1. Climate change is predicted to negatively impact ecosystems globally. Freshwaters are particularly susceptible, due to thermal and hydrological sensitivity and poikilothermic fauna. Such change may ultimately imperil ecosystems service provision. Adaptation schemes that limit ecological and economic impacts are therefore widely advocated. The major management action recommended for rivers is restoration of “buffer strips” of riparian tree cover, which can lower stream water temperatures, and should therefore protect thermally sensitive species, including economically important salmonid fish (Family: Salmonidae). 2. Despite thermal consequences being well-quantified, community-wide biotic responses to restoration remain unexplored. Such ecological consequences may ultimately govern the efficacy of this measure in protecting focal species, but there is limited evidence available from which to predict restoration outcomes and inform management efforts. 3. Using 24 upland streams, this thesis assessed ecological consequences of differential catchment tree cover on stream communities. Using surveys and experimentation, the project assessed the role catchment afforestation in mediating the importance of terrestrial resource subsidies to stream food webs, structuring macroinvertebrate communities, and supporting salmonid fish. 4. Several lines of evidence indicated that wider catchment tree cover controls the functional composition of stream communities, by mediating availability of terrestrial resources. However, buffer strips did not approximate the effects of wider broadleaf forest, and supported communities that were functionally indistinguishable from streams draining unafforested moorland. Unexpectedly, catchment broadleaf cover did not ultimately affect salmonid populations, contrary to expectations. 5. In combination, these results contribute to the understanding of land use effects on stream communities, and provide clear evidence needed to guide future management efforts. These findings suggest two distinct adaptation options: restoration of buffer strips should be able to confer benefits to fish populations, by offsetting thermal impacts without jeopardising food availability. However, re-instatement of wider broadleaf forest could potentially re-establish woodland stream communities.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:590365 |
| Date | January 2013 |
| Creators | Thomas, Stephen Michael |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/57732/ |
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