Ribbon grass alluvial plain pastures in the Kimberley, Western Australia

Ribbon grass alluvial plain pastures

These pastures are part of the Kimberley 'black' soils group of pastures, and the perennial ribbon grass is the identifier grass. Use the interactive key to pasture condition to help identify pasture type.

Pastoral value

Ribbon grass alluvial plain pastures have a high pastoral value when in good condition. Ribbon grass plants can be killed by repeated prolonged heavy grazing, especially during dry years.

Occurrence

Ribbon grass alluvial plain pastures occur on level alluvial plains throughout the Kimberley. They are found on deep grey or brown cracking clays and occur as tussock grasslands, sometimes with a variable cover of trees, such as eucalypts and bauhinias. These pastures occupy a similar niche to Mitchell grass alluvial plain pastures. The main difference is that here Mitchell grasses are totally absent; additionally, some tree cover is a little more likely and gilgai microrelief is not always evident.

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Pasture condition

Good: When in good pasture condition, these pastures are dominated by ribbon grass. Bundle-bundle is also often present. Isolated plants of intermediate species, such as native millet (more common in higher rainfall areas), silky browntop or annual sorghum, may be present. There is little bare ground visible, unless the pasture is heavily grazed, and the plants appear vigorous (Figure 1).

Figure 1 Ribbon grass alluvial plain pasture in good condition in the Kimberley (photograph taken May 2008). A High density and even spacing of ribbon grass plants, which appear healthy. B Only a small amount of undesirable species, such as feathertop. C The prickle bush growing in the background is an indicator of the heavy soils on which this pasture type is found; Mitchell grasses are not evident, confirming the pasture type determination; this pasture is lightly grazed, however, the high density of desirable species would still be obvious under a higher utilisation rate, so the condition would still be assessed as good.

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Fair: Prolonged heavy grazing on the preferred ribbon grass and bundle-bundle plants reduces their density and in fair condition, the intermediate species are more prominent. The lower density and smaller size of desirable plants allow an increase in undesirable plants, such as feathertop and rubber bush. Bare patches may become more obvious (Figure 2).

Figure 2 Ribbon grass alluvial plain pasture in fair condition in the Kimberley (photograph taken June 2008). A The density and vigour of desirable perennial grasses are reduced. B There is an increased number of undesirable plants, such as feathertop. C There are more patches with no perennial grass cover; Mitchell grass butts are not evident, confirming the pasture type.

Poor: In poor condition, ribbon grass and bundle-bundle plants are infrequent, often stunted and lacking vigour. Sometimes undesirable perennial species, such as feathertop, can dominate. Alternatively, there may be significant bare areas or large areas with annual grasses, such as Kimberley couch. Intermediate species have declined or may have been grazed out and grazing may even be evident on feathertop and rubber bush, which are species of low palatability (Figure 3).

Figure 3 Ribbon grass alluvial plain pasture in poor condition in the Kimberley (photograph taken May 2008). A Ribbon grass is sparse and stunted, showing evidence of heavy grazing. B The undesirable perennial, feathertop, remains. C There are large areas of bare ground; Mitchell grass butts are not evident, confirming the pasture type determination.

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Associated plants