Abstract
In order to understand the implications of changes in global CO 2 concentrations and temperature for the growth and fitness of individual plants, performance must be investigated in relation to the performance of other plants within a population. In this study we examined patterns of recruitment, mortality, and size structure of monospecific stands in response to ambient (400 μL/L) and elevated CO 2 concentrations (700 μL/L) across three temperature regimes; 18°, 28°, and 38°C. We created experimental populations of two annual plants that differ in their photosynthetic pathway and water use patterns: Abutilon theophrasti (C 3 ) and Amaranthus retroflexus (C 4 ). The effects of CO 2 , temperature, and their interactions on population structure were complex and species dependent. For both species increasing temperature resulted in higher germination and faster initial growth rates. These initial temperature responses increased the intensity and role of competition in determining stand size and structure. Postemergence responses to elevated CO 2 differed markedly between the two species. For Abutilon, the C 3 species, self—thinning and the mean biomass of the survivors increased under elevated CO 2 . For Amaranthus, survivorship, but not growth, increased under elevated CO 2 conditions. We attribute differences in response between species not only to photosynthetic pathway, but also to differences in the onset of competition mediated through differences in plant form and in resource uptake and deployment. The patterns of stand development in response to CO 2 and temperature suggest that the effects of changing CO 2 and temperature may be understood within mechanistically based models of resource use. Temperature regulates the rate of resource use and the onset of interference among plants, while CO 2 functions both as a resource and a resource regulator. Although mortality was concentrated later in stand development for Abutilon than Amaranthus, overall patterns of stand size and structure were similar for both species; mortality and size inequalities increased with increasing temperature and CO 2 . Because size is often correlated with fecundity, and increase in size hierarchies in response to elevated CO 2 , in conjunction with a decrease in survivorship, may result in a smaller effective population size. Our ability to predict changes in effective population size due to changing size due to changing size hierarchies alone, however, should also consider developmental shifts in response to elevated CO 2 that may result in, as in this study, a decrease in the minimum size at the onset of flowering.
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Claims 6
Claim · model-written summary
Under elevated CO2 the self-thinning and mean biomass of surviving Abutilon theophrasti increased relative to ambient CO2.
- Taxon
- Abutilon theophrasti
Abutilon theophrastie3 - Treatment
- elevated CO 2e1
- Outcome
- self—thinning and the mean biomass of the survivorse1
- Direction
- increasede1
- Comparator
- ambient (400 μL/L)e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“For Abutilon, the C 3 species, self—thinning and the mean biomass of the survivors increased under elevated CO 2”
e2“ambient (400 μL/L) and elevated CO 2 concentrations (700 μL/L)”
e3“We created experimental populations of two annual plants that differ in their photosynthetic pathway and water use patterns: Abutilon theophrasti (C 3 ) and Amaranthus retroflexus (C 4 )”
Claim · model-written summary
Under elevated CO2 survivorship of Amaranthus retroflexus increased.
- Taxon
- Amaranthus retroflexus
Amaranthus retroflexuse3 - Treatment
- elevated CO 2e4
- Outcome
- survivorshipe4
- Direction
- increasede4
- Comparator
- ambient (400 μL/L)e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“ambient (400 μL/L) and elevated CO 2 concentrations (700 μL/L)”
e3“We created experimental populations of two annual plants that differ in their photosynthetic pathway and water use patterns: Abutilon theophrasti (C 3 ) and Amaranthus retroflexus (C 4 )”
e4“For Amaranthus, survivorship, but not growth, increased under elevated CO 2 conditions”
Claim · model-written summary
Under elevated CO2 growth of Amaranthus retroflexus did not change.
- Taxon
- Amaranthus retroflexusAmaranthus retroflexuse3
- Treatment
- elevated CO 2e4
- Outcome
- growthe4
- Direction
- no_changeinferrede4
- Comparator
- ambient (400 μL/L)e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“ambient (400 μL/L) and elevated CO 2 concentrations (700 μL/L)”
e3“We created experimental populations of two annual plants that differ in their photosynthetic pathway and water use patterns: Abutilon theophrasti (C 3 ) and Amaranthus retroflexus (C 4 )”
e4“For Amaranthus, survivorship, but not growth, increased under elevated CO 2 conditions”
Claim · model-written summary
Increasing temperature resulted in higher germination in both annual species.
Not reportedComparator
Verbatim
e3“We created experimental populations of two annual plants that differ in their photosynthetic pathway and water use patterns: Abutilon theophrasti (C 3 ) and Amaranthus retroflexus (C 4 )”
e5“For both species increasing temperature resulted in higher germination and faster initial growth rates”
Claim · model-written summary
Increasing temperature resulted in faster initial growth rates in both annual species.
- Taxon
- two annual plantse3
- Treatment
- increasing temperaturee5
- Outcome
- initial growth ratese5
- Direction
- fastere5
Not reportedComparator
Verbatim
e3“We created experimental populations of two annual plants that differ in their photosynthetic pathway and water use patterns: Abutilon theophrasti (C 3 ) and Amaranthus retroflexus (C 4 )”
e5“For both species increasing temperature resulted in higher germination and faster initial growth rates”
Claim · model-written summary
Mortality and size inequalities increased with increasing temperature and CO2.
- Taxon
- two annual plantse3
- Treatment
- increasing temperature and CO 2e6
- Outcome
- mortality and size inequalitiese6
- Direction
- increasede6
Not reportedComparator
Verbatim
e3“We created experimental populations of two annual plants that differ in their photosynthetic pathway and water use patterns: Abutilon theophrasti (C 3 ) and Amaranthus retroflexus (C 4 )”
e6“mortality and size inequalities increased with increasing temperature and CO 2”
The same questions in other papers
co2 · growth · Amaranthus retroflexus (redroot amaranth)Positive and negative results
4 papers in the same direction as this paper · 2 in the opposite direction
- positive
- positive
- no effect
3 papers more in this group
See all 7 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.