• Evaluating the Potential Effects of Deicing Salts on Roadside Carbon Sequestration

      Fay, Laura; Ament, Rob; Hartshorn, Tony; Powell, Scott (2019-01)
      This project sought to document patterns of road deicing salts and the effects of these salts on the amount of carbon being sequestered passively along Montana Department of Transportation roads; it was designed collaboratively with a related roadside project that tested three different highway right-of-way management techniques (mowing height, shrub planting, disturbance) to determine whether they have the capacity to increase soil organic carbon. Our sampling did not reveal elevated salt levels at any of the nine locations sampled at each of the three I-90 sites. The greatest saline concentrations were found at the sample locations farthest from the road. This pattern was consistent across all three sites. The range of soil organic matter (SOM) was broad, from ~1% to >10%. Generally, SOM values were lowest adjacent to the road and highest farthest from the road. We found no or weak evidence of a relationship between our indices of soil salinity and SOM levels, with electrical conductivity, exchangeable calcium, and cation exchange capacity. Results imply that if road deicing salts are altering patterns of roadside SOM and potential carbon sequestration, this effect was not captured by our experimental design, nor did deicing salts appear to have affected roadside vegetation during our most recent sampling effort. Our findings highlight the value of experimentally separating the multiple potentially confounding effects of winter maintenance operations on roadside soils: roads could focus the flow of water, salts, and sands to roadside soils. How these types of mass inputs to roadside soils might influence medium- or long-term carbon dynamics remains an open question, but their fuller characterization and possible flow paths will be essential to clarifying the role of roadside soils in terrestrial soil organic carbon sequestration strategies.
    • Evaluation of Effectiveness and Cost-Benefits of Woolen Roadside Reclamation Products

      Ament, Rob; Cuelho, Eli; Pokorny, Monica; Jennings, Stuart (Center for Environmentally Sustainable Transportation in Cold Climates, 2017-12)
      This research project developed three types of products for study: woolen erosion control blankets (ECBs), wool incorporated into wood fiber compost at a 40:1 ratio (compost to wool, by weight), and wool incorporated into silt fence. The project, supported by Montana Department of Transportation (MDT) and the Center for Environmentally Sustainable Transportation in Cold Climates, compared the wool products’ performance to roadside reclamation products commonly used for revegetating cut slopes: straw/coconut (coir) ECB, wood fiber compost and woven plastic silt fence. Three versions of wool silt fence were developed by the project, yet, even more versions are needed to arrive at a commercially viable product. Wool silt fence was the least promising of the three types of reclamation materials. The primary measure for success for ECBs and wool additive to the compost was the amount of seeded or desired vegetation they established after two growing seasons. The research team evaluated the performance of the woolen and standard products by measuring the percentage of canopy cover of each plant species present in each treatment plot. Canopy cover measures the percentage of ground that is covered by a vertical projection of a plant’s foliage. To conduct the comparative analysis, researchers calculated an average percent canopy cover for each functional group: seeded native grasses, desired non-seeded (volunteer) grasses and forbs, and weeds. There was no statistical difference in the mean canopy cover of seeded grass species of the compost treatment (control) compared to the cut wool with compost treatment, 6.4% and 10.2%, respectively. Thus, the project could not determine that cut wool pieces provided a benefit to plant establishment and growth when it is added to compost material. Further experimentation to determine the ideal ratio of wool pieces to add to compost is warranted. The two best performing treatments (i.e. greatest seeded grass establishment) were the rolled wool/straw ECBs. The 100% wool ECB and 50% wool/50% straw ECB had the greatest mean seeded grass canopy cover after two years. Both of these wool ECBs had more seeded grass canopy cover than the standard 70% straw/30% coir ECB demonstrating their potential as a commercially viable product for roadside revegetation applications. Laboratory tests of the wool/straw ECB demonstrated it was comparable to the specifications of a short-term (Type II B or C) standard ECB used along MDT roadways. Future product development of the wool/straw ECB should focus on improving the shear strength at high flows so it meets all required Type III specifications.