Fifty years of vegetation and environmental change in the Scottish Highlands

Long-term data are valuable for detecting changes in vegetation composition, and investigating how vegetation is responding to environmental change. We use a range of approaches to quantify, characterise and interpret vegetation change in upland plant communities of the Scottish Highlands by comparing two datasets, collected in 1956-58 and 2007-08, on the species composition of representative plots in major vegetation types in the North-West Highlands and the East Central Highlands. Firstly, we validate the methodology used for relocating plots that were not permanently marked, by showing that temporal change is greater than local spatial heterogeneity in the vegetation. The results show evidence of biotic homogenisation in the vegetation, manifested through declining plant diversity and an increase in generalist species, particularly graminoids, at the expense of specialists, particularly dwarf-shrubs, lichens and forbs. Climate change in the form of increased oceanicity, and grazing were found to have been important in driving these changes, whereas nitrogen deposition had a smaller effect. These data were also applied to two issues in nature conservation management, showing that protected area status had no effect on the magnitude of vegetation change, and that indicator species of the key drivers of change could be identified. Finally, we show how long-term vegetation change data can be used in hypothesis formulation for experimental work, by carrying out an ex-situ manipulative experiment on an important upland graminoid species, Trichophorum germanicum. This thesis incorporates examples of the wide range of ecological questions and analytical approaches that can be investigated through revisitation studies.EThOS - Electronic Theses Online ServiceGBUnited Kingdo