Herbaceous species, or forbs, are also important, particularly in the southern parts. The rangeland based grazing industries are as diverse as their climatic range, and their resource diversity. Average rainfall varies from about 150 mm in the far south east to over 1500mm in the north, with associated variation in seasonality and reliability. Rainfall in the north is highly seasonal with a distinct summer wet season, and a winter dry season. In the south rainfall is more erratic and can occur at any time of the year Annual grasses are generally fast growing and short lived, particularly in the drier regions.
Most annuals disappear during the dry season, leaving the soil surface exposed.
They are generally smaller and shorter grasses of lower productivity than perennials and include Flinders Grass and annual sorghums. Perennial grasses are drought and fire resistant, generally resilient under grazing and capable of quick growth response after rain. Perennial grasses include desirable pasture species such as the Mitchell grasses, Golden Beard or Ribbon Grass and Perennial Sorghum. Perennial grasses, if not overgrazed, provide forage and soil protection during the entire dry season.