Issue Number #32
Issue Date Winter 2005
Number of Articles Online 1 Articles
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Title To Mow or To Graze Grassland?

The following is a summary of a paper in Austral Ecology.

Lowland native grasslands and grassy woodlands have been severely depleted in area and condition through-out their original range in south-eastern mainland Australia and Tasmania. One of the few remaining native tussock grasslands on basalt occurs in the Pontville Small Arms Range Complex (PSARC) at Pontville, owned by the Department of Defence. The use of PSARC as a small arms range has been combined with a grazing lease, with stock excluded from the range for the sake of their health. The small arms range is mown at high frequency, and the slash removed after mowing, to avoid grass fires.

As temperate grassy ecosystems require disturbance to maintain species diversity, a study was done to determine whether frequent mowing with removal of slash is a better option for lowland tussock grassland management then a moderate level of sheep grazing.

Quadrants were established on each sides of a fence between the mown area and the grazed area in order to compare plant species richness and abundance.

The results found that species richness was greater on the mown than the grazed side of the fence. As well, the abundance of native herbs and grasses, and perennial exotic grasses and herbs, was greater on the mown side of the fence. The mowing regime was significantly more effective than the moderate grazing regime in promoting perennial cover, probably by limiting establishment space for annuals.

The mowing regime is definitely superior in its conservation outcomes to the grazing regime. The mowing regime produces greater cover of rare or threatened species, greater native cover and less exotic grass cover. It thus presents an opportunity for maintaining or improving the condition of previously grazed remnants in reserves without resorting either to the use of stock or to fire.

The key to using mowing as a successful conservation tool in lowland native grasslands seems to be the removal of slash, as this reduces the nutrient status of the ecosystem, which discourages weed infestations. It also ensures that the intertussock space is bare ground, rather than smothered with litter.

Reference: Verrier,F.J. and Kirkpatrick, J.B. Frequent Mowing is better than grazing for the conservation value of lowland tussock grassland at Pontville, Tasmania. Austral Ecology, (2205), 30, 74-78

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