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Richard D. Bardgett - One of the best experts on this subject based on the ideXlab platform.
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Influence of Microbial activity on plant-Microbial Competition for organic and inorganic nitrogen
Plant and Soil, 2006Co-Authors: R. M. Dunn, Juha Mikola, Roland Bol, Richard D. BardgettAbstract:To investigate how the level of Microbial activity in grassland soils affects plant–Microbial Competition for different nitrogen (N) forms, we established microcosms consisting of a natural soil community and a seedling of one of two co-existing grass species, Anthoxanthum odoratum or Festuca rubra. We then stimulated the soil Microbial community with glucose in half of the microcosms and followed the transfer of added inorganic (15NH415NO3) and organic (glycine-2-13C-15N) N into Microbial and plant biomass. We found that microbes captured significantly more 15N in organic than in inorganic form and that glucose addition increased Microbial 15N capture from the inorganic source. Shoot and root biomass, total shoot N content and shoot and root 15N contents were significantly greater for A. odoratum than F. rubra, whereas F. rubra had higher shoot and root N concentrations. Where glucose was not added, A. odoratum had higher shoot 15N content with organic than with inorganic 15N addition, whereas where glucose was added, both species had higher shoot 15N content with inorganic than with organic 15N. Glucose addition had equally negative effects on shoot growth, total shoot N content, shoot and root N concentrations and shoot and root 15N content for both species. Both N forms produced significantly more shoot biomass and higher shoot N content than the water control, but the chemical form of N had no significant effect. Our findings suggest that plant species that are better in capturing nutrients from soil are not necessarily better in tolerating increasing Microbial Competition for nutrients. It also appears that intense Microbial Competition has more adverse effects on the uptake of organic than inorganic N by plants, which may potentially have significant implications for interspecific plant–plant Competition for N in ecosystems where the importance of organic N is high and some of the plant species specialize in use of organic N.
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Influence of Microbial activity on plant–Microbial Competition for organic and inorganic nitrogen
Plant and Soil, 2006Co-Authors: R. M. Dunn, Juha Mikola, Roland Bol, Richard D. BardgettAbstract:To investigate how the level of Microbial activity in grassland soils affects plant–Microbial Competition for different nitrogen (N) forms, we established microcosms consisting of a natural soil community and a seedling of one of two co-existing grass species, Anthoxanthum odoratum or Festuca rubra. We then stimulated the soil Microbial community with glucose in half of the microcosms and followed the transfer of added inorganic (15NH415NO3) and organic (glycine-2-13C-15N) N into Microbial and plant biomass. We found that microbes captured significantly more 15N in organic than in inorganic form and that glucose addition increased Microbial 15N capture from the inorganic source. Shoot and root biomass, total shoot N content and shoot and root 15N contents were significantly greater for A. odoratum than F. rubra, whereas F. rubra had higher shoot and root N concentrations. Where glucose was not added, A. odoratum had higher shoot 15N content with organic than with inorganic 15N addition, whereas where glucose was added, both species had higher shoot 15N content with inorganic than with organic 15N. Glucose addition had equally negative effects on shoot growth, total shoot N content, shoot and root N concentrations and shoot and root 15N content for both species. Both N forms produced significantly more shoot biomass and higher shoot N content than the water control, but the chemical form of N had no significant effect. Our findings suggest that plant species that are better in capturing nutrients from soil are not necessarily better in tolerating increasing Microbial Competition for nutrients. It also appears that intense Microbial Competition has more adverse effects on the uptake of organic than inorganic N by plants, which may potentially have significant implications for interspecific plant–plant Competition for N in ecosystems where the importance of organic N is high and some of the plant species specialize in use of organic N
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soil animals influence Microbial abundance but not plant Microbial Competition for soil organic nitrogen
Functional Ecology, 2004Co-Authors: Lisa Cole, Philip L. Staddon, Darren Sleep, Richard D. BardgettAbstract:1. In a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil Microbial properties and the short-term partitioning of a dual-labelled organic nitrogen source (glycine-2-13C-15N) between a grassland plant, Agrostis capillaris, and the soil Microbial biomass, to determine how soil fauna and their diversity influence plant–Microbial Competition for organic N. 2. We hypothesized that variations in the diversity of animals would influence the partitioning of 15N inputs between plants and the Microbial biomass, due to the effect of animal grazing on the Microbial biomass, and hence its ability to sequester N. 3. Certain individual species of Collembola influenced the Microbial community of the soil. Folsomia quadrioculata reduced Microbial biomass, whereas Mesaphorura macrochaeta enhanced arbuscular mycorrhizal (AM) colonization of A. capillaris roots. Effects of increasing species richness of microarthropods on Microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species. 4. Microbial uptake of added 15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on Microbial 15N. 5. Root and shoot uptake of 15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species, Ceratophysella denticulata, reduced root 15N capture when present in monoculture. We did not detect 13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization. 6. Our data suggest that, while single species and variations in diversity of microarthropods influence Microbial abundance in soil, there is no effect on Microbial or plant uptake of N. Overall, these data provide little support for the notion that Microbial-feeding soil animals are regulators of Microbial–plant Competition for N.
