Abstract
In a six years' field study (1995-2000) we have studied the effects of elevated CO2 on photosynthesis, above- and below-ground production and root dynamics in a species-rich semi-natural grassland with a long history of grazing in Central Sweden (59° 48'N, 17° 38'E, 10 m a.s.l.). We used open-top chambers with ambient (A, ca 350 µmol/mol) and elevated (E, ca 700 µmol/mol) CO2 treatments, and a control treatment consisting of rings without mounted chambers. Elevated CO2 was supplied to treatment E continuously during the field season (April-October/November). During each field season, elevated CO2 stimulated light-saturated leaf-level photosynthesis of Taraxacum vulgare and Plantago media. Although photosynthesis showed a significant decrease during each growing season, the CO2 effect (treatment E/A) was rather constant. We found no trend in photosynthesis or the effect of CO2 hereon over the years, but during the dry and extremely dry summers of 1996 and 1999, respectively, the CO2 effect on leaf-level photosynthesis was significantly larger than during rainy summers. Elevated CO2 stimulated above-ground production (standing crop in early August) in 1995-1997, but not in 1998-2000. Root production (measured with minirhizotrons and ingrowth-bags) was stimulated during each growing season. The lack of above-ground production response during the latter years may be explained by unusual weather circumstances (1998 and 2000 being extremely wet and overcast with only few sunny days, and 1999 being extremely dry). However, increasing nutrient limitation might also be involved.
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Claims 10
Claim · model-written summary
Elevated CO2 stimulated light-saturated leaf-level photosynthesis of Taraxacum vulgare.
- Taxon
- Taraxacum vulgare
Taraxacum officinalee0 - Treatment
- elevated CO2e0
- Outcome
- light-saturated leaf-level photosynthesise0
- Direction
- stimulatede0
- Comparator
- ambient (A, ca 350 µmol/mol)e1
- Setting
- Central Swedene2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“elevated CO2 stimulated light-saturated leaf-level photosynthesis of Taraxacum vulgare and Plantago media”
e1“open-top chambers with ambient (A, ca 350 µmol/mol) and elevated (E, ca 700 µmol/mol) CO2 treatments”
e2“in a species-rich semi-natural grassland with a long history of grazing in Central Sweden”
Claim · model-written summary
Elevated CO2 stimulated light-saturated leaf-level photosynthesis of Plantago media.
- Taxon
- Plantago media
.jpg?width=60)
Plantago mediae0 - Treatment
- elevated CO2e0
- Outcome
- light-saturated leaf-level photosynthesise0
- Direction
- stimulatede0
- Comparator
- ambient (A, ca 350 µmol/mol)e1
- Setting
- Central Swedene2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“elevated CO2 stimulated light-saturated leaf-level photosynthesis of Taraxacum vulgare and Plantago media”
e1“open-top chambers with ambient (A, ca 350 µmol/mol) and elevated (E, ca 700 µmol/mol) CO2 treatments”
e2“in a species-rich semi-natural grassland with a long history of grazing in Central Sweden”
Claim · model-written summary
Photosynthesis of the grassland showed a significant decrease during each growing season.
Verbatim
e3“Although photosynthesis showed a significant decrease during each growing season”
e2“in a species-rich semi-natural grassland with a long history of grazing in Central Sweden”
Claim · model-written summary
The CO2 effect on photosynthesis showed no trend over the years.
- Taxon
- species-rich semi-natural grasslande2
- Treatment
- elevated CO2e0
- Outcome
- trend in photosynthesis or the effect of CO2e5
- Direction
- no trende5
Not reportedComparator
Verbatim
e5“We found no trend in photosynthesis or the effect of CO2 hereon over the years”
e2“in a species-rich semi-natural grassland with a long history of grazing in Central Sweden”
e0“elevated CO2 stimulated light-saturated leaf-level photosynthesis of Taraxacum vulgare and Plantago media”
Claim · model-written summary
The CO2 effect on leaf-level photosynthesis was larger in dry and extremely dry summers than in rainy summers.
Verbatim
e4“during the dry and extremely dry summers of 1996 and 1999, respectively, the CO2 effect on leaf-level photosynthesis was significantly larger than during rainy summers”
e2“in a species-rich semi-natural grassland with a long history of grazing in Central Sweden”
e0“elevated CO2 stimulated light-saturated leaf-level photosynthesis of Taraxacum vulgare and Plantago media”
Claim · model-written summary
Elevated CO2 stimulated above-ground production in 1995-1997.
- Taxon
- species-rich semi-natural grasslande2
- Treatment
- Elevated CO2e5
- Outcome
- above-ground productione5
- Direction
- stimulatede5
- Qualifier
- in 1995-1997e5
Not reportedComparator
Verbatim
e5“Elevated CO2 stimulated above-ground production (standing crop in early August) in 1995-1997, but not in 1998-2000”
e2“in a species-rich semi-natural grassland with a long history of grazing in Central Sweden”
Claim · model-written summary
Elevated CO2 did not change above-ground production in 1998-2000.
- Taxon
- species-rich semi-natural grasslande2
- Treatment
- Elevated CO2e5
- Outcome
- above-ground productione5
- Direction
- no_changeinferrede5
- Qualifier
- 1998-2000e5
Not reportedComparator
Verbatim
e5“Elevated CO2 stimulated above-ground production (standing crop in early August) in 1995-1997, but not in 1998-2000”
e2“in a species-rich semi-natural grassland with a long history of grazing in Central Sweden”
Claim · model-written summary
Elevated CO2 stimulated root production during each growing season.
- Taxon
- species-rich semi-natural grasslande2
- Treatment
- elevated CO2e0
- Outcome
- Root productione6
- Direction
- stimulatede6
- Qualifier
- during each growing seasone6
Not reportedComparator
Verbatim
e6“Root production (measured with minirhizotrons and ingrowth-bags) was stimulated during each growing season”
e2“in a species-rich semi-natural grassland with a long history of grazing in Central Sweden”
e0“elevated CO2 stimulated light-saturated leaf-level photosynthesis of Taraxacum vulgare and Plantago media”
Claim · model-written summary
The lack of above-ground production response may be explained by unusual weather circumstances.
Verbatim
e7“The lack of above-ground production response during the latter years may be explained by unusual weather circumstances”
e2“in a species-rich semi-natural grassland with a long history of grazing in Central Sweden”
Claim · model-written summary
Increasing nutrient limitation might also be involved in the lack of above-ground production response.
Verbatim
e6“increasing nutrient limitation might also be involved”
e7“The lack of above-ground production response during the latter years may be explained by unusual weather circumstances”
e2“in a species-rich semi-natural grassland with a long history of grazing in Central Sweden”