Abstract
The rising levels of atmospheric CO2 are likely to increase biomass production of C3 species in both natural and managed ecosystems because photosynthetic rates will be higher. The greatest absolute increase in productivity will occur when nitrogen and phosphorus availability in the soil is high. Low nitrogen does not preclude a growth response to high CO2, whereas some C3 species fail to respond to high CO2 when phosphorus is low, possibly because insufficient phosphorus is available to maintain maximum photosynthetic activity at high CO2. C3 plants response to high CO2 because the flux of carbon through the photoreductive cycle is increased and photorespiration is suppressed. This change in metabolism appears to alter the foliar nutrient concentration required to promote maximum productivity (critical concentration). Higher phosphorus concentrations are needed at elevated CO2, whereas the nitrogen requirement is reduced by CO2 enrichment. Since critical concentrations are used to evaluate nutrient status of crop and forest species and to manage fertiliser programs, they will need reassessing as the atmospheric CO2 concentration rises. Another consequence of the altered nutrient requirement at high CO2 is that the nitrogen concentrations of foliage, roots and grain are consistently lower in plants grown at elevated CO2, irrespective of availability of nitrogen in the soil. In natural ecosystems, the lower nitrogen to carbon ratio of the litter may alter rates of nutrient cycling. For farmers, the rising CO2 concentrations could cause reductions in grain nitrogen, and therefore protein content. This could have important implications for baking quality of hard wheats as well as affecting the nutrient value of grain such as rice.
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Claims 8
Claim · model-written summary
Elevated CO2 is expected to increase biomass production of C3 species through higher photosynthesis.
Verbatim
e0“rising levels of atmospheric CO2 are likely to increase biomass production of C3 species in both natural and managed ecosystems because photosynthetic rates will be higher”
Claim · model-written summary
The greatest productivity increase is expected at high soil nitrogen and phosphorus availability.
Verbatim
e0“The greatest absolute increase in productivity will occur when nitrogen and phosphorus availability in the soil is high.”
t0“Plant Nutrition”
e2“biomass production of C3 species in both natural and managed ecosystems”
Claim · model-written summary
Low nitrogen does not prevent a growth response to high CO2.
Verbatim
e0“Low nitrogen does not preclude a growth response to high CO2”
t0“Plant Nutrition”
e2“biomass production of C3 species in both natural and managed ecosystems”
Claim · model-written summary
Some C3 species fail to respond to high CO2 when phosphorus is low.
Verbatim
e0“some C3 species fail to respond to high CO2 when phosphorus is low”
Claim · model-written summary
Higher phosphorus concentrations are required at elevated CO2.
Verbatim
e0“Higher phosphorus concentrations are needed at elevated CO2”
t0“Plant Nutrition”
Claim · model-written summary
CO2 enrichment reduces nitrogen requirement.
Verbatim
e0“the nitrogen requirement is reduced by CO2 enrichment”
t0“Plant Nutrition”
Claim · model-written summary
Foliar, root and grain nitrogen concentrations are lower under elevated CO2 regardless of soil nitrogen availability.
- Taxon
- plantsViridiplantaee0
- Treatment
- elevated CO2e0
- Outcome
- nitrogen concentrations of foliage, roots and graine0
- Direction
- lowere0
Not reportedComparator
Verbatim
e0“the nitrogen concentrations of foliage, roots and grain are consistently lower in plants grown at elevated CO2, irrespective of availability of nitrogen in the soil”
Claim · model-written summary
Critical nutrient concentrations should be reassessed as atmospheric CO2 rises.
Verbatim
e0“they will need reassessing as the atmospheric CO2 concentration rises”
t0“Plant Nutrition”
e2“critical concentrations are used to evaluate nutrient status of crop and forest species”