Contents lists available at ScienceDirectApplied Soil Ecologyjournal homepage: www.elsevier.com/locate/apsoilThe microbial network in naturally fertile paddy soil possibly facilitatesfunctional recruitment in the rice mature stageXuesong Luo a,b , Shun Han a , Xiaoqian Fu a , Xiang Li a , Li Wang a,b , Shaobing Peng c , Wenli Chen a, ? ,Qiaoyun Huang a,b, ?a State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, Chinab Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, HuazhongAgricultural University, Wuhan 430070, Chinac Crop Physiology and Production Center (CPPC), College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, ChinaA R T I C L E I N F OKeywords:Paddy soilMicrobial communityLow-yield f i eldHigh-yield f i eldFertilizersA B S T R A C THow agriculture practice, especially the nitrogen fertilization, inf l uences dif f erent paddy soil microbial eco-systems remains unclear. The bacterial communities in two paddy f i elds, which were distinguished by thenatural fertility level, were utilized in this study. Each f i eld held two control plots and two nitrogen-fertilizedones. The microbial communities mainly dif f ered in their relative abundances of Proteobacteria and Chlorof l exibetween the two f i elds. However, they were very similar in the α-diversity and enzymatic functions, as well astheir resistances indexes in response to the nitrogen fertilizers. Redundancy analysis indicated that phosphorus,nitrogen and potassium contents signif i cantly explained the variability of the communities in the two f i elds totalpotassium (TK) plus nitrogen level and TK alone signif i cantly explained the variation of the microbial com-munities in the high yield f i eld and the low yield, respectively. Network analysis data showed that the microbialcommunity in the high-yield f i eld possessed a higher connectivity, which might facilitate recruiting more mi-crobes that were predicted to drive organic matter decomposition, sulfate/iron reduction, nitrogen retention,and methane oxidation at the mature stage. The use of nitrogen fertilizer in the low yield f i eld would help torecruit microbial functions similar to those in the high-yield at the stage. This ecological process possibly sti-mulated nutrient availability for rice production in the present case.1. IntroductionMicrobial community drives C, N, P and S cycling in soils. In paddysoils, it rapidly changes in response to the environmental disturbance,especially the nitrogen fertilizers (Geisseler et al., 2017). The ammoniatype nitrogen fertilizer, urea, always lead to the decrease in microbialdiversity and the abundances of ammonia/methane-oxidizing Archeae,and the increase of ammonia-oxidizing bacteria (Fan et al., 2016). Insome cases, chemical fertilization with nitrogen was found to stimulatethe growth of gram-positive bacteria in some rice soils, while organicamendments cause the increases of bacteria and fungi, but Actinomy-cetes abundance decreased (Zhang et al., 2007, 2012). Nitrogen ferti-lizers also increased microbial biomass when the carbon availabilitywas relatively redundant (Lin et al., 2014). In a calcareous purplishpaddy f i eld, the chemical fertilizers increased paddy soil organiccarbon, soil moisture, available phosphorus, and total nitrogen, whiledecreased the nitrate-N, and also enriched Pseudomonadales,Xanthomonadales Nitrosomonadales, Methylococcales, and Methylophilales(Gu et al., 2017). A meta-analysis for the ef f ect of N addition on paddysoil microorganisms indicated that nitrogen generally increased mi-crobial biomass. The response of dif f erent microbial groups to nitrogenfertilizers is highly variable (Geisseler et al., 2017).Microorganisms rarely live alone as a pure culture in nature. Theyform various ecological relationships, ranging from mutualism tocompetition. Network analysis becomes increasingly used for the pre-diction of species interactions in environments (Faust et al., 2012). Atthe continental scale, the paddy soil microbial network module hubswere found to be af f i liated with Alphaproteobacteria and Actinobacteria,followed by Chlorof l exi, Firmicutes, Acidobacteria, and Nitrospirae.However, the topological properties of the empirical molecular ecolo-gical networks for dif f erent rotation system diverged (Jiang et al.,2016). Microbial network in a rice terrace showed multiple mutualisticinteractions among Sulfate-reducing bacteria, Fe(III)-reducing andmethane-oxidizing bacteria (Sun et al., 2018). In the calcareoushttps://doi.org/10.1016/j.apsoil.2018.12.008Received 10 September 2018; Received in revised form 26 November 2018; Accepted 10 December 2018? Corresponding authors at: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China.E-mail address: qyhuang@mail.hzau.edu.cn (Q. Huang).Applied Soil Ecology 135 (2019) 174–181Available online 21 December 20180929-1393/ © 2018 Elsevier B.V. All rights reserved.T
