Positive effects of burning and cattle grazing on grasshopper diversity
2016
Joubert, Lize | Pryke, James S. | Samways, Michael J.
Grasshoppers constitute a significant proportion of invertebrate diversity in grasslands, but little is known about how fire and grazing, two of the main drivers of grassland dynamics, influence them. Here, we determine how these disturbances influence grasshopper diversity in remnant grassland ecological networks (ENs) among commercial forestry compartments in Afromontane grassland, South Africa. Sites differed in fire frequency (annual vs. longer rotation burning), time since last fire (<12 months vs. >12 months ago), and presence or absence of domestic cattle grazing. Reference sites were in an adjacent protected area (PA). We also recorded bare ground, vegetation cover, and vegetation height. Grasshopper abundance significantly benefitted from annual burning, cattle grazing, short grass, and when the last fire was <12 months prior to sampling. Fire frequency was the only disturbance with a significant effect on grasshopper species composition, but without significantly affecting species richness. In the PA, heterogeneity of dispersion was smaller in annually burned firebreaks than in sites with longer fire‐return intervals, which points to homogenisation of resident grasshopper assemblages. Although most grasshopper species favoured recently burned or grazed grassland, some preferred low or no disturbance. This illustrates a considerable range of habitat preferences in the grasshopper assemblage. Management recommendation: Burning and grazing at moderate levels should be integral to local landscape management, as these impacts benefit grasshoppers in grassland ENs. Some areas should be left undisturbed to create a mosaic of different successional stages at the landscape spatial scale, providing diverse habitat for a wide range of species.
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