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  • Articles  (162)
  • Microbial biomass  (162)
  • Geosciences  (162)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 18 (1994), S. 137-142 
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Bamboo savanna ; N mineralization ; Nutrient pools ; Temporal variations ; Nitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of harvesting bamboo savanna on the dynamics of soil nutrient pools, N mineralization, and microbial biomass was examined. In the unharvested bamboo site NO inf3 sup- -N in soil ranged from 0.37 to 3.11 mg kg-1 soil and in the harvested site from 0.43 to 3.67 mg kg-1. NaHCO3-extractable inorganic P ranged from 0.55 to 3.58 mg kg-1 in the unharvested site and from 1.01 to 4.22 mg kg-1 in the harvested site. Over two annual cycles, the N mineralization range in the unharvested and harvested sites was 0–19.28 and 0–24.0 mg kg-1 soil month-1, respectively. The microbial C, N, and P ranges were 278–587, 28–64, and 12–26 mg kg-1 soil, respectively, with the harvested site exhibiting higher values. Bamboo harvesting depleted soil organic C by 13% and total N by 20%. Harvesting increased N mineralization, resulting in 10 kg ha-1 additional mineral N in the first 1st year and 5 kg ha-1 in the 2nd year following the harvest. Microbial biomass C, N and P increased respectively by 10, 18, and 5% as a result of bamboo harvesting.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 18 (1994), S. 155-162 
    ISSN: 1432-0789
    Keywords: Grazing ; Semiarid soils ; Shrubland ; Grassland ; Microbial biomass ; Microbial respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The major objectives of this study were to determine the influence of grazing on the soil microbial biomass and activity in semiarid grassland and shrubland areas and to quantify the canopy effect (the differences in soil microbial biomass and activities between soils under plant canopies and soils in the open between plants). We also quantified changes in microbial biomass and activity during seasonal transition from dry to moist conditions. Chronosequences of sites withdrawn from grazing for 0, 11, and 16 years were sampled in a grassland (Bouteloua spp.) area and a shrubland (Atriplex canescens) area on and near the Sevilleta National Wildlife Reguge in central New Mexico, USA. Samples were obtained from beneath the canopies of plants (Yucca glauca in the grassland and A. canescens in the shrubland) and from open soils; they were collected three times during the spring and summer of a single growing season. Organic C, soil microbial biomass C, and basal respiration rates (collectively called the “soil C triangle”) were measured. We also calculated the microbial: organic C ratio and the metabolic quotient (ratio of respiration to microbial C) as measures of soil organic C stability and turnover. Although we had hypothesized that individual values of the soil C triangle would increase and that the ratios would decrease with time since grazing, differences in microbial parameters between sites located along the chronosequences were generally not significant. Grazing did not have a consistion effect on organic C, microbial C, and basal respiration in our chronosequences. The microbial: organic C ratio and the metabolic quotient generally increased with time since grazing on the shrubland chronosequence. The microbial: organic C ratio decreased with time since grazing and the metabolic quotient increased with time since grazing on the grassland chronosequence. The canopy effect was observed at all sites in nearly all parameters including organic C, microbial C, basal respiration, the microbial: organic C ratio, and the metabolic quotient which were predominantly higher in soils under the canopies of plants than in the open at all sites. Microbial biomass and activity did not increase during the experiment, even though the availability of moisture increased dramatically. The canopy effects were approximately equal on the shrubland and grassland sites. The microbial: organic C ratios and the metabolic quotients were generally higher in the shrubland soils than in the grassland soils.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 19 (1995), S. 1-9 
    ISSN: 1432-0789
    Keywords: Mineralization ; Soil organic matter ; Aerobic incubation ; CaCl2 extraction ; Soluble organic nitrogen ; Microbial biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Indices of N mineralization in soils of contrasting texture, pH, and organic matter contents were compared at different dates during the growing season. The indices were derived from a 12-week aerobic incubation, determination of the amount of microbial biomass at the start of the incubation, determination of the increase in NH 4 + after boiling with 2 M KCl for 2h, and extraction of total soluble N with 0.01 M CaCl2. Cumulative mineral N increased linearly with time in the course of the incubations. Rates of mineralization in soil samples taken in March 1989 and 1990 were significantly correlated with soluble organic N, while correlations between the mineralization rate and the increase in NH 4 + after boiling with 2 M KCl for 2 h were poor for sandy soils and absent for loamy soils. Correlations between NH 4 + after boiling with 2 M KCl for 2h and the soil N concentration were highly significant, but no general relationship was found between the mineralization rate and the soil N concentration. Neither biomass N nor biomass C was significantly correlated with the mineralization rate or with one of the chemical indices. Among the methods tested, soluble organic N extracted with 0.01 M CaCl2 was the only method with any promise for routine measurement of the mineralization capacity of the individual sites.
