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DARLING RIVERINE PLAINS BIOREGION Background Report

DARLING RIVERINE PLAINS BIOREGION Background Report

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16/08/02 Darling Riverine Plains Bioregion <strong>Background</strong> <strong>Report</strong><br />

Grevillea juncifolia, Grevillea albiflora (white spider-flower), Acacia murrayana (sandplain<br />

wattle) and Acacia johnsonii (gereera wattle).<br />

Austrostipa aristiglumis (plains grass) grasslands<br />

Grey and brown clays of floodplains of major rivers support this community. Associated<br />

species include other grasses, perennial forbs and, following winter rains, annual grasses and<br />

forbs.<br />

Austrostipa spp. (variable speargrasses) and Enneapogon spp. (bottle washers) grassland<br />

This grassland community also often forms the groundcover of the Casuarina cristata -<br />

Alectryon oleifolius and Acacia loderi shrubland communities. It is found on solonized brown<br />

soils, calcareous red earths and desert loams and occurs with other grasses, chenopods,<br />

perennial forbs, and after winter rains, annual forbs. The dominance of Austrostipa variabilis<br />

is favoured by winter rains and Enneapogon spp. by summer rains.<br />

Floodplain communities<br />

A sparse to open chenopod shrubland and open grassland is found on the floodplains, playas<br />

and basins within the northern floodplains region. The height of this community ranges from<br />

0.5 to three metres and cover from five to 50%. Most common shrubs are Muehlenbeckia<br />

florulenta, Chenopodium auricomum (golden goosefoot), and occasionally regeneration of<br />

Eucalyptus camaldulensis. Ground cover species include Agrostis avenacea (blown grass),<br />

Eragrostis setifolia, Eleocharis pallens (pale spike-rush), Pycnosorus chrysanthus (golden<br />

billy-buttons), Atriplex pseudocampanulata (mealy saltbush) and Pimelea simplex (desert<br />

riceflower).<br />

Muehlenbeckia florulenta and Chenopodium nitrariaceum can form distinct communities<br />

although their boundaries can be indistinct depending on the degree, frequency and reliability<br />

of flooding.<br />

The Muehlenbeckia florulenta community occurs on alluvial areas with cracking grey soils<br />

and periodic flooding. It can be a treeless community, or have scattered Eucalyptus<br />

largiflorens, Eucalyptus camaldulensis, Eucalyptus coolabah or Acacia stenophylla.<br />

Associated shrub species include Eragrostis australasica, Leptochloa digitata (umbrella<br />

canegrass), Chenopodium nitrariaceum and Typha spp. (cumbungi). After floodwaters<br />

recede, a pasture of Marsilea drummondii, Eleocharis spp. (spike-rushes) and Eragrostis<br />

setifolia (neverfail) often grows between shrubs.<br />

Muehlenbeckia florulenta grows on the beds of the large overflow lakes and basins of the<br />

Menindee province, fringed by Eucalyptus largiflorens, Maireana pyramidata and Zygochloa<br />

paradoxa (sandhill canegrass) and sparse Casuarina cristata and acacias on the lunettes.<br />

The Chenopodium nitrariaceum community is found on the grey clay soils of the beds of<br />

periodically flooded lakes and flooded alluvial sites along major rivers. Trees are usually<br />

absent and complementary shrub species include Eragrostis australasica, Leptochloa digitata<br />

and Muehlenbeckia florulenta. Pastures similar to those found in the Muehlenbeckia<br />

florulenta communities occur after flooding.<br />

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