Open Access

Mark Tozer

• Twenty-two vascular plant communities occurring on, and adjacent to the Cumberland Plain and Hornsby Plateau, are defined using a multi-variate analysis of quantitative field survey data. Communities are described using structural features, habitat characteristics and diagnostic species. Diagnostic species are identified using a statistical fidelity measure. The pre–European spatial distribution of communities is estimated using a decision tree approach to derive relationships between community distribution and geological, climatic and topographical variables. Contemporary vegetation cover is estimated from 1:16 000 scale aerial photography (1997/98) and sorted into six categories based on cover of Eucalyptus species. These categories are only approximately related to vegetation condition: high Eucalyptus cover classes are most likely to contain high levels of floristic diversity, but areas with scattered cover or no cover at all may have either high or low diversity. Map accuracy is assessed using independent field samples and is primarily limited by the accuracy of 1:100 000 geological maps. Patterns in overstorey composition were mapped at 1:16 000 scale but were less useful in delineating community boundaries than was hoped because few species are confined to a single community. The extent to which observer bias may influence estimates of the present extent of remnant vegetation is investigated by comparing the interpretations of two observers for a subset of the study area. The community classification is interpreted in light of previous publications and the Endangered Ecological Communities listed under the NSW Threatened Species Conservation (TSC) Act (1995). Four communities listed under the TSC Act (1995) are represented by more than one unit in the new classification: Cumberland Plains Woodland (represented by Shale Plains Woodland, Shale Hills Woodland); Sydney Coastal River Flat Forest (Riparian Woodland, Riparian Forest, Alluvial Woodland); Shale/Sandstone Transition Forest (Shale/Sandstone Transition Forest low sandstone influence, high sandstone influence); and Sydney Turpentine-Ironbark Forest (Turpentine-Ironbark Forest, Turpentine-Ironbark Margin Forest). A further seven listed communities are described in this paper (Cooks River/Castlereagh Ironbark Forest, Shale/ Gravel Transition Forest, Castlereagh Swamp Woodland, Agnes Banks Woodland, Western Sydney Dry Rainforest, Moist Shale Woodland, and Blue Gum High Forest). As a result of clearing, native vegetation cover on the Cumberland Plain has been reduced to only 13.1% (+ 1.7) of the pre- European extent. Despite high levels of fragmentation, the presence of exotic species and a history of extensive grazing, high numbers of native species were recorded in remnants of all sizes. A large proportion of species was recorded once only (22%), while nearly half of all species were recorded 5 times or less. This suggests that there is a high likelihood that further clearing will lead to a loss of floristic diversity. Two exotic species (Olea europea subsp. africana and Myrsiphyllum asparagoides) are identified as a major threat to the conservation of native flora due to their widespread distribution and ability to out-compete native species. Control of these species should be a high priority in conservation management.