Abstract
Increased atmospheric CO2 concentration will have an significant impact on the nitrogen cycle of terrestrial ecosystems. The elevation of atmospheric CO2 has become an inevitable trend, and nitrogen is the most important factor affecting plant growth. But it is rare to explore the effect of CO2 on nitrogen cycle by measuring the value of δ15N. The δ15N value as a comprehensive indicator of the nitrogen cycle of the ecosystem, which can not only clarify the migration and transformation of nitrogen, but also effectively indicate the nitrogen limit and nitrogen open level of the ecosystem. Our experiment selected alfalfa (C3 plant) as the research object, then investigated the response of nitrate nitrogen, ammonia nitrogen and absorbable nitrogen to the elevated CO2 concentration in soil and alfalfa leaves under ambient and elevated atmospheric CO2 (500 and 700ppm) in open top chambers. The 15N isotope value was determined by bacterial denitrification , and 15N-gas chromatography (GC-MS) were applied to further analyze the effect of elevated CO2 concentration on nitrogen cycling in soil and plant leaves. The increase of CO2 concentration led to the decline of various inorganic nitrogen levels in soil, and the δ15N in the soil also showed a certain downward trend, but always maintained a positive value. The nitrogen level and δ15N values in alfalfa leaves did not change significantly, showing a small increase. It indicates that there are different degrees of nitrogen loss in the leaves under the influence of different concentrations of CO2. These results are closely related to the fractional distillation of nitrogen isotopes caused by microorganisms in the process of nitrogen morphologic transformation. We briefly reviewed the changes of nitrogen content in soil and plant leaves under elevated CO2, providing new insights into the nitrogen cycle of soils and plants under high CO2 concentrations. It also provides a scientific basis for the protection of soil and plants under the greenhouse effect.
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Claims 5
Claim · model-written summary
Elevated CO2 decreased the various inorganic nitrogen levels in soil relative to ambient CO2.
- Taxon
- alfalfa
Medicago sativat0 - Treatment
- increase of CO2 concentratione1
- Outcome
- various inorganic nitrogen levelse1
- Direction
- declinee1
- Comparator
- ambiente2
- Setting
- open top chamberse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soil and alfalfa leaves”
e1“The increase of CO2 concentration led to the decline of various inorganic nitrogen levels in soil”
e2“under ambient and elevated atmospheric CO2 (500 and 700ppm) in open top chambers”
Claim · model-written summary
Soil delta-15N under elevated CO2 showed a downward trend but remained positive.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- increase of CO2 concentratione1
- Outcome
- δ15N in the soile3
- Direction
- downward trende3
- Qualifier
- always maintained a positive valuee3
- Comparator
- ambiente2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soil and alfalfa leaves”
e1“The increase of CO2 concentration led to the decline of various inorganic nitrogen levels in soil”
e2“under ambient and elevated atmospheric CO2 (500 and 700ppm) in open top chambers”
e3“the δ15N in the soil also showed a certain downward trend, but always maintained a positive value”
Claim · model-written summary
Elevated CO2 did not significantly change nitrogen level or delta-15N in alfalfa leaves, which showed a small increase.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- increase of CO2 concentratione1
- Outcome
- nitrogen level and δ15N values in alfalfa leavese4
- Direction
- did not change significantlye4
- Qualifier
- showing a small increasee4
- Comparator
- ambiente2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soil and alfalfa leaves”
e1“The increase of CO2 concentration led to the decline of various inorganic nitrogen levels in soil”
e2“under ambient and elevated atmospheric CO2 (500 and 700ppm) in open top chambers”
e4“The nitrogen level and δ15N values in alfalfa leaves did not change significantly, showing a small increase”
Claim · model-written summary
Different CO2 concentrations were associated with different degrees of nitrogen loss in alfalfa leaves.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- different concentrations of CO2e5
- Outcome
- nitrogen losse5
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soil and alfalfa leaves”
e5“It indicates that there are different degrees of nitrogen loss in the leaves under the influence of different concentrations of CO2”
Claim · model-written summary
The nitrogen results are explained by fractional distillation of nitrogen isotopes caused by microorganisms during nitrogen transformation.
- Taxon
- alfalfaMedicago sativat0
- Outcome
- These resultse6
- Qualifier
- fractional distillation of nitrogen isotopes caused by microorganismse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“soil and alfalfa leaves”
e6“These results are closely related to the fractional distillation of nitrogen isotopes caused by microorganisms in the process of nitrogen morphologic transformation”
The same questions in other papers
co2 · nutrient: content · Medicago sativa (alfalfa)Results differ
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