Legacy Effects of Highway Construction Disturbance and Vegetation Management on Carbon Dynamics in Forested Urban Verges

Abstract

Natural ecosystems, like forests, adjacent to urban interstates are directly exposed to vehicle emissions (e.g., carbon dioxide) and may be strategically located for providing ecosystem services, such as carbon storage and sequestration. The primary goal of this study was to determine the effects of past soil disturbance (i.e., topsoil removal during highway construction) and an exotic shrub (Amur honeysuckle) on soil carbon dynamics in forests adjacent to urban interstates in Louisville, Kentucky. To predict potential tree and soil carbon storage and sequestration, CENTURY model simulations were conducted. A short-term (94-year) CENTURY model simulation was performed to determine the impact of past soil disturbance and honeysuckle presence on tree and soil carbon dynamics. The forest with highly disturbed soils exhibited 20% lower tree and 3% lower soil carbon storage than the forest with undisturbed soils. Tree carbon storage was 1.6 times more and soil carbon storage 1.2 times more in the forest with low honeysuckle density compared to the forest dominated by honeysuckle. Since honeysuckle removal is a management option for improving biodiversity in these interstate forests, the implication of honeysuckle eradication on long-term carbon storage in these ecosystems using 494-year CENTURY model runs was explored. Once the impact of honeysuckle was removed from the CENTURY simulations, the forest dominated by honeysuckle with intensively disturbed soils exhibited similar tree carbon storage (70,133 g Cm⁻²) and greater soil carbon storage (7,380 g Cm⁻²) than the forest with low honeysuckle density and undisturbed soils (tree = 71,152 g Cm⁻², soil = 7,053 g Cm⁻²). These CENTURY model simulations suggest that over long time spans the removal of Amur honeysuckle could improve tree and soil carbon sequestration even where urban soils experienced intense past soil disturbance.