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Human activities, from resource extraction to recreation, are increasing global connectivity, especially to less-disturbed and previously inaccessible places. Such activities necessitate road networks and vehicles. Vehicles can transport reproductive plant propagules long distances, thereby increasing the risk of invasive plant species transport and dispersal. Subsequent invasions by less desirable species have significant implications for the future of threatened species and habitats. The goal of this study was to understand vehicle seed accrual by different vehicle types and under different driving conditions, and to evaluate different mitigation strategies. Using studies and experiments at four sites in the western USA we addressed three questions: How many seeds and species accumulate and are transported on vehicles? Does this differ with vehicle type, driving surface, surface conditions, and season? What is our ability to mitigate seed dispersal risk by cleaning vehicles? Our results demonstrated that vehicles accrue plant propagules, and driving surface, surface conditions, and season affect the rate of accrual: on- and off-trail summer seed accrual on all-terrain vehicles was 13 and 3508 seeds km, respectively, and was higher in the fall than in the summer. Early season seed accrual on 4-wheel drive vehicles averaged 7 and 36 seeds km on paved and unpaved roads respectively, under dry conditions. Furthermore, seed accrual on unpaved roads differed by vehicle type, with tracked vehicles accruing more than small and large 4-wheel drives; and small 4-wheel drives more than large. Rates were dramatically increased under wet surface conditions. Vehicles indiscriminately accrue a wide diversity of seeds (different life histories, forms and seed lengths); total richness, richness of annuals, biennials, forbs and shrubs, and seed length didn't differ among vehicle types, or additional seed bank samples. Our evaluation of portable vehicle wash units showed that approximately 80% of soil and seed was removed from dirty vehicles. This suggests that interception programs to reduce vehicular seed transportation risk are feasible and should be developed for areas of high conservation value, or where the spread of invasive species is of special concern.

Although the gopher tortoise (Gopherus polyphemus) is widespread across the southeastern United States where conditions are favorable, the species is in serious decline. While biologists and land managers might consider any of a variety of in-situ and ex-situ management options when determining how best to manage individual populations, there are no good decision tools for evaluating or predicting whether the existing population is viable in the long term. This study developed demographic models for gopher tortoise populations and has proposed to use those models to predict outcomes for a variety of population conditions and management scenarios. The major limiting factor in the development of models was the availability of complete lifehistory data. Because of its demonstrated importance in population stability in other turtle species, adult survivorship was assumed to be high in all model scenarios. However, reproduction and survivorship of other life stages varied among simulations. The model results demonstrated that, of the parameters manipulated, hatchling survivorship was the most critical life history stage because of the very small likelihood that hatchlings survive to their second year. Any management actions that increase hatchling success are likely to increase population viability significantly.

We examined habitat disturbance, species richness, equitability, and abundance of ants in the Fall-Line Sandhills, at Fort Benning, Georgia. We collected ants with pitfall traps, sweep nets, and by searching tree trunks. Disturbed areas were used for military training; tracked and wheeled vehicles damaged vegetation and soils. Highly disturbed sites had fewer trees, diminished ground cover, warmer soils in the summer, and more compacted soils with a shallower A-horizon. We collected 48 species of ants, in 23 genera (141,468 individuals), over four years of sampling. Highly disturbed areas had fewer species, and greater numbers of ants than did moderately or lightly disturbed areas. The ant communities in disturbed areas were also less equitable, and were dominated by Dorymyrmex smithi.

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