map

Pastures in North East Queensland

Pasture composition

Pastures vary greatly across this region as a result of the unevenness in soil fertility, which varies because of the different climatic and geological topographical characteristics across North East Queensland. The Great Dividing Range, as well as other ranges, also contribute to the diversity in landform. In general, the more fertile areas are found on the river floodplains or are associated with basalt-derived soils in the south of the region and to the north-west of Charters Towers. Topographic and drainage characteristics can also vary greatly within relatively small areas, particularly in areas adjacent to the Great Divide.

Regional variation in pastures

The northern third of the region is broadly dominated by tropical/subtropical perennial tallgrass, and black/bunch speargrass (Heteropogon contortus) pastures in particular.

Along the coast, there are swards of saltwater couch (Sporobolus virginicus) grasslands which occur in areas of periodic tidal innundation. These areas consist almost entirely of saltwater couch with some sedges and rushes, river grass and native millet (Panicum decompositum).

Blady grass (Imperata cylindrica) is another pasture community type which typically occurs in areas closer to the coast and with rainfall generally above 1100 mm per year. Grasses characteristic of this community include blady grass, giant speargrass (Heteropogon triticeus), northern canegrass (Mnesithea rottboellioides) and kangaroo grass (Themeda triandra).

Black speargrass

The most significant pasture for the region is black speargrass, which occurs in areas of rainfall between 700 and 1200 mm. Grasses include black speargrass, desert bluegrass (Bothriochloa ewartiana), kangaroo grass, giant speargrass and pitted bluegrass (Bothriochloa decipiens).

Abundance of these palatable species is greatly influenced by management practices. As this represents the most extensive native pasture community of the North East Queensland region, it is concerning that significant changes in composition have occurred, including increases in annuals and broad-leafed weeds. Indian couch (Bothriochloa pertusa (L.) A. Camus), an annual, in particular has been replacing perrenials in many heavily grazed areas.

Schizachyrium pastures

In the far north of the region, bordering Cape York, are Schizachyrium pastures. These are dominated by Schizachyrium species, but incorporate wiregrasses (Aristida spp.), giant speargrass, native sorghums (Sorghum spp.), black speargrass and goldenbeard grass (Chrosopogon fallax).

Aristida-Bothriochloa pastures

Black speargrass pastures merge into Aristida-Bothriochloa pastures in the west of the region. This pasture community is very diverse, and includes desert bluegrass, wiregrasses, goldenbeard grass and kangaroo grass (Themeda triandra). Some spinifex (Triodia pungens) pastures occur in the south west of the region growing on sands or skeletal soils, which grade into the Aristida-Bothriochloa pastures. In addition to the spinifex there often exists a mosaic-like pattern of buck spinifex (Triodia mitchellii), wiregrasses and desert bluegrass.

Brigalow and softwood scrub

In the centre of the area, south of Charters Towers, and especially south of the Cape River, brigalow and softwood scrub dominated in the past. Gidgee was common to the west and blackwood was common north of the Suttor River. However, much of this scrub was cleared for cropping and sown pastures. Remaining areas of native pastures in this central region include brigalow grass and fairy grass (Sporobolus australasicus). To the west of this central area gidgee scrub was prevalent, although large areas have now been cleared to make way for sown pastures. Grasses under gidgee are similar to those under brigalow, but may also include desert bluegrass and slender bluegrass.

Bluegrass

To the south of the Bowen-Broken Rivers region, there were significant areas of Queensland bluegrass (Dichanthium sericium) pastures, although much of this has now been cleared for crop cultivation. Remaining areas may also contain other bluegrasses, coolibah grass, feathertop (Aristida latifolia) and white speargrasses. Flinders (Aristida spp.) and Mitchell grass (Astrebla spp.) may also be significant locally.

Further north, areas of this pasture remain on the basalt plains and plateaus between Charters Towers and Mt Garnet. Other grasses may include cane grass, browntop (Eulalia aurea ) and black speargrass.

Mitchell grass

Finally, areas of Mitchell grass pasture are common on the western boundary, generally dominated by bull Mitchell and curly Mitchell (Astrebla lappacea). Flinders grasses may also form an important component.

Changes in composition of native pastures

As a result of high stocking rates there have been significant changes in the composition of native pasture in this region. These include increases in annuals and broad-leafed weeds. Indian couch (Bothriochloa pertusa) has replaced perrenials in many overgrazed areas. There have also been dramatic increases in the percentage of wiregrasses in these pastures. Of particular concern is the black speargrass communities as they represent the most extensive native pasture community of the region, and are associated with woodlands and open forests of eucalypts.