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  • 1
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical biology 28 (1990), S. 225-235 
    ISSN: 1432-1416
    Keywords: Logistic growth ; Age-dependent model ; Global stability ; Oscillation ; Boundedness of solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We study the large time behaviour of a nonlinear population model with a general logistic term. It is proved that every solution must have a limit when time becomes infinite. We present conditions that guarantee the boundedness of the solution. Furthermore, we prove that in general no oscillation is possible for the total number of population. This is in sharp contrast to the linear case.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 170 (1995), S. 131-140 
    ISSN: 1573-5036
    Keywords: crop productivity ; cropping systems ; Glomales ; soil ecology ; vesicular arbuscular mycorrhizal fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Mycorrhizal fungi are present in all arable soils and colonize nearly all crops and weed pests of crops. They may be involved as mutualists or pathogens of crops in well known but poorly understood phenomena such as crop rotation and green manure effects on soil productivity. Crop change effects on mycorrhizal fungal community parameters were evaluated in three field experiments. In Experiment 1, soybean (Glycine max (L.) Merr. cv. Douglas) was grown continuously or rotated with corn (Zea mays L.), milo (Sorghum bicolor (L.) Moench), or fescue (Festuca arundinacea Schreb cv. Johnstone) for two years, then soybean was grown on all plots. Continuous soybean plots were dominated byGigaspora spp., while rotated crops were dominated byGlomus spp. Differences in communities and community indices of continuous soybean and rotated plots were reduced after growing soybeans on rotated plots. In Experiment 2, a fescue sod was plowed and pearl millet (Pennisetum americanum Leeke) or crabgrass (Digitaria sanguinalis (L.) Scop.) grown. Both hosts resulted in great changes in populations of individual species, decreases in community dominance, and increases in community diversity and equitability. Crabgrass also resulted in reduced species richness. In Experiment 3, tobacco (Nicotiana tabacum L.) or fescue was planted on adjacent tracts of land with a long-term history of either fescue (30 yr) or sorghum-sudangrass (Sorghum bicolor (L.) Moench. ×S. sudanense (Piper) Staph.) (3 yr). The long-term cropping history had major effects on the mycorrhizal fungal communities which were related to the expression of mycorrhizal stunt disease of tobacco. Changes occurred in these communities in response to either current-season crop. These experiments suggest that crop rotation causes large changes in mycorrhizal fungal communities, that these changes may be involved in the rotation effect on soil productivity, and that design of cropping systems should take mycorrhizal fungal communities into consideration.
    Type of Medium: Electronic Resource
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