Abstract
The leaching of soil nitrogen (N) has become one of the most concerning environmental threats to ecosystems. Arbuscular mycorrhizal (AM) fungi have important ecological functions, however, their influence on soil N leaching and the mechanism of action remain unclear. We conducted a two-factor (N application level × AM inoculation) experiment on poplar, and for the first time, comprehensively analyzed the mechanism by which AM fungi influence soil N leaching. The results showed that, under optimum (7.5 mM) and high (20 mM) N levels, the nitrate (NO3−) and ammonium (NH4+) concentrations of leachate in the AM inoculated treatment (+AM) were lower than in the non-inoculated treatment (−AM), with significant reductions of 20.0% and 67.5%, respectively, under high N level, indicating that AM inoculation can reduce soil N leaching and that it is more effective for NH4+. The arbuscular and total colonization rates gradually increased, and the morphology of spores and vesicles changed as the N level increased. Under optimum and high N levels, +AM treatment increased the root N concentration by 11.7% and 50.7%, respectively; the increase was significant (p < 0.05) at the high N level, which was associated with slightly increased transpiration and root activity despite reductions in root surface area and root length. Additionally, the +AM treatment increased soil cation exchange capacity (CEC), soil organic carbon (SOC), and significantly (p < 0.05) increased the proportions of macroaggregates (but without significant change in microaggregates), causing soil total nitrogen (TN) to increase by 7.2% and 4.7% under optimum and high N levels, respectively. As the N levels increased, the relative contributions of AM inoculation on N leaching increased, however, the contributions of plant physiological and soil variables decreased. Among all of the variables, SOC had important contributions to NH4+ and total N in the leachate, while root N concentration had a higher contribution to NO3−. In conclusion, AM fungi can mitigate soil N leaching and lower the risk of environmental pollution via enhancing N interception by the inoculated fungi, increasing N sequestration in plant roots, and by improving soil N retention.
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Claims 16
Claim · model-written summary
AM inoculation lowered leachate nitrate under optimum and high N, by 20.0% at high N.
- Treatment
- AM inoculated treatment (+AM)e0
- Interactor
- AMe0symbiont
- Outcome
- nitrate (NO3−)e0
- Direction
- lowere0
- Value
- 20.0%e0
- Qualifier
- under high N levele0
- Comparator
- non-inoculated treatment (−AM)e0
PopulusOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under optimum (7.5 mM) and high (20 mM) N levels, the nitrate (NO3−) and ammonium (NH4+) concentrations of leachate in the AM inoculated treatment (+AM) were lower than in the non-inoculated treatment (−AM), with significant reductions of 20.0% and 67.5%, respectively, under high N level”
t0“Poplar Seedlings”
Claim · model-written summary
AM inoculation lowered leachate ammonium under optimum and high N, by 67.5% at high N.
- Treatment
- AM inoculated treatment (+AM)e0
- Interactor
- AMe0symbiont
- Outcome
- ammonium (NH4+) concentrations of leachatee0
- Direction
- lowere0
- Value
- 67.5%e0
- Comparator
- non-inoculated treatment (−AM)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“under optimum (7.5 mM) and high (20 mM) N levels, the nitrate (NO3−) and ammonium (NH4+) concentrations of leachate in the AM inoculated treatment (+AM) were lower than in the non-inoculated treatment (−AM), with significant reductions of 20.0% and 67.5%, respectively, under high N level”
t0“Poplar Seedlings”
Claim · model-written summary
AM spore and vesicle morphology changed as N level increased.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the morphology of spores and vesicles changed as the N level increased”
t0“Poplar Seedlings”
Claim · model-written summary
AM increased root N concentration 11.7% at optimum N.
- Treatment
- +AM treatmente0
- Outcome
- root N concentratione0
- Direction
- increasede0
- Value
- 11.7%e0
- Qualifier
- optimume0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under optimum and high N levels, +AM treatment increased the root N concentration by 11.7% and 50.7%, respectively”
t0“Poplar Seedlings”
Claim · model-written summary
AM increased root N concentration 50.7% at high N, significantly.
- Treatment
- +AM treatmente0
- Outcome
- root N concentratione0
- Direction
- increasede0
- Value
- 50.7%e0
- Qualifier
- high N levele0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under optimum and high N levels, +AM treatment increased the root N concentration by 11.7% and 50.7%, respectively; the increase was significant (p < 0.05) at the high N level”
t0“Poplar Seedlings”
Claim · model-written summary
AM slightly increased transpiration and root activity.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“which was associated with slightly increased transpiration and root activity despite reductions in root surface area and root length”
t0“Poplar Seedlings”
t1“AM inoculation) experiment”
Claim · model-written summary
AM reduced root surface area and root length.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“despite reductions in root surface area and root length”
t0“Poplar Seedlings”
t1“AM inoculation) experiment”
Claim · model-written summary
AM increased soil CEC and SOC.
- Treatment
- +AM treatmente0
- Outcome
- soil cation exchange capacity (CEC), soil organic carbon (SOC)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the +AM treatment increased soil cation exchange capacity (CEC), soil organic carbon (SOC)”
t0“Poplar Seedlings”
Claim · model-written summary
AM significantly increased macroaggregate proportions.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“significantly (p < 0.05) increased the proportions of macroaggregates”
t0“Poplar Seedlings”
t1“AM inoculation) experiment”
Claim · model-written summary
AM did not significantly change microaggregates.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“without significant change in microaggregates”
t0“Poplar Seedlings”
t1“AM inoculation) experiment”
Claim · model-written summary
AM increased soil total N 7.2% under optimum N.
- Treatment
- AM inoculationt1
- Outcome
- soil total nitrogen (TN)e0
- Direction
- increasee0
- Value
- 7.2%e0
- Qualifier
- optimume0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“causing soil total nitrogen (TN) to increase by 7.2% and 4.7% under optimum and high N levels, respectively”
t0“Poplar Seedlings”
t1“AM inoculation) experiment”
Claim · model-written summary
AM increased soil total N 4.7% under high N.
- Treatment
- AM inoculationt1
- Outcome
- soil total nitrogen (TN)e0
- Direction
- increasee0
- Value
- 4.7%e0
- Qualifier
- high N levelse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“causing soil total nitrogen (TN) to increase by 7.2% and 4.7% under optimum and high N levels, respectively”
t0“Poplar Seedlings”
t1“AM inoculation) experiment”
Claim · model-written summary
Relative AM contributions to N leaching increased with N level.
- Treatment
- N levelse0
- Outcome
- relative contributions of AM inoculation on N leachinge0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As the N levels increased, the relative contributions of AM inoculation on N leaching increased”
t0“Poplar Seedlings”
Claim · model-written summary
Plant physiological and soil variable contributions decreased with rising N.
- Treatment
- N levelst1
- Outcome
- contributions of plant physiological and soil variablese0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“however, the contributions of plant physiological and soil variables decreased”
t0“Poplar Seedlings”
t1“N levels increased”
Claim · model-written summary
SOC contributed importantly to leachate NH4+ and total N.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SOC had important contributions to NH4+ and total N in the leachate”
t0“Poplar Seedlings”
Claim · model-written summary
Root N concentration contributed more to NO3−.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“root N concentration had a higher contribution to NO3−”
t0“Poplar Seedlings”
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