Abstract
An elevated atmospheric CO2 concentration ([CO2 ]) can reduce stomatal conductance of leaves for most plant species, including rice (Oryza sativa L.). However, few studies have quantified seasonal changes in the effects of elevated [CO2 ] on canopy evapotranspiration, which integrates the response of stomatal conductance of individual leaves with other responses, such as leaf area expansion, changes in leaf surface temperature, and changes in developmental stages, in field conditions. We conducted a field experiment to measure seasonal changes in stomatal conductance of the uppermost leaves and in the evapotranspiration, transpiration, and evaporation rates using a lysimeter method. The study was conducted for flooded rice under open-air CO2 elevation. Stomatal conductance decreased by 27% under elevated [CO2 ], averaged throughout the growing season, and evapotranspiration decreased by an average of 5% during the same period. The decrease in daily evapotranspiration caused by elevated [CO2 ] was more significantly correlated with air temperature and leaf area index (LAI) rather than with other parameters of solar radiation, days after transplanting, vapor-pressure deficit and FAO reference evapotranspiration. This indicates that higher air temperatures, within the range from 16 to 27 °C, and a larger LAI, within the range from 0 to 4 m(2) m(-2) , can increase the magnitude of the decrease in evapotranspiration rate caused by elevated [CO2 ]. The crop coefficient (i.e. the evapotranspiration rate divided by the FAO reference evapotranspiration rate) was 1.24 at ambient [CO2 ] and 1.17 at elevated [CO2 ]. This study provides the first direct measurement of the effects of elevated [CO2 ] on rice canopy evapotranspiration under open-air conditions using the lysimeter method, and the results will improve future predictions of water use in rice fields.
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Claims 7
Claim · model-written summary
Elevated CO2 decreased rice stomatal conductance by 27% over the season.
- Taxon
- rice
Oryza sativat0 - Treatment
- elevated [CO2 ]e0
- Outcome
- Stomatal conductancee0
- Direction
- decreasede0
- Value
- 27%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Stomatal conductance decreased by 27% under elevated [CO2 ], averaged throughout the growing season”
t0“rice”
Claim · model-written summary
Elevated CO2 decreased evapotranspiration by 5% on average.
- Taxon
- riceOryza sativat0
- Treatment
- open-air CO2 elevatione1
- Outcome
- evapotranspiratione0
- Direction
- decreasede0
- Value
- 5%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“evapotranspiration decreased by an average of 5% during the same period”
e1“under open-air CO2 elevation”
t0“rice”
Claim · model-written summary
The decrease in daily evapotranspiration correlated more strongly with air temperature and leaf area index than other listed parameters.
- Taxon
- riceOryza sativat0
- Outcome
- decrease in daily evapotranspiratione0
- Qualifier
- air temperature and leaf area index (LAI)e0
- Comparator
- solar radiation, days after transplanting, vapor-pressure deficit and FAO reference evapotranspiratione0
Not reportedSettingDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The decrease in daily evapotranspiration caused by elevated [CO2 ] was more significantly correlated with air temperature and leaf area index (LAI) rather than with other parameters of solar radiation, days after transplanting, vapor-pressure deficit and FAO reference evapotranspiration”
t0“rice”
Claim · model-written summary
Higher air temperatures increased the magnitude of the CO2-related evapotranspiration decrease.
- Taxon
- riceOryza sativat0
- Treatment
- elevated [CO2 ]e0
- Outcome
- magnitude of the decrease in evapotranspiration ratee0
- Direction
- increasee0
- Qualifier
- within the range from 16 to 27 °Ce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher air temperatures, within the range from 16 to 27 °C, and a larger LAI, within the range from 0 to 4 m(2) m(-2) , can increase the magnitude of the decrease in evapotranspiration rate caused by elevated [CO2 ]”
t0“rice”
Claim · model-written summary
Larger LAI increased the magnitude of the CO2-related evapotranspiration decrease.
- Taxon
- riceOryza sativat0
- Treatment
- elevated [CO2 ]e0
- Outcome
- magnitude of the decrease in evapotranspiration ratee0
- Direction
- increasee0
- Qualifier
- within the range from 0 to 4 m(2) m(-2)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a larger LAI, within the range from 0 to 4 m(2) m(-2) , can increase the magnitude of the decrease in evapotranspiration rate caused by elevated [CO2 ]”
t0“rice”
Claim · model-written summary
Crop coefficient at ambient CO2 was 1.24.
- Taxon
- riceOryza sativat0
- Treatment
- ambient [CO2 ]e0
- Outcome
- crop coefficiente0
- Value
- 1.24e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The crop coefficient (i.e. the evapotranspiration rate divided by the FAO reference evapotranspiration rate) was 1.24 at ambient [CO2 ]”
t0“rice”
Claim · model-written summary
Crop coefficient at elevated CO2 was 1.17.
- Taxon
- riceOryza sativat0
- Treatment
- elevated [CO2 ]e0
- Outcome
- crop coefficiente1
- Value
- 1.17e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“1.17 at elevated [CO2 ]”
e1“The crop coefficient (i.e. the evapotranspiration rate divided by the FAO reference evapotranspiration rate) was 1.24 at ambient [CO2 ] and 1.17 at elevated [CO2 ]”
t0“rice”