Abstract
The long-term response of leaf photosynthesis to rising CO2 concentrations [CO2] depends on biochemical and morphological feedbacks. Additionally, responses to elevated [CO2] might depend on the nutrient availability and the light environment, affecting the net carbon uptake of a forest stand. After 6 yr of exposure to free-air CO2 enrichment (EUROFACE) during two rotation cycles (with fertilization during the second cycle), profiles of light, leaf characteristics and photosynthetic parameters were measured in the closed canopy of a poplar (Populus) short-rotation coppice. Net photosynthetic rate (A(growth)) was 49% higher in poplars grown in elevated [CO2], independently of the canopy position. Jmax significantly increased (15%), whereas leaf carboxylation capacity (Vcmax), leaf nitrogen (N(a)) and chlorophyll (Chl(a)) were unaffected in elevated [CO2]. Leaf mass per unit area (LMA) increased in the upper canopy. Fertilization created more leaves in the top of the crown. These results suggest that the photosynthetic stimulation by elevated [CO2] in a closed-canopy poplar coppice might be sustained in the long term. The absence of any down-regulation, given a sufficient sink capacity and nutrient availability, provides more carbon for growth and storage in this bioenergy plantation.
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Claims 7
Claim · model-written summary
Elevated CO2 raised net photosynthetic rate by 49% throughout the poplar canopy.
- Treatment
- elevated [CO2]e0
- Outcome
- Net photosynthetic ratee0
- Direction
- highere0
- Value
- 49%e0
- Qualifier
- independently of the canopy positione0
PopulusNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Net photosynthetic rate (A(growth)) was 49% higher in poplars grown in elevated [CO2], independently of the canopy position.”
Claim · model-written summary
Elevated CO2 significantly increased Jmax by 15%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Jmax significantly increased (15%), whereas leaf carboxylation capacity (Vcmax), leaf nitrogen (N(a)) and chlorophyll (Chl(a)) were unaffected in elevated [CO2].”
t0“Populus”
Claim · model-written summary
Elevated CO2 did not affect leaf carboxylation capacity, leaf nitrogen, or chlorophyll.
- Treatment
- elevated [CO2]e0
- Outcome
- leaf carboxylation capacity (Vcmax), leaf nitrogen (N(a)) and chlorophyll (Chl(a))e0
- Direction
- unaffectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leaf carboxylation capacity (Vcmax), leaf nitrogen (N(a)) and chlorophyll (Chl(a)) were unaffected in elevated [CO2]”
t0“Populus”
Claim · model-written summary
Leaf mass per unit area increased in the upper canopy.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf mass per unit area (LMA) increased in the upper canopy.”
t0“Populus”
Claim · model-written summary
Fertilization produced more leaves at the top of the poplar crown.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Fertilization created more leaves in the top of the crown.”
t0“Populus”
Claim · model-written summary
The authors infer that photosynthetic stimulation by elevated CO2 may persist long term in closed-canopy poplar coppice.
- Treatment
- elevated [CO2]e0
- Outcome
- photosynthetic stimulatione0
- Qualifier
- might be sustained in the long terme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthetic stimulation by elevated [CO2] in a closed-canopy poplar coppice might be sustained in the long term”
Claim · model-written summary
The authors infer that absence of down-regulation, with sufficient sink capacity and nutrients, provides more carbon for growth and storage.
- Outcome
- carbon for growth and storagee0
- Direction
- moree0
- Qualifier
- given a sufficient sink capacity and nutrient availabilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The absence of any down-regulation, given a sufficient sink capacity and nutrient availability, provides more carbon for growth and storage in this bioenergy plantation.”
t0“Populus”
The same questions in other papers
fertilization · growth · Populus (poplar)Results differ
35 papers in the same direction as this paper · 9 in the opposite direction · 1 reporting no difference from an alternative
- no effect
- no effect
- negative
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See all 46 papers →co2 · physiology: photosynthesis · Populus (poplar)Positive and negative results
9 papers in the same direction as this paper · 1 in the opposite direction
- positive
- positive
- negative
7 papers more in this group
See all 11 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.