Natural vegetation of the New South Wales Wheat-belt (Cobar–Nyngan–Gilgandra, Nymagee–Narromine–Dubbo 1:250 000 vegetation sheets)

The vegetation of the Central Division of New South Wales (lat. 31°–33° S, long. 146° 30’–149° E) was classified and mapped (Cobar–Nyngan–Gilgandra, Nymagee–Narromine–Dubbo 1:250 000 mapsheets) as part of the NSW National Parks & Wildlife Service wheat-belt mapping series. The vegetation classification was derived using traditional air photo interpretation and quantitative analysis of data from 428 field sites. Analyses included hierarchical classification in PATN to define floristic groups, then Fidel and ANOSIM to elucidate the characteristic species of the groups and explore the consistency of these relationships at various levels of similarity. Maps and descriptions show the floristic composition and structure, the geographic distribution of assemblages, the current extent, and shape and degree of connectivity of vegetation and changes in native woody vegetation cover over time. 22 vegetation units were defined, 19 were woodlands and forests dominated by eucalypts including Eucalyptus populnea subsp. bimbil — P4 Poplar Box Woodlands and P16 Simple Poplar Box Woodlands; Eucalyptus largiflorens — R3 Black Box Woodlands; Eucalyptus microcarpa — P12 Woodlands on Jurassic Sandstone and P13 Grey Box Woodlands; Eucalyptus camaldulensis — R1 River Red Gum Forests and Woodlands; Eucalyptus intertexta — P14 Red Box, Poplar Box and Pine Woodlands, U1 Red Box, Poplar Box, Pine and Green Mallee Woodlands and U2 Red Box, Poplar Box and Pine Woodlands on Granite Hillslopes; Eucalyptus dwyeri — U3 Dwyer’s Red Gum Low Open Woodland on Granite Crests, H1 Dwyer’s Red Gum, Ironbark and Green Mallee Woodlands and H9 Dwyer’s Red Gum Open Woodlands on Granite Hills; Eucalyptus viridis — H2 Green Mallee Woodlands; Eucalyptus morrisii — H6 Grey Mallee Open Woodlands; Mallee — H7 Mallee Woodlands on Rolling Hills and P1 Mallee Woodlands on Plains; Eucalyptus dealbata — H8 Tumble-down Red Gum Woodlands on Basalt Hills; and Eucalyptus chloroclada — P15 Dirty Red Gum, Pine and Poplar Box Woodlands. These eucalypt woodlands exhibit diversity in structure and associated species composition. Two tall open shrublands of Acacia pendula — R5 Myall Woodlands and Flindersia maculosa — P11 Leopardwood Open Shrublands and a woodland dominated by Callitris glaucophylla — P6 White Cypress Pine Woodlands are included in the mapping. The current extent of native woody vegetation is 1.2 million ha (29%) of the total 4.1 million ha study area. Over a period of 15 years approximately 130 000 ha or 10% of the extant vegetation was cleared. Only four of the 22 vegetation units are represented in conservation reserves. These reserves are not considered to adequately represent the diversity of the vegetation units they contain nor do they comprehensively represent the diversity of the vegetation. Threatening processes including; continued clearing, changing water regimes, habitat fragmentation, over-grazing by domestic, feral and native animals, nutrient enrichment, compaction of soil, firewood collection and weed invasion operate in this predominantly agricultural landscape, all of which have implications for the long-term persistence of the vegetation of the area.