Abstract
Stomatal responses to atmospheric change have been well documented through a range of laboratory- and field-based experiments. Increases in atmospheric concentration of CO(2) ([CO(2)]) have been shown to decrease stomatal conductance (g(s)) for a wide range of species under numerous conditions. Less well understood, however, is the extent to which leaf-level responses translate to changes in ecosystem evapotranspiration (ET). Since many changes at the soil, plant, and canopy microclimate levels may feed back on ET, it is not certain that a decrease in g(s) will decrease ET in rain-fed crops. To examine the scaling of the effect of elevated [CO(2)] on g(s) at the leaf to ecosystem ET, soybean (Glycine max) was grown in field conditions under control (approximately 375 micromol CO(2) mol(-1) air) and elevated [CO(2)] (approximately 550 micromol mol(-1)) using free air CO(2) enrichment. ET was determined from the time of canopy closure to crop senescence using a residual energy balance approach over four growing seasons. Elevated [CO(2)] caused ET to decrease between 9% and 16% depending on year and despite large increases in photosynthesis and seed yield. Ecosystem ET was linked with g(s) of the upper canopy leaves when averaged across the growing seasons, such that a 10% decrease in g(s) results in a 8.6% decrease in ET; this relationship was not altered by growth at elevated [CO(2)]. The findings are consistent with model and historical analyses that suggest that, despite system feedbacks, decreased g(s) of upper canopy leaves at elevated [CO(2)] results in decreased transfer of water vapor to the atmosphere.
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Claims 5
Claim · model-written summary
Elevated CO2 decreased ecosystem evapotranspiration by 9–16% across years.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Elevated [CO(2)] caused ET to decrease between 9% and 16% depending on year”
t0“Soybean”
Claim · model-written summary
Elevated CO2 increased photosynthesis.
- Taxon
- Soybean
Glycine maxt0 - Treatment
- Elevation of [CO2]t0
- Outcome
- photosynthesise0
- Direction
- increasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“despite large increases in photosynthesis and seed yield”
t0“Soybean under Open-Air Elevation of [CO2]”
Claim · model-written summary
Elevated CO2 increased seed yield.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- Elevation of [CO2]t0
- Outcome
- seed yielde0
- Direction
- increasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“despite large increases in photosynthesis and seed yield”
t0“Soybean under Open-Air Elevation of [CO2]”
Claim · model-written summary
A 10% decrease in upper-canopy stomatal conductance corresponded to an 8.6% ET decrease.
- Taxon
- SoybeanGlycine maxt0
- Organ / stage
- Stomatal Conductancet0
- Outcome
- ETe0
- Direction
- decreasee0
- Value
- 8.6%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a 10% decrease in g(s) results in a 8.6% decrease in ET”
t0“Stomatal Conductance of Soybean”
Claim · model-written summary
Elevated CO2 did not change the stomatal-conductance and ET relationship.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- elevated [CO(2)]e0
- Outcome
- this relationshipe0
- Direction
- not alterede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this relationship was not altered by growth at elevated [CO(2)]”
t0“Soybean”
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