growth, phenological and physiological responses. The effects of OTCs were also included in this experiment. Biomass accumulation was always enhanced by elevated [CO<SUB>2</SUB>] when nutrients were not limiting. Biomass stimulation as a result of elevated [CO<SUB>2</SUB>] was 16 and 37 % for seedlings with a foliar [N] of 1.9 and 2.4 % respectively. However, there was no enhancement at a foliar [N] of 0.9 %. A similar result was also observed in the long term study. There was no significant chamber effect on biomass but seedlings growing inside OTCs were 25 % taller. Biomass allocation was affected by [CO<SUB>2</SUB>], nutrient supply rate, growth inside OTCs and experimental duration. The amount of biomass allocated to roots was increased by elevated [CO<SUB>2</SUB>] and decreasing nutrient supply rates, with those seedlings receiving elevated [CO<SUB>2</SUB>] and low-N supply rates having the highest R/S ratios. Growth inside OTCs reduced the amount of biomass allocated to roots. Seedlings receiving elevated [CO<SUB>2</SUB>] and low nutrient supply rates had smaller amounts of biomass allocated to stems. Total leaf area and mass were both increased by elevated [CO<SUB>2</SUB>] and increasing nutrient supply rate but there was no significant effect of elevated [CO<SUB>2</SUB>] on specific leaf area, leaf area ratio or leaf mass ratio. Elevated [CO<SUB>2</SUB>] significantly affected bud phenology, delaying budburst and advancing budset, thereby reducing the growing season of seedlings with foliar [N] of 2.0 % or below. Increasing nutrient supply rates lengthened the growing season <I>per se</I>. Phenology of seedlings with a foliar [N] of 2.4% were not affected by elevated [CO<SUB>2</SUB>]. There was a large clonal variation in the phenological response to [CO<SUB>2</SUB>] and the effect of OTC was bigger than that of [CO<SUB>2</SUB>]. The effect of elevated [CO<SUB>2</SUB>] and climatic warming on spring frost damage was modelled and future risks of damage were predicted to decrease.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:659792 |
| Date | January 1997 |
| Creators | Murray, Maureen B. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/11206 |
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