Contents lists available at ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil Enhanced labile carbon fow in soil-microbes-plant-atmospheric continuum in rice under elevated CO 2 and temperature leads to positive climate change feed-back S.R. Padhy a , P. Bhattacharyya a, ⁎ , P.K. Dash a , K.S. Roy b , S. Neogi c , M.J. Baig a , P. Swain a , A.K. Nayak a , T. Mohapatra d a ICAR-National Rice Research Institute (NRRI), Cuttack, Odisha, India b Department of Environmental Science, SRM University, Delhi-NCR, Sonepat, Haryana, India c Ashoka Trust for Research in Ecology and the Environment (ATREE), Bangalore-560064, Karnataka, India d Indian Council of Agricultural Research, New Delhi, India ARTICLE INFO Keywords: Climate change feedback Elevated CO 2 and temperature Microbial carbon fxation Photosynthesis Root exudates Rice ABSTRACT Lowland rice along with wetland sequesters one third of terrestrial carbon (C) which is responsible for both positive and negative feed-back to climate change. Labile C pools are sensitive to anticipated climate change condition (elevated CO 2 and temperature). Those may eventually afect the C-stock in soil-microbes-plant-at- mospheric (SMPA) continuum through priming efect and could enhance positive climate change feedback. Therefore, the objectives of the study were to analysis the efect elevated CO 2 on C partitioning in rice-plant parts, soil labile C pools, and methane emission; along with identify related bacterial diversities and C-fxation pathways through whole genome metagenomic approach. The labile carbon fow in SMPA continuum was es- timated for 3 years in lowland rice under elevated CO 2 and temperature in open top chambers (OTCs). Rice was grown under ambient CO 2 (a-CO 2 ; 390 ± 20 μmol mol −1 ) and elevated CO 2 and temperature (e-CO 2 T; 550 ± 20 μmol mol −1 ; 2 °C above ambient) under OTCs with replications. Soil labile C pools were increased by 25.4 to 38.9%, under e-CO 2 T over a-CO 2. In microbes, biomass C, C-fxation pathways (metagenomic analysis) and C related soil enzymes were assayed. In atmosphere, the methane emission was measured and in plant system, C in diferent plant- parts, photosynthetic rates, root exudates-C were estimated to quantify labile C fow. Root exudates C was increased by 31.9% and microbial biomass C was enhanced by 23.3% under e-CO 2 T. Primarily, 12 soil bacterial genera which were responsible for C-fxation were dominant with higher abundance reads under e-CO 2 T. In C-fxation, dicarboxylate hydroxybutyrate cycle pathway and reductive citric acid cycle pathway were predominant under a-CO 2 and e-CO 2 T, respectively. The methane emission was 26.0 and 26.8% higher under e-CO 2 T than a-CO 2 at vegetative and reproductive stage of crop, respectively. Further, we got higher biomass accumulation, photosynthetic rate and stomatal conductance of rice under e-CO 2 T. Therefore, these augmented labile C fows in SMPA continuum may trigger the priming of soil C stocks, and at the same time could afect the system as a whole and results a positive feedback to climate change. 1. Introduction Wet land including lowland rice (anthropogenic wetland; a sub-set of total wet land) stores about 33% of terrestrial carbon (C) (Limpens et al., 2008; Dise, 2009). It plays a vital role in maintaining atmospheric carbon dioxide (CO 2 ) and methane (CH 4 ) concentrations. Carbon di- oxide and CH 4 are major greenhouse gases (GHGs) regulate climate change feedback. The present atmospheric CO 2 concentration is about 390 ± 20 μmol mol −1 and with the current rate of increase of 1.9 μmol mol −1 y −1 , it is projected to reach 700 μmol mol −1 by the end of 21st century (Solomon et al., 2007; IPCC, 2007, 2014). Global sur- face temperature is also predicted to increase up to 1–4 °C by the end of 21st century (O'neill et al., 2017; Chen et al., 2018) along with increase in atmospheric CO 2 concentration. This increasing temperature has a signifcant impact on terrestrial C budgets that could cause both posi- tive and negative feedback to climate change (Peñuelas et al., 2017; Yang et al., 2019). Moreover, increasing CO 2 concentration coupled with temperature rise causes global warming and climate change. The https://doi.org/10.1016/j.apsoil.2020.103657 Received 23 August 2019; Received in revised form 2 May 2020; Accepted 8 May 2020 ⁎ Corresponding author. E-mail address: pratap162001@gmail.com (P. Bhattacharyya). Applied Soil Ecology 155 (2020) 103657 0929-1393/ © 2020 Elsevier B.V. All rights reserved. T