title: Discrimination in Degradability of Soil Pyrogenic Organic Matter Follows a Return-On-Energy-Investment Principle.
abstract: A fundamental understanding of biodegradability is central to elucidating the role(s) of pyrogenic organic matter (PyOM) in biogeochemical cycles. Since microbial community and ecosystem dynamics are driven by net energy flows, then a quantitative assessment of energy value versus energy requirement for oxidation of PyOM should yield important insights into their biodegradability. We used bomb calorimetry, stepwise isothermal thermogravimetric analysis (isoTGA), and 5-year in situ bidegradation data to develop energy-biodegradability relationships for a suite of plant- and manure-derived PyOM (n = 10). The net energy value (ΔE) for PyOM was between 4.0 and 175 kJ mol(-1); with manure-derived PyOM having the highest ΔE. Thermal-oxidation activation energy (Ea) requirements ranged from 51 to 125 kJ mol(-1), with wood-derived PyOM having the highest Ea requirements. We propose a return-on-investment (ROI) parameter (ΔE/Ea) for differentiating short-to-medium term biodegradability of PyOM and deciphering if biodegradation will most likely proceed via cometabolism (ROI < 1) or direct metabolism (ROI ≥ 1). The ROI-biodegradability relationship was sigmoidal with higher biodegradability associated with PyOM of higher ROI; indicating that microbes exhibit a higher preference for "high investment value" PyOM.
authors.affiliation: School of Geology, Energy and the Environment, Texas Christian University , Fort Worth, Texas 76129, United States.
authors.forename: Omar R
authors.initials: OR
authors.lastname: Harvey
authors.affiliation: Department of Oceanography, Texas A&M University , College Station, Texas 77840, United States.
authors.forename: Allison N
authors.initials: AN
authors.lastname: Myers-Pigg
authors.affiliation: Marine Science Laboratory, Pacific Northwest National Laboratory , Sequim, Washington 98382, United States.
authors.forename: Li-Jung
authors.initials: LJ
authors.lastname: Kuo
authors.affiliation: NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute , Menangle, New South Wales 2568, Australia.
authors.forename: Bhupinder Pal
authors.initials: BP
authors.lastname: Singh
authors.affiliation: Department of Biological Sciences, The University of Southern Mississippi , Hattiesburg, Mississippi 39406, United States.
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Kuehn
authors.affiliation: Department of Oceanography, Texas A&M University , College Station, Texas 77840, United States.|Department of Marine Sciences, Texas A&M University at Galveston , Galveston, Texas 77553 United States.
authors.forename: Patrick
authors.initials: P
authors.lastname: Louchouarn
mesh_terms: D001673:Biodegradation, Environmental; D017753:Ecosystem; D008372:Manure; D009930:Organic Chemicals / Q000378:metabolism*; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D008372:Manure; D009930:Organic Chemicals; D012987:Soil