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Evaluating Management Options to Increase Roadside Carbon Sequestration

Project #: 4W5840
Start Date: 10/01/2015
End Date: 12/31/2017

As described in the final report, the research team estimated the amount of carbon sequestered along Montana Department of Transportation (MDT) roads and tested 3 different highway right-of-way (ROW) management techniques to increase carbon stocks. Using Geographic Information System techniques, the total ROW acreage owned by MDT was found to sequester 75,292 metric tons of carbon per year and to consist mostly of grasslands (70%). From 2016-2018, the team tested 3 ROW management techniques to increase carbon stocks- increase mowing height, plant woody shrubs, or add legumes to reclamation seed mixes of disturbed soils – at 3 sites (Three Forks [3F], Bear Canyon [BC], and Bozeman Pass [BP]) along Interstate 90 in southwestern Montana. Soil samples generally averaged 0.75–1.5% soil organic carbon (SOC) at the 3F site, 2.5–4% SOC at the BC site, and 1.5–2.5% SOC at the BP site. Average SOC levels were always lower in 2018 than in 2016. Soil respiration rates were generally highest in June or July at the BC site, averaging ~4 μmol CO2 m-2 second-1. Soil respiration rates were lower at the BC site in November 2016, at the BP site in June 2018, and at the 3F site in July 2018 (all ~2–3 μmol CO2 m-2 s-1). Aboveground biomass carbon estimates generally mirrored belowground SOC estimates. Taken together, the findings suggest that of the three treatments implemented (raised mowing height, shrub planting, and disturbance), minimizing disturbance to soils likely makes the greatest contribution to the medium- and long-term carbon-storage potential of these roadside soils.


Interest has recently been increasing in the potential for roadside vegetation and soils to capture and store carbon through the absorption of CO2 by vegetation and soil (terrestrial sequestration).

This project will estimate how much roadside acreage exists and how much carbon is currently being captured and stored along Montana DOT’s (MDT’s) roadsides. Next, researchers will calculate how much of this acreage is available for active carbon management,  then construct experimental plots to determine if changing three different management practices of roadside vegetation and soils can increase existing levels of carbon capture and storage.  The three management practices are: increasing the mowing height within the ROW clear zone, increasing physiognomic diversity by planting native woody shrubs into existing perennial-grass-dominated ROWs, and including  leguminous forbs with seed mixes for roadside re-vegetation projects.

The team will be able to compare two of these management techniques that are also being tested in New Mexico. This will allow the FHWA and DOTs to evaluate some of the differences in roadside carbon storage potential in more mesic and colder climates with those of the arid southwest United States.


The objective of this project was to work with the Montana Department of Transportation (MDT) to estimate how much roadside acreage exists and how much carbon is currently being captured and stored along roadsides managed by MDT.

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