Straw tissue quality influence the formation pathways of soil organic carbon via living microbes or microbial necromass in a Mollisols,Northeast ChinaOA

Soil organic carbon(SOC),representing the largest terrestrial organic carbon pool,significantly influences soil quality.The incorporation of residues is widely recognized as a method to regulate SOC sequestration.A 365-day incubation experiment was conducted to evaluate the contribution of straw-derived carbon(SDC)of varying quality to SOC fractions(free-floating particulate organic carbon(f POC),occluded POC(o POC)and mineral-associated OC(MAOC)),and examine the relationships between microorganisms and SOC fractions by incorporating^(13)C-labelled maize stem straw(ST),leave straw(LE),sheath straw(SH)(1%)in Chinese Mollisols.Results indicated that compared to control(CK),ST,LE and SH treatments enhanced SOC,f POC and MAOC by 4.8-19.5,35.7-49.5 and 1.6-3.9%,respectively.The SDC-SOC and MAOC content of LE were 29.1-38.1%and 17.5-44.5%higher than ST and SH,respectively.The SDCo POC content of SH was 3.1%higher than LE.The PLFA concentration decreased steadily throughout the incubation period,while necromass remained in-fluctuating until an obvious increasing trend observed at later stage.Furthermore,structural equation model(SEM)revealed that lignin to nitrogen ratio(Lig N)of ST exhibited negative association with SDCf POC,and bacterial diversity in SH showed negative correlation with Lig N and positive correlation with SDC-o POC,while demonstrating positive correlation between microbial necromass and SDC-MAOC in LE.These findings indicated that POC dynamics correlated with straw chemical traits,while MAOC showed links to both microbial necromass traits and straw chemical characteristics.These findings advance our understanding of how straw residue quality influences SOC turnover and stabilization through microbial community interactions,contributing to the development of policies to improve soil fertility,and promote the rational and efficient utilization of straw.