Sallow Wattle! (“Not-Friend” of the Grampians)

On 5/02/2017 PhD student Samantha Barron gave us a very interesting presentation on her research into Sallow Wattle, (Acacia longifolia), which has become extremely invasive in many parts of the Grampians since the 2006 fires. Samantha mentioned that it is also invasive in more than 20 countries around the world, where it has been introduced for things such as dune stabilisation, tannin production and for ornamental reasons.

The more we know about it, the better we may be able to manage it long-term, and this has been, and is, the overall focus of her research.  Samantha’s aims are to determine which environmental factors help it, and to compare functional traits and genetic differences of the species within its home and invaded ranges; a further aim is to look at its competitive abilities under different climate change scenarios.

One characteristic helping plants to become invasive is being “disturbance adapted”. Acacia longifolia, which includes ssp longifolia and sophorae, is top of the tree for being disturbance adapted ….. Hello Grampians! Fires, floods, you name it, the Grampians excels in disturbance. Fire especially seems to suit Sallow Wattle propagation.

Other factors driving invasiveness include:

  • Fast growing
  • Reproductive maturity of less than 2 years
  • Large, viable seed production
  • Nitrogen fixation
  • Adaptability
  • Allelopathy (the chemical inhibition of one plant by another, due to the release of substances acting as germination or growth inhibitors).

Sallow Wattle appears to have the lot!

Biological control possibilities include (seed eating) weevils, flies, gall-inducing wasps, rust fungus, and stem-boring insects.

Samantha’s research highlights many more questions ….. ie:

  • Which areas are most at risk
  • Where will the species do best
  • Where is it going to increase in abundance and distribution
  • Where energy should be directed for control measures …… such as, where it is a danger to threatened species, and along waterways, where it thrives.

Two studies are in the pipe-line:

  1. Mapping, and predicting plant health by Parks
    The fascinating Chlorophyll Fluorescence measuring tool is assisting as a measure of plant health, (we’d all like one but Samantha tells us they are expensive)
  2. CO2 and drought study; e.g., how well does Sallow Wattle do with/without water??
    There are so many variables. For example, in open heathland, the species doesn’t have to grow as tall as in wooded areas, but it gets no shade once it has outgrown the heath.

Many thanks to Samantha, and her hard-working assistant Josh, for this research and presentation. We wish them all the best as they continue this research.

FOGGs have a strong commitment to encouraging and supporting research into the biodiversity of our Park. Samantha was not one of the students we supported financially, but whose work is so important and we will help with any followup work if needed. We hope to have at least one student presentation on our calendar each year.

Some of us are helping Park research with photomonitoring of Sallow Wattle at different sites. We each have a list of GPS points where a starpicket has been hammered in so that at regular intervals we can take a photo pointing in the same direction. Over the years this will become a valuable record of where it is or is not flourishing.