Abstract: The sequestration of soil inorganic carbon (SIC) especially pedogenic carbonate (PC) is one of the important pathways reducing the concentration of atmospheric carbon dioxide and thus mitigating climate change in coastal areas. Using the technology of ¹³C stable isotope, we analyzed the differences in the composition and storage of SIC, and explored the key physicochemical properties influencing soil PC storage in different horizons (0-10, 11-20, 21-40, 41-60, 61-80 and 81-100 cm) from Suaeda salsa wetland (SS), Spartina alterniflora wetland (SA), young poplar plantation (YP), and mature poplar plantation (MP) in coastal area of the northern Jiangsu Province. The results showed that except for the surface (0-10 cm) soil in MP, the SIC content was higher than SOC in all soil horizons. Overall, neither the soil PC to SIC ratio nor the SIC storage were significantly different in SA and SS soils. Compared to wetland soils (0-40 cm), the soil PC to SIC ratio was reduced by 32.7% and 54.1% and the PC storage was reduced by 40.5% and 59.2%, the lithogenic carbonate (LC) storage changed little, while the SIC storage was reduced by 21.0% and 17.9%, respectively in the YP and MP soils. Compared to the YP soils (0-100 cm), both the soil PC to SIC ratio and the PC storage were significantly reduced while the LC storage was significantly increased, especially at the 41-100 cm soil horizons, meanwhile, the SIC storage was not significantly changed in the MP soils. Results of the structural equation modeling (SEM) indicated that key factors influencing soil PC storage were the ratio of PC to SIC, followed by the SOC content and bulk density. SOC could inhibit the formation of soil PC. Generally, the coastal wetlands have greater SIC storage and sequestration potential than poplar plantations, and the PC sequestration can be regulated by modulating the ratio of PC to SIC and SOC content.

Key words: inorganic carbon, pedogenic carbonate, lithogenic carbonate, carbon storage, plantation, coastal wetland