Soil labile organic carbon indicating seasonal dynamics of soil organic carbon in northeast peatland

Abstract

Peatlands have persisted as massive carbon pool in terrestrial ecosystem. Labile organic carbon (LOC) plays a vital role in carbon cycling in high-latitude peatlands, which is an important indicator of seasonal soil organic carbon (SOC) dynamics. However, the contributions of LOC fractions are poorly understood. Here, soil samples were collected at a high-latitude peatland site located in Northeastern China, and SOC and its labile fractions, including dissolved organic carbon (DOC), light-fraction organic carbon (LFOC), easily oxidizable carbon (EOC) and microbial biomass carbon (MBC) were determined, as well as the environmental and microbial parameters. The results presented seasonal variations in SOC with 352.09 ± 4.93 g/kg in July, 357.84 ± 14.02 g/kg in September, 366.74 ± 17.41 g/kg in November, 413.58 ± 7.83 g/kg in January, and 422.17 ± 8.74 g/kg in April. It was shown that DOC and LFOC were to be important indicators in seasonal carbon dynamics from an elastic net regression model. Although DOC and LFOC accounted for only 3.88% ± 0.50% and 0.34% ± 0.21% in this peatland, they might drive the changes in SOC. The redundancy analysis (RDA) model indicated that pH, total nitrogen (TN), precipitation, soil temperature and actinomycetes PLFAs are important driving factors of SOC pools. A structural equation modeling (SEM) was used to part the direct and indirect effects of factors on soil carbon dynamics based on the covariance structures. The results showed that environmental factors influenced SOC pools through different pathways. Soil pH affected carbon pools directly, while soil temperature influenced the carbon cycling indirectly by affecting soil microbes based on the path analysis. This study suggests that DOC and LFOC had the potential to cause the changes of carbon dynamics in northeast crater peatlands.