Effects of cattle browsing on Terminalia sericea-dominated woodlands in a semi-arid region of the Kalahari, Namibia

Type Thesis or Dissertation - Doctor of Philosophy
Title Effects of cattle browsing on Terminalia sericea-dominated woodlands in a semi-arid region of the Kalahari, Namibia
Author(s)
Publication (Day/Month/Year) 2006
URL http://scholar.sun.ac.za/handle/10019.1/50604
Abstract
Livestock farming affect plant growth and soil condition around artificial water points in arid and semiarid
environments. This study investigated the following, in the northern Kalahari, Namibia: 1) the
impact oflivestock on soil condition, vegetation structure and composition with reference to artificial
water points; 2) cattle browsing preference on pre-rain flush during the hot-dry season; 3) the
independent and interactive effects of plant damage, soil nutrients and moisture content on tolerance
and resistance traits of Terminalia sericea. Condensed tannin was used as a measure of resistance trait,
while growth parameters were used to measure tolerance of (herbivore) damage. This experiment was
carried out in small camps in the field where plant damage and soil nutrients were controlled, and (4)
under nursery conditions where in addition to plant damage and soil nutrients, soil moisture was also
controlled. The nursery experiment was carried out on 19 month-old seedlings of Terminalia sericea;
and 5) the perception and knowledge oflocal pastoralists on vegetation change and utilization of woody
plants was assessed. The key results of the study are summarised in the sections below:
Impacts of livestock around artificial water points in the northern Kalahari
Livestock activities near artificial water points had significant impacts on vegetation and soils. Fewer,
but tall trees with broader canopy areas grew near the water points. Herbaceous abundance increased
with proximity to the water points, but species diversity of both herbaceous and woody plants was 55
and 29 % respectively of the diversity measured from 600-4000 m from the water points. Soil organic
carbon and nitrogen content was generally higher at 10 - 20 cm depth near the water points than at
lower depths, while soil moisture changed little across the soil profile and farther away from water
points. Available phosphorus in the 10 - 20 cm soil layer was significantly higher at 200 m from water
points than at any other depth and distance from water points. This may have resulted from livestock
dung deposition. Long-term observations by pastoralists revealed that the density of woody vegetation
Stellenbosch University https://scholar.sun.ac.za
iv
and composition of plant community have changed substantially all over the rangelands since the
commencement of sedentary settlements around the anificial permanent water points some 32 to 51
years ago.

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