| Summary: | Concerns were raised over the past decades, on the degradation condition of arid and
semi-arid rangelands in South Africa, mainly in areas under communal land
management. Baseline information on soil quality is essential to monitor changes in land
conditions and assess impacts of land uses and management over time. The objectives of
this study, initiated within the framework of the Desert Margins Program, were to
characterize and establish baseline indicators of soil quality health, and to investigate
the potential effects of grazing and exclusion management (hypothesized as grazing
effect) on selected soil properties in the western Bophirima District in South Africa.
Soils were characterized for physical, chemical, enzymatic activity and microbial
biomass properties, and grazing effects were evaluated on selected properties. The
aboveground herbaceous species composition and biomass production were also
determined. Sandy, poor fertile soils (low organic carbon and phosphorus)
characterized all sites. Various levels of enzymatic and microbial biomass were
recorded at the sites. Grazing had no significant effects on most of soil chemical
properties, but did affect selected enzymatic activities, site-specifically. No significant
differences of grazing effects were observed on soil microbial biomass. The
inconsistent responses of soil properties across the sites prompt to caution regarding
the generalization and/or extrapolation of grazing effects to other areas, without
consideration of the prevailing environmental and management characteristics to each
site. Notwithstanding the alarming plea about degradation at these communal sites,
indicators of soil quality did not significantly differ between communal and
surrounding commercial and/or game managed areas, despite their apparent vegetation
degradation. The results showed that rangeland under the communal management
were characterized by increaser species of low grazing value, but this situation did not
necessarily interpret severe soil degradation as tacitly described. Soil degradation
depends on land use, management and environmental conditions, and references are
needed to assess degradation. Important interrelationships between the aboveground
vegetation and soil belowground activity were observed. This emphasized the need to
integrate both soil and vegetation into rangeland monitoring, as these interrelationships
and associated ecological processes sustain rangeland health. Further research is needed to re-examine the "inferred degradation of rangelands in communal areas,
taking into consideration their history, and using appropriate baselines and references
sites. Only then, can degradation trends and hotspots be identified and thereof,
appropriate management decisions (through participatory research) taken locally to
combat degradation and sustain long-term rangeland resources uses. === Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2007.
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