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Land degradation evaluation in a game reserve in Eastern
Cape of South Africa: soil properties and vegetation cover
Fatunbi Abiodun Oluwole* and Dube Sikhalazo
University of Fort Hare, Faculty of Science and Agriculture,
Livestock and Pasture Science Department, PB X1314, Alice
5700, South Africa.
Corresponding author. E-mail:
AFatunbi@ufh.ac.za.
Accepted 8 February, 2008 |
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Land
degradation in the agricultural domains of South Africa has
attained a scale that requires scientific intervention. To
devise an appropriate control measure, we investigated the
contribution of vegetation condition and soil properties to
observed land degradation conditions. Twenty three degraded
sites were identified and classified using a land
degradation index derived from six physical degradation
indicators, using multidimensional analysis techniques. A
veldt condition assessment was also conducted on the sites.
Soil samples from the sites were analyzed for soil
degradation indicators viz., particle size fractions,
aggregate stability, organic C, pH, EC, total and
exchangeable Na, Mg, K and Ca. The veldt condition score
ranged from 26.3 – 50%, which implied that the veldt
condition has diminished by up to 50 - 77% of its standard
condition. Most of the degraded sites are poorly covered;
the percentage basal cover ranged from 12 – 39% with average
distance of 0.8 – 30.7cm between plants. The degraded lands
consisted of high (69 - 100%) proportion of increaser’s
species which was caused by selective grazing of palatable
species by wildlife herbivores. The stable soil aggregate
size ranged from 0.8 – 1.4 mm across the mechanical
disaggregation, fast wetting and slow wetting tests. Soils
of the degraded sites (poorly, moderately and highly
degraded) have low organic carbon content < 13.0 mgkg-1.
Higher quantities of Na and Ca were observed in the highly
degraded sites, indicating the effects of increased
solidification and calcification on the breakdown and
erosion of soil aggregates. Soil erosion was the major end
occurrence in land degradation episodes at Tsolwana game
reserve, which was a result of the integrated effects of the
vegetation and soil variables. It is recommended that land
degradation control measures should be focused on the
alteration of cause-variables rather than the effects
variable (soil erosion).
Key
words: Land degradation, land degradation index, nature
game reserve, soil erosion and vegetation. |
