Light inhibition of carbon mineralization associated with iron redox processes in calcareous paddy soil

• Published in: Journal of soils and sediments Vol. 20; no. 8; pp. 3171 - 3180
• Main Authors: Wang, Xugang, Sun, Lirong, Chen, Zhihuai, Guo, Dayong, Fan, Haolong, Xu, Xiaofeng, Shi, Zhaoyong, Chen, Xianni
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2020; Springer Nature B.V
• Subjects: Bacteria; Biomass; Calcareous soils; Carbon; Carbon cycle; Carbon dioxide; Carbon fixation; Carbon sequestration; Community structure; Cyanobacteria; Earth and Environmental Science; Emissions; Environment; Environmental factors; Environmental Physics; Gases; Gene sequencing; Greenhouse effect; Greenhouse gases; Headspace; Incubation period; Inorganic carbon; Iron; Light; Light effects; Methane; Microorganisms; Mineralization; Oxidoreductions; Periodic variations; Photosynthesis; Phototrophic bacteria; Planting density; Rice fields; rRNA 16S; Seasonal variations; Sec 3 • Remediation and Management of Contaminated or Degraded Lands • Research Article; Serum; Slurries; Soil; Soil analysis; Soil dynamics; Soil microorganisms; Soil Science & Conservation; Soil structure; Soils; Terrestrial ecosystems; Terrestrial environments; Water chemistry; Oxygenic photosynthesis; Carbon mineralization; emission; Iron redox cycling; CO; Greenhouse gases
• ISSN: 1439-0108; 1614-7480
• DOI: 10.1007/s11368-020-02660-w

Purpose The iron redox cycle is closely tied to the fate of carbon in terrestrial ecosystems, especially paddy soils. Varies diurnally and seasonally, light—the crucial environmental factor—may be a fundamental factor elucidating temporal and spatial variabilities of carbon-containing gases emission. The role of sunlight in the iron-mediated carbon cycle, however, has not been fully elucidated. We conduct this study to test the role of light in the iron-mediated carbon cycling. Materials and methods In this study, we conducted anaerobic incubation experiments of a calcareous paddy soil in serum vials under alternating dark and light conditions. The dynamic evolution of the carbon and iron contents was evaluated by measuring the CO 2 , CH 4 , and O 2 concentrations in the headspace of the vials, as well as the water-soluble inorganic carbon, microbial biomass carbon, and HCl-extractable ferrous iron contents in soil slurries. We also analyzed the soil microbial community structure by high-throughput 16S rRNA gene sequencing. Results and discussion The results highlighted the positive correlation between carbon mineralization and ferric iron reduction under dark conditions. Under light conditions, however, ferrous iron was oxidized by the O 2 generated via oxygenic photosynthesis of phototrophic bacteria such as Cyanobacteria , along with a decreased production of CO 2 , CH 4 , and water-soluble inorganic carbon. The abundance of Cyanobacteria positively correlated to O 2 levels and MBC content significantly. Light-induced periodic variations in the redox conditions facilitated carbon fixation in microbial biomass and up to 31.79 μmol g −1 carbon was sequestrated during 30 days light incubation. Conclusions These results indicate that light inhibits the emission of carbon-containing greenhouse gases associated with the iron redox cycle in calcareous paddy soil. Assimilation of inorganic carbon by phototrophs may responsible for the inhibition of carbon mineralization. Our study suggests that procedures allowing more light to reach the soil surface, for instance, reducing the planting density, may mitigate greenhouse gas emissions and promote carbon sequestration in paddy soils.