Abstract
BackgroundSoil microbial communities can affect plant nutrient uptake, productivity, and may even confer resistance to global change. Elevated atmospheric CO2 is widely expected to stimulate plant productivity; however, this will depend on the availability of growth limiting nutrients such as nitrogen. Soil microbial communities are the main mediators of soil nitrogen cycling and should therefore play a key role in influencing plant responses to elevated CO2.ResultsTo test this, we conducted a controlled, growth chamber experiment with Pinus sylvestris to evaluate how soil microbiome variation influences plant physiology, productivity, and responses to elevated CO₂ (eCO₂; 800 ppm versus 400 ppm in the ambient treatment). Field soils were collected from six forests with varying tree growth rates and were used as an inoculant source, either sterilized or living, into a common growth medium seeded with P. sylvestris. After seven months of growth, we measured plant carbon assimilation, photosynthetic nitrogen use efficiency, above- and belowground productivity, and we measured soil microbial biodiversity using DNA metabarcoding. Our findings demonstrate that seedling productivity was stimulated under eCO2 conditions and that this was supported by improved plant photosynthetic nitrogen use efficiency, but only in the presence of living versus sterilized soil inoculant. The magnitude of this response was also dependent on the forest soil microbial inoculant source and was linked to a 70% increase in bacterial species richness, increased relative abundances of bacteria known to have positive effects on plant growth (e.g., Lactobacillus, Bacillus, Flavobacterium), and with a concomitant shift in saprotrophic fungal community composition and root growth. Variation in inorganic nitrogen cycling which favored the accumulation of nitrate under eCO2 was also correlated with a twofold reduction in photosynthetic nitrogen use efficiency, suggesting a decoupling of nitrogen availability and assimilation efficiency with distinct implications for plant growth responses to elevated CO2.ConclusionsOur results show that soil microbial community variation directly affects P. sylvestris physiology, productivity, and responses to eCO2, and may enhance plant growth through improved nitrogen use efficiency. Surprisingly, growth with different microbial communities even more strongly impacted plant productivity than a doubling of atmospheric CO2 concentrations. The soil microbiome therefore plays a key role in supporting plant nutrition and growth under ambient and eCO2 conditions, and in turn, may confer increased forest resistance to climate change.
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Claims 9
Claim · model-written summary
Elevated CO2 stimulated pine seedling productivity only with living soil inoculant.
- Taxon
- Pinus sylvestris
Pinus sylvestrist0 - Treatment
- eCO2 conditionse0
- Outcome
- seedling productivitye0
- Direction
- stimulatede0
- Qualifier
- only in the presence of living versus sterilized soil inoculante0
- Comparator
- sterilized soil inoculante0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“seedling productivity was stimulated under eCO2 conditions and that this was supported by improved plant photosynthetic nitrogen use efficiency, but only in the presence of living versus sterilized soil inoculant”
t0“Pinus sylvestris”
Claim · model-written summary
Elevated CO2 improved pine photosynthetic nitrogen use efficiency only with living soil inoculant.
- Taxon
- Pinus sylvestrisPinus sylvestrist0
- Treatment
- eCO2 conditionse1
- Outcome
- plant photosynthetic nitrogen use efficiencye0
- Direction
- improvede0
- Comparator
- sterilized soil inoculante0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“improved plant photosynthetic nitrogen use efficiency, but only in the presence of living versus sterilized soil inoculant”
e1“under eCO2 conditions”
t0“Pinus sylvestris”
Claim · model-written summary
The magnitude of the elevated CO2 response depended on forest soil inoculant source.
- Taxon
- Pinus sylvestrisPinus sylvestrist0
- Treatment
- forest soil microbial inoculant sourcee0
- Outcome
- magnitude of this responsee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The magnitude of this response was also dependent on the forest soil microbial inoculant source”
t0“Pinus sylvestris”
Claim · model-written summary
The response was linked to a 70% increase in bacterial species richness.
- Taxon
- Pinus sylvestrisPinus sylvestrist0
- Treatment
- forest soil microbial inoculant sourcee2
- Outcome
- bacterial species richnesse0
- Direction
- increasee0
- Value
- 70%e0
- Qualifier
- magnitude of this responsee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“linked to a 70% increase in bacterial species richness”
e1“The magnitude of this response”
e2“forest soil microbial inoculant source”
t0“Pinus sylvestris”
Claim · model-written summary
The response was linked to increased relative abundance of growth-promoting bacteria.
- Taxon
- Pinus sylvestrisPinus sylvestrist0
- Treatment
- forest soil microbial inoculant sourcee2
- Outcome
- relative abundances of bacteriae0
- Direction
- increasede0
- Qualifier
- magnitude of this responsee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased relative abundances of bacteria known to have positive effects on plant growth (e.g., Lactobacillus, Bacillus, Flavobacterium)”
e1“The magnitude of this response”
e2“forest soil microbial inoculant source”
t0“Pinus sylvestris”
Claim · model-written summary
The response coincided with a shift in saprotrophic fungal composition and root growth.
- Taxon
- Pinus sylvestrisPinus sylvestrist0
- Treatment
- forest soil microbial inoculant sourcee2
- Outcome
- saprotrophic fungal community composition and root growthe0
- Qualifier
- magnitude of this responsee1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a concomitant shift in saprotrophic fungal community composition and root growth”
e1“The magnitude of this response”
e2“forest soil microbial inoculant source”
t0“Pinus sylvestris”
Claim · model-written summary
Inorganic nitrogen cycling under elevated CO2 favored nitrate accumulation.
- Taxon
- Pinus sylvestrisPinus sylvestrist0
- Treatment
- eCO2e0
- Outcome
- accumulation of nitratee0
- Direction
- favorede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Variation in inorganic nitrogen cycling which favored the accumulation of nitrate under eCO2”
t0“Pinus sylvestris”
Claim · model-written summary
Nitrate-favoring nitrogen cycling correlated with a twofold reduction in photosynthetic nitrogen use efficiency.
- Taxon
- Pinus sylvestrisPinus sylvestrist0
- Compound
- nitratee0
- Outcome
- photosynthetic nitrogen use efficiencye0
- Direction
- reductione0
- Value
- twofolde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Variation in inorganic nitrogen cycling which favored the accumulation of nitrate under eCO2 was also correlated with a twofold reduction in photosynthetic nitrogen use efficiency”
t0“Pinus sylvestris”
Claim · model-written summary
Different microbial communities affected pine productivity more strongly than doubled atmospheric CO2.
- Taxon
- Pinus sylvestrisPinus sylvestrist0
- Treatment
- different microbial communitiese0
- Outcome
- plant productivitye0
- Direction
- more strongly impactede0
- Comparator
- a doubling of atmospheric CO2 concentrationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“growth with different microbial communities even more strongly impacted plant productivity than a doubling of atmospheric CO2 concentrations”
t0“Pinus sylvestris”
The same questions in other papers
co2 · yield · Pinus sylvestris (Scots pine)Results differ
4 papers in the same direction as this paper · 1 in the opposite direction
- no effect
- positive
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See all 6 papers →co2 · physiology: photosynthesis · Pinus sylvestris (Scots pine)Positive and negative results
5 papers in the same direction as this paper · 2 in the opposite direction
- no effect
- negative
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4 papers more in this group
See all 8 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.