Negative relationship between microbial biomass and root amount in topsoil of a renovated grassland

Okano, S.; Sato, Kenzi; Inoue, Kazuhide

doi:10.1080/00380768.1991.10415009

Cited by 11 publications

(8 citation statements)

References 17 publications

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“…This may be explained by the varied response of microorganisms to growing plants. The microbiota, and thus C mic , is usually enhanced in the root zone of plants due to utilization of substrates released from the rhizosphere (Lynch and Panting, 1980;Martens, 1990); however, reduction of the C mic due to root competition has also been detected (Okano et al, 1991;Raghubanshi, 1991). Two different effects of the plant cover on C mic , as in the present study, could therefore be observed depending on the predominance of two opposing forces, rhizosphere stimulation and nutrient immobilization.…”

Section: Resultsmentioning

confidence: 56%

Changes in soil microbial biomass and aggregate stability following burning and soil rehabilitation

et al. 2004

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Section: Resultsmentioning

confidence: 56%

Changes in soil microbial biomass and aggregate stability following burning and soil rehabilitation

et al. 2004

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“…The varying responses could reflect the ability of plants, either to enhance microbes through resource addition (Roder et al . 1988; Smith & Paul 1990), or to suppress them through nutrient immobilisation (Okano et al . 1991).…”

Section: Biotic Interactions and Microfood‐web Regulation And Functionmentioning

confidence: 99%

Trophic relationships in the soil microfood‐web: predicting the responses to a changing global environment

Wardle

Verhoef

Clarholm

1998

Global Change Biology

110

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In this article, we evaluate how global environmental change may affect microfood‐webs and trophic interactions in the soil, and the implications of this at the ecosystem level. First we outline how bottom‐up (resource control) and top‐down (predation‐control) forces regulate food‐web components. Food‐web components can respond either positively or negatively to shifts in NPP resulting from global change, thus creating difficulties in developing general principles about the response of soil biota to global change phenomena. We also demonstrate that top‐down effects can be important in soil food‐webs, creating negative feed‐backs which may partially counter bottom‐up effects. Secondly, we determine how soil food‐webs and the processes they regulate respond to various global change phenomena. Enhanced atmospheric CO2 levels can have two main effects on plants which are relevant for the soil food‐web, i.e. enhanced NPP (often positive) and diminished organic matter quality (with negative effects, at least in the short term). Climate change effects resulting from elevated CO2 levels may be mainly secondary through alteration of vegetation, as shown by examples. Intensification of land management is usually associated with greater disturbance, which alters soil food‐web composition and key processes; this is particularly apparent in comparisons of conventionally tilled and nontilled agroecosystems. Global change involves shifts in plant species composition and diversity, possibly affecting soil food‐webs; we interpret this in terms of theories relating biodiversity to ecosystem function. We conclude that a more detailed understanding of interactions between NPP, soil organic matter and components of the soil food‐web, as well as their regulation of biogeochemical processes and ultimately ecosystem‐level properties, is essential in better understanding long‐term aspects of global change phenomena.

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“…5). This stimulation is likely to result from the substrate added in decomposing large rosette leaves, or reduced competitive effects of the other pasture components in the W zone (Okano et al, 1989(Okano et al, , 1991.…”

Section: Field Experimentsmentioning

confidence: 99%

Interference effects of the invasive plantCarduus nutans L. against the nitrogen fixation ability ofTrifolium repens L.

et al. 1994

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Carduus nutans L. is an invasive pasture/grassland species which may undergo rapid population growth through positive feedback. Plants of C. nutans produce a vegetative rosette, and after several months produce stems containing flower-heads, during which time the rosette leaves die and decompose. We investigated the influence of C. nutans on the nitrogen-fixation ability of Trifolium repens L. in three experiments. The first experiment was set up in a "mixture" design, and demonstrated that seedlings of T. repens were more susceptible to competition with other T. repens seedlings than to C. nutans seedlings. Nodule numbers and acetylene reduction per unit root, and acetylene reduction per unit nodules were adversely affected by increasing T. repens, but not C. nutansdensities. The second experiment was of an additive design, with separate partitions to isolate above-ground and belowground interference. Flowering C. nutans plants strongly inhibited T. repens root growth, nodulation and acetylene reduction, but usually only when shoot interference was permitted. This appears to be due to decomposition of rosette leaves, which was maximal at this stage. The third experiment involved monitoring effects of tagged C. nutans individuals against T. repens in the field. This experiment showed that acetylene reduction was severely influenced by flowering C. nutans (when rosette leaves were decomposing), even when only mild reduction of T. repens growth was observed, and these effects persisted for some months after the C. nutans plants had died. The results of these experiments in combination suggest that decomposing rosette leaves have a strong potential to inhibit T. repens nitrogen fixation. It appears that allelopathy is involved, since alternative explanations (e.g. root competition by C. nutans; effects of C. nutans on soil moisture, microbial nutrient immobilisation and light availability; facilitation of herbivores by C. nutans) can be effectively discounted. Although invasive species are often assumed to be associated with soil nitrogen build-up, we believe that some invasive species such as C. nutans have the potential to induce long-term decline of soil nitrogen input.

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Negative relationship between microbial biomass and root amount in topsoil of a renovated grassland

Cited by 11 publications

References 17 publications

Changes in soil microbial biomass and aggregate stability following burning and soil rehabilitation

Changes in soil microbial biomass and aggregate stability following burning and soil rehabilitation

Trophic relationships in the soil microfood‐web: predicting the responses to a changing global environment

Interference effects of the invasive plantCarduus nutans L. against the nitrogen fixation ability ofTrifolium repens L.

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