Phospholipid 13 C stable isotopic probing during decomposition of wheat residues Zhen Bai a,b, *, Chao Liang a,c, **, Samuel Bodé b , Dries Huygens b,d , Pascal Boeckx b a State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, PR China b Isotope Bioscience Laboratory—ISOFYS, Ghent University, Ghent, Belgium c DOE Great Lakes Bioenergy Research Center, University of Wisconsin, Madison, USA d Institute of Agricultural Engineering and Soil Science, Faculty of Agricultural Sciences, Universidad Austral de Chile, Valdivia, Chile A R T I C L E I N F O Article history: Received 3 April 2015 Received in revised form 22 September 2015 Accepted 24 September 2015 Available online 4 November 2015 Keywords: Soil carbon Kinetics Microbial groups 13 C-labeled wheat Isotope ratio mass spectrometry (IRMS) Phospholipid fatty acid (PLFA) A B S T R A C T Disentangling the kinetics of the soil microbial community succession, which is simultaneously driven by newly added plant materials and extant soil organic matter (SOM), can enrich our knowledge on microbial carbon (C) utilization patterns under residue amendment. This understanding might be useful to predict the rapid responses of specific microbial functional groups and develop strategies for balancing the terrestrial C budget. Therefore, our objective was to characterize and estimate the parameters of the microbial community dynamics profiled by phospholipid fatty acids (PLFA) from 13 C-labeled wheat residues and SOM. We conducted a 21-day microcosm study using two different arable systems (conventional tillage, CT; no-till, NT) amended with three types of 13 C-labeled wheat residues (grains, leaves and roots). The abundances and isotopic fractions of 13 CO 2 flux and 13 C-labeled PLFA were measured via gas trace isotope ratio mass spectrometry (IRMS) and gas chromatography-combustion- isotope ratio mass spectrometry (GC-c-IRMS), respectively. A double exponential model was used to describe the synthesis-degradation kinetics of PLFA from different microbial origins. We found that the PLFA formation generally reaches its maximal abundance within 7 days (except for PLFA from actinomycetes). The SOM- and wheat residue-derived C fluxes, as well as their PLFA profiles, were inconsistently impacted by the residue quality or the tillage regime over the incubation period. Specifically, the abundances of residue-derived CO 2 and PLFAs significantly decreased in the following order: grains > leaves > roots. However, those abundances derived from SOM were the lowest with the leaf residue treatments. Residue-derived PLFA patterns were highly influenced by fungi and G  bacteria, while G + bacterial and actinomycete PLFAs were preferentially linked to extant SOM mineralization. Compared to the residue-derived counterparts, the SOM-derived microbes were characterized by higher G + /G  bacteria and cy17:0/C16:1v 7c ratios, as well as lower fungi/bacteria PLFA ratios. Such distinction between residue and SOM was also evidenced by the contrasting tillage effects on C mineralization and the ratios of cy17:0/C16:1v 7c and fungal/G  bacterial PLFA. Our study provides evidence with important implications for adapting the microbial-mediated processes of soil C management through residue quality control. ã 2015 Elsevier B.V. All rights reserved. 1. Introduction The dynamics of microbial communities responsible for soil organic matter (SOM) metabolism (Waldrop and Firestone, 2004) are dependent on the quality of organic substrates (Kuzyakov, 2010; Potthast et al., 2010). The two primary natural resources are plant residues and native SOM pools (Kramer and Gleixner, 2006). Modeling the C flows in soil microbial communities can aid in the prediction of rapid responses and strategies of specific functional groups for balancing the global terrestrial C budgets (Schmidt et al., 2011). Large proportions of exogenous plant residues can be quickly incorporated into soils within days or weeks (Vanlauwe et al., 2005; Brant et al., 2006; Duong et al., 2009; Rubino et al., 2010; Marschner et al., 2011). This immobilized fraction mainly contributes to the soil labile C pool, which accounts for up to 15% of the total SOM (Gleixner et al., 1999) with a turnover time of 0.1–1.5 years (Gleixner et al., 2002; Lal, 2004). In some cases, residues with low lignin and high N contents can lead to a fast * Corresponding author. ** Corresponding author. E-mail addresses: baizhen@iae.ac.cn (Z. Bai), cliang823@gmail.com (C. Liang). http://dx.doi.org/10.1016/j.apsoil.2015.09.009 0929-1393/ ã 2015 Elsevier B.V. All rights reserved. Applied Soil Ecology 98 (2016) 65–74 Contents lists available at ScienceDirect Applied Soil Ecology journal homepage: www.elsevier.com/locate/apsoil