Response of grasshoppers (Orthoptera: Acrididae) to livestock grazing in southeastern Arizona: Differences between seasons and subfamilies
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Authors: K. Jepson-Innes, and C. E. Bock
Date: 1989
Journal: Oecologia
Volume: 78
Number: 3
Pages: 430-431
Summary of Methods: The effect of cattle grazing on grasshopper densities was studied in Santa Cruz County, Arizona for two years. Two grazing treatments (grazed, ungrazed) were examined. Grasshopper densities were measured weekly from July to August (summer) of the first year and July to August (summer) and September to October (fall) of the second year. Percent bare ground and canopy cover of each plant species were recorded in August of the second year.
Article Summary / Main Points: Vegetative composition dictates the type of grasshoppers found on a site. Cattle grazing can decrease or increase grasshopper density depending on subfamilies present and time of year. Generally grass foragers occur at higher numbers in the summer when grasses dominates, while herbaceous foragers occur at higher numbers in the fall as grass composition is reduced due to grazing and/or senesce. During both summers, grass foragers dominated both grazed and ungrazed sites, but were more abundant on the ungrazed site where grass cover was higher. During the second year the seasonal shift from grass foragers to herbaceous forages was seen with herbaceous foragers dominating both sites. Herbaceous grasshoppers were four times more abundant on the grazed treatment. No clear connection could be made between vegetation cover and density of herbaceous foragers as cover did not vary between treatments.
Vegetation Types: Desert Grasslands
MLRA Ecoregions: 41 Southeastern Arizona Basin and Range
Agrovoc Control Words: Grazing Rangelands Grasshoppers
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: acrididae, arizona, grasshoppers, grazing
Annotation: This replicated study was conducted over two years. The specific associated results from this study are applicable to desert grasslands, though the general principles effecting community structure and habitat selection are applicable to all rangeland communities. Therefore, some grasshopper species benefit from grazing while others are negatively impacted depending on climate and intensity of grazing. As is true for all grazing research, the results are most directly applicable to areas with similar landscapes, type of ungulate, weather conditions and season of use. Joern (2004, Envrionmental Entomology 33:1617-1625) and Joern (2005, Ecology 86:861-873) studied the effect bison grazing and fire frequency has on grasshopper species richness, also available on the RSIS website; with both papers highlighting a positive correlation bison grazing has on grasshopper densities and species richness.
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