de Sosa, LL, Glanville, HC, Marshall, MR, Schnepf, A, Cooper, DM, Hill, PW, Binley, A and Jones, DL (2018) Stoichiometric constraints on the microbial processing of carbon with soil depth along a riparian hillslope. Biology and Fertility of Soils, 54. 949 - 963. ISSN 0178-2762

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Soil organic matter (SOM) content is a key indicator of riparian soil functioning and in the provision of ecosystem services such as water retention, flood alleviation, pollutant attenuation and carbon (C) sequestration for climate change mitigation. Here, we studied the importance of microbial biomass and nutrient availability in regulating SOM turnover rates. C stabilisation in soil is expected to vary both vertically, down the soil profile and laterally across the riparian zone. In this study, we evaluated the influence of five factors on C mineralisation (C-min): (i) substrate quantity, (ii) substrate quality, (iii) nutrient (C, N and P) stoichiometry, (iv) soil microbial activity with proximity to the river (2 to 75m) and (v) as a function of soil depth (0-3m). Substrate quality, quantity and nutrient stoichiometry were evaluated using high and low molecular weight C-14-labelled dissolved organic (DOC) along with different nutrient additions. Differences in soil microbial activity with proximity to the river and soil depth were assessed by comparing initial (immediate) C-min rates and cumulative C mineralised at the end of the incubation period. Overall, microbial biomass C (MBC), organic matter (OM) and soil moisture content (MC) proved to be the major factors controlling rates of C-min at depth. Differences in the immediate and medium-term response (42days) of C-min suggested that microbial growth increased and carbon use efficiency (CUE) decreased down the soil profile. Inorganic N and/or P availability had little or no effect on C-min suggesting that microbial community growth and activity is predominantly C limited. Similarly, proximity to the watercourse also had relatively little effect on C-min. This work challenges current theories suggesting that areas adjacent to watercourse process C differently from upslope areas. In contrast, our results suggest that substrate quality and microbial biomass are more important in regulating C processing rates rather than proximity to a river.

Item Type: Article
Additional Information: This is the final published version of the article (version of record). It first appeared online via Springer Verlag at - please refer to any applicable terms of use of the publisher.
Uncontrolled Keywords: Recalcitrant carbon . Nitrogen . Phosphorus . Nutrient cycling . Subsoil
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Divisions: Faculty of Natural Sciences > School of Geography, Geology and the Environment
Depositing User: Symplectic
Date Deposited: 06 Nov 2018 11:58
Last Modified: 30 Mar 2021 10:10

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