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Soil animals influence Microbial abundance, but not plant–Microbial Competition for soil organic nitrogen
Functional Ecology, 2004Co-Authors: Lisa Cole, Philip L. Staddon, Darren Sleep, Richard D. BardgettAbstract:1. In a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil Microbial properties and the short-term partitioning of a dual-labelled organic nitrogen source (glycine-2-13C-15N) between a grassland plant, Agrostis capillaris, and the soil Microbial biomass, to determine how soil fauna and their diversity influence plant–Microbial Competition for organic N. 2. We hypothesized that variations in the diversity of animals would influence the partitioning of 15N inputs between plants and the Microbial biomass, due to the effect of animal grazing on the Microbial biomass, and hence its ability to sequester N. 3. Certain individual species of Collembola influenced the Microbial community of the soil. Folsomia quadrioculata reduced Microbial biomass, whereas Mesaphorura macrochaeta enhanced arbuscular mycorrhizal (AM) colonization of A. capillaris roots. Effects of increasing species richness of microarthropods on Microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species. 4. Microbial uptake of added 15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on Microbial 15N. 5. Root and shoot uptake of 15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species, Ceratophysella denticulata, reduced root 15N capture when present in monoculture. We did not detect 13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization. 6. Our data suggest that, while single species and variations in diversity of microarthropods influence Microbial abundance in soil, there is no effect on Microbial or plant uptake of N. Overall, these data provide little support for the notion that Microbial-feeding soil animals are regulators of Microbial–plant Competition for N.
Lisa Cole - One of the best experts on this subject based on the ideXlab platform.
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soil animals influence Microbial abundance but not plant Microbial Competition for soil organic nitrogen
Functional Ecology, 2004Co-Authors: Lisa Cole, Philip L. Staddon, Darren Sleep, Richard D. BardgettAbstract:1. In a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil Microbial properties and the short-term partitioning of a dual-labelled organic nitrogen source (glycine-2-13C-15N) between a grassland plant, Agrostis capillaris, and the soil Microbial biomass, to determine how soil fauna and their diversity influence plant–Microbial Competition for organic N. 2. We hypothesized that variations in the diversity of animals would influence the partitioning of 15N inputs between plants and the Microbial biomass, due to the effect of animal grazing on the Microbial biomass, and hence its ability to sequester N. 3. Certain individual species of Collembola influenced the Microbial community of the soil. Folsomia quadrioculata reduced Microbial biomass, whereas Mesaphorura macrochaeta enhanced arbuscular mycorrhizal (AM) colonization of A. capillaris roots. Effects of increasing species richness of microarthropods on Microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species. 4. Microbial uptake of added 15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on Microbial 15N. 5. Root and shoot uptake of 15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species, Ceratophysella denticulata, reduced root 15N capture when present in monoculture. We did not detect 13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization. 6. Our data suggest that, while single species and variations in diversity of microarthropods influence Microbial abundance in soil, there is no effect on Microbial or plant uptake of N. Overall, these data provide little support for the notion that Microbial-feeding soil animals are regulators of Microbial–plant Competition for N.
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Soil animals influence Microbial abundance, but not plant–Microbial Competition for soil organic nitrogen
Functional Ecology, 2004Co-Authors: Lisa Cole, Philip L. Staddon, Darren Sleep, Richard D. BardgettAbstract:1. In a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil Microbial properties and the short-term partitioning of a dual-labelled organic nitrogen source (glycine-2-13C-15N) between a grassland plant, Agrostis capillaris, and the soil Microbial biomass, to determine how soil fauna and their diversity influence plant–Microbial Competition for organic N. 2. We hypothesized that variations in the diversity of animals would influence the partitioning of 15N inputs between plants and the Microbial biomass, due to the effect of animal grazing on the Microbial biomass, and hence its ability to sequester N. 3. Certain individual species of Collembola influenced the Microbial community of the soil. Folsomia quadrioculata reduced Microbial biomass, whereas Mesaphorura macrochaeta enhanced arbuscular mycorrhizal (AM) colonization of A. capillaris roots. Effects of increasing species richness of microarthropods on Microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species. 4. Microbial uptake of added 15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on Microbial 15N. 5. Root and shoot uptake of 15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species, Ceratophysella denticulata, reduced root 15N capture when present in monoculture. We did not detect 13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization. 6. Our data suggest that, while single species and variations in diversity of microarthropods influence Microbial abundance in soil, there is no effect on Microbial or plant uptake of N. Overall, these data provide little support for the notion that Microbial-feeding soil animals are regulators of Microbial–plant Competition for N.
