Individual study: Effects of sowing treatment and landscape position on kangaroo grass Themeda triandra establishment in degraded Eucalyptus woodlands at Dripstone, Cowra, Harefield and Burrumbuttock, New South Wales, Australia
Cole I., Lunt I.D. & Koen T. (2005) Effects of sowing treatment and landscape position on establishment of the perennial tussock grass Themeda triandra (Poaceae) in degraded Eucalyptus woodlands in southeastern Australia. Restoration Ecology, 13, 552-561
In Australia, primarily due to agricultural development and livestock grazing, native grassy eucalypt woodlands are often degraded. There are no reliable techniques to restore grassy and herbaceous understorey species over large areas. Re-establishment of dominant native grasses such as the perennial kangaroo grass Themeda triandra is particularly important as it competes strongly with non-native species. This study compared Themeda establishment using a variety of sowing techniques at upper, mid- and lower landscape positions in degraded woodlands of central New South Wales.
Study sites: Four localities (Dripstone (near Wellington), Cowra, Harefield (near Wagga Wagga) and Burrumbuttock (near Albury)) were selected. The average distance between localities was 145 km. At each locality, three different landscape positions were selected (upper, mid- and lower) giving a total of 12 sites.
Experimental design: A randomized block experiment was established with five replicates of five seedbed treatments : combinations of soil disturbance (disturbed, non-disturbed) and weed control (atrazine, nonatrazine), plus topsoil scalping followed by soil disturbance. Plots were 4 x 2 m a in 20 × 10 m block.
Pre-treatment management: The sites were slashed at the end of September 2000 to remove most standing herbaceous vegetation and glyphosate sprayed. A week prior to sowing, plots were mown to 3 cm height and clippings were removed (to simulate heavy grazing).
Treatment application: In October 2000, scalping and disturbance treatments were applied, and seed (a seed-floret mix harvested by brush harvester from a local Kangaroo grass Themeda triandra grassland) was spread at a rate of 22 germinable seeds/m² . Disturbance was achieved using a single pass of a four-tyne scarifier. In the scalping treatment, the topsoil was removed by shovel to 5 cm, followed by a single scarifier pass. The atrazine treatment was applied immediately after sowing, 1.8 kg a.i./ha applied by knapsack sprayer.
After 117 days, all plots were sprayed with atrazine to control weeds.
Kangaroo grass established in all plots and establishment was not significantly affected by landscape position, despite significant differences in non-native cover between sites.
The scalped/disturbed treatment resulted in significantly better establishment at 400 days (18% or 3.9 plants/m²) than the control (8% or 1.8 plants/m²). Other treatments did not differ significantly from the control.
Results indicate that Themeda grassland can be re-established in degraded eucalyptus woodlands relatively simply. Themeda established on all plots, and contrary to expectations, landscape position did not influence establishment success.
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