Disturbance by fire frequency and bison grazing modulate grasshopper assemblages in tallgrass prairie
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Authors: A. Joern
Date: 2005
Journal: Ecology
Volume: 86
Number: 4
Pages: 861-873
Summary of Methods: The combined effects of burn frequency (1, 2, 4, 20 and unburned), bison grazing activity (grazed and ungrazed) and topography (upland and lowland) on the local diversity of grasshoppers were examined in Kansas (39° 05’ N, 96° 35’ W). Grasshopper species richness and relative abundance was determined from sweep net sampling in early August. Canopy height, plant species richness and biomass of grasses and forbs were measured the same time.
Article Summary / Main Points: Grasshopper species richness increased with bison grazing. There were no differences in grasshopper species richness between upland vs. lowland sites and 1-4 year burn frequencies on ungrazed sites. Heterogeneity in vegetative canopy cover, as a result of bison grazing, was the strongest predictor of grasshopper species richness and density. As canopy cover heterogeneity increased so did the number of grasshopper species present. Overall, as grasshopper densities increased so did grasshopper species richness.
Vegetation Types: Tallgrass Prairie
MLRA Ecoregions: 106 Nebraska and Kansas Loess-Drift Hills
Agrovoc Control Words: Grasshoppers Grazing Burning
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: acrididae, disturbance, habitat heterogeneity, konza prairie, long term study, phasmida, prescribed burning, tettigoniidae
Annotation: This was a replicated study over one year and the specific results apply to only tall grass prairies, though the general principles effecting community structure and habitat selection are applicable to all rangeland communities. As is true for all grazing research, the results are most directly applicable to areas with similar landscapes, type of ungulates and grasshoppers, weather conditions and season of use. Grazing studies on grasshopper densities suggest that the impact of livestock grazing on grasshoppers depends upon the season, the species, and the plant community. Therefore, some grasshopper species benefit from grazing while others are negatively impacted depending on climate and intensity of grazing. Jepson-Innes and Bock (1989, Oecologia 78:430-431) showed that cattle grazing can have a positive or negative impact on grasshoppers, depending on the species and the type of forage relevant to that species. Joern (2004, Environ. Entomology 33:1617-1625) studied the effect bison grazing and fire frequency has on grasshopper densities, also available on the RSIS website; with both Joern papers highlighting a positive correlation bison grazing has on grasshopper densities and species richness.
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