Abdelhamid Ajbar - One of the best experts on this subject based on the ideXlab platform.
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On the Existence of Complex Dynamics in Pure and Simple Microbial Competition in Bioreactors
Arabian Journal for Science and Engineering, 2014Co-Authors: Abdelhamid Ajbar, Mohamed AsifAbstract:This paper examines the conditions necessary for the emergence of complex dynamic behavior in systems of pure and simple Microbial Competition in the chemostat under time-invariant feed conditions. In particular, we study the effect of variable yield coefficients and the presence of microorganisms in the inflow on the dynamics of such systems. This is accomplished through the study of a mathematical model of two Microbial populations competing for a single nutrient in a chemostat. A numerical investigation is carried out for a particular case for which the yield coefficient associated with one species is linearly dependent on the substrate, while the other species exists in the inflow. Both Monod and substrate inhibition growth rates are examined. The numerical investigation showed the existence of complex behavior in the model, characterized by the existence of stable quasi-periodic states resulting from torus bifurcations of limit cycles. Also, limit cycles may undergo period doubling leading to periodic states of increasing period. It seems that the variability of the yield coefficient of one species and the presence of at least one microorganism in the inflow are necessary conditions for complex dynamics to arise in pure and simple Competition in the chemostat.
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On the existence of chaotic behavior in simple and pure Microbial Competition: the role of Contois kinetics
Anziam Journal, 2014Co-Authors: Abdelhamid Ajbar, Mohamed Asif, Emad AliAbstract:Microbial Competition for nutrients is a common phenomenon that occurs between species inhabiting the same environment. Bioreactors are often used for the study of Microbial Competition since the number and type of Microbial species can be controlled, and the system can be isolated from other interactions that may occur between the competing species. A common type of Competition is the so-called simple and pure Competition when the Microbial populations interact in no other way except the Competition for a single rate-limiting nutrient that affects their growth rates. The issue whether simple and pure Competition under time invariant conditions can give rise to chaotic behavior has been unresolved for decades. Recently, Ajbar~\cite{Ajbar2012} showed, for the first time, that chaos can theoretically occur in these systems by analyzing the dynamics of a model where both competing species grow following the biomass dependent Contois model while the yield coefficients associated with the two species are substrate dependent. In this paper, we show that chaotic behavior can occur in a much simpler model of pure and simple Competition. We examine the case where only one species grows following Contois model with variable yield coefficient while the other species is allowed to grow following the simple Monod model with constant yield. We show that while the static behavior of the proposed model is quite simple, the dynamic behavior is complex and involves period doubling culminating to chaos. The proposed model could serve as a basis to re-examine the importance of Contois kinetics in predicting complex behavior in Microbial Competition. doi: 10.1017/S1446181113000345
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ON THE EXISTENCE OF CHAOTIC BEHAVIOUR IN PURE AND SIMPLE Microbial Competition: THE ROLE OF CONTOIS KINETICS
The ANZIAM Journal, 2013Co-Authors: Mohammad Asif, Emad Ali, Abdelhamid AjbarAbstract:Microbial Competition for nutrients is a common phenomenon that occurs between species inhabiting the same environment. Bioreactors are often used for the study of Microbial Competition since the number and type of Microbial species can be controlled, and the system can be isolated from other interactions that may occur between the competing species. A common type of Competition is the so-called “pure and simple” Competition, where the Microbial populations interact in no other way except the Competition for a single rate-limiting nutrient that affects their growth rates. The issue of whether pure and simple Competition under time-invariant conditions can give rise to chaotic behaviour has been unresolved for decades. The third author recently showed, for the first time, that chaos can theoretically occur in these systems by analysing the dynamics of a model where both competing species grow following the biomass-dependent Contois model while the yield coefficients associated with the two species are substrate-dependent. In this paper we show that chaotic behaviour can occur in a much simpler model of pure and simple Competition. We examine the case where only one species grows following the Contois model with variable yield coefficient while the other species is allowed to grow following the simple Monod model with constant yield. We show that while the static behaviour of the proposed model is quite simple, the dynamic behaviour is complex and involves period doubling culminating in chaos. The proposed model could serve as a basis to re-examine the importance of Contois kinetics in predicting complex behaviour in Microbial Competition.
