Military vehicle trafficking impacts vegetation and soil bulk density at FortBenning, Georgia

摘要

Potential increases in wind erosion that might be brought about by military vehicles travelling off-road during training are of concern to the United States military. Field studies were conducted in the summer of 2012 at Fort Benning, Georgia. The objective of the experiment was to assess the trafficked surface changes in susceptibility to generating dust emissions due to military vehicle trafficking intensity. Site-specific quantitative data on the major soil and vegetation parameters are needed tomake appropriate estimates of the susceptibility to dust generation from the soil surface and the magnitude of those emissions. The field experiment consisted of carrying out multiple trafficking passes with both tracked and wheeled vehicles. A tracked (M1A1) and wheeled (HMMWV) vehicle were driven in a figure-8 pattern in 40-m x 70-m plots. On each plot, three levels of vehicle passes were made. On the tracked plots, the M1A1 was driven a total cumulative number of passes of 1, 5, and 10. On the wheeled plots, the HMMWV was driven a total cumulative number of passes of 10, 25, and 50. The vehicles were driven repeatedly over the same figure-8 path. The statistical design consisted of vehicle type in the main plots in three replications and vehicle passes as repeated measures. 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. All grass and forb species suffered from 65% to 100% reduction in biomass. After trafficking, the biomass difference between vehicles was not significant. However, cover showed strong response to vehicle type, trafficking intensity, location (within the vehicle tracks), and their interactions. Regression equations relating trafficking intensity to reduction in cover were obtained. These equations could be used to give reasonable estimates of the loss of cover resulting from trafficking by tracked or wheeled vehicles. At the 5 cm depth bulk density was significantly higher than the control in both the M1A1 and HMMWV tracks. There was no significant evidence of soil compaction below 5 cm.