Rate of soil organic carbon sequestration in a millennium coastal soil chronosequence in northern Jiangsu, China

Abstract

The ‘4 per mille’ initiative, launched in 2015, highlighted the crucial role of soil organic carbon (SOC) sequestration in food security and climate change adaptation and mitigation. The objectives of this study were to investigate the changes in the SOC stock (SOCs) with depth and time and explore the SOC accumulation process, in a millennium chronosequence derived from marine sediments. Chronofunctions were formulated based on SOCs at different depths to evaluate the effects of sampling depth on chronofunctions and the rates of SOC sequestration. The depth distribution of SOCs showed that SOC accumulation occurred mainly in the top 40 cm, with 69% of the SOC being distributed in the upper 0–40 cm layers. The chronofunctions yielding the best fits changed from linear to power and then to logarithmic, suggesting that sampling depth affected the chronofunction type. The SOCs for the entire profile (0–100 cm) could be estimated from that in the 0–20 cm or 0–50 cm, which can potentially aid the estimation of legacy SOC data. The SOC sequestration rates were found to be high at the beginning of development, gradually slowing down with time. The soil in this area can sequestrate SOC for more than 2000 years, at a rate greater than 0.4%. Spectroscopy and digital soil mapping methods can provide accurate and acceptable SOC data pertaining to agriculture and climate change and could be a potential technology for global SOC monitoring.