Effects of carbohydrate application on diazotroph populations and nitrogen availability in grass swards established in garden waste compost

Keeling, A.A.; Cook, Jamie A.; Wilcox, Andrew

doi:10.1016/s0960-8524(98)00055-8

Cited by 23 publications

(13 citation statements)

References 26 publications

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“…In general, the availability of labile C stimulates N fixation (7,26,27), although not always (25). Nitrogen fixation can also be inhibited (51) or stimulated (40) by available N in the soil.…”

Section: Discussionmentioning

confidence: 99%

“…Field sampling for the present study was conducted in long-term levels-of-growing-stock (LOGS) experimental installations located on Vancouver Island, British Columbia, Canada. The periodically thinned second-growth Douglas-fir plantation near Shawnigan Lake, British Columbia (Shawnigan Lake LOGS site; site A), and a nearby clear-cut plot were sampled on 25 (1,14) provide more detailed information about the sites used in the present study.…”

Section: Methodsmentioning

confidence: 99%

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Quantification of Nitrogen Reductase and Nitrite Reductase Genes in Soil of Thinned and Clear-Cut Douglas-Fir Stands by Using Real-Time PCR

Levy‐Booth

Winder

2010

Appl Environ Microbiol

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The abundance of nifH, nirS, and nirK gene fragments involved in nitrogen (N) fixation and denitrification in thinned second-growth Douglas-fir (Pseudotsuga menziesii subsp. menziesii [Mirb.] Franco) forest soil was investigated by using quantitative real-time PCR. Prokaryotic N cycling is an important aspect of N availability in forest soil. The abundance of universal nifH, Azotobacter sp.-specific nifH (nifH-g1), nirS, and nirK gene fragments in unthinned control and 30, 90, and 100% thinning treatments were compared at two long-term research sites on Vancouver Island, Canada. The soil was analyzed for organic matter (OM), total carbon (C), total N, NH 4 -N, NO 3 -N, and phosphorus (P). The soil horizon accounted for the greatest variation in nutrient status, followed by the site location. The 30% thinning treatment was associated with significantly greater nifH-g1 abundance than the control treatment in one site; at the same site, nirS in the mineral soil horizon was significantly reduced by thinning. The abundance of nirS genes significantly correlated with the abundance of nirK genes. In addition, significant correlations were observed between nifH-g1 abundance and C and N in the organic horizon and between nirS and nirK and N in the mineral horizon. Overall, no clear influence of tree thinning on nifH, nirS, and nirK was observed. However, soil OM, C, and N were found to significantly influence N-cycling gene abundance.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Quantification of Nitrogen Reductase and Nitrite Reductase Genes in Soil of Thinned and Clear-Cut Douglas-Fir Stands by Using Real-Time PCR

Levy‐Booth

Winder

2010

Appl Environ Microbiol

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“…In contrast, the effects of C and N quantity and quality are less consistent. Increases in the availability of labile C generally stimulate N fixation (O'Toole and Knowles, 1973;Keeling et al, 1998;Burgmann et al, 2005;Kondo and Yasuda, 2003a, b), but in other cases have little or no effect (Brouzes et al, 1969;Roper and Smith, 1991;Keeling et al, 1998). Likewise, N availability can have either stimulatory (Azam et al, 1988;Poly et al, 2001) or inhibitory (Koteva et al, 1992;Tan et al, 2003) effects.…”

Section: Introductionmentioning

confidence: 99%

Evidence for the functional significance of diazotroph community structure in soil

2008

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Microbial ecologists continue to seek a greater understanding of the factors that govern the ecological significance of microbial community structure. Changes in community structure have been shown to have functional significance for processes that are mediated by a narrow spectrum of organisms, such as nitrification and denitrification, but in some cases, functional redundancy in the community seems to buffer microbial ecosystem processes. The functional significance of microbial community structure is frequently obscured by environmental variation and is hard to detect in short-term experiments. We examine the functional significance of free-living diazotrophs in a replicated long-term tillage experiment in which extraneous variation is minimized and N-fixation rates can be related to soil characteristics and diazotroph community structure. Soil characteristics were found to be primarily impacted by tillage management, whereas N-fixation rates and diazotroph community structure were impacted by both biomass management practices and interactions between tillage and biomass management. The data suggest that the variation in diazotroph community structure has a greater impact on N-fixation rates than do soil characteristics at the site. N-fixation rates displayed a saturating response to increases in diazotroph community diversity. These results show that the changes in the community structure of free-living diazotrophs in soils can have ecological significance and suggest that this response is related to a change in community diversity.

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“…Anthropogenic activities have led to increased nitrogen fertilization and atmospheric deposition of bioavailable nitrogen (NH 4 ϩ , NO 3 Ϫ ), thus reducing the extent of N limitation in many ecosystems. On the other hand, N fixation activities of free-living microorganisms can be induced or stimulated locally by increasing the C/N ratios or availability of suitable easily degradable C sources (21,24,43), such as decaying plant material or root exudates (40). Nitrogen-limited conditions may also be induced after application of organic amendments in agricultural systems (e.g., after straw incorporation into soil) (33,46).…”

mentioning

confidence: 99%

“…Although strategies based on deliberate release (4,22) or stimulation of the natural diazotroph population (20,21) have yielded variable results in the past, such strategies have considerable potential (21,22). In order to advance research in this area, development of tools that allow in situ studies of gene expression and activities in the soil matrix is required.…”

mentioning

confidence: 99%

mRNA Extraction and Reverse Transcription-PCR Protocol for Detection of nifH Gene Expression by Azotobacter vinelandii in Soil

Bürgmann

Widmer

Sigler

et al. 2003

Appl Environ Microbiol

153

100

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The study of free-living nitrogen-fixing organisms in bulk soil is hampered by the great diversity of soil microbial communities and the difficulty of relating nitrogen fixation activities to individual members of the diazotroph populations. We developed a molecular method that allows analysis of nifH mRNA expression in soil in parallel with determinations of nitrogen-fixing activity and bacterial growth. In this study, Azotobacter vinelandii growing in sterile soil and liquid culture served as a model system for nifH expression, in which sucrose served as the carbon source and provided nitrogen-limited conditions, while amendments of NH 4 NO 3 were used to suppress nitrogen fixation. Soil RNA extraction was performed with a new optimized direct extraction protocol that yielded nondegraded total RNA. The RNA extracts were of high purity, free of DNA contamination, and allowed highly sensitive and specific detection of nifH mRNA by a reverse transcription-PCR. The level of nifH gene expression was estimated by PCR amplification of reverse-transcribed nifH mRNA fragments with A. vinelandii-specific nifH primers. This new approach revealed that nifH gene expression was positively correlated with bulk nitrogen fixation activity in soil (r 2 ‫؍‬ 0.72) and in liquid culture (r 2 ‫؍‬ 0.84) and therefore is a powerful tool for studying specific regulation of gene expression directly in the soil environment.

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Effects of carbohydrate application on diazotroph populations and nitrogen availability in grass swards established in garden waste compost

Cited by 23 publications

References 26 publications

Quantification of Nitrogen Reductase and Nitrite Reductase Genes in Soil of Thinned and Clear-Cut Douglas-Fir Stands by Using Real-Time PCR

Quantification of Nitrogen Reductase and Nitrite Reductase Genes in Soil of Thinned and Clear-Cut Douglas-Fir Stands by Using Real-Time PCR

Evidence for the functional significance of diazotroph community structure in soil

mRNA Extraction and Reverse Transcription-PCR Protocol for Detection of nifH Gene Expression by Azotobacter vinelandii in Soil

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