Abstract
Relatively little is known about the implications of atmospheric CO2 enrichment for tree responses to biotic disturbances such as folivory. We examined the combined effects of elevated CO2 concentration ([CO2]) and defoliation on growth and physiology of sugar maple (Acer saccharum Marsh.) and trembling aspen (Populus tremuloides Michx.). Seedlings were planted in the ground in eight open-top chambers. Four chambers were ventilated with CO2-enriched air (ambient + 283 micromol mol-1) and four chambers were supplied with ambient air. After 6 weeks of growth, half of the leaf area was removed on a subset of seedlings of each species in each CO2 treatment. We monitored subsequent biomass gain and allocation, along with leaf gas exchange and chemistry. Defoliation did not significantly affect final seedling biomass in either species or CO2 treatment. Growth recovery following defoliation was associated with increased allocation to leaf mass in maple and a slight enhancement of mean photosynthesis in aspen. Elevated [CO2] did not significantly affect aspen growth, and the observed stimulation of maple growth was significant only in mid-season. Correspondingly, simulated responses of whole-tree photosynthesis to elevated [CO2] were constrained by a decrease in photosynthetic capacity in maple, and were partially offset by reductions in specific leaf area and biomass allocation to foliage in aspen. There was a significant interaction between [CO2] and defoliation on only a few of the measured traits. Thus, the data do not support the hypothesis that atmospheric CO2 enrichment will substantially alter tree responses to folivory. However, our findings do provide further indication that regeneration-stage growth rates of certain temperate tree species may respond only moderately to a near doubling of atmospheric [CO2].
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Claims 12
Claim · model-written summary
Defoliation did not significantly affect final sugar maple seedling biomass.
- Taxon
- sugar maple
Acer saccharume1 - Treatment
- Defoliatione0
- Outcome
- final seedling biomasse0
- Direction
- did not significantly affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Defoliation did not significantly affect final seedling biomass in either species or CO2 treatment”
e1“sugar maple (Acer saccharum Marsh.)”
Claim · model-written summary
Defoliation did not significantly affect final trembling aspen seedling biomass.
- Taxon
- trembling aspene1
- Treatment
- Defoliatione0
- Outcome
- final seedling biomasse0
- Direction
- did not significantly affecte0
Not reportedComparator
Verbatim
e0“Defoliation did not significantly affect final seedling biomass in either species or CO2 treatment”
e1“trembling aspen (Populus tremuloides Michx.)”
Claim · model-written summary
Maple growth recovery after defoliation was associated with increased allocation to leaf mass.
Verbatim
e0“Growth recovery following defoliation was associated with increased allocation to leaf mass in maple”
Claim · model-written summary
Aspen growth recovery after defoliation was associated with slightly enhanced mean photosynthesis.
Verbatim
e0“Growth recovery following defoliation was associated with increased allocation to leaf mass in maple and a slight enhancement of mean photosynthesis in aspen”
Claim · model-written summary
Elevated CO2 did not significantly affect aspen growth.
Not reportedComparator
Verbatim
e0“Elevated [CO2] did not significantly affect aspen growth”
Claim · model-written summary
Elevated CO2 stimulated maple growth significantly only at mid-season.
- Taxon
- maplee0
- Treatment
- Elevated [CO2]e1
- Outcome
- maple growthe0
- Direction
- stimulatione0
- Qualifier
- only in mid-seasone0
Not reportedComparator
Verbatim
e0“stimulation of maple growth was significant only in mid-season”
e1“Elevated [CO2] did not significantly affect aspen growth, and the observed stimulation of maple growth”
Claim · model-written summary
Reduced photosynthetic capacity constrained simulated whole-tree photosynthetic responses to elevated CO2 in maple.
Verbatim
e0“simulated responses of whole-tree photosynthesis to elevated [CO2] were constrained by a decrease in photosynthetic capacity in maple”
Claim · model-written summary
Reduced specific leaf area partly offset simulated whole-tree photosynthetic responses to elevated CO2 in aspen.
Verbatim
e0“were partially offset by reductions in specific leaf area and biomass allocation to foliage in aspen”
e1“simulated responses of whole-tree photosynthesis to elevated [CO2]”
Claim · model-written summary
Reduced biomass allocation to foliage partly offset simulated whole-tree photosynthetic responses to elevated CO2 in aspen.
Verbatim
e0“were partially offset by reductions in specific leaf area and biomass allocation to foliage in aspen”
e1“simulated responses of whole-tree photosynthesis to elevated [CO2]”
Claim · model-written summary
Only a few measured traits showed a significant CO2-by-defoliation interaction.
- Taxon
- deciduous broadleaf treest0
- Treatment
- defoliatione0
- Outcome
- interaction between [CO2] and defoliatione0
- Qualifier
- only a few of the measured traitse0
Not reportedDirection
Verbatim
e0“There was a significant interaction between [CO2] and defoliation on only a few of the measured traits”
t0“deciduous broadleaf trees”
Claim · model-written summary
The data do not support substantial alteration of tree responses to folivory by CO2 enrichment.
Verbatim
e0“the data do not support the hypothesis that atmospheric CO2 enrichment will substantially alter tree responses to folivory”
Claim · model-written summary
Regeneration-stage growth rates of some temperate trees may respond only moderately to near-doubled atmospheric CO2.
Verbatim
e0“regeneration-stage growth rates of certain temperate tree species may respond only moderately to a near doubling of atmospheric [CO2]”
The same questions in other papers
pruning · growth · Acer saccharum (sugar maple)Positive and negative results
1 paper in the same direction as this paper · 2 in the opposite direction
- positive
- positive
- negative
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.