Soil microbial populations in deep floodplain soils are adapted to infrequent but regular carbon substrate addition

A - Papers appearing in refereed journals

Cressey, E. L., Dungait, J. A. J., Jones, D. L., Nicholas, A. P. and Quine, T. A. 2018. Soil microbial populations in deep floodplain soils are adapted to infrequent but regular carbon substrate addition. Soil Biology and Biochemistry. 122, pp. 60-70. https://doi.org/10.1016/j.soilbio.2018.04.001

AuthorsCressey, E. L., Dungait, J. A. J., Jones, D. L., Nicholas, A. P. and Quine, T. A.
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.

KeywordsSoil organic carbon; Soil microbial biomass; C-labelling; dissolved organic carbon; Depth; Mineralisation; Floodplain; Stoichiometry
Year of Publication2018
JournalSoil Biology and Biochemistry
Journal citation122, pp. 60-70
Digital Object Identifier (DOI)https://doi.org/10.1016/j.soilbio.2018.04.001
Open accessPublished as ‘gold’ (paid) open access
FunderNERC - Natural Environment Research Council - Centre for Ecology Hydrology - CEH
Biotechnology and Biological Sciences Research Council
Funder project or codeS2N - Soil to Nutrition - Work package 1 (WP1) - Optimising nutrient flows and pools in the soil-plant-biota system
Publisher's version
Output statusPublished
Publication dates
Online12 Apr 2018
Publication process dates
Accepted02 Apr 2018
PublisherElsevier
Copyright licenseCC BY
Grant IDNE/E011713/1
BB/P01268X/1
ISSN0038-0717

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