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Research Article
Xiaomin Zhu
Chengdu Institute of Biology
Corresponding Author
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While multiple evidences have demonstrated that root-derived carbon (C) can profoundly regulate mineral nitrogen (N) cycling, it is still not elucidated whether tree roots differentially modulate the production and retention of ammonium (NH4+) versus nitrate (NO3-) through rhizosphere effect (RE). Using the 15N isotope labeling technique, we investigated how plant roots regulate the production and retention of NH4+ and NO3- via rhizosphere processes, and thus affect soil N availability in soils of two alpine coniferous forests. Synchronously, the activities of enzymes associated with N cycling and soil physicochemical properties in the rhizosphere and bulk soils were measured to explain the underlying mechanism. The results showed that roots induced greater positive REs of gross mineralization, microbial NH4+ immobilization, and dissimilatory nitrate reduction to ammonium (DNRA) to improve rhizosphere NH4+ availability. These positive REs can be attributed to the higher microbial biomass C and N and higher activities of N cycling-associated enzymes fueled by root-derived C. In contrast, the REs on NO3- production were negative, corresponding to the higher soil C:N ratio and higher microbial NH4+ immobilization in the rhizosphere soil than in the bulk soil, which led to relatively low NO3- availability in the rhizosphere. Collectively, our study provides field-based empirical evidence that plant roots can stimulate NH4+ production and immobilization, whereas they can limit NO3- production to achieve a high rhizosphere NH4+ supply in alpine coniferous forests. These findings provide comprehensive insights into how plants sustain their nutrition and growth by soil microbial N processes in their rhizosphere.
Keywords
Rhizosphere effect, mineral N production and retention, nutrient availability, alpine forests
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This preprint is under consideration at Biogeochemistry. A preprint is a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Learn more about In Review
Research Article
Xiaomin Zhu
Chengdu Institute of Biology
Corresponding Author
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
Peer Review Timeline
CURRENT STATUS: Under Review
Version 1
Posted 15 Feb, 2021
No community comments so far
First submitted
On 15 Jan, 2021
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
License:
This work is licensed under a CC BY 4.0 License. Read Full License
While multiple evidences have demonstrated that root-derived carbon (C) can profoundly regulate mineral nitrogen (N) cycling, it is still not elucidated whether tree roots differentially modulate the production and retention of ammonium (NH4+) versus nitrate (NO3-) through rhizosphere effect (RE). Using the 15N isotope labeling technique, we investigated how plant roots regulate the production and retention of NH4+ and NO3- via rhizosphere processes, and thus affect soil N availability in soils of two alpine coniferous forests. Synchronously, the activities of enzymes associated with N cycling and soil physicochemical properties in the rhizosphere and bulk soils were measured to explain the underlying mechanism. The results showed that roots induced greater positive REs of gross mineralization, microbial NH4+ immobilization, and dissimilatory nitrate reduction to ammonium (DNRA) to improve rhizosphere NH4+ availability. These positive REs can be attributed to the higher microbial biomass C and N and higher activities of N cycling-associated enzymes fueled by root-derived C. In contrast, the REs on NO3- production were negative, corresponding to the higher soil C:N ratio and higher microbial NH4+ immobilization in the rhizosphere soil than in the bulk soil, which led to relatively low NO3- availability in the rhizosphere. Collectively, our study provides field-based empirical evidence that plant roots can stimulate NH4+ production and immobilization, whereas they can limit NO3- production to achieve a high rhizosphere NH4+ supply in alpine coniferous forests. These findings provide comprehensive insights into how plants sustain their nutrition and growth by soil microbial N processes in their rhizosphere.
Figure 1
Figure 2
Figure 3
Figure 4
This is a list of supplementary files associated with this preprint. Click to download.
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