Friends of The Pinnacle   defeating the weed menace
fotpin's Native Grass Restoration Project
 
  

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Restoring native grasses to the understorey of The Pinnacle
New knowledge that will aid recovery of degraded box-gum grassy woodlands

A Friends of The Pinnacle project funded by:
ACT Environment Grant 2010-11
Caring for Our Country Community Action Grant 2010-2011
Canberra Labor Club 2010-2011


Results of Plant and Nutrient Surveys, 2011 - 2013

Quick Summary:

  • Generally, if nutrients can be reduced native species are expected to benefit.
  • None of the treatments tested have made a clear improvement.
  • Grazing at current levels maintains species richness (of exotics and natives)

 

[ NB: for background see the methodology and experiment design ]

The effect of soil nutrients on plant species composition

 

The measured nutrient values at the beginning of the experiment were compared statistically with the composition of plant species at the same time.

The number of native species present was smaller for larger concentrations of the plant nutrients Nitrogen, Phosphorus and Carbon.

While there was no relationship with the nutrient level as a whole, the number of exotic species was larger for larger Nitrogen concentration in the soil.

nutrients effect on number of exotic species nutrients effect on number of exotic species
  • Although the number of native species overall was severely reduced by high nutrient levels, some native species did better at high nutrient levels.
  • Similarly, although exotic species increased with higher nutrient levels, some exotics did better at low nutrients Some natives do better at high nutrients.
  • The type of nutrient matters.

Summary: This finding suggests that while on average it will benefit native species to reduce nutrients, the actual outcome of any attempts to reduce nutrients is likely to depend on whether those attempts reduce Phosphorus and Carbon or Nitrogen.

The effect of the applied treatments on plant species composition

Effect on number of native species

 

  • Any kind of disturbance resulted in more species
  • Prevention of grazing resulted in a smaller number of species, although this was only significant for the control (without other treatments)
  • Although not statistically significant, sugar application appeared to reduce the decline in the number of species when grazing was prevented

 

 

See below for a note on interpretation of the charts.

treatment effects on native species

Effect on number of exotic species

 

  • Any kind of disturbance resulted in more species
  • Prevention of grazing resulted in a smaller number of species, although this was only significant for the control and sugar treatment

 

 

See below for a note on interpretation of the charts.

treatment effects on exotic species

Effect on native species cover

 

  • Sugar increased cover when not grazed

 

 

See below for a note on interpretation of the charts.

treatment effects on native species

Effect on exotic species cover

 

  • Slashing increased cover for both grazed and ungrazed treatments

 

 

See below for a note on interpretation of the charts.

treatment effects on exotic species

Interpreting the charts above

Column labels

Columns are labelled as the treatment, followed by the letter "f" for fenced (ie ungrazed) or "o" for open (ie grazed).

For example, "crop:o" represents the grazed cropped treatment.

statistical significance

The error bars on the graph indicate the confidence in the mean values represented by the columns

The letters above the columns indicate whether columns are statistically significantly different from each other.

  • Columns with the same letter above them are not significantly different from each other
  • Columns with different letters above then are significantly different from each other

For example, in the effect of treatment on exotic species cover immediately above, "crop:f" and "slash:f" are not significantly different (both have the letter "e" above them), whereas "crop:f" and "sugar:f" are significantly different (because they have no common letters).

 

Summary: The experiment has confirmed our expectations that:

  • Disturbance, whether by grazing, fire, slashing or cropping, increases the number of species of both exotic and native plants.
  • Grazing exclusion decreases the number of exotics and native species,
    but, if grazing is prevented, adding sugar prevents number of native species declining as much as the exotic species.

 

Conclusions
  • Generally, if nutrients can be reduced native species are expected to benefit.
  • None of the treatments tested have made a clear improvement.
  • Grazing at current levels maintains species richness (of exotics and natives)

 

Where to from here?

A small working group has been formed to discuss options to further this research.

Please contact if you would like to be involved in these discussions.

 

project home methods & implementation plot map current activities findings full project description
[pdf, 274 kB]

 

 
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