title: Microbial respiration, but not biomass, responded linearly to increasing light fraction organic matter input: Consequences for carbon sequestration.
abstract: Rebuilding 'lost' soil carbon (C) is a priority in mitigating climate change and underpinning key soil functions that support ecosystem services. Microorganisms determine if fresh C input is converted into stable soil organic matter (SOM) or lost as CO2. Here we quantified if microbial biomass and respiration responded positively to addition of light fraction organic matter (LFOM, representing recent inputs of plant residue) in an infertile semi-arid agricultural soil. Field trial soil with different historical plant residue inputs [soil C content: control (tilled) = 9.6 t C ha-1versus tilled + plant residue treatment (tilled + OM) = 18.0 t C ha-1] were incubated in the laboratory with a gradient of LFOM equivalent to 0 to 3.8 t C ha-1(0 to 500% LFOM). Microbial biomass C significantly declined under increased rates of LFOM addition while microbial respiration increased linearly, leading to a decrease in the microbial C use efficiency. We hypothesise this was due to insufficient nutrients to form new microbial biomass as LFOM input increased the ratio of C to nitrogen, phosphorus and sulphur of soil. Increased CO2efflux but constrained microbial growth in response to LFOM input demonstrated the difficulty for C storage in this environment.
authors.affiliation: Soil Biology and Molecular Ecology Group, School of Earth and Environment and Institute of Agriculture, The University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Yichao
authors.initials: Y
authors.lastname: Rui
authors.affiliation: Soil Biology and Molecular Ecology Group, School of Earth and Environment and Institute of Agriculture, The University of Western Australia, Crawley, WA 6009, Australia.
authors.forename: Daniel V
authors.initials: DV
authors.lastname: Murphy
authors.affiliation: Soil Biology and Molecular Ecology Group, School of Earth and Environment and Institute of Agriculture, The University of Western Australia, Crawley, WA 6009, Australia.|College of Agriculture, Guizhou University, Guizhou 550025, China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Wang
authors.affiliation: Soil Biology and Molecular Ecology Group, School of Earth and Environment and Institute of Agriculture, The University of Western Australia, Crawley, WA 6009, Australia.|Department of Agriculture and Food Western Australia, South Perth, WA 6151, Australia.
authors.forename: Frances C
authors.initials: FC
authors.lastname: Hoyle
mesh_terms: D018533:Biomass; D057965:Carbon Sequestration; D008027:Light; D008962:Models, Theoretical; D009930:Organic Chemicals; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D009930:Organic Chemicals; D012987:Soil