Contents lists available at ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil Microbial responses to temperature sensitivity of soil respiration in a dry fallow cover cropping and submerged rice mono-cropping system Muhammad Israr Khan a , Hyun Young Hwang a , Gil Won Kim a , Pil Joo Kim a,b,⁎ , Suvendu Das b,⁎ a Division of Applied Life Science, Gyeongsang National University, Jinju 660-701, South Korea b Institute of Agriculture and Life Sciences, Gyeongsang National University, Jinju 660-701, South Korea ARTICLE INFO Keywords: Soil respiration Decomposition Temperature sensitivity Q 10 PLFA Microbial community ABSTRACT Soil heterotrophic respiration (SHR) increases exponentially with temperature and this general information has been incorporated into soil carbon models. However, the positive feedback of warming to SHR remains un- certain, mostly due to the differential response of soil microbial community to warming under dry and flooded conditions in a rice mono-cropping system. In this study, we aimed to evaluate the relationship between SHR and microbial functional groups during the fallow and flooded rice cultivation seasons under changing temperature in a rice mono-cropping system. Field experiments were conducted to investigate SHR, soil microbial functional groups and biomass, and temperature sensitivity of SHR (Q 10 ) under dry fallow conditions during the cover cropping season and under flooded conditions during the rice cropping season. We found that SHR increased with increasing air and soil temperature, carbon availability, and soil microbial community composition and biomass in the fallow season, whereas a decrease in SHR in spite of an increase in temperature and carbon availability was observed under flooded conditions during the rice cropping season. Furthermore, a nonlinear response of microbial community composition and biomass with SHR was noticed during the flooded rice cropping season. This suggests that flooding could be the limiting factor for temperature sensitivity of SHR as well as microbial community composition in a rice mono-cropping system. Flooding the soil significantly (p < 0.01) decreased Q 10 . We therefore conclude that temperature, moisture region and carbon availability, rather than only soil microbial community composition are responsible for the spatiotemporal variation in SHR in a rice mono-cropping system in this region. 1. Introduction Soil heterotrophic respiration (SHR) is a major source of carbon dioxide (CO 2 ) in terrestrial ecosystems (Wieder et al., 2013). Carbon dioxide released by microbial activities in association with soil organic matter decomposition (soil heterotrophic respiration) in soils is gov- erned by abiotic and biotic components. Although abiotic components, primarily temperature, and moisture are well recognized as important variables for predicting organic matter decomposition and thus soil CO 2 efflux, the importance of soil microorganisms (biotic factor) as a de- terminant of SHR is not being critically examined, probably due to enormous diversity and different capacities of individual microbial groups in soil to degrade available and complex form of C (Waring et al., 2013). Moreover, the role of individual microbial groups on SHR under changing temperature and moisture regime in an ecosystem re- mains uncertain and widely debated (Curiel Yuste et al., 2007). Several studies have shown that SHR increases exponentially with temperature and this general relationship has been incorporated into soil-carbon and Earth-system models (Wieder et al., 2013; Karhu et al., 2014). However, the positive feedback of warming to SHR remains uncertain, because the response of soil microbial communities to changing temperatures has the potential to either decrease or increase (Karhu et al., 2014). These inconsistent responses of soil microbial communities to the temperature sensitivity of SHR could be due to the influence of other environmental variables primarily soil moisture, which could markedly affects SOM decomposition (Suseela et al., 2012). Unlike, forest ecosystems, the role of microbial community re- sponse in controlling the temperature sensitivity of SHR in agricultural systems is not clearly understood due to different cropping practices and field management, which strongly influence not only the microbial community but also the SHR (Tian et al., 2013; Tang et al., 2017). Among agricultural systems, rice mono-cropping systems are unique ecological systems which comprise both flooded and dried soil condi- tions. For example, in Korean paddy fields, soils are kept under water submergence for almost three months during the rice cultivation season and under dry, aerobic conditions for more than six months during the https://doi.org/10.1016/j.apsoil.2018.04.002 Received 5 December 2017; Received in revised form 26 March 2018; Accepted 4 April 2018 ⁎ Corresponding authors at: Division of Applied Life Science, Gyeongsang National University, Jinju 660-701, South Korea (P.J. Kim). E-mail addresses: pjkim@gnu.ac.kr (P.J. Kim), suvendu.bls@gmail.com (S. Das). Applied Soil Ecology 128 (2018) 98–108 Available online 17 April 2018 0929-1393/ © 2018 Elsevier B.V. All rights reserved. T