Abstract
Grazing levels and rotational schemes need to be tailored to each individual farm or pasture, and more studies are needed on the resilience of rangelands and on separating the effects of grazing and climate. The direct short-term impact of three rates of stocking (4, 8 and 16 Small Stock Units-SSU/ha) was quantified in terms of composition and cover of arid Nama Karoo vegetation (subshrub/grass). Mature Merino wethers grazed in one hectare plots during May in 1995 and 1996 (the plots were not subjected to grazing at any other time). The basal cover of the Karoo bushes (shrubs) showed a decrease at the highest stocking rate only, with the species Phymaspermum parvifolium the most sensitive to intensive grazing. An increase in stocking rate caused a significant decrease in both canopy cover and canopy-spread cover. The canopy cover of palatable Karoo bushes such as Felicia muricata, Salsola calluna and Walafrida geniculata decreased most. Light stocking (4 SSU/ha) was apparently the least detrimental to the vegetation composition and cover. Regardless of stocking rate, an 11-month resting period was possibly sufficient for all the vegetation parameters concerned to be fully restored after grazing took place. The rangeland rapidly reacted to rainfall as the ephemeral cover increased temporarily. The higher the stocking rate was, the greater the increase in ephemerals occurring. The ecological sustainability of the Nama Karoo ecosystem, utilised by high stocking densities, is questioned. Keywords: Basal cover; canopy cover; canopy-spread cover; ephemerals; Karoo bushes; stocking rate
Highlights
Concerns about the effects of agricultural management practices on the environment have initiated interest in sustainable animal production (Snyman, 1998; Broersma et al, 1999; Hoffman & Ashwell, 2001; Esler et al, 2006)
In contrast to the decrease in basal cover of the annual/poor perennial grasses (Aristida congesta, Chloris virgata, Schismus fasiculatus, Tragus koelerioides and T. racemosa), the basal cover of the bushes was least influenced by grazing
This study showed that an increase in stocking rate in the short term resulted in an almost linear decrease in canopy and canopy-spread cover
Summary
Concerns about the effects of agricultural management practices on the environment have initiated interest in sustainable animal production (Snyman, 1998; Broersma et al, 1999; Hoffman & Ashwell, 2001; Esler et al, 2006). Policy makers and the public become increasingly concerned about the sustainability of rangeland resources, soil and vegetation responses to various grazing systems (Teague & Dowhower, 2003) need to be quantified to develop suitable grazing practices (Hoffman & Ashwell, 2001; Holm et al, 2004; Esler et al, 2006; Hoshino et al, 2009). There must definitely be a threshold of vegetation change beyond which recovery does not occur (Friedel et al, 2003)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