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  • 4
    ISSN: 1432-0789
    Keywords: Fatty acids ; Phospholipids ; Lipopolysaccharides ; Microbial biomass ; Gram-positive bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Several soils subject to different cultivation and management practices were examined by analysis of fatty acid profiles derived from phospholipids and lipopolysaccharides, using an improved sequential method which is capable of measuring ester-linked and non-ester-linked phospholipid fatty acids (EL-PLFA, NEL-PLFA, respectively) and the hydroxy fatty acids in lipopolysaccharides. A good correlation was obtained (r〉0.90) between the soil biomass and total EL-PLFA in the soils investigated, which ranged from forest soils to a variety of agricultural soils. Elucidation of the composition of the community structure was an additional task. Eukaryotes can be differentiated from bacteria by the presence of polyunsaturated and ω-hydroxy fatty acids, both of which were much more abundant in the OF layer of the forest soil than in the remaining samples. A relatively low proportion of monomethyl branched-chain saturated fatty acids was obtained in the forest OF horizon, these being indicators for Gram-positive bacteria and actinomycetes. Various subclasses of proteobacteria produce β and mid-chain hydroxy fatty acids, which occur primarily in agricultural soils. The ratios between monounsaturated fatty acids and saturated fatty acids seem to be very useful parameters of soil environmental conditions. In addition, on the basis of the differences in composition of the NEL-PLFA and hydroxy fatty acids of lipopolysaccharides, clear indications for the community structure of various soils were obtained. In the forest soils much more abundant anaerobic micro-organisms and relatively less abundant proteobacteria were present than in the other soils. In the cultivated soils, however, the proportion of Gram-negative bacteria was considerably higher. Furthermore, eukaryotes appeared to be pre-dominant in the soils once used for a manure deposit site.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 19 (1995), S. 141-147 
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Biomass C:N ratio Acidification ; Beech forest ; Soil organic C ; Total N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soils from 38 German forest sites, dominated by beech trees (Fagus sylvatica L.) were sampled to a depth of about 10 cm after careful removal of overlying organic layers. Microbial biomass N and C were measured by fumigation-extraction. The pH of the soils varied between 3.5 and 8.3, covering a wide range of cation exchange capacity, organic C, total N, and soil C:N values. Maximum biomass C and biomass N contents were 2116 μg C m-2 and 347 μg N m-2, while minimum contents were 317 and 30 μg m-2, respectively. Microbial biomass N and C were closely correlated. Large variations in microbial biomass C:N ratios were observed (between 5.4 and 17.3, mean 7.7), indicating that no simple relationship exists between these two parameters. The frequency distribution of the parameters for C and N availability to the microflora divided the soils into two subgroups (with the exception of one soil): (1) microbial: organic C〉12 mg g-1, microbial:total N〉28 mg g-1 (n=23), a group with high C and N availability, and (2) microbial:organic C≤12 mg g-1, microbial:total N≦28 mg g-1 (n=14), a group with low C and N availability. With the exception of a periodically waterlogged soil, the pH of all soils belonging to subgroup 2 was below 5.0 and the soil C:N ratios were comparatively high. Within these two subgroups no significant correlation between the microbial C:N ratio and soil pH or any other parameter measured was found. The data suggest that above a certain threshold (pH 5.0) microbial C:N values vary within a very small range over a wide range of pH values. Below this threshold, in contrast, the range of microbial C:N values becomes very large.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 19 (1995), S. 159-165 
    ISSN: 1432-0789
    Keywords: Collembola ; Microbial biomass ; Soil compaction ; Crop rotation ; Arable soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Collembola and microbial biomass C were investigated in a field experiment with controlled agricultural traffic and crop rotation over a period of 27 months. The wheel-induced compactive efforts were applied according to management practices within the crop rotation of sugar beet, winter wheat, and winter barley. Increasing wheel traffic produced increasing soil compaction, mainly due to a reduction in surface soil porosity. Increasing soil compaction was accompanied by a decrease in microbial biomass C and the density of collembola. The influence of soil compaction on microbial biomass C was smaller than that of the standing crop. However, for collembola, especially euedaphic species, a reduction in pore space appeared to be of more importance than the effects of a standing crop. Within the crop rotation, microbial biomass C and the density of collembola increased in the order sugar beet, winter wheat, and winter barley.
