ACHIEVEMENTS
PhD Study Reveals a Grassier
Eastern Karoo
Christine Cuénod
Current Address: Networking Facilitator, Friends of UKZN Agriculture,
University of KwaZulu-Natal, Pietermaritzburg
Email address: [email protected]
Reprinted From: http://bit.ly/37d5VK6
R
esearch conducted by Dr Justin
du Toit for his PhD in Grassland
Science shows that as the climate
changes, grassiness in the semi-arid Ka-
roo is on the rise. His study investigated
factors influencing the botanical com-
position of the eastern Karoo, including
rainfall, grazing by livestock, and the im-
pact of minimum temperatures on shifts
in vegetation, while also examining the
potential increased chances of fire.
Du Toit is based at the Department
of Agriculture, Forestry and Fisheries’
Grootfontein Agricultural Development
Institute in Middelburg in the Eastern
Cape, where he conducts and publishes
research on vegetation-related aspects
of the Karoo. His study was supervised
by Professors Kevin Kirkman and Tim
O’Connor, and will be relevant to re-
searchers, managers, farmers and con-
servationists in the Karoo.
He said that the aim of his study was
to gain a better understanding of how
Karoo vegetation works and thereby
contribute new knowledge on the con-
sequences of management interven-
tions such as livestock grazing, natural
background drivers such as rainfall and
drought, and emergent factors that can
be controlled to a point, such as fires.
times less shrubby, and boasting health-
ier veld from the 1960s to the 2010s.
Periods of rainfall decline resulted in
more pronounced grazing effects, with
heavy summer grazing damaging the
veld and increasing the amount of bare
ground, as opposed to less damaging
grazing spread out over the year. Win-
ter grazing resulted in grasses thriving
and shrubs becoming less common.
Increased rainfall rendered the results
of grazing less pronounced; even dam-
aged veld recovered considerably and
boasted good botanical diversity. Du
Toit concluded that rainfall was the pri-
mary driver of vegetation condition, but
that grazing has an important second-
ary effect that is especially pronounced
during dry times.
Since rainfall increases the growth of
flammable grasses and therefore the
chance of fire (an important considera-
tion as climate change is predicted to
increase the incidence of wet periods as
well as droughts), du Toit examined the
influence of an accidental fire at Groot-
fontein. He found that while fire did not
change the overall number of species,
it caused major shifts in which spe-
cies were dominant, noting that many
shrubs took many years to regain their
original size.
Du Toit also investigated whether mini-
mum temperatures (and frost) corre-
lated with shifts in vegetation, finding
that despite background warming re-
sulting in longer growing seasons and a
general increase in temperatures, there
was no correlation between the length
of the growing season and changes in
vegetation.
This research has resulted in 12 publi-
cations and presentations, including in
the African Journal of Range and For-
age Science, the South African Journal
of Botany and at the Annual Congress
of the Grassland Society of Southern
Africa.
Du Toit extended special thanks to two
people among the many that contrib-
uted to his research. Grootfontein’s resi-
dent Karoo ecology expert Dr Piet Roux
was instrumental in du Toit’s research
and in providing insight into the re-
gion, while he described co-supervisor
O’Connor as providing amazing guid-
ance, direction and insight, and said
that it was an honour to work with him.
Figure 1: Dr Justin du Toit
received a PhD in Grass-
land Science. Photo:
supplied
He explained that the increase in grassi-
ness in the Karoo over the past few
decades is generally seen as a positive
development. He investigated a num-
ber of factors that contributed to this,
beginning by using rainfall records dat-
ing from 1888 to establish that rainfall in
recent decades has been notably high-
er, and droughts less common. He also
found strong evidence of cyclical rainfall
patterns, with the clearest cycle about
20 years long.
Combining the effects of livestock graz-
ing with rainfall effects, du Toit used
long-term data to reveal that increased
rainfall had resulted in the eastern Ka-
roo becoming much grassier and some-
03
Grassroots
Vol 19
No 4
November 2019