Geomorphic types

There have been many different approaches to wetland classification but, as discussed previously in section 1.262, a classification that aids management through a link to wetland fimctioning is needed. Therefore categories within the classification need to be both easily recognisable and key

structural elements that have a direct bearing on wetland functioning. Section 2.2 identified that a determination of potential fimctipning can be achieved through the identification of the hydrologie and geomorphic structural elements. Therefore, it is argued that categories within a fimctional classification should focus on the geomorphic and hydrologie elements of wetlands within Europe. The following two sections discuss other approaches to wetland classification, different approaches to geomorphic and hydrologie categorisation and conclude that, for a wetland classification of Europe, the use of geomorphic and hydrologie criteria the most appropriate.

Vegetation described by the dominant life form or community type has been traditionally used as

a criteria for the classification of wetlands (Cowardin et a l, 1979). Wetlands have often been

included within vegetation descriptions and classifications that extend beyond wetland areas. For example, wetland habitat types such as ‘Sea marshes’ in Ellenberg’s (1988) description of the vegetation ecology of Central Europe or ‘Tall Herb Fens’ in Rodwell’s (1998) British Plant Communities. The classification of plant communities is important for detailed investigation of wetland areas but a classification solely based on vegetation is limited because it makes no link to functioning and takes limited account of management. Even classifications which consider the

topographic location of a wetland, such as Cowardin et a l (1979), are reliant on a description of

the dominant life form and do not make a link to wetland functioning. Within Europe the alteration of wetland habitats and communities is severe so a category of classification that is management neutral is required so that the functioning of a wetland is recognised.

The wetland classifications discussed in section 1.262 all have an element of morphological topography within them but few, if any, make a link between the landscape setting and the functioning of the wetland. Brinson (1993) makes this link by developing a classification where the relationship between hydrogeomorphology and fimctioning is recognised. To ensure that the classification of European Wetlands recognises wetland functioning then the geomorphology of a wetland has to taken into account.

Geomorphology is the science of landforms (Thombury, 1954). Geomorphological study

attempts to understand the maintenance and change of landforms through observing contemporary processes and to deduce, from erosional and depositional features, the sequence of

historical events that have shaped the landscape (Chorley et al, 1984). Using geomorphic

criteria for classification does not simply describe the shape or type of landscape but provides an understanding of how that landscape was formed and what geomorphic processes may occur

there at present. This understanding of the landscape setting for a wetland is vital if a link to ecosystem functioning is to be made.

The advantages of using geomorphic criteria for wetland classification can be summarised as being;

1. Landscape and geomorphic processes such as soil development, erosion and deposition are fundamentally linked to wetland genesis and development.

2. Geomorphic settings are easily recognisable in the field and from basic data sources such as topographical maps.

3. Geomorphology is a key structural element that determines wetland functioning through:

a) Processes such as erosion and deposition, that are directly related to

geomorphology, interacting with other structural elements.

b) Providing a control on the interaction of ecosystem processes and structure

through the landscape setting and profile.

Disadvantages to using geomorphic criteria for wetland classification are:

1. Limited account of management alteration to a wetland and therefore functioning is taken. 2. That there is no description of vegetation or habitat type which can affect processes such as

soil development, erosion and deposition.

Although the use of a geomorphic criteria for wetland classification takes limited account of management and does not describe plant communities and habitat types for the level of assessment performed by the fimctional classification of European wetlands this detail of information is not required. Information concerning management and plant communities is only needed if a determination of actual functioning is required. The functional classification provides a description of potential functioning, for which geomorphic criteria are vital, but if a more detailed assessment is needed then another technique such as assessment procedures should be sought.

Detailed distinctions between landforms using geomorphological criteria take account of the

processes that gave rise to the landscape formation. Landform morphology results from

structural processes, such as tectonic uplift, weathering processes, such as decomposition,

erosional processes, such as detachment by wind, and from depositional processes, such as

sedimentation (Chorley et al, 1984). For the purposes of classification of wetland ecosystems

this type of separation is not required because the important element is the wetland ecosystem itself. A subdivision of geomorphic landforms associated with wetlands, on the basis of their

formation processes, would create a cumbersome classification that would add a level of detail that could only be understood by an experienced geomorphologist. To avoid this the fimctional classification utilises recognisable terms, such as river marginal and estuarine, to provide a distinction between specific landforms associated with wetlands. Although the grouping of geomorphic setting is not achieved using the controlling formation processes but rather focusing on the characteristic associated wetland, the terms used and the descriptions given, are inherently linked to the processes that shaped the landscape where the wetland is contained.

There are three scales at which geomorphology is used within the fimctional classification. Butzer (1976) described these three different scales as macrolandforms, mesolandforms and microlandforms. Butzer (1976) stated that a hill might be described as a macrolandform, a hillside as a mesolandform, and the individual rills or striations on a hillside as microlandforms. The five major geomorphic types of River Marginal, Estuarine, Basin, Coastal and Extensive Peatland are macrolandforms. Whilst the sub-types related to these, such as Sedimentary Erosional Estuary are mesolandforms. Hydrogeomorphic units which are used in the final stages of the classification, to determine potential functioning, are microlandforms. Using these three scales the functional classification provides a clear structure for ease of use and provides a system that can more accurately determine potential functioning.

The discussion has illustrated that the use of geomorphology as a criteria for classification of European wetlands is beneficial because it provides information on a key ecosystem structural element, that allows the determination of potential functioning, and utilised at different scales, provides a logical structure to the classification.