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Arbuscular mycorrhizal (AM) fungi facilitate inorganic N (NH4
+ or NO3
−) uptake by plants, but their role in N mobilization from organic sources is unclear. We hypothesized that arbuscular mycorrhizae
enhance the ability of a plant to use organic residues (ORs) as a source of N. This was tested under controlled glasshouse
conditions by burying a patch of OR in soil separated by 20-μm nylon mesh so that only fungal hyphae can pass through it.
The fate of the N contained in the OR patch, as influenced by Glomus claroideum, Glomus clarum, or Glomus intraradices over 24 weeks, was determined using 15N as a tracer. AM fungal species enhanced N mineralization from OR to different levels. N recovery and translocation to Russian
wild rye by hyphae reached 25% of mineralized N in G. clarum, which was most effective despite its smaller extraradical development in soil. Mobilization of N by G. clarum relieved plant N deficiency and enhanced plant growth. We show that AM hyphae modify soil functioning by linking plant growth
to N mineralization from OR. AM species enhance N mineralization differentially leading to species-specific changes in the
quality of the soil environment (soil C-to-N ratio) and structure of the soil microbial community. 相似文献
2.
Long-Term Phosphorus Fertilization Impacts Soil Fungal and Bacterial Diversity but not AM Fungal Community in Alfalfa 总被引:8,自引:0,他引:8
Soil function may be affected by cropping practices impacting the soil microbial community. The effect of different phosphorus
(P) fertilization rates (0, 20, or 40 kg P2O5 ha−1) on soil microbial diversity was studied in 8-year-old alfalfa monocultures. The hypothesis that P fertilization modifies
soil microbial community was tested using denaturing gradient gel electrophoresis and phospholipids fatty acid (PLFA) profiling
to describe soil bacteria, fungi, and arbuscular mycorrhizal (AM) fungi diversity. Soil parameters related to fertility (soil
phosphate flux, soluble P, moisture, phosphatase and dehydrogenase assays, and carbon and nitrogen content of the light fraction
of soil organic matter) were also monitored and related to soil microbial ribotype profiles. Change in soil P fertility with
the application of fertilizer had no effect on crop yield in 8 years, but on the year of this study was associated with shifts
in the composition of fungal and bacterial communities without affecting their richness, as evidenced by the absence of effect
on the average number of ribotypes detected. However, variation in soil P level created by a history of differential fertilization
did not significantly influence AM fungi ribotype assemblages nor AM fungi biomass measured with the PLFA 16:1ω5. Fertilization
increased P flux and soil soluble P level but reduced soil moisture and soil microbial activity, as revealed by dehydrogenase
assay. Results suggest that soil P fertility management could influence soil processes involving soil microorganisms. Seasonal
variations were also recorded in microbial activity, soil soluble P level as well as in the abundance of specific bacterial
and fungal PLFA indicators of soil microbial biomass. 相似文献
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