Abstract
Elevated atmospheric carbon dioxide (eCO2) greatly impacts greenhouse gas (GHG) emissions of CH4 and N2O from rice fields. Although eCO2 generally stimulates GHG emissions in the short term (<5 years) experiments, the responses to long-term (≥10 years) eCO2 remain poorly known. Here we show, through a series of experiments and meta-analysis, that the eCO2 does not necessarily increase CH4 and N2O emissions from rice paddies. In an experiment of free-air CO2 enrichment for 13–15 years, CH4 and N2O emissions were decreased by 11–54% and 33–54%, respectively. The decline of CH4 emissions was related to the reduction of CH4 production and enhancement of CH4 oxidation via raising soil Eh and soil-water interface [O2] under eCO2. Moreover, the eCO2 significantly decreased NH4+-N content, suggesting a reduction of soil nitrification and thereby N2O emissions. A meta-analysis showed that CH4 and N2O emissions were stimulated under short-term eCO2 while reduced under long-term eCO2. The eCO2-induced increase in yield and biomass and the ratio of mcrA genes/pmoA genes declined with eCO2 duration, indicating an eCO2-stimulation of methanogenesis lower than that of methanotrophy over time by fewer increased substrates. Upscaling the results of meta-analysis, the eCO2-induced global paddy CH4 and N2O emissions shifted from an increase (+0.17 Pg CO2-eq year−1) in the short term into a decrease (−0.11 Pg CO2-eq year−1) in the long term. Our findings suggest that the effect of eCO2 on GHG emissions changes over time, and this should be considered in future climate change research.
Original language | English |
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Article number | 152363 |
Number of pages | 11 |
Journal | Science of the Total Environment |
Volume | 810 |
Early online date | 13 Dec 2021 |
DOIs | |
Publication status | Published - 1 Mar 2022 |
Bibliographical note
Funding Information:This work was financially supported by the National Key Research and Development Program of China ( 2017YFD0300105 ), the National Natural Science Foundation of China ( 41571232 , 41877325 , 41571130062 ), and the Youth Innovation Promotion Association of Chinese Academy of Sciences ( 2018349 ).
Keywords
- Elevated CO duration
- Free-air CO enrichment
- GHG emissions
- Meta-analysis
- Rice fields
- Yield