Buffer strips alongside watercourses are now a widely accepted method of reducing nutrient and sediment run-off from agricultural land thereby improving water quality and meeting policy goals. However, this change in land use may have consequences for riparian biodiversity which have yet to be fully understood. This study investigated the impact of buffering on various aspects of biodiversity by comparing three types of margins in three river catchments in north east Scotland. Margins were categorised as unbuffered (open and unfenced), buffered (fenced-off vegetated) and wooded (long established woody vegetation - fenced and unfenced). Components of biodiversity studied included vegetation patterns, and the abundance, diversity, movement and assemblage composition of ground-dwelling arthropods focussing primarily, though not exclusively, on ground beetles (Coleoptera, Carabidae). This study further considered management options which may improve or enhance biodiversity. Evidenced changes in vegetation were associated with soil parameters (including decreasing pH), channel morphology, decreasing light availability and tree canopy cover, and bryophyte abundance along a successional gradient from unbuffered-buffered-wooded sites. Buffered and wooded sites showed lower activity density and species richness of ground beetles, but while one measure of functional diversity was high for wooded sites, buffered sites were found to have significantly lower values. Both species and trait assemblage structure of ground beetles were influenced by soil and vegetation, but also by features of buffer strip design such as width, length and age. Active management of sites through grazing or cutting increased ground beetle abundance, particularly hygrophilous species, but did not affect diversity. Radiotracking showed increased movement of ground beetles was correlated with intensity of grazing. Few truly riparian plant or arthropod species were identified indicating the process of buffering essentially 'terrestrialises' the riparian margins. The presence of a tree canopy layer appears to be the key instigator of change in soil conditions with vegetation and arthropods responding accordingly. Therefore planting and maintaining trees in buffer strips could be crucial to ensuring that functional diversity and associated ecosystem services are maintained. Active management through grazing or cutting could help in this regard. The results from this study suggest that rather than buffering all riparian margins within catchments, it is fundamentally important for biodiversity to maintain a mosaic of different successional stages and a diversity of habitats.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:606448 |
| Date | January 2013 |
| Creators | Stockan, Jennifer A. |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=211222 |
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