Soil organic carbon stability of vegetation restoration during 11-year-old grassland succession

Purpose: Soil aggregates are the basic unit of soil structure and have a significant impact on soil organic carbon (SOC) sequestration. Most of the current research focuses on the effect of vegetation restoration on soil organic carbon storage, while the response of soil organic carbon stability and influencing factors under different vegetation restoration modes is still unclear. Methods: This study uses stable carbon isotopes and Fourier transform infrared spectroscopy to characterize soil organic carbon compounds, and elucidate the effects of natural shrub (NS), natural grassland (NG), olive grove (OG), and cropland (CL) restoration on soil organic carbon stability. Results: The results showed that the proportion of macroaggregates in the topsoil of cropland was about 1.5 times that of other vegetation types during the same restoration period. However, the content of organic carbon in the macroaggregates is not the most, indicating that the macroaggregates are not conducive to maintain the stability of organic carbon. The content of stable organic carbon in natural grassland soil was the highest, and the accumulation of soil organic carbon was the highest. Conclusions: We considered natural grassland soil has the greatest carbon sequestration potential. The content of unstable polysaccharides in olive groves was the highest about 75%, which made organic carbon easily decomposed, resulting in the least accumulation of olive groves. The findings are directly relevant to regional policies to promote vegetation restoration, and natural revegetation can help restore ecosystem function in vulnerable areas.