The Avon Wheatbelt is a

bioregion A bioregion is an ecologically and geographically defined area that is smaller than a biogeographic realm, but larger than an ecoregion or an ecosystem, in the World Wide Fund for Nature classification scheme. There is also an attempt to use the ...

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

. It has an area of . It is considered part of the larger Southwest Australia savanna ecoregion.

Geography

The Avon Wheatbelt bioregion is mostly a gently undulating landscape with low relief. It lies on the

Yilgarn Craton The Yilgarn Craton is a large craton that constitutes the bulk of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts. Zircon grains in the Jack Hills, Narryer Terrane have b ...

, an ancient block of crystalline rock, which was uplifted in the

Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

and dissected by rivers. The craton is overlain by

laterite Laterite is both a soil and a rock type rich in iron and aluminium and is commonly considered to have formed in hot and wet tropical areas. Nearly all laterites are of rusty-red coloration, because of high iron oxide content. They develop by ...

deposits, which in places have decomposed into yellow sandplains, particularly on low hills. Steep-sided erosional gullies, known as breakaways, are common. Beecham, Brett (2001). "Avon Wheatbelt 2 (AW2 - Re-juvenated Drainage subregion)" in ''A Biodiversity Audit of Western Australia’s 53 Biogeographical Subregions in 2002''. Department of Conservation and Land Management, Government of Western Australia, November 2001. Accessed 15 May 2022

/ref> In the south and west (the Katanning subregion), streams are mostly perennial, and feed rivers which drain westwards to empty into the Indian Ocean. In the centre, east, and north (Merredin subregion) there is no connected drainage. Here streams, which are remnants of ancient drainage systems, flow only during wet years, and drain to chains of salt lakes. Beecham, Brett (2001). "Avon Wheatbelt 1 (AW1 - Ancient Drainage subregion)" in ''A Biodiversity Audit of Western Australia’s 53 Biogeographical Subregions in 2002''. Department of Conservation and Land Management, Government of Western Australia, November 2001. Accessed 15 May 2022

/ref>

Subregions

It has within it two subregions named after localities within the region: * Merredin, Western Australia, Merredin - AVW01 * Katanning - AVW02

Climate

The bioregion has a semi-arid

Mediterranean climate A Mediterranean climate (also called a dry summer temperate climate ''Cs'') is a temperate climate sub-type, generally characterized by warm, dry summers and mild, fairly wet winters; these weather conditions are typically experienced in the ...

, with hot, dry summers and mild winters, with most rainfall occurring in the winter months. The Avon Wheatbelt is generally dryer than the

Darling Scarp The Darling Scarp, also referred to as the Darling Range or Darling Ranges, is a low escarpment running north–south to the east of the Swan Coastal Plain and Perth, Western Australia. The escarpment extends generally north of Bindoon, to th ...

to the west.

Flora and fauna

Scrub-heath, characterized by shrubs in the

Proteaceae The Proteaceae form a family of flowering plants predominantly distributed in the Southern Hemisphere. The family comprises 83 genera with about 1,660 known species. Together with the Platanaceae and Nelumbonaceae, they make up the order Pro ...

family, are common on sandplains and lateritic uplands. These scrub-heaths are species-rich, and include many endemic plants. Mixed eucalypt woodlands with salmon gum (''

Eucalyptus salmonophloia ''Eucalyptus salmonophloia'', commonly known as salmon gum, wurak or weerluk or woonert or marrlinja. is a species of small to medium-sized tree that is endemic to Western Australia. It has smooth bark, narrow lance-shaped to curved adult leave ...

'') and rock sheoak ('' Allocasuarina huegeliana''), and woodlands of jam (''

Acacia acuminata ''Acacia acuminata'', known as mangart and jam, is a tree in the family Fabaceae. Endemic to Western Australia, it occurs throughout the south west of the State. It is common in the Wheatbelt, and also extends into the semi-arid interior. ...

'') and York gum (''

Eucalyptus loxophleba ''Eucalyptus loxophleba'', commonly known as York gum, daarwet, goatta, twotta or yandee, is a species of tree or mallee that is endemic to Western Australia. It has rough bark on the trunk, smooth olive to brownish bark above, lance-shaped adul ...

''), are found on granite-derived soils and the alluvial soils of plains and stream valleys. There are smaller areas of

wandoo Wandoo is the common name for a number of Western Australian ''Eucalyptus'' species, all of which have smooth white bark. The original "wandoo" is ''Eucalyptus wandoo''. Additional species have been given this name because of a perceived likeness w ...

woodland. The

Wongan Hills Wongan Hills is a range of low flat-topped hills in the Avon Wheatbelt bioregion of Western Australia. It is located at , in the Shire of Wongan–Ballidu. History The range was first recorded in 1836 by Surveyor General of Western Australia Jo ...

are a range of flat-topped hills, dissected by steep gullies, in the northern portion of the bioregion. They are the largest area of intact vegetation in the northern Wheatbelt. The hills are home to remnant woodlands of salmon gum, York gum, gimlet (''

Eucalyptus salubris ''Eucalyptus salubris'', commonly known as gimlet, fluted gum tree, gimlet gum and silver-topped gimlet, is a species of mallet that is endemic to low-rainfall areas of the wheatbelt and goldfields regions of Western Australia. Description '' ...