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Study of complex dynamics in pure and simple Microbial Competition
Chemical Engineering Science, 2012Co-Authors: Abdelhamid AjbarAbstract:Abstract This paper examines the conditions for the emergence of complex dynamic behavior in systems of pure and simple Microbial Competition. A general unstructured model for the Competition is considered where the specific growth rates of both species are assumed to depend arbitrarily on both the substrate and the biomass. The model also assumes a general dependence of the yield coefficients on the substrate. It is shown that useful analytical conditions can be readily obtained that characterize the occurrence of periodic behavior in the chemostat. These results show that for a number of specific growth rates expressions, the existence of complex behavior is conditioned mainly by the variability of the yield coefficients. In particular, when the two species are assumed to grow following the biomass-dependent Contois model, the analysis uncovered complex behavior including chaos, which is a novelty for time invariant pure and simple Microbial Competition.
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Microbial Competition: Study of global branching phenomena
AIChE Journal, 2000Co-Authors: Abdelhamid Ajbar, Khalid AlhumaziAbstract:The stability characteristics of a bioreactor with cell recycle involving the Competition between Microbial cultures are investigated. The unstructured model, based on Andrew's inhibitory kinetics, involves the pure and simple Competition between two microorganisms for a single pollutant. The singularity theory used for this study allows an in-depth analysis of both the static and dynamic bifurcation mechanisms occurring in the system. The hysteresis with five solutions is the highest singularity the system can exhibit. With inhibitory kinetic expressions, the model can also predict self-sustained oscillations for a wide range of parameters. The analysis of clean feed conditions shows that the model cannot exhibit periodic behavior regardless of the growth kinetics model. Analytical criteria are also derived for the coexistence of the competing cultures and for the prevention of wash-out conditions. The stability characteristics for Monod kinetics, derived as a limiting case of the inhibitory kinetic expressions, are incorporated in the general framework offered by the singularity theory.
Darren Sleep - One of the best experts on this subject based on the ideXlab platform.
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soil animals influence Microbial abundance but not plant Microbial Competition for soil organic nitrogen
Functional Ecology, 2004Co-Authors: Lisa Cole, Philip L. Staddon, Darren Sleep, Richard D. BardgettAbstract:1. In a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil Microbial properties and the short-term partitioning of a dual-labelled organic nitrogen source (glycine-2-13C-15N) between a grassland plant, Agrostis capillaris, and the soil Microbial biomass, to determine how soil fauna and their diversity influence plant–Microbial Competition for organic N. 2. We hypothesized that variations in the diversity of animals would influence the partitioning of 15N inputs between plants and the Microbial biomass, due to the effect of animal grazing on the Microbial biomass, and hence its ability to sequester N. 3. Certain individual species of Collembola influenced the Microbial community of the soil. Folsomia quadrioculata reduced Microbial biomass, whereas Mesaphorura macrochaeta enhanced arbuscular mycorrhizal (AM) colonization of A. capillaris roots. Effects of increasing species richness of microarthropods on Microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species. 4. Microbial uptake of added 15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on Microbial 15N. 5. Root and shoot uptake of 15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species, Ceratophysella denticulata, reduced root 15N capture when present in monoculture. We did not detect 13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization. 6. Our data suggest that, while single species and variations in diversity of microarthropods influence Microbial abundance in soil, there is no effect on Microbial or plant uptake of N. Overall, these data provide little support for the notion that Microbial-feeding soil animals are regulators of Microbial–plant Competition for N.
