DARLING RIVERINE PLAINS BIOREGION Background Report

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16/08/02 Darling Riverine Plains Bioregion Background Report (myall) community, for example, has greatly diminished as a community and is not well conserved (Mitchell 1991). The pre-1750 vegetation of the DRP bioregion has been substantially modified but not in a consistent way or degree throughout the bioregion. In the eastern portion, clearing of the forests and woodlands on the productive alluvial plains has left an extensively changed landscape, one dominated by agricultural uses and containing only small patches of remnant native vegetation communities. In the western semi-arid portion of the bioregion the initial effects of overgrazing were extreme, but with changes in management there has been some recovery of the vegetative cover. In general terms there has been a shift from woodland to a larger proportion of grassland but of different and predominantly introduced species. 3.2 VEGETATION MAPPING AND DESCRIPTION IN THE DRP Vegetation mapping covering the DRP is limited to very broad-scale datasets, with some detailed mapping of small areas. Only the Murray Darling Basin Commission basin-wide mapping of structural and floristic attributes of the vegetation (M305) covers the entire DRP (MDBC 1991) (Map 24). This M305 mapping indicates that only 6.2% of the DRP is now covered with woody vegetation. In the Macquarie catchment 6.4% of the area is covered with woody vegetation (M305). Eucalyptus populnea subsp. bimbil (bimble box) communities are dominant, but are in poor health, with the grassy/herbaceous E. populnea subsp. bimbil woodland of the relic floodplains being severely fragmented through cropping, while the more shrubby E. populnea subsp. bimbil woodlands have been largely affected by grazing, thinning, ring-barking and cropping (Lewer, S., DLWC, pers. com. Dec. 2001). Understorey species have almost completely disappeared and less than 13% of the region retains natural pastures (MDBC 1991; Macquarie 2100 report). The value of the M305 vegetation mapping is limited, as it omits native grasslands and shrublands with less than 20% woody cover and provides no specific indication of species composition or community health. The precision, scale, methodology and coverage of mapping with floristic interpretation varies throughout the region. Other broad-scale vegetation datasets are listed in Table 3.1. Table 3.1 Existing broad-scale vegetation mapping in the DRP Dataset Scale of mapping Notes / references 62 % of DRP covered The Vegetation of Australia 1:10 000 000 Beadle (1981) 100% AUSLIG Atlas of Australian 1:5 000 000 AUSLIG (1990) 100% Resources: Vegetation The Natural Vegetation of 1:1 000 000 Pickard and Norris (1994) 21% North-Western Wales New South Murray Darling Basin 1:100 000 Broad Landsat structural and floristic interpretation 98% Commission M305 Datalayer (nominal) of woody/non-woody vegetation in the Murray- Darling Basin (MDBC 1991). Conservation Atlas of Plant Point data used to Specht et al. (1995) not available in electronic form 100% Communities estimate locations – published only in hard copy. of vegetation Natural Vegetation of the communities 1:250 000 Sivertsen and Metcalfe (1995) 57% Southern Wheatbelt
16/08/02 Darling Riverine Plains Bioregion Background Report The eastern 57% of the bioregion has been mapped as part of the NPWS wheatbelt mapping project (Sivertsen & Metcalfe 1995). This includes systematic site survey data and includes updated mapping layers which incorporate information about clearing of native vegetation, covering the period from 1987 to 1998 (Sivertsen & Metcalfe 1999). This mapping identifies woody vegetation of greater than 5% cover and a remnant patch sizes of greater than 10 hectares. The lower reaches of the Macquarie and Bogan Rivers have been surveyed and mapped during a number of studies. Beadle (1948) mapped the area in the west and Biddiscombe (1953,1963), the east. These maps outline the vegetation communities of the area but do not indicate the densities of woody vegetation cover. Steenbeeke (1996) mapped the lower Macquarie floodplain, upstream of the Macquarie Marshes using aerial photography; Peasley (1999) mapped Moree Plains and East Walgett; and Sawtell (undated) mapped the West Walgett and Brewarrina Regional Vegetation Committee (RVC) areas. Two additional surveys did not included mapping. These were the survey of native vegetation in the lower Macquarie valley irrigation area by Hassall and Associates (1996); and the vegetation survey of stock routes in the central west by Nowland (1997). The survey report by Hassall and Associates (1996) outlines the health of native vegetation and discusses the distribution and decline in woody vegetation cover since European settlement. The spatial distribution of recent fine-scale vegetation mapping indicates a gap in floristic community information in the centre of the DRP (Map 25). Lee (1925) includes excerpts from the diary of the botanist on Oxley’s expedition from Condobolin to the Bogan River describing the vegetation of the area. Surveys of the natural pastures were undertaken of the north-west slopes of New South Wales by Williams (1979). Several authors have provided general descriptions of plant communities in the DRP. In their descriptions of the provinces defined for the DRP, Morgan and Terrey (1992) described briefly the dominant plant communities. These descriptions are very broad but cover the entire bioregion. Plant communities in the portion of the bioregion within the western division of New South Wales have also been described by Walker (1991) and Cunningham et al. (1992), and the plant communities of the northern floodplains are described in Smith et al. (1998). None of these descriptions has been based on quadrat sampling or detailed plant community analysis. The Sivertsen and Metcalfe (1995) mapping also contributed to the description of plant communities within the eastern portion of the DRP which overlaps with the majority of the Macquarie catchment within the DRP, and the entire area of the Macintyre, Gwydir, Namoi and Castlereagh catchments within the DRP. Howling (1997) described seven woodland communities for the Central West catchment (including Macquarie, Bogan and Castlereagh Catchments), highlighting the importance of riparian, wetland, shrubland and native grassland communities. 63
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DARLING RIVERINE PLAINS BIOREGION B
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For more information data contact t
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3.2 Vegetation Mapping and Descript
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10 APPENDICES 166 A CLIMATIC DATA B
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List of Maps Chapter 1 Map 1 Locati
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Initial Phase Assessment Phase 16/0
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Appendix A: Mean Monthly Rainfall a
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Major Rangetype Rangetype Physiogra
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Appendix C : Native Flora Other Tha
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Family Scientific Name cretica Comm
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APPENDIX E: Fauna Other than Those
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Common 1983 1984 1985 1986 1987 198
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Taxa No Records Dataset Class Arach
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Taxa No Records Dataset Tabanidae s
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Taxa No Records Dataset Berosus sp
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