Long-term fencing alters the vertical distribution of soil δ13C and SOC turnover rate: Revealed by MBC-δ13C

• Published in: Agriculture, ecosystems & environment Vol. 339; p. 108119
• Main Authors: Qu, Qing, Zhang, Juan, Hai, Xuying, Wu, Jianzhao, Fan, Jiawei, Wang, Defu, Li, Jiwei, Shangguan, Zhouping, Deng, Lei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2022
• Subjects: agriculture; biomass; Carbon cycle; carbon dioxide; carbon sinks; China; Degeneration; environment; fractionation; Grassland management; grasslands; Land use change; microbial carbon; Soil microorganism; soil organic carbon; soil profiles; Soil δ13C; spatial distribution; China; Carbon cycle; Soil δ13C; Degeneration; Grassland management; Soil microorganism; Land use change
• ISSN: 0167-8809; 1873-2305
• DOI: 10.1016/j.agee.2022.108119

Grassland is the significant composition of the terrestrial carbon pool. Its belowground carbon turnover process is sensitive to land use changes and has a huge impact on atmospheric CO2 contents. However, the interpretation of the vertical distribution of δ13C values of soil organic carbon (SOC-δ13C), the SOC turnover rate (β value) and their changes in the soil profile remain uncertain after fencing (grazing exclusion). Grasslands that have been fenced for 39 years and grazed (as the control) on the Loess Plateau, China were selected to evaluate the vertical distribution of SOC-δ13C and β values and their influencing factors across the 0–100 cm soil profile (0–10, 10–20, 20–40, 40–60, 60–80, 80–100 cm). The results showed that SOC gradually decreased but SOC-δ13C overall increased with soil depths. Fencing significantly decreased the SOC-δ13C in 10–80 cm depth. The SOC-δ13C had a positive correlation with δ13C values of microbial biomass carbon (MBC-δ13C), but negative correlations with root biomass. Besides, the β values of 0–60 cm depth were higher in fencing grasslands (−2.70) than that in grazing grasslands (−11.38). Overall, carbon input, microbial fractionation and soil leaching contributed to the increasing trend of SOC-δ13C with soil depths, and fencing increased the SOC content in the profile but decreased the SOC turnover rate in 0–60 cm soils. The results provide direct evidence for the change of SOC-δ13C and a more comprehensive understanding of SOC-δ13C and SOC turnover dynamics with long-term fencing across the soil profile. The information on SOC dynamics and their feedback to long-term fencing can aid in developing reasonable grassland management measures. •SOC gradually decreased but SOC-δ13C overall increased with soil depths.•Grazing exclusion increased soil C contents but decreased the C turnover rate.•SOC-δ13C was positively correlated with δ13C values of microbial biomass carbon.•SOC-δ13C in grazing grasslands was affected by pH, cPOC, C/N and enzyme activity.•SOC-δ13C in fencing grasslands was affected by C/N.