Responses of Denitrification Rate and Denitrifying Bacterial Communities Carrying nirS and nirK Genes to Grazing in Peat
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ORIGINAL PAPER
Responses of Denitrification Rate and Denitrifying Bacterial Communities Carrying nirS and nirK Genes to Grazing in Peatland Xin Fang 1 & Rongbo Zheng 2 & Xuelian Guo 1 & Qian Fu 1 & Kun Zhang 1 Received: 20 November 2019 / Accepted: 24 February 2020 # Sociedad Chilena de la Ciencia del Suelo 2020
Abstract Improving knowledge on how the denitrifier community responds to grazing activity is essential to better understanding whether peatland nitrous oxide (N2O) emissions will react to grazing. To quantify the effects of grazing type on the denitrifier community, an experiment was conducted to determine how grazing types (pig uprooting, PU; yak tramping, YT) influence denitrification and the bacterial community in peatland. Soil samples were collected from control and two grazing types in the peatland of Southwest China. Soil physicochemical properties, denitrification rate (DR), and reductase assay activities were analyzed. Molecular methods were applied to determine the community of nirS and nirK genes. The relationship among DR, physicochemical properties, enzymatic activity, and denitrifier community was analyzed by Pearson correlation analysis, structural equation modeling (SEM), and canonical correspondence analysis (CCA). YT had a more significant influence on the ACE index, while PU affected the diversity index obviously. Grazing reduced unclassified Betaproteobacteria but increased unclassified Proteobacteria for nirS, while increased Bradyrhizobiaceae and decreased Phyllobacteriaceae for nirK. nirK was more sensitive to grazing disturbances than nirS. YT increased Bradyrhizobium and unclassified Proteobacteria, but Hyphomicrobiaceae disappeared in YT, and a reverse trend was observed in PU. Unclassified Chloroflexi and Nitrosomonadaceae were new denitrifier species that appeared in PU. Pig uprooting has a greater potential effect on denitrification than yak tramping in the peatland ecosystem. The alteration of soil environmental conditions is the dominant mechanism by which grazing type influences soil denitrification rate and the denitrifier community. Keywords Denitrification rate . Denitrifiers . Community structure . Grazing type . Peatland
1 Introduction Denitrification has received much attention in the background of global climate change because it affects N2O emissions to the atmosphere (Bouwman et al. 2013). N2O is a greenhouse gas and has a global warming potential approximately 296 times higher than the molar equivalent of carbon dioxide. In addition, N2O emission is currently Electronic supplementary material The online version of this article (https://doi.org/10.1007/s42729-020-00209-x) contains supplementary material, which is available to authorized users. * Xuelian Guo [email protected] 1
National Plateau Wetlands Research Center, Southwest Forestry University, Kunming 650224, People’s Republic of China
2
College of Chemical Engineering, Southwest Forestry University, Kunming 650224, People’s Republic of China
the single most crucial ozone-depleting emission and
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