The Functional Ecology of Euhydrophyte Communities of European Riverine Wetland Ecosystems

Abernethy, Victoria Jane (1994) The Functional Ecology of Euhydrophyte Communities of European Riverine Wetland Ecosystems. PhD thesis, University of Glasgow.

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Abstract

To investigate the functional ecology of euhydrophyte communities in European riverine wetlands six study catchments were chosen. Of these, four were the target sites of a European Community research project investigating the 'Functional Analysis of European Wetland Ecosystems' to which this project was allied. These sites cover a range of climatic conditions from eu-oceanic to semi-arid. Within the six catchments, 37 sampling sites were located in total. Sampling sites exhibited a range of flow velocities, trophic states, water depths and water qualities. During 1992 and 1993 a field survey involving repeated visits to all the sites was conducted. At each site, euhydrophyte plant communities were recorded, other plant species present below the water line were recorded, a suite of environmental variables was assessed, and morphological traits measured on selected species. Sites were visited between two and eight times over the two year period. A total of 54 euhydrophyte species were recorded. TWINSPAN was used to classify sites by their constituent species, and was found to strongly reflect geographical location. Canonical Correspondence Analysis showed that no single environmental factor was controlling community composition, although the most influential of those measured were flow, conductivity, water phosphate levels, sediment texture, depth, sediment organic matter, level of light received at the substrate and pH. Species were ranked along selected gradients. An extensive review of research published on euhydrophytes was used to compile a table of euhydrophyte traits and assign to them a fuzzy coded value. These included morphological, life history, physiological and regenerative traits. Traits concerned with the established phase of the life cycle were used to classify euhydrophytes into six groups, termed functional groups, using non-hierarchical clustering methods. The homogeneity of these groups was investigated using a Principal Components Analysis. A linear discriminant analysis provided equations, using a subset of the original traits, to predict functional group membership for new species. Morphological traits measured in the field survey were tested for their value as indicators of functional group, but were found to be poor descriptors. Glasshouse experiments on established phase plants were used to investigate the response of selected species to the pressures of competition, stress and disturbance. Species responses were measured in terms of total biomass, plant length and biomass allocation. The results could be used to improve the knowledge of species strategy sensu Grime (1979). Regenerative phase traits, taken from the published literature, were also used to classify euhydrophyte species using a non-hierarchical clustering method. Examination of these groups showed them to be quite heterogeneous in composition. Comparison with groupings achieved using established phase traits only and using established and regenerative phase traits in combination, showed a grouping from established phase traits to be most homogenous. This was attributed to the poor data available on regenerative phase traits. Few strong correlations existed between established and juvenile phase traits. Two aspects of regenerative biology were investigated experimentally. The rooting rate of fragments did not show any correlation with flow velocity, stress index or disturbance index. The seed banks from a range of sites were quantified using seedling emergence techniques. Flooding depth had a severe effect on the numbers of seedlings emerging and on species richness. A permanent seed bank was demonstrated for a number of euhydrophytes. The contribution of the seed bank to population maintenance in euhydrophytes was found to be small, but potentially critical, particularly in seasonal water bodies or following natural catastrophe, or artificial disturbance. The seed bank of permanently submerged sites was higher than suggested from previous studies and may have potential for wetland restoration. The contribution of each functional group was used to classify sites into Functional Vegetation Types (FVTs). Predictive equations were constructed, using linear discriminant analysis, to allow new sites to be assigned to an FVT on the basis of their functional group composition. These were found to be unrelated to geographical location. The FVTs showed recognisable associations to particular habitat conditions. In many sites a variety of the functional groups were present, possibly indicating within-site heterogeneity of environmental conditions. A field survey was carried out in the Czech and Slovak Republics in 1994. Fifteen sites were visited and data on community composition, euhydrophyte morphological traits and environmental variables was collected. This was comparable to the 1992/93 survey and was used as a test data set. Morphological traits measured in the field were again found to be inadequate indicators of functional group. The relationship of functional groups to environmental gradients described from the original survey was largely supported. The necessity for collection of comparable data on euhydrophyte traits, particularly regenerative traits is emphasised.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Kevin Murphy
Keywords: Ecology
Date of Award: 1994
Depositing User: Enlighten Team
Unique ID: glathesis:1994-75337
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 20:49
Last Modified: 19 Nov 2019 20:49
URI: http://theses.gla.ac.uk/id/eprint/75337

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