284 research outputs found

    Species-Specific Effects of Epigeic Earthworms on Microbial Community Structure during First Stages of Decomposition of Organic Matter

    Get PDF
    Background: Epigeic earthworms are key organisms in organic matter decomposition because of the interactions they establish with microorganisms. The earthworm species and the quality and/or substrate availability are expected to be major factors influencing the outcome of these interactions. Here we tested whether and to what extent the epigeic earthworms Eisenia andrei, Eisenia fetida and Perionyx excavatus, widely used in vermicomposting, are capable of altering the microbiological properties of fresh organic matter in the short-term. We also questioned if the earthworm-induced modifications to the microbial communities are dependent on the type of substrate ingested. Methodology/Principal Findings: To address these questions we determined the microbial community structure (phospholipid fatty acid profiles) and microbial activity (basal respiration and microbial growth rates) of three types of animal manure (cow, horse and rabbit) that differed in microbial composition, after being processed by each species of earthworm for one month. No differences were found between earthworm-worked samples with regards to microbial community structure, irrespective of type of manure, which suggests the existence of a bottleneck effect of worm digestion on microbial populations of the original material consumed. Moreover, in mesocosms containing cow manure the presence of E. andrei resulted not only in a decrease in bacterial and fungal biomass, but also in a reduced bacterial growth rate and total microbial activity, while no such reduction was found with E. fetida and P. excavatus

    Analysis of the stress state of a halved and tabled traditional timber scarf joint with the Finite Element Method

    Get PDF
    The purpose of this study is to determine the stress distribution in the carpentry joint of halved and tabled scarf joint with the finite element method (FEM) and its comparison with the values obtained using the theory of Strength of Materials. The stress concentration areas where analyzed and the influence of mesh refinement was studied on the results in order to determine the mesh size that provides the stress values more consistent with the theory. In areas where stress concentration is lower, different mesh sizes show similar stress values. In areas where stress concentration occurs, the same values increase considerably with the refinement of the mesh. The results show a central symmetry of the isobar lines distribution where the centre of symmetry corresponds to the geometric centre of the joint. Comparison of normal stress levels obtained by the FEM and the classical theory shows small differences, except at points of stress concentration

    Relationship between peat formatíon and holocene environmental conditions in Sierra do Bocelo (NW Spain)

    Get PDF
    [Resumen] Se estudian las condiciones de formación y evolución de una serie de depósitos de turba de la Sierra de O Bocelo (A Coruña) y se relacionan con su morfología. La primera etapa formadora de turberas parte de finales del Atlántico, según han puesto de manifiesto las dataciones raciocarbónicas y las características polínicas de los perfiles estudiados; su origen se asocia con el incremento de precipitaciones de la época y con su situación topográfica. A principios del Subatlántico tuvo lugar una segunda fase de formación de turberas, que se relaciona con la degradación de las masas forestales por la acción del hombre y posiblemente con una degradación climática. El grado de descomposición de la wrba estimado por el sistema de Von Post refleja los distintos ciclos evolutivos de estas turberas.[Abstract] The conditions of the formation and evolution of a series of peats in Sierra do Bocelo (A Coruña, Spain) were studied and related to their morphology. Carbon dating and pollen characteristics show an initial peat-forming period beginning in the late Atlantic in topographically suitable areas due to increased rainfall. A second peat-formation period in the early Sub-Atlantic relates to increasing deforestation due to man, and possibly to worsening climate also. The successive cycles undergone by these peats are reflected by their degree of decomposition as measured on Von Post' s scale

    Polynic analysis of a periglaciar deposit in Moucide (Lugo)

    Get PDF
    [Resumen] Se realizó el análisis polínico de un depósito orgánico de características periglaciares en Moucide (Lugo) y de un nivel de turba cercano al anterior. Se efectuó la interpretación paleoecológica del mismo y su comparación con otros análisis realizados en la zona.[Abstract] It was made a polynic analysis of an organic deposit with periglaciar characteristics from Moucide (Lugo) and with a level of turf (sod-peat) near to the mentioned before. It was worked ont its paleoecologie interpretation and its comparison to the other analysis made in the place

    Annual variations of Castanea airbone pollen at thirteen spanish sites

    Get PDF

    AEROMICOTA DE AMBIENTES INTERNOS: COMPARACION DE METODOS DE MUESTREO

    Get PDF
    El procedimiento de muestreo utilizado paradeterminar el grado de contaminación fúngica enambientes internos, difiere según los autores. Por ello,con el fin de conocer si el método utilizado por nuestrogrupo de investigación, es comparable con otrasmetodologías, se ha realizado un estudio comparativocon varios sistemas de captación de esporas del aire,incluyendo equipos volumétricos (Aeroscope Chirana,System Air Sampler, Burkard Personal Culture) así comoel método tradicional por sedimentación. Los resultadosobtenidos muestran que apenas existen diferenciascuando se utilizan los sistemas volumétricos, sinembargo, el método por sedimentación ha sido menoseficaz, tanto desde el punto de vista cuantitativo comocualitativo. Mientras, el método directo por hisopado,resulta un buen complemento para determinar la fuentede contaminación. También se ha determinado la horadel día con mayor carga fúngica, que se localiza almediodía y tras el análisis de varios medios de cultivo,se concluye que el Agar Glucosa de Sabouraud resultaadecuado para este tipo de investigaciones

    Challenges to alcohol and other drug discussions in the general practice consultation

    Get PDF
    Background. There is a widely held expectation that GPs will routinely use opportunities to provide opportunistic screening and brief intervention for alcohol and other drug (AOD) abuse, a major cause of preventable death and morbidity

    Diversity, structure and sources of bacterial communities in earthworm cocoons.

    Get PDF
    Animals start interactions with the bacteria that will constitute their microbiomes at embryonic stage. After mating, earthworms produce cocoons externally which will be colonized with bacteria from their parents and the environment. Due to the key role bacterial symbionts play on earthworm fitness, it is important to study bacterial colonization during cocoon formation. Here we describe the cocoon microbiome of the earthworms Eisenia andrei and E. fetida, which included 275 and 176 bacterial species, respectively. They were dominated by three vertically-transmitted symbionts, Microbacteriaceae, Verminephrobacter and Ca. Nephrothrix, which accounted for 88% and 66% of the sequences respectively. Verminephrobacter and Ca. Nephrothrix showed a high rate of sequence variation, suggesting that they could be biparentally acquired during mating. The other bacterial species inhabiting the cocoons came from the bedding, where they accounted for a small fraction of the diversity (27% and 7% of bacterial species for E. andrei and E. fetida bedding). Hence, earthworm cocoon microbiome includes a large fraction of the vertically-transmitted symbionts and a minor fraction, but more diverse, horizontally and non-randomly acquired from the environment. These data suggest that horizontally-transmitted bacteria to cocoons may play an important role in the adaptation of earthworms to new environments or diets
    corecore