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Responses of Methanogenic and Methanotrophic Communities to Elevated Atmospheric CO 2 and Temperature in a Paddy Field

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ABSTRACT

Although climate change is predicted to affect methane (CH4) emissions in paddy soil, the dynamics of methanogens and methanotrophs in paddy fields under climate change have not yet been fully investigated. To address this issue, a multifactor climate change experiment was conducted in a Chinese paddy field using the following experimental treatments: (1) enrichment of atmospheric CO2 concentrations (500 ppm, CE), (2) canopy air warming (2°C above the ambient, WA), (3) combined CO2 enrichment and warming (CW), and (4) ambient conditions (CK). We analyzed the abundance of methanogens and methanotrophs, community structures, CH4 production and oxidation potentials, in situ CH4 emissions using real-time PCR, T-RFLP, and clone library techniques, as well as biochemical assays. Compared to the control under CE and CW treatments, CH4 production potential, methanogenic gene abundance and soil microbial biomass carbon significantly increased; the methanogenic community, however, remained stable. The canopy air warming treatment only had an effect on CH4 oxidation potential at the ripening stage. Phylogenic analysis indicated that methanogens in the rhizosphere were dominated by Methanosarcina, Methanocellales, Methanobacteriales, and Methanomicrobiales, while methanotrophic sequences were classified as Methylococcus, Methylocaldum, Methylomonas, Methylosarcina (Type I) and Methylocystis (Type II). However, the relative abundance of Methylococcus (Type I) decreased under CE and CW treatments and the relative abundance of Methylocystis (Type II) increased. The in situ CH4 fluxes indicated similar seasonal patterns between treatments; both CE and CW increased CH4 emissions. In conclusion results suggest that methanogens and methanotrophs respond differently to elevated atmospheric CO2 concentrations and warming, thus adding insights into the effects of simulated global climate change on CH4 emissions in paddy fields.

No MeSH data available.


Changes in the mcrA (A) and pmoA(B) gene copy numbers for methanogens and methanotrophs in the studied soils under simulated climate change treatments. Different letters above the columns indicate significant differences among treatments within a single growth stage (p < 0.05).
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Figure 1: Changes in the mcrA (A) and pmoA(B) gene copy numbers for methanogens and methanotrophs in the studied soils under simulated climate change treatments. Different letters above the columns indicate significant differences among treatments within a single growth stage (p < 0.05).

Mentions: Gene abundance data showed that the abundances of mcrA and pmoA genes generally increased with rice growth development, the highest values being attained at the ripening stage (Figure 1). The abundance of mcrA genes under all treatments ranged from 9.13 × 108 (WA, tillering) to 7.73 × 109 (CE, ripening) copies g-1 dw. These results were higher than the abundance of pmoA genes, ranging from 1.31 × 108 (CK, tillering) to 4.55 × 108 (CW, ripening) copies g-1 dw. Repeated measures ANOVA showed that the effects of elevated CO2 and elevated CO2 combined with warming were significant (p < 0.05) on the abundance of mcrA genes, but not on the abundance of pmoA genes (Table 2). In this study, no significant changes in the abundance of mcrA and pmoA genes associated with climate change treatments were observed at the tillering stage. However, the abundance of mcrA genes significantly increased under CE and CW treatments at the heading and ripening stages. Compared to CK, the mean abundance of mcrA genes increased by 63% (CE) and 82% (CW) at the heading stage and 98% (CE) and 78% (CW) at the ripening stage, respectively. In contrast, the pmoA gene copy numbers were more stable without significant changes among the climate change treatments at all three growth stages.


Responses of Methanogenic and Methanotrophic Communities to Elevated Atmospheric CO 2 and Temperature in a Paddy Field
Changes in the mcrA (A) and pmoA(B) gene copy numbers for methanogens and methanotrophs in the studied soils under simulated climate change treatments. Different letters above the columns indicate significant differences among treatments within a single growth stage (p < 0.05).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121223&req=5

Figure 1: Changes in the mcrA (A) and pmoA(B) gene copy numbers for methanogens and methanotrophs in the studied soils under simulated climate change treatments. Different letters above the columns indicate significant differences among treatments within a single growth stage (p < 0.05).
Mentions: Gene abundance data showed that the abundances of mcrA and pmoA genes generally increased with rice growth development, the highest values being attained at the ripening stage (Figure 1). The abundance of mcrA genes under all treatments ranged from 9.13 × 108 (WA, tillering) to 7.73 × 109 (CE, ripening) copies g-1 dw. These results were higher than the abundance of pmoA genes, ranging from 1.31 × 108 (CK, tillering) to 4.55 × 108 (CW, ripening) copies g-1 dw. Repeated measures ANOVA showed that the effects of elevated CO2 and elevated CO2 combined with warming were significant (p < 0.05) on the abundance of mcrA genes, but not on the abundance of pmoA genes (Table 2). In this study, no significant changes in the abundance of mcrA and pmoA genes associated with climate change treatments were observed at the tillering stage. However, the abundance of mcrA genes significantly increased under CE and CW treatments at the heading and ripening stages. Compared to CK, the mean abundance of mcrA genes increased by 63% (CE) and 82% (CW) at the heading stage and 98% (CE) and 78% (CW) at the ripening stage, respectively. In contrast, the pmoA gene copy numbers were more stable without significant changes among the climate change treatments at all three growth stages.

View Article: PubMed Central - PubMed

ABSTRACT

Although climate change is predicted to affect methane (CH4) emissions in paddy soil, the dynamics of methanogens and methanotrophs in paddy fields under climate change have not yet been fully investigated. To address this issue, a multifactor climate change experiment was conducted in a Chinese paddy field using the following experimental treatments: (1) enrichment of atmospheric CO2 concentrations (500 ppm, CE), (2) canopy air warming (2&deg;C above the ambient, WA), (3) combined CO2 enrichment and warming (CW), and (4) ambient conditions (CK). We analyzed the abundance of methanogens and methanotrophs, community structures, CH4 production and oxidation potentials, in situ CH4 emissions using real-time PCR, T-RFLP, and clone library techniques, as well as biochemical assays. Compared to the control under CE and CW treatments, CH4 production potential, methanogenic gene abundance and soil microbial biomass carbon significantly increased; the methanogenic community, however, remained stable. The canopy air warming treatment only had an effect on CH4 oxidation potential at the ripening stage. Phylogenic analysis indicated that methanogens in the rhizosphere were dominated by Methanosarcina, Methanocellales, Methanobacteriales, and Methanomicrobiales, while methanotrophic sequences were classified as Methylococcus, Methylocaldum, Methylomonas, Methylosarcina (Type I) and Methylocystis (Type II). However, the relative abundance of Methylococcus (Type I) decreased under CE and CW treatments and the relative abundance of Methylocystis (Type II) increased. The in situ CH4 fluxes indicated similar seasonal patterns between treatments; both CE and CW increased CH4 emissions. In conclusion results suggest that methanogens and methanotrophs respond differently to elevated atmospheric CO2 concentrations and warming, thus adding insights into the effects of simulated global climate change on CH4 emissions in paddy fields.

No MeSH data available.