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Open AccessArticle

Arbuscular Mycorrhizal Fungi Mitigate Nitrogen Leaching under Poplar Seedlings

by Fengru Fang 1,†, Chunyan Wang 1,†, Fei Wu 2,3, Ming Tang 1,2,* and Russell Doughty 4
1
College of Forestry, Northwest A&F University, Yangling 712100, China
2
State Key Laboratory of Conservation and Utilization of Subtropical Agro-bioresources, Lingnan Guangdong Laboratory of Modern Agriculture, Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture South China Agricultural University, Guangzhou 510642, China
3
Key Laboratory of State Forestry and Grassland Administration on Forest Ecosystem Protection and Restoration of Poyang Lake Watershed, College of Forestry, Jiangxi Agricultural University, Nanchang 330045, China
4
Department of Microbiology and Plant Biology, Center for Spatial Analysis, University of Oklahoma, Norman, OK 73019, USA
*
Author to whom correspondence should be addressed.
Fengru Fang and Chunyan Wang contributed equally to this work.
Forests 2020, 11(3), 325; https://doi.org/10.3390/f11030325
Received: 23 February 2020 / Revised: 12 March 2020 / Accepted: 13 March 2020 / Published: 14 March 2020
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. View Full-Text
Keywords: arbuscular mycorrhizal fungi; poplar; nitrate and ammonium nitrogen leaching; AM fungi inoculation; plant biological activity; soil properties; relative contribution arbuscular mycorrhizal fungi; poplar; nitrate and ammonium nitrogen leaching; AM fungi inoculation; plant biological activity; soil properties; relative contribution
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Fang, F.; Wang, C.; Wu, F.; Tang, M.; Doughty, R. Arbuscular Mycorrhizal Fungi Mitigate Nitrogen Leaching under Poplar Seedlings. Forests 2020, 11, 325.

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