Search results for " Community"
showing 10 items of 1104 documents
Importance of dispersal and thermal environment for mycorrhizal communities: lessons from Yellowstone National Park
2011
International audience; The relative importance of dispersal and niche restrictions remains a controversial topic in community ecology, especially for microorganisms that are often assumed to be ubiquitous. We investigated the impact of these factors for the community assembly of the root-symbiont arbuscular mycorrhizal fungi (AMF) by sampling roots from geothermal and nonthermal grasslands in Yellowstone National Park (YNP), followed by sequencing and RFLP of AMF ribosomal DNA. With the exception of an apparent generalist RFLP type closely related to Glomus intraradices, a distance-based redundancy analysis indicated that the AMF community composition correlated with soil pH or pH-driven c…
Las redes sociales y la innovación educativa. La experiencia del Geoforo. Balance anual de 2012
2012
El aumento de la participación en los foros ha facilitado el intercambio de opiniones y argumentos sobre la innovación educativa. Podemos definir este momento como la creación de una red social con intereses profesionales coincidentes: la mejora del aprendizaje de los hechos sociales, en especial los que tienen una característica geográfica. Los datos que se aportan en este balance anual nos indican que se está asentando el Geoforo allí donde hay grupos locales, lo que nos confirma que este blog es una red de redes.
"Nerdfighters, we did it" : means of building a sense of community on the YouTube channel Vlogbrothers
2015
YouTube on tärkeä uusi ilmiö ja suosittu viihdekanava etenkin nuorten keskuudessa. YouTube-yhteisöjen suosiosta huolimatta ei niistä ole vielä tehty juurikaan tutkimusta, ja nettiyhteisöjen tutkimus onkin kohdistunut lähinnä tekstipohjaisiin yhteisöihin, kuten foorumeihin. Tutkielmani tarkoituksena on selvittää, kuinka YouTuben videobloggaajat rakentavat yhteisöllisyyden tunnetta faniensa keskuudessa. Tutkimuskohteenani on YouTube-kanava Vlogbrothers, jolla on yli kaksi miljoonaa vakituista katsojaa ja jonka ympärille on rakentunut poikkeuksellisen tiivis kansainvälinen katsojayhteisö. Videodataa analysoimalla pyrin erottamaan erilaisia keinoja, joilla vloggaajat vahvistavat yhteisöllisyyde…
Overlapping community detection versus ground-truth in AMAZON co-purchasing network
2015
International audience; Objective evaluation of community detection algorithms is a strategic issue. Indeed, we need to verify that the communities identified are actually the good ones. Moreover, it is necessary to compare results between two distinct algorithms to determine which is most effective. Classically, validations rely on clustering comparison measures or on quality metrics. Although, various traditional performance measures are used extensively. It appears very clearly that they cannot distinguish community structures with different topological properties. It is therefore necessary to propose an alternative methodology more sensitive to the community structure variations in orde…
Microsporidian disease of the invasive amphipod Dikerogammarus villosus and the potential for its transfer to local invertebrate fauna.
2012
12 pages; International audience; Invasive species may introduce novel pathogens to a colonised area. Most of the time emerging pathogens are detected a posteriori, but recognition of a priori emergence of an invasive disease by host shift may be useful for predictive purposes. Here, we studied if the microsporidian parasite Cucumispora dikerogammari infecting the invasive Ponto-Caspian amphipod Dikerogammarus villosus, has the potential to become an emergent disease in invaded rivers in Western and Central Europe. We first showed that this parasite decreases the survival of D. villosus in the later stages of infection development. However, the host reproduces earlier in response to the inf…
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,…
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…
Comparison of different tillage systems in organic farming : effect of soil structure and organic matter repartition on soil micro-organisms and thei…
2009
Over the last decades, the surface traditionally ploughed has tended to decrease and replaced by shallow working tillage techniques without soil inversion, i.e., no tillage or reduced tillage with tines or discs. These techniques were mostly developed in conventional farming systems but nowadays they are also developed in organic farming systems. Nevertheless, these tillage techniques could generate crop nutrients deficiencies and a deterioration of soil structure, especially during the first years of their application. As the use of synthetic fertilizers is forbidden in organic farming, a decrease of the soil fertility could be very detrimental for crop growth. Indeed, soil micro-organisms…
Caractérisation des communautés microbiennes dans les technosols construits pour la restauration des friches industrielles
2012
Increasing soil degradation and its consequences on overall ecosystem services urge for restoration strategies. Construction of Technosols through assemblage of treated soil and industrial wastes is an innovative technology for the restoration of polluted land and re-use of industrial by-products. Recent studies have evidenced that Technosols could support ecosystemic services such as primary production but the knowledge about other soil functions, such as biogeochemical cycling, is limited. Due to the significant contribution of microbial communities to soil functioning, this PhD work was carried out to study the effect of the type of Technosol on microbial communities with a focus on func…
SOIL MICROBIOLOGICAL QUALITY: STATE OF THE ART AND IMPORTANCE OF MICROBIAL COMMUNITIES FOR FRENCH AGRICULTURAL SOILS
2022
Soils are one of the major reservoirs of biological diversity on our planet, hosting a huge diversity of microorganisms. Numerous studies have demonstrated the role of microbial diversity in soil functions, such as nutrient cycling or pathogen management. Given the key role of soil microorganisms in the regulation of soil ecosystem functions, the environmental factors driving soil microbial diversity need to be understood. In France, we have the opportunity to benefit from a national soil survey (called the French Soil Quality Monitoring Network), which represents one of the most extensive and without a priori soil sampling survey available to date. Through several funded projects, we were …