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.
