Molecular distributions and carbon isotopic compositions of phospholipid ester-linked fatty acids in a soil profile of the Dinghushan Biosphere Reserve, south China: Implications for soil organic carbon accumulation

  • Author(s): Shengyi Mao, Yongge Sun, Deqiang Zhang, Juxiu Liu, and Guoyi Zhou
  • DOI: 10.3319/TAO.2017.10.06.03
  • Keywords: Phospholipid ester-linked fatty acids, Dinghushan Biosphere Reserve, carbon accumulation
  • PLFAs in soil from Dinghushan suggest the dominance of the Gram-positive bacteria
  • PLFAs that specific to sulfate-reducing bacteria are identified high concentrations
  • PLFAs showed the rise of the depth of the anaerobic zone may be caused by acidic rain
Abstract

Phospholipid ester-linked fatty acids (PLFA) were used to investigate the microbial ecology and its association with carbon accumulation in one soil profile from the Dinghushan Biosphere Preserve in south China, in order to probe the mechanisms that control the carbon accumulation at the depth of 0-20 cm in the Dinghushan forest soil profile. With molecular distributions and carbon isotopic compositions of single PLFA, 10me16:0 and cyc17:0, that are specific to sulfate-reducing bacteria (e.g., Desulfobacter and Desulfobacterium autotrophicum) were identified with relatively high concentrations through the profile. Methanotrophic bacteria, fungi, the gram-negative bacteria, the gram-positive bacteria are also identified. The Sulfate reducing bacteria (SRB)occur in the top 10 cm, and methanotrophic bacteria and fungi are not present below 10 cm, and the gram-negative bacteria are reduced with gram-positive bacteria dominating at that depth; all of which indicated that the activities of some of the microorganisms were inhibited, from which we infer that the available carbon source and oxygen content of micro environment may be reduced below 10 cm of the profile. The shallow depth (top 10 cm) of the soil anaerobic zone at the Wukesong profile, compared to the normal soil anaerobic zone, which is the top 20-30 cm, is considered to be mainly the result of the high precipitation of acidic rain. The physicochemical reactions caused by acid rain in the soil system result in a decreased soil porosity, and a correspondingly decreased porosity-dependent oxygen concentration, leading to the thriving of SRB in the shallow depth. Although the increase of soil organic carbon stock is attributed to numerous factors, the decreasing rate of litter decomposition in the topsoil layer, together with the rise of the depth of the anaerobic zone, may play key roles in the carbon accumulation in the depth of 0-20 cm in the soil profile from the Dinghushan Biosphere Preserve.

 

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