NEWS
Investigating long-term
(>35 year) woody vegetation
change around watering points
in the Kalahari Gemsbok
National Park
Dr Helga van der Merwe (SAEON) and
Dr Hugo Bezuidenhout (SANParks)
E-mail Addresses: [email protected] and [email protected]
Reprinted From: http://bit.ly/2zgR8yo
F
rom 1978 onwards, numerous sur-
veys have been conducted in the
Kalahari Gemsbok National Park to
gain insight into the medium- and long-
term changes in the vegetation, in par-
ticular within the piosphere surrounding
artificial watering points.
The hypothesis is that provision of artifi-
cial watering points generally promotes
heavy concentrations of wildlife around
the watering point, resulting in the deg-
radation of herbaceous vegetation and
bush densification.
Woody species most commonly as-
sociated with bush densification in the
Kalahari environment are Senegalia
mellifera (Acacia mellifera), Rhigozum
trichotomum and Grewia flava. Vachellia
erioloba (Acacia erioloba) is also often
mentioned as a plant species that could
densify in this region.
Artificial watering points have been pro-
vided in the Kalahari Gemsbok National
Park since the 1930s and the long-term
impact of these watering points on the
vegetation is unknown for such a large
conservation area (9 600 km²).
nearly four decades.
The study found that regardless of
distance from the watering point, the
density of large Vachellia erioloba and
Vachellia luederitzii (Acacia luederitzii)
individuals decreased with successive
surveys. This long-term study over more
than 35 years shows that no evidence of
bush densification was found at the ar-
tificial watering point for any of the spe-
cies known to densify in the southern
Kalahari.
Vegetation dynamics in this large con-
servation area therefore differ from
those found in agricultural landscapes,
where bush densification is common.
Additionally, it was determined that af-
ter nearly four decades, woody vegeta-
tion composition showed only a slight
directional trend at one site away from
the watering point.
The good collaboration between SAN-
Parks and SAEON has enabled the re-
newal of existing datasets, allowing for
the analysis and interpretation of data
to better understand vegetation dy-
namics in the Kalahari environment.
Figure 2: Undisturbed Kalahari vegeta-
tion away from an artificial watering
point (Photo: Helga van der Merwe)
Good collaboration
Investigating changes in the vegetation
This study aimed to establish whether
densification in the park occurred over
time at the Dankbaar artificial watering
point, opened in 1959, compared to
two sites about 5 km from the watering
point. Additionally, change in woody
species composition and density was
investigated to determine whether any
directional trends were evident after
Grassroots
Vol 18
No 4
Figure 1: Piosphere (area denuded of
vegetation) around an artificial watering
point in the Kalahari Gemsbok National
Park (Photo: Helga van der Merwe)
December 2018
10