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Soil animals influence Microbial abundance, but not plant–Microbial Competition for soil organic nitrogen
Functional Ecology, 2004Co-Authors: Lisa Cole, Philip L. Staddon, Darren Sleep, Richard D. BardgettAbstract:1. In a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil Microbial properties and the short-term partitioning of a dual-labelled organic nitrogen source (glycine-2-13C-15N) between a grassland plant, Agrostis capillaris, and the soil Microbial biomass, to determine how soil fauna and their diversity influence plant–Microbial Competition for organic N. 2. We hypothesized that variations in the diversity of animals would influence the partitioning of 15N inputs between plants and the Microbial biomass, due to the effect of animal grazing on the Microbial biomass, and hence its ability to sequester N. 3. Certain individual species of Collembola influenced the Microbial community of the soil. Folsomia quadrioculata reduced Microbial biomass, whereas Mesaphorura macrochaeta enhanced arbuscular mycorrhizal (AM) colonization of A. capillaris roots. Effects of increasing species richness of microarthropods on Microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species. 4. Microbial uptake of added 15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on Microbial 15N. 5. Root and shoot uptake of 15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species, Ceratophysella denticulata, reduced root 15N capture when present in monoculture. We did not detect 13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization. 6. Our data suggest that, while single species and variations in diversity of microarthropods influence Microbial abundance in soil, there is no effect on Microbial or plant uptake of N. Overall, these data provide little support for the notion that Microbial-feeding soil animals are regulators of Microbial–plant Competition for N.
Philip L. Staddon - One of the best experts on this subject based on the ideXlab platform.
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soil animals influence Microbial abundance but not plant Microbial Competition for soil organic nitrogen
Functional Ecology, 2004Co-Authors: Lisa Cole, Philip L. Staddon, Darren Sleep, Richard D. BardgettAbstract:1. In a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil Microbial properties and the short-term partitioning of a dual-labelled organic nitrogen source (glycine-2-13C-15N) between a grassland plant, Agrostis capillaris, and the soil Microbial biomass, to determine how soil fauna and their diversity influence plant–Microbial Competition for organic N. 2. We hypothesized that variations in the diversity of animals would influence the partitioning of 15N inputs between plants and the Microbial biomass, due to the effect of animal grazing on the Microbial biomass, and hence its ability to sequester N. 3. Certain individual species of Collembola influenced the Microbial community of the soil. Folsomia quadrioculata reduced Microbial biomass, whereas Mesaphorura macrochaeta enhanced arbuscular mycorrhizal (AM) colonization of A. capillaris roots. Effects of increasing species richness of microarthropods on Microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species. 4. Microbial uptake of added 15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on Microbial 15N. 5. Root and shoot uptake of 15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species, Ceratophysella denticulata, reduced root 15N capture when present in monoculture. We did not detect 13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization. 6. Our data suggest that, while single species and variations in diversity of microarthropods influence Microbial abundance in soil, there is no effect on Microbial or plant uptake of N. Overall, these data provide little support for the notion that Microbial-feeding soil animals are regulators of Microbial–plant Competition for N.
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Soil animals influence Microbial abundance, but not plant–Microbial Competition for soil organic nitrogen
Functional Ecology, 2004Co-Authors: Lisa Cole, Philip L. Staddon, Darren Sleep, Richard D. BardgettAbstract:1. In a microcosm experiment we examined the effects of individual species of microarthropods, and variations in microarthropod diversity of up to eight species, on soil Microbial properties and the short-term partitioning of a dual-labelled organic nitrogen source (glycine-2-13C-15N) between a grassland plant, Agrostis capillaris, and the soil Microbial biomass, to determine how soil fauna and their diversity influence plant–Microbial Competition for organic N. 2. We hypothesized that variations in the diversity of animals would influence the partitioning of 15N inputs between plants and the Microbial biomass, due to the effect of animal grazing on the Microbial biomass, and hence its ability to sequester N. 3. Certain individual species of Collembola influenced the Microbial community of the soil. Folsomia quadrioculata reduced Microbial biomass, whereas Mesaphorura macrochaeta enhanced arbuscular mycorrhizal (AM) colonization of A. capillaris roots. Effects of increasing species richness of microarthropods on Microbial biomass and AM colonization were detected, but these effects could be interpreted in relation to the presence or absence of individual species. 4. Microbial uptake of added 15N was not affected by the presence of any of the individual species of animal in the monoculture treatments. Similarly, increasing diversity of microarthropods had no detectable effect on Microbial 15N. 5. Root and shoot uptake of 15N was also largely unaffected by both single species and variations in diversity of microarthropods. However, one collembolan species, Ceratophysella denticulata, reduced root 15N capture when present in monoculture. We did not detect 13C in plant tissue under any experimental treatments, indicating that all N was taken up by plants after mineralization. 6. Our data suggest that, while single species and variations in diversity of microarthropods influence Microbial abundance in soil, there is no effect on Microbial or plant uptake of N. Overall, these data provide little support for the notion that Microbial-feeding soil animals are regulators of Microbial–plant Competition for N.