Search results for "Community structure"
showing 10 items of 163 documents
Temporal variability of airborne bacterial community structure in an urban area
2006
International audience; Temporal airborne bacterial genetic community structure and meteorological factors were analysed above an urban area in the northwest of France from December 2003 to April 2004 with a sampling strategy considering different time intervals (from an hour to a month). Principal component analysis (PCA) of B-ARISA (Bacterial-Automated Ribosomal Intergenic Spacer Analysis) profiles revealed a hierarchy in the temporal variability of bacterial community: daily<weekly<seasonal. Co-inertia analysis between B-ARISA data and meteorological factors demonstrated the correlation between the seasonal variability in the bacterial community and climatic conditions such as temperatur…
Assessing genetic structure and diversity of airborne bacterial communities by DNA fingerprinting and 16S rDNA clone library
2005
Abstract The density, genetic structure and diversity of airborne bacterial communities were assessed in the outdoor atmosphere. Two air samples were collected on the same location (north of France) at two dates (March 2003 (sample1) and May 2003 (sample 2)). Molecular culture-independent methods were used to characterise airborne bacterial communities regardless of the cell culturability. The automated-ribosomal intergenic spacer analysis (A-RISA) was performed to characterise the community structure in each sample. For both sampling dates, complex A-RISA patterns were observed suggesting a highly diverse community structure, comparable to those found in soil, water or sediment environment…
Disentangling the rhizosphere effect on nitrate reducers and denitrifiers: insight into the role of root exudates.
2008
International audience; To determine to which extent root-derived carbon contributes to the effects of plants on nitrate reducers and denitrifiers, four solutions containing different proportions of sugar, organic acids and amino acids mimicking maize root exudates were added daily to soil microcosms at a concentration of 150 μg C g−1 of soil. Water-amended soils were used as controls. After 1 month, the size and structure of the nitrate reducer and denitrifier communities were analysed using the narG and napA, and the nirK, nirS and nosZ genes as molecular markers respectively. Addition of artificial root exudates (ARE) did not strongly affect the structure or the density of nitrate reduce…
Predation on two vole species by a shared predator: antipredatory response and prey preference
2008
In prey communities with shared predators, variation in prey vulnerability is a key factor in shaping community dynamics. Conversely, the hunting efficiency of a predator depends on the prey community structure, preferences of the predator and antipredatory behavioural traits of the prey. We studied experimentally, under seminatural field conditions, the preferences of a predator and the antipredatory responses of prey in a system consisting of two Myodes species of voles, the grey-sided vole (M. rufocanus Sund.) and the bank vole (M. glareolus Schreb.), and their specialist predator, the least weasel (Mustela nivalis nivalis L.). To quantify the preference of the weasels, we developed a ne…
Benthic Invertebrates in Relation to Acidity in Finnish Forest Lakes
1990
In order to examine the effects of acidity on abundance and community structure of the benthic invertebrates in forest lakes and to evaluate the applicability of certain benthic animals as early warning indicators of lake acidification, 140 lakes, situated mainly in southern Finland, were studied by quantitative and qualitative sampling methods.
Collembolan communities in deciduous forests of different origin in Finland
2006
The aim of the study was to compare the collembolan communities in anthropogenous birch stands of different origin with each other and with natural forests at the same latitude. Nine sites were investigated: three birch stands (Betula pendula) planted ca. 30 years prior to the study after clear-cutting of spruce stands, three birch stands planted ca. 30 years earlier on arable soil that had been under cultivation until reforestation, and three natural deciduous forests. These were sampled in August and October 1998, and microarthropods were extracted, counted and identified. Thirty years after reforestation, the collembolan communities of “Birch after Spruce” and “Birch after Field” differe…
Relationship between soil microarthropod species diversity and plant growth does not change when the system is disturbed
2002
Soil microarthropods influence vital ecosystem processes, such as decomposition and nutrient mineralisation. There is evidence, however, that proper functioning of ecosystems does not require the presence of all its constituent species, and therefore some species can be regarded as functionally redundant. It has been proposed that species redundancy can act as an insurance against unfavourable conditions, and that functionally redundant species may become important when a system has faced a disturbance (the “insurance hypothesis”). We conducted a laboratory microcosm experiment with coniferous forest soil and a seedling of silver birch (Betula pendula). A gradient of microarthropod diversit…
Evidence for shifts in the structure and abundance of the microbial community in a long-term PCB-contaminated soil under bioremediation.
2011
International audience; Although the impact of bioremediation of PCB-contaminated sites on the indigenous microbial community is a key question for soil restoration, it remains poorly understood. Therefore, a small-scale bioremediation assay made of (a) a biostimulation treatment with carvone, soya lecithin and xylose and (b) two bioaugmentation treatments, one with a TSZ7 mixed culture and another with a Rhodococcus sp. Z6 pure strain was set up. Changes in the structure of the global soil microbial community and in the abundances of different taxonomic phyla were monitored using ribosomal intergenic spacer analysis (RISA) and real-time PCR. After an 18-month treatment, the structure of th…
Relationships between soil water repellency and microbial community composition under different plant species in a Mediterranean semiarid forest
2014
Abstract Soil water repellency (SWR) can influence many hydrological soil properties, including water infiltration, uneven moisture distribution or water retention. In the current study we investigated how variable SWR persistence in the field is related to the soil microbial community under different plant species (P. halepensis, Q. rotundifolia, C. albidus and R. officinalis) in a Mediterranean forest. The soil microbial community was determined through phospholipid fatty acids (PLFA). The relationships between microbiological community structure and the soil properties pH, Glomalin Related Soil Protein (GRSP) and soil organic matter (SOM) content were also studied. Different statistical …
Plant effects on the soil community: A microcosm experiment
1999
Abstract An experiment was carried out in microcosms for testing the hypothesis that a higher level of primary production should maintain a decomposer community with higher biomass and activity. Microcosms with coniferous forest humus and a diverse microbial and faunal community were divided into three sets: (1) control without plants, (2) with birch seedlings in full illumination, and (3) with birch seedlings, shaded to reduce the net primary production. During 16 weeks of incubation at +16 °C, no treatment effects were found in numbers or biomass of taxonomic or functional groups of soil organisms, nor in the system respiration in darkness. The community structure of the shaded systems di…