Summary - City of Gosnells

Regional Setting 156. Ephemeral Wetlands, a complex mosaic of shrublands, heaths, sedgelands and herblandsThe Corymbia calophylla and the Casuarina obesa woodlands and open forests and the wetland vegetationmosaic were considered to be the most common units prior to the large-scale clearing of the Pinjarra Plain.2.6.1.4 Floristic Community Types (FCTs)Early work to classify the vegetation of the Swan Coastal Plain using numerical classification of floristicdata was carried out by Havel (1968) and, later, by Heddle et al. (1980). More comprehensive survey andanalysis of the vegetation of the SCP was carried out by Gibson et al. (1994) to define finer-scale vegetationunits than those of the regional-scale Vegetation Systems of Beard (1979) and the Vegetation Complexes ofHeddle et al. (1980). The vegetation units derived by Gibson et al. (1994; Government of Western Australia2000) are known as the Floristic Community Types of the Swan Coastal Plain (SCP FCTs).As there were only 43 FCTs identified for the entire SCP by Gibson et al. (1994), it is a fair assumption toconsider that these FCTs represent relatively high order units (as discussed by Trudgen, 1999, and by Griffin,Appendix C). In the current survey, the FCTs are therefore considered as sub-regional scale vegetation unitsto differentiate them from the local scale vegetation units that were mapped in the current study (and in otherstudies of the Greater Brixton Street Wetlands, including Mattiske and Associates, 1992) at a scale ofapproximately 1:5,000 or finer.The derivation of Floristic Community Types, after Gibson et al. (1994), is an example of a purely-floristicmethod of vegetation classification. In floristic classification, vegetation classes are defined by the groupingof standard-sized, sample plots of native vegetation (on the basis of the similarity matrices of the floristiccomposition of these plots) with the aid of software such as PATN®. In the case of the FCTs of the SwanCoastal Plain defined by Gibson et al. (1994) and in subsequent update studies, the standard size of thevegetation sample plot from which floristic data are recorded for the purposes of FCT definition is a 10 m by10 m quadrat. It is important to note that the definition of FCTs on the SCP by this method does not includevegetation structure data or individual taxa abundance data from the vegetation sample plots in the analysis.Only presence/absence data of all vascular flora taxa (regardless of height and cover class) are included inthe analysis.In Gibson et al. (1994), 509 standard quadrats were surveyed on public lands throughout the SCP to recordfloristic data. A numerical classification of these vegetation samples resulted in the identification of foursupergroups of sites. These supergroups were correlated with three of the major geomorphic units of the SCP(Foothills/Pinjarra Plain, Bassendean Dunes and Spearwood/Quindalup Dunes) and seasonal wetlands. TheGibson et al. 1994 supergroups can thus be considered as showing regional scale patterning of the vegetationat approximately the same scale as the Vegetation Complexes of Heddle et al. (1980).Within the four supergroups of Gibson et al. (1994) there were a total of 43 clusters of sites. Each of these 43clusters of sites was designated by Gibson et al. (1994) as a Floristic Community Type (FCT). The SeasonalWetlands supergroup contained the largest number of FCTs. However, the mean number of quadrats thatwere sampled per FCT in this supergroup was the lowest of all the supergroups, i.e. the seasonal wetlandswere relatively poorly sampled in this study.Numerous attempts have been made (e.g. Trudgen, 1999) to numerically compare the floristics of thevegetation units derived by fine scale mapping on the SCP with the data obtained in Gibson et al. 1994. Thevegetation units recorded in environmental assessment projects, such as the current survey, that, on analysis,show affinity with the Gibson et al. (1994) FCTs that are recognised as Threatened Ecological Communities(DEC, 2007 and DEWHA, 2008) have very high conservation value. However, because most of theThreatened Ecological Communities (TECs) of the SCP are defined exclusively by their statistical similaritywith the FCTs found by Gibson et al. (1994), vegetation that does not show floristic affinity to these FCTs, isoften, in practice, automatically deemed to be of low conservation significance. The results of such analyseshave often failed to recognise vegetation that is known to be genuinely rare and threatened on the SCP by themost experienced botanists and environmental scientists working in Western Australia (Trudgen, 1999 beingthe best documented example of this).The floristic classification of the vegetation of the SCP of Gibson et al. (1994) was later updated by theaddition of floristic data from a further 613 quadrats surveyed on both private and public lands of the SCPTauss, 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