Soil microbiome-induced changes in the priming effects of 13C-labelled substrates from rice residues

Authors: WANG, YIMIN - Hohai University; LI, MING - Chinese Academy Of Sciences; JIANG, CHUN-YU - Chinese Academy Of Sciences; LIU, MING - Chinese Academy Of Sciences; WU, MENG - Chinese Academy Of Sciences; LIU, PING - Chinese Academy Of Sciences; LI, ZHONG-PEI - Chinese Academy Of Sciences; Uchimiya, Sophie; YUAN, XU-YIN - Hohai University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/2020
Publication Date: 7/15/2020
Citation: Wang, Y.-M., Li, M., Jiang, C.-Y., Liu, M., Wu, M., Liu, P., Li, Z.-P., Uchimiya, M., Yuan, X.-Y. 2020. Soil microbiome-induced changes in the priming effects of 13C-labelled substrates from rice residues. Science of the Total Environment. 726:138562. https://doi.org/10.1016/j.scitotenv.2020.138562.
DOI: https://doi.org/10.1016/j.scitotenv.2020.138562

Interpretive Summary: Soil health is controlled by the composition and activity of microbial community, i.e., soil biology. Soil biology is greatly influenced by the chemical property of soil, especially the quality and quantity of soil organic carbon. This study employed rice husk/root biomass and its themochemical conversion product (biochar) as a probe to test how external inputs of organic carbon will impact the soil health. Isotope tracing technique was employed to differentiate added and native sources of carbon. Specific microbial community was responsible for consuming recalcitrant carbon of biochar, enabling carbon sequestration.

Technical Abstract: Biomass and its value added products, e.g., biochar, are promising inputs of the terrestrial C stock to promote soil health. Significant knowledge gap exists to understand the soil CO2 emission and microbial community response to exogenous organic substrate amendments. In particular, thermochemical conversion of biomass could alter the direction of priming effects (PEs) and mineralization of soil organic carbon (SOC). We studied the decomposition of 13C-labled organic materials (RR: rice root, RS: rice straw, RB: rice straw derived biochar), PEs and changes in phospholipid fatty acid (PLFA) in one-year laboratory incubation experiment. Soil amendments significantly (p<0.05) increased pH, available N, and available P, especially during the first 45 days of incubation experiment. Percentages of residual 13C-labled RB was greatest among amendments while capacities of soil CO2 emission was lowest. Furthermore, RB amendment caused negative PEs, while RR and RS caused positive PEs, which increased as a function of incubation time. RDA analyses showed that soil microbial community involved in the decomposition of different organic materials are significantly affected by soil properties after amendments. The 13C-labled PLFA analysis enabled the differentiation of specific microbial population response to various organic substrates. Gram-negative (G-) biomarkers cy17:0, cy 19:0 were sensitive to the decomposition of all three organic substrates, while Gram-positive (G+) bacteria a17:0 and actinobacteria 10Me16:0 biomarkers were only responsive to both RR and RS. Therefore, G- bacteria was the primary population mineralizing RB, while G+ bacteria was most abundant in mineralization of RR and RS. Percentages of actinobacteria populations were enhanced towards later incubation periods. Results of Pearson’s correlation (r > 0.5, p<0.01) indicated that soil priming effects are significantly modulated by the microbial communities using 13C-labled organic substrates. Actinobacteria populations, associated with substrate utilization, played a vital role in soil organic matter mineralization. Those evidence indicate that biochar is an excellent soil C sequestration agent than biomass, because its recalcitrant organic carbon could serve as the carbon source only for specific microbial communities.