Search results for "Systematic"

La lutte biologique contre l'ambroisie à feuille d'armoise illustrée par l'exemple d'Ophraella communa : quels intérêts et quelles limites

2016

Common ragweed (Ambrosia artemisiifolia) was introduced in France over 150 years ago and its spreading across France now seems inexorable. The specific biology of this summer annual creates new problems for the managers of the various habitats where the plant can be found. The reduced possibility, or even the impossibility, to use traditional control means in certain environment conditions brings managers to consider biological control as one of the few possible means for slowing down the spread, or even pushing back the distribution area, of this invasive and allergenic plant. With Ophraella communa as an example, a reflection is presented on the benefit-risk balance of the introduction of…

Biodiversity and taxonomy in primates: between extinction and inflation.

2020

Growth response of the saltbush Atriplex nummularia L. to inoculation with the arbuscular mycorrhizal fungus Glomus intraradices

2005

Abstract Plantlets of Atriplex nummularia were inoculated with the arbuscular mycorrhizal fungi Glomus intraradices in a pot experiment. Plants were grown in a low P soil. Highly significant growth response of a Chenopodiaceae was recorded for the first time. Mycorrhizal colonization of roots was well developed, internal hyphae and vesicles were observed, but not arbuscules. These observations suggest that arbuscules are not necessary to obtain significant growth stimulation from mycorrhizal inoculation. Atriplex nummularia is already used as forage crops, its high mycorrhizal dependency offers possibilities to develop this production and revegetation strategies.

Depth matters : Effects of precipitation regime on soil microbial activity upon rewetting of a plant-soil system

2018

International audience; Climate change is predicted to affect not only the amount but also the temporal distribution of rain. Changes in frequency and amplitude of rain events, i.e. precipitation patterns, result in different water conditions with soil depth, and likely affect plant growth and shape plant and soil microbial activity. Here, we used 18O stable isotope probing (SIP) to investigate bacterial and fungal communities that actively grew or not upon rewetting, at three different depths in plant-soil mesocosms previously subjected to frequent or infrequent watering for 12 weeks (equal total water input). Phylogenetic marker genes for bacteria and fungi were sequenced after rewetting,…

Determinants of the distribution of nitrogen-cycling microbial communities at the landscape-scale

2010

Little information is available regarding the landscape-scale distribution of microbial communities and its environmental determinants. However, a landscape perspective is needed to understand the relative importance of local and regional factors and land management for the microbial communities. In this manuscript, we investigated the distribution of functional microbial communities involved in N-cycling and of the total bacterial and crenarchaeal communities over 107 sites using a grid with a 16 km lag distance within Burgundy, a 31 500 km2 region in France. After quantifying the abundances of the total bacterial, crenarchaeal, nitrate-reducing, denitrifying and ammonia-oxidizing communit…

Les phénols de la lignine et le 13C, traceurs de l'origine des matières organiques du sol

2001

Abstract In spodosols of Gascony (France), conversion of maritime pine stands into maize cropping leads to an incorporation of maize organic matter, which changed the isotopic (δ13C) and phenolic signature in A and L horizons of soil. Hydrolysis of phenol lignin in forests and cultivated soils showed the predominance of vanillic units under forest and the early but moderate incorporation of cinnamic acids. Incorporation of syringic units appeared higher, related to a large maize production of stable syringic phenols. Syringic units represented a long-term marker of maize inputs in soils, whereas vanillic units revealed the degradation of forest organic matter.

Holocene fire activity during low-natural flammability periods reveals scale-dependent cultural human-fire relationships in Europe

2018

Abstract Fire is a natural component of global biogeochemical cycles and closely related to changes in human land use. Whereas climate-fuel relationships seem to drive both global and subcontinental fire regimes, human-induced fires are prominent mainly on a local scale. Furthermore, the basic assumption that relates humans and fire regimes in terms of population densities, suggesting that few human-induced fires should occur in periods and areas of low population density, is currently debated. Here, we analyze human-fire relationships throughout the Holocene and discuss how and to what extent human-driven fires affected the landscape transformation in the Central European Lowlands (CEL). W…

Microbial Community Structure and Density Under Different Tree Species in an Acid Forest Soil (Morvan, France)

2005

Overexploitation of forests to increase wood production has led to the replacement of native forest by large areas of monospecific tree plantations. In the present study, the effects of different monospecific tree cover plantations on density and composition of the indigenous soil microbial community are described. The experimental site of "Breuil-Chenue" in the Morvan (France) was the site of a comparison of a similar mineral soil under Norway spruce (Picea abies), Douglas fir (Pseudotuga menziesii), oak (Quercus sessiflora), and native forest [mixed stand dominated by oak and beech (Fagus sylvatica)]. Sampling was performed during winter (February) at three depths (0-5, 5-10, and 10-15 cm…

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…

Actin in Allomyces arbuscula

1991

International audience; A 42 kDa protein was isolated by affinity chromatography on DNAse I-Sepharose from 24-h-old mycelia of Allomyces arbuscula. It was identified as actin by immunoblots with monoclonal antibody probe against a chicken gizzard actin. This fungal actin has a pI of 5.9 and separates into two spots on two-dimensional polyacrylamide gel electrophoresis, suggesting its dual nature. It can polymerize into 8-10 nm filaments visualized by electron microscopy.