Blitzing the weeds at Charles Darwin Reserve

Thursday 21 December, 2006

Andrea and Kurt Tschirner, reserve managers at Charles Darwin Reserve, report on the latest weed blitz.

Rock bridge formed by years of weathering. Photo Jiri Lochman / Lochman Transparencies.Rock bridge formed by years of weathering. Photo Jiri Lochman / Lochman Transparencies.

In August, 22 willing volunteers joined us for our annual weed blitz. The extremely dry year and a terrific effort by volunteers last year, which significantly reduced the number of seeds of weed species in the soil, meant that there were many fewer weeds to pull, chip, spray and chop than in previous years.

We targeted 23 sites on the reserve. For the most part we were treated to stunning spring days, and the visits to the weed sites were most enjoyable, especially with Sandra’s wonderful damper, cooked on the camp fire.

Having many willing hands and fewer weeds to deal with also enabled us to undertake some strategic work on erosion control. The weed problems in many areas are exacerbated by the channelling of rainwater along tracks and into areas compacted by the pressure of past grazing.

Volunteers start the construction of brush silt traps. A completed silt trap. Photos Andrea Tschirner.Volunteers start the construction of brush silt traps. A completed silt trap. Photos Andrea Tschirner.

The flowing water carries the seeds of weed species out into the surrounding bush and also creates serious erosion problems that have impacts on the condition of the soil and growth of native vegetation.

To help stem the weed and erosion problems we've begun putting in silt traps made of brush to slow down the water flow that follows heavy rain. Using branches and logs, we pack loose material into gullies and creeks where running water cuts into the surface of the soil after rain.

The sticks, twigs and leaves slow down the water to the point where it no longer has the momentum to carry away precious topsoil and, in many cases, the seeds of weed species.

After only six months we've found a lot of our traps beginning to silt up, and weeds thriving amongst the brush. This is a great help in our management of the weeds because it slows their spread into the adjacent bush and helps us to target our weed-control efforts.

Our special thanks to all our volunteers. You contributed over 550 hours of work! We greatly appreciate the time and effort every one of you put in to travel to the reserve and participate in such an important stage in the management of its biodiversity. We hope to see you all again next year. Working bees are a vital part of the management of all the reserves and we would encourage you to join one if you can.

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