Summary - City of Gosnells

Regional Setting 13(Keighery and Trudgen, 1992; Government of Western Australia, 2000a). These areas are specificallyprotected by the Bush Forever policy (Government of Western Australia, 2000a, p. xiv) that states:‘There will be a general presumption against clearing bushland containing threatened ecologicalcommunities or representation of vegetation complexes of which less than 10 per cent currentlyremains on the Swan Coastal Plain portion of the Perth Metropolitan Region (generally involving theeastern side of the Swan Coastal Plain).’Bush Forever Site 387 (The Greater Brixton Street Wetlands) is the most species-rich area of all the BushForever sites described in the Bush Forever report (Government of Western Australia, 2000a, 2000b) and, assuch, is one of the most important conservation reserves in the Swan Coastal Plain Bioregion of WesternAustralia. Currently more than 555 native plant taxa are known from the 127 ha of the Greater Brixton StreetWetlands (Keighery and Keighery, 2000). This represents over 26% of the total native flora of the PerthFloristic District, about 20% of the total native flora of the species-rich Swan Coastal Plain (SCP) Bioregionand about 12% of the total native flora of the South West Australian Botanical Province (the latter area beingthe only globally-significant biodiversity ‘hot spot’ in Australia) (Conservation International, 2008; WesternAustralian Herbarium, 2009). The Greater Brixton Street Wetlands contain nearly five times the speciesrichnessof native flora per unit area that is found in Kings Park, which has only 293 native taxa in 321 ha ofbushland according to Government of Western Australia (2000b). Factors that are likely to have contributedto the very high biodiversity values exhibited in remnant bush and wetlands in the vicinity of the GreaterBrixton Street Wetlands include:• The great habitat heterogeneity provided by the complex hydrogeology in the alluvial fans of the PinjarraPlain (V & C Semeniuk Research Group, 2001);• The inclusion, in BFS 387, of a substantial sample of the topographical series of landforms and soils(catena) that occur within the Wattle Grove-Kenwick alluvial fan (due to the orientation of this BushForever Site parallel to the topographical gradient down the alluvial fan - Figure 7);• The very species-rich pool of flora available in the southwest Western Australia Floristic Province thatwas available to colonise the ESCP via the natural corridors; and• The repeated fluctuations in climatic and edaphic conditions that were experienced in the region duringthe Quaternary era. Whilst there was good connectivity between the habitats of the ESCP and the DarlingRange and its hinterland, plants adapted to both semi-arid and humid conditions were able to colonise theESCP during climatic fluctuations. This connectivity of habitats between the Darling Range and theCanning River along the Yule Brook is still functioning currently to a certain extent.2.6.1 Regional Scale Vegetation Units of the Eastern Swan Coastal PlainThere have been numerous studies that have aimed to characterise, classify and/or map the vegetation unitsthat are present within the Swan Coastal Plain Bioregion to investigate the land-use capability of land thatwas covered with the native vegetation and to assess the conservation significance and reservation status ofthis vegetation. The terms Vegetation Systems, Vegetation Complexes and Vegetation Associations havebeen used by various authors to designate vegetation units mapped at various scales. All of these units areregional scale, high order units.2.6.1.1 Vegetation Systems (Beard, 1979a)Beard (1979a, 1979b, 1981) mapped the vegetation of the Swan Coastal Plain as broadscale VegetationSystems based on the structures of the dominant vegetation layers. In this mapping, the vegetation of most ofthe MKSEA and neighbouring area is indicated as Marri (Corymbia calophylla) Woodland (e 3 Mi), of thePinjarra Plain Vegetation System (as defined by Smith 1974). Beard’s Pinjarra Plain Vegetation Systemextended from about Gingin to Dunsborough and was located between the Bassendean Vegetation System tothe west and the Ridge Hill Shelf Vegetation System to the east. The Pinjarra Plain Vegetation Systeminhabited the most fertile soils of the coastal plain, which were preferentially developed for pasture andirrigation systems. Because Beard (1979a) considered that very little (if any) virgin Marri Woodland of theTauss, C. and Weston, A.S. (2010). The flora, vegetation and wetlands of the Maddington-Kenwick Strategic Employment Area.A survey of the rural lands in the vicinity of the Greater Brixton Street Wetlands. Report to the City of Gosnells, W.A. Version 18.04.10