Search results for "unge"
showing 10 items of 1645 documents
Effect of cropping cycles and repeated herbicide applications on the degradation of diclofop-methyl, bentazone, diuron, isoproturon and pendimethalin…
2002
A greenhouse study was conducted to investigate the ability of four crops (wheat, corn, oilseed rape and soybean) to influence the degradation of bentazone, diclofop-methyl, diuron, isoproturon and pendimethalin in soil. The present study showed that microbial biomass-carbon was significantly higher in planted soils than in bulk soil, especially with wheat and corn, after several cropping cycles. The biomass in corn and soybean planted soils was adversely affected by bentazone but recovered after three cropping cycles. In wheat-planted soils, diclofop-methyl application resulted in persistent increase of the amount of microbial biomass. Bentazone did not show accelerated degradation even af…
Degradation of 2,4‐D, 2,4‐Dichlorophenol, and 4‐Chlorophenol in Soil after Sorption on Humified and Nonhumified Organic Matter
1999
Soil organic matter (SOM) primarily governs sorption processes and therefore affects the availability of organic chemicals to degrading microorganisms. Transformations of 14 C-ring-labeled 2,4-dichlorophenoxyacetic acid (2,4-D); 2,4-dichlorophenol (2,4-DCP); and 4-chlorophenol (4-CP) sorbed on organic materials with increasing degrees of humification (wood, fresh straw, composted straw, ligain, and humic acid) and on a reference mineral sorbent (Al-oxide) were studied during soil incubation experiments. Chemicals previously sorbed on the different sorbents were applied to the soil. Mineralization kinetics, analysis of water and methanol extracts and measurements of the nonextractable radioa…
Leaching of glyphosate and AMPA under two soil management practices in Burgundy vineyards (Vosne-Romanée, 21-France)
2005
Some drinking water reservoirs under the vineyards of Burgundy are contaminated with herbicides. Thus the effectiveness of alternative soil management practices, such as grass cover, for reducing the leaching of glyphosate and its metabolite, AMPA, through soils was studied. The leaching of both molecules was studied in structured soil columns under outdoor conditions for 1 year. The soil was managed under two vineyard soil practices: a chemically treated bare calcosol, and a vegetated calcosol. After 680 mm of rainfall, the vegetated calcosol leachates contained lower amounts of glyphosate and AMPA (0.02% and 0.03%, respectively) than the bare calcosol leachates (0.06% and 0.15%, respectiv…
Seasonal dynamics of the bacterial community in forest soils under different quantities of leaf litter
2010
International audience; Soil microbial communities play an important role in soil carbon functioning, particularly in forest ecosystems. Their variation in response to climate change may affect soil carbon processes, highlighting the importance of understanding how environmental factors affect microbial communities. This study aimed to determine to what extent an increase in the quantity of fresh litter may affect heterotrophic mineralization of organic carbon and bacterial community structure in soil and litter. A litter manipulation experiment was performed in situ in a temperate deciduous forest. Three treatments of fresh litter inputs were considered: litter exclusion, natural condition…
Effect of onion consumption by rats on hepatic drug-metabolizing enzymes
2001
Fruits and vegetables or their natural constituents which increase detoxication enzymes and/or reduce activating enzymes are considered as good candidates to prevent chemically-induced carcinogenesis. In this study, rats were fed a diet supplemented with 20% onion powder for 9 days. Several cytochrome P450 (CYP)s enzymes (CYP 1A, 2B, 2E1, 3A), which are involved in carcinogen activation, were determined by measuring their enzyme activities using specific substrates. In addition, phase II enzymes activities such as UDP-glucuronosyltransferase (UGT) and glutathione S-transferase (GST), involved in detoxication of carcinogens, were measured. Protein levels of CYPs and GST A1/A2, A3/A5, Ml, M2 …
Neolithic Human Societies and Woodlands in the North-Western Mediterranean Region: Wood and Charcoal Analysis
2017
An overview of woodland history in the north-western Mediterranean region, based on charcoal analysis (Anthracology) from Mesolithic and Neolithic sites, is proposed for the Mediterranean areas of France, Spain and Portugal. The taxonomic identification of charcoal fragments and the diachronic variations of taxa frequencies provide, for each settlement, an accurate image of the local vegetal cover. During the end of the last glaciation, beginning of the Holocene, vegetation dynamics reflects the evolution of climatic and geographic conditions. Any potential ecological impact by hunter-fisher-gatherer communities (Mesolithic) remains invisible; the same comment applies to the farming-herding…
Differential Responses of Nitrate Reducer Community Size, Structure, and Activity to Tillage Systems
2009
ABSTRACT The main objective of this study was to determine how the size, structure, and activity of the nitrate reducer community were affected by adoption of a conservative tillage system as an alternative to conventional tillage. The experimental field, established in Madagascar in 1991, consists of plots subjected to conventional tillage or direct-seeding mulch-based cropping systems (DM), both amended with three different fertilization regimes. Comparisons of size, structure, and activity of the nitrate reducer community in samples collected from the top layer in 2005 and 2006 revealed that all characteristics of this functional community were affected by the tillage system, with increa…
Copper Dynamics and Impact on Microbial Communities in Soils of Variable Organic Status
2008
International audience; The effect of soil organic status on copper impact was investigated by means of a microcosm study carried out on a vineyard soil that had been amended with varying types of organic matter during a previous long-term field experiment. Soil microcosms were contaminated at 250 mg Cu kg−1 and incubated for 35 days. Copper distribution and dynamics were assessed in the solid matrix by a sequential extraction procedure and in the soil solution by measuring total and free exchangeable copper concentrations. Copper bioavailability was also measured with a whole-cell biosensor. Modifications of microbial communities were assessed by means of biomass-C measurements and charact…
Cadmium availability at different soil pH to transgenic tobacco overexpressing ferritin
2003
International audience; Knowledge on physiological mechanisms and plant metabolism can be used to enhance metal uptake. The capacity to uptake metals of transgenic tobaccos overexpressing ferritin in plastids (P6) or in cytoplasm (C5) and a control tobacco (A) is assessed in three polluted soils from the same soil series, with a similar Cd content, but displaying pH from 5.8 to 7 (8b2, 8b3, S11). Differences in dry leave weight were not significant between the three tobaccos growing on each soil. Iron concentration in ferritin overexpression either in P6 or in C5 tobaccos increased only on the S11 soil, which had a soil pH 7, in comparison to A tobacco. In both 8b2 and 8b3 soils at pH lower…
Loss in microbial diversity affects nitrogen cycling in soil
2013
International audience; Microbial communities have a central role in ecosystem processes by driving the Earth's biogeochemical cycles. However, the importance of microbial diversity for ecosystem functioning is still debated. Here, we experimentally manipulated the soil microbial community using a dilution approach to analyze the functional consequences of diversity loss. A trait-centered approach was embraced using the denitrifiers as model guild due to their role in nitrogen cycling, a major ecosystem service. How various diversity metrics related to richness, eveness and phylogenetic diversity of the soil denitrifier community were affected by the removal experiment was assessed by 454 s…