Assessment technique for evaluating military vehicular impacts to vegetation in the Mojave desert

Abstract A new plant-damage assessment technique was developed. The technique consists of linear transects the width of a military vehicle’s tracks located in existing tracks in the soil (usually during a prior training rotation period of 30 days or since the last rain or wind storm). Measurements of vegetation within the tracks are used to determine the area of plant parts impacted. The percent of the plant parts damaged and the percent expected to recover are estimated. The technique documents prior-damage classes based on estimates of damage that plants have apparently experienced previously (as assessed from field indicators of damage such as plant shape and height). The technique was used to evaluate different vehicle types (rubber-tire wheels vs. metal tracks) in six areas at the NTC with different soils and training intensity levels. The technique provides tabular data that can be sorted and queried to show a variety of trends related to military vehicular impacts. It also is suitable for assessing other non-military off-road traffic impacts. The study reports: (1) differences in plant sensitivity to different vehicle track types, (2) plant cover and density by species and training area after prolonged impact, (3) the degree to which rubber tire wheels have less impact than metal tracks, and (4) mean percent survival was inversely proportional to the degree of prior damage received by the vegetation (i.e., plants previously impacted have lower survival than plants not previously impacted).