''), and silver mallet (''

Eucalyptus falcata ''Eucalyptus falcata'', commonly known as silver mallet or toolyumuck, is a species of Mallee (habit), mallee or marlock that is Endemism, endemic to Western Australia. It has smooth bark, lance-shaped to curved adult leaves, flower buds in group ...

''), and low forest of jam (''Acacia acuminata''), plant communities were once widespread but now rare in the Wheatbelt. The hills are home to 90 species of birds. Plants endemic to the Wongan Hills include '' Acacia botrydion, Acacia pharangites,

Acacia pygmaea ''Acacia pygmaea'', commonly known as the dwarf rock wattle, is a shrub of the genus '' Acacia'' and the subgenus ''Phyllodineae'' that is endemic to south western Australia. Description The erect single-stemmed shrub typically grows to a heigh ...

Banksia bella ''Banksia bella'', commonly known as the Wongan dryandra, is a species of dense shrub that is endemic to a restricted area of Western Australia. It has narrow, deeply serrated leaves covered with white hairs on the lower surface, heads of yellow ...

Eremophila ternifolia ''Eremophila ternifolia'', commonly known as Wongan eremophila is a flowering plant in the figwort family, Scrophulariaceae and is endemic to Western Australia. It is a low, many-branched, shrub with short, pointed leaves and small lilac-colou ...

Philotheca wonganensis ''Philotheca wonganensis'', commonly known as Wongan philotheca, is a species of flowering plant in the family Rutaceae and is endemic to the south-west of Western Australia. It is a shrub with thin, cylindrical leaves and white flowers with ...

'', and ''

Chenopodium aciculare ''Chenopodium'' is a genus of numerous species of perennial or annual herbaceous flowering plants known as the goosefoots, which occur almost anywhere in the world. It is placed in the family Amaranthaceae in the APG II system; older classific ...

''. Granite outcrops, like Boyagin Rock,

Kokerbin Rock Kokerbin Rock, also known as Kokerbin Hill, is a granite rock formation located within Kokerbin Nature Reserve in the Wheatbelt region of Western Australia. The area has special significance for the Nyoongar. There are claims that Kokerbin Rock ...

, and Yilliminning Rock, are important as seasonal habitats and refuges for native fauna. Some are home to some endemic species, including the tree '' Eucalyptus caesia'' endemic to Boyagin Rock and the lichens ''Paraparmelia sammyi'' and ''Paraparmelia sargentii'' endemic to Yilliminning Rock. Granite pools are home to 350 species of aquatic invertebrates, including 50 thought to be endemic to the Wheatbelt. Native mammals include the

red-tailed phascogale The red-tailed phascogale (''Phascogale calura''), also known as the red-tailed wambenger, red-tailed mousesack or kenngoor, is a small carnivorous marsupial found in inland areas of south-western Western Australia, and has been reintroduced in ...

(''Phascogale calura''), black-flanked rock-wallaby (''Petrogale lateralis lateralis''),

western brush wallaby The western brush wallaby (''Notamacropus irma''), also known as the black-gloved wallaby, is a species of wallaby found in the southwestern coastal region of Western Australia. The wallaby's main threat is predation by the introduced red fox (' ...

(''Macropus irma''), and

common brushtail possum The common brushtail possum (''Trichosurus vulpecula'', from the Greek for "furry tailed" and the Latin for "little fox", previously in the genus ''Phalangista'') is a nocturnal, semiarboreal marsupial of the family Phalangeridae, native to Austr ...

(''Trichosurus vulpecula''). Several other once-native mammals are now locally extinct. Native birds include

malleefowl The malleefowl (''Leipoa ocellata'') is a stocky ground-dwelling Australian bird about the size of a domestic chicken (to which it is distantly related). It is notable for the large nesting mounds constructed by the males and lack of parental ca ...

(''Leipoa ocellata''),

Carnaby's black cockatoo Carnaby's black cockatoo (''Zanda latirostris''), also known as the short-billed black cockatoo, is a large black cockatoo endemic to southwest Australia. It was described in 1948 by naturalist Ivan Carnaby. Measuring in length, it has a s ...

(''Calyptorhynchus latirostris''),

Baudin's black cockatoo Baudin's black cockatoo (''Zanda baudinii''), also known as Baudin's cockatoo or the long-billed black cockatoo, is a species of genus '' Zanda'' found in southwest Australia. The epithet commemorates the French explorer Nicolas Baudin. It has ...

(''Calyptorhynchus baudinii''), and

Australian bustard The Australian bustard (''Ardeotis australis'') is a large ground dwelling bird which is common in grassland, woodland and open agricultural country across northern Australia and southern New Guinea. It stands at about high, and its wingspan is ...

(''Ardeotis australis''). Toolibin Lake is an important breeding area for waterbirds in the inland drainage systems of south-western Australia, particularly

freckled duck The freckled duck (''Stictonetta naevosa)'' is a waterfowl species endemic to Australia. The freckled duck has also been referred to as the monkey duck or oatmeal duck. These birds are usually present in mainland Australia, but disperse to coas ...

(''Stictonetta naevosa'').

Land use

Much of the land is used for dryland farming, particularly wheat. Extensive areas have been converted to pasture for livestock grazing.

Protected areas

Less than 5% of the Avon Wheatbelt bioregion is in protected areas.