Conversion of organic carbon from decayed native and invasive plant litter in Jiuduansha wetland and its implications for SOC formation and sequestration

Abstract

It is still controversial which type of plant litter is conducive to soil organic carbon (SOC) formation. Here we are to explore the conversion of organic carbon (OC) from decayed plant litter in soil and its influence on final SOC sequestration. In situ investigation combined with laboratory soil incubation experiments were conducted in mixing zones dominated by halophytes of Phragmites communis and Spartina alterniflora in the Jiuduansha wetland of the Yangtze River estuary to investigate differences in conversion patterns of OC from two decayed plant litters of different characteristics using traditional physicochemical indicators and stable isotope tracing. Additionally, the mechanism of biotransformation was investigated through analysis of soil microbial community structure. Due to the higher content of lignin and cellulose in P. communis litter, the associated soil microbial community was more conducive to the formation of soil humus (HS). By contrast, more easily decomposable S. alterniflora litter induced its related soil microbial community more amenable to mineralization. Consequently, OC from decayed S. alterniflora litter remained in soil for less time than that from decayed P. communis, and the lost OC was more readily converted into CO2. OC from decayed P. communis was degraded very slowly during the early stage of conversion (November), and its longer duration in soil was favorable for HS formation. Analysis of the conversion of intermediates derived from different types of decayed plants can provide insight into plant litter input and SOC formation, and indicate the whereabouts of lost OC. From the perspective of plant biomass and conversion of plant litter-derived OC, P. communis is more conducive to soil carbon sequestration than S. alterniflora.