Background Slope restoration ecosystem can not only reduce soil erosion, but also absorb carbon dioxide in the atmosphere, increase the carbon sink function, so as to offset the carbon emission during the highway construction period. With the vegetation succession, the carbon sequestration rate of the slope will change significantly, but the characteristics of the change are still unclear. And the offsetting effect of slope carbon sequestration on carbon emissions during highway construction period has not been quantified yet, leading to insufficient understanding of the carbon sequestration value of slopes and limiting the proposal of relevant carbon sequestration strategies.

Methods In order to quantify the carbon sequestration potential of highway slope restoration ecosystems, this study takes the CCCC Guanglian Expressway as the research object, established a calculation model of slope carbon sequestration based on vegetation succession process, calculated the carbon sequestration of ecological slopes along the highway, and its carbon sequestration function offsets the carbon emission of the highway roadbed and the pavement project during the construction period and analyzed the carbon sequestration potential of the ecosystems of highway slope restoration accordingly.

Results The results of the study show that: 1) During the restoration process of highway slopes, the carbon sequestration of vegetation shows a trend of first increasing and then stabilizing over time, while the carbon sequestration of soil shows a trend of first decreasing and then increasing, and the contribution of vegetation carbon pool to slope carbon sequestration exceeds 64%. 2) The carbon sequestration rate of highway slopes is the highest in the first 20 years of restoration, about 0.60–0.69 kg/(m²·a) carbon (C), which is comparable to natural ecosystems such as mangroves. 3) During the period of 2023 – 2050, the ecological slopes along the Guanglian Highway show a remarkable carbon sequestration potential, the carbon sequestration increased from 4.53 × 10³ t CO₂ to 31.86 × 10³–34.66 × 10³ t CO₂, and the ratio of the amount of carbon sequestration to the carbon emissions during the construction period of the highway roadbed and roadway engineering. increased from 2.59% to 18.25%−19.85%.

Conclusion Slope restoration ecosystems have strong carbon sequestration potential, so the carbon sequestration capacity of vegetation species should be fully considered when restoring slope ecosystems. The first 20 years of slope ecological restoration are a critical period for carbon sequestration, and the maintenance and management of slope vegetation should be strengthened during this stage. The results of this study not only provide reference for the evaluation of slope carbon sink resources, but also provide scientific basis for the improvement of artificial slope carbon sink function restoration technology.