Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 2, 2005
Publication Date: October 1, 2005
Citation: Branson, D.H. 2005. Effects of fire on grasshopper populations and vegetation in a northern mixed-grass prairie. Environmental Entomology. 34(5):1109-1113. Interpretive Summary: Very little is known about how grassland fires in the northern Great Plains affect the population dynamics of grasshoppers. Habitat management practices such as burning have the potential to reduce grasshopper outbreaks. This experiment examined the effect of a grassland wildfire on grasshopper populations and vegetation in western North Dakota mixed-grass prairie. Grasshopper populations were lower in sites that burned in the year following the fire. The reduction in grasshopper populations resulting from the fire was short lived, as populations in burned and unburned areas were similar two years after the fire. The effects of grassland fires in the northern Great Plains on grasshopper population dynamics will likely vary with the timing and intensity of the fire as well as precipitation. This preliminary study suggests that fire may be useful as a management tool for grasshoppers, but additional research is needed. The results can be used to help guide fire practices in the northern Great Plains.
Technical Abstract: Grassland fires have been shown to influence grasshopper community composition and population dynamics, but investigations of their effects on rangeland grasshopper population dynamics in the northern Great Plains are lacking. This experiment was designed to examine the effect of a grassland wildfire on grasshopper population dynamics and vegetation in western North Dakota mixed-grass prairie; with sampling in paired burned and unburned plots. The rapidly moving fire occurred in late October 1999, after egg-overwintering grasshoppers had laid egg pods and died. Vegetation biomass and nitrogen content of grasses was similar between burned and unburned plots. As survival of nymphal Melanoplus sanguinipes Fabricius did not differ between burned and unburned cages the year following fire, the late fall fire did not appear to change vegetative characteristics in ways that affected the short-term survival of this common species. Fire negatively affected grasshopper population densities the year following the fire, although species diversity was not affected by the fire. The wildfire led to reduced densities of Ageneotettix deorum Scudder in the year following fire, a species that lays shallow horizontal egg pods. Nymph-overwintering grasshoppers that were alive at the time of the fire were also negatively affected by the late fall fire. Grasshopper population densities did not differ between burned and unburned plots in 2001. The fire could affect grasshoppers in additional ways as population densities of both A. deorum and nymph-overwintering grasshoppers were low at all sites.