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  • 7
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Dehydrogenase activity Urease ; Phosphatase ; Respiration ; ATP ; Grazing Fertiliser ; Lime
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field study was conducted to determine the influence of a short-term (2 year) cessation of fertiliser applications, liming, and sheep-grazing on microbial biomass and activity in a reseeded upland grassland soil. The cessation of fertiliser applications (N and NPK) on a limed and grazed grassland had no effect on microbial biomass measurements, enzyme activities, or respiration. Withholding fertiliser and lime from a grazed grassland resulted in significant reductions in both microbial biomass C (P〈0.05) and dehydrogenase activity (P〈0.05) by approximately 18 and 21%, respectively. The removal of fertiliser applications, liming, and grazing resulted in even greater reductions in microbial biomass C (44%, P〈0.001) and dehydrogenase activity (31%, P〈0.001), and significant reductions in microbial biomass N (P〈0.005), urease activity (P〈0.05), phosphatase activity (P〈0.001), and basal respiration (P〈0.05). The abundance of culturable bacteria and fungi and the soil ATP content were unaffected by changes in grassland managements. With the cessation of liming soil pH fell from 5.4 to 4.7, and the removal of grazing resulted in a further reduction to pH 4.5. A significant negative linear relationship (r 2=0.97; P〈0.01) was found between increasing soil acidity and dehydrogenase activity. Possible mechanisms influencing these changes are discussed.
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  • 8
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Substrate-induced respiration ; Beech litter ; Fragmentation ; Nutrient limitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In February 1993 samples of litter from three different litter layers (upper, intermediate, and lower) were taken from a beechwood growing on basalt soil. Using the substrate-induced respiration method, we investigated the influence of fragmentation and glucose concentration on the maximum initial respiratory response. Glucose concentrations ranged between 0 and 160000 μg g-1 dry weight. The initial respiratory response reached a maximum at 80000 μg glucose g-1 dry weight. The addition of higher concentrations of glucose resulted in negligible changes in respiration. Litter materials of four different size classes (intact leaves, fragmented 〈100 mm2, 〈25 mm2, and 〈5 mm2) were amended with 80000 μg glucose g-1 dry weight. Substrate-induced respiration was at a maximum in the size class 〈25 mm2. The addition of glucose to intact litter did not result in microbial growth. It is concluded that C is not the primary limiting element for the microflora in litter layers of the study site. Fragmentation of beech litter enabled the microorganisms to grow. Presumably, nutrients that limited microbial growth in intact litter were mobilized by the fragmentation procedure and enabled microorganisms to grow in fragmented litter materials.
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  • 9
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Substrate-induced respiration ; Selective inhibition ; Prokaryote: eukaryote ratio Woodland soils ; Streptomycin ; Cycloheximide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Bacterial and fungal contributions to microbial respiration in three beechwood soils rich in C (two basalt soils and one limestone soil) were investigated by using streptomycin and cycloheximide to inhibit substrate-induced respiration after glucose (8000 μg g-1), N, and P addition to soil samples. The inhibitors were added as solutions (2000, 8000, and 16000 μg g-1) and the reduction in substrate-induced respiration after separate and combined inhibitor addition was measured in an automated electrolytic microrespirometer. Bacterial and fungal contributions to microbial respiration were calculated using the interval 6–10 h after inhibitor application. The microbial biomas was smaller in the two basalt soils (Oberhang and Mittelhang) than in the limestone soil (Unterhang). In the presence of both inhibitors, microbial respiration was inhibited by a maximum of 45, 45, and 25% in the two basalt soils and the limestone soil, respectively. Inhibition of microbial respiration was at a maximum at streptomycin and cycloheximide concentrations of 16000 μg g-1. The inhibitor additivity ratio approached 1.0 even at high inhibitor concentrations, indicating high inhibitor selectivity. Calculated prokaryote: eukaryote ratios indicated lower bacterial contributions to the microbial biomass in the Mettelhang (0.74) and Unterhang (0.73) than in the Oberhang (0.88) soil.
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  • 10
    ISSN: 1432-0789
    Keywords: Excreta ; Fertiliser ; Microbial biomass ; Nitrogen ; Silvopastoral
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper describes a field study to assess the effect of increasing the frequency of split applications of N fertiliser on the pattern of plant uptake, soil N availability, and microbial biomass C and N. Measurements were taken during the growing season in different positions relative to young trees (Prunus avium L.) in an upland silvopastoral system in its first year after establishment. At fertiliser rates of 72 and 144 kg ha-1 N applied as NH4NO3, increasing the number of split applications increased N uptake by the pasture. Mineral forms of soil N measured 2 weeks after application indicated that residual NH inf4 sup+ -N and total mineral N were also greater in this treatment on certain dates. Soil NO inf3 sup- -N was positively correlated with the soil moisture content, and nitrification reached a maximum in early May and declined rapidly thereafter except within the herbicide-treated areas around the trees where soil moisture had been conserved. Results of the study suggest that high NO inf3 sup- -N in herbicide-treated areas was probably caused by mineralisation of grass residues and low uptake by the tree rather than by preferential urine excretion by sheep sheltering beside the trees. Mean microbial biomass C and N values of 894 and 213 kg ha-1, respectively, were obtained. Microbial C was slightly increased by the higher frequency of split applications at 144 kg ha-1 N and was probably related to the greater herbage production with this treatment. Microbial N was not significantly affected by the N treatments. Both microbial biomass C and N increased during the growing season, resulting in the net immobilisation of at least 45 kg ha-1 N which was later released during the autumn.
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