Abstract
Abstract Methane (CH 4 ) is a particularly potent greenhouse gas with a radiative forcing 23 times that of CO 2 on a per mass basis. Flooded rice paddies are a major source of CH 4 emissions to the Earth's atmosphere. A free‐air CO 2 enrichment (FACE) experiment was conducted to evaluate changes in crop productivity and the crop ecosystem under enriched CO 2 conditions during three rice growth seasons from 1998 to 2000 in a rice paddy at Shizukuishi, Iwate, Japan. To understand the influence of elevated atmospheric CO 2 concentrations on CH 4 emission, we measured methane flux from FACE rice fields and rice fields with ambient levels of CO 2 during the 1999 and 2000 growing seasons. Methane production and oxidation potentials of soil samples collected when the rice was at the tillering and flowering stages in 2000 were measured in the laboratory by the anaerobic incubation and alternative propylene substrates methods, respectively. The average tiller number and root dry biomass were clearly larger in the plots with elevated CO 2 during all rice growth stages. No difference in methane oxidation potential between FACE and ambient treatments was found, but the methane production potential of soils during the flowering stage was significantly greater under FACE than under ambient conditions. When free‐air CO 2 was enriched to 550 ppmv, the CH 4 emissions from the rice paddy field increased significantly, by 38% in 1999 and 51% in 2000. The increased CH 4 emissions were attributed to accelerated CH 4 production potential as a result of more root exudates and root autolysis products and to increased plant‐mediated CH 4 emissions because of the larger rice tiller numbers under FACE conditions.
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Claims 8
Claim · model-written summary
Elevated CO2 increased rice tiller number.
- Taxon
- rice
Oryza sativat0 - Treatment
- elevated CO 2e0
- Outcome
- average tiller numbere0
- Direction
- largere0
- Qualifier
- during all rice growth stagese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The average tiller number and root dry biomass were clearly larger in the plots with elevated CO 2 during all rice growth stages”
t0“rice”
Claim · model-written summary
Elevated CO2 increased root dry biomass.
- Taxon
- riceOryza sativae0
- Treatment
- elevated CO 2e0
- Outcome
- root dry biomasse0
- Direction
- largere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The average tiller number and root dry biomass were clearly larger in the plots with elevated CO 2 during all rice growth stages”
Claim · model-written summary
Methane oxidation potential did not differ between FACE and ambient conditions.
- Taxon
- riceOryza sativat0
- Treatment
- FACEe0
- Outcome
- methane oxidation potentiale0
- Direction
- No differencee0
- Comparator
- ambient treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“No difference in methane oxidation potential between FACE and ambient treatments was found”
t0“rice”
Claim · model-written summary
Flowering-stage soil methane production potential was significantly greater under FACE.
- Taxon
- riceOryza sativat0
- Organ / stage
- flowering stagee0
- Treatment
- FACEe0
- Outcome
- methane production potential of soilse0
- Direction
- greatere0
- Comparator
- ambient conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the methane production potential of soils during the flowering stage was significantly greater under FACE than under ambient conditions”
t0“rice”
Claim · model-written summary
Elevated CO2 raised paddy methane emissions by 38% in 1999.
- Taxon
- riceOryza sativae0
- Treatment
- free‐air CO 2 was enriched to 550 ppmve0
- Outcome
- CH 4 emissions from the rice paddy fielde0
- Direction
- increasede0
- Value
- 38%e0
- Qualifier
- in 1999e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When free‐air CO 2 was enriched to 550 ppmv, the CH 4 emissions from the rice paddy field increased significantly, by 38% in 1999 and 51% in 2000”
Claim · model-written summary
Elevated CO2 raised paddy methane emissions by 51% in 2000.
- Taxon
- riceOryza sativae0
- Treatment
- free‐air CO 2 was enriched to 550 ppmve0
- Outcome
- CH 4 emissions from the rice paddy fielde0
- Direction
- increasede0
- Value
- 51%e0
- Qualifier
- in 2000e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When free‐air CO 2 was enriched to 550 ppmv, the CH 4 emissions from the rice paddy field increased significantly, by 38% in 1999 and 51% in 2000”
Claim · model-written summary
Authors attributed increased methane to production potential driven by root exudates and autolysis products.
- Taxon
- riceOryza sativat0
- Outcome
- increased CH 4 emissionse0
- Qualifier
- accelerated CH 4 production potential as a result of more root exudates and root autolysis productse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The increased CH 4 emissions were attributed to accelerated CH 4 production potential as a result of more root exudates and root autolysis products”
t0“rice”
Claim · model-written summary
Authors attributed methane increase partly to greater plant-mediated emissions from more rice tillers.
- Taxon
- riceOryza sativae0
- Organ / stage
- tillere0
- Outcome
- plant‐mediated CH 4 emissionse0
- Qualifier
- because of the larger rice tiller numbers under FACE conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased plant‐mediated CH 4 emissions because of the larger rice tiller numbers under FACE conditions”
The same questions in other papers
co2 · molecular: metabolites · Oryza sativa (rice)Results differ
19 papers in the same direction as this paper · 23 in the opposite direction
- no effect
- positive
- positive
39 papers more in this group
See all 43 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.