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Title: A wetland framework for impact assessment at statutory sites in England and Wales
Author: B.D. Wheeler
Author: S. Shaw
Author: K. Tanner
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1645, Representation ID: 610, Object ID: 2752
The essence of this project was to combine and review ecological and hydrogeological data sources for about 200 wetland sites (including over 1,500 stand samples). At the core of the Framework was the identification of the main distinctive wetland habitats. A bottom-up approach, based on an analysis of field data from wetlands, was used to detect the recurrence of sets of conditions and species and to use these as the foundation for a classification. The main procedures used for data analysis were multivariate classification and cluster analysis, in particular canonical correspondence analysis (CCA) and Ward’s method. An ecohydrological framework was developed in which habitats were defined according to a combination of three base-richness (pH) categories, three fertility categories and twenty wetland water supply mechanisms (WETMECs), plus sub-types. WETMECs were one of the most important outcomes of the study, in essence offering a summary of how wetlands work hydrologically. Certain WETMECs are associated with specific hydrogeological and landscape contexts. Analysis of these relationships showed why some habitats and vegetation types are intrinsically rare and confined to specific locations. A key finding of the study was the importance of top-layer conditions (the wetland substratum itself) in regulating the water environment and character of the habitat. Part 1 introduces aspects of the ecohydrology and classification of wetlands, outlining the report’s main concepts. It describes the complex relationships between wetland vegetation and environmental conditions, hydrodynamics, succession and development. Part 2 outlines the main approaches to the project and data analysis procedures, and describes a typology which forms the core of the Wetland Framework. This typology relates primarily to types within wetlands rather than types of wetlands. Two main sets of units are used: ‘wetland water supply mechanisms’ (WETMECs) and ‘ecological types’ (permutations of water base-richness (pH) and soil fertility categories). Twenty WETMECS are identified and described. Part 3 examines the relationships between the occurrence and composition of selected wetland plant communities in relation to hydrological, ecological and management variables. These communities include those considered particularly important under EC Habitats Directive. The main environmental conditions under which they occur are described, with comments on their perceived vulnerability to dehydration, eutrophication and management practices.
Publisher: Environment Agency
Subject Keywords: EcologyHydrogeologyHydrologyWetlandsVegetationHydrologyFensBogsMacrophytesEutrophication
Extent: 755
Total file downloads: 310

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