Euston-Brown, D., Rathogwa, N & Richardson ... - DWA Home Page

66
Region Site Name Peg GPS South
Kruger Park Sabie River Pump
Station
Appendix 1
(o)
GPS
East (o)
103 24.01881 31.24925 Granite Lowveld
(SVI3), Lowveld
Riverine Forest (Foa1)
SA Vegetation type Notes and insights:
Kruger Park Lower Sabie on S3 24.97004 31.40896 Granite Lowveld
(SVI3), Lowveld
Riverine Forest (Foa1)
Kruger Park Lower Sabie Road 165 24.97934 31.64558 Granite Lowveld
(SVI3), Lowveld
Riverine Forest (Foa1)
Kruger Park Lower Sabie
Bridge
Kruger Park “Lower Sabie
Camp”
74 25.12238 31.92529 Granite Lowveld
(SVI3), Lowveld
Riverine Forest (Foa1)
143 25.09870 31.88118 Granite Lowveld
(SVI3), Lowveld
Riverine Forest (Foa1)
Kruger Park Picnic Spot 158 25.00010 31.77221 Granite Lowveld
(SVI3), Lowveld
Riverine Forest (Foa1)
9.1.3 Results
Show case best approaches
Lantana cleared, but 5 other alien
weeds have increased cover
Clearing done, six more (total 10)
other alien weeds have invaded,
Peg missing, site burnt
Chromolaena gone but many
weed species are still present,
peg missing
Lantana cleared, browsing by
hippo
Effective clearing, peg missing
No clearing, other exotic weeds
increasing cover
9.1.3.1 Assessment of the effectiveness of clearing methods currently used
A summary table of the data is provided in Annexure 1. This data has been very briefly analysed
below by grouping the plots into those that were cleared and not cleared during the sample interval
(2004-2006). Based on this and the clearing experiments the conclusion is that most clearing methods
currently being used are effective.
Table 2: The average and standard deviation of the difference in cover or number of species between 2004 and 2006
for a range of growth forms and aliens. Results show averages for plots where no clearing happened (no
interference occurred) compared with where clearing did happen between 2004 and 2006 (interference).
Difference in % cover and number of species for a range of alien and indigenous vegetation categories
between 2006 and 2004 (2006 minus 2004)
% grass % chromo- % lantana % other no. of other tree grass herb
cover laena cover cover alien cover alien spp diversity diversity diversity
No interference N=32 2 ± 25 15 ± 30 1 ± 11 7 ± 16 1 ± 1 3 ± 4 1 ± 2 2 ± 5
Interference N=25 23 ± 36 -14 ± 41 -6 ± 21 11 ± 19 1 ± 3 3 ± 5 1 ± 2 2 ± 3
Table 2 shows that overall, clearing does reduce the cover of chromolaena and lantana, but not other
alien invasive plants. This is probably related to the phenomenon whereby recently cleared plots are open
to invasion, and accumulate opportunistic weed species as well as indigenous plants, especially after good
summer rain (see Figure 1). Indigenous grass cover increased more where clearing happened. There was
a slight increase in tree, grass and herb diversity for both cleared and uncleared sites. The increase in
grass cover could be regarded as a positive sign in terms of using fire as a control method.
Based on the increase in other alien plants in even cleared plots, there does appear to be a shortage of
understanding of the threat posed by other emerging weeds. In many cases these weeds are left alone,
and only specified target species are controlled. This is a flaw in training and management that urgently
needs to be rectified.