Despite the existence of an extensive literature on the morphology, autecology, utilisation, and eradication of Pteridium aquilinum, relatively little research has been done on the Pteridium-grassland ecosystem of Scottish rough grazings. This study is a systematic and semi-quantitative investigation of the influence of Pteridium competition on its associated vegetation and soils, based on field and soil laboratory techniques. It is postulated that the differential response of moorland species to varying degrees of bracken dominance and the modification of soil morphological and chemical characteristics by the dominant plant species is partly responsible for the well-known association of Pteridium aqutlinum with Festuca-Agrostis - brown forest soil ecosystems. This hypothesis is tested in the field in three contrasting upland environments in Scotland. The influence of varying densities of bracken on three facets of the vegetation - soil association is examined: (I) the characteristic particularly the biomass, of the ground vegetation as a whole (2) the species composition of the herb layer and (3) the morphological characteristics of the soil. The degree of dominance of bracken is defined in a semi-quantitative manner and correlated with indices of the vigour of the ground vegetation and its species composition. A classification of common dry moorland species, according to their response to Pterldlum competition is produced. The association of Ptertdlum aqutltnum with soils of brown forest soil morphology is studied and the importance of the rhizome system In modifying the physical characteristics of the soil and the distribution of organic matter in the profile demonstrated. The tendency of bracken to modify the morphological characteristics of podsolised soils is shown. Subsequent laboratory analysis substantiates the morphological evidence of the relationship between Pteridium-dominated vegetation and soil type. By revealing the differences in nutrient status between bracken soils and podsolised heath soils and the seasonal variation In nutrient levels, the efficiency of Pteridium in cycling nutrients through the ecosystem Is suggested. The ability of Pterldium to release phosphate from inorganic sources in the soil is demonstrated by laboratory experiment, anomalously high available phosphate levels in the subsoil of bracken soils having been revealed by routine analysis. Laboratory experiment also suggests that the modification of iron pans by Pteridium rhizomes may have a chemical as well as a physical component. The evidence of Pteridium's Influence on vegetation and soil characteristics allows preliminary comment to be made on the ecological significance of bracken eradication schemes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:465843 |
| Date | January 1977 |
| Creators | Mitchell, Joan |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/5359/ |
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