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Title: Patch-specific disturbance in steep streams : a geomorphic framework
Author: Oldmeadow, David F.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2005
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In this thesis I propose a framework to characterise the size and spacing of refugia in steep streams, based on a geomorphological classification of the streambed. Focusing primarily on four aspects, the physical attributes, particle movement and invertebrate assemblage associated with each morphological patch, and the hydraulic influence on invertebrate drift and settlement, I test the response of invertebrates to floods of different magnitudes on each patch type, Loose, Degraded and Structured. Patch type differed in sedimentological character. A strong association of invertebrate assemblage with patch type was detected. Distribution of some species was restricted to Structured patches. Contribution of Structured patches to invertebrate abundance is much greater than their areal extent suggests. I hypothesised that the hydraulic environment of a Structured patch, step, promotes drift settlement. Baetis rhodani and Simulium sp show no change in drift and settlement over a step, despite a large increase in velocity and turbulence. Hydropsyche pellicudula and Ecdyonurus torrentis drift further. The hydraulic environment of the step constrained the settlement and distribution of E. torrentis. The difference in drift response between the mayfly species is due to a complex interaction between behaviour and hydraulic environment. I contend this is driven by body morphology. A net loss occurred on all patch types during after flooding, although the assemblage on Structured patches was more resistant. Species-specific response was complex, and not related to particle movement. Loose patches, despite complete mobilisation, accumulated individuals, but this varied between flood events. Particle movement was only weakly linked with the processes responsible for the post-flood pattern of invertebrates. The patch classification does not discriminate on the basis of these processes, and may not provide a useable framework to characterise size and spacing of refugia in steep streams.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available