N addition undermines N supplied by arbuscular mycorrhizal fungi to native perennial grasses

Jach-Smith, Laura C.; Jackson, Randall D.

doi:10.1016/j.soilbio.2017.10.009

Cited by 43 publications

(25 citation statements)

References 66 publications

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“…However, no yield advantage was achieved with this high level of fertilization at ARL (Jach‐Smith and Jackson ), which would indicate that plants were not N limited at the ARL site. Plant aboveground biomass and total N content was reported in Jach‐Smith and Jackson (), where a yield gain was achieved only at KBS with the N addition treatments. N content increased with N application rate, but this is assumed to be N luxury consumption (an increase in plant N concentration that is not used for growth) since there was no yield gain.…”

Section: Resultsmentioning

confidence: 97%

Inorganic N addition replaces N supplied to switchgrass (Panicum virgatum) by arbuscular mycorrhizal fungi

Jach-Smith

Jackson

2020

Ecological Applications

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Arbuscular mycorrhizal fungi (AMF) provide many benefits in agroecosystems including improved soil tilth, carbon sequestration, and water and nutrient transfer to plants. AMF are known to affect plant nitrogen (N) dynamics and transfer N to plants, but there have been few studies addressing whether the amount of N transferred to plants by AMF is agronomically relevant. We used δ15N natural abundance methods and δ15N mass balance equations to estimate the amount of plant N derived from AMF transfer in perennial grasses managed for bioenergy production under different N addition treatments (0, 56, and 196 kg N/ha). Differentiation of δ15N among plant, soil N, and AMF pools was higher than anticipated leading to calculations of 34–55% of plant N transferred by AMF in the treatments receiving no N addition to 6–22% of plant N transferred to plants in high‐N addition treatments. AMF extra‐radical hyphae biomass was significantly reduced in the high‐N (196 kg N/ha) addition treatments, which was negatively correlated to enriched plant δ15N. Our results suggest that N addition decreases AMF N transfer to plants. When N was limiting to plant growth, AMF supplied agronomically significant amounts of plant N, and a higher proportion of overall plant N. Because differentiation between N pools was greater than expected, stable isotope measurements can be used to estimate N transfer to AMF plant hosts.

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Section: Resultsmentioning

confidence: 97%

Inorganic N addition replaces N supplied to switchgrass (Panicum virgatum) by arbuscular mycorrhizal fungi

Jach-Smith

Jackson

2020

Ecological Applications

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“…The ability of the mycorrhizal network to transfer N from the donor to recipient plant varies from 0-80% [69]. However, much elevated N-fertilization did not increase nutrient transfer and plant biomass because plants may face other limitations, like water, light or space, that limit their growth [70]. However, at severe N deficiency, the AM fungi might consume additional N sources for their own needs, and as a result, there is little or no N transfer to the plants [71].…”

Section: Discussionmentioning

confidence: 99%

Formation of Common Mycorrhizal Networks Significantly Affects Plant Biomass and Soil Properties of the Neighboring Plants under Various Nitrogen Levels

et al. 2020

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Common mycorrhizal networks (CMNs) allow the transfer of nutrients between plants, influencing the growth of the neighboring plants and soil properties. Cleistogene squarrosa (C. squarrosa) is one of the most common grass species in the steppe ecosystem of Inner Mongolia, where nitrogen (N) is often a key limiting nutrient for plant growth, but little is known about whether CMNs exist between neighboring individuals of C. squarrosa or play any roles in the N acquisition of the C. squarrosa population. In this study, two C. squarrosa individuals, one as a donor plant and the other as a recipient plant, were planted in separate compartments in a partitioned root-box. Adjacent compartments were separated by 37 µm nylon mesh, in which mycorrhizal hyphae can go through but not roots. The donor plant was inoculated with arbuscular mycorrhizal (AM) fungi, and their hyphae potentially passed through nylon mesh to colonize the roots of the recipient plant, resulting in the establishment of CMNs. The formation of CMNs was verified by microscopic examination and 15 N tracer techniques. Moreover, different levels of N fertilization (N0 = 0, N1 = 7.06, N2 = 14.15, N3 = 21.19 mg/kg) were applied to evaluate the CMNs' functioning under different soil nutrient conditions. Our results showed that when C. squarrosa-C. squarrosa was the association, the extraradical mycelium transferred the 15 N in the range of 45-55% at different N levels. Moreover, AM fungal colonization of the recipient plant by the extraradical hyphae from the donor plant significantly increased the plant biomass and the chlorophyll content in the recipient plant. The extraradical hyphae released the highest content of glomalin-related soil protein into the rhizosphere upon N2 treatment, and a significant positive correlation was found between hyphal length and glomalin-related soil proteins (GRSPs). GRSPs and soil organic carbon (SOC) were significantly correlated with mean weight diameter (MWD) and helped in the aggregation of soil particles, resulting in improved soil structure. In short, the formation of CMNs in this root-box experiment supposes the existence of CMNs in the typical steppe plants, and CMNs-mediated N transfer and root colonization increased the plant growth and soil properties of the recipient plant.

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“…This is almost certainly an underestimate, because our mass balance calculation does not include N lost by leaching (approximately 2.7 kg N ha -1 yr -1 , [ 18 ]) or from denitrification. While it is possible that some of this N might be supplied through net mineralization of soil organic N stores, especially since switchgrass and other perennial grasses are adept at recovering N from soils through their association with mycorrhizal fungi [ 57 , 58 ], we have seen no evidence of soil N depletion at this site [ 18 , 59 ], consistent with long-term gains in soil organic matter commonly observed when cultivated soils are converted from annual to perennial vegetation (e.g., [ 60 , 61 ]). The total N deficit is equivalent to ~7% of the total soil N pool, which is within detection limits if soil organic matter were the sole source of the missing N [ 62 ].…”

Section: Discussionmentioning

confidence: 99%

Associative nitrogen fixation (ANF) in switchgrass (Panicum virgatum) across a nitrogen input gradient

et al. 2018

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Associative N fixation (ANF), the process by which dinitrogen gas is converted to ammonia by bacteria in casual association with plants, has not been well-studied in temperate ecosystems. We examined the ANF potential of switchgrass (Panicum virgatum L.), a North American prairie grass whose productivity is often unresponsive to N fertilizer addition, via separate short-term 15N2 incubations of rhizosphere soils and excised roots four times during the growing season. Measurements occurred along N fertilization gradients at two sites with contrasting soil fertility (Wisconsin, USA Mollisols and Michigan, USA Alfisols). In general, we found that ANF potentials declined with long-term N addition, corresponding with increased soil N availability. Although we hypothesized that ANF potential would track plant N demand through the growing season, the highest root fixation rates occurred after plants senesced, suggesting that root diazotrophs exploit carbon (C) released during senescence, as C is translocated from aboveground tissues to roots for wintertime storage. Measured ANF potentials, coupled with mass balance calculations, suggest that ANF appears to be an important source of N to unfertilized switchgrass, and, by extension, to temperate grasslands in general.

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N addition undermines N supplied by arbuscular mycorrhizal fungi to native perennial grasses

Cited by 43 publications

References 66 publications

Inorganic N addition replaces N supplied to switchgrass (Panicum virgatum) by arbuscular mycorrhizal fungi

Inorganic N addition replaces N supplied to switchgrass (Panicum virgatum) by arbuscular mycorrhizal fungi

Formation of Common Mycorrhizal Networks Significantly Affects Plant Biomass and Soil Properties of the Neighboring Plants under Various Nitrogen Levels

Associative nitrogen fixation (ANF) in switchgrass (Panicum virgatum) across a nitrogen input gradient

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