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  • Microbial biomass  (3)
  • Neural control of respiration  (2)
  • Soil texture  (2)
  • 1
    ISSN: 1432-0789
    Schlagwort(e): Phospholipids ; Microbial biomass ; Phosphatase ; Cropping systems ; Long-term experiments Prairie
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In agricultural ecosystems that have had consistent cropping histories, standard microbial methods may be used to evaluate past and present practices. Our objective was to evaluate several microbial methods that best indicate cropping histories and soil quality on long-term plots. We selected soil microbial carbon (C), phospholipid analyses, direct counts of total fungal and bacterial biomass, and soil enzymes (phosphatases) to measure direct and indirect microbial activity on the Sanborn Field and Tucker Prairie. The Sanborn Field has been under various cropping and management practices since 1888 and the Tucker Prairie is an uncultivated site. Seven different plots were chosen on the Sanborn Field and random samples were taken in the summit area on the Tucker Prairie, which represented a reference site. Soil microbial biomass C, phospholipids, and enzyme activity were reflective of the cropping and management histories observed on the Sanborn Field. Enzymatic activity was highly correlated to soil organic matter. The direct counts of fungal and bacterial biomass showed that fungal populations dominated these soils, which may be attributed to soil pH. Soil microbial biomass C and enzyme assays seemed to be better potential indicators of cropping histories than the other methods tested in the long-term plots.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 21 (1996), S. 271-276 
    ISSN: 1432-0789
    Schlagwort(e): 15N transformations ; Crop residues ; Soil texture ; Soil aggregation ; Microbial pool ; Microbial biomass
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In a greenhouse pot study, we examined the availability of N to grain sorghum from organic and inorganic N sources. The treatments were15N-labeled clover residues, wheat residues, and fertilizer placed on a sandy clay loam and loamy sand soil surface for an 8-week period. Soil aggregates formed under each soil texture were measured after 8 weeks for each treatment. Significantly greater 15N was taken up and recovered by grain sorghum in sandy clay loam pots compared with loamy sand pots. Greater 15N recovery was consistently observed with the inorganic source than the organic sources regardless of soil texture or time. Microbial biomass C and N were significantly greater for sandy clay loam soil compared with the loamy sand. Microbial biomass 15N was also significantly greater in the sandy clay loam treatment compared to the loamy sand. The fertilizer treatment initially had the greatest pool of microbial biomass 15N but decreased with time. The crop residue treatments generally had less microbial biomass 15N with time. The crop residues and soil texture had a significant effect on the water-stable aggregates formed after 8 weeks of treatments. Significantly greater water-stable aggregates were formed in the sandy clay loam than the loamy sand. Approximately 20% greater water-stable aggregates were formed under the crop residue treatments compared to the fertilizer only treatment. Soil texture seemed to be one of the most important factors affecting the availability of N from organic or inorganic N sources in these soils.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Biology and fertility of soils 21 (1996), S. 271-276 
    ISSN: 1432-0789
    Schlagwort(e): Key words15N transformations ; Crop residues ; Soil texture ; Soil aggregation ; Microbial pool ; Microbial biomass
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In a greenhouse pot study, we examined the availability of N to grain sorghum from organic and inorganic N sources. The treatments were 15N-labeled clover residues, wheat residues, and fertilizer placed on a sandy clay loam and loamy sand soil surface for an 8-week period. Soil aggregates formed under each soil texture were measured after 8 weeks for each treatment. Significantly greater 15N was taken up and recovered by grain sorghum in sandy clay loam pots compared with loamy sand pots. Greater 15N recovery was consistently observed with the inorganic source than the organic sources regardless of soil texture or time. Microbial biomass C and N were significantly greater for sandy clay loam soil compared with the loamy sand. Microbial biomass 15N was also significantly greater in the sandy clay loam treatment compared to the loamy sand. The fertilizer treatment initially had the greatest pool of microbial biomass 15N but decreased with time. The crop residue treatments generally had less microbial biomass 15N with time. The crop residues and soil texture had a significant effect on the water-stable aggregates formed after 8 weeks of treatments. Significantly greater water-stable aggregates were formed in the sandy clay loam than the loamy sand. Approximately 20% greater water-stable aggregates were formed under the crop residue treatments compared to the fertilizer only treatment. Soil texture seemed to be one of the most important factors affecting the availability of N from organic or inorganic N sources in these soils.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    ISSN: 1432-2013
    Schlagwort(e): Slowly adapting lung stretch receptor afferents ; Aortic baroreceptor afferents ; Presynaptic depolarization ; Neural control of respiration ; Neural control of circulation ; Nuclei of the solitary tract
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The presynaptic influences that act on terminals of slowly adapting lung stretch receptor afferents and aortic baroreceptor afferents within the nucleus of the solitary tract were assessed using intracellular recording and antidromic stimulation techniques. Central respiratory influences on the axcitability of lung stretch receptor terminals were observed in 29% (4 of 14) of measurements. These were confirmed in intracellular recordings where membrane depolarizations in synchrony with phrenic nerve discharge were seen in 17% (4 of 24) of fibres. In three cases membrane depolarization also occurred synchronously with artificial lung inflation. Neither tests of excitability nor intracellular recording revealed any evidence for equivalent presynaptic influences on 16 myelinated aortic baroreceptor terminals. Stimulation of the superior laryngeal nerve evoked depolarizations in 50% (7 of 14) of lung stretch receptor terminals. These took the form of complex waves of depolarization with both short (3–8 ms) and long latency (27–35 ms) components. The amplitude of the long latency response increased during the period of phrenic nerve discharge, i.e. during “central inspiration”. These effects are discussed in relation to the central respiratory influences on both respiratory and cardiovascular reflexes.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 1432-2013
    Schlagwort(e): Inspiratory neurones ; Slowly adapting pulmonary stretch receptors ; Spike triggered averaging ; Neural control of respiration ; Connectivity of respiratory neurones ; Nuclei of the tractus solitarius ; Hering-Breuer reflex
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The synaptic connection between slowly adapting pulmonary stretch receptor afferents and inspiratory neurones within a region ventral to the tractus solitarius was determined using intracellular recording and spike triggered averaging techniques. When the vagus nerve was stimulated at intensities eliciting a Hering-Breuer reflex, the difference in mean latency between centrally recorded action potentials of slowly adapting pulmonary stretch receptor afferents and e.p.s.p.s of inspiratory beta neurones was 0.2 ms. This difference is indicative of a monosynaptic connection. Extracellular single unit spikes of slowly adapting pulmonary stretch receptors recorded from the nodose ganglion were used to trigger the averaging of synaptic noise recorded from inspiratory neurones. A prominent wave of synaptic depolarization was observed in all inspiratory beta neurones even when a small number of sweeps were averaged. This depolarization was absent from inspiratory alpha neurones. The shape indices of these depolarizations are consistent with a monosynaptic connection between slowly adapting pulmonary stretch receptor afferents and inspiratory beta neurones. In addition, the data raise the possibility that this connection is multiple and distributed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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