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.

Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2007.

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.