Abstract
Plant species typical of semi‐natural grasslands were tested for their sensitivity to long‐term ozone effects on growth under two irrigation regimes, and the relationship between ozone sensitivity, relative growth rate, and plant strategy was analysed. Individuals of 24 grasses, herbs and legumes were grown in pots and exposed for two seasons to four levels of ozone in open‐top chambers: (a) CF, charcoal‐filtered air, (b) CFAA, charcoal‐filtered air plus ozone to match ambient levels, (c) CF+, charcoal‐filtered air plus ozone added to match 1.5 times ambient levels and (d) CF++, charcoal‐filtered air with ozone added to match twice ambient levels during selected episodes of 7–13 d. During the ozone episodes, one half of the plants received reduced irrigation (dry treatment) while the rest was kept well watered (wet treatment). The effect of ozone on the relative growth rate was determined during the initial growth period during the first season. Above‐ground plant dry weight was determined three times during each season, and stubble dry weight at the end of the experiment. In most species, the effect of ozone on relative growth rate was not significant, except in Centaurea jacea and Lychnis flos‐cuculi for which a significant stimulation of relative growth rate was found. There was a significant negative relationship between percentage relative growth rate and relative growth rate measured in the CF treatment, indicating that in species growing faster in clean air relative growth rate tended to be more sensitive to ozone than in slower‐growing species. After the first re‐growth period during the first season, a significant effect of ozone on above‐ground biomass was found in five species, i.e. a decrease in Chrysanthemum leucanthemum , Trifolium pratense and T. repens , and an increase in Silene dioïca . During the second season no significant ozone effect was detected, except for an increase in stubble mass in C. leucanthemum . In 10 species, the dry treatment caused a significant decrease in biomass, but in Plantago lanceolata during the first year, and in Knautia arvensis and T. repens during the second year, an ozone×irrigation interaction was observed. Exposure–response patterns in the wet treatment varied between species. In some species growth tended to be increased in charcoal‐filtered air plus ozone to ambient levels, in others either a continuous increase or decrease in biomass was observed with increasing ozone. Trifolium repens showed the lowest AOT40 (ozone accumulated above a threshold of 40 ppb) corresponding to a 10% change in biomass. The comparison between exposure–response pattern between the wet and dry treatments revealed reduced, increased, or unchanged ozone sensitivity. The shift was related to plant strategy and not to the specific sensitivity to the dry treatment. The specific response to both ozone and dry treatment tended to be related to Grime's triangular classification of plant strategies, i.e. the C‐S‐R model. In species with a large component of C (competitor strategy), and/or R (ruderal strategy), biomass was more sensitive to both stresses, compared with species with a high component of S (stress tolerators), and ozone×drought interactions were more pronounced. The results indicate that specific relative growth rate is an important determinant for the potential sensitivity of grassland species to long‐term effects of ozone, and that reduced irrigation causes no general protection from the effects of ozone on growth.
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Claims 18
Claim · model-written summary
Ozone significantly stimulated relative growth rate in Centaurea jacea.
- Taxon
- Centaurea jacea
Centaurea jaceae0 - Treatment
- ozonee0
- Outcome
- relative growth ratee0
- Direction
- stimulatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In most species, the effect of ozone on relative growth rate was not significant, except in Centaurea jacea and Lychnis flos‐cuculi for which a significant stimulation of relative growth rate was found”
Claim · model-written summary
Ozone significantly stimulated relative growth rate in Lychnis flos‐cuculi.
Not reportedComparator
Verbatim
e0“In most species, the effect of ozone on relative growth rate was not significant, except in Centaurea jacea and Lychnis flos‐cuculi for which a significant stimulation of relative growth rate was found”
Claim · model-written summary
Species with faster growth in clean air tended to have greater ozone sensitivity of relative growth rate.
Verbatim
e0“There was a significant negative relationship between percentage relative growth rate and relative growth rate measured in the CF treatment, indicating that in species growing faster in clean air relative growth rate tended to be more sensitive to ozone than in slower‐growing species”
t0“grassland species”
Claim · model-written summary
Ozone caused a significant decrease in aboveground biomass of Chrysanthemum leucanthemum after first regrowth.
- Taxon
- Chrysanthemum leucanthemum
Leucanthemum vulgaree0 - Treatment
- ozonee0
- Outcome
- above‐ground biomasse0
- Direction
- decreasee0
- Qualifier
- first re‐growth periode0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After the first re‐growth period during the first season, a significant effect of ozone on above‐ground biomass was found in five species, i.e. a decrease in Chrysanthemum leucanthemum , Trifolium pratense and T. repens , and an increase in Silene dioïca”
Claim · model-written summary
Ozone caused a significant decrease in aboveground biomass of Trifolium pratense after first regrowth.
- Taxon
- Trifolium pratense
Trifolium pratensee0 - Treatment
- ozonee0
- Outcome
- above‐ground biomasse0
- Direction
- decreasee0
- Qualifier
- first re‐growth periode0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After the first re‐growth period during the first season, a significant effect of ozone on above‐ground biomass was found in five species, i.e. a decrease in Chrysanthemum leucanthemum , Trifolium pratense and T. repens , and an increase in Silene dioïca”
Claim · model-written summary
Ozone caused a significant decrease in aboveground biomass of T. repens after first regrowth.
