Declared Rare and Poorly Known Flora in the Geraldton District

Mingenew areas has loamy soils, which may be acid to alkaline. The coastal limestone is covered by shallow siliceoussand that is red in the north of the District, becoming yellow in the south.6.3 VegetationThe western side of the Geraldton District falls within the South-West Botanical Province, including parts of the Irwinand Avon Botanical Districts, whilst the eastern part of the District comes within the Austin Botanical District of theEremaean Botanical Province.The Austin Botanical District lies on the Yilgarn Block. Its western boundary coincides with that of the Yilgarn Blockbut its southerly boundary is determined by the rainfall patterns. The vegetation is characterised by mulga, Acaciaaneura, which grows in several forms. As a tree with a single erect trunk, on favourable soils it forms low woodland,on plains with red loam soils overlying hard pan. It forms a shrub in less favourable situations where it extends ontohills or downslope and it is less common or absent on sandplain or on heavy alkaline or saline soils. Mulga woodlandhas an open tree layer 3 m or more tall, with a sparse layer of low shrubs 1-2 m tall and a ground layer of ephemeralherbs which varies in density according to the favourabilty of the season. Mallees such as Eucalyptus kingsmillii mayalso be present. Species of Cassia are common in the shrub layer, with Eremophila species. Perennial grasses occur onlow banks of sandy soil, where A. linophylla occurs with A. aneura.Granite and gneiss hills also have mulga in shrub form, associated with A. quadrimarginea and A. grasbyi. Thisassociation is also found on the edging laterite breakaways or scarps of sandplains, sometimes with Callitris andEucalyptus species. On the open areas of white clay at the base of these breakaways, Frankenia species and otherhalophytes occur.On slopes lower in the landscape from the plains with mulga woodland, the woodland opens out and patches of scrubwith A. sclerosperma, A. tetragonophylla and Hakea preissii become more common. Lower still, Maireana species arepresent, with Melaleuca uncinata and Eremophila species. These are replaced by samphires as salinity increases.Where calcrete has been deposited in drainage lines, a characteristic scrub of A. sclerosperma, Pittosporumphylliraeoides and Grevillea nematophylla occurs. Near rivers with active drainage, Eucalyptus camaldulensis andCasuarina obesa may become frequent enough to form woodland. On salt flats, Atriplex, Maireana and Frankeniaspecies form low colonies.Sandplains in the eastern part of the District, such as in the Sandstone area, have hummock grasses, Triodia andPlectrachne species, with scattered trees, particularly Eucalyptus gongylocarpa, on deeper sand. Mallee eucalypts, suchas E. kingsmillii, E. oldfieldii and E. leptopoda may occur.On the south-west side of the Austin Botanical District, the Yalgoo Sub-region is the transitional zone between theEremaean and Southwestern Provinces. The rainfall increases towards the south-west and although the vegetation isbasically Eremaean, this change towards the South-west Botanical Province is marked by the decrease in frequency ofmulga and its replacement by other species of Acacia. Outliers of mulga woodland occur to the north and east ofYalgoo. As mulga decreases in frequency, it is replaced by scrub of A. ramulosa and A. acuminata on hills, mixedAcacia scrub on plains, A. ramulosa and A. murrayana on sandplains and A. sclerosperma and A. eremaea with Atriplexand Maireana species on low lying flats. Further south, midslope vegetation is of thickets of Acacia ramulosa, A.acuminata and Melaleuca uncinata, scrub of A. ramulosa, Callitris and Eucalyptus in the valleys.In this sub-region, an extensive chain of salt flats and lakes runs from Lake Monger westward to Lake Nullewa. Theseare surrounded by samphire, teatree and Acacia-Eremophila scrub.Hills and ranges in the area may be of banded ironstone, with sparse shrubs of Acacia, Eremophila, Thryptomene andPtilotus obovatus. Greenstone hills are less harsh and better vegetated.To the east of the Yalgoo Sub-region lies the Barlee Sub-region, east of Lake Moore and the Great Northern Highway,running north to Mt Magnet and Youanmi. This an area of gently undulating country with extensive sandplains,straddling a watershed, draining north to Lake Austin, south-west to Lake Monger and Lake Moore and east to LakeBarlee and the Youanmi salt flats. The vegetation is basically of Acacia scrub on hills, sandplains, mulga lowwoodland on plains and halophytic communities in low-lying saline areas. Rainfall rises towards the south where theboundary with the Southwestern Interzone lies. Mixed with the mulga are native pines, sheoaks and eucalypts andoutliers of eucalypt woodland on the southern boundary. Mulga is dominant on hills in the north, giving way to Acaciaacuminata, A. ramulosa and A. quadrimarginea in the south. Sandplains support bowgada, heath and spinifex.19