title: Methane Emissions and Microbial Communities as Influenced by Dual Cropping of Azolla along with Early Rice.
abstract: Azolla caroliniana Willd. is widely used as a green manure accompanying rice, but its ecological importance remains unclear, except for its ability to fix nitrogen in association with cyanobacteria. To investigate the impacts of Azolla cultivation on methane emissions and environmental variables in paddy fields, we performed this study on the plain of Dongting Lake, China, in 2014. The results showed that the dual cropping of Azolla significantly suppressed the methane emissions from paddies, likely due to the increase in redox potential in the root region and dissolved oxygen concentration at the soil-water interface. Furthermore, the floodwater pH decreased in association with Azolla cultivation, which is also a factor significantly correlated with the decrease in methane emissions. An increase in methanotrophic bacteria population (pmoA gene copies) and a reduction in methanogenic archaea (16S rRNA gene copies) were observed in association with Azolla growth. During rice cultivation period, dual cropping of Azolla also intensified increasing trend of 1/Simpson of methanogens and significantly decreased species richness (Chao 1) and species diversity (1/Simpson, 1/D) of methanotrophs. These results clearly demonstrate the suppression of CH4emissions by culturing Azolla and show the environmental and microbial responses in paddy soil under Azolla cultivation.
authors.affiliation: College of Agriculture and Biotechnology, China Agricultural University, Beijing, China.|Plant &Soil Science Section, Department of Plant and Environmental Science, Faculty of Science, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: Jingna
authors.initials: J
authors.lastname: Liu
authors.affiliation: College of Agriculture and Biotechnology, China Agricultural University, Beijing, China.
authors.forename: Heshui
authors.initials: H
authors.lastname: Xu
authors.affiliation: College of Agriculture and Biotechnology, China Agricultural University, Beijing, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: College of Agriculture and Biotechnology, China Agricultural University, Beijing, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.affiliation: College of Agriculture and Biotechnology, China Agricultural University, Beijing, China.
authors.forename: Yuegao
authors.initials: Y
authors.lastname: Hu
authors.affiliation: College of Agriculture and Biotechnology, China Agricultural University, Beijing, China.
authors.forename: Zhaohai
authors.initials: Z
authors.lastname: Zeng
mesh_terms: D000704:Analysis of Variance; D001105:Archaea / Q000235:genetics; D044822:Biodiversity; D016000:Cluster Analysis; D029624:Ferns / Q000382:microbiology* / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D008697:Methane / Q000737:chemistry; D064307:Microbiota; D012275:Oryza / Q000382:microbiology* / Q000502:physiology*; D012621:Seasons; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology
chemical_list: D012987:Soil; D008697:Methane