Assessing the Potential to Sequester Carbon within State Highway Rights-of-Way in New Mexico Phase I: Inventory of Soil Organic Carbon and Current Management Practices

Details

• Creators:
  Dunn, William C
• Corporate Creators:
  Ecosystem Management, Inc.
• Corporate Contributors:
  New Mexico. Department of Transportation. Research Bureau ; United States. Department of Transportation. Federal Highway Administration
• Subject/TRT Terms:
  Carbon Geographic Information Systems Mowing Regression Analysis Right Of Way (Land) Soils Vegetation Control
• Publication/ Report Number:
  NM10ENV-01
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States ; New Mexico
• Corporate Publisher:
  New Mexico. Department of Transportation
• Abstract:
  A study to assess carbon sequestered in soils (soil organic carbon (SOC)) within state highway rights-of-way in New Mexico was initiated in April 2011. During October–November, 2011, the authors gathered soil and vegetation samples at 117 randomly located sites in 3 biomes (19 upper montane, 54 lower montane, 44 prairie) throughout areas of the state that receive ≥35 cm precipitation. Samples were obtained along 3 transects/site and in up to 4 right-of-way (ROW) zones per transect. Physical and chemical characteristics were measured from 854 soil samples. Composition, cover, and biomass were measured for vegetation within 0.5-m² quadrats, placed centrally within each zone of each transect. Environmental characteristics of each site were captured via Geographic Information Systems (GIS). Total and mean SOC were estimated to be 153,481 Mg and 57.9 Mg/ha in the Upper Montane; 204,311 Mg and 36.2 Mg/ha in the Lower Montane; and 591,822 Mg and 42.9 Mg/ha in the Prairie biomes. Relative precision for mean SOC was 7.7% across the study area and 11–12% for individual biomes. These values were within, or close to, the 10% precision required by the Chicago Climate Exchange for trading or selling carbon credits. The authors developed regression models using untransformed variables (“standard model”) and variables grouped via factor analysis (“factor model”) to determine associations between the variables the authors measured and SOC. Annual precipitation, clay, litter, and grass in the managed and inflection ROW zones were associated with SOC in the standard model. In the factor model, Factor 1 (characterized by annual precipitation, elevation, Fraction of Absorbed Photosynthetically Active Radiation, and evaporation) and Factor 2 (characterized by grass/vegetation cover) explained 30% of the variance; seven factors explained 62% of the variance. Spatial and temporal patterns of mowing and chemical spraying were analyzed using New Mexico Department of Transportation's (NMDOT’s) Highway Maintenance Management System database to determine if adjusting these management practices might contribute to carbon sequestration. Both practices were most common in the prairie districts. The authors identified 56 highways in which reducing the number of visits to mow to the average for the district would result in 1,893 fewer miles mowed annually (3.1% of the statewide total). The authors also identified 86 highways where mowing might be limited to the dormant season. The authors found little potential for contributing to carbon sequestration by reducing the number of passes by mowers or by limiting chemical spraying. For the next phase of the study, the authors recommend testing the effects of different rates of removal of biomass and different methods to enhance growth of plants to determine which provide optimal sequestration of carbon in ROW soils. The authors also outline 3 steps in development of a ROW carbon offset protocol for marketing carbon credits.
• Format:
  PDF
• Funding:
  C05438-01
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:18abb1ae1a9f2a8de3e271e74eb21e18c21d9d6116d7956b4c922984074fa024bb6f73f2b38acdeeccd91ac4a74589c59ca778d8106291d003a0a585fff4fe8f
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/87300/dot_87300_DS1.pdf
• File Type:
  [PDF - 1.72 MB ]