Assessing the Physical Stability of Soil Organic Carbon in Roadside Ecosystems

Understanding the factors controlling the stability of soil organic carbon stocks, notably in urban areas such as roadsides, can contribute to a better quantification of the ecosystem services that these areas can provide, a key to improving urban planning and management. This study assessed soil carbon stability based on physical fractions in roadside ecosystems of southern Quebec, Canada. We measured the carbon content of soil mineral-associated (MAOC) and particulate (POC) organic carbon physical fractions of roadsides with different land uses and investigated relationships with road density, soil concentration of heavy metals, and soil salinity. We used the MAOC/POC ratio to evaluate the carbon storage potential of each physical fraction. The stable physical fraction MAOC contained a higher carbon content than the labile soil fraction POC across different depths. The MAOC/POC ratio was higher for sites with a more recent history of agriculture abandonment. MAOC was positively linked to road density, soil salinity, and heavy metal concentration. This study suggested that roadside soils have a high capacity to store carbon in a stable form. Additionally, the chemical properties of roadside soils did not adversely affect the physical stability of soil carbon, especially in the top mineral soil.