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Published (Version of Record)CC BY V4.0, Open Access
Journal article
Soil microbial populations in deep floodplain soils are adapted to infrequent but regular carbon substrate addition
Soil biology & biochemistry, Vol.122, pp.60-70
2018
Abstract
Floodplain soils provide an important link in the land-ocean aquatic continuum. Understanding microbial activity in these soils, which can be many metres deep, is a key component in our understanding of the role of floodplains in the carbon (C) cycle. We sampled the mineral soil profile to 3 m depth from two floodplain sites under long-term pasture adjacent to the river Culm in SW England, UK. Soil chemistry (C, nitrogen (N), phosphorus (P), soil microbial biomass (SMB), moisture content) and soil solution (pH, dissolved organic C (DOC) and N, nitrate, ammonium, water extractable P) were analysed over the 3 m depth in 6 increments: 0.0–0.2, 0.2–0.7, 1.0–1.5, 1.5–2.0, 2.0–2.5, and 2.5–3.0 m. 14C-glucose was added to the soil and the evolution of 14CO2 measured during a 29 d incubation. From soil properties and 14C-glucose mineralisation, three depth groups emerged, with distinct turnover times extrapolated from initial k1 mineralisation rate constants of 2 h (topsoil 0.0–0.2 m), 4 h (subsoil 0.2–0.7 m), and 11 h (deep subsoil 1.0–3.0 m). However, when normalised by SMB, k1 rate constants had no significant differences across all depths. Deep subsoil had a 2 h lag to reach maximal 14CO2 production whereas the topsoil and subsoil (0.2–0.7 m) achieved maximum mineralisation rates immediately. SMB decreased with depth, but only to half of the surface population, with the proportion of SMB-C to total C increasing from 1% in topsoil to 15% in deep subsoil (>1.0 m). The relatively large SMB concentration and rapid mineralisation of 14C-glucose suggests that DOC turnover in deep soil horizons in floodplains is limited by access to biologically available C and not the size of the microbial population.
•Dissolved organic carbon dynamics analysed in 3 m soil profiles from a UK floodplain.•Floodplain soils maintain a large metabolically alert microbial biomass at depth.•Variation over depth in maximum mineralisation rate, with a 2 h lag in deep subsoil.•Mineralisation limited by labile C availability, not size of microbial population.•Stoichiometric control on C mineralisation varies with depth.
Details
- Title
- Soil microbial populations in deep floodplain soils are adapted to infrequent but regular carbon substrate addition
- Authors/Creators
- E.L. Cressey - University of ExeterJ.A.J. Dungait - Rothamsted ResearchD.L. Jones - Bangor UniversityA.P. Nicholas - University of ExeterT.A. Quine - University of Exeter
- Publication Details
- Soil biology & biochemistry, Vol.122, pp.60-70
- Publisher
- Elsevier Ltd
- Identifiers
- 991005560331407891
- Copyright
- Crown Copyright © 2018
- Murdoch Affiliation
- Centre for Sustainable Farming Systems
- Language
- English
- Resource Type
- Journal article
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InCites Highlights
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- Collaboration types
- Domestic collaboration
- Citation topics
- 3 Agriculture, Environment & Ecology
- 3.45 Soil Science
- 3.45.112 Soil Carbon Dynamics
- Web Of Science research areas
- Soil Science
- ESI research areas
- Agricultural Sciences