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  • 1
    Publication Date: 2020-01-15
    Type: paper
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  • 2
    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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  • 3
    ISSN: 1432-0789
    Keywords: Key words Phospholipid fatty acids ; Substrate-induced respiration ; Fungi ; Bacteria ; Sheep-grazing ; Fertiliser ; Lime ; Microbial biomass ; Soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In this study we examined the effect on soil fungal:bacterial biomass ratios of withholding fertiliser, lime, and sheep-grazing from reseeded upland grassland. The cessation of fertiliser applications on limed and grazed grassland resulted in a reduction in soil pH from 5.4 to 5.1. The cessation of fertiliser applications and liming on grazed grassland resulted in a fall in pH from 5.4 to 4.7, whereas withholding fertiliser and lime and the removal of grazing resulted in a further reduction to pH 4.5. Substrate-induced respiration was reduced in the unfertilised grazed (21%; P〈0.01) and unfertilised ungrazed (36%; P〈0.001) treatments. Bacterial substrate-induced respiration and bacterial fatty acids were unaffected by the treatments. The relative abundance of the fungal fatty acid 18:2ω6 increased by 39 and 72% (P〈0.05) in the limed grazed and unfertilised grazed treatments, respectively. Fungal substrate-induced respiration increased in the limed grazed (18%) and unfertilised grazed (65%; P〈0.05) treatments. The ratio of 18:2ω6: bacterial fatty acids was correlated with the ratio of fungal:bacterial substrate-induced respiration (r=0.69; P〈0.001).
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  • 4
    ISSN: 1432-0789
    Keywords: Fungal biomass ; Respiration ; Nutrient cycling ; Microcosms ; Grass litter ; Onychiurus procampatus ; Phoma exigua ; Collembola
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory microcosms containing litter from three tussock grasslands were used to assess the impact of grazing by a collembolan, Onychiurus procampatus, on the abundance, nutrient release, and respiration of the saprotrophic fungus, Phoma exigua. The fungal biomass and respiration rate were significantly reduced only when Collembola were present in excess of mean field densities but perhaps more typical of spatial aggregations in the soil. A high efficiency of nutrient immobilization by P. exigua was demonstrated but nutrient release was not significantly affected by the fauna. Problems associated with the use of microcosms in the simulation of field conditions are discussed.
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  • 5
    ISSN: 1432-0789
    Keywords: Keywords Soil microbial biomass ; Soil enzymes ; Particle-size fractions ; Heavy metals ; Phospholipid fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Particle-size fractionation of a heavy metal polluted soil was performed to study the influence of environmental pollution on microbial community structure, microbial biomass, microbial residues and enzyme activities in microhabitats of a Calcaric Phaeocem. In 1987, the soil was experimentally contaminated with four heavy metal loads: (1) uncontaminated controls; (2) light (300 ppm Zn, 100 ppm Cu, 50 ppm Ni, 50 ppm V and 3 ppm Cd); (3) medium; and (4) heavy pollution (two- and threefold the light load, respectively). After 10 years of exposure, the highest concentrations of microbial ninhydrin-reactive nitrogen were found in the clay (2–0.1 μm) and silt fractions (63–2 μm), and the lowest were found in the coarse sand fraction (2,000–250 μm). The phospholipid fatty acid analyses (PLFA) and denaturing gradient gel electrophoresis (DGGE) separation of 16S rRNA gene fragments revealed that the microbial biomass within the clay fraction was predominantly due to soil bacteria. In contrast, a high percentage of fungal-derived PLFA 18 : 2ω6 was found in the coarse sand fraction. Bacterial residues such as muramic acid accumulated in the finer fractions in relation to fungal residues. The fractions also differed with respect to substrate utilization: Urease was located mainly in the 〈2 μm fraction, alkaline phosphatase and arylsulfatase in the 2–63 μm fraction, and xylanase activity was equally distributed in all fractions. Heavy metal pollution significantly decreased the concentration of ninhydrin-reactive nitrogen of soil microorganisms in the silt and clay fraction and thus in the bulk soil. Soil enzyme activity was reduced significantly in all fractions subjected to heavy metal pollution in the order arylsulfatase 〉phosphatase 〉urease 〉xylanase. Heavy metal pollution did not markedly change the similarity pattern of the DGGE profiles and amino sugar concentrations. Therefore, microbial biomass and enzyme activities seem to be more sensitive than 16S rRNA gene fragments and microbial amino-sugar-N to heavy metal treatment.
