Abstract
Abstract Soil acidification caused by atmospheric sulphur (S) deposition may have a significant impact on plant carbon (C) assimilation and allocation, thereby altering soil organic C (SOC) dynamics. However, it remains largely unknown how plants allocate photosynthetic C among below‐ground C sinks and whether they can leverage these limited C resources to adapt to abiotic stresses. We conducted a 13 CO 2 pulse labelling experiment in a meadow to investigate the effects of soil acidification, induced by S addition, on photosynthetic C allocation and to explore the trade‐offs among plant below‐ground sinks as well as the contribution of below‐ground C allocation to SOC formation. We found that soil acidification decreased rhizodeposit C (13%–60%) and the absolute amount of 13 C allocated to soil (0.8%–51%), due to a 30%–36% reduction in shoot photosynthetic 13 C assimilation. Conversely, S addition increased the proportion of 13 C allocated to roots by 3%–52%. The root biomass, non‐structural carbohydrates (NSC) and respiration increased with S addition rates, and a threshold point appeared around 20 g S m −2 year −1 , after which they began to decline. Root 13 C was negatively correlated with soil 13 C but positively associated with both root biomass and NSC. Soil acidification led to an increase in below‐ground biomass, while SOC stocks remained unchanged, possibly due to reduced rhizodeposit C input accompanied by suppressed SOC decomposition. Synthesis . These results confirm that under soil acidification, less photosynthetic C in roots was converted into rhizodeposit C entering the soil, while proportionally more was invested in root growth, respiration and storage to cope with acidification stress. Overall, the trade‐off in C allocation between root biomass and rhizodeposition may underlie plant adaptation to soil acidification and is a key indicator for predicting SOC dynamics.
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Claims 13
Claim · model-written summary
Soil acidification decreased rhizodeposit C by 13%–60%.
Not reportedComparator
Verbatim
e0“We found that soil acidification decreased rhizodeposit C (13%–60%) and the absolute amount of 13 C allocated to soil (0.8%–51%), due to a 30%–36% reduction in shoot photosynthetic 13 C assimilation.”
t0“plant”
Claim · model-written summary
Soil acidification decreased absolute 13 C allocation to soil by 0.8%–51%.
- Taxon
- plantt0
- Treatment
- soil acidificatione0
- Outcome
- absolute amount of 13 C allocated to soile0
- Direction
- decreasede0
- Value
- 0.8%–51%e0
Not reportedComparator
Verbatim
e0“We found that soil acidification decreased rhizodeposit C (13%–60%) and the absolute amount of 13 C allocated to soil (0.8%–51%), due to a 30%–36% reduction in shoot photosynthetic 13 C assimilation.”
t0“plant”
Claim · model-written summary
Soil acidification reduced shoot photosynthetic 13 C assimilation by 30%–36%.
- Taxon
- plantt0
- Treatment
- soil acidificatione0
- Outcome
- shoot photosynthetic 13 C assimilatione0
- Direction
- reductione0
- Value
- 30%–36%e0
Not reportedComparator
Verbatim
e0“We found that soil acidification decreased rhizodeposit C (13%–60%) and the absolute amount of 13 C allocated to soil (0.8%–51%), due to a 30%–36% reduction in shoot photosynthetic 13 C assimilation.”
t0“plant”
Claim · model-written summary
S addition increased the fraction of 13 C allocated to roots by 3%–52%.
- Taxon
- plantt0
- Treatment
- S additione0
- Outcome
- proportion of 13 C allocated to rootse0
- Direction
- increasede0
- Value
- 3%–52%e0
Not reportedComparator
Verbatim
e0“Conversely, S addition increased the proportion of 13 C allocated to roots by 3%–52%.”
t0“plant”
Claim · model-written summary
root biomass increased with S addition up to about 20 g S m −2 year −1, then declined.
Verbatim
e0“The root biomass, non‐structural carbohydrates (NSC) and respiration increased with S addition rates, and a threshold point appeared around 20 g S m −2 year −1 , after which they began to decline.”
t0“plant”
Claim · model-written summary
non‐structural carbohydrates (NSC) increased with S addition up to about 20 g S m −2 year −1, then declined.
Verbatim
e0“The root biomass, non‐structural carbohydrates (NSC) and respiration increased with S addition rates, and a threshold point appeared around 20 g S m −2 year −1 , after which they began to decline.”
t0“plant”
Claim · model-written summary
respiration increased with S addition up to about 20 g S m −2 year −1, then declined.
Verbatim
e0“The root biomass, non‐structural carbohydrates (NSC) and respiration increased with S addition rates, and a threshold point appeared around 20 g S m −2 year −1 , after which they began to decline.”
t0“plant”
Claim · model-written summary
Root 13 C was negatively correlated with soil 13 C.
Verbatim
e0“Root 13 C was negatively correlated with soil 13 C but positively associated with both root biomass and NSC.”
t0“plant”
Claim · model-written summary
Root 13 C was positively associated with root biomass and NSC.
Verbatim
e0“Root 13 C was negatively correlated with soil 13 C but positively associated with both root biomass and NSC.”
t0“plant”
Claim · model-written summary
Soil acidification increased below-ground biomass.
Not reportedComparator
Verbatim
e0“Soil acidification led to an increase in below‐ground biomass, while SOC stocks remained unchanged”
t0“plant”
Claim · model-written summary
SOC stocks remained unchanged under soil acidification.
Not reportedTaxonComparator
Verbatim
e0“Soil acidification led to an increase in below‐ground biomass, while SOC stocks remained unchanged”
Claim · model-written summary
Reduced rhizodeposit input and suppressed SOC decomposition may explain stable SOC stocks.
- Outcome
- SOC stocks remained unchangede0
- Qualifier
- reduced rhizodeposit C input accompanied by suppressed SOC decompositione0
Not reportedTaxon
Verbatim
e0“SOC stocks remained unchanged, possibly due to reduced rhizodeposit C input accompanied by suppressed SOC decomposition.”
Claim · model-written summary
Under acidification, less root photosynthate became rhizodeposit C, while more supported root growth, respiration, and storage.
Verbatim
e0“under soil acidification, less photosynthetic C in roots was converted into rhizodeposit C entering the soil, while proportionally more was invested in root growth, respiration and storage to cope with acidification stress.”
t0“plant”