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  • 1
    ISSN: 1432-0789
    Keywords: Detrital food web ; Microbes ; Mineralization ; Soil fauna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Several experimental approaches have been taken to demonstrate the importance of soil fauna in nitrogen mineralization, but there have been difficulties interpreting the results. We have supplemented the experimental approach with theoretical calculations of nitrogen transformations in a shortgrass prairie. The calculations incorporate a wide array of information on decomposer organisms, including their feeding preferences, nitrogen contents, life spans, assimilation efficiencies, productio:assimilation ratios, decomposabilities, and population sizes. The results are estimates of nitrogen transfer rates through the detrital food web, including rates of N mineralization by bacteria, fungi, root-feeding nematodes, collembolans, fungal-feeding mites, fungal-feeding nematodes, flagellates, bacterial-feeding nematodes, amoebae, omnivorous nematodes, predaceous nematodes, nematode-feeding mites, and predaceous mites. Bacteria are estimated to mineralize the most N (4.5 g N m−2 year−1), followed by the fauna (2.9), and fungi (0.3). Bacterial-feeding amoebae and nematodes together account for over 83% of N mineralization by the fauna. The detrital food web in a shortgrass prairie is similar to that of a desert grassland. The shortgrass detrital web seems to be divided into bacteria- and fungus-based components, although these two branches are united at the level of predaceous nematodes and mites.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 5 (1987), S. 6-12 
    ISSN: 1432-0789
    Keywords: Inter- and intraspecific feeding ; Collembola ; Folsomia candida ; Acremonium sp. ; Paecilomyces varioti ; Penicillium citrinum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Selective grazing of fungi by soil microarthropods may affect decomposition rates of litter materials and the structure of microarthropod and fungal communities. We developed laboratory methods to assay feeding selectivity and investigated the preferences of the collembolan Folsomia candida on three fungi: Acremonium sp., Paecilomyces varioti, and Penicillium citrinum. F. candida showed stronger preference for Acremonium sp. than for P. varioti and P. citrinum. Oviposition site selection followed the same pattern. Actively metabolizing hyphae of Acremonium sp. and P. varioti were preferred over senescent hyphae, while spores of P. citrinum were preferred over active hyphae. If microarthropod preference for active hyphae is extensive, microarthropod regulation of decomposition could be more important than their biomass indicates. Furthermore, as the P. citrinum results indicate, mechanisms of microbial dissemination may include selective grazing.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 97 (1987), S. 333-344 
    ISSN: 1573-5036
    Keywords: Artificial soil ; Axenic roots ; Oats ; Rhizosphere dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A multiple split root chamber and artificial soil were developed which allowed for maintenance of axenic conditions and for the isolation of soil from specific regions of single roots. A sterile minirhizotron was used to measure patterns and rates of root extension under sterile conditions. Carbon and nitrogen distributions in the rhizosphere of sterile oat roots were measured in combination with rates of root elongation to calculate specific rates of rhizodeposition and ammonium nitrogen uptake. The highest rates of rhizodeposition C production and N depletion occurred at the root tip (first day segment). Rhizodeposited soluble and insoluble C compounds represented up to 50% of the standing root biomass C. Within 48 hours after root entry, levels of rhizosphere ammonium-N decreased by 40–50%. The results were summarized in a simple model of root growth, rhizodeposition, and NH 4 + −H uptake.
    Type of Medium: Electronic Resource
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