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  • 6
    ISSN: 1432-0789
    Keywords: Collembola ; Food preferences ; Grassland ; Fungi ; Gut contents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Specimens of Onychiurus procampatus (Collembola) observed grazing on fungal mycelia were collected from the surface soil of three differently manged upland grasslands. A general trend of an increasing proportion of Collembola with a full gut was found along a gradient of reduced sheep management intensity, which was correlated with increased fungal biomass. In the laboratory, this collembolan showed a consistent order of preference for the mycelium of seven common fungal species isolated from the field sites.
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  • 7
    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.
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  • 8
    ISSN: 1432-0789
    Keywords: Key words Defoliation ; Microbial biomass ; Microbial populations ; Dehydrogenase activity ; Respiration ; Bacteria ; Fungi ; Upland grassland ; Upland soil ; Pseudomonas spp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A microcosm study was conducted to investigate the effect of continuous plant defoliation on the composition and activity of microbial populations in the rhizosphere of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). Continuous defoliation of ryegrass and clover resulted in significant (P〈0.01) increases in soil microbial biomass, although whilst increases were measured from day 2 in soil sown with clover significant increases were only seen from day 21 in soil sown with ryegrass. These increases were paralleled, from day 10 onwards, by increases in the numbers of culturable bacteria. Numbers of Pseudomonas spp. also increased in the later stages of the study. No influence on culturable fungal populations was detected. Whilst shifts in the composition of the microbial populations were measured in response to defoliation there was little effect on microbial activity. No changes in either dehydrogenase activity or microbial respiration in the rhizosphere of ryegrass or clover were measured in response to defoliation, but both dehydrogenase activity and microbial respiration were greater in ryegrass than clover when values over the whole study were combined. Continuous defoliation resulted in significant (P〈0.001) reductions in the root dry weight of ryegrass and clover, of the order 19% and 16%, respectively.
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  • 9
    ISSN: 1432-0789
    Keywords: Defoliation ; Microbial biomass ; Microbial populations ; Dehydrogenase activity ; Respiration ; BacteriaFungi ; Upland grassland Upland soil ; Pseudomonas spp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A microcosm study was conducted to investigate the effect of continuons plant defoliation on the composition and activity of microbial populations in the rhizosphere of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). Continuons defoliation of ryegrass and clover resulted in sigmficant (P 〈0.01) increases in soil microbial biomass, although whilst increases were measured from day 2 in soil sown with clover significant increases were only seen from day 21 in soil sown with ryegrass. These increases were paralleled, from day 10 onwards, by increases in the numbers of culturable bacteria. Numbers ofPsendomonas spp. also increased in the later stages of the study. No influence on culturable fungal populations was detected. Whilst shifts in the composition of the microbial populations were measured in response to defoliation there was little effect on microbial activity. No changes in either dehydrogenase activity or microbial respiration in the rhizosphere of ryegrass or clover were measured in response to defoliation, but both dehydrogenase activity and microbial respiration were greater in ryegrass than clover when values over the whole study were combined. Continuous defoliation resulted in significant (P 〈0.001) reductions in the root dry weight of ryegrass and clover, of the order 19% and 16%, respectively.
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  • 10
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The use of manipulative experiments to study directly the effects of climate change on natural and managed systems is expensive if performed on a large scale: it also relies upon accurate predictions of future climatic conditions. Predictive modelling is less expensive and permits a range of scenarios to be considered but this is only as reliable as the underpinning model.Predicting the suitability of England and Wales for the cultivation of forage maize under climate change was attempted using an established crop growth model by Muchow et al. (1990) integrated with climate data. The biological and climatic inputs to the model were the thermal requirements for the stages of crop growth, leaf number, leaf area, harvest index, the daily maximum and minimum air temperature, precipitation and solar radiation. These values were obtained from a daily meteorological database for ninety-three sites in England and Wales for the period 1951–80. Model outputs as point values of potential crop yield predicting current production -‘baseline’- were statistically validated using actual crop yield data collated from bibliographic analysis. The baseline results indicated that pans of the south-east appeared to be too dry and the north too cold. The model was run again using an artificial sensitivity test (temperature +2°C. precipitation ±10%). Increased precipitation led to a predicted increase in geographical suitability of the UK for forage maize production to the north and west. Under reduced precipitation there was a decrease in suitability in the south-east, possibly owing to moisture stress.
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