Semi-natural upland plant communities in the U.K. characterised by calcifugous grasslands and montane dwarf shrub communities, with low N requirements, are thought to be particularly vulnerable to the effects of N pollution. N deposition can be enhanced at high altitude sites <I>via</I> cloud droplet deposition and the seeder-feeder effect and the consequences of this for upland vegetation were investigated. Sampling of a range of upland plant species on altitudinal transacts at sites of known N deposition showed that the foliar N concentration increased with altitude and appeared to reflect the enhancement of N deposition with altitude at these sites. Transplant experiments with <I>Nardus stricta</I> in pots and turves showed that although this species reflected N deposition to some extent, the relationship was modified by temperature. This should be taken into account in any attempt to biomonitor N deposition using higher plants. A two year experiment in which upland plant species were misted with N at a rate typical of more polluted sites in the U.K. (60 kg N ha<sup>-1</sup> yr<sup>-1</sup>) produced increased root and shoot tissue N concentrations in all species and differential effects on growth and nutrient allocation, and flowering. The dwarf shrubs <I>Vaccinium vitis-idaea</I> and <I>Erica cinerea</I> showed a decrease in root:shoot ratio as a consequence of increased shoot growth, as did the sedge <I>Eriophorum vaginatum</I>, but in the grass <I>Nardus stricta</I> both root and shoot growth were stimulated with the result that there was no change in root:shoot ratio. The magnitude of the response of foliar N concentration to N deposition was species specific and greatest in slow growing species, such as dwarf shrubs, which showed preferential allocation of N to the shoots.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:320769 |
| Date | January 1996 |
| Creators | Hicks, William Kevin |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU083081 |
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