The Avon Wheatbelt is a bioregion in Western Australia. 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, an ancient block of crystalline rock, which was uplifted in the Tertiary and dissected by rivers. The craton is overlain by laterite deposits, which in places have decomposed into yellow sandplains, particularly on low hills. Steep-sided erosional gullies, known as breakaways, are common. 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. Subregions It has within it two subregions named after localities within the region: Merredin - AVW01 Katanning - AVW02 Climate The bioregion has a semi-arid Mediterranean climate, 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 to the west. Flora and fauna Scrub-heath, characterized by shrubs in the Proteaceae 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) and rock sheoak (Allocasuarina huegeliana), and woodlands of jam (Acacia acuminata) and York gum (Eucalyptus loxophleba), are found on granite-derived soils and the alluvial soils of plains and stream valleys. There are smaller areas of wandoo woodland. The Wongan Hills 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), and silver mallet (Eucalyptus falcata), 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, Banksia bella, Eremophila ternifolia, Philotheca wonganensis, and Chenopodium aciculare. Granite outcrops, like Boyagin Rock, Kokerbin Rock, and Yilliminning Rock, are important as seasonal habitats and refuges for native fauna. Some are home to some