Cumulative impacts on Alaskan arctic tundra of a quarter century of road dust1

Tundra ecosystems are sensitive to disturbance and slow to recover. To account for environmental costs of development in the North, cumulative impacts of roads and dust deposition must be quantified. After a previous study, we re-examined tundra adjacent to the 577-km-long Dalton Highway in northern Alaska to assess 13 y of additional calcareous road dust deposition. Dust loading continues to alter substrate properties and community composition. Moist, acidic, tussock-sedge tundra typically has a soil pH of 4. At the road margin the pH of the fibric horizon had increased to pH 5.5 by 1989 and to pH 6.0 by 2002. Plots adjacent to the road have significantly higher graminoid and Rubus chamaemorus biomass and less moss, evergreen shrub, lichen, and forb biomass. Graminoid cover ranges from 30% in undisturbed tundra to over 80% within 5 m of the road. We observed an 80 g·m- 2 increase in graminoid biomass and a 130 g·m- 2 decline in moss biomass across the study site between 1989 and 2002. Ordinations indicate a broadened zone of dust disturbance in 2002. This evidence of cumulative impacts of dust will improve our evaluation of the ecological costs of future road development in the North.