Trials with four different sheep stocking rates were initiated at the Carnarvon Agricultural Experimental Plots during 1988 by the Department of Agriculture. Vegetation cover has subsequently been monitored periodically by the provincial and national Department of Agriculture. In addition, a plot-based plant diversity assessment was conducted by SAEON in May 2015.
Key findings by Van der Merwe et al. (2018):
- Stocking rate and time had significant effects on species composition
- Greater stocking rates resulted in lower total plant cover, palatable and unpalatable shrub cover, perennial grasses, and annual herbaceous species
- Higher annual rainfall resulted in higher total plant cover, while greater preceding three-month rainfall benefitted annual grasses and annual herbaceous species
- Plant diversity seemed unaffected by stocking rate as for vegetation structure.
The study confirmed the slow rate at which vegetation change occurs in drylands and therefore the importance of long-term monitoring trials.
