Military Vehicle Trafficking Impacts on Vegetation and Soil Bulk Density at Fort Benning , Georgia

Potential increases in wind erosion that might be brought about by military vehicles traveling off-road during training are of concern to the U.S. military because wind erosion and vehicle dust emissions contribute to land and air quality degradation and can cause adverse effects on respiratory health. Field studies were conducted in the summer of 2012 at Fort Benning, Georgia, to assess the effects of military vehicle trafficking intensity on susceptibility to dust emissions. Quantitative data on soil and vegetation parameters are needed to make appropriate estimates of the susceptibility to dust generation from the soil surface and the magnitude of those emissions. The experiment consisted of making multiple trafficking passes with both tracked and wheeled vehicles and then measuring wind erosion parameters. A tracked (M1A1) and wheeled (HMMWV) vehicle were driven in a figure-8 pattern within replicated 40 m × 80 m plots. On each plot, three levels of vehicle passes were made. On the tracked plots, the M1A1 was driven a cumulative total of 1, 5, and 10 passes. On the wheeled plots, the HMMWV was driven a cumulative total of 10, 25, and 50 passes. The vehicles were driven repeatedly over the same figure-8 path. Bulk density, aboveground biomass, and vegetative cover data were taken from the straight, curved, and cross-over sections of the vehicle tracks. Samples were also taken before the start of trafficking. Bulk density at three depths, total aboveground biomass, grass biomass, forb biomass, biomass by individual species, total cover, grass cover, and forb cover data were analyzed for differences between vehicles, vehicles passes, locations within the track sections, and their interactions. At the 5 cm depth, bulk density was significantly higher (p ≤ 0.05) than the control in both the M1A1 and HMMWV tracks. There was no significant evidence of soil compaction below 5 cm. At the end of all trafficking, grass and forb species biomass was reduced 65% to 100%. Vegetation cover showed strong response to vehicle type, trafficking intensity, location (within the vehicle tracks), and their interactions. Regression equations relating trafficking intensity by vehicle to reduction in cover and biomass were obtained.