- Taxon
- T. repens
Trifolium repense0 - Treatment
- ozonee0
- Outcome
- above‐ground biomasse0
- Direction
- decreasee0
- Qualifier
- first re‐growth periode0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After the first re‐growth period during the first season, a significant effect of ozone on above‐ground biomass was found in five species, i.e. a decrease in Chrysanthemum leucanthemum , Trifolium pratense and T. repens , and an increase in Silene dioïca”
Claim · model-written summary
Ozone caused a significant increase in aboveground biomass of Silene dioïca after first regrowth.
- Taxon
- Silene dioïcae0
- Treatment
- ozonee0
- Outcome
- above‐ground biomasse0
- Direction
- increasee0
- Qualifier
- first re‐growth periode0
Not reportedComparator
Verbatim
e0“After the first re‐growth period during the first season, a significant effect of ozone on above‐ground biomass was found in five species, i.e. a decrease in Chrysanthemum leucanthemum , Trifolium pratense and T. repens , and an increase in Silene dioïca”
Claim · model-written summary
Ozone increased stubble mass of C. leucanthemum in the second season.
- Taxon
- C. leucanthemumLeucanthemum vulgaree0
- Treatment
- ozonee0
- Outcome
- stubble masse0
- Direction
- increasee0
- Qualifier
- second seasone0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“During the second season no significant ozone effect was detected, except for an increase in stubble mass in C. leucanthemum”
Claim · model-written summary
Reduced irrigation significantly decreased biomass in ten species.
- Taxon
- grassland speciest0
- Treatment
- dry treatmente0
- Outcome
- biomasse0
- Direction
- decreasee0
- Value
- 10 speciese0
Not reportedComparator
Verbatim
e0“In 10 species, the dry treatment caused a significant decrease in biomass”
t0“grassland species”
Claim · model-written summary
An ozone by irrigation interaction was observed in Plantago lanceolata in the first year.
- Taxon
- Plantago lanceolata
Plantago lanceolatae0 - Treatment
- ozone×irrigatione0
- Outcome
- ozone×irrigation interactione0
- Qualifier
- first yeare0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in Plantago lanceolata during the first year, and in Knautia arvensis and T. repens during the second year, an ozone×irrigation interaction was observed”
Claim · model-written summary
An ozone by irrigation interaction was observed in Knautia arvensis in the second year.
- Taxon
- Knautia arvensis
Knautia arvensise0 - Treatment
- ozone×irrigatione0
- Outcome
- ozone×irrigation interactione0
- Qualifier
- second yeare0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in Plantago lanceolata during the first year, and in Knautia arvensis and T. repens during the second year, an ozone×irrigation interaction was observed”
Claim · model-written summary
An ozone by irrigation interaction was observed in T. repens in the second year.
- Taxon
- T. repensTrifolium repense0
- Treatment
- ozone×irrigatione0
- Outcome
- ozone×irrigation interactione0
- Qualifier
- second yeare0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in Plantago lanceolata during the first year, and in Knautia arvensis and T. repens during the second year, an ozone×irrigation interaction was observed”
Claim · model-written summary
Trifolium repens had the lowest ozone exposure threshold corresponding to a 10% biomass change.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Trifolium repens showed the lowest AOT40 (ozone accumulated above a threshold of 40 ppb) corresponding to a 10% change in biomass”
Claim · model-written summary
Ozone sensitivity shifts between wet and dry conditions were related to plant strategy.
Not reportedDirection
Verbatim
e0“The shift was related to plant strategy and not to the specific sensitivity to the dry treatment”
t0“grassland species”
Claim · model-written summary
Species with larger competitor or ruderal strategy components had more biomass sensitivity to both stresses than stress tolerators.
Verbatim
e0“In species with a large component of C (competitor strategy), and/or R (ruderal strategy), biomass was more sensitive to both stresses, compared with species with a high component of S (stress tolerators), and ozone×drought interactions were more pronounced”
t0“grassland species”
Claim · model-written summary
Ozone by drought interactions were more pronounced in competitor or ruderal species than stress tolerators.
Verbatim
e0“In species with a large component of C (competitor strategy), and/or R (ruderal strategy), biomass was more sensitive to both stresses, compared with species with a high component of S (stress tolerators), and ozone×drought interactions were more pronounced”
t0“grassland species”
Claim · model-written summary
Specific relative growth rate was identified as a determinant of long term ozone sensitivity.
- Taxon
- grassland speciese0
- Treatment
- ozonee0
- Outcome
- potential sensitivitye0
- Qualifier
- specific relative growth ratee0
Not reportedDirection
Verbatim
e0“specific relative growth rate is an important determinant for the potential sensitivity of grassland species to long‐term effects of ozone”
Claim · model-written summary
Reduced irrigation offered no general protection from ozone effects on growth.
- Taxon
- grassland speciest0
- Treatment
- reduced irrigatione0
- Outcome
- effects of ozone on growthe0
- Direction
- no general protectione0
Not reportedComparator
Verbatim
e0“reduced irrigation causes no general protection from the effects of ozone on growth”
t0“grassland species”
The same questions in other papers
ozone · growth · Leucanthemum vulgareResults agree
1 paper in the same direction as this paper
- negative
ozone · growth · Trifolium pratense (red clover)Results agree
3 papers in the same direction as this paper
- negative
- negative
- negative
ozone · growth · Trifolium repens (white clover)Results agree
5 papers in the same direction as this paper
- negative
- negative
- negative
2 papers more in this group
See all 6 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.