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  • Microbial biomass  (4)
  • Springer  (4)
  • Wiley
  • 1990-1994  (4)
  • 1945-1949
  • 1935-1939
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Keywords
Publisher
  • Springer  (4)
  • Wiley
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    The dual importance of competition and predation as regulatory forces in terrestrial ecosystems: evidence from decomposer food-webs (1993)
    Springer
    Oecologia 93 (1993), S. 303-306 
    Details
    ISSN: 1432-1939
    Keywords: Competition ; Detritus food web ; Microbial biomass ; Nematode ; Predation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relative importance of predation and competition (resource limitation) in influencing the components of a below-ground food-web consisting of three trophic levels (bacteria and fungi; bacterial-feeding and fungal-feeding nematodes; and top predatory nematodes) was estimated using microbial biomass and nematode frequency data collected throughout a 1-year period in two agro-ecosystems. The study suggested that bacterial and fungal biomass were likely to be regulated by grazing and competition respectively, and that these differences were likely to be attributed to the biological (probably morphological) differences between bacteria and fungi, in contrast to the predictions of the hypothesis of Hairston et al. (1960). Top predatory nematodes were sometimes strongly related to the microbial but not microbial-feeding trophic levels, indicating that microbial biomass may directly influence top predator numbers, and that the intermediate level may simply serve as a conduit by which resources pass from the bottom to top trophic levels. This study also suggests that the detritus food-web acts as two distinct (bacterial-and fungal-based) compartments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317685
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  • 2
    Electronic Resource
    Electronic Resource
    Recolonization of methyl bromide sterilized soils under four different field conditions (1991)
    Springer
    Biology and fertility of soils 11 (1991), S. 181-189 
    Details
    ISSN: 1432-0789
    Keywords: Invasion ; Soil ; Recolonization ; Protozoa ; Rotifers ; Nematodes ; Microbial biomass ; Dehydrogenase activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The course of recovery in biological activity was assessed in the top 5 cm of undisturbed soil cores (29.7 cm diameter, 30 cm deep) that had been fumigated in the laboratory with methyl bromide. The cores were returned to their original pasture and forest sites, two with a moderate and two with a high rainfall, and untreated soils at all sites served as baselines. Sampling took place over 166 days (midsummer to midwinter). Microbial biomass (as measured by fumigation-extraction and substrate-induced respiration procedures) and dehydrogenase activity both recovered rapidly, but remained consistently lower in the fumigated than in untreated samples at both forest sites and at the moister of the two pasture sites. Bacterial numbers also recovered rapidly. Fungal hyphal lengths were, on average over 166 days, 25% lower in the fumigated soils. Levels of mineral N were initially highest in the fumigated soils, but declined with time. Fumigation generally had no detectable effects on the subsequent rates of net N mineralization and little effect on nitrification rates. Fumigation almost totally eliminated protozoa, with one to three species being recovered on day 0; the numbers recovered most rapidly in the moist forest soil and slowly in the dry pasture soil. The recoionization rate of protozoan species was similar in all soils, with species numbers on day 110 being 33 and 34 in the fumigated and untreated soils, respectively. Nematodes were eliminated by fumigation; recolonization was first detected on day 26 but by day 166, nematode numbers were still lower in fumigated than in untreated soils, the abundance being 10 and 62 g-1 soil and diversity 10 and 31 species, respectively. Overall, the results suggest that protozoan and nematode populations and diversities could provide a useful medium-term ecological index of the recovery in comprehensive soil biological activity following major soil pollution or disturbance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00335765
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of freeze-thaw events on mineralization of soil nitrogen (1992)
    Springer
    Biology and fertility of soils 14 (1992), S. 116-120 
    Details
    ISSN: 1432-0789
    Keywords: Freezing and thawing of soils ; Nitrogen mineralization ; Microbial biomass ; Ninhydrin-reactive N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In humid regions of the United States there is considerable interest in the use of late spring (April–June) soil NO 3 − concentrations to estimate fertilizer N requirements. However, little information is available on the environmental factors that influence soil NO 3 − concentrations in late winter/early spring. The influence of freeze-thaw treatments on N mineralization was studied on several central Iowa soils. The soils were subjected to temperatures of-20°C or 5°C for 1 week followed by 0–20 days of incubation at various temperatures. The release of soluble ninhydrin-reactive N, the N mineralization rate, and net N mineralization (mineral N flush) were observed. The freeze-thaw treatment resulted in a significant increase in the N mineralization rate and mineral N flush. The N mineralization rate in the freeze-thaw treated soils remained higher than in non-frozen soils for 3–6 days when thawed soils were incubated at 25°C and for up to 20 days in thawed soils incubated at 5°C. The freeze-thaw treatments resulted in a significant release of ninhydrin-reactive N. These values were closely correlated with the mineral N flush (r 2=0.84). The release of ninhydrin-reactive N was more closely correlated with biomass N (r 2=0.80) than total N (r 2=0.65). Our results suggest that freeze-thaw events in soil disrupt microbial tissues in a similar way to drying and re-wetting or chloroform fumigation. Thus the level of mineral N released was directly related to the soil microbial biomass. We conclude that net N mineralization following a spring thaw may provide a significant portion of the total NO 3 − present in the soil profile.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336260
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  • 4
    Electronic Resource
    Electronic Resource
    Impact of pasture contamination by copper, chromium, and arsenic timber preservative on soil microbial properties and nematodes (1994)
    Springer
    Biology and fertility of soils 18 (1994), S. 71-79 
    Details
    ISSN: 1432-0789
    Keywords: Heavy metals ; Microbial biomass ; Respiration ; Enzymes ; Denitrification ; Dimethyl sulphoxide reduction ; Nematodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Microbial properties and nematode abundance were measured along a gradient of increasing Cu, Cr, and As concentrations (50–1300 mg Cr kg-1) in the top 5 cm of a pasture soil contaminated by runoff of preserving liquor from an adjacent timber-treatment plant. Microbial biomass C and N were significantly (P〈0.05) lower in contaminated than uncontaminated soils. The amount of microbial biomass C as a percentage of total organic C declined significantly (r 2 value with Cr 0.726*) with increasing contamination, and the ratio of respired C to biomass C was significantly (P〈0.05) higher with contamination. Substrate-induced respiration, microbial biomass P, and denitrification declined (r2 value with Cr 0.601, 0.833*, and 0.709*, respectively) with increasing contamination. Increasing contamination had no effect on prokaryote substrate-induced respiration but eukaryote: eukaryote substrate-induced respiration declined significantly (r 2 value with Cr 0.722*). Accordingly, the ratio of prokaryote substrate-induced respiration increased significantly (r 2 value with Cr 0.799*) with contamination. There was a significant (r 2 value with Cr 0.872*) hyperbolic relationship between sulphatase activity and contamination, with activity declining by approximately 80% at 〉1000 mg Cr kg-1. Increasing contamination had no effect on basal respiration, dimethyl sulphoxide reduction, and phosphatase, urease, and invertase activities. Numbers of plant-associated nematodes declined significantly (r 2 value with Cr 0.780*) with contamination. On a percentage basis, plant-feeding nematodes predominated in less contaminated soils, whereas bacterial-feeding and predatory nematodes predominated in heavily contaminated soils. The use of the fumigation—incubation procedure for measurement of microbial biomass C in heavy-metal contaminated soils is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336448
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