Responses of grasshopper assemblages to long-term grazing management in a semi-arid African savanna

Abstract

A study on grasshopper assemblage response to seasonal grazing, rotational grazing, continuous resting and continuous grazing was undertaken in the eastern Karoo, South Africa. Rotationally-grazed sites supported the highest number and abundance of grasshopper species while continuously-grazed sites had the lowest. Spring-grazed and winter-grazed sites were the most similar, with continuously-rested sites being the next similar to these. Rotationally-grazed sites showed the least similarity to the other sites. There were clear groupings of sites and grasshopper species, with most species associated with rotationally-grazed sites. Continuously-grazed sites had a different grasshopper assemblage. The assemblages followed definite gradients of measured environmental variables. Rotationally-grazed sites occurred along gradients of increasing bare ground, while continuously-grazed and summer-grazed sites occurred along increasing gradients of shrub cover and soil temperature. Spring-grazed, autumn-grazed, winter-grazed and rotationally-grazed sites were characterized by high vegetation density. Grasshopper dominance differed between sites. Summer-grazed sites had high dominance of Pycnodictya flavipes (40%), winter-grazed sites of Pseudogmothela sp. (32%) The significance of variable grazing management systems for maintaining floral and grasshopper diversity is discussed. Rotational grazing in this arid system is most suited to maintaining plant and insect diversity.