Title: Military vehicle trafficking impacts vegetation and soil bulk density at Fort Benning, Georgia Authors
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 11, 2014
Publication Date: N/A
Interpretive Summary: Potential increases in wind erosion caused by military vehicles travelling off-road during training exercises are of concern to the United States military. The U.S. Department of Agriculture-Agricultural Research Service (ARS) recently developed the Wind Erosion Prediction System (WEPS) model to estimate risk of wind erosion events on agricultural croplands. With appropriate modifications, WEPS could also be used as a decision aid in developing site-specific training schedules which minimize adverse impacts to the soil surface and vegetation cover due to off-road trafficking as well as provide reasonable estimates of possible increases in PM10 (particulate matter greater than 10 microns) content in the dust plume arising from such activities. However, availability of suitable data for use with WEPS and similar models is limited at most military installations. To fill this knowledge gap a project was initiated to conduct field experiments at military bases in different geographical and climatic regions of the country. Soil, vegetation, and surface condition data before and after vehicular trafficking were obtained in field experiments conducted in July 2012 at Fort Benning, Georgia. Among the data collected were bulk density, biomass, and vegetative cover before and after different trafficking intensities created by different vehicle (wheeled vs. tracked) types. Vegetative cover showed a 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 developed. These equations can be used to give reasonable estimates of the loss of vegetative cover resulting from trafficking by tracked or wheeled vehicles. The near surface layer bulk density (0-5 cm depth) was significantly higher after trafficking with both the M1A1 Abrams tank and HMMWV (Humvee). The results from this experiment can be included in WEPS and similar models so they can better assess dust emissions and wind erosion potential resulting from military training activities at Fort Benning.
Technical Abstract: 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 to make 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 × 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.