SPATIAL-ANALYSIS OF GRASSHOPPER DENSITY AND ECOLOGICAL DISTURBANCE ON SOUTHERN IDAHO RANGELAND

Historical grasshopper survey data were used to relate grasshopper densities to ecological condition classes on the Bureau of Land Management's Shoshone District in Idaho as part of an effort to identify areas prone to high grasshopper densities and to understand the effects of range management practices on grasshopper populations. A MOSS-based Geographic Information System was used to overlay maps of ecological condition, elevation, and grasshopper density to test the hypothesis that grasshopper density was the same for all ecological condition classes. Areas that had been severely disturbed by wildfires and invasion of exotic annual vegetation had significantly higher grasshopper densities over the 3 years examined than less severely disturbed areas that retained some sagebrush cover. This suggests that shrub loss due to wildfires or other causes may lead to greater grasshopper densities. The techniques and applicability of geostatistical spatial analysis to these questions is also discussed.