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Abstract

Mitchell Grass pastures are valued for their high carrying capacity and traditionally there has

been some reluctance to use fire in their management. The effects of fire in a cattle grazing

context were documented on Flora Valley station, in the East Kimberley region of Western

Australia.

Two sets of sites (0.13 ha), paired on either side of an access track, were established within

each of two ‘black soil’ paddocks. These were subject to normal station management. Plant

frequencies were monitored in most years over 1995-2010, using a protocol similar to that for

grassland sites in the Western Australian Rangeland Monitoring System (WARMS). Pasture

composition and total standing dry matter (TDSM) were also estimated.

The number of fires at individual sites varied from one to seven; timing of fires varied from

August to November. Most had no detectable effect on the frequency of two key perennial

species – Astrebla pectinata (Barley Mitchell Grass) and Chrysopogon fallax (Ribbon Grass).

Ribbon Grass frequency increased over the study at five of six sites where it was initially

recorded. At one site, a reduction in Ribbon Grass frequency following a small-scale fire

appeared to be associated with heavy post-fire grazing. There was some evidence that fires in

one year may have reduced the subsequent frequency of Flinders Grass (Iseilema

vaginiflorum), a useful annual. Values of TSDM at sites burnt in the previous year were

extremely low in two years with below average wet-season rainfall, highlighting the need for

careful assessment of risks when planning fire management for these pastures.