DARLING RIVERINE PLAINS BIOREGION Background Report

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16/08/02 Darling Riverine Plains Bioregion Background Report Eragrostis australasica (cane grass) and Leptochloa digitata (umbrella canegrass) community Eragrostis australasica (cane grass) swamps occur in pans in sand dune country and on lakebeds with compact clay soils that are subject to periodic inundation. Few species are associated with this community except for scattered Eremophila bignoniiflora. Swamp or marsh communities These communities occur on sites with permanent, or effectively permanent, still or slowmoving shallow water. Vegetation is commonly composed of Phragmites australis (common reed), Typha spp. and other aquatic species, with or without emergent Eucalyptus largiflorens, Eucalyptus camaldulensis and Eucalyptus coolabah. 3.3.4 Plant communities of major DRP wetlands Mapping and survey of plant communities in some of the major wetlands within the DRP indicates that there are distinct differences between them. These distinctive features suggest that each of the wetlands is significant in its own right, as well as being critical in the interconnecting, but diminishing, network of wetland habitats which support waterbird movements. The wetlands of the DRP are dynamic and strongly influenced by the irregular and uneven distribution of rain events and rainfall intensity in their catchments. They are adapted to this variability, with the relative proportions of particular wetland vegetation associations varying in relation to the prevailing climatic conditions. The frequency and duration of flood events mostly determine the distribution, composition and structure of wetland plant communities. The regulation of river flows has changed the dynamic nature of this system, stabilising and enlarging the area of the drier plant communities while reducing the core wetlands and causing long term community changes through the loss of conditions suitable for the recruitment of some tree species (Kingsford & Thomas 1995). Table 3.2 below gives a brief summary of the dominant plant communities within the major wetlands of the DRP. Plant community Forests and woodlands Shrublands Grasslands and reedlands Table 3.2 Dominant plant communities of major wetlands of the DRP Dominant species Major wetlands of Area within each DRP major (ha) wetland Eucalyptus populnea subsp. bimbil woodlands Macquarie Marshes 10 023 Eucalyptus largiflorens woodlands Macquarie Marshes 15 800 Eucalyptus coolabah woodlands Macquarie Marshes 8 040 Gwydir Wetlands 50 000 Gingham Wetlands 150 000* Eucalyptus coolabah – Eucalyptus camaldulensis woodlands Gingham Wetlands 2 000 Eucalyptus camaldulensis woodlands Macquarie Marshes 39 500 Narran Lakes nd Eucalyptus camaldulensis – Eucalyptus coolabah – Narran Lakes nd Eucalyptus largiflorens – Acacia stenophylla woodlands Casuarina cristata woodlands Gingham Wetlands Acacia pendula shrublands Macquarie Marshes 8 600 Acacia stenophylla shrublands Macquarie Marshes 3 270 Acacia stenophylla and Muehlenbeckia florulenta shrublands Gingham Wetlands 42 000* Muehlenbeckia florulenta shrublands Macquarie Marshes 2 840 Narran Lakes nd Phragmites australis and Typha spp. Reed beds Macquarie Marshes nd Marsh club-rush Bulboschoenus fluviatilis, Eleocharis plana, Paspalum distichum and Juncus aridicola communities Gwydir Wetlands 10 000 Paspalum distichum and Eleocharis spp. communities Gingham Wetlands 13 500* Grasslands Macquarie Marshes 108 000 76
16/08/02 Darling Riverine Plains Bioregion Background Report * estimated area prior to construction of Copeton Dam on the Gwydir River nd = no data Macquarie Marshes The plant communities of the Macquarie Marshes include 108 000 ha of grassland, 10 023 ha of Eucalyptus populnea subsp. bimbil woodland, 8 600 ha of Acacia pendula, 2 840 ha of Muehlenbeckia florulenta, 15 800 ha of Eucalyptus largiflorens, 8 040ha of Eucalyptus coolabah, 3 270ha of Acacia stenophylla and 39 500 ha of Eucalyptus camaldulensis forest (Bray 1994b). Slow flowing channels have Vallisneria gigantea (ribbon reed), Potamogeton crispus (curly pondweed), Azolla filiculoides (red azolla), duckweeds, rushes and Paspalum distichum (water couch). Typha sp. occurs in the more permanently wet channels within reed beds. The Macquarie Marshes contain the most northern occurrence of extensive reed beds of Phragmites australis (Wolfgang 1998). In the Macquarie Marshes, tree health has been affected by variation in flood regimes, raised water tables and salinisation, herbicide spray drift, tree senescence, fire damage, pathogens and insects. The area of wetland vegetation in the Marshes has declined as a result of river regulation which has reduced the frequency of large and medium flows. This has, in turn, led to a change to a vegetation association more suited to a drier environment. Reed beds were formerly dominant in south marsh, but this area has recently been colonised by chenopods (Atriplex and Sclerolaena spp.). Weeds are also prevalent. Large areas have been cleared for farming, with the area of Eucalyptus camaldulensis in the southern marshes having been reduced from an estimated 1 406 ha in 1931 to 636 ha in 1981 (Wolfgang 1998). Lower Gwydir Wetlands The Lower Gwydir supports about 24 000 ha of semi-permanent wetland and floodplain plant communities, including 7 500 ha of Paspalum distichum and Juncus aridicola (tussock rush) and a 700 ha stand of Bolboschoenus fluviatilis (marsh club-rush), the largest area of Bolboschoenus fluviatilis known in New South Wales. One third of this area (2 500 ha) in the west is highly degraded. Intermittent wetland areas of the lower Gywdir wetlands include 4 000ha of lignum (Muehlenbeckia florulenta) and river coobah (Acacia stenophylla). Approximately 4 880ha of coolibah (Eucalyptus coolabah) occurs on the floodplain of the lower Gywdir Wetland. Other significant plant species in this wetland include Eleocharis plana (ribbed spike-rush), Eleocharis sphacelata (tall spike-rush), Juncus aridicola (tussock rush) and Typha spp. (cumbungi) (Johnson 2001; Ramsar 1999). The main wetland area contains stands of dead Eucalyptus coolabah killed by prolonged inundation from the 1955 and 1970 floods and the release of water from Copeton Dam for spillway modifications in the 1970s. The dominant species in the seven distinct landform types within the wetland are shown on Figure 3.12 and listed in Table 3.3 (Keyte 1994). 77
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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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PROJECT SUMMARY This report forms p
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abbits are listed as key threatenin
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16/08/02 Darling Riverine Plains Bi
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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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APPENDIX E: Fauna Other than Those
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Common 1983 1984 1985 1986 1987 198
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Common Name 1983 1984 1985 1986 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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DARLING RIVERINE PLAINS BIOREGION Background Report

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