Vehicle Impacts on Northern Great Plains Range Vegetation

Abstract

Three levels of vehicle impact (2,8,32 trips over the same tracks) were applied on rangelands near Ashland, Mont., using a fourwheel-drive Chevrolet Blazer with mud and snow radial tires. The impacts were applied each month, May to September, on previously unhnpacted range. Canopy coverage measurements and ground and aerial photography were used to evaluate ihe impact effects. In the year of impact, canopy coverage measurements showed increasing damage to the vegetation as the number oftrips increased. Damage was greater on very moist to wet soils than on dry soils. Vegetation measurements the year following the impacts did not show carry-over damage to vegetation from the 2 and 8 trip treatments, except for range hnpacted when the soils were wet. These measurements did show carry-over damage to shrubs from 32 trips, but not to grasses and forbs. Ground and aerial photographs in the fit year after the impacts still showed visual evidence of 8 and 32 trip impacts. Aerial photographs taken the second year after the impacts still showed evidence of all 32 trip treatments and some 8 trip treatments. Color infrared film gave superior results when the vegetation was actively growing. Color film was superior when the vegetation had dried. Off-road vehicle (ORV) travel has become a major concern of federal and state land management agencies and many ranchers. Limited research on vegetational impact from ORV’s has been done in the deserts of the Southwest and along both eastern and western coastlines, but none has been done in the Northern Great Plains. A great deal of work has been done on the effects of agricultural and military vehicles on soils, but comparatively little literature is available on ORV-rangeland relationships. The military has done exhaustive studies using aerial photography to assess vehicle impacts on vegetation. Unfortunately, only part of this work is available to the research scientist. Still, there is a wealth of other information available dealing with the photography of vegetation. (See footnote). Our primary objectives were to (1) determine the effects of vehicle impacts on soil and vegetation and (2) evaluate photography as a means of identifying vehicle impact.