Masters of Science, Imperial College London, 2012
A re-assessment of the effects of grazing pressure in structuring community composition of Carex-Racomitrium heath on Glas Maol
Context
This study undertook to re-assess permanent plots and grazing cages on Glas Maol, a Scottish Munro on the border between Aberdeenshire and Angus, to explore how grazing-sensitive and grazing-tolerant species in Carex-Racomitrium heath respond to a decrease in grazing pressure.
Aim and Methods
Carex-Racomitrium heath is a montane habitat found throughout the uplands of northern Europe. However, it has experienced a substantial decline in its UK extent during the past century and is now almost absent south of the Scottish uplands. Although considered a species poor habitat, it is home to a number of montane species which are considered rare in their UK range, such as the migratory dotterel (Charadrius morinellus). The cause of the habitat’s decline is thought to be linked to increases in grazing pressure, primarily by sheep, and high nitrogen deposition, which occurredwithin the last 50 years.
Results & Conclusion
Analysis of dung counts, vegetation cover, and biomass data revealed that the grazing-sensitive moss R. lanuginosum only showed a modest increase in cover, suggesting its recovery, as suggested elsewhere, may be impeded by sustained levels of high nitrogen deposition. Graminoids and other vascular plants either appeared to significantly increase cover or show nochange, suggesting that they may, at least initially, benefit from the decreased herbivory. Elsewhere, a substantial decrease in Dicranum moss, a species commonly found replacing Racomitrium when grazing is high, may indicate the loss of a competitive advantage related to herbivore tolerance or may be caused by another factor not explained by this study.
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