**4. Conclusion**

intensification of degradation can induce shifts in the distribution of texture, as indicated in the study by Dong et al. [27] in the Qinghai-Tibetan Plateau in China, which found that grassland degradation led to a shift in soil texture from loamy toward sandy loamy soils. This phenomenon was corroborated by Fullen et al. [40], whose study compared the textures of grassland and degraded sandy soils from Shropshire, UK, and concluded that degradation changed mean soil texture from a very slightly stony loamy sand to a slightly stony sandy loam. The authors also found that the degraded soil was particularly deficient in sand, especially medium and coarse sands, and the depletion in sand was so marked that the degraded bare soil had significantly greater mean percentage clay content than non-degraded grassland soil. A recent meta-analysis by Dlamini et al. [41] concluded that grassland degradation has a significantly negative effect on coarser textured soils than fine textured soils due to the lack of physical protection of organic matter and weak aggregation in sandy soils.

88 Land Degradation and Desertification - a Global Crisis

**Figure 4.** Relationship between sand, silt, clay and soil surface coverage by vegetation. Data are presented as mean±SE (*n*=12) per soil surface coverage by vegetation, and bars with different letters are significantly different at the *P*<0.05

Land degradation results in the reduction of vegetation cover, which is unfavourable to soil protection. Degraded soils generated through the loss of vegetation cover are exposed to raindrop impact, which may lead to crust formation and a reduction in the infiltration capacity of the soil [42]. Such effects may lead to bare soil being more susceptible to surface runoff generation as drainage becomes impeded. These changes to soil hydrology have implications for runoff from degraded land, potentially modifying not only the quantity but also the quality of runoff, in terms of sediment and nutrient loads transported over and through the soil [37]. Vegetation cover by intercepting raindrops and enhancing infiltration protects the soil surface from the erosional effects of rainsplash and surface runoff, and this in turn helps preserve the

level.

water quality in surface waters of rangelands.

The reduction in grass cover induced by degradation in the communal rangeland resulted in a decrease in soil aggregate stability. The reduced soil structure or aggregation was concomitant with an increase in soil compaction and bulk density as well as a shift in soil texture associated with decreasing sand content and increasing clay content in the soil surface layers. Soil structure and texture are soil quality parameters crucial to the provision of ecosystem services and desirable for functioning of rangelands. Land degradation by adversely altering the quality of these soil properties negatively affects the services they provide, such as storing water, carbon and nutrients, which affect grassland productivity when lost. For many smallholder farmers, the grass vegetation of communal rangelands is essential to livestock production by providing forage for grazing animals, meat, dairy products and income to the people. As such, quantitative data on the effects of degradation on the quality of rangeland soils and the processes involved are crucial for developing effective land management and rehabilitation options, with the goal of improving rangeland productivity. Soil quality in degraded rangelands can be enhanced by adopting focused initiatives, such as the UN Convention to Combat Desertification. Improvement of rangelands can involve various grassland management options — from fertilization, soil tillage, livestock exclusion, burning and appropriate grazing regimes, which can lead to more sustainable rangelands. More work of this nature needs to be carried out on different soil types under diverse rangeland environments.
