Effect of Elevated CO₂ Concentration, Elevated Temperature and No Nitrogen Fertilization on Methanogenic Archaeal and Methane-Oxidizing Bacterial Community Structures in Paddy Soil

Abstract

Elevated concentrations of atmospheric CO2 ([CO2]) enhance the production and emission of methane in paddy fields. In the present study, the effects of elevated [CO2], elevated temperature (ET), and no nitrogen fertilization (LN) on methanogenic archaeal and methane-oxidizing bacterial community structures in a free-air CO2 enrichment (FACE) experimental paddy field were investigated by PCR-DGGE and real-time quantitative PCR. Soil samples were collected from the upper and lower soil layers at the rice panicle initiation (PI) and mid-ripening (MR) stages. The composition of the methanogenic archaeal community in the upper and lower soil layers was not markedly affected by the elevated [CO2], ET, or LN condition. The abundance of the methanogenic archaeal community in the upper and lower soil layers was also not affected by elevated [CO2] or ET, but was significantly increased at the rice PI stage and significantly decreased by LN in the lower soil layer. In contrast, the composition of the methane-oxidizing bacterial community was affected by rice-growing stages in the upper soil layer. The abundance of methane-oxidizing bacteria was significantly decreased by elevated [CO2] and LN in both soil layers at the rice MR stage and by ET in the upper soil layer. The ratio of mcrA/pmoA genes correlated with methane emission from ambient and FACE paddy plots at the PI stage. These results indicate that the decrease observed in the abundance of methane-oxidizing bacteria was related to increased methane emission from the paddy field under the elevated [CO2], ET, and LN conditions.

Methanogenic Community Was Stable in Two Contrasting Freshwater Marshes Exposed to Elevated Atmospheric CO2

“…In this study, the difference in the mcr A gene abundance in the three compartments of both marshes was statistically not significant under elevated CO 2 when compared to ambient CO 2 . In a previous paddy soil study, Liu et al (2016) similarly did not observe an effect of elevated CO 2 on the abundance of the methanogenic archaeal community in the bulk soil. In contrast, some studies have reported that elevated CO 2 significantly increased the abundance of methanogenic archaea in rice cultivated soil ( Inubushi et al, 2003 ; Okubo et al, 2015 ) because of the increase in the carbon supply as root exudates with elevated CO 2 ( Bhattacharyya et al, 2013 ).…”

“…Studying a temperate marsh microcosm, Lee et al (2012) found that elevated CO 2 concentrations increased the relative abundance of hydrogenotrophic methanogens. In contrast, other studies did not identify any apparent effect on the methanogen community ( Angel et al, 2012 ; Liu et al, 2016 ). Drigo et al (2008) found that elevated atmospheric CO 2 did not affect the microbial community in the bulk soil, but did near the roots.…”

“…In the present study; however, we did not find a significant effect of elevated CO 2 on the methanogenic community composition in the bulk soil, rhizosphere soil, or roots ( Figure 4 ). The resilience of the methanogenic community to elevated CO 2 may be due to the general robustness of the community against changes in the surrounding environment ( Liu et al, 2012b , 2016 ), or the changes in the organic substrate input and environmental factors were potentially not large enough to change the methanogen community composition ( Angel et al, 2012 ). Likewise, in a 10-year atmospheric CO 2 enrichment experiment, Angel et al (2012) did not observe changes to the methanogenic communities in a waterlogged grassland under elevated CO 2 .…”

Short-Term Response of the Soil Microbial Abundances and Enzyme Activities to Experimental Warming in a Boreal Peatland in Northeast China

“…Liu et al [63] also observed that the abundance of methane-oxidizing bacteria significantly decreased under higher temperature. The decrease observed in the abundance of methane-oxidizing bacteria may be related to increased methane emission under climate warming [74].…”

Topic of Influence, Methane and Microbes

“…The amount of methane released into the atmosphere is tightly controlled by the balance between microbial methane production and oxidation by methane-producing archaea and methane-oxidizing bacteria, respectively. Based on the observation that increased CO 2 levels in the atmosphere promote the production and emission of methane from rice paddies, Liu and colleagues investigated the effects of increased CO 2 levels, elevated soil temperatures, and the absence of nitrogen fertilization on methane-producing and -oxidizing microbial populations in a free-air CO 2 enrichment (FACE) experimental paddy field ( 20 ). Using PCR with denaturing gradient gel electrophoresis (DDGE) and quantitative PCR techniques targeting the genes mcrA and pmoA , which encode key enzymes for methane production and oxidization, they showed that the abundance of methane-producing archaea, detected as mcrA gene abundance, was not affected by increased CO 2 levels and elevated soil temperatures, but by the absence of nitrogen fertilizer, leading to low abundance.…”