The experiments described in this thesis were designed to assess changes in pasture
dynamics (biomass and species composition of pasture) of grazing land on the Southern
Tablelands of ACT and NSW, after 16 combinations of rabbit control treatments had been
applied. The rabbit control performed by CSIRO Division of Wildlife and Ecology
consisted of all combinations of presence-absence of Poisoning (using sodium
monofluoroacetate, 1080: POIS), Ripping (ripping warrens using a tractor fitted with
ripping tynes: RIP), Fumigation (pressure fumigation using chloropicrin: FUM) and
repeated follow-up fumigation (using phostoxin pellets one, six and eighteen months after
completion of the initial treatment: ANN). The pasture was assessed before treatments
were applied, and every six months after rabbit control treatments. Treatment
combinations were assigned randomly in a 24 factorial design on a total of 32 sites.
There was a significant increase of pasture biomass at the RIP+ANN treatment at
post-treatment sample 5. The analysis of covariance did not detect any other significant
increase or decrease of pasture biomass for any rabbit control treatment, at any posttreatment
sample.
A significant increase of grass species occurred for the treatments of
POIS+RIP+FUM, POIS and RIP+ANN for the post-treatment samples of 1, 3 and 5
respectively. There was a significant increase of thistles at the rabbit control treatments of
POIS+RIP+FUM+ANN (post-treatment sample 1), RIP, ANN, RIP+FUM,
RIP+FUM+ANN and POIS+RIP+FUM+ANN (post-treatment sample 3) and RIP and
FUM+ANN (post-treatment sample 5). A significant increase of weeds occurred at FUM
(post-treatment sample 3) and at FUM+ANN (post-treatment sample 5). No significant
changes in the amount of herbs or legumes was apparent for any rabbit control treatment or
post-treatment sample. There were no significant decreases for any species group. Except
for the significant results for post-treatment sample 1, all significant increases of biomass
for any species group occurred during spring (post-treatment sample 3 and 5) which
suggests a growth phase during spring then subsequent dieback (particularly for thistles and
weeds), as any change was not detected in the following autumn sample. No strong trend
is evident for any particular rabbit control treatments, or any combination of treatments.
Analysis of covariance revealed that the rabbit control treatment of RIP+ANN
showed significant increases in both total biomass of pasture and grass biomass during
post-treatment sample 5. This treatment reduced the number of active entrances the most.
Significant positive correlations were found between pasture biomass (total) with
grass, herb, legume, thistle and weed species groups. Significant negative correlations
between grass biomass and the number of active entrances were found when the rabbit
control had been highly effective in reducing the number of active entrances. When rabbit
control had not been very successful, there was a significant positive but low correlation
with the number of active entrances. There was no significant relationship between the
number of active entrances with the weight of rabbit dung pellets. It is reasoned that they
are different measures of rabbit abundance. More rabbit dung pellets were found closer to
the warren than further away from the warren, but there was no correlation between rabbit
dung and pasture biomass.
Rainfall was above average for most of the experiment, biomass increased
accordingly, and rabbit control was highly successful. The resulting changes in the pasture
were difficult to detect, although some increases in species composition groups occurred.
It is reasoned that the changes observed are partly attributable to seasonal conditions, and
to high rainfall. Grazing by domestic animals, sheep and cattle, had been found to be
consistent throughout the experiment.
| Identifer | oai:union.ndltd.org:ADTP/219533 |
| Date | January 1993 |
| Creators | Brown, Peter Robert, n/a |
| Publisher | University of Canberra. Resource & Environmental Science |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | ), Copyright Peter Robert Brown |
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