Modelling the competition for nitrogen between plants and microflora as a function of soil heterogeneity

Korsæth, Audun; Molstad, Lars; Bakken, Lars R.

doi:10.1016/s0038-0717(00)00132-2

Cited by 60 publications

(30 citation statements)

References 26 publications

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“…In our experiments vegetation presence had a negative influence on the denitrification rate. An explanation could be competition for nitrate by plant roots (Korsaeth et al 2001). The fact that in the unvegetated zone nitrate concentration in the surface water was higher than in the vegetated zone also supports that explanation.…”

Section: Discussionmentioning

confidence: 65%

Nutrient Cycling and Retention Along a Littoral Gradient in a Dutch Shallow Lake in Relation to Water Level Regime

Sollie

Verhoeven

2008

Water Air Soil Pollut

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Littoral zones are characterized by gradients in depth and vegetation biomass, influencing nutrient retention capacity. A field experiment was conducted in a Phragmites australis dominated littoral zone to investigate nutrient retention and its effect on surface water quality. Measurements were done in mesocosms where water levels could be manipulated. Nutrient status was investigated along a gradient perpendicular to the shore during two growing seasons, one with a stable water level and one with a gradually decreasing water level. Nutrient concentrations in sediment, soil pore water and surface water were significantly lower in the vegetated than in the unvegetated zone. The negative correlations of nutrients in sediment and water, with nutrient contents of the vegetation suggest a direct effect of the vegetation. Nutrient uptake and biomass of the vegetation was higher in continuously flooded soils than in seasonally emerging sediments higher along the littoral gradient, probably due to the increased salinity in drained zones. Denitrification rate was highest in the unvegetated zone and was positively related to water level. Flooded littoral zones did result in a higher nutrient retention than drained zones. On small scale, for an optimal nutrient retention a fluctuating regime is not necessarily better suited than a stable water level, but on a larger scale it can substantially increase the width of the vegetated zone. It is important to optimize conditions for helophyte growth since the positive effect of vegetation on nutrient retention, at least at local scale, has been demonstrated in this study.

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Section: Discussionmentioning

confidence: 65%

Nutrient Cycling and Retention Along a Littoral Gradient in a Dutch Shallow Lake in Relation to Water Level Regime

Sollie

Verhoeven

2008

Water Air Soil Pollut

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“…Documentation by GFP reporters of the number and distribution of soil microsites diffusionally isolated from plant root uptake is in itself an interesting result. Such heterogeneity may be very important for explaining the ability of microbes and plants to efficiently compete with one another for inorganic nitrogen (14,25).…”

Section: Discussionmentioning

confidence: 99%

Two Novel Bacterial Biosensors for Detection of Nitrate Availability in the Rhizosphere

DeAngelis

Firestone

et al. 2005

Appl Environ Microbiol

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The nitrate-regulated promoter of narG in Escherichia coli was fused to promoterless ice nucleation (inaZ) and green fluorescent protein (GFP) reporter genes to yield the nitrate-responsive gene fusions in plasmids pNice and pNgfp, respectively. While the promoter of narG is normally nitrate responsive only under anaerobic conditions, the L28H-fnr gene was provided in trans to enable nitrate-dependent expression of these reporter gene fusions even under aerobic conditions in both E. coli DH5␣ and Enterobacter cloacae EcCT501R. E. cloacae and E. coli cells containing the fusion plasmid pNice exhibited more than 100-fold-higher ice nucleation activity in cultures amended with 10 mM sodium nitrate than in nitrate-free media. The GFP fluorescence of E. cloacae cells harboring pNgfp was uniform at a given concentration of nitrate and increased about 1,000-fold when nitrate increased from 0 to 1 mM. Measurable induction of ice nucleation in E. cloacae EcCT501R harboring pNice occurred at nitrate concentrations of as low as 0.1 M, while GFP fluorescence was detected in cells harboring pNgfp at about 10 M. In the rhizosphere of wild oat (Avena fatua), the whole-cell bioreporter E. cloacae(pNgfp) or E. cloacae(pNice) expressed significantly higher GFP fluorescence or ice nucleation activity when the plants were grown in natural soils amended with nitrate than in unamended natural soils. Significantly lower nitrate abundance was detected by the E. cloacae(pNgfp) reporter in the A. fatua rhizosphere compared to in bulk soil, indicating plant competition for nitrate. Ice-and GFP-based bacterial sensors thus are useful for estimating nitrate availability in relevant microbial niches in natural environments.

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“…Microorganisms can compete effectively with plants for these nutrients (Schimel et al 1989;Zak et al 1990). Applied inorganic N, for example, is rapidly taken up by the soil microbial biomass (Nannipieri et al 1990) which can be limited by nutrients and not just C (Kaye and Hart 1997;Wang and Bakken 1997), although the outcome of the plant-microorganism competition depends on the spatial heterogeneity of the system (Korsaeth et al 2001). Previous work on cut, rather than grazed, grassland showed clearly that both microbial biomass P and the biomass C:P ratio were sensitive to longterm (>100 years) fertiliser regimes (He et al 1997).…”

Section: Introductionmentioning

confidence: 99%

C:N:P stoichiometry and nutrient limitation of the soil microbial biomass in a grazed grassland site under experimental P limitation or excess

2012

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Introduction: The availability of essential nutrients, such as nitrogen (N) and phosphorus (P), can feedback on soil carbon (C) and the soil microbial biomass. Natural cycles can be supplemented by agricultural fertiliser addition, and we determined whether the stoichiometry and nutrient limitation of the microbial biomass could be affected by an unbalanced nutrient supply.Methods: Samples were taken from a long-term trial (in effect since 1968) with annual applications of 0, 15 and 30 kg P ha −1 with constant N and potassium. Soil and microbial biomass CNP contents were measured and nutrient limitation assessed by substrate-induced respiration. Linear regression and discriminant analyses were used to identify the variables explaining nutrient limitation. Results: Soil and biomass CNP increased with increasing P fertiliser, and there was a significant, positive, correlation between microbial biomass P and biomass C, apart from at the highest level of P fertilisation when the microbial biomass was over-saturated with P. The molar ratios of C:N:P in the microbial biomass remained constant (homeostatic) despite large changes in the soil nutrient ratios. Microbial growth was generally limited by C and N, except in soil with no added P when C and P were the main limiting nutrients. C, N and P, however, did not explain all the growth limitation on the soils with no added P. Conclusions: Increased soil C and N were probably due to increased net primary production. Our results confirm that C:N:P ratios within the microbial biomass were constrained (i.e. homeostatic) under near optimum soil conditions. Soils with no added P were characterised by strong microbial P limitation and soils under high P by over-saturation of microorganisms with P. Relative changes in biomass C:P can be indicative of nutrient limitation within a site.

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Modelling the competition for nitrogen between plants and microflora as a function of soil heterogeneity

Cited by 60 publications

References 26 publications

Nutrient Cycling and Retention Along a Littoral Gradient in a Dutch Shallow Lake in Relation to Water Level Regime

Nutrient Cycling and Retention Along a Littoral Gradient in a Dutch Shallow Lake in Relation to Water Level Regime

Two Novel Bacterial Biosensors for Detection of Nitrate Availability in the Rhizosphere

C:N:P stoichiometry and nutrient limitation of the soil microbial biomass in a grazed grassland site under experimental P limitation or excess

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