Representativeness

Representativeness (R) is the degree to which each ecosystem spatial unit is representative of a biological or physical class to which it belongs. It was assessed through a set of statewide biological and physical classifications of each ecosystem based on a range of different classification components (e.g. fish, riparian vegetation, hydrology, etc.).

Each classification covers a number of different classes, and these can range in extent from being widespread (like Hydrological region 3 used for Rivers which covers most of western Tasmania) to rare (like the Physical class used for waterbodies which separates out Perched Lake as being a unique member of its own class). A map of the distribution of each of these classes is shown below.

Lets consider the term representativeness using these examples further, Perched Lake is highly representative of its class and extremely rare. In contrast the 33 most representative river sections for Hydrological region 3 were selected using attributes such as length and condition and could easily be replaced by examples from elsewhere in western Tasmania. All of these highly representative spatial units belong within the upper band (band A) of Representative Conservation Value (RCV).

Map
Two different biophysical classes: Perched Lake is a unique member of a rare physical class, while the red river sections in central Tasmania are the most representative examples of the extensive class called Hydrological Region 3 (in blue)

Every spatial unit (e.g. river sections or wetlands) considered by the CFEV assessment belongs to one class from each of the classifications that were used for that ecosystem theme. For example, a river section will have 7 different biophysical classifications and it will vary in how good a representative it is of each of these; a wetland will belong to 6 different biological or physical classes. The RCV of the physical unit is driven by the class of which it is most representative.

For example, Perched Lake is the only member of its particular physical class (Wb19), but is it also a member of five other classes which form part of the waterbodies classification (see table below).

ClassificationClass codeClass description
Crayfish regionC2Astacopsis tricornis present
Frog assemblageFR9West - Assemblage characterised by high probability of occurrence of: Limnodynastes dumerili insularis, Litoria ewingi, Litoria burrowsae, Crinia signifera, Crinia tasmaniensis
Native fish assemblageF16Assemblage distributed within coastal streams and waterbodies that extend along most of the west coast including King Island through to the western edge of the Derwent River. Species Composition: Anguilla australis, Galaxias truttaceus, Geotria australis & Mordacia mordax, Prototroctes maraena, Neochanna cleaveri, Pseudaphritis urvillii, Galaxias brevipinnis, Galaxias maculatus, Retropinna tasmanica
Tree assemblageT43Western lowland riverine rainforest, tea tree forest and wet eucalypt forest . Similar communities to 21, 38 and 50. Found along the Gordon river and its tributaries: the Franklin, Maxwell, Denison and Olga rivers, extending also to the Hardwood River. Species Composition: Anodopetalum biglandulosum, Atherosperma moschatum, Cenarrhenes nitida, Eucalyptus nitida, Eucryphia lucida, Lagarostrobos franklinii, Leptospermum nitidum, Leptospermum scoparium eximium, Leptospermum scoparium var., Melaleuca squarrosa, Monotoca glauca, Nothofagus cunninghamii, Phebalium squameum, Phyllocladus aspleniifolius, Pittosporum bicolor, Tasmannia lanceolata
Tyler classTY9Lakes with natural meromictic state (only in Lower Gordon). Red-window optical environment ('fulvic dominated'). Marked stratification, with fresh epilimnion and saline to brackish hypolimnion.
Waterbody physical class Wb19Lowland, warm monomictic lake in SW Tasmania (Perched Lake only)

All of these classes are far less rare (in total extent) than the physical class Wb19, and so the Waterbody physical class is the most important biophysical class for Perched Lake, and thus drives in RCV ranking.

The different biological and physical classifications for each of the different ecosystems are detailed in the CFEV assessment framework summary.

Descriptions of the different biophysical classes are included in the reports produced by the WIST and CFEVCI, or can be found in the CFEV technical report.

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