Pindan pastures in the Kimberley, Western Australia

Pindan pastures

These pastures are part of the Kimberley red soil group - spinifex pastures: soft spinifex and curly spinifex are the identifier grasses. Use the interactive key to pasture condition to help identify pasture type.

Pastoral value

Pastoral value of Pindan pastures is moderate. Forage value is adequate for stock growth during the wet season, with ephemerals and herbs providing reasonable quality forage. During the dry season, the palatability and quality of the forage declines and the pasture provides a sub-maintenance ration for stock.

Pindan pastures in good or fair condition are stable and resilient under grazing and provide a good drought reserve. Pindan pastures can be stocked heavily over the wet season to allow other pastures with greater pastoral value to be spelled. However, continuous (year round) heavy grazing will quickly remove the more palatable legumes and other forbs that provide reasonable nutrition for stock.

Recovery of Pindan pastures in poor condition at the paddock to regional scale is difficult. Where Pindan pastures were historically overgrazed by sheep, recovery has been very slow (>100 years) and the pastures are still dominated by annual plants and undesirable grasses in 2012.

Occasional burning once every three to five years will encourage the growth of forbs and annuals. Too frequent cool burns will thicken the acacias and encourage annual sorghum (Sorghum stipoideum). A hot fire late in the season will control the acacias but may also kill the perennial grasses so should be used with caution. Fires should be patchy and stock should be kept off recently burnt areas to give the grasses time to re-establish.

Management

Pindan pastures are of most use to stock when used in a rotational grazing system where the pasture is grazed then spelled. Pindan pastures are accessible over the wet season and can be usefully grazed over the wet season when more productive pastures are not accessible. If Pindan pastures are grazed over part of the wet, they should then be spelled to allow seed set. Overgrazing will cause the ribbon grass butts to decline in vigour; under heavy grazing pressure, they will disappear over a few years. When these pastures are burnt, cattle should be kept off until plants have re-established to a size where they won’t be pulled out by the roots.

Pindan pastures are of moderate carrying capacity and can be used in conjunction with better quality pastures to provide year round forage.

Pindan pasture carrying capacity

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Distribution and soil type

Pindan is a local term used in the Kimberley to describe the association of deep red sands and an overstorey of acacia trees. Pindan pastures are mainly found in the west of the Kimberley on the Dampier Penninsula and throughout the Fitzroy valley. Pindan pastures are major pastures of the Camelgooda, Luluigui, Wanganut and Yeeda land systems and an important component on many other land systems. They also extend for some distance south from Broome. Smaller areas of Pindan pastures are also found near Halls Creek.

Pindan pastures are found on sandplain, dune fields and swales. Soils are predominately deep, red sands, or reddish sandy soils and occasionally yellowish sandy soils.

Pindan pastures are tussock, hummock or mixed grasslands with an overstorey of acacias, occurring on sandplains, dune fields and swales. Soils are predominately deep red sands, or reddish sandy soils and occasionally yellowish sandy soils. The clay content increases at depth.

Vegetation structure and composition

Note: links from common names go to a DPIRD species page, and links from scientific names go to FloraBase.

Structure and composition are variable and a function of past fire regimes, stocking history, soil types and prevailing climatic conditions. Pastures may be a mixture of tussock and hummock grasslands, tall shrublands or occasionally woodlands. In each case, the ground storey is dominated by curly or soft spinifex (Triodia bitextura or T. pungens) and ribbon grass (Chrysopogon fallax). Feathertop spinifex (T. schinzii) becomes an increasingly important component to the south of Broome.

Trees and shrubs are scattered in the swales: projected foliar cover (PFC) is less than 20%, to moderately close (PFC<30%) on the dunes and sandplain. The tree and tall shrub layer is dominated by Broome wattle (Acacia eriopoda) or sickle leaf wattle (Acacia tumida). Other trees include bloodwoods (Corymbia greeniana syn. C. dampieri or C. zygophylla), bauhinia (Bauhinia cunninghamii), beefwood (Grevillea striata) and Darwin box (Eucalyptus tectifica).

Where the soil has a lateritic gravel component, or in areas near sandstone outcrop, turpentine wattle (Acacia lysiphloia) predominates in the upper storey.

The perennial grass layer is dominated by a combination of ribbon grass and curly spinifex but other grasses such as perennial sorghum (Sorghum plumosum), white grass (Sehima nervosum), unequal threeawn (Aristida inaequiglumis), erect kerosene grass (A. holathera), wire grass (Eriachne obtusa) and woollybutt (Eragrostis eriopoda) are also common.

Assessing pasture condition

The condition of these pastures is assessed by observing the degree of ground cover (% basal cover) afforded by the grass tussocks, the vigour of the tussocks, age structure of the stand, the proportion of undesirables in the stand and the condition of the soil surface.

Pindan pastures in good condition will be dominated by curly spinifex and ribbon grass. Other grasses will include some perennial sorghum and white grass. Basal cover may be 3 to 5% or more of the soil surface.

In fair condition the distance between butts of desirable grass will increase. Few seedlings of ribbon grass and curly spinifex will be present. The size of the mature butts of ribbon grass will be smaller. Basal cover will decrease to 1 to 3%. The proportion of the intermediate grasses such as wire grass, woollybutt, and annual sorghum will increase to above one third of the stand. Undesirables such as feathertop threeawn and erect kerosene grass will become a significant part of the stand.

In poor condition there may be isolated butts of curly spinifex present but ribbon grass may have almost disappeared. The intermediate grasses such as wire grass, woollybutt, annual sorghum and undesirables such as feathertop threeawn and erect kerosene grass will dominate the stand. The stands of acacia may become dense enough to reduce the ground storey.

Rangeland condition assessment (2000-2009) and long-term monitoring data (WARMS) indicates that Pindan pastures in the Kimberley are mostly in fair to good condition in equal proportion, with some pasture in poor condition (around 15%).

Soil erosion is not usually associated with a decline in condition in these pastures. The sandy soil is porous, so there is little water run-off and the soil surface is usually protected by leaf litter.

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Pasture condition rating

Good: Pindan pastures in good pasture condition are dominated by curly spinifex and ribbon grass with even coverage. Other grasses likely to occur are perennial sorghum, white grass and soft spinifex. There is little bare ground visible and the plants appear vigorous.

Figure 1 Pindan pasture in good condition in the Kimberley (photograph taken April 2010).  A Curly spinifex and ribbon grass are abundant and vigorous; sickle-leaf wattle is a minor component; there are no undesirable plants; perennial grass density is optimal for Pindan country.

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Fair: The vigour and density of the desirable species is moderate. The coverage of perennial plants may appear patchy or uneven, with the areas in-between supporting a sparse cover of annual grasses and forbs. Intermediate species, such as wire grass, woollybutt grass and annual sorghum, are more prominent and may make up one-third or more of the stand. Undesirable species, such as unequal threeawn and erect kerosene grass, are present.

Figure 2 Pindan pasture in fair condition in the Kimberley (photograph taken 2010).  A Curly spinifex and ribbon grass are present, but less vigorous than when in good condition.  B Sickle-leaf wattle dominates the shrub layer.  C Undesirable threeawn grasses are present; the density of the desirable grasses has decreased.

Poor: In poor condition, the desirable grasses are absent or reduced to isolated butts amongst the dominant intermediate and undesirable species. Wire grass, woollybutt grass, annual sorghum, unequal threeawn or erect kerosene grass will dominate or co-dominate the stand. The acacia overstorey may become dense enough to reduce pasture growth.

It may be almost impossible to reverse the declining trend in Pindan pastures that have degraded to poor condition. 

Figure 3 Pindan pasture in poor condition in the Kimberley (photograph taken 2010).  A Erect kerosene grass dominates the grass layer.  B Broome Pindan wattle dominates the shrub layer.  C Large areas of bare soil are visible; desirable grasses are absent.

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Associated plants