Abstract
Ozone effects on plant species mixtures could depend on the characteristics of the species involved, their mixing ratio, or on environmental conditions. Predicting long‐term effects on the dynamics of plant communities requires an understanding of the interactions involved. The present experiment was designed to determine the effects of ozone on grassland species in relation to mixing ratio and soil water content (irrigation) using binary mixtures. The grass Trisetum flavescens was grown in potted replacement‐series mixtures with Centaurea jacea (Experiment A) or Trifolium pratense (Experiment B). The plants were exposed to three concentrations of ozone in open‐top chambers in two irrigation treatments. Total above‐ground dry weight over three growth periods was measured. The competitive ability of T. flavescens was expressed as the competitive ratio ( CR T ). In Experiment B, total above‐ground dry weight was reduced by elevated ozone and by reduced soil moisture, and significant interactions were found for ozone × irrigation and ozone × ratio. In Experiment A these effects were not significant. Under well watered conditions, CR T tended to be reduced by elevated ozone in Experiment A, but increased significantly in Experiment B, indicating the importance of the competing species in modifying the ozone effect on T. flavescens . In both experiments reduced irrigation decreased the magnitude of ozone effects on biomass production, which could be related to observed reductions in specific leaf conductance. The results suggest that under well watered conditions the effect of elevated ozone on the competitive balance between species depends on the species mixture, but that the mixing ratio is less important.
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Claims 8
Claim · model-written summary
Elevated ozone reduced aboveground dry weight in the Trisetum–Trifolium mixture.
- Taxon
- Trifolium pratense
Trifolium pratensee1 - Treatment
- elevated ozonee0
- Outcome
- total above‐ground dry weighte0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In Experiment B, total above‐ground dry weight was reduced by elevated ozone”
e1“Trifolium pratense (Experiment B)”
Claim · model-written summary
Reduced soil moisture reduced aboveground dry weight in the Trisetum–Trifolium mixture.
- Taxon
- Trifolium pratenseTrifolium pratensee1
- Treatment
- reduced soil moisturee0
- Outcome
- total above‐ground dry weighte0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In Experiment B, total above‐ground dry weight was reduced by elevated ozone and by reduced soil moisture”
e1“Trifolium pratense (Experiment B)”
Claim · model-written summary
Ozone interacted significantly with irrigation and mixture ratio in Experiment B.
- Taxon
- Trifolium pratenseTrifolium pratensee1
- Treatment
- ozonee0
- Outcome
- ozone × irrigation and ozone × ratioe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“significant interactions were found for ozone × irrigation and ozone × ratio”
e1“Trifolium pratense (Experiment B)”
Claim · model-written summary
The corresponding ozone, irrigation and ratio effects were not significant in the Trisetum–Centaurea mixture.
- Taxon
- Centaurea jacea
Centaurea jaceae1 - Outcome
- these effectse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In Experiment A these effects were not significant”
e1“Centaurea jacea (Experiment A)”
Claim · model-written summary
Under well-watered conditions elevated ozone tended to reduce Trisetum competitive ratio with Centaurea.
- Taxon
- T. flavescens
Trisetum flavescense2 - Treatment
- elevated ozonee0
- Interactor
- Centaurea jaceaCentaurea jaceae1other
- Outcome
- CR Te0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under well watered conditions, CR T tended to be reduced by elevated ozone in Experiment A”
e1“Centaurea jacea (Experiment A)”
e2“The competitive ability of T. flavescens was expressed as the competitive ratio ( CR T )”
Claim · model-written summary
Under well-watered conditions elevated ozone significantly increased Trisetum competitive ratio with Trifolium.
- Taxon
- T. flavescensTrisetum flavescense2
- Treatment
- elevated ozonee0
- Interactor
- Trifolium pratenseTrifolium pratensee1other
- Outcome
- CR Te0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under well watered conditions, CR T tended to be reduced by elevated ozone in Experiment A, but increased significantly in Experiment B”
e1“Trifolium pratense (Experiment B)”
e2“The competitive ability of T. flavescens was expressed as the competitive ratio ( CR T )”
Claim · model-written summary
Reduced irrigation decreased the size of ozone effects on biomass in both mixtures.
- Treatment
- reduced irrigatione0
- Outcome
- magnitude of ozone effects on biomass productione0
- Direction
- decreasede0
Not reportedTaxonComparator
Verbatim
e0“In both experiments reduced irrigation decreased the magnitude of ozone effects on biomass production”
Claim · model-written summary
Reduced specific leaf conductance may explain the smaller ozone biomass effect under reduced irrigation.
- Outcome
- magnitude of ozone effects on biomass productione0
- Qualifier
- observed reductions in specific leaf conductancee0
Not reportedTaxon
Verbatim
e0“reduced irrigation decreased the magnitude of ozone effects on biomass production, which could be related to observed reductions in specific leaf conductance”
The same questions in other papers
soil water · growth · Trifolium pratense (red clover)Positive and negative results
1 in the opposite direction
- positive
ozone · growth · Trifolium pratense (red clover)Results agree
3 papers in the same direction as this paper
- negative
- negative
- 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.