Contrasting response of organic carbon mineralisation to iron oxide addition under conditions of low and high microbial
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ORIGINAL PAPER
Contrasting response of organic carbon mineralisation to iron oxide addition under conditions of low and high microbial biomass in anoxic paddy soil Yuhong Li 1 & Muhammad Shahbaz 2,3 & Zhenke Zhu 1 Yangwu Deng 5 & Jinshui Wu 1,6 & Tida Ge 1,7
&
Anlei Chen 1 & Paolo Nannipieri 4 & Baozhen Li 1 &
Received: 13 May 2020 / Revised: 9 September 2020 / Accepted: 17 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In contrast to what is observed in aerobic uplands, microbial biomass and the presence of electron acceptors, such as iron oxides, play a crucial role in regulating soil organic C (SOC) mineralisation in paddy soils. However, the related underlying mechanisms are still poorly explored. We conducted an anaerobic incubation study to investigate changes in CO2 emissions from SOC and acetate (13C-labeleld) in response to iron oxide (ferrihydrite and goethite) addition in chloroform-fumigated and unfumigated paddy soils. The iron oxides, as electron acceptors, increased CO2 emissions from SOC with stronger impact under ferrihydrite than goethite addition. However, the acetate addition, as a preferable C source for reducing microbes, decreased SOC mineralisation and caused a negative priming effect. CO2 emission from both acetate and SOC was affected by microbial biomass change. In the acetate-treated soil, goethite in the fumigated soil (i.e. high microbial biomass) increased CO2 emissions from acetate, providing electron acceptors, and decreased CO2 emissions from SOC. Ferrihydrite accepted electrons and adsorbed acetate, resulting in a slight decline in CO2 emission from acetate. However, in the fumigated soil (i.e. low microbial biomass), both iron oxide additions reduced CO2 emissions from acetate and SOC and likely the dominant role of both iron oxides shifted from being electron acceptors to being adsorbents, thus limiting acetate accessibility to microorganisms. The results suggest that microbial biomass is a key driver in shifting the effects of iron oxides on organic C mineralisation in anaerobic paddy soils. Keywords Acetate . Anaerobic mineralisation . Iron oxides . Microbial biomass . Rice paddy soil . Soil organic C
Introduction Rice paddies, which are artificial wetlands, cover approximately 165 million ha area worldwide, contributing to a large
proportion of global soil organic C (SOC) stocks (Conrad et al. 2012; Ge et al. 2017; Guo and Lin 2001). C dynamics in paddy soils are crucial to global C sequestration and associated greenhouse gas (CO2) flux emissions (Atere et al. 2020;
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00374-020-01510-8) contains supplementary material, which is available to authorized users. * Zhenke Zhu [email protected] 1
Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha 410125, Hunan, China
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Departme
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