pH controls over anaerobic carbon mineralization, the efficiency of methane production, and methanogenic pathways in peatlands across an ombrotrophic–minerotrophic gradient

• Published in: Soil biology & biochemistry 2012-11, Vol.54, p.36-47
• Main Authors: Ye, Rongzhong, Jin, Qusheng, Bohannan, Brendan, Keller, Jason K., McAllister, Steven A., Bridgham, Scott D.
• Format: Article
• Language: English
• Subjects: Acetate pooling; acetates; Agronomy. Soil science and plant productions; Anaerobic carbon mineralization; Biochemistry and biology; biogeochemical cycles; Biological and medical sciences; carbon; carbon dioxide; Chemical, physicochemical, biochemical and biological properties; Efficiency of methane production; electrons; fermentation; Fundamental and applied biological sciences. Psychology; humic substances; methane; Methane pathways; methane production; mineralization; Ombrotrophic–minerotrophic gradient; peat; Peatlands; Physics, chemistry, biochemistry and biology of agricultural and forest soils; slurries; Soil science
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2012.05.015

Methane (CH4) production varies greatly among different types of peatlands along an ombrotrophic–minerotrophic hydrogeomorphic gradient. pH is thought to be a dominant control over observed differences in CH4 production across sites, and previous pH manipulation experiments have verified the inhibitory effect of low pH on CH4 production. In this experiment, we asked (i) if the major effect of low pH is direct inhibition of one or both pathways of methanogenesis and/or inhibition of ‘upstream’ fermentation that provides substrates for methanogens, and (ii) to what extent is pH sufficient to explain differences in CH4 production relative to other factors that co-vary across the gradient. To address these questions, we adjusted the pH of peat slurries from 6 peatlands to 4 levels (3.5, 4.5, 5.5, and 6.5) that reflected their range of native pH, maintained these pH levels over a 43-day anaerobic laboratory incubation, and measured a suite of responses within the anaerobic carbon cycle. Higher pH caused a significant increase in CO2 production in all sites. Regardless of site, time, and pH level, the reduction of inorganic electron acceptors contributed to