Biotic homogenization of upland vegetation: patterns and drivers at multiple spatial scales over five decades
Article first published online: 2 FEB 2012
© 2012 International Association for Vegetation Science
Journal of Vegetation Science
Volume 23, Issue 4, pages 755–770, August 2012
How to Cite
Ross, L. C., Woodin, S. J., Hester, A. J., Thompson, D. B.A., Birks, H. J. B. (2012), Biotic homogenization of upland vegetation: patterns and drivers at multiple spatial scales over five decades. Journal of Vegetation Science, 23: 755–770. doi: 10.1111/j.1654-1103.2012.01390.x
- Issue published online: 3 JUL 2012
- Article first published online: 2 FEB 2012
- Manuscript Accepted: 16 DEC 2011
- Manuscript Received: 15 MAR 2011
- CASE studentship with Scottish Natural Heritage
- Ellenberg indicator values;
- environmental change;
- multivariate analysis;
- re-sampling study;
- species attributes
Is there evidence for biotic homogenization of upland vegetation? Do the magnitude and nature of floristic and compositional change vary between vegetation types? What can be inferred about the drivers responsible for the observed changes?
Upland heath, mire and grassland communities of the northwest Highlands of Scotland, UK.
We re-survey plots first described in a phytosociological study of 1956–1958 to assess the changes in plant species composition over the last 50 yr in five major upland vegetation types. Using a combination of multivariate analysis, dissimilarity measures, diversity metrics and published data on species attributes; we quantify, characterize and link potential drivers of environmental change with the observed changes in species composition.
Grassland and heath vegetation declined in species richness and variation in community composition, while mires showed little change. Previously distinct vegetation types became more similar in composition, characterized by the increased dominance of generalist upland graminoids and reduced dwarf-shrub, forb and lichen cover, although novel assemblages were not apparent. Species with an oceanic distribution increased at the expense of those with an arctic-montane distribution. Temperature, precipitation and acidity were found to be potentially important in explaining changes in species composition: species that had undergone the greatest increases had a preference for warmer, drier and more acidic conditions.
The vegetation of the northwest Scottish Highlands has undergone marked biotic homogenization over the last 50 yr, manifested through a loss of various aspects of diversity at the local, community and landscape scales. The magnitude of change varies between vegetation types, although the nature of change shows many similar characteristics. Analyses of species attributes suggest these changes are driven by climate warming and acidification, although over-grazing may also be important. This study highlights the importance of the link between the loss of plant diversity and homogenization at multiple scales, and demonstrates that boreal heath communities are particularly at risk from these processes.