Vegetation

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Vegetation

There are nine broad vegetation types in the Darling catchment.  However, between Brewarrina and Wentworth, the vegetation is dominated by grasses, shrubs, Mallee and Belah woodlands and riverine woodlands.

The riverine woodlands are dominated by River red gums which generally occupy a narrow band along sections of the Darling River, particularly around lakes and water courses. Blackbox woodlands occur on slightly higher parts of the floodplain.

Mallee shrubland vegetation is dominated by multi-stemmed eucalyptus and occurs along the lower Darling sandy rises and dune fields.

Belah woodlands occur between the sandy dunes and most have been heavily grazed.  Regeneration of many associated tree and shrub species is rare.  Many hollows in these tree and woodland species provide habitats for bats and birds.

Surprisingly, grasslands are not a dominate vegetation type in the lower Darling, but have proved remarkably resilient under grazing. The composition of grasslands may change seasonally or according to climate, but for much of the year, the ground may remain bare.  Native grasses such as Spear Grass can be very abundant following rains.

Shrublands can form dense thickets on disturbed areas and may also include introduced herbs and grasses.  It may also include Saltbush shrublands on dry lake beds.  Where the vegetation has been laid bare and overgrazed, saltbush and introduced grasses and herbs often predominate.

Most of the vegetation of this area has been subjected to overgrazing by stock, feral animals and increased numbers of kangaroos for over 100 years.  Grazing has had a major impact on most vegetation communities.  While the death of trees is a noticeable effect of vegetation decline, the loss of understory from woodlands and changes in grasslands and shrublands often go unnoticed.

Heavy grazing has also led to soil degradation including gully erosion and wind erosion.  Many of the plants in this area are long-lived, but continual grazing pressure can lead to their elimination.  Several species in the semi-arid woodlands are currently at risk.  Cropping is also a threat to plant communities along the Darling because it completely removed native vegetation and prevents regeneration.  Cropping is mostly confined to the heavier soils of dry lake beds, but is also occurring on lighter soils in the lower Darling.  Small areas in the lower Darling have also been cleared for irrigated horticulture.

Much of the riverine floodplain vegetation depends on periodic floods but has been affected by changes to natural flows in the Darling River.  Some permanently flooded areas have resulted in the death of trees and increases in sedges and rushes.  Areas receiving no water have seen restricted germination of native trees and shrubs.

The widespread provision of watering points for stock has had a significant influence of native vegetation, particularly in the lower Darling. However, more reliable water has also led to a significant increase in kangaroo numbers and allowed stock and feral animals to graze these areas for longer periods.


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