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 four-wheel-drive Chevrolet Blazer with mud and snow radial tires. The impacts were applied each month, May to September, on previously unimpacted range. Canopy coverage measurements and ground and aerial photography were used to evaluate the impact effects. In the year of impact, canopy coverage measurements showed increasing damage to the vegetation as the number of trips 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 impacted